Study On The High Efficient Acidizing Technology Of Heterogeneous Sandstone Resevoirs In Offshore Oil Field

The exploitation characteristics and requirements of offshore oil fields are safe,fast,economical and efficient.Acidizing technology is a powerful technique to realize efficient exploitation and increase production greatly.The reservoir damage types of MM oilfield are complicated by drilling,completing and injection production process since its great non-homogeneity and sensitivity.Although the conventional acidification technology is effective,it still faces many problems in the implementation process under the special environmental conditions at sea.For example,homogeneous acidification of non-homogeneous reservoir in multi-layer of long well segment;complex implementation process;high cost and difficult rearrange of acidizing return fluid and so on.In this paper,the non-homogeneous sandstone reservoir in MM oilfield is studied as object to research on the technology and countermeasures of high efficient acidification of oil wells,water injection wells,implementation process methods and rearrange of acidizing return fluid,so as to form an effective acidification technology of marine heterogeneous sandstone reservoir and support the efficient efficient exploitation of offshore oilfields.(1)From the perspective of efficient acidification,the reservoir rock,micro pore throat structure,reservoir property,fluid property,potential damage factors and the degree of mineral sensitivity are analyzed emphatically,which lays a foundation for the acidizing process and the selection of acid system.(2)The original production string acidizing technology is put forward according to the characteristics of offshore oil well.The efficiency of acid solution,uniformly distribute of diversion acid,corrosion mechanism of original production string and residual acid treatment were studied.A new type of chelating acid system is designed by analyzing the mechanism of chemical bond and coordination,which not only has low damage,but also inhibits the secondary damage,and is an environmentally friendly acid system.A compound organic reliever(SA-AD)was designed to remove both inorganic matter and organic matter,the acidification of oil well can achieve more efficient acid solution blocking action.A new viscoelastic Gemini surfactants to acid system which is suitable for sandstone reservoir was developed to effectively resolve the key problems of the heterogeneity of sandstone reservoirs.A simulation method was established to optimize the parameters of diversion acidizing.Results of experiment suggested that corrosion inhibitor is the key to reduce the acid corrosion of tubing string,and the equipment corrosion caused by original production string acidizing occurs mainly at the beginning of the residual acid.(3)The main reason for the serious emulsification of oil and water is due to the stability of emulsion caused by iron ion and surfactant.Targeted research and development of the iron chelating agent was implemented.The iron chelating agent was injected with chemical into pipeline to acidizing wells,and then chelating with ferrous ion to decrease the ferrous ions content in residual fluid,so as to reduce the formation of emulsion.(4)The treatment process of acid return drainage of neutralization,demulsification and oxidative coagulation filtration is put forward.According to the single well acidizing fracturing liquid treatment scheme,the acidizing residual liquid treatment device is designed and manufactured by "physical + chemical" technology,based on the properties of the oil weli's residual fluid and the existing process and facilities of oil production platform.The impact of residual acid on the production process is greatly reduced,and a breakthrough has been made in dealing with residual acid problems in acidizing operations in oil wells.(5)In view of the characteristics of offshore operation,this paper proposed an single step online acidizing technology,developed a new acid system with high efficiency and low damage for single step acid solution to replace the conventional complex "preflush?treatment solution?post-solution liquid?displacement fluid"four-step acid system,and developed an on-line acidification optimization and monitoring software.By recording pumping pressure and injection displacement in real time,it can realize the effect of acidizing real-time monitoring and automatic adjustment of construction parameters,besides,it can realize on-line,fast,efficient and large-scale acidification of offshore injection wells,and can realize acidizing such as variable concentration,variable volume and so on,and ensures the best acidizing effect.The research results of this paper have contributed to the significant progress and development of the oil production in offshore oilfields.The research results have been applied in MM oil field successfully in water injection and oil wells with high efficiency.It ensures the rapid and efficient exploitation of oil field provides effective technical guarantee for the stable production of Bohai oilfield.The results of this paper can provide useful reference for oil stimulation in similar fields.