Studies Of The Profile Control And Oil Displacement Technologies By Microbes After Polymer Flooding At Sabei Development Area

Aiming at the puzzle of enhanced oil recovery after polymer flooding at the heterogeneous reservoir, advanced theories and technologies were investigated at home and abroad on the tertiary oil recovery. In combination with the methods like lab experiments and numerical simulations, several bacterial strains were selected for profile control and oil displacement according to the reservoir properties of the Sabei development Area at Daqing oilfield. Based on the feasible microbial profile control proved by a pilot field test, a program for microbial profile control and oil displacement was optimized and predicted to provide a theoretical basis and a technological guide for its field application after polymer flooding.Through geological studies and fine reservoir description, the remaining oil distribution features was analyzed at the West of Bei-2 Block. The results show many new features as: the polymer flooding has made the reservoir physical properties change to different extents; a great amount of remaining oil exists under ground at the test block after polymer flooding but scatters a lot; the injected water cycles futilely with a big adjustment difficulty; the viscous finger goes severely with poor oil displacement effect because of the fact that less viscous fluid displaces high viscous fluid in the process of subsequent water injection after polymer flooding.From the produced water of Daqing oilfield and the waste water of companies, two excellent profile-control strains as TP-1 and TP-2 and five oil-displacement strains as SHB, MRI, P178, PHL and GWN were optimized by the processes of microbial separation, secondary screening and strain identification etc. The compatibilities of TP-1 and TP-2 with reservoir conditions were evaluated by the core plugging experiments and the fluid flow tests in heterogeneous cores. The results show that the compound formula of the two profile-control strains has good performance of profile control. They can plug the high permeable oil layers effectively to make the water intake conditions better between the low and high permeability layers, then to improve the oil recovery ratio. The mixture of the oil-displacement strains can grow and reproduce under conditions of polymer and crude oil with several metabolites as organic acid, active substance, can degrade the crude oil and polymer to decrease the paraffin content and can reduce the interfacial tension of oil-water to decrease the viscosity of the crude oil.According to the transportation mechanisms of the microbes, substrates and metabolites within the porous reservoir after polymer flooding, based on the traditional model, the bio-film formed by the residual polymer with the profile control microbes and the effect of the degradation of both crude oil and polymer on the enhanced oil recovery inside the reservoir were considered to build a three-dimensional, three phase and poly-component flowing mathematical model which includes the component migration equation, black-oil-type simulation model, microbial kinetics equation, permeability reduction model and the occluded oil activation model, all of which are capable of describing the microbial physical, chemical and biological processes occurring in the porous media. A software was also developed to model the enhanced oil recovery process by microbial profile control and oil displacement. The new software was used to predict the effect of microbial profile control and oil displacement, of which the results show that the microbial profile control and oil displacement is able to enhance the oil recovery ratio by 7.37% after polymer flooding at the test block with a big decrease of water cut.The pilot field test with strains TP-1 and TP-2 shows the feasibility of microbial profile control and oil displacement at the Putaohua oil layer.