Pilot Project Management for Gas Displacement Recovery (GDR) Flooding

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PRAXAIR BUSINESS CONFIDENTIAL

GDR Pilots For Reserve Growth •

Key is Proper Planning – –

•

Determine goals, objectives, and strategy Goals: book reserves, test reservoir model data aquired

Important Tasks Include: 1) Initial reservoir characterization 

2) 3) 4) 5)

Identifying reserve growth method

Design monitoring program Design facilities Proper implementation Postmortem evaluation

Step 1: Reservoir Characterization Work Flow

Start

Feed back Loop

Determine Reservoir Architecture

Establish Fluid-Flow Trends

Develop a Reservoir Model

Identify Reserve Growth Potential

How does the pilot design test the reservoir Model?

Reservoir Architecture Issues For EOR Pilots • Depositional Stacking Patterns – Flooding surfaces acting as flow barriers – Grain size and diagenesis causing high k variation

• Horizontal facies changes between injectorsproducers – Spatial facies variations cause anisotropic k

• Sealing and/or Offsetting Faults – Flow barriers – Interflow unit connectivity

Reserve Growth Applications 1. Pressure Maintenance  

Oil reservoirs Pressure maintenance condensate and retrograde condensate reservoirs

2. Miscible Displacement 3. Immiscible Displacement  

Oil: IWAG Gas cap gas

4. Mixed Gas Applications  

Driving agent for slug/buffer Mixed gases for density control

5. Gas Assisted Gravity Drainage

Step 2: Monitoring Program • Goal; To gather data to allow the evaluation of the pre injection prediction • Collect Fluid Input and Output Data, – Volumes, rates – Downhole Injection and production profiles

• Monitor Reservoir Conditions – Temperature and pressure

• Measure Hydrocarbon Saturation Change – Downhole wireline saturation logs – Volumetric recovery efficiency

Considerations for Monitoring Wells • Number of Monitoring Wells – Single well, vertical and displacement efficiency – Multiple wells, vertical sweep between wells, areal sweep efficiency, fluid mobility within the formation

• Location of Monitoring Wells – Test geologic interpretation

• Well Logistics – – – –

Drilling Coring, logging Completing Integrating data gathering

Injection Well Design Example from Bay St. Elaine Field

Screen wells for completion issues (Palmer et al., 1984)

Mobile Downhole Monitoring Unit

Monitor for the effect of injection on Oil Saturation: Example Oil saturation (%) 0 -12,790

20

40

Post Inj. Well A-18 Pre Inj. Well A-17

SubSea depth (ft)

-12,800

Residual oil saturation to water influx Minimum = 0.154 Maximum = 0.376 Average = 0.221

Residual oil saturation to CO2 Minimum = 0.0 Maximum = 0.073 Average = 0.022

-12,810

-12,820

-12,830

-12,840

-12,850

-12,860

Apply through casing saturation tools •Reservoir Saturation Tool (RST) •Resistivity •Neutron

Step 3: Facilities Design • SAFETY FIRST • Site Preparation • Injection Facilities – Solvent delivery – Pumping equipment

• Production Facilities – Fluid rate and volume measurement – Fluid separation – Fluid handling

Facilities Design: Site Preparation • Pad Preparation – Size, layout, material

• Road Construction and/or Repair • Power Needs – Pumps, lights, trailers

• Water Needs

Facilities Design: Gas Delivery • Solvent Supply and Demand Status – Can you obtain the needed CO2 volumes when you want them?

• Diesel Source and