Error analysis and discussion of determining the maximum horizontal principal stress by hydraulic fracturing based on the compliance analysis of testing system
The large error in the results of the maximum horizontal principal stress is a prominent problem in the in-situ stress measurement by hydraulic fracturing method.In this paper,the differences and applicability of several main formulas used to calculate the maximum horizontal principal stress are compared and analyzed on the basis of the domestic and foreign hydraulic fracturing in-situ stress measurements regulations or suggested methods.Taking the test system compliance as the main influencing factor,the error sources and physical mechanism that affect the calculation accuracy of the maximum horizontal principal stress are analyzed in detail and depth.On this basis,taking the measured hydraulic fracturing data of the deep-hole obtained from the granite borehole in Beishan,Gansu as an example,the fracture reopening process is numerically analyzed based on the KGD theoretical model,and the influence of system compliance on the calculation result of the maximum horizontal principal stress is quantitatively studied.Taking the theoretical calculation value of eliminating the influence factors of compliance as correction value,the measured data and heoretical correction valueof 6 testing intervals in the hole depth range of 18-930 m are given.The results show that the error of the maximum horizontal principal stress measurement results increases gradually with the increase of test depth due to the influence of the test system compliance.When the test depth is 930 m,the relative error of the measurement results is 24.55％.The research results can provide a reference for the error problem of the maximum horizontal principal stress measurement results in relevant engineering applications,also provide a new idea and technical approach for the error analysis and further improvement of the reliability of the hydraulic fracturing in-situ stress measurements.
rock mechanicshydraulic fracturing methodtest system compliancere-opening pressurethe maximum horizontal principal stresserror analysis
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