Research on Biologic Completion Fluid and It’s Application in Low Permeability Oil Gas Fields

Filter cake blockage is an main factor influencing oil well production in horizontal wells with non-perforation completion,and degrading polymer with biologic enzyme is a major way to clear filter cake.The kind and concentration of enzyme were defined through lab experiment.At the same time,the influence of pH on enzyme degrading course was investigated,and the mechanism of biologic enzyme degrading polymer was analyzed.Hydrophobic association polymer AX-1 was selected as the viscofier of biologic completion fluid,and its formula was formed through orthogonal experiment.Reduced rate of viscosity,filter cake soaking and formation protection tests were conducted for the fluid.Experiment results show that the biologic completion fluid clears filter cake well and recovery of permeability is over 85%,which result in good reservoir protection.Field application in Shengli Oilfield and Daniudi Gas Field shows that the biologic completion fluid can remove plugging effectively and enhance production significantly in low permeability reservoirs.For different drilling fluids,appropriate biologic enzyme can clear filer cake effectively and improve formation damage control.