Study on evaluation method of fracture forming ability of shale oil reservoirs in Fengcheng Formation, Mahu sag

Abstract

In order to effectively evaluate the complex fracture network forming ability of Fengcheng Formation shale oil reservoirs in Mahu sag, the core in a vertical well of Fengcheng Formation in Mahu sag was considered as the research object. Through coring sampling, indoor experimental testing, combined with logging data and comprehensive interpretation, the rock mechanical properties and in-situ stress profile of the reservoir are systematically obtained. The results show that the shale oil reservoir of Fengcheng Formation in Mahu sag has deep burial depth, large absolute value of in-situ stress, high compressive strength and elastic modulus, good brittleness, low development degree of reservoir bedding, but relatively developed natural fractures. Among these features, brittleness, natural fractures, compressive strength and in-situ stress are the main controlling factors affecting the reservoir fracture propagation. The acoustic emission b value during the process of rock fracture can characterize the ability to form complex fracture network. By evaluating the correlation coefficient between each main control factor and acoustic emission b value for the first time, the weight value of each factor on fracture forming ability is determined. So as to establish the quantitative evaluation model of reservoir fracture forming ability, and quantitatively evaluate the fracture forming ability of the reservoir section. Applying the quantitative evaluation model of fracture forming ability to the logging data of the well. The evaluation results of the whole well section are consistent with the liquid production profile of the well, which shows that the research model established by this method is reliable. That also provides a guidance for the fracturing transformation and horizon optimization of horizontal wells in Fengcheng Formation shale oil reservoir in Mahu sag in the later stage.