Coagulation treatment method for high-viscosity fracturing waste water of low-permeability oilfields

Abstract

The invention relates to a coagulation treatment method for high-viscosity fracturing waste water of low-permeability oilfields. A coagulant during high-viscosity fracturing waste water treatment comprises following components: 500-1000 mg / L of polyaluminum chloride, 50-100 mg / L of potassium carbonate, 1000-3000 mg / L of loessal soil having a size of 80 / 100 meshes and 7-15 mg / L of polyacrylamide. The loessal soil, the polyaluminum chloride, the potassium carbonate and the polyacrylamide are added in order. The coagulation time is controlled within 30 min. The mud amount is lower than 10%. After treatment, the SS of liquid supernatant is controlled to be lower than 10 mg / L. The method is used for treating the high-viscosity fracturing waste water having viscosity higher than 5 mPa.s, and overcomes disadvantages of conventional coagulation, namely incapability of effectively removing impurities in the high-viscosity fracturing waste water, superficial floc, difficult settlement, and large mud amount.

Description

technical field [0001] The invention relates to the field of waste liquid treatment, in particular to a coagulation treatment method for high-viscosity fracturing waste liquid (fracturing waste liquid viscosity > 5 mPa.s) in low-permeability oilfields. Background technique [0002] Oil well fracturing reservoir stimulation is a common measure for low permeability oilfield development and old well stimulation, but the fracturing operation will produce a large amount of fracturing waste fluid. Fracturing waste fluid has the characteristics of high viscosity and high COD, and contains a variety of high molecular polymers, suspended solids, crude oil, bacteria and microorganisms that are difficult to biodegrade, which have adverse effects on the environment and human health. The fracturing waste fluid contains a large amount of organic matter such as guar gum, and needs to be cross-linked to form a gel due to the need for sand-carrying; therefore, high viscosity is a prominen...

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Problems solved by technology

[0004] The purpose of the present invention is to provide a coagulation treatment method for high-viscosity fracturing waste fluid in low-permeability oilfields; in the conventional coagulant system based on PAC and PAM, adding K 2 CO 3 It can not only adjust the pH of the waste liquid, remove some calcium and magnesium ions, and K + It is beneficial to the stability of the reservoir and is beneficial to the reuse of treated water; in order to overcome the shortcomings of high-viscosity fracturing waste fluid, such as poor treatment reaction effect and difficult sedimentation of flocs, considering the requirements of convenient material acquisition and low cost, local loess loess is selected as a coagulant, which can be used as a coagulant. Promote the further compaction of flocs, accelerate the sedimentation, improve the treatment effect and wastewater recovery rate

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