| Water injection is one important treatment way in increasing the production of sandstone reservoirs,the water injection wells often suffer from a series of reasons,such as solid particle blockage,particle migration,chemical blockage and so on,resulting in a decline in water absorption capacity.In order to solve the problems in the offshore injection wells like injecting pressure rises,injecting volume,acidizing radius and validity time decrease,acid quantity and reservoir heterogeneity enhanced after long-time injecting,online acidizing technology was proposed,which can effectively solve the problems of narrow space,cumbersome technology,long process time and difficult to implement.But it cannot be acidizing the formation homogenized and cannot improve the injection profile.The online diversion acidizing technology of water injection wells proposed in this paper is based on the online acidizing technology of offshore oilfields,the implementation of diversion acidizing was added.This technology is not only efficient and concise,but also can homogeneously acidize heterogeneous formations and prolong the effective acidizing time.This technology is not only efficient and concise,but also can acidizing heterogeneous formations uniformly and prolong the effective acidizing time without causing damages.In this paper,through theoretical and laboratory experiments,the mixing ratio of acid and water,the performance acid and diversion capacity are studied,the process parameters are optimized.The main research contents are as follows:(1)According to the geological data of H oilfield and the acidizing status of water injection wells,the source of formation damage is identified;the sensitivity factors are analyzed,and the performance requirements of acidizing fluid system are put forward by analyzing the problems of acidizing in the past.(2)An online acidizing acid system with good compatibility with formation water,low corrosively,good metal ion chelating and precipitation inhibition was designed.The acidizing plugging removal effect was verified by laboratory core acidizing flow test.(3)The mechanism of surfactant viscous change was studied,and the type of surfactant with good compatibility with acid system was selected from the diversion agents with different molecular structures,which met the online acidification conditions of H oilfield water injection wells,and the concentration and proportion of the diversion agent were optimized.(4)The parameters of online diversion acidizing technology were designed,and carry out online diversion acidizing for a water injection well.Through the analysis of the results,it can provide guidance for the follow-up implementation of the technology. |
