Ultrasonic testing method for hydraulic fracturing of full-diameter rock cores independently loaded by axial stress

Abstract

The invention relates to a full-diameter rock core hydrofracturing ultrasonic detection method under an independent axial stress loading condition. An axial loading system is designed as two semi-cylindrical anvils, and thus two sets of independent axial loads can be provided on a rock core end surface. The axial loading system is supplied with pressure through a hydraulic pump; hydraulic pressure is conducted to the two semi-cylindrical anvils inside a clamp through controllable valves respectively; the semi-cylindrical anvils are moveable parts which can displace in an axial direction, and thus two sets of axial stress can be generated in a rock core inside the clamp; and ultrasonic wave generation / receiving probes are mounted on end surfaces of the anvils, after the rock core is stable after stress deformation, a central hole of the rock core is filled with fracturing fluid, then a crack of a certain form is generated, and a general extension direction and the extension range of the crack can be detected by using an ultrasonic technique. The method is an evaluation method applicable to research on expansion rules of hydraulic fracture and natural fracture in a complex crustal stress state, and the method is scientific and reasonable in design, accurate in evaluation method and relatively high in creativity.

Description

technical field [0001] The invention belongs to the field of petroleum and natural gas engineering, and relates to indoor experimental evaluation of oil and gas field exploitation technology, in particular to an ultrasonic detection method for hydraulic fracturing of a full-diameter rock core independently loaded by axial stress. Background technique [0002] The principle of conventional hydraulic fracturing simulation experiments is to inject fracturing fluid into the core through the fracturing fluid injection pipeline under confining pressure and axial pressure, and at the same time, external sensors monitor the load stress and pump pressure, and record the pump pressure under different triaxial stress test conditions. The curve of pressure and time is used to study the relationship between triaxial stress and hydraulic fracturing pressure. [0003] Conventional methods can only provide a set of axial compression loading on the end face, but the actual geological conditi...

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Problems solved by technology

[0003] Conventional methods can only provide a set of axial compression loading on the end face, but the actual geological conditions are disturbed by natural fractures, the in-situ stress is not a certain value, and the actual stress state of the rock in the formation may be twisted, sheared and other complex situations, so Traditional technical methods can only simulate the single stress state of the rock, and cannot simulate the rock distortion or shear stress state

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