The Study Of Reducing Injection Water Pressure And Improving Injection Capacity Technology In High Pressure Water Injection Block Of Tahe Fracture-vuggy Reservoir

The fracture-vuggy reservoirs play an important role in the world's oil and gas resources.According to statistics,more than one-third of the carbonate reservoirs in the world are cracked caverns.Such reservoirs are highly heterogeneous,with complex fluid distribution,and the multi-dimensionality and connectivity diversity of the fracture holes make difficulties for development.In recent years,with the continuous exploitation of Tahe Oilfield,the understanding of the development of fracture-vuggy reservoirs has deepened.Tahe Oilfield is located at the junction of Luntai County and Kuche County in Xinjiang Uygur Autonomous Region.It is formed by multi-phase tectonic movement and weathered karst dominated by limestone karst.The main reservoir spaces of Tahe fracture-cavity carbonate reservoir are large caves,dissolved pores and cracks.Due to the complex and diverse sedimentary environment,early accumulation time,large burial depth,and multiple tectonic evolutions in the later stage,the spatial distribution of the reservoir has discontinuous and highly discrete characteristics,and the heterogeneity is extremely strong.Since 2005,Tahe Oilfield has achieved good results in high-pressure water injection development in some multi-well seam units.However,after long-term highpressure water injection,the water injection pressure is gradually increased,and the water injection volume is continuously decreasing.If further pressurized water injection is required,it will be affected by the ground equipment and the wellbore tubular process flow.Therefore,it is necessary to carry out research on the pressure reduction and water injection technology.Based on the current situation of high-pressure water injection in Tahe oilfield and the geological characteristics of fractured-vuggy reservoir in Tahe oilfield,this paper analyzes the causes of high pressure in water injection wells through on-site data analysis,physical simulation,numerical simulation and engineering calculation,determines the standard of pressure reduction and well selection,and adopts corresponding pressure reduction measures for the selected high-pressure water injection wells,which provides guidance for improving the water injection efficiency of the oilfield,increasing the controlled reserves of water flooding and the degree of production.