Research On Low Permeability Reservoir Protection Technology For Duanliubo Oilfield

Low permeability oil and gas resources occupies an important position in our country.It is abundant,widely distributed and has great development prospects.However,due to the special character,the resources is difficult to exploitation and easy to damage.So,it is significant for achieving sustainable development of China petroleum industry that the rational development of low permeability oil and gas field,reducing the formation damage and improving exploitation efficiency.Duanliubo field,low-permeability reservoir,is located between the Kongdian tectonic belt in southern Huanghua depression and Wumaying tectonic belt.It has reservoir damage during exploitation.In this paper,considered the current status of research in low permeability reservoir damage and protection technologies,we analyse the reservoir characteristics and do reservoir sensitivity evaluation test to Duanliubo field.Further,Analyze the reasons of formation damage in the region,and optimize the work-over fluids.Low permeability reservoir of Duanliubo Oilfield has high content of clay,small porosity and permeability,likely to cause water sensitivity and water-block damage.The formation water contained NaHCO₃ is not compatible with the work-water contained calcium ion.Indoor sensitivity experiments show that: the reservoir velocity sensitivity is weak.The water sensitivity and salt sensitivity is strong;it has acid sensitivity to mud acid and acidified with hydrochloric acid can improve reservoir permeability.The fractured sandstone reservoir has stress sensitivity and the porosity reservoir sensitivity is weak.For the damage of work-over process,we choose the preventing water-block agent by evaluating the surface tension of the solution,temperature resistance and alt resistance.Then optimize the existing work-over fluid system.Formulating agents FP and FCJ add to flushing fluid,and it makes the permeability damage below 30% evaluated by core flow experiment.The optimized well killing fluid system has better thermal stability and the core damage rate is less than 20% after using it.We study the influence factors of the fluid-loss control fluid using orthogonal experiment,and consider that the thickener impacts greatest.The optimized fluid has good temperature resistance.It can plug effectively evaluated by sand bed fluid loss experiments.The average penetration depth is 8.5cm.Adding inhibitor A,B to calcium fluid can make the scale soft through chelation.There is no scale after adding the inhibitor F to the mixture of liquid calcium and sodium bicarbonate?5000mg/L?.Use the density functional method of quantum chemistry to calculate the hydrogen bond interaction and the length of the hydrogen bonds between OP-10,FC respectively and water molecules.Explore and explain the inner contact between the surface activity with the solution of preventing water blocking in theory.