The standard terms or nomenclature used in permeability surveys are as 

 follows: (1) capacity - the volume of fluid injected into an individual permeable 

 zone in gallons per minute; (2) capacity index - the volume of fluid injected 

 into an individual permeable zone in gallons per minute for each pound per 

 square inch of differential pressure; and (3) specific capacity index - the 

 volume of fluid injected into an individual permeable zone in gallons per 

 minute for each pound per square inch of differential per foot of thickness of 

 the zone at the bore hole. 



The term "capacity" is the most generally used index for planning initial 

 acidizing procedures. For most work-over jobs it is sufficient. For comparing 

 permeability surveys on the same well before and after acid treatment, or before 

 and after a work-over job, the capacity index should be used, since the injection 

 rates into the various zones must be corrected for the differential pressure applied. 



The "specific-capacity index", which is a direct measure of the actual 

 effective permeability of each permeable zone, appears to be valuable in locating 

 undesirable water or gas zones in a well, particularly in intermediate zones pro- 

 ducing these fluids. Where a well is producing from a series of breaks or perme- 

 able zones, all of which are connected to a common water or gas reservoir, it 

 is reasonable to assume that the most permeable zones will be depleted of oil 

 more rapidly and that water or gas encroachment will begin through these 

 particular zones. 



It should be noted that the comparative-permeability survey is used to de- 

 termine only the position of the permeable zones in the well, the thickness of 

 these zones in the bore hole, and the relative capacities of the various zones. It 

 is not used for direct determination of saturation, porosity, or fluid content of 

 the permeable zones, although when used in connection with other well informa- 

 tion or well logs it will assist at times, in the evaluation of the fluid content of 

 such zones. These particular comparative-permeability logs, in their role of 

 locating and evaluating zones with respect to permeability, appear to be more 

 reliable and accurate than any other method in use. 



The comparative-permeability survey cannot replace or detract from the 

 value of other well-logging methods that show the saturation or fluid content of 

 the producing horizon. In work-over jobs, acidizing work in particular, satura- 

 tion and fluid-content logs should be used in conjunction with the permeability 

 survey in planning the program. The permeability survey as it is applied now 

 has an accuracy of only about 95 or 97 percent; therefore the permeable zones 

 in a producing horizon that contain 3 to 5 percent of the total capacity of the 

 well may not be recognized. This does not mean, however, that these zones will 

 not produce oil if they are acidized properly. A number of instances have 

 occurred where zones, indicated as impermeable because of mudding or other 

 factors, have shown good saturation on the sample log. After selective acidizing 

 of these zones, production was greatly increased. Also, in instances where no 



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