At present, in the process of oil field exploitation, in the face of the problems of hydraulic fracturing using a lot of water resources and serious pollution of fracturing flowback fluid, the reuse of flowback fluid is the development trend of oil and gas field industry in the future, regardless of cost or environmental protection.
With the rapid development of oilfield chemicals, the demand for fracturing fluid in field construction is getting higher and higher, and the chelating agent corrosion and scale inhibition fracturing fluid meets the comprehensive development needs of oilfield additives in the future.
When the backflow treatment liquid is reused, because the backflow liquid contains a large number of divalent ions, such as Ca2+, Mg2+ and Fe2+:
1 has great influence on the viscosity and temperature resistance of thickener.
2. Because the reverse drainage treatment fluid contains a large number of calcium and magnesium ions, carbonate ions and sulfate ions, it is easy to scale and precipitate at a certain concentration and temperature. When the fracturing fluid made from reverse drainage is injected into the well again, it is easy to scale and block the diversion channel supporting the fracture, which greatly reduces the fracturing stimulation effect and leads to production reduction or even shutdown.
In view of the above problems, our company, Southwest Petroleum University, China Youshi University, Xi Youshi University and other universities, after years of in-depth analysis, experimental simulation and field application, have developed chelating additives for different reverse-discharge treatment fluids and different fracturing fluid formulations in view of the complex situation of different reverse-discharge treatment fluids in many oilfield blocks in China, such as Changqing Oilfield, Daqing Oilfield, Southwest Oilfield and Karamay Oilfield. It not only effectively reduces the influence of Ca2+, Mg2+ and Fe2+ plasma in reverse drainage on the viscosity and temperature resistance of fracturing fluid, but also solves the problem of corrosion and scaling of reinjection channel, especially the QH-75 10 product developed by our unit in 90396 at 133709, which has been evaluated by many oilfield units of the Institute of Oil and Gas. On the basis of effectively improving the performance of fracturing fluid, the excellent results of scale inhibition rate are obtained: calcium carbonate > 95%, calcium sulfate > 95% and barium sulfate > 95%, which saves the secondary addition of reinjection water and corrosion inhibitor and scale inhibitor in gathering pipeline, reduces the labor intensity of manual dosing on site, and conforms to the direction of comprehensive development of oilfield additives.