(Z&afrt&i 37 



SPECIAL 



APPLICATIONS OF 

 DST PRESSURE 

 DATA 



C. A. Einarsen 



J. P. Dolan 



and 



G. A. Hill 



INTRODUCTION A drill-stem test is a temporary completion 



designed to sample the formation fluid and 

 to establish the possibility of commercial production. Early pressure recording 

 devices were used merely to verify proper operation of the testing tool. Until 

 recently the accuracy of the pressure gauges has been insufficient for any 

 reliable quantitative use of the recorded pressures. In view of the need for 

 more reliable formation evaluation and as a result of the recent interest in 

 exploration work employing the concept of hydrodynamic entrapment, (Hill, 

 1951, 1954; Hill and Knight, 1956; Hubbert, 1953) better pressure recording 

 gauges are now in use. These devices can record pressure within 1 percent 

 above 1000 psig and can detect differential pressures as low as !/2 P s ig- 



In addition to formation pressure, several other reservoir characteristics 

 can be determined from DST charts; namely, well productivity, formation 

 permeability, wellbore damage, and the possible existence of barriers (faults, 

 pinchouts, changes in permeability, etc). 



This chapter presents a practical method to interpret DST pressure charts 

 for formation pressures and many other reservoir properties, a method that has 

 been developed in analyzing approximately 4000 DST charts during the last 

 five years. The techniques used are a composite of published articles on drill- 

 stem testing (Black, 1956; Olson, 1953), together with well-known pressure 

 build-up analysis methods. 



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