Study On Drilling Fluid Technology For Protecting Oil And Gas Reservoirs In Tamysag Basin

The reservoir damage mechanism is the theoretical basis for protecting reservoirs,preventing and controlling damage.The essence of reservoir damage is the decrease of effective permeability.The decline in effective permeability includes a decrease in absolute permeability and a decrease in relative permeability.This article analyzes the internal and external causes of reservoir damage,and conducts damage experiments.Based on the results of the damage test,we conclude that the damage caused by the solid phase is small,and the main damage method is liquid phase damage.In the liquid phase damage,the water lock damage is the main cause.Protecting the reservoir should focus on reducing the liquid phase damage of the drilling fluid,and in particular controlling the quantity and properties of the drilling fluid filtrate that enters the reservoir.Through the core damage experiment,the influence law of water lock damage was obtained.The experimental data showed that the breakthrough pressure required for the fluid flow is high,indicating that if the water-based fluid is displaced or self-inhaled,it may appear obvious water lock effect,causing more serious water lock damage.Therefore,the prevention and release of water lock damage can not be ignored in the drilling fluid design.Gas reservoir sensitivity assessment usually includes five-sensitivity experiments such as quick-sensitive,water-sensitive,salt-sensitive,alkali-sensitive,and acid-sensitive tests.The experiments in this paper are performed according to the industry standard of “assessment procedures for sandstone reservoir core flow experiments”.The purpose is to find out the sensitive conditions of oil and gas reservoirs and the extent of oil and gas damage caused by the sensitivity,and provide scientific basis for the design of various working fluids,the analysis of the damage mechanism of oil and gas layers,and the development of a systematic oil and gas reservoir protection plan.Oil drilling is further for migration of oil and gas resources,but drilling fluids may cause reservior damage and impact the block production.This paper focuses on the analysis of the influence of drilling fluid system in the block of the reservoir,the final optimized drilling fluid system is suitable for the area,worthy of further promotion and application in the block.