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7/28/2019 Depositional Sequences and Petroleum Systems (Meissner, 1997)
INDONESIAN PETROLEUM ASSOClATIONProceedings of the Petroleum Systems of SE Asia and Australasia Conference, M
THE ROLE OF DEPOSIT IONAL SEQUENCESIN CREA TING AND CONTROLL ING PETROLEUM SYSTEMS
-- BASIC PRINCIPLES AND EXA M PLES
Fmd F. Meissnefl
ABSTRACT
Most of the essential elements and processes thatcreate a petroleum system are controlled by thelithology and stratigraphy of the rrjck package
involved. The vertical and lateral distnbution ofsource, carrierheservoir, and migrational-barrierhap-seal rocks generally reflects an orderly pattern oflithoiogic and environmental facies that representsequences of transgressive-regressive or deepening-shallowing water sedimentation. In cross section, theseseuuences are commonly represented byunconformity-boundeC& wedge-shaped bodies of
sediment that thin from depositional basin centerstoward edges of non-deposition and erosion onbordering highlands.
An "ideal" depositional sequence contains an internaldistribution of source rock, carrier/reservoir, and sealunits. Overburden depths that cause source rockmaturity may be produced by the thickness ofoverlying beds within the sequence itself or in an
overlying sequence. Migration paths may be eitherupward and cross-stratal or lateral and updip within a
given carrierlreservoir unit. Migrahon may continueuntil either a site of entrapment is reached within areservoir indigenous to the sequence or a " leak" isencountered into an overlying sequence or to the
same lithologic geometries. Sequencof hydrocarbons due to source rocleakage. Understanding how requirpetroleum system are represedepositional sequence should aid i
predicting where oil and gas accumu
Examplesof petroleum systems relatsequences will be presented.
INTRODUCTION
The following elements areessentia
of a productive petroleum system: 1rock; 2) a reservoir rock; 3) a seI'trag". These elements must be plspace such that the processes of gene
accumulation andpreservation will tif not all, of the essential elementsprocesses that create a petrolecontrolled by the lithology and sttotal rock package involved. The drepresenting any oneof the essentiindependent of rock units of ddeposited in overlying, underlying o
occur in several orders of size and time duration,ranging from thick, long-term "1st order" cycles ofbasin formation, infill and stagnation, to thin short-term "2nd, 3rd, etc. order" cycles controlled bytectonic pulses or glacial eustasy (Figure 1).
Superposition of different orders leads to stratigraphiccomplexity and often generates lithologic patternsconducive to the formation of stratigraphic petroleumtraps. In cross section, sequences are commonly
represented by unconformity-bounded, wedge-shapedbodies of sediment that thin from maximum thicknessin depositional basin centers toward edges of non-deposition +d erosion on the flanks of borderinguplifts or platforms.
Oil-prone marine and lacustrine source rocks tend toform in depositional sequences during stages of
maximum transgressive flooding or in condensedsections where organic productivity ishigh and overallsedimentation rate controlled by inorganicsedimentation is low. Gas-prone humic source rockstend to form on coastal plains and nearshore swamps.Coarse-grained clastic reservoirs tend to form in high-energy shore line positions, in stream channels and in"Low-sea-level-stand turbidite deposits. Carbonatereservoirs tend to form in intertidal nearshorepositions and on open marine shelves and shelfmargins during periods of high sea level and shelfmargin progradation or in pinnacle reefs that growfrom low-stand shelves during sea level rise.Sealharrier rocks tend to form where shales andevaporites are deposited, as in deep water, shelf slopesand evaporite basins or on terrestrial flood plains,playas and sabkas. Two classes of depositional
sequences may be recognized: 1) marine or lacustrine(e.g., aquatic) cycles of transgressive-regressivesedimentation related to ocean/lake expansionfollowed by contraction and 2) terrestrial cycles ofregressive-transgressive sedimentation related tocontraction followedby expansionof oceansor lakes.
distribution of source rock, carrierfr
units (Figure 3). When source sequence reach a condition of thersource rocks will generate hydrocsubsequently be expelled to ounderlying canrierheservoir units. Orequired to achieve maturity may bethickness of overlying beds within torby an overlying younger sequencmay be upward and cross-stratal i
vertical migrational impedance, or thand updip within a given carrier/resean effective confining barrierheamay continue until either a site reached within a reservoir indigenouor a "lea"' occurs to an overlying searth's surface. Both stratigraphic trtraps may be present within a sequ
depositional compIexity and deformapresence of the sequence itself. configurations may also be supsequence after its deposition.
Not all sequences contain the stratthat make petroleum systems, norcritical lithologies inthe same archiEither source rocks, reservoirs or sein some sequences. Many sequencof hydrocarbons due to source rocoutward leakage. However, some thone or more essential element may sgeneration and leakage from anothe
Examples
Two examqles of "ideal" sedimrelated to major petroleum systemAmerican basins will be discused (
Several billion barrels of oil have Bone Spring-San Andres (Permian)
7/28/2019 Depositional Sequences and Petroleum Systems (Meissner, 1997)