Study Of Deep And Long-acting Plug Removal Technology For Polymer Injection Wells

With the application of polymer flooding technology in the oilfield development, theproblem of plugging in polymer injection wells becomes more and more serious. It is verydisadvantageous for oilfield to enhance oil recovery. And on the later period of polymerflooding, the plugging depth of injection well increases, it is difficult to remove the plug ofinjection well. At present, it has the problem of small plug removal radius and short valid plugremoval period with using fracturing and chemical method separately, which are not ideal forthe plug removal effects. In order to solve the above problem, this paper combined fractureplug removal with chemical solution plug removal, and develop a long-acting plug removalsystem what is suitable for deep removal of polymer plugging after fracturing, to meet theneed of long-acting unblocking for deep polymer injection well.The plug removal system contains degradation of main agent, auxiliary agent, speedcontrol agent and wettability reversal agent. The mixed solution of the main agent and theauxiliary agent can degradate polyacrylamide solution5000mg/L completely, the degradationtime is about24h, and it is suitable for deep plug removal. Speed control agent can control thetime of polymer degradation between12-24h. Wettability reversal agent can reduce theadsorption of polymer solution in the reservoir core, and can extend the valid period of plugremoval.Through the research on compatibility, rheological properties and damage on reservoir,the results showed that the fracturing fluid system and polymer solution have goodcompatibility. And various components of fracturing fluid system and remnants of fracturingfluid after gel breaking have no effect on the effect of blocking solution plugging system.With injection of fracturing fluid system components and the residual liquid in reservoir coresof polymer flooding, the blocking removal rate of blocking system can reach above80%.Through the simulation experiments of the core plugging indoor, it show that plugremoval rate of natural core with the general permeability after polymer flooding can reachabove85%after the fracturing and chemical solution plug removal, and the polymer injectionblocking rate after the plug removal dropped more than20%. The technology of deeplong-term plug removal and fracturing plug removal are compared at two wells on site, thewell with the deep and long-term plug removal have more injection volume and longproduction time.