Application of XRay CT to Investigate Effect of Rock Heterogeneity and Injection Rates During CO2 Flood Process

Application of X-Ray CT to
Investigate Effect of Rock
Heterogeneity and Injection
Rates During CO2 Flood
Process
Deepak Chakravarthy
Master’s Division
Texas A&M University

Feb, 2004


Topics of Discussion
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Introduction
Problem Outline
Objective
Experiment Outline
Results
Conclusions

Texas A&M University

Feb, 2004

Topics of Discussion







Introduction
Problem Outline
Objective
Experiment Outline
Results
Conclusions

Texas A&M University

Feb, 2004


Introduction
 Enhanced Oil Recovery
 CO2 flooding – One of the most widely used!

Why ?
Texas A&M University

Feb, 2004

Introduction
Broad Applicability

Lithology -- Works well in:
Sandstone (55% of current floods)
 Carbonates (35% of current floods)
 Others (about 10%)


Secondary or Tertiary
Oil saturation from <20% to 85% at start of
flood
 Average S for current flood is 55%
o
 Water cuts as high as 98% at start


Texas A&M University

Feb, 2004


Introduction
Mechanisms

 Miscible flood
 Extraction of light to intermediate hydrocarbons
 Oil swelling
 Viscosity reduction

Texas A&M University

Feb, 2004


Introduction
Miscible flood
Extraction of light to intermediate

Problems
?
hydrocarbons

Oil swelling
Viscosity reduction

Texas A&M University

Feb, 2004


Problem Outline
Limiting Factors

 Reservoir heterogeneity
 Low viscosity and high mobility
 Natural fractures

Texas A&M University

Feb, 2004


Objective
Investigate mechanisms of oil bypass during CO2
flooding

X-Ray CT Scanner
Texas A&M University

Feb, 2004


Topics of Discussion







Introduction
Problem Outline
Objective
Experiment Outline
Results
Conclusions

Texas A&M University

Feb, 2004


Experiment Outline
X-Ray Tomography
Workstation

3D CT Image

X-Ray Source
Digital Detector

Texas A&M University

Object

Feb, 2004


Experiment Outline
X-Ray CT Basics

 CT number
 Depends on density
 Every material has a characteristic CT number
 E.g. CT for air = -1000

Texas A&M University

Feb, 2004


CT Scanner

Texas A&M University

Feb, 2004


Experiment Outline
Procedure
Prepare Core

Experiment

Scan Dry Core

Saturate in
Vacuum Chamber

CO2 Saturated
Core Scans

Dope Oil

Texas A&M University

Feb, 2004

Experiment Outline

Texas A&M University

Feb, 2004


Experiment Outline
Experiment Summary

 Displaced Fluid - SoltrolTM Refined Oil
 Displacing Fluid - CO2
 Pressure - 800 psig
 Temperature - 75° F
 CO2 phase - Vapor

Texas A&M University

Feb, 2004


Experiment Outline
Experiment Summary

 Highest Injection Rate - 0.09 cc/min

Texas A&M University

Feb, 2004

Experiment Outline
Experiment Summary

 Highest Injection Rate - 0.09 cc/min
 Lowest Injection Rate - 0.03 cc/min

Texas A&M University

Feb, 2004


Experiment Outline
Experiment Summary

 Highest Injection Rate - 0.09 cc/min
 Lowest Injection Rate - 0.03 cc/min
 Lowest rate with heterogeneous (fractured) core
- 0.03 cc/min

Texas A&M University

Feb, 2004


Topics of Discussion








Introduction
Problem Outline
Objective
Experiment Outline
Results
Conclusions

Texas A&M University

Feb, 2004


Results

Dry core scans with bright blue regions
indicating higher CT numbers - i.e. higher
density


Results

Oil saturated core scans with red color
indicating higher CT numbers


Results

CO2 Injection at 15 minutes shows CO2 as a
blue spot at the center


Results

CT Scans at 25 minutes after start of
injection


Results

CT Scans at 35 minutes after start of
injection