Preparation method of normal temperature crosslinking aluminum crosslinker for shale gas fracturing fluid

Abstract

The invention relates to a preparation method of a normal temperature crosslinking aluminum crosslinker for a shale gas fracturing fluid. The preparation method includes the steps: firstly, dissolvingaluminum ion auxiliaries in water to prepare first mixed solution; heating the first mixed solution to reach the temperature of 50-80 DEG C, stirring the first mixed solution and adding an organic matter serving as a complex ligand to obtain second mixed solution; secondly, performing thermostatic reaction on the second mixed solution for 2-4 hours and keeping the second mixed solution clear andtransparent; adding pH (potential of hydrogen) regulators into the second mixed solution and adjusting the pH value of the second mixed solution to be 6.0-8.0 to obtain faint yellow homogeneous transparent liquid. The pH of the crosslinker prepared by the preparation method is 6-8, and corrosion of oil pipe equipment and the like is reduced. Effective crosslinking components are released at normaltemperature and can be crosslinked with low-concentration hydrolytic polyacrylamide in fracturing construction to form a stable gel system, the crosslinker has performances such as strong viscous elasticity, high temperature resistance and high salinity resistance, a most permeable zone can be limitedly plugged, water injection effects are improved, and gas well recovery ratio is increased.

Description

technical field [0001] The invention belongs to the field of fracturing crosslinking agents, and in particular relates to a preparation method of a normal temperature crosslinking aluminum crosslinking agent for shale gas fracturing fluid. Background technique [0002] Shale gas reservoirs have ultra-low permeability, large thickness, and well-developed natural fractures, requiring hydraulic fracturing to achieve industrial exploitation value. Shale gas reservoirs have extremely low porosity and matrix permeability, basically no natural productivity, and are deeply buried and have high formation pressure. Fracturing must be performed to achieve economical and effective development. Therefore, fracturing is the main technology for shale gas development. . Fracturing fluid is the working fluid for fracturing construction, which plays the role of transmitting pressure, breaking rocks, extending fractures and carrying proppants. Fracturing fluid usually contains additives such...

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Problems solved by technology

However, the cross-linking agent thus prepared has the following disadvantages: (1) the pH of the mixture is low, which seriously corrodes oilfield equipment; (2) the sulfate radical in the raw material can strengthen the scaling tendency of oilfield water; (3) adopt this method , the complexation between trivalent aluminum ions and citric acid is not sufficient, aluminum ions are easy to adsorb in the near wellbore area, or form gel in the near wellbore area, which cannot achieve the purpose of improving water injection effect and gas well recovery

This type of method for preparing cross-linking agents has the following disadvantages: (1) The synthesis temperature of the cross-linking agent needs to reach 95-110°C, the reaction time is as long as 6-8 hours, and the production process is complicated; (2) The synthesis water described in the patent is deionized Water, low conversion efficiency in industrial production

[0004] Shale gas fracturing fluid can effectively improve the recovery of gas wells, but the aluminum crosslinking agent in the shale gas fracturing fluid currently used has the following disadvantages: (1) it is easy to hydrolyze into precipitates under high temperature conditions. Metal ions such as aluminum ions do not undergo complexation reactions, and turn into hydroxides at high temperatures, and are insoluble in water: (2) and cannot effectively form gels under alkaline oil reservoir conditions; (3) its acid-base application range is not (4) The cross-linking agent is in a relatively stable state at room temperature, does not release the cross-linking active ingredient, and cannot undergo cross-linking reaction with partially hydrolyzed polyacrylamide at room temperature

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