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4D地震SEG杰出讲师课程Lecture 2

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Reservoir Engineering and Reservoir Management

“Engineers like to solve problems. If there are no problems handily available, they will create their own problems.” ― Scott Adams

Why Reservoir Engineering?
? Understanding the production process is critical to effectively apply 4D seismic methods ? Reservoir management strategy is dictated by the depletion mechanism ? Different depletion mechanisms result in different – Saturation distributions – Pressure variations – 4D seismic response ? 4D seismic is a reservoir engineering tool!

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 2

Outline
? Depletion Mechanisms – Natural Drives – Secondary Depletion – Enhanced Oil Recovery – Compaction ? Displacement Efficiency and Sweep ? Tools For Reservoir Management – Field Surveillance – Reservoir Simulation

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 3

Depletion Mechanisms
? Means by which hydrocarbons are produced from a reservoir to the surface ? Defined by available reservoir forces and energies – Natural energy: primary depletion – Supplemental energy: secondary depletion ? Multiple mechanisms may be active in any reservoir

Viscous

Gravity

Inertial

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 4

Depletion Mechanisms
? Natural Drive Mechanisms – Solution Gas Drive – Gas Cap Drive – Water Drive ? Secondary Depletion Mechanisms – Gas Injection – Water Injection ? Enhanced Oil Recovery – Miscible Flooding – Steam Flooding ? Compaction
2013 SEG Distinguished Instructor Short Course - Reservoir Management Slide 5

Solution Gas Drive
? Energy derived from expansion of free gas as pressure declines ? Characteristic reservoirs – Thin horizontal oil zones – Often associated with stratigraphic traps – No gas cap – No water drive ? Oil recovery < 30% OOIP

Oil

Gas

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 6

Solution Gas Drive 4D Applications
? Reservoirs typically pattern drilled ? Assumes pressure distribution is relatively uniform ? 4D response from gas coming out of solution ? Used to identify barriers, baffles, and isolated compartments
Fault High

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Pressure
Low
Slide 7

Gas Cap Drive
? Energy derived from expanding gas cap as pressure declines ? Ideal reservoirs – Large gas cap – Good gas cap and oil zone communication – Dipping structure, thick reservoir ? Oil recovery: 30 ~ 60% OOIP

Gas
Oil

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 8

Gas Cap Drive 4D Applications
? Wells completed below original OGC ? 4D response from gas cap expanding downward ? 4D used to – Identify gas channeling along high-permeability pathways toward wells – Identify untapped compartments

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 9

Water Drive
? Energy derived from external aquifer ? Ideal reservoirs – Relatively homogeneous – Large aquifer/reservoir volume ratio ? Oil recovery: 40 ~ 80% OOIP

Oil
Water

OOWC

Oil

Water

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 10

Water Drive 4D Applications
? Wells completed above original OWC ? 4D response from water displacing oil ? 4D used to – Identify channeling along high-permeability pathways toward wells – Locate bypassed oil

OOWC

OOWC

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 11

Depletion Mechanisms
? Natural Drive Mechanisms – Solution Gas Drive – Gas Cap Drive – Water Drive ? Secondary Depletion Mechanisms – Gas Injection – Water Injection ? Enhanced Oil Recovery – Miscible Flooding – Steam Flooding ? Compaction
2013 SEG Distinguished Instructor Short Course - Reservoir Management Slide 12

Gas Injection
? Why use gas injection? – Recover additional oil – Accelerate production – Maintain pressure – Prevent gas cap shrinkage – Reduce flaring ? Gas has high mobility ? 4D response from gas replacing oil or water – Minimize recycling – Determine sweep efficiency
Producer 2 Injector

Producer 1

West Africa Gas Injection

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 13

Waterflood
? Why use water floods? – Water is efficient in contacting and displacing oil to production wells – Water is generally available – Hydraulic head assists in injection ? Solution-gas-drive and weak water drive reservoirs are likely candidates ? Recovery about 50% OOIP

Water

Oil

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 14

Waterflood 4D Applications
? 4D response is from water replacing oil or gas – Track water fronts – Determine sweep efficiency – Locate bypassed oil – Prevent early water breakthrough – Identify thief zones, high permeability streak
Base S7 Time Surface C05 C18A Injector

2009 2006

C02

C06

N
RHW-Jurassic communication

Ringhorne Jurassic, North Sea

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 15

Depletion Mechanisms
? Natural Drive Mechanisms – Solution Gas Drive – Gas Cap Drive – Water Drive ? Secondary Depletion Mechanisms – Gas Injection – Water Injection ? Enhanced Oil Recovery – Miscible Flooding – Steam Flooding ? Compaction
2013 SEG Distinguished Instructor Short Course - Reservoir Management Slide 16

Miscible Flooding
? Miscible solvents swell oil oil, reduce viscosity, and increase mobility ? Solvents include natural gas and CO2 ? 4D responds to injected fluid and miscible front replacing oil or water ? Applications – Minimize recycling – Maximize sweep efficiency – Locate bypassed oil
Delhi Field, Louisiana 2010-2008 P-wave difference

Injector Producer

Richards (2011)

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 17

Thermal Flooding
? Reduce oil viscosity by increasing fluid temperature ? Cyclic stimulation, continuous flood, SAGD, and insitu combustion ? 4D responds to fluid and thermal changes – Monitor steam front and heated oil – Identify bypassed oil – Maximize program efficiency
Steam Oil with water

Oil

Steam

Hot oil and water

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 18

SAGD Flood Applications
1

2

3 4

5

6

7
8

9

October April 2010 2011

Surmont, Canada Conoco-Phillips and Total

Realistic reservoir – complicated flow Ideal reservoir – high recovery and OSR patterns and drainage of discrete packages
2013 SEG Distinguished Instructor Short Course - Reservoir Management Slide 19

Depletion Mechanisms
? Natural Drive Mechanisms – Solution Gas Drive – Gas Cap Drive – Water Drive ? Secondary Depletion Mechanisms – Gas Injection – Water Injection ? Enhanced Oil Recovery – Miscible Flooding – Steam Flooding ? Compaction
2013 SEG Distinguished Instructor Short Course - Reservoir Management Slide 20

Compaction Drive
? Nonreversible collapse of the rock framework and pore fluid expansion as pressure declines ? Common in highly compressible reservoirs – Unconsolidated sands Unstressed (e.g. California, Venezuela, and Alberta) – High porosity chalks (e.g. North Sea) After pore ? Early evaluation of compaction collapse critical for effective reservoir management
Wu et al. (1999)
2013 SEG Distinguished Instructor Short Course - Reservoir Management Slide 21

Compaction Drive 4D Applications
? Monitor inter-reservoir seismic changes resulting from porosity decrease in order to evaluate – Sand production potential – Compartmentalization ? Evaluate overburden and underburden strain changes – Determine wellbore integrity risk – Optimize well paths
Overburden changes

4D seismic over Gulf of Mexico tertiary unconsolidated reservoir

2013 SEG Distinguished Instructor Short Course Reservoir Management

Slide 22

Outline
? Depletion Mechanisms – Natural Drive – Secondary Depletion – Enhanced Oil Recovery ? Displacement Efficiency and Sweep ? Tools For Reservoir Management – Field Surveillance – Reservoir Simulation

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 23

Displacement and Sweep
? Depletion processes do not fully replace reservoir fluids ? Displacement efficiency – Fraction of depleted pore space – Defined by end-member saturations – Influences magnitude of 4D response ? Sweep efficiency – Fraction of depleted reservoir volume – Controlled by heterogeneities – Measured by 4D seismic

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 24

Displacement Efficiency

Swirr, Irreducible Water

Srow, Residual Oil Saturation to Water Oil

Grain

Water Sweep Original Oil

?Somax = 1 – Swirr – Srow Soinit
2013 SEG Distinguished Instructor Short Course - Reservoir Management Slide 25

Displacement Efficiency

Srog, Residual Oil Saturation to Gas

Original Oil Gas Swept

?Somax = 1 – Swirr – Srog Soinit
2013 SEG Distinguished Instructor Short Course - Reservoir Management Slide 26

Displacement Efficiency

Sgc, Critical Gas Saturation

Pressure Decline/Gas Original Oil Exsolution

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 27

Sweep Efficiency

OOWC Uniform areal sweep Water fingering to producer

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 28

Outline
? Depletion Mechanisms – Natural Drive – Secondary Depletion – Enhanced Oil Recovery ? Displacement Efficiency and Sweep ? Tools For Reservoir Management – Field Surveillance – Reservoir Simulation

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 29

Conventional Field Surveillance
? Pressure (well head and downhole) ? Production/Injection rates ? WOR, GOR ? Open-hole logs – Porosity and fluid saturation before and after production ? Cased-hole logs – e.g. Thermal decay time (TDT) – Repeat measurements of saturation ? Tracer - injected with water or gas and monitored at production well ? Production log (PLT) – Fluid flow rates – Fluid type
2013 SEG Distinguished Instructor Short Course - Reservoir Management Slide 30

Reservoir Simulation
? Integrates geological and production data ? Models sweep Data Sources ? Reservoir Description /Geologic Data ? Engineering Data ? Production Data
Prediction History

Major decisions ? Field development ? EOR techniques ? Reserves basis

Oil Rate

Oil Rate

Time

Time

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 31

History Matching
? Process by which model is adjusted to match field performance – Validates geological model, improves volume estimates – Develops predictive tool to estimate future field performance under various recovery schemes – Evaluates sensitivities to uncertain parameters ? Iterative process involving engineering and geoscience ? Non-unique -- good history match doesn’t guarantee predictability
50 4000

Oil rate (kSTBD)

Water cut (%)

40 30 20 10 0 1995

Field Model

3000 2000 1000 0 1995

Field Model

2000

2005

2010

2000

2005

2010
Slide 32

Time (years)
2013 SEG Distinguished Instructor Short Course - Reservoir Management

Time (years)

Reservoir Simulation
? Integrates geological and production data ? Models sweep Data Sources ? Reservoir Description /Geologic Data ? Engineering Data ? Production Data
Prediction History

Major decisions ? Field development ? EOR techniques ? Reserves basis

Oil Rate

Oil Rate

Time

Time

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 33

Reservoir Simulation
? Integrates geological and production data ? Models sweep Data Sources ? Reservoir Description /Geologic Data ? Engineering Data ? Production Data
Prediction History

4D Seismic Modeling and Interpretation ? Measures sweep
Predict

Oil Rate

Oil Rate

Time

Time

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 34

Reservoir Simulation
? Integrates geological and production data ? Models sweep Data Sources ? Reservoir Description /Geologic Data ? Engineering Data ? Production Data
Prediction History

4D Seismic Modeling and Interpretation ? Measures sweep
Predict

Oil Rate

Oil Rate

Time

Time

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 35

Summary
? Reservoir management strategy is dictated by the depletion mechanism ? Different depletion mechanisms result in different – Saturation distributions – Pressure variations – 4D seismic response ? Understanding the production process is critical to effectively apply 4D seismic methods ? Reservoir simulation can be used to predict 4D seismic ? 4D seismic can be used to update the simulation model

2013 SEG Distinguished Instructor Short Course - Reservoir Management

Slide 36




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