Experimental device and method for simulating single-crack flowback after shale gas fracturing

Abstract

The invention relates to an experimental device and method for simulating single-crack flowback after shale gas fracturing. The experimental device is mainly composed of a pump set, a device body, a hydraulic pressure and temperature control device, and a tail monitoring and liquid waste disposal device. The device body mainly refers to an improved rock core clamp holder specially used for manufacturing a rock core, confining pressure is applied through the hydraulic pressure device, and the temperature control device heats hydraulic oil to form a high temperature for simulation of the stratum environment; in the experimental process, displacement meters on the upper side face and the lower side face of the rock core clamp holder can detect crack displacement change, and the sand production rate and the fluid flow speed can be monitored in real time through the tail monitoring device. By the adoption of the experimental device and method, the stratum high-temperature and high-pressure environment can be simulated, and on the premise that the flow conductivity of cracks of different crack lengths and crack widths is detected, the crack pressure drop, the sand production rate, the propping agent embedding degree and the propping agent backflow and settlement rule are detected; moreover, artificial marble rock cores are used, and the environment gets more close to the true stratum environment compared with the mode that steel blocks are used for simulating cracks.

Description

technical field [0001] The invention relates to an experimental device and method for simulating single fracture flowback after shale gas pressure, belonging to the technical field of oil and gas field development. Background technique [0002] Shale gas reservoir is a kind of tight gas reservoir, which usually requires fracturing to obtain effective industrial gas flow. Shale gas fracturing usually uses slick water or clear water to carry proppant into the formation with high pressure, high displacement, and low viscosity. After effective fractures are formed, the fracturing fluid lost to the formation should be maximized. Flow back out to reduce damage to the formation, and at the same time reduce the return flow of the proppant and enable the proppant to settle effectively, so as to improve the fracture conductivity and the permeability of the oil and gas layer near the wellbore, and improve the effect of fracturing stimulation. Therefore, it is particularly important to...

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Problems solved by technology

[0003] The domestic and foreign researches on fracturing fluid flowback process after shale gas pressure mainly stay in theoretical research. The traditional full three-dimensional fracture geometry simulator system studies the settlement law of proppant during fracture closure, but does not consider the flowback process. Factors such as pressure drop, proppant return flow, and settlement law; early slot model experiments were filled with proppant in the middle of the slot, and the experimental fluid was pumped in from one end and flowed through the filling layer. There were observation devices on both walls to observe the proppant The size of the slot can be changed, and this method can simulate the influence of the change of fracture width on the proppant reflow, but it does not consider the effect of closure pressure; the circular tube-perforation model mainly examines the critical flow rate of the proppant reflow, and the method is Fill the stainless steel tube with proppant and let fluids with different flow rates pass through. This method cannot simulate the change of fracture width and closure pressure; the most classic method is the API linear flow core holder. The advantage of this method is that it takes pressure and temperature into account The critical condition of proppant backflow under different fracture widths and flow rates can also be obtained, but this method does not consider the fracture length, fracture contact surface geometry, sand concentration, and sand distribution. The influence of ratio on proppant reflux and the influence of factors such as sand production volume, sand production critical velocity, proppant embedment degree, pressure drop during flowback, fracturing fluid fluid loss, etc.

The most commonly used API conductivity model and grid fracture rectangular conductivity model can only measure the conductivity of fractures, but cannot dynamically study the influencing factors in the process of flowback after shale gas pressure

The experimental device and method for simulating flowback technology after shale gas pressure is currently unable to systematically consider the influence of various factors. Therefore, it is of great significance to develop an experimental device and its working method that can simulate the process of flowback after shale gas pressure

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