This study focuses on methods to reduce the permeability of water bearing formations by injecting chemical solutions through the wellbore. Permeability reduction applies in increasing recovery from waterfloods, water-drive gas reservoirs, and might find application in other fields, like environmental engineering, hydrogeology and construction. Different permeability reduction mechanisms are investigated and recommendations are given to aid in selecting an appropriate permeability reduction mechanism for a given reservoir. The study is conducted through literature search, theoretical and experimental investigations[1].

After examining several permeability reduction methods, it was found that no single technique can be applied universally in all reservoirs. The most common factor affecting the success and applicability of all the methods mentioned above is temperature, fluid salinity and pH. Some methods also depend on shear rate and consequently to rock properties as well as flow rate. The result of this study is a table that according to reservoir temperature, fluid salinity and pH, suggests the most efficient method to reduce permeability in a water bearing formation. Although this table does not provide a final answer to all possible situations, it is a staring point to design the appropriate permeability reduction treatment for a particular formation.

The general conclusions of this study are:

  • No single technique can be applied universally in all reservoirs to deliberately reduce permeability in a considerable radius around a well.

  • It is possible to create a reduced permeability zone around a well. This barrier can prevent water encroachment if reservoir conditions permit.

  • The conditions that effect the performance of most permeability reduction methods, are; temperature, rock properties, pH and salinity. The effects of temperature, pH and salinity are shown in Table 1 for all methods considered to be efficient for the purpose of the present study.

  • Some of the methods considered in this study also depend on displacement velocity. The iron hydroxide sol and gels based on polyacrylamide polymers are effected by displacement velocities the most. In both of these cases, it is more efficient to deliver the corresponding fluids at low rather than high displacement velocities.

  • Employing fine migration/clay interaction is not applicable because permeability reduction is not evident at low flow rates.

  • A method based on iron hydroxide colloidal solution (sol) is proposed for low temperature, low salinity reservoirs. From our experimental work it is shown that the magnitude and distribution of permeability reduction caused by iron hydroxide sol injection are injection rate dependent.

  • Acidization with hydrofluoric acid causes conductivity reduction in fractured carbonates. However, it is not certain if conductivity reduction is continuous along the fractures.

  • From the other methods considered in the present study, microbial treatments and in-situ gelation show a stronger potential for application.

Table 1

Classification of Permeability Reduction Methods

MethodTemperaturepHSalinityMajor Influences
Iron Hydroxide Sol Low Low Low Chlorides, High Rates 
Microbial Treatment Low Medium Low  
Xanthan Gum/Cr(VI) Low Medium Medium Hydrogen Sulfide 
Xanthan Gum/Cr(III) Low Low Medium  
Aluminum Citrate Low Medium Medium  
PHPA/Cr(VI) Medium Low Medium Iron Cations, High Rates 
Silicates Low Medium Medium Calcium Chloride 
PHPA/Cr(III) Medium Low Medium High Rates 
Aluminates Medium Medium Medium  
Lignosulhonates Medium Medium Medium  
Polysaccharides High High High Calcium., Magnesium 
Phenophormaldehyde High Medium Medium  
MethodTemperaturepHSalinityMajor Influences
Iron Hydroxide Sol Low Low Low Chlorides, High Rates 
Microbial Treatment Low Medium Low  
Xanthan Gum/Cr(VI) Low Medium Medium Hydrogen Sulfide 
Xanthan Gum/Cr(III) Low Low Medium  
Aluminum Citrate Low Medium Medium  
PHPA/Cr(VI) Medium Low Medium Iron Cations, High Rates 
Silicates Low Medium Medium Calcium Chloride 
PHPA/Cr(III) Medium Low Medium High Rates 
Aluminates Medium Medium Medium  
Lignosulhonates Medium Medium Medium  
Polysaccharides High High High Calcium., Magnesium 
Phenophormaldehyde High Medium Medium  
RANGES Degrees Fahrenheit pH Total Solids ppm 
HIGH 60-160 2-5 0-20,000 
MEDIUM 160-200 5-8 20,000-50,000 
LOW 200-300 8-12 50,000-150,000 
RANGES Degrees Fahrenheit pH Total Solids ppm 
HIGH 60-160 2-5 0-20,000 
MEDIUM 160-200 5-8 20,000-50,000 
LOW 200-300 8-12 50,000-150,000 

Following the above conclusions and anticipating field application of permeability reduction methods, it is recommended that:

  1. Most favorable reservoir candidates for such treatments are the ones with low temperature and low salinity resident water.

  2. Since the radius around a well affected by such methods is not expected to exceed 500 ft, well spacing needs to be considered when creating a permeability barrier.

  3. A very important design factor is the time required for the injected fluids to reduce formation permeability before injection is prohibited by increased pressure resistance.

  4. Timing has to be tested in the laboratory using resident brine and reservoir temperature for various injection rates.

  5. When laboratory investigations are employed to define the extent of permeability reduction, the spatial distribution of permeability must be obtained. For this purpose the Liquid Minipermeameter apparatus[2] is suggested together with conventional coreflooding equipment.

  6. For rate dependent methods, injection through a fracture or a horizontal well can be considered as a means to overcome low injection rate restrictions.

  7. In the case of brine chemistry limitations, a pre flush might be considered as a remedy.

  8. Evidently there is no remedy for temperature limitations, therefore reservoir temperature is a controlling factor for choosing the right method to reduce permeability in some reservoirs.

  9. It is recommended that to select a permeability reduction method, temperature limitations should be considered first and then the other controlling factors. Also the method should exhibit technical and economical feasibility for the reservoir in question.

This paper was selected for presentation by an SPE Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A. Telex, 163245 SPEUT.

The authors wish to thank the Gas Research Institute and the Petroleum Department at the Colorado School of Mines for financing and supporting this study.

Vassilellis
G.D.
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Permeability Modification and Measurement in Water-Bearing Formations
"
M.S. Dissertation
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T-4444, Colorado School of Mines
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Golden, Colorado
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1993
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Vassilellis
,
G.D.
and
Graves
,
R.M.
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Point Permeability Measurements Using a Liquid Minipermeameter to study formation Damage Mechanisms.
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SPE 23785, presented at SPE International Symposium on Formation Damage Control
,
Laffayette, LA
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1992
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