Corrective natural fracture hydraulic fracturing in-situ stress measurement method

Abstract

The invention discloses a corrective natural fracture hydraulic fracturing in-situ stress measurement method. According to the method, a mechanical equation is established for shear stress widely existing in a natural fracture surface, and an in-situ stress tensor is obtained through inversion by searching for a natural fracture surface friction coefficient by use of a least square method and a computer program trial and error method. Through the method provided by the invention, the number of natural fractures needed by a conventional natural fracture hydraulic fracturing in-situ stress measurement method is substantially reduced, many hypothesis conditions set for an in-situ stress field during application of the natural fracture hydraulic fracturing in-situ stress measurement method are eliminated, the application difficulty of the natural fracture hydraulic fracturing in-situ stress measurement method is lowered, and the accuracy of the method is improved.

Description

technical field [0001] The invention belongs to the technical field of geological structure exploration and measurement, and in particular relates to a corrected in-situ stress measurement method of primary fracture hydraulic fracturing. Background technique [0002] The in-situ stress measurement method of hydraulic fracturing (Hydraulic Fracturing, which can be abbreviated as HF) is one of the important in-situ stress measurement techniques at present [1-2] . This method is one of the recommended methods in the recommended methods for determining rock stress issued by the Test Method Committee of the International Society of Rock Mechanics in 1987 and 2003. [3] . Although hydraulic fracturing in situ stress measurement method has many advantages [1-2] , but this method still has some unavoidable limitations. Example: determining the tensile strength of the rock mass in the test section [4-5] ;burst pressure may not correspond to induced crack initiation [6] ; Hydraul...

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Problems solved by technology

[0013] in the literature [12] In, Cornet pointed out three major limitations of the HTPF method: (1) The test workload is heavy; (2) It is necessary to select a single primary fracture that meets the test conditions, and it is required that the rock mass should not be very jointed; It is very difficult to find primary fractures in the same borehole; (3) Some assumptions about the in-situ stress state of the test area are required in advance

[0014] To sum up, hydraulic fracturing of primary fractures has achieved good results in solving the problems existing in hydraulic fracturing. However, hydraulic fracturing of primary fractures also has some problems in the application process, including: The test process is very long; the number of qualified primary cracks required for the test is too large to meet the requirements in many cases on site; how to eliminate the influence of the stress gradient on the test results; how to ensure that the selected structural surface is closed during the test process plane etc.

These problems, on the one hand, increase the difficulty of the application of primary fracture hydraulic fracturing, and on the other hand, restrict the application effect of this method

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