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RETURN PERMEABILITY STUDY

Liquid Casing® products non-invasive nature were extensively evaluated in a laboratory test program carried out by STIM-LAB Inc. in Duncan, Oklahoma, (File Number SL 1815.).

 

The formation evaluation studies used two types of formations with a 2% (7 lb/bbl potassium chloride (KCI) brine containing 4 lbs/bbl of Liquid Casing® and polymers of either Xanthan gum or Xanthan gum plus, and some polyanionic cellulose (PAC). The properties of the fluids tested are given in the following table.

 

Properties of Polymer Based Fluids in 2% KCI Brine with 4 LBS/BBL Liquid Casing®

Parameter Xanthan Gum Xanthan Gum/PAC
FANN 600, cps 44 31
FANN 300, cps 34 20
Apparent Viscosity, cps 22 15.5
Plastic Viscosity, cps 10 11
Yield Point, lbs/100 sq. ft 24 9
Gel Strength, 10 sec, lbs/100 sq. ft 14 4
Gel Strength, 10 min, lbs/100 sq. ft 20 6
API Fluid Loss, ml 12.7 16.8

The flow studies were conducted on two contrasting cores. One core was a tight Berea sandstone, approximately 50 millidarcies, and the other, a high permeability Brady sandstone approximately 1,000 millidarcies.

 

The cores were saturated with the brines and then the initial permeability was determined to oil, Klearol, followed by the polymer/Liquid Casing® fluid until a pressure differential of 500 psi or higher was achieved. The core was shut in for 3 hours, and the initial return permeability determined to the oil. A KCI solution was flushed across the core and a final permeability to oil was determined. The results of these experiments are summarized in the following tables:

 

Formation Damage Testing for Liquid Casing® in a 2% KCL Brine with Xanthan Gum

Initial Perm. Initial Oil Perm. Final Oil Perm. After KCI Flush % Original Perm.
59 md 32 md 60 md 100 md
910 md 240 md 900 md 99 md

Formation Damage Testing for Liquid Casing® in a 2% KCL Brine with Pac/Xanthan Gum

Initial Perm. Initial Oil Perm. Final Oil Perm. After KCI Flush % Original Perm.
59 md 25 md 59 md 98 md
900 md 380 md 780 md 87 md

The flow rate across the core face in these experiments was very low, at about 0.02 ft /min, consequently, the filter cake resembled a static condition rather than a dynamic one; which is the reason why the KCI flush was remarkably effective as it helped to physically disperse the cake. Usually with a polymer filter cake, a drastic treatment such as acid would be needed in order to significantly regain permeability.

 

These studies show that the Liquid Casing® can quickly form a filter cake which will prevent the invasion of the polymers into the core. A simple mechanical flushing action fully restores the core to its original permeability. These results demonstrate the non-damaging nature of Liquid Casing®, which ensures that the polymer remains in the filter cake rather than penetrating the core.

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