U.S. GEOLOGICAL SURVEY PETROLEUM GEOLOGY OF THE …been regarded as dominated by wrench tectonics and associated vertical strike-slip faulting (e.g., Howell and others, 1980). However,

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

PETROLEUM GEOLOGY OF THE CENTRAL COASTAL BASINS ASSESSMENT PROVINCE, CALIFORNIA

FOR THE1987 NATIONAL ASSESSMENT OF

UNDISCOVERED OIL AND GAS RESOURCES

by

Caroline M. Isaacs1

Open-File Report 89-450 D

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

1U.S. Geological Survey345 Middlefield Road, MS 999Menlo Park, California 94025

1992

CONTENTS

Introduction...........................................................................^^^Province Location............................................................................................................................... 1Structural Setting................................................................................................................................ 1Stratigraphy..........................................................................................................................^Source rocks.............................................................^Burial history, thermal maturity, and timing of migration.........................................................21Hydrocarbon occurrence.................................................................................................................22

Geographic distribution..............................................................................................................22Stratigraphic and structural habitat of petroleum..................................................................23Basis for play definition........................................................................................................w^^

Neogene Play.....................................................................................................................................24Play defirn'tion....................................................Reservoirs.............................................................................................^^Traps and seals.............................................................................................................................24Oil characteristics..............................................._Depth of occurrence....................................................................................................................25Exploration status ........................................................................................................................37

History......................................................................................................................................37Future potential......................................................................................................................37

Acknowledgments...............................................^References .........................................................................................................................................44

Figures1. Index maps......................................................................................................................................4

A. Assessment province and play boundary .............................................................................4B. Isopachs of Tertiary sediment................................................................................................ 5C. Neogene basins of California margin (offshore) ................................................................6D. Major structural features........................................................................................................7

2. Interpretations of geologic history.............................................................................................. 8A. Terrane model for pre-Eocene California margin............................................................. 8B. Paleogeographic model of Eocene California margin....................................................... 9C. Plate tectonic model of Tertiary California margin......................................................... 10D. Evolution of Tertiary California margin (offshore)......................................................... 11

3. Cross-sectioris.........................................................................................................................^4. Stratigraphic columns and correlation charts......................................................................... 13

A. Pre-Neogene correlation chart............................................................................................ 13B. Map for pre-Neogene correlation chart............................................................................. 14C. Cuyama district Stratigraphic sections............................................................................... 15D. Salinas district Stratigraphic column................................................................................... 16E. Salinas district correlation chart.......................................................................................... 17F. La Honda district correlation chart..................................................................................... 18

CONTENTS - cont'd.

5. Neogene paleobathymetric histories........................................................................................ 19A. Cuyama district...................................................................................................................... 19B. Salinasdistrict.............................................................................................................^

6. Oil field maps...............................................................................................................................26A. Cuyama district ......................................................................................................................26B. Salinas district............................................................................................................^C. La Honda district...................................................................................................................28

7. Trap types .............................................................A. Structural trap, South Cuyama field...................................................................................29B. Structural trap, Russell Ranch field....................................................................................30C. Subthrust structural trap, Morales Canyon field ..............................................................31D. Combination trap, San Ardo field..................................................................................... 32E. Faulted anticlinal trap, King City field...............................................................................33F. Combination trap, Monroe Swell field...............................................................................34

8. Potential reservoir distribution, Salinas district......................................................................35A. Distribution of middle Miocene sandstone....................................................................... 35B. Distribution of upper Miocene sandstone .........................................................................36

Tables1. Field data for major fields (Nehring).......................................................................................392. Oil production and reserves for minor fields ..........................................................................403. Field data (California Division of Oil and Gas).....................................................................41

INTRODUCTION

This report presents a summary of the geology used as a basis for the U.S. Geological Survey's 1987 assessment of undiscovered oil and gas resources in the Central Coastal Basins assessment province. The petroleum geology was taken for the most part from published sources, principally Baldwin (1971) and California Division of Oil and Gas (1974).

The assessment was made on a base level of discovered oil and gas resources (cumulative production plus proved reserves) from the Nehring data base as of 12/31/83 (NRG Associates, 1984) which includes only fields exceeding 1 MMBOE (million barrels oil equivalent). These production and reserve figures correspond to those in California Division of Oil and Gas (1984) which includes fields of all sizes. Reserve additions due to field development or new discoveries declared after 12/31/83 by the California Division of Oil and Gas were for assessment purposes regarded as undiscovered resources.

Total baseline resources in the assessment province through 1983 were 884 MMBOE. These included cumulative production of 665 MMbbl (million barrels) oil and condensate and 343 Bcf (billion cubic feet) gas, for a province total of 722 MMBOE (California Division of Oil and Gas, 1984). Proved reserves totalled 161 MMbbl oil and condensate, and 7 Bcf gas, together representing 162 MMBOE (California Division of Oil and Gas, 1984).

PROVINCE LOCATION

The Central Coastal Basins assessment province is located in central coastal California. As defined (Figure 1A), the province is bounded on the south by the Big Pine fault, on the northeast by the San Andreas fault, and on the west (offshore) by the western limit of state waters within 3 miles of shore from Monterey (at the south) to San Francisco (at the north). The southwest boundary of the assessment province generally follows the Sur-Nacimiento fault but north of 36°N excludes the approximate extent of exposed pre- Cretaceous metamorphic basement rocks.

Geologically speaking, the assessment province includes the Neogene Cuyama, Salinas, and La Honda Basins (Figure IB), together with slivers of the Neogene outer Santa Cruz and Bodega Basins in the offshore (Figure 1C).

STRUCTURAL SETTING

The Central Coastal Basins assessment province is bounded by two major northwest- southeast trending faults, the San Andreas and Sur-Nacimiento faults, and includes the onshore portion of the Salinian block together with adjacent nearshore areas (Figure ID). Basement rocks in the Salinian block consist of Cretaceous granites and metamorphic r

rocks distinct from the basement rocks of adjacent structural blocks to the east and west (Figure 2A).

The onshore part of the assessment province generally consists of low-lying areas of Neogene and younger deposits (including the Neogene Cuyama, Salinas, and La Honda Basins), located more or less between northwest-southeast trending mountains of the Coast Ranges that expose pre-Neogene strata and basement rocks. The offshore part of the assessment province lies at a complex tectonic juncture of the San Gregorio-Hosgri and Sur-Nacimiento fault systems (Figure ID) near the edges of the Neogene outer Santa Cruz and Bodega Basins (Figure 1C).

Prevailing views of the formation of west coast Neogene basins are based on modifications of Atwater's (1970) and Atwater and Molnar's (1973) plate tectonic model for the west coast of North America. In this model, Neogene basins were formed at a triple junction (between the North American, Pacific, and Farallon Plates) that migrated north and south from the vicinity of southern California between 29 Ma and present (Figure 2C). Various summaries address the formation of basins within this setting (e.g. Blake and others, 1978; Howell and others, 1980), and a diagrammatic representation of the development of the central California margin is given in Figure 2D. Cross-sections of the assessment province are shown in Figure 3.

The Miocene and younger structural style of the assessment province has generally been regarded as dominated by wrench tectonics and associated vertical strike-slip faulting (e.g., Howell and others, 1980). However, compressional tectonics and associated thrust and high-angle reverse faulting were more recently advocated as the dominant structural style in the development of nearby offshore areas (Crouch and others, 1984). Subsequent to the assessment, major anticlinal structures in the Cuyama district and adjacent areas in the southern Coast Ranges and Transverse Ranges have been related to fault-bend and fault-propagation folds in a Pliocene and younger fold and thrust belt (Davis and Namson, 1987; Namson and Davis, 1990).

STRATIGRAPHY

The Central Coastal Basins assessment province is included in the Salinian composite terrane of Vedder and others (1983). Basement rocks in this terrane consist of Cretaceous or older granitic rocks and (locally) high temperature metamorphic rocks (Vedder and others, 1983, and references therein). The overlying Upper Cretaceous and lowermost Paleocene strata for the most part are sequences of clastic marine sedimentary rocks (Pigeon Point, Locatelli, Merle, Dip Creek, Asuncion, and Pattiway Formations together with various other including unnamed strata; see Figure 4A). These sequences are overlain throughout the assessment province by an unconformity representing most of Paleocene time (Figure 4A; Vedder and others, 1983). According to Vedder and others' (1983) terrane model, pre-Eocene strata were deposited far distant from the present California margin and sutured to the North American craton about 40 Ma (Figure 2A).

During the Eocene, a series of marine basins developed along the California continental borderland (Figure 2B; Nilsen and Clarke, 1975). Included within the assessment province are the Sierra Madre, Northern Santa Lucia, Point Lobos, La Honda, and Point San Pedro basins (or parts thereof; Figure 2B). Strata deposited in these basins were largely submarine fan deposits represented by thick marine sequences for the most part composed of sandstone, conglomerate, and mudstone (Matilija Sandstone, Juncal Formation, Church Creek Formation, Reliz Canyon Formation, Pinecate Formation, San Juan Bautista Formation, Butano Sandstone, and various other including unnamed strata; see Figure 4A). Locally, mudstone is also predominant as in the Cozy Dell Shale in the southeastern part of the assessment area (Figure 4A) and the Two Bar Shale and Rices Mudstone in La Honda district (Figure 4F). The Oligocene to early Miocene period in the La Honda basin is represented by a marine sequence generally deposited at bathyal or even abyssal depths (Stanley, 1984; Figure 4F).

In the Cuyama and Salinas districts, by contrast, Eocene deposits are unconformably overlain by nonmarine conglomerates and sandstones of probable late Oligocene or early Miocene age including the Simmler, Caliente, and Plush Ranch Formations (Figure 4A) and Berry Formation (Figures 4D and 4E). These strata mark the beginning about 20 Ma of Neogene basin formation (Figure 2C) represented by a major episode of basin subsidence and filling in the Salinas district (Graham, 1976; Figure 5B) and two such episodes in the Cuyama district (Lagoe, 1987a, 1987b; Figure 5A). Strata deposited during these episodes include shallow - and, in the Cuyama basin, partly bathyal - marine deposits of sandstone and mudrock (early Miocene Vaqueros Formation), overlain by mainly bathyal fine-grained calcareous and biosiliceous mudrocks (late early to late Miocene Monterey Formation), in turn locally overlain by bathyal to neritic sandstones and mudrocks (late Miocene Santa Margarita Formation). In the Cuyama district, the Monterey Formation is very localized, interfmgers with inner shelf marine sandstones of the Branch Canyon Sandstone, and is partly coeval with nonmarine strata of the Caliente Formation (Lagoe, 1984,1987; Figure 4C). In the Salinas district, the Monterey Formation is generally much thicker (max, 8600 ft; see Figure 4D) and more widespread, but locally interfingers with marine shelf sandstones of the Tierra Redonda and Santa Margarita Formations (Figures 4D, 4E, and 5B). Overlying Pliocene and younger nonmarine strata include the Qatal and Morales Formations in the Cuyama district, and the Paso Robles Formation in the Salinas district.

In the La Honda district, early Miocene strata included in the Vaqueros Formation are bathyal turbidite sandstones overlain by locally varying strata (including in places the Monterey Formation, Santa Cruz Mudstone, etc.) deposited in periods interrupted by several episodes of uplift and erosion during the Miocene (Figure 4F). A thick Pliocene mudrock (Purisima Formation) locally caps the Neogene stratigraphic sequence in this area.

Many studies describe the detailed stratigraphy and structure in the assessment province. For the Cuyama district, included are Carman (1964), Hill and others (1958), Vedder and Repenning (1965, 1975), Vedder (1968, 1970), Vedder and others (1973), Bohannon (1975), and Dibblee (1982). For the Salinas district are Durham (1963, 1964,

San Francisco

Assessment province boundary

Pacific OceanSANTA MARIA

. BASINAssessment _ _ VENTURA BASIN

Province Assessment

Santa Barbara

Figure 1A. Location of the Central Coastal Basins assessment province and Neogene play boundary.

Figure IB. Tertiary isopach maps. Reprinted from Baldwin (1971) by permission.

Half Moon Bay

int Ano Nuevo

36° -

35° -

124

Figure 1C. Generalized boundaries of late Tertiary shelf and slope basins and locations of offshore exploratory wells on the central California continental margin (from McCulloch, 1989).

Figure ID. Major structural features onshore (left; reprinted from Baldwin, 1971, by permission) and offshore (right; from McCulloch, 1987, 1989). On right diagram, teeth are shown on up-thrown side of high-angle reverse faults or upper plate of thrust faults, and shaded offshore areas are late Tertiary basins. Abbreviations for faults (near the assessment province) are: SAP - San Andreas, SF - Sur, NF - Nacimiento, SNF - Sur-Nacimiento, SGF - San Gregorio, HF - Hosgri, SLBF - Santa Lucia Bank, PF - Pilarcitos. Structural highs: SCH - Santa Cruz, FH - Farallon. Blocks: PPB - Pigeon Point, ANB-Ano Nuevo.

8

SUTURED TERRANES

SUR-OBISPO COMPOSITE TERRANE

SALINIAN COMPOSITE TERRANE

50

40

30

20

10

-10

-20

SID Fr*Dcitco

B

40 80 120 TIME (myBP)

160

Figure 2A. Pre-Eocene geologic history of the Santa Maria and Santa Barbara-Ventura basins. (A) Terranes of Southern California and northern Baja California showing the Santa Lucia-Orocopia allochthon (diagonal lines) and the Baja Borderland allochthon (stippled pattern). From Howell and others (1987). (B) Proposed latitude trajectories of the allochthons (and their constituent terranes) shown in A. From Howell and others (1987). (C) Generalized pre-Eocene stratigraphic column for the Salinian composite terrane, and the Sur-Obispo composite terrane (including the San Simeon terrane and the Stanley Mountain terrane). Modified slightly from Vedder and others (1983).

PACIFIC

OCEAN CARLOCK (PRESENT TRACE)

PACIFIC OCEAN

50 100 MILES

50 100 KILOMETRES

Figure 2B. Generalized paleogeographic map of early Tertiary California, restored for offset along the present San Andreas fault. City abbreviations: SAC-Sacramento; SF-San Francisco; BAK-Bakersfield; MON-Monterey; LA-Los Angeles; SD-San Diego. From Nilsen and Clarke (1975).

Figu

re 2

C.

Sche

mat

ic m

odel

of

inte

ract

ion

of P

acif

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aral

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and

Nor

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ates

for

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Ter

tiary

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tion,

and

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ape

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eoge

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orm

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from

Bla

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73).

ER

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; PA

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ega

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SC,

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OSC

, O

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M,

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MM

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ta M

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th

rltf

f*

fwtt

11

LE-0

TRANSPRESSION LP-H (5-3Ma)

TRANSTENSION M-P

TRANSTENSION O-M («v23Ma)

Figure 2D. Diagrammatic representation of the development of the offshore central California margin (from McCulloch, 1989). K, Cretaceous; E, Eocene; O, Oligocene; M, Miocene, P, Pliocene; H, Holocene.

12

Son GregorioFoult

SHORE Half Moon-J-irp

Son Andreos Fault

Boon Iconics

SANTA CRUZ MOUNTAINSzo.ooo1

w

Son Andrtos Fault

SW

SALINAS VALLEY

20,000*

ES- Oil Sand PC - Pliocene Continental P - Pliocini

Upper MioceneMiddle MiocimLewar MioceneMid. Mio (or lower)ContinentalFroncitconPre (?) Franciscan Marble

UM- M.M LM MC K|f

IS NE

Nocimicnta Foult

F F 1 (Section bfMk)

Voltey

Cuyomo Whiterock Morales Thrust) /Thrust iThrust

C«ll*nll Ml. C«rra«

Son Andr*os Foult

FigureS. Cross sections in the Central Coastal Basins assessment province. A-B across northern Santa Cruz Mountains. C-D across Salinas Valley. E-F-F'-G across Cuyama basin area. Locations of the sections are shown in Figure IB. Reprinted from Baldwin (1971) by permission.

13


TIME- ROCK UNITS

POINT RETES. POIN T SAN PEDRC. PIGEOK POINT, POU" LOB?'.

(Gallona;, 1977. ill et al.. 1977,

et al.. 19S9, INiM-Esfatia--, 19t5,

.tmon, 1978;

SANTA CRUZ MTNSSOUTMMfST Of SAK

ANDREAS FAULT

(Clarl and RletMn.1973. Green andClarl,. 1979, Cl*»-

ngs et al.. 1962,tonplon. 1966)

(Alien, 1946, Clart Rletaan, 1973,

and Schenck. I9?S, lloss. 1977)

13NORTHERN SANTA

LUCIA RANGE-INDIANSRANCH AREA

(GralMW, 1979, Ruetz. 1979. Ross, 1977)

LAKE NACIMIENTO

(Taliaferro, 1944; Durham, 1974, Novell »t !., 1977)

ISLA PAMZA RANGE, POZO SUMMIT TO

OWCIA MOUNTAIN

(Howl! et !., 1977, unpub. d*ta, 1980; Ross. 1977)

SOUTHEASTER* SItRRA NNNE MOUNTAINS

Madulce sjmcltne

Uedder. 1967. 1468; Vedder et <!.. 1973)

EASTERN CALIENTERMCt iocnncio

VALLEY

(C»HMn. 1*64; Mill 1., 19S8; tohtn-

non, 197S. Vtdoer nd Repemlnf. 197S)

HtSTtM SAN GAMICL MOUNTAINS

(Kooser, 1980, S*9«. 1975)

EVENTS

JFPOS FORMATION 900 r ss; nu-ine, 60

llo» bis«lt

ZAYANH SANDSTONE 550 r ss, sis, cs';

»AOUtRO$ FORMATION 400 P ss, Mrtne

UNNAMED RED BEDS 36S r breccit, cgl,

BUTANP SANDSTONE ?450; r ss, egl marine

PINECATE FORMATION 35 in ss, locil c;l,

urine

SAN JUAN BAUT ISTAFORMAT!OS

1525i m s», ill, urine

MAA/WNAACAWELO rORMA-JON,

>t. Reyes, ft. S«nPedro,400« m ss;c9',

»S.

LOCATEILI FORMATIO" r sis, SS,

y jrinj te

not 1n contact

PIGEO* PT rORMA'Il 330C if ss. sis, cgl,marine

not 1n contact

CHURCK CREEKFORMAT I OK

365: m ss, Ms, c

RELI2 CANYON FORMATION

VAOUEROS FORMATION740: is; wrine

SIMHLER FORMATION I8Si elji noiiMr-

VAOUCROS ronwiON230 * ss, subordin- <te cgl; ixrtne

CALIENTE FORMATION 100: ss; cgl. Ms; onurtne

VMMCROS FORMATION 71S: ss; Mrtne

CALIENTESIW.ER AND PLUSH RANCH FORMATIONS

900:, 91S. 1830: «.respectively.

»ASWCZ FORMAT IW 3800 m, egl. ss. suborittMte sis; noipurfne

II

UNNAMFD STRATA ItOO: ss, egl. Ms. Mrine

COZT DtlL'SHAL 36S Ms, subordin ate ss; Mrfne

WT1L1JA SANDSTONE 500: ss, lubordtn- te sis; Mrtne

JUNCAL FORMATION 7600; ss. Ms, oci! cgl; aartne

UNNAMED STRATA 670 sh. si; «*rtn«

MERLE FORMA^IOK 1S?5 r ss. Ms. Cll

DIP CREEK FORMATION IOC1 r ss. cgl. Ms;

UNNAMED STRATA 3400; * ss, Ms. cgl; Mrine

UNNAMED STRATA 0 n ss, cgl, Ms;

ASUNCION FORMATION ?300t ss. Ms, eg), *<rtne and non- inirinef)

base not exposed

PATTIUAT FORMATION 1070> m si. MS cgl; Mrtne

se not eiposed

SAN FRANCISOU1TOFORMATION

4000: I" SS, 09!, ds; Mrine

oclis, cMe'ly pe'utc scl'st and

(age uncertain)

netasediiiientar/ rocks, chie'lj Mr- ble, calc-nornfel s,

metasedimentar; rocks, quirtiofeUs- pathic gneiss, gri-v-

granttic rocks (age uncenam)

rnetasedlMntar; rocks; Mrble, schistose Inclusions 1fi granitic rtetii

granite east of Ozenj »iult (subsur face, age uncertain) Mesozoic and Precan-

brttn gnelsslc ilttc rocks

'»§*

Mesototc plutomcand Pr«caM>ritngneissic rocks

a«

Figure 4A. Pre-Neogene correlation chart illustrating known and inferred Stratigraphic and structural discontinuities in the Salinian composite terrane. Stratigraphic units, maximum or aggregated thicknesses, and predominant rock types are shown for localities 10-18 shown in Figure 4B. From Vedder and others (1983); not all references given are included in this report.

14

38

I23 C

50 100 KM

36'

121

[13)

36°-


I2I C

SUR-OBISPO COMPOSITE TERRANE 34<

Figure 4B. Location of stratigraphic columns in pre-Neogene correlation chart (Figure 4A). From Vedder and others (1983).

15

AiiOTT CANYON

PADRONES CANYON

' NONMAMINE NOCKS

' 'INNER SHELF SANDSTONE

kmI I OUTER SHELF SILTY SANDSTONE I I AND SILTSTONE

NW

WhiterockBluffShale

Santa Marganla Branch Canyon Undifferentiated

Saltos Shale

on

. ' Caliente

. Formation

Branch iTj^ Canyon ^<^Sandstone * -

Painted Rock Sandstone

Figure 4C. Summary Miocene stratigraphic section of southeast Caliente area (above); from Lagoe (1984) after Clifton (1981). Summary Neogene stratigraphic section beneath Cuyama Valley (below) from Lagoe (1984). For the pre-Neogene section in this area, see Figure 4A.

16

Cumulative maximum thickness, m feet

1000'

2000 -

3000 -

4000-

5000-

6000-

7000-

8000-

9000 -

10.000-

11.000-

12.000-

13.000-

14,000-

15.000-

16.000-

[QUATERNARY

| TERTIARY

PRE-TERTIARY

Recent

Pteisl

7

PIlO

|

Oligc

ocene

cene

*

icene

Eocene

Stratigraphic unit

AlluviumOlder alluvium

Paso Robtes Formation

Regionalunconformity(?)

Unnamed formation

Gradational

Monterey Shale

Gradational and

interfingenng contact

Vaqueros Formation

Reliz Canyon Formation

UNCONFORMITY

contact

Sandholdt

Gradationalcontact

Upper member

Interfingeringcontact

Lower member

Gradationalcontact

Upper member

Middle memberLower member

Basement complex

Generalized hthotogy

* 6 o o

0 ° o o -D 0 00

ocooVo".0

X X X X X

,,___",-

X X X X X

~\~^~

T. tTVTL

x~x"Vx5X X X^l-T.

TTOLxTx1. X.X.X.T.

X\ X X X.

xTx x"x"xX. X.X.X.X

X X V X X

x~x. x~x~x

L X V T.-Tx -u v x -vX X X. V X X X X 1- Xx x x"x?x

X~ X~T-~

x x Cx~x

r-J-i-^r

-------

00

0 0 <

0 0 « «

e o o <

-_-_-_-.

* y*'* K

*'"^' fs'*'

< XKXXX J

k>:xS:x *^ x ' v«'<

v * ^' N K

Sand and gravelSandy gravel and sandy silt

Conglomerate, rounded pebbles of porcelaneous rock and chert m matrix of fine to coarse sand and abun dant silt, generally calcareous;

Sandstone, yellowish-gray and very pale orange, poorly sorted, poorly bedded, generally calcareous;

Mudstone. very pale orange and yellowish-gray, massive.

Sandstone, very fine grained, yellowish-gray, massive, conchoidal fracture, ncncalcareous:

Sandstone, medium- to coarse-grained, yellowish- gray and yellowish-brown, mainly noncalcareous;

. Mudstone. sittstone. and claystone. yellowish-gray and / \ very pale orange, mainly noncalcareous: minor porce- / \ lamte and diatomrte. /

Porcelaneous mudstone and shate. chiefly light olive-gray and yellowish-gray, hackly fracture;

Porcelanite. pale yellowish-brown to white, hard, massive, fractured:

Mudstone and shale, chiefly very pale orange or yellowish- gray, massive to thin bedded, noncalcareous;

Carbonate beds and concretions, grayish-orange, pale yellowish-orange, and pale yellowish-brown, hard, dense.

Shale, chiefly very pale orange, light olive-gray, and gray ish-orange, hard calcareous:

Also contains porcelaneous shale, sittstone. sandstone, chert, and carbonate beds

Sandstone, arkosic. yellowish-gray, pale yellowish-brown, and pale-olive, fine- to coarse-grained, calcareous, fossiliferous:

Sfltstone. pale yellowish-brown, massive, hackly fracture.

Sandstone, arkosic. conglomeratic, yellowish-gray and grayish-orange, medium- to coarse-grained, locally cross-stratified, chiefly calcareous:

Local bads and lenses of conglomerate.

Sandstone, arkosic. yellowish-gray, light olive-gray, and pete-olive, medium- to coarse-grimed, chiefly calcare ous.

/Sittstone. kght olive-gray, mainly noncalcareous. hackly \ ' fracture, ellipsoidal calcareous concretions, fossilif-

erous

Sandstone, arkosic. kght olive-gray, fine- to coarse- \ grained, mainly noncalcareous. /

Schist, gneiss, hornblendite. crystalline limestone; cut by veins and dikes of quartz, aplrte, and pegmatite, and intruded by granodKXite.

Thickness

Approximate maximum m feet

60

1400

1000

6600

2000

2000

1100

1500

350

.180^

i 8

I

Near King City

Near mouth of Thompson Canyon

Northeast corner Reliz Canyon quadrangle

In subsurface in sec. 4, T. 20 S., R.7E.

In sec. 31. T. 19 S. R.6E

In sec 26. T.20 S.. R 6E

In sec 31. T20 S . R. 7 E,

In sec. 21. T. 20 S.. R.6E.

Near SW cor sec. y 21. T. 20 S.. R. 6E. ̂ do ^

Remarks

Base marked in most places by hard conglomerate with Opaline matrix. Nonma- nne.

Marine

Marine. Absent east of Salinas River. Contains sandstone in subsurface near margin of hills west of Salinas River.

Marine

Marine

Probably nonmarine

Probably marme

Marine

EXPLANATION

Siliceous shale Calcareous shale

Porcelaneous rocks Carbonate beds and concretions

JOOOOOOGJ |OOPOOPI

Conglomerate

Figure 4D. Stratigraphic column in the Reliz Canyon area. From Durham (1963).

17

WEST OF JOLON-RINCONADA FAULT ZONE EAST OF JOLON-RINCONADA FAULT ZONE

Paso Robles Formation (Pliocene and Pleistocene( ?))

Paso Robles Formation (Pliocene and Pleistocene!?))

Pancho Rico Formation (Pliocene)

Pancho Rico Formation (Pliocene) t (Overlies basement complex in northeastern part of map area).

Santa Margarita Formation (Miocene!

Buttle Member of Monterey Formation (Miocene)

Hamas Member of Montarey Formation (Miocene)Sandhokft Membai of Monterey Formation

<Miootrw)Tierra Radonda

Formation (Miocene

Vaqueros Formation (Miocene)

Santa Margarita Formation (Miocene)

Sandholdt Member of Monterey F Tierra Radonda Formation (Miocene)

Vaqueros Formation (Miocene)

Berry Formation (Oligocenei?))

'Buttle Member of Monterey Formation (Miocene)

Mames Member of Monteray Formation(M40CMW)

Unnamed formation (Cretaceous and Pateocene)

Reliz Canyon Formation (Eocene)

Basement complex (Pre-Tartiary)

SW SHELL LABARERE 27* 350 *

BEND IN Y SECTION

GENERALIZED LAND SURFACE SAN ARDO OIL FIELD

ENE ft PLEISTOCENE

ggPKllDOLE MIOCENE St. * COL (TMM. TMN)

SALINIAN BASEMENT

2000 4000 FT.

Figure 4E. Lateral relations (above) among formations in the southern Salinas Valley; from Durham (1974). Geologic cross-section (below) in the San Ardo oil field area; reprinted from Graham (1976) by permission (in part after Colvin, 1963).

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19

MIDDLE CENOZOIC SEQUENCE CUYAMA VALLEY, CALIFORNIA

MOR- ALES

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MONTEREY

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Figure 5A. Paleobathymetry of middle Cenozoic rocks beneath Cuyama Valley, showing two distinct episodes of basin subsidence and filling. Paleobathymetric abbreviations: NM-nonmarine; IN-inner neritic; ON-outer neritic; UB-upper bathyal; MB-upper middle bathyal; LB-lower middle bathyal. Reprinted from Lagoe (1987a).

20

TIME 5

GENERAL AGE STAGE FORMATION LITHOLOGY1

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PALEOBATHYMETRY1 (METERS)

SEDIMENTATION RATEA PALEOTECTONICS2

(METERS/M. YRS.) TIME

0 190t 3000 _____ , (FT7M.YRS.)

3000 8000 1 PtOTTED B¥ THICKNESS(FT.)_______2 PLOTTED BY ESTIMATED APE RANGE

Figure 5B. Tertiary paleobathymetry (above) in the Reliz Canyon area and middle Miocene paleogeography (below) in the Salinas basin. Modified slightly from Graham (1976) and reprinted by permission.

21

1965, 1966, 1968a, 1968b, 1970, 1974), Durham and Addicott (1964, 1965), Graham (1976, 1979a, 1979b), and Ruetz (1979). For the Santa Cruz Mountains or La Honda district are Alien (1946), Cummings and others (1962), Clark and Reitman (1973), Greene and Clark (1979), and Stanley (1984). For adjacent offshore areas are Hoskins and Griffiths (1971) and McCulloch (1987, 1989). A more complete bibliography for the southern part of the area is given by Heilbrunn-Tomson (1988).

SOURCE ROCKS

The Central Coastal Basins assessment province contains a variety of potential source rocks from Cretaceous to Pliocene in age. At the time of the assessment, little research was available except data on the Monterey Formation which was generally presumed to be the principal source rock in the two major petroleum-producing districts (Salinas and Cuyama).

The main source-rock study available was Kablanow (1986) who evaluated subsurface Monterey samples (mainly cuttings) from 8 wells in the central part of the Salinas Basin. Samples yielded TOC (total organic carbon) values in the range 0.8-5.5% (av 2.6%), with the organic matter generally type II or intermediate type II-III (as shown by elemental composition). Similar values of TOC (average lithotype values in the range 0.2-4.6%) and kerogen types were documented by Mertz (1984) for mainly surface samples from the lower part of the Monterey Formation (Sandholdt Member) in the area. A few samples of Eocene Juncal Formation in the mountains along the western boundary of the assessment province near the Cuyama district had TOC in the range 0.4-6.8% and type HI kerogens (interpreted from Rock-Eval pyrolysis) (Frizzell and Claypool, 1983).

Subsequent to the assessment, several source-rock studies were published or presented for the Cuyama basin. These generally concluded that the most probable major petroleum source in the Cuyama district is not the Monterey Formation but the early Miocene Soda Lake Shale Member of the Vaqueros Formation (Kornacki, 1988; Lillis, 1988; Lundell and Gordon, 1988), a unit sedimentologically similar to and more or less coeval with the Rincon Shale of the Ventura basin (Lagoe, 1987a).

BURIAL HISTORY, THERMAL MATURITY, AND TIMING OF MIGRATION

Because the major source rocks in the assessment province are Miocene in age, Neogene and especially late Neogene burial histories are of principal importance in evaluating oil generation and migration histories. Each district in the province has somewhat different characteristic burial histories. In the Cuyama district, the thickness of pre-upper Miocene Tertiary sediments in places exceeds 8000 ft (Figure IB) but younger strata were not rapidly deposited and are not today particularly thick, nowhere exceeding more than about 2000 ft (Figure IB). In the Salinas district, by contrast, upper Miocene and younger strata are as much as 8000 ft thick (Figure IB; Baldwin, 1971) and the

22

Monterey Formation as a whole in places exceeds 13,000 ft in thickness (Kablanow, 1986). In the Santa Cruz Mountain district, episodes of uplift and erosion occurred during parts of middle and late Miocene time (Stanley, 1984), and upper Miocene and younger strata exceed 4000 ft thickness mainly in the Half Moon Basin (Baldwin, 1971; Figure IB) which is filled for the most part with Pliocene sandstone and mudrocks of the Purisima Formation (Baldwin, 1971; Figure 3).

The only thermal maturation model available at the time of the assessment was Kablanow's (1986) study of the Monterey Formation in the central part of the Salinas basin. This study contains much valuable data on maturation of Monterey organic matter, including subsurface values for extractable hydrocarbon, some chromatographic parameters, and Rock-Eval pyrolysis corrected by extraction. (This latter correction adjusts for the heavy hydrocarbons and nitrogen-sulfur-oxygen compounds abundant in Monterey bitumen; see Kruge, 1983; Orr, 1983; Kablanow, 1986; Petersen and Hickey, 1987). By these criteria, mature (oil-generating) organic matter was considered to be present below 4500 ft (1.4 km) present-day depths in the center of the Salinas Trough (Kablanow, 1986).

Kablanow's (1986) study also addressed the history of oil generation and migration in the area. According to his model, in the lower part of the Monterey Formation in the central basin trough, sulfur-rich kerogen would have generated oil from about 8 to 6 Ma (in the temperature range 100-135 °C) with expulsion at 6000 ft of burial, and sulfur-poor kerogen would have generated oil from 5 Ma to the present (at temperatures exceeding 125 °C) with expulsion at 8000 ft. However, these conclusions are sensitive to many assumptions, for example assumptions regarding paleo heat flows (assumed to be high in the early Miocene, based on Hall's 1981 tectonic model of the Coast Ranges), thermal conductivity patterns in diatomaceous rocks (not well-known), present-day temperature gradients (not measured in equilibrium), etc. Other major unknowns were (1) whether the source kerogen is in fact sulfur-rich, sulfur-poor, or some combination; and (2) whether the heavy oils in the area are early-generated primary oils or biodegraded "normal" oils. (For a summary on early generation in the Monterey Formation, see Petersen and Hickey, 1987; Isaacs and Petersen, 1987.) Because of these uncertainties, models of the history of oil generation and migration were not considered sufficiently conclusive to be of particular value at the time of the assessment.

HYDROCARBON OCCURRENCE

Geographic Distribution

Discovered oil and gas resources (cumulative production plus proved reserves through 1983) in the assessment province total 884 MMBOE, including 826 MMbbl oil (93% of total province resources). Most resources are in the Salinas district with 545 MMBOE (62% of total province resources) and Cuyama district with 338 MMBOE oil (38% of total province resources), but most gas resources (»80% of province gas resources) are in the

23

Cuyama district. Additional resources of about 1.7 MMBOE oil («0.2% of total province resources) are located in the La Honda district.

Of total resources in the Salinas district, the vast majority (>99%) are in the Main area of the giant San Ardo field with remaining resources scattered among 9 other small fields or field areas (Tables 1-3). Resources in the Cuyama district are largely in the Main area of the South Cuyama field with 258 MMBOE (76% of the district total) and the Main area of the Russell Ranch field with 77 MMBOE (23% of the district total); another 3 MMbbl oil («1% of the district total) is scattered among 7 small fields and field areas (Tables 1-3).

Stratigraphic and structural habitat of petroleum

Most hydrocarbons in the Central Coastal Basins assessment province accumulated in permeable Miocene sandstones. In the Cuyama district, most oil is produced from shelfal marine sandstones of the Vaqueros Formation, principally the Dibblee sand of the Painted Rock Sandstone Member and the Colgrove sand of the Soda Lake Shale Member (Figure 4C; Table 3). Minor oil and gas are also produced from nonmarine sandstones in the Pliocene Morales Formation («1 MMbbl oil), the shelfal Miocene sandstones of the Branch Canyon Sandstone («1.5 MMbbl oil) and Santa Margarita Formation («2.5 MMbbl oil), and possibly the Soda Lake Shale Member of the Vaqueros Formation («1.4 MMbbl oil) (Table 3; Conservation Committee of California Oil and Gas Producers, 1986). Traps in the Cuyama district are mainly structural - complexly faulted anticlines, homoclines, and noses (Table 3; Figure 7A-7C). Some small traps are in subthrust structures sealed by overlying impermeable shale (Figure 7C).

In the Salinas district, the vast majority of oil is produced from the San Ardo field, where reservoirs are upper Miocene sandstones in the Monterey Formation (California Division of Oil and Gas, 1991) or Santa Margarita Formation (Durham, 1974) which intertongue with fine-grained rocks near the Miocene shoreline along the eastern edge of the Salinas Trough (Baldwin, 1971; Durham, 1974; Figure 4E). Several other smaller oil fields also produce from the "basinward shale edge" of upper Miocene Monterey-Santa Margarita sandstones, and one field (the King City field) produces from the "basinward shale edge" of middle Miocene Monterey-Tierra Redonda sandstones (Baldwin, 1971; Durham, 1974). Traps in the Salinas district are mainly Stratigraphic or combination stratigraphic-structural traps (Figures 7D-7F).

Basis for play definition

A variety of more or less stratigraphically defined plays were early considered for the Central Coastal basins assessment province. These included fractured reservoirs in the Monterey Formation (a speculative play); Miocene-Pliocene sandstones of the Monterey Formation together with subjacent and superjacent strata; sandstone reservoirs of the Vaqueros Formation (the main reservoir in Cuyama district, a speculative play for the Salinas district); nonmarine sandstones of the Simmler, Caliente and other Formations (a speculative play); Eocene sandstones of various formations (the main reservoir in the La

24

Honda district, a speculative play in other districts); Cretaceous sandstones and basement rocks (a speculative play); etc.

Because of the small number of fields (7 major fields as classed by the Nehring data base; see Table 1), however, and because reservoirs in all major discovered fields are Miocene-Pliocene sandstones, all fields in the assessment area were grouped together in a single play termed the Neogene play.

NEOCENE PLAY

Play Definition

The Neogene play is characterized by oil accumulations in Neogene sandstone reservoirs, trapped in structural, stratigraphic, and combination structural-stratigraphic traps. The play includes the entire area of significant subsurface extent of Neogene strata together with adjacent federal waters, an area approximately 275 miles long and 10-35 miles wide (Figure 1A).

Reservoirs

Throughout the assessment province, the major reservoir lithology is sandstone. In the Cuyama district, most oil is reservoired in sandstone of the Vaqueros Formation (Table 1) having porosity in the range 25-30% and permeabilities in the hundreds of millidarcies (NRG Associates, 1984). Even higher porosities (39-41%) are reported for the reservoirs of the San Ardo field in the Salinas district. Reservoirs in the La Honda district include a variety of sandstone horizons ranging from Eocene to Pliocene in age. According to Baldwin (1971), poor reservoir quality in this area is the major reason for its small cumulative production and overall resource potential.

Traps and seals

In the Cuyama district, traps are mostly structural. Two field areas account for most hydrocarbon resources: (1) the Main area of the South Cuyama field (the largest field in the district), where the trap is a faulted anticline (Figure 7A), and (2) the Main area of the Russell Ranch field, where the trap is a faulted homocline (Figure 7B). Traps in other smaller fields in the district are homoclines (Southeast area of the South Cuyama field and Cuyama Central field), faulted anticlinal noses (Southeast area of Russell Ranch field and Taylor Canyon field), and a faulted asymmetrical anticline (Morales Canyon field). Some traps (as in the Clayton area of the Morales Canyon field, Figure 7C) are in subthrust reservoirs. Throughout the area, the main seal is the fine-grained strata of the Monterey Formation.

In the Salinas district, the major trap (in the San Ardo field) is an anticlinal structure combined with intertonguing sandstones (reservoir) and shale (seal). Other smaller traps

25

in the district include permeability barriers on anticlinal folds (Monroe Swell field), lenticular sands on a dome (Doud 3-1-32 area of the King City field), and sand overlap onto basement (Me Cool Ranch field).

In the La Honda district, traps are mainly structural and include an anticlinal- homoclinal trap (Half Moon Bay field), nose (La Honda field), faulted nose (Oil Creek field), and a fold on the flank of a steeply inclined monocline (Moody Gulch field).

Oil Characteristics

Oil in the assessment province differs markedly between districts. In the Cuyama district, oil is generally light with API gravities in the range 26-46°. In the Salinas district, oil is generally heavy with API gravities in the range 10-19°; though included in the assessment as conventional oil resource, these heavy oils would by usual definition be classed as unconventional.

At the time of the assessment, no organic geochemical studies of the oils or oil-source correlation studies were published or otherwise available for the assessment province and the main source-rock was assumed to be the Monterey Formation throughout the area. Analogies with oil generation in the better-known Santa Maria, Ventura, and Los Angeles basins (Petersen and Hickey, 1984, 1987; Orr, 1986) suggested that the good-quality high- gravity oils of the Cuyama district were plausibly related to the clay-rich character of the Monterey Formation in that area (as speculated by Orr, 1986, for the Barham Ranch field in the Santa Maria basin). By similar analogy, the heavy oil characteristic of the Salinas basin was plausibly related either to biodegradation or to generation of primary heavy oil as in the Santa Maria basin (for a summary, see Isaacs and Petersen, 1987), but information was not available to distinguish between these possibilities.

Subsequent to the assessment, as mentioned above, studies suggested that oils in the Cuyama district derived from the Soda Lake Shale Member of the Vaqueros Formation (Kornacki, 1988; Lillis, 1988; Lundell and Gordon, 1988). The Soda Lake Shale Member is actually very similar lithologically to most strata included in the Monterey Formation in the Cuyama district, especially the Saltos Shale.

Depth of Occurrence

The depth to the top of oil reservoir horizons is moderate, being on average less than 6000 ft in all fields (as listed in the Nehring data base) with an average depth of about 3000 ft. Average reservoir thickness ranges from about 70 ft to about 600 ft, with an overall average of about 250 ft (by field; Table 1). Reservoirs in the Salinas basin are shallower (field averages 2000-2400 ft, Table 1; pool average 710-3200 ft, Table 3) than in the Cuyama basin, where the deepest average field depth (in the Cuyama Central field) is 7360 ft (Table 3).

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27

INDEX MAP A

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Figure 6B. Oil fields in the Salinas district. From California Division of Oil and Gas (1991).

28

MAP CNORTH CALIFORNIA

CALE IN MILES

Figure 6C. Oil fields in the La Honda district and adjacent areas. From California Division of Oil and Gas (1982).

TION R27W TION R26W

3O29

CONTOURS ON TOP OF DIBBLEE SAND

Figure 7A. Cross section and contour map of the Main area of the South Cuyama oil field (Cuyama district), showing the faulted anticlinal trap. From California Division of Oil and Gas (1991).

23

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Figure 7B. Cross section and contour map of the Main area of the Russell Ranch oil field (Cuyama district), showing the faulted homoclinal trap. From California Division of Oil and Gas (1991).

TUN R28W GOVERNMENT 18 AREA

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31

UNDIFF MARINE STRATA (CRETACEOUS)

Figure 1C. Cross section and contour map of the Morales Canyon oil field (Cuyama district), a faulted asymmetrical anticline. Note the reservoirs in deep subthrust positions. From California Division of Oil and Gas (1991).

32

CONTOURS ON TOP OF LOMBARD! OIL SAND OR EQUIVALENT

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Figure 7D. Cross section and contour map of the Main area of the San Ardo oil field (Salinas district), showing the anticlinal trap with stratigraphic variations. From California Division of Oil and Gas (1991).

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CONTOURS ON TOP Of DOUD SAND

34

Figure 7F. Cross section and contour map of the Monroe Swell oil field (Salinas district). The trap in this field is due to permeability barriers on the anticlinal fold. From California Division of Oil and Gas (1991).

35121 C 30' 121 00

30

Upper Reliz Canyon jSandholdtiUndh) j

\

Tierra Redonda Formation and Sand holdt Member ofMonterey Forma tion, undifferentiated

7"tm, out'crops(Ttm), approximate subsurface extent.

Includes sandy beds of the Tierra Redonda Formation where stippled

Rocks younger than the undifferentiated unit on rocks older than the unit

Outcrops of rocks older than the undifferentiated unit

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IsopachShowing estimated thickness of Tierra

Redonda Formation and Sandholdt Member ofMonterey Formation, un differentiated. Interval 1,000 feet

(g M 3248

Fossil locality Fauna listed in text

Mf1455

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Figure 8A, Distribution of the Tierra Redonda Formation and the lower part of the Monterey Formation (Sandholdt Member) undifferentiated. Stippled areas indicate sandy beds in the Tierra Redonda Formation. From Durham (1974).

36121"30'

121 00

EXPLANATION

Santa Margarita Formation and Buttle and Hames Members of Monterey Formation, undifferentiated

Tsm. outcrops(Tsm). approximate subsurface extent.

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Rocks younger than the undifferentiated unit on rocks older than the unit

Outcrops of rocks older than the undifferentiated unit

5000

IsopachsShow estimated thickness of Santa

Margarita Formation and Buttle and Hames Members of Monterey Formation, undifferentiated. In terval 1,000 feet

@M4072

Fossil locality Fauna listed in text

M4072

M3954 120° 30'

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Figure 8B. Distribution of the Santa Margarita Formation and the upper part of the Monterey Formation (Hames and Buttle Members) undifferentiated in the southern Salinas Valley. Stippled areas indicate sandy beds in the Santa Margarita Formation. From Durham (1974).

37

Exploration status

History

Earliest discoveries in the assessment province were in the La Honda district, where oil was discovered in the small Half Moon Bay field (with cumulative oil production through 1983 of 0.05 Mbbl) in about 1890 and in the Moody Gulch field (0.1 Mbbl) in 1898.

Further discoveries were not made until the late 1940s and early 1950s. In the Salinas district, these were (with cumulative oil production through 1983) the small North area (0.3 MMbbl) of the San Ardo field, 1947; the Main area of the San Ardo field (376.0 MMbbl), 1948; the Biaggi area (< 0.0005 MMbbl) of the Paris Valley field, 1948; and the Monroe Swell Field (0.2 MMbbl), 1949. In the Cuyama district, discoveries began with the Main area of Russell Ranch field (66.8 MMbbl) in 1948. All subsequent area and field discoveries in this district were made within 3 years: Main area of South Cuyama field (215.1 MMbbl), 1949; Clayton area of Morales Canyon field (1.0 MMbbl), 1950; Government 18 area of Morales Canyon field (1.4 MMbbl), 1950; Taylor Canyon field (0.5 MMbbl), 1950; Cuyama Central field (0.03 MMbbl), 1951; and Southeast area of South Cuyama field (0.1 MMbbl), 1951.

During the mid-late 1950s, minor discoveries were made in the La Honda district: Oil Creek field (0.2 MMbbl), 1955; Main area (0.8 MMbbl) of La Honda field, 1956; and South area (0.5 MMbbl) of La Honda field, 1959. Exploration in the Salinas district during the 1950's and 1960's also resulted in some small discoveries: Main area (0.1 MMbbl) of Paris Valley field, 1958; Doud area (1.8 MMbbl) of King City field, 1959; Kent-Basham area (0.1 MMbbl) of King City field, 1961; Lynch Canyon field (0.1 MMbbl), 1962; Quinado Canyon field (0.01 MMbbl), 1963; Doud 3-1-32 area of King City field (0.002 MMbbl), 1963; and McCool Ranch field (0.1 MMbbl), 1964.

During the 1970's and early 1980's, discoveries made in the Cuyama district were the East area of the South Cuyama field (1975) and a new gas pool in the Southeast area of South Cuyama field (1981). In the Salinas district was discovered the E sand pool in the McCool Ranch field (1981).

Future potential

Future resource potential in the assessment province seems likely to be fair to good, mainly in the less well-explored parts of the Salinas and Cuyama districts, with discovery of another giant field in the Salinas district the most promising possibility. Baldwin (1971) placed remaining potential new reserves at 2.5 Bbbl for the assessment province as a whole, 2 Bbbl for the Salinas district.

In terms of future potential, important features of the Salinas district include proven oil generation in significant quantities, a wide areal extent of thick subsurface sequences of Neogene sedimentary rocks likely to represent oil sources, and trap types (stratigraphic variations on slight structural highs) that are difficult to identify. However, future reserves would probably be difficult to find due to the difficulty of interpreting the complexities of

38

stratigraphy and structure concealing potential traps (Baldwin, 1971). Suggested exploration targets have included sandstone traps in the Vaqueros Formation on Miocene- Pliocene structures westward of the Neogene basin center (Baldwin, 1971) and the underexplored margins of basement highs where Miocene sandstones are present (Durham, 1974; Figures 8A, 8B). Fractured reservoirs or diagenetic traps within the Monterey Formation may also have future potential. A number of prospect wells were drilled during the 1980s, notably in the deep Hames Valley area with fractured-reservoir and diagenetic-trap potential, but results had not been announced at the time of the assessment.

In the Cuyama district, potential prospects seem most likely to be similar to existing fields but in deeper locations that have been difficult to identify, for example deep traps in concealed subthrust sandstone reservoirs. However, reservoir quality (sandstone permeability) may be a limiting factor in more deeply buried strata. Baldwin (1971) also suggested that uplifted areas northeast and southwest of the central overthrust graben were underexplored.

Future potential in the La Honda district seems generally poor and further drilling unlikely to produce significant new reserves, based on the long history of exploration resulting in only minor discoveries. Offshore prospects in the assessment province are likewise not highly promising, based on the paucity of discovered resources in adjacent onshore areas.

ACKNOWLEDGMENTS

Many people contributed knowledge and counsel on the geology of the assessment province. I particularly thank William Bazeley formerly of Arco Oil and Gas Corporation (Bakersfield, California); Margaret Keller, Larry Beyer, Kenneth Bird, Rick Stanley, and Jack Vedder - all with the U.S. Geological Survey (Menlo Park, California); Dave Griggs and the late Frank Webster, both formerly with the Minerals Management Service (Los Angeles, California); Neil F. Petersen of Worldwide Geosciences (Houston, Texas); Ray Kablanow formerly with the University of Wyoming (Laramie, Wyoming); and Cathy Rigsby formerly of Sohio (San Francisco, California), now of Long Beach State University (Long Beach, California). For permission to reprint figures, I acknowledge and thank the American Association of Petroleum Geologists; Stephan A. Graham of Stanford University (Stanford, California); Martin B. Lagoe of the University of Texas (Austin, Texas); and Richard G. Stanley now of the U.S. Geological Survey (Menlo Park, California). Lynn Tennyson of the U.S. Geological Survey (Denver, Colorado) and Kenneth J. Bird reviewed preliminary versions of this report.

Tabl

e 1.

Oil

field

dat

a fo

r the

Cen

tral C

oast

al B

asin

s as

sess

men

t pro

vinc

e, b

ased

on

Neh

ring

data

bas

e th

roug

h 19

83 (N

RG

Ass

ocia

tes,

198

4).

BA

SIN

Fiel

dTr

ap ty

peFo

rmat

ion

Aver

age

Dep

th to

to

p (ft

)

Aver

age

Thic

knes

s (ft

)

Aver

age

API

Gra

vity

Dis

c'y

Year

Cum

ulat

ive

prod

'n +

res

erve

sO

il (M

Mbb

l)N

GL

(MM

bbl)

Gas

(B

cf)

CU

YA

MA

BA

SIN

Sout

h C

uyam

a -

Mai

n ar

eaM

oral

es C

anyo

n -

Cla

yton

are

aM

oral

es C

anyo

n -

Gov

nt 1

8 ar

eaR

usse

ll R

anch

- M

ain

area

Rus

sell

Ran

ch - S

outh

east

are

a

Stru

ctur

alS

truct

ural

Com

bina

tion

Stru

ctur

alS

truct

ural

Vaqu

eros

Mor

ales

Vaqu

eros

Vaqu

eros

Vaqu

eros

3600

1900

5800

2800

3600

520

100

400

600 70

33 31 38 37 39

1949

1950

1950

1948

1952

220.

01.

01.

467

.3 0.7

9.9 - -

2.0

0.1

215.

60

.5 1.3

46

.8 3.1

SA

LIN

AS

BA

SIN

San

Ardo

King

City

- D

oud

area

Com

bina

tion

Stru

ctur

al

Lom

bard

yM

onte

rey

Mon

tere

y

2000

2400

2000

150

120

100

11 13 16

1947

1959

525.

0

2.0

- -

71.4 0.1

AV

ER

AG

E30

1325

827

1951

TO

TA

L11

781

72 12

48 339

Tabl

e 2.

C

umul

ativ

e pr

oduc

tion

+ re

serv

es in

sm

all f

ield

s no

t inc

lude

d in

the

Neh

ring

data

bas

e (N

RG

Ass

ocia

tes,

198

4).

Bas

ed o

n C

alifo

rnia

Div

isio

n of

O

il an

d G

as (

1984

,198

6),

see

also

Tab

le 3

.

BA

SIN

Fie

ldC

umul

ativ

e pr

oduc

tion

+ re

serv

esO

il (M

Mbb

l)G

as

(Bcf

)

CU

YA

MA

BA

SIN

Tayl

or C

anyo

nS

outh

Cuy

ama

- S

outh

east

are

aS

outh

Cuy

ama

- Ea

st a

rea

(abd

)C

uyam

a -

Cen

tral a

rea

(abd

)

0.49

0.11

0.04

0.03

0.14

0.93

0.03

0.01

SA

UN

AS

BA

SIN

McC

ool R

anch

San

Ard

o -

Nor

th a

rea

Mon

roe

Sw

ell

Par

ris V

alle

yLy

nch

Can

yon

Kin

g C

ity - K

ent-B

asha

m a

rea

Qui

nado

Can

yon

Kin

g C

ity - D

oud

3-1

-32

area

0.35

0.31

0.27

0.14

*

0.12

0.11

0.01

0.00

2

<0.

001 -

0.00

3<

0.00

1<

0.00

1<

0.00

10.

003 -

LA H

ON

DA

BA

SIN

La H

onda

- M

ain

area

La H

onda

- S

outh

are

aO

il C

reek

Moo

dy G

ulch

(ab

d)H

alf M

oon

Bay

0.80

0.52

0.19

0.10

0.05

0.11

0.04

0.08

0.04

0.02

[TO

TA

L3.

639

1.40

6

Res

erve

s no

t inc

lude

d.

Tabl

e 3.

O

il fie

ld d

ata

for C

entra

l Coa

stal

Bas

ins

asse

ssm

ent p

rovi

nce

(from

Cal

iforn

ia D

ivis

ion

of O

il an

d G

as,

1974

,198

4).

BA

SIN F

IELD AR

EA

Poo

l

Poo

l D

isc'

y D

ate

Cum

ulat

ive

prod

uctio

nO

il (M

Mbb

l)G

as

(Bcf

)

Trap

Typ

eA

vera

ge

Res

ervo

ir D

epth

(ft

)

Ave

rage

R

eser

voir

Thic

knes

s (ft

)

Pool

AP

I gr

avity

CU

YA

MA

BA

SIN

SO

UT

H C

UY

AM

AM

AIN

AR

EA

52-1

Gas

(San

ta M

arga

rD

ibbl

ee (

Vaq

uero

s)C

olgr

ove

(Vaq

uero

s)S

OU

TH

EA

ST

AR

EA

Col

grov

e (V

aque

ros)

RU

SS

ELL

RA

NC

HM

AIN

AR

EA

San

ta M

arga

rita

Dib

blee

(Vaq

uero

s)G

riggs

-Dib

blee

(Vaq

uer

Col

grov

e (V

aque

ros)

SO

UT

HE

AS

T A

RE

AD

ibbl

ee (

Vaq

uero

s)M

OR

ALE

S C

AN

YO

NC

LAY

TO

N A

RE

A (

abd)

Cla

yton

(Mor

ales

)G

OV

ER

NM

EN

T 1

8 A

RE

AG

over

nmen

t 18

(Vaq

uer

TA

YLO

R C

AN

YO

NQ

uail

Can

yon

sand

(Vaq

CU

YA

MA

CE

NT

RA

LB

ranc

h C

anyo

n

1953

1949

1950

1951

1948

1948

1949

1949

1952

1950

1950

1950

1951

215.

1

0.1

66.8

66.1 0.6

2.4

1.0

221.

2

0.03

46.9

43.8 3.1

1.8

0.5

1.4

0.5

0.03

1.3

0.1

0.01

Faul

ted

antic

line

Faul

ted

hom

oclin

e

Faul

ted

hom

oclin

e

Faul

ted

antic

linal

nos

e

Faul

ted

asym

met

rical

ant

iclin

e

Faul

ted

nose

Faul

ted

hom

oclin

e

1830

3600

4300

5840

2500

2800

4300

3500

3600

1900

5800

5620

7360

3540

012

0 50

200

350

150

100

70 100

400

200 20

26 33 33 37 25 34 3835-4

0 39 31 38 38 46

BA

SIN F

IELD AR

EA

Poo

l

Poo

l D

isc'

y D

ate

Cum

ulat

ive

prod

uctio

nO

il (M

Mbb

l)G

as

(Bcf

)

Tra

p Ty

peA

vera

ge

Res

ervo

ir D

epth

(ft

)

Ave

rage

R

eser

voir

Thic

knes

s (ft

)

Poo

l A

PI

grav

ity

SA

UN

AS

BA

SIN

SA

N A

RD

OM

AIN

AR

EA

Lom

bard

! (M

onte

rey)

Aur

igna

c (M

onte

rey)

NO

RT

H A

RE

ALo

mba

rd! (

Mon

tere

y)K

ING

CIT

YD

OU

D A

RE

ATh

orup

(M

onte

rey)

DO

UD

3-1

-3

2 A

RE

AT

horu

p (M

onte

rey)

KE

NT

-BA

SH

AM

AR

EA

Thor

up (

Mon

tere

y)M

cCO

OL

RA

NC

HLo

mba

rd!

(Mon

tere

y)M

ON

RO

E S

WE

LL44

(M

onte

rey)

Dou

d (M

onte

rey)

Bee

dy (

Mon

tere

y)P

AR

IS V

ALL

EY

BIA

GG

I A

RE

AB

asal

Ans

berr

y (M

onte

reM

AIN

AR

EA

Bas

al A

nsbe

rry

(Mon

tere

LYN

CH

CA

NY

ON

Lani

gan

(Mon

tere

y)Q

UIN

AD

O C

AN

YO

NG

ambo

a-K

elly

(Mon

tere

1948

1948

1947

1959

1963

1961

1964

1960

1959

1949

1948

1958

1962

1963

376.

037

5.7

0.31 1.

91.

8

0.00

2

0.11

0.13

0.24

0.13

<0.0

005

0.13

0.13

0.01

71.4

71.4

0.06

0.06

<0.

001

<0.

001

<0.

001

0.00

3

<0.

001

<0.

001

0.00

3

Ant

iclin

e

Faul

ted

dom

e

San

d le

ns o

n a

dom

e

Faul

ted

nose

San

ds o

verla

p on

to b

asem

ent

Per

mea

bilit

y ba

rrie

rs o

nan

ticlin

al fo

ld

Ant

iclin

e

Faul

ted

antic

line

Dom

e on

bas

emen

t hig

h

Faul

ted

nose

2000

2400

2100

2000

1860

2450

2150

2000

2900

3200

1090 710

1800

2035

150

120

40 100 30 65 30 200

200

150 70 80 55 60

11 13 10 16 13 17 12 19 19 17 13 12 10 19

BA

SIN F

IELD AR

EA

Poo

l

Pool

D

isc'

y D

ate

Cum

ulat

ive

prod

uctio

nO

il (M

Mbb

l)G

as

(Bcf

)

Trap

Typ

eA

vera

ge

Res

ervo

ir D

epth

(ft

)

Ave

rage

R

eser

voir

Thic

knes

s (ft

)

Pool

AP

I gr

avity

LA H

ON

DA

BA

SIN

LA H

ON

DA

MA

IN A

RE

AU

pper

Cos

ta (B

utan

o)Lo

wer

Cos

ta (B

utan

o)S

OU

TH

AR

EA

Bur

nsO

IL C

RE

EK

Tony

(But

ano)

Cos

ta (B

utan

o)M

OO

DY

GU

LCH

(ab

d)Sa

n Lo

renz

oH

ALF

MO

ON

BA

Y (

abd)

Pur

isim

a

1956

1959

1955

1898

C8

18

90

1.3

0.79

0.50

0.18

0.10

0.05

0.15

0.11

0.04

0.08

0.04

0.02

Ant

iclin

e

Nos

e (?

)

Faul

ted

nose

Fold

on

flank

of s

teep

ly in

clin

edm

onoc

line

Ant

iclin

e an

d ho

moc

line,

acc

umul

ain

upd

ip le

nses

.

1660

1800

1400

1860

2090 80

0[io

n80

0

45 30

60-1

80 55 120 40

40 40 17 41 41 45 45

44

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45

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46

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U.S. GEOLOGICAL SURVEY PETROLEUM GEOLOGY OF THE …been regarded as dominated by wrench tectonics and associated vertical strike-slip faulting (e.g., Howell and others, 1980). However,

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