Optimization Design Of Drilling Fluid Reservoir Protection In Shengli Oilfield

The damage of drilling fluid to oil and gas reservoirs in the construction process will directly affect the productivity of oil and gas wells,and even shorten the life of oil and gas wells.With the advancement of exploration and development in Shengli Oilfield,the number of deep wells,complex wells and special technology wells is increasing,and the requirements for drilling fluid and reservoir protection technology are also increasing gradually.However,at present,drilling fluid design mostly refers to near-well data,which is blind to some extent.Therefore,it is necessary to study reservoir damage mechanism and protection principle in key blocks of Shengli Oilfield,optimize the design scheme to meet the needs of reservoir protection,ensure engineering construction and reduce comprehensive costs.This paper combines theoretical analysis with experimental research to study the reservoir damage mechanism in the main new areas of Shengli Oilfield,optimize reservoir protection technology and improve drilling engineering design.Reservoir damage in Shengli Oilfield is mainly caused by solid invasion,clay hydration expansion and dispersive migration,adsorption of dispersive treatment agents,wellbore instability,incompatibility of foreign fluids and water lock.At present,there are mainly brine drilling fluids,positive gel drilling fluids,low solid drilling fluids,solid-free soilless drilling fluids and oil.There are some problems in drilling fluids,such as base drilling fluids and polymer drilling fluids,such as poor compatibility,large field usage and high cost proportion of reservoir protection materials used.For the moderately weak water sensitivity and salt sensitivity damage of reservoir in Chengbei 326 block,it is recommended to use polyols,non-permeable treatment agents and naturally degradable polymers to construct high-quality non-polluting seawater drilling fluid with permeability recovery rate of more than 90%.For the reservoir in Qingdong 12 block,the permeability recovery rate is weak water sensitivity,weak alkali sensitivity and strong acid sensitivity.The constructed seawater MEG drilling fluid reservoir has excellent protection performance;the reservoir in Shishen 100 block has strong water sensitivity,acid sensitivity and weak salt sensitivity,and adopts ideal filling and waterproof locking technology to maximize reservoir protection;Wang55 block is a low permeability layered lithologic reservoir with fast formation pressure attenuation and high drilling fluid density causing serious damage,so it is recommended to add more.Adding aminopolyol to inhibit clay expansion,adding double-film pressure-bearing agent to plug micro-cracks,reduce dynamic filtration,and using waterproof blocking agent to reduce interfacial tension and speed up back drainage have good reservoir protection effect.The permeability recovery value is more than 86%.Field tests and applications in Chengbei 326 block,Qingdong 12 block,Yong3 fault block,Shishen 100 block and Wang55 block have achieved good results and remarkable production.The effective combination of drilling fluid technology and reservoir protection technology in target block has been achieved,and the dual roles of improving production efficiency and reservoir protection have been achieved.