Abstract
Abstract An analytical technique has been developed to consider fluid compressibility and temperature changes when making mini-frac analyses. Mini-frac tests in which the effects of compressibility and changing temperatures are ignored can produce results that are as much as 75% in error. However, techniques for mini-frac analysis presented in current petroleum engineering literature are based on the assumption that fracturing fluid is incompressible and isothermal in nature. This paper examines the effects that fluid compressibility and temperature changes have on mini-frac analysis by presenting field cases analyzed by the method developed. The analysis was performed using both PK and CZ models as presented in literature. An example analysis using the PK model showed that when both temperature and compressibility effects are ignored, errors of 300% in calculated fluid loss coefficient and 75% in calculated fracture length are encountered. The same example using CZ models gave 200% and 33% errors in fluid loss coefficient and fracture length, respectively. Correcting for temperature and compressibility effects is considered through the use of "effective pressure drop," or pressure drop the mini-frac would have exhibited if ideal conditions had prevailed. Developing this concept allows the use of already developed type curves. The approach is analogous to pseudo pressure in well testing. When only compressibility effect is considered, only the magnitude and not the shape of ΔP versus dimensionless time graph is changed. Correcting for both temperature change and compressibility changed both shape and magnitude of the curve. It has been observed that a better match was obtained after such correction.
Published Version
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