The Research Of Plugging Mechanism And Oxidative Blocking Removel System And The Application In The Polymer Injection Well In The Bohai Oilfield

Since the offshore oilfield gradually developed the technology of polymer flooding and expanded the industrial tests from 2003,the polymer flooding technology has achieved a significant increase in oil and reduce the influence of water,which has become one of the important means for Bohai oilfield's exploration,stable production and increasing productivity.However,with the increasing injection volume of the polymer solution and the prolonged injection time,the plugging problem is becoming serious day by day.Thus,it is very important to develop high-performance plugging removel agent for offshore oilfield.First,the composition of blockage of one representative oilfield in Bohai was analyzed and the plugging reason includes the plugging due to polymer,clay mineral,the deposition regarding iron and sulfur,carbonate and oil contamination.And also the combined action of different plugging stuff.Then,two fundamental formula were screened based on the plugging reason: one is 1% CN-1and the other one is 4%HCl+3%HF.The first formula is encapsulated solid oxide,thus it can be easily shipped.It has high safty and degradation effect,therefore it is suitable for being used in offshore oilfield.The second,namely the acid,can be used to greatly reduce the plugging through dissolving various minerals.The results of core flow experiment show that the blocking removal effect by using the combination of the oxidizing agent and acid is far better than that only using oxidizing agent or acid.The blockage removal system was futher optimized based on the fundamental formula,and the corrosion inhibition experiment,the sulfur removal test,emulsification test and core flow experiment were conducted to evaluate the property of plugging removel agent.The actual condition of the blocked reservoir was simulated by alternatively injecting polymer solution,plugging mineral and Bohai heavy oil.In this case,the plugging removel effect can be significantly enhanced by adding surfactant and extension agent to the basic plugging removel agent.And the finally optimized plugging removel system includes two parts: one is CN-1+0.4% extension agent+0.3%OP-10+0.2%EDTA,it is named JD-1,the other one is 4%HCl+3%HF+0.3%OP-10+0.2% corrosion inhibitor2+0.2%EDTA,and it is named JD-2;the core flow experiment was conducted by using double-fluid method,and the permeability recovery rate can be as high as 91.5%.The plugging removel agent JD-1 and JD-2 was used to remove plugging in the oilfield and also was used to compare with the effect of CN-1.Good plugging removel effect was obtained and the plugging removel effect of JD-1+JD-2 is far better than CN-1.