An Evolving Approach in the Analysis of Stress-Test Pressure-Decline Data

Abstract

Summary Stress testing (microhydraulic fracturing) is recognized by the petroleum industry as the most direct method of determining the minimum in-situ (closure) stress for a given reservoir rock and the surrounding formations. In general, it is variations of in-situ stress between formations that dominates hydraulic fracture height growth and overall fracture geometry. Misleading interpretations of stress-test data (cased or openhole) can lead to significant errors in the prediction of stress contrast between the producing and bounding rock layers as well as an erroneous estimation of closure stress in the productive interval. In either case, hydraulic-fracture-treatment designs based on this information may not be designed optimally, and the subsequent interpretation of the fracturing treatment pressure response may not be correct. We present an evolutionary approach in the analysis of stress-test data that leads to more consistent results relating directly to actual fracture-treatment pressure responses. Although the emphasis in this paper is on cased-hole stress-test-data interpretation, the methodology presented is also applicable to openhole stress testing and larger-scale pump-in/shut-in (i.e. calibration or minifracture) pressure falloff responses.