Method for treating and reusing fracturing backflow fluid of shale gas

Abstract

The invention discloses a method for treating and reusing fracturing backflow fluid of shale gas. The method comprises the following steps: (a) oxidizing Fe<2+> in original fracturing backflow fluid into Fe(OH)3, so as to obtain oxidized fracturing backflow fluid; (b) carrying out water quality analysis on the oxidized fracturing backflow fluid; (c) making comparison on the water quality of the oxidized fracturing backflow fluid and a reuse liquid preparation water quality requirement, and judging whether the concentrations of Ca<2+> and Mg<2+> in the oxidized fracturing backflow fluid of the shale gas are qualified; (d) if yes, sequentially carrying out coagulation, flocculation, sedimentation and filtration on the oxidized fracturing backflow fluid, and if no, sequentially carrying out coagulation-pH increase, ionic reaction, flocculation, sedimentation, filtration and pH value adjustment on the oxidized fracturing backflow fluid, so as to obtain treated fracturing backflow fluid; and (e) directly reusing the treated fracturing backflow fluid for liquid preparation or directly storing the treated fracturing backflow fluid. The method can adapt to the characteristics that the change of the water quality of the fracturing backflow fluid of the shale gas is large and reuse fracturing construction liquid preparation standards are different, and the instant continuous treatment can be realized.

Description

technical field [0001] The invention relates to the technical field of waste water recycling in oil and gas fields, in particular to a method for treating and recycling shale gas fracturing flowback fluid. Background technique [0002] Shale gas is natural gas that occurs in shale formations, which belongs to unconventional natural gas, and is mainly exploited by hydraulic fracturing. Hydraulic fracturing is a mining method that uses high pressure to drive fracturing fluid into the ground to hydraulically break the formation, thereby releasing the oil or natural gas reserves therein. After the hydraulic fracturing operation is completed, part of the liquid will be drained back to the ground, and the liquid that is drained back to the ground is called fracturing flowback fluid. The fracturing of a single shale gas well often consumes 20,000m3 of water 3 Above, 10%-50% of the flowback before the completion of the well, enter the production stage and still flow back at ten to...

AI Technical Summary

Problems solved by technology

[0004] In the process of realizing the present invention, the inventors found that there are at least the following problems in the existing fracturing flowback fluid treatment and reuse technology: most of them mainly relate to the conventional vegetable gum fracturing fluid detection or treatment device or recycling method for oil field stimulation, The slick water fracturing fluid system mainly used in shale gas development is not very specific, such as patent application number 200910071306.5, patent application number 201010113164.7, patent application number 201010237746.6, patent application number 201210264645.7, patent application number 201310545858.1, patent application number 201310649326. ; Although there are patents claiming that shale gas fracturing flowback fluid can be processed, the final destination after treatment is unknown or the goal is not to reuse, such as patent application number 201210210209.1, patent application number 201210287197.2, and patent application number 201210473701.8; another patented process Although it claims to be able to process shale gas fracturing flowback fluid for reconfiguration of fracturing fluid, it cannot adjust the degree of treatment and target for changing water quality of flowback fluid, such as patent application number 201310108977.0; in addition, patent application number 201110401452.7 It is a slick water formula; patent application number 201410617945.8 mainly proposes a performance evaluation method for shale gas fracturing flowback fluid reuse and a treatment method to prevent flowback fluid from deteriorating during storage. Filtration and reverse osmosis are too simple, high operating costs, and still produce a certain amount of dope

[0005] "Experimental Research on Treatment Process of Shale Gas Fracturing Flowback Fluid" (Xu Jian, Li Wenquan. Petroleum Machinery, 2013, Vol. 41, Issue 11) proposes that chemical coagulation / flocculation→electrocoagulation→filtration can meet the requirements of flowback fluid. Requirements for repeated use; this process repeatedly uses 2 flocculation processes, and after destabilization, the water quality directly enters the filter unit without sedimentation, which may cause excessive solid load of the filter unit and frequent backwashing

In the current development practice, natural sedimentation→filtering and intercepting larger particles are used to directly dilute and repeat the liquid preparation, but this treatment method cannot achieve instant and continuous treatment, and is only suitable for the situation where the number of wells in the early stage of development is small and the fracturing operation is infrequent

There are also attempts to use electrocoagulation → inclined plate sedimentation → filtration to mainly remove colloidal substances and suspended particles in shale gas fracturing flowback fluid. There is basically no removal effect for metal cations, so only the initial flowback liquid (accounting for about 10-30% of the overall flowback liquid) can be recovered, and large-scale recovery of the flowback liquid cannot be realized

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