Method and device for simulating fissure expansion of hydraulic fracturing in plane distribution

Abstract

The invention discloses a method and a device for simulating fissure expansion of hydraulic fracturing in plane distribution, the method comprises the following steps: firstly, the front surface and the rear surface of a specimen are clamped with two pieces of transparent glass steel, fastening bolts are tightened, the upper surface and the lower surface of the specimen are clamped tightly with metal loading plates, and a constant voltage and constant current pump is connected with a stainless steel sleeve part in the specimen; the constant voltage and constant current pump is opened for injection of a liquid into the specimen, the specimen is gradually completely broken, in the loading process, and continuously changing pictures of the speckle field of the surface of the specimen are obtained by a high-speed camera, and stored in a computer; and change rules of the displacement field and the strain field of the surface of the specimen can be obtained by analysis software in a load application process. Based on digital speckle expansion technique and through the analysis of the change rules of the displacement field and the strain field, the interaction mechanism between artificial and natural fractures in the artificial crack propagation process and after intersection of the artificial and natural fractures can be obtained, and a foundation is laid for studies on formation mechanism of shale reservoir fracture network cracks.

Description

technical field [0001] The invention relates to the field of petroleum engineering, in particular to a method and device for simulating the expansion of hydraulic fracturing fractures in a plane spread. Background technique [0002] Due to the extremely poor permeability of unconventional shale reservoirs, industrial production capacity must be achieved through volume fracturing to form fracture networks. Therefore, the formation mechanism of fracture network fractures in unconventional shale reservoirs is a hot and difficult issue in the field of energy research in the world. . Natural fractures are developed in unconventional shale reservoirs. When artificial fractures meet natural fractures and turn to expand, complex fracture networks may be formed. However, when artificial fractures pass through natural fractures and expand, fracture networks cannot be formed. Therefore, the analysis of artificial fractures and natural fractures The propagation law of natural fractures...

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Problems solved by technology

[0003] In the existing indoor hydraulic fracturing simulation experiments, single fracture propagation can be simulated well, but there are the following deficiencies in simulating network fracture propagation: (1) The size of the specimen is limited, and the fracture size of the general experimental device is 300mm ×300mm×300mm (Langfang Branch has developed a large model hydraulic fracturing device of 1000mm×1000mm×1000mm, but the experiment cost is high, the specimen is large in size and difficult to process), the network cracks cannot fully develop in the specimen, therefore, It is limited in the study of compressibility evaluation experiments of tight rock or shale; (2) The crack propagation occurs inside the specimen, and the crack shape is not easy to observe. Using CT scanning technology is expensive and cannot be invested in a large number of experimental studies , the acoustic emission test device can only perform qualitative description of cracks, and is greatly affected by the external environment, so it is impossible to accurately observe the crack shape, resulting in the crack shape of the specimen after compression cannot be observed directly

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