Method for evaluating compressibility of tight reservoir based on stress-strain curve

Abstract

The invention discloses a method for evaluating compressibility of a tight reservoir based on a stress-strain curve. The method comprises the following steps: testing the stress-strain curve of a rocksample under a certain confining pressure to obtain elasticity modulus and Poisson's ratio of an elastic deformation stage so as to obtain the volumetric strain of the elastic deformation stage and obtain crack volume strain; determining an expansion point of the rock sample according to an axial strain-crack volume strain relationship curve and obtaining the strain energy size through the stress-strain curve envelope area formed from the expansion point to the break point in an enclosing way; and establishing a compressibility index mathematical model of the surrounding rock by performing nondimensionalization on the change numerical value of the parameter, and calculating and comparing the size. The experimental evaluation method provided by the invention is suitable for the unconventional resources such as shale gas, coal bed gas, compact oil gas and a hot dry rock, and can be applied to the conventional oil and gas reservoir with low permeability and ultralow permeability. The confining pressure effect is considered and the artificial fracture density formed after the rock is expanded is considered, so the method can be used for evaluating the artificial joint network formingcapability of the formation condition and guiding the volumetric fracturing construction to select wells and select formations.

Description

technical field [0001] The invention relates to an oil and gas extraction technology, in particular to a method for evaluating the compressibility of tight reservoirs based on stress-strain curves. Background technique [0002] Hydraulic fracturing technology is a necessary means to increase the production of low- and ultra-low-permeable reservoirs, and it is also one of the effective ways to establish hot dry rock artificial heat storage and improve its heat recovery rate. A network of fractures to increase the contact area with the reservoir. Therefore, evaluating rock compressibility is the basis for evaluating whether a reservoir is suitable for fracture network fracturing. [0003] At present, there are two shortcomings in the evaluation of compressibility. One is that the confining pressure is not considered, and most of them are evaluated under uniaxial loading conditions; the other is that the real artificial fracture density is not considered, and most of the actua...

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Problems solved by technology

[0003] At present, there are two shortcomings in the evaluation of compressibility. One is that the confining pressure is not considered, and most of them are evaluated under uniaxial loading conditions; the other is that the real artificial fracture density is not considered, and most of the actual artificial fractures are approximated by the natural fracture density. density

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