Research On Damage Mechanism Of Low Permeable Reservoir In Jilin Qi′an Oilfield

With the increasing demand of oil and gas resource, exploitation of low porosity and permeability reservoir has been one of the important measures to increase oil and gas production. In this paper, according to the features of low porosity and permeability reservoir of Qi′an Block, we do the corresponding research of reservoir damage mechanism. Based on the experimental results, the values of porosity and permeability are very low. So the studied block belongs to poorly developed formation of low porosity and permeability. Yet we find that the absolute content of clay mineral is less than 5 percent. There is no trace of montmorillonite. In the sensitive study, we determine that the Heidimiao reservoir is medium to weak acid sensitivity, salt sensitivity and water sensitivity. While Gaotaizi reservoir is weak salt sensitivity, medium to weak speed sensitivity and weak water, acid and alkali sensitivity. The main damaged pattern is water block damage. The damaged rate of water block is between 10.71% and 15.38%.On the basis of experimental study, we establish a mathematical model to describe the filtrate invasion damage. By the mean of numerical simulation, we get the estimated permeability recovery values. Compared with the measured values, the error is less than 10%.According to the serious problem of water block, we optimized water block proof agent FHB-10. The optimized dosage was 2%. Finally, the drilling fluid system has been improved. The protection effect of this drilling fluid system was obvious. The permeability recovery value can reach 91.4%. It is a high quality drilling fluid with low penetration and low damage. Above all, it can effectively prevent water block damage to achieve the goal of reservoir protection.