Geological Characteristics Of Reservoirs In Wenchang Formation In LF14-4 Oilfield And Research On Waterflooding Reservoir Protection Technology

In recent years,the low permeability reservoir is more and more become the mainstream of the development of oil and gas exploration,Lufeng 14-4 oilfield wenchang group reservoir which is located in the Zhujiangkou basin belongs to low porosity and low permeability reservoir.Restricted by offshore platform space and service life,synchronous waterflood means must be taken to the low permeability reservoir,implement high-efficiency mining to improve reservoir recovery factor,reduce development costs.Low permeability reservoir waterflood vulnerable to kinds of damage,and offshore oil field injection water is limited,thus deepening the research on reservoir geological characteristics,diagnosing the types of potential reservoir sensitivity damage,clarifying the damage mechanism of water injection process,and formulating reasonable reservoir protection technology in the process of water injection are the key problems to be solved.In this thesis,based on the literature research and the collection of the previous relevant results,the geological characteristics of the reservoir,such as the sensitivity of minerals and pore structure,were further studied by means of scanning electron microscopy and X-ray diffraction.Sensitivity experiment and fluid compatibility evaluation experiment were carried out to clarify the mechanism and type of reservoir damage in the process of water injection,and protective measures were put forward to provide technical support for the scientific and efficient development of such low-permeability offshore oilfields.The main reservoir of Wenchang formation in Lufeng 14-4 oilfield is fine?medium-grained lithic quartz sandstone,followed by feldspathic quartz sandstone.main in the clay cement,absolute content<7%,mainly illite and kaolinite.The Wenchang formation has an average porosity of 11.8%and an average permeability of 16.2mD,belonging to low?medium porosity and extremely low?low permeability reservoirs.The primary intergranular pores are dominant,followed by intergranular solution pores,mold holes and poor connectivity of pore throat.Flaky and curved flaky pore throat dominate.The results of sensitivity experiment show that the reservoirs in Wenchang formation have slight velocity sensitivity,weak?medium weak water sensitivity,weak?medium weak salt sensitivity,strong alkali sensitivity and weak?medium weak acid sensitivity.The critical salinity is 3300mg/L and the critical pH value is 8.0.Theoretical simulation and laboratory experimental evaluation showed that the injected water(formation water of Enping formation)and formation water of Wenchang formation were incompatible to a certain extent and easy to form carbonate scale.The injected water has a good adaptability with Wenchang formation,and a matching scale inhibitor is recommended to prevent the incompatibility between injected water and formation water from causing scale blockage on the reservoir pore throat,and the corresponding injection process parameters are recommended.