Reserves Addition From Low Gravity Crudes-dr Amaefule Spe Lagos Section Final-june 2009

BY DR JUDE O. AMAEFULE

CHAIRMAN/CEO EMERALD ENERGY RESOURCES LIMITED

Presented at the Distinguished Lectures and Technical Meeting of the Lagos Nigeria Chapter of the Society of Petroleum Engineers, SPE International

On June 30, 2009 at the Federal Palace Hotel, Victoria Island, lagos

•  Business Case

•  Definition of Low Gravity Viscous Oils

•  Characteristics of Low Gravity Crudes

•  Global Distribution of Heavy Oil Reservoirs

•  Typical Niger Delta Fields with Low Gravity Viscous Oils

•  Overview of Current Heavy Oil Developments

•  Production Challenges

•  Productivity Enhancement Strategies

•  Technological Advances for Heavy Oil Developments

•  Concluding Remarks

DEFINITION OF LOW GRAVITY VISCOUS OIL

CHARACTERISTICS

PROPERTIES

NATURE

Oil Classification by API Gravity

Published correlations were used, most of which rely on the oil’s API gravity as their basis. One (arbitrary) classification system for crude oil is by De Ghetto et al, (1994).

1) Extra-heavy crude oil – APIo < 10 2) Heavy crude oil – 10 < APIo < 22.3 3) Medium crude oil – 22.3 < APIo < 31.1 4) Light crude oil – APIo > 31.1

Definitions •  LOW GRAVITY VISCUOUS OILS ARE

FLUIDS WITH CONSIDERABLY LOW API GRAVITY & CORRESPONDINGLY HIGH VISCOSITY. THEY ARE COMMONLY REFFERRED TO AS HEAVY OILS.

•  VISCOUS OILS ARE HUGE PRODUCTION NIGHTMARES.

•  IT’S IMPORTANT TO REMEMBER THAT WHAT WORKS FOR ONE HEAVY-OIL FIELD MAY NOT WORK AT ALL IN THE NEXT.

Characteristics of Low Gravity Oil Sands

•  SANDS ARE GENERALLY UNCEMENTED WITH HIGH POROSITY AND PERMEABILITY

•  OILS RANGE IN GRAVITY FROM 8 TO 20 API

•  VISCOSITIES RANGE FROM A FEW HUNDRED TO MORE THAN ONE MILLION CP

•  RESERVOIRS ARE TYPICALLY SHALLOW, AT LOW PRESSURE AND TEMPERATURE

•  SOLUTION GAS CONTENT IS LOW

Global Distributions of Heavy Oil Resources

UNITED STATES- CALIFORNIA & ALASKA

CANADA-ALBERTA , WESTERN CANADA

VENEZUELA-ORINOCO BASIN, MARACAIBO

RUSSIA-VOLGA-URAL

INDONESIA- DURI

BRASIL

MEDITERRANEAN , OFFSHORE ITALY, -

TRINIDAD

CHINA

NORTH SEA (UK & NORWAY)

MIDDLE EAST-IRAN & IRAQ, OMAN

AFRICA (MADAGASCAR, NIGERIA)

Like natural gas, heavy oil becomes what the industry calls a “stranded resource” when it is discovered far from infrastructure to transport and refine it.

4,000 4,000

5,000 5,000

6,000 6,000

7,000 7,000

8,000

9,000 9,000

10,000 10,000

11,000 11,000

C4.0 C4.0 C4.0

D4.0 D4.0 D4.0

D9.0

E2.0 E2.0 E2.0

E4.0 E4.0

E6.0 E6.0

E8.0 E8.0

F1.0 F1.0

Undegraded Oil

Meteoric Water

Connate Water

Degraded Oil

WELL 45 WELL 10 WELL 28

Cross section of Imo River Field showing faults and location of reservoirs(C4.0, D4.0, etc)

D1.0

8,000

LEGEND BIODEGRADED & VISCOUS ZONE

UNDEGRADED ZONES

Reference: Relationship Among Oils and Water Composition in Niger Delta. By P.A. Dickey, G.O. George & C. Barker (AAPG: 1987))

GEOCHEMICAL FINGERPRINT OF OILS SHOWS

VARYING DEGRESS OF BIODEGRADATION

OVERVIEW OF CURRENT HEAVY OIL DEVELOPMENTS

•  COLD PRODUCTION (FOAMY OIL/SAND PRODUCTION) •  CYCLIC STEAM STIMULATION (CSS) WITH OIL TO STEAM

RATIOS (2-3) Typically Called “Huff & Puff” •  STEAM FLOODING •  HORIZONTAL WELL STEAM FLOODING •  INSITU COMBUSTION •  STEAM ASSISTED GRAVITY DRAINAGE •  MULTI-LATERAL HORIZONTAL WELLS •  GAS INJECTION •  WAG (WATER ALTERING GAS)   CHEMICALS

•  SOLVENTS •  SURFACTANTS •  ALKALINE

•  Heavy oil can be produced in limited amounts by “cold” production, with typical recovery factors in the range of 5% to 8%.

•  The most common way to produce heavy oil is to heat the reservoir, usually by injecting steam, which typically boosts recovery rates as well over 20%, and in some cases as high as 70%.

•  Operators in California use steam-drives the way others might use water. Rows of up to 10 steam generators, each the size of a diesel locomotive, are a common sight.

•  The trick with this and any thermal recovery process is to minimize the steam-oil ratio (SOR), since steam is the largest single expense. Even a small shift in the SOR can have a significant impact on a field’s overall economics.

CHARACTERISTICS OF RESERVOIRS SUITABLE FOR STEAMFLOOD RECOVERY

PARAMETERS STEAMFLOOD

DEPTH, FT 160-5000

NET PAY, FT 10-1,050

DIP, DEG. 0-70

POROSITY, % 12-39

PERMEABILITY, md 70-10,000

OIL GRAVITY, OAPI 5-40

OIL VISCOSITY AT INSITU TEMPERATURE, cp

4-106

OIL SATURATION @ START, % 15-85

OOIP AT START, BBL/ACRE-FT 370-2,230

•  HOT WATER FLOOD INCLUDING VISCOSITY REDUCTION & SWELLING

•  GAS DRIVE

•  STEAM DISTILLATION

•  SOLVENT EXTRACTION EFFECTS

•  LOW FLOW RATES RESULTING FROM HIGH VISCOSITY

•  WATER BREAK- THROUGH (Adverse Mobility Ratio)

•  PREMATURE GAS BREAK THROUGH •  SAND PRODUCTION •  LOW RECOVERY EFFICIENCIES (3-5% STOIIP)

•  ARTIFICIAL LIFTING OF HEAVY CRUDES FROM HIGHLY DEVIATED WELLS

•  TREATING HEAVY CRUDES WITHIN THE CONFINED SPACE OF AN OFFSHORE PLATFORM

•  PIPELINE TRANSPORTATION OF THE CRUDE TO SHORE THROUGH THE COLD OCEAN ENVIRONMENT

•  SYSTEM STARTUPS OR RESTARTS AFTER A SHUTDOWN

•  EMULSIONS (W/O & O/W) FORMATION

•  CRUDE OIL FOAMING •  ORGANIC SCALING

( ASPHALTENES & WAX) PRECIPITATION AND ESP FOULING

•  STEAM DISTRIBUTION •  SANDING •  WATER AND GAS CONING •  FINES MIGRATION •  HYDRATE FORMATION •  SWEET AND SOUR GAS

CORROSION •  FORMATION DAMAGE

REF:SPE 16606

•  HORIZONTAL WELLS •  MULTILATERAL HORIZONTAL WELLS •  PROGRESSIVE CAVITY PUMPS FOR

ARTIFICIAL LIFT •  FOAMY OIL/SAND PRODUCTION

•  CYCLIC STEAM STIMULATION

•  MULTIPHASE BOOSTER PUMPS

THESE INCLUDE:

•  Developed with Vertical wells •  Developed with H wells •  Require Larger Completion length through

application of multi-lateral well(MLW) technology or very closely spaced H wells.

•  Low PI of Viscous Reservoir means that wells may not flow under test without Artificial lift.

Ideally, the PIF for a non-damaged horizontal well varies from 3 to about 5 for well lengths in excess of 1000 feet. The benefits of an undamaged horizontal well include the significant

reserves addition and the savings in operating expenses. However, Formation damage could decrease the PIF to about 1.5.

DEVELOPMENT SCENARIOS •  Target 10 KBOPD

– Δp = 250 psi – For Vertical Wells, the ff is required;

Koh/µo > 50,000 md-ft/cp – For H wells

KO h/µo> 5000 md-ft/cp

•  PIHWELL/PIVERTICAL ≈ 10

ADVANTAGES OF HORIZONTAL WELLS IN PRIMARY HEAVY OIL PRODUCTION

•  LOWER UTC

•  LONG (1000-1500 FEET) HORIZONTAL

WELLS CAN BE DRILLED FOR 3 TO 4

TIMES THE COST OF A VERTICAL

WELL BUT THE INCREASED

EXPOSURE TO THE RESERVOIR CAN

YIELD 10 TIMES THE PRODUCTION

RATE, THEREBY REDUCING UTC

•  ABILITY TO EFFECTIVELY PRODUCE

RESERVOIRS WITH BOTTOM WATER

•  ENLARGED DRAINAGE VOLUME

•  REDUCED IMPACT OF

HETEROGENEITIES

•  REDUCED PRESSURE DRAWDOWN

•  LOWER ECONOMIC PRODUCTION

RATE ALL CONTRIBUTE TO HIGHER

ULTIMATE RECOVERY

•  Hwell Completion Minimizes – Pressure Drawdown – Maximizes Stand-off from O/W contact

thereby achieving higher PI vs Vertical •  High K makes the onset of water coning

one of the key criteria in well design •  Sand Control measures required due to

unconsolidated nature during completion •  Pre-packed screens for sand exclusion

CASE HISTORY: VENEZUELA Horizontal Wells in Melones Heavy Oil FD

Geology

•  Sand bed dip

•  Fault locations

•  Horizontal well length (increased LD; increased with PI)

•  Geological and reservoir analysis results have been applied in actual drilling programs to improve production performance

Design of horizontal wells:

•  Length of horizontal lateral

•  Reservoir heterogeneity •  Sand thickness and

structure •  Reservoir pressure •  Drainage area •  Crude viscosity

CASE HISTORY: VENEZUELA Horizontal Wells in Melones Heavy Oil FD

Le = LD - ΣLS ⇒ Le * h ⇒ 95,000 ft2 → PI =

9.4 STB/D/PSI

•  PI (max) = 9.4 STB/D/PSI (Le * h→ 95000) •  Qh = 1700 STB/D (horizontal well) •  Qv = 200 STB/D (vertical well)

DRILLING WAS NOT A PROBLEM AS HOLE STABILITY AND SAND PRODUCTION WAS ABOUT 1 MILLIGRAM/LITER OF FLUID

HORIZONTAL WELLS ARE COMPLETED WITH SLOTTED LINERS B/W 0.012 & 0.018 – THIS ALLOWS THE USE OF ESP IN WELLS WITH PI’S OF MORE THAN 3.0 STB/D/PSI

MULTILATERAL WELLS ENHANCE PRODUCTIVITY OF VISCOUS OIL RESERVOIRS

DESIGN CONSIDERATIONS FOR A HEAVY OIL MULTILATERAL WELL

•  Simulation studies to: •  Investigate interaction B/W well branch

inflow & completion pressure drops – Well trajectory – Completion diameter – Positioning of artificial lift for heavy oil

multilateral

Requirements: •  Better reservoir description to both

understand well performance and to improve well placement

•  Type of liner •  How best to cleanup the well

Multi-lateral wells add an additional level of complexity in that well branch interaction need to be taken into account :

•  Branch inflow performance

•  Completion performance between the sandface and well junction points

DESIGN CONSIDERATIONS FOR A HEAVY OIL MULTILATERAL WELL

MULTILATERAL HORIZONTAL WELLS

PROS & CONS OF MULTI-LATERAL HORIZONTAL WELLS IN PRIMARY HEAVY OIL PRODUCTION

PROS •  HIGHER PI

•  INCREASED RESERVES PER WELL DUE TO INCREASED DRAINAGE VOLUME AND BETTER VERTICAL AND AREAL SWEEP

•  DRAINING RELATIVELY THIN LAYERS

•  DECREASED WATER & GAS CONING

•  BETTER SWEEP EFFICIENCY

•  EOR BY STEAM-ASSISTED GRAVITY DRAINAGE

CONS •  HIGHER INITIAL COSTS •  INCREASED SENSITIVITY TO HETEROGENEITIES

AND ANISOTROPIES (STRESS & PERMEABILITY) •  SENSITIVITY TO POOR EEFECTIVE VERTICAL

PERMEABILITY •  COMPLICATED DRILLING, COMPLETION AND

PRODUCTION TECHNOLOGIES •  COMPLICATED AND EXPENSIVE STIMULATION •  SLOWER AND LESS EFFECTIVE CLEANUP

•  CUMBERSOME WELLBORE MANAGEMENT DURING PRODUCTION

•  DIFFICULT SELECTION OF APPROPRIATE CANDIDATES

•  INTERFERENCE OF WELL BRANCHES

•  CROSSFLOW & DIFFICULT PRODUCTION ALLOCATION

•  DIFFICULTY OF DAMAGE REMOVAL

•  ELECTRICAL SUBMERSIBLE PUMPS (ESP)

•  JET PUMPS

•  ROD PUMPS

•  GAS LIFT

ARTIFICIAL LIFT OPTIONS

REF: R. KIRVELIS and D.R.DAVIES, IChemE, 2003

PROS & CONS OF VARIOUS LIFT OPTIONS

LIFT

OPTIONS

PROS CONS

ESP • MOST USED OFFSHORE • CAPABLE OF LIFTING HIGH VOLUMES • EASE OF INSTALLATION IN DIRECTIONALLY DRILLED HOLES • NEW VARIABLE SPEED CONTROLLERS AND CABLE SUSPENDED PUMPS LIMIT DISADVANTAGES

• LACK OF PRODUCTION-RATE FLEXIBILITY • HIGH FAILURE RATES • NEED TO USE DRILLING OR WORKOVER UNITS TO REPLACE THE PUMP

JET PUMPS

• USED SUCCESSFULLY FOR DST OF HEAVY CRUDE ZONES IN EXPLORATORY WELLS · USES WATER AS MOTIVE POWER FLUID

ROD

PUMPING UNITS

• SPACE REQUIREMENTS OFFSHORE • ROD FLOATING • CRUDE PLUGGING • OVERLOADED PUMPING UNITS • STICKING & SAND EROSION

GAS LIFT SUCCESSFULLY USED ON PLATFORM A IN THE HONDO FIELD OFFSHORE CALIFORNIA IN WELLS WITH API GRAVITY OF 17API

USED INFREQUENTLY FOR LIFTING HEAVY CRUDES DUE TO LOW GOR AND LACK OF AVAILABLE GAS

OTHER NEW PRODUCTION TECHNOLOGIES METHOD SUITABILITY

CHOPS: Cold Heavy Oil Production with Sand

• Good for unconsolidated sandstones • 5-20m zone thickness • No mobile water, no water legs • RF: 12-20 %

SAGD: Steam Assisted Gravity Drainage

• Limited to thicker zones (>20m) • Good for immobile heavy oils • Combined processes of gravity segregation and shale thermal fracturing make SAGD very efficient with RF up to 50%

PPT: Pressure-Pulse flow enhancement Technology

• Useful with other methods (Cold flow, CHOPS)

VAPEX: Vapor Assisted Petroleum Extraction

• Best in >20°API cases or as a SAGD adjunct

THAI: Toe-to-Heel Air Injection

• Applicable to all Heavy Oils

REF:M.B. DUSSEAULT, CIPC, PAPER 2001-061

•  Like natural gas, heavy oil becomes what the industry calls a “stranded resource” when it is discovered far from the infrastructure to transport and refine it.

•  Today for example, there is the capacity to produce at least 2 million barrels of heavy oil per day from the middle east, but there is no market for it.

•  Steam-assisted gravity drainage (SAGD) is growing in importance as thermal recovery method for heavy oil. Operators outside Canada have begun to investigate this process to obtain the highest possible recovery rates from heavy oil fields.

CURRENT HEAVY OIL DEVELOPMENTS CONTD’.

SAGD

Toe-Heel Air Injection(THAI) IN-SITU COMBUSTION PROCESS

MIXED-MODE DEVELOPMENT SCHEMES

•  Using a solvent instead of steam to reduce heavy oil viscosity offers economical and environmental advantages and may be applicable to some reservoirs where SAGD is not applicable.

•  Commonly, the heat is applied by hot fluids 2 utilizing steam injection or hot oil treatments. While these methods can be extremely effective in many applications, both are subject to certain limitations.

•  Both steam and hot oil experience heat losses which lead to considerable lowering of the fluid temperature before it reaches the well bottom.

United States Patent 4330037

WATER FLOODING AS A RECOVERY TECHNIQUE FOR LOW GRAVITY OIL RESERVOIRS

•  Critical water and gas rates to be determined

•  Adverse mobility ratio leads to early water breakthrough, thus poor sweep efficiency and recovery of a large portion of the reserves at high WC.

•  Full Voidage Replacement, by injecting water into aquifer to be implemented right from the outset to maintain pressure and enhance the lift capability of the producing well.

 Questions?  Discussions?  Comments?