an analog co 2 Experimental device and method for acid fracturing and acid etching crack process

Abstract

The invention discloses an experimental device simulating the CO2 acid fracturing and acid etching crack process and a testing method. A CO2 conveying unit, an acid liquid conveying unit, a liquid mixing tank of supercritical CO2 and acid liquid, and a rock plate holder are included, and a rock plate is installed in the rock plate holder; supercritical CO2 and acid liquid are pumped into the liquid mixing tank by the CO2 conveying unit and the acid liquid conveying unit correspondingly to be mixed, obtained mixed fluid is injected into the rock plate holder, and a liquid outlet of the rock plate holder is provided with a back pressure valve; and the liquid mixing tank is a cylindrical tank body which is arranged in a sealed manner; and the bottom of the tank body is provided with a supercritical CO2 inlet and a liquid inlet and outlet. The liquid outlet of the rock plate holder is sequentially connected with the back pressure valve, a cooling water jacket, a CO2 separation tank and a waste liquid tank, and the CO2 separation tank is further connected with an acid liquid neutralization tank. The experimental device and method provide a special device and testing method for accurately simulating the real acid etching form in CO2 acid fracturing.

Description

technical field [0001] The invention relates to the technical field of oil and gas field exploitation, in particular to a simulated CO 2 Experimental device and method for acid fracturing and acid etching crack process. Background technique [0002] Acid fracturing (acid fracturing) is an important technical measure for the commissioning and stimulation of carbonate oil and gas wells. It reacts chemically with the artificial (natural) fracture wall rock through the acid liquid to form groove-like or uneven high-permeability channels, thereby improving the seepage condition of the gas well and increasing the production of the oil and gas well. However, for low-pressure tight carbonate rocks, when using conventional acid fracturing technology, there are two obvious limitations: (1) the acid-rock reaction rate is fast, and the action distance in the acid liquid formation is small; (2) when a large amount of acid liquid enters the formation , due to the low formation pressure,...

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Problems solved by technology

[0004] At present, there is no simulated CO in public literature at home and abroad. 2 The experimental device and method for the acid etching crack process in the acid fracturing process, the invention patent application number 201010203373.0 discloses a test device and method for simulating the conductivity of acid etching cracks, but the test device cannot truly simulate CO 2 The process of acid etching cracks during energized acid fracturing is mainly due to: ① Lack of CO 2 Mixing with the acid liquid mixing device directly in the test pipeline is easy to form a slug-like mixed fluid, which cannot achieve a uniform mixing state, let alone control the foam dryness; ②The chamber of the rock sample holder is in the shape of a long arc cylinder The rock sample is loaded from the upper and lower parts of the cylinder chamber perpendicular to the flow direction of the test medium, and then the upper and lower two long arc cylinder pistons are installed, and each piston is only sealed by a rubber ring. CO 2 When the fluid mixed with acid is etched by acid, it is very easy to leak, posing serious safety hazards, and the pressure of the reaction environment is not easy to control; ③The waste liquid collection design at the end of the device process cannot realize the gas-liquid separation of the mixed fluid. When depressing the valve, due to the sudden drop in pressure, there is CO 2 Potential safety hazards caused by high-pressure gas and corrosive acid mist; ④The entire process pipeline is not designed with an insulation layer, which causes heat loss during the flow of the test fluid, and the temperature is difficult to control, resulting in the inability to form a stable phase of supercritical CO 2 mixed fluid with acid

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