The first member of Dongying formation is the main production reservoir of Nanpu 1-5 block in Jidong Oilfield located in northern Bohai Bay Basin, China. The formation was put into development as early as 2005, and it has entered late development stage. Formation characteristics changed constantly during the development by water flooding, formation damage mechanisms were not well understood, which resulted in the incompatibility of formation protection technology with the reservoir so that further formation damage happened. For wells newly putted into production, significantly lower production was obtained than the expected for years. Based on the measurement and comparison of formation characteristic, remaining oil distribution and damage mechanisms in early and late development stage, formation protection drilling fluid are conducted and optimized. The reservoir analysis results show that with constant development, pore-throat sizes decrease, heterogeneity intensify, and remaining oil is mostly trapped in the the low permeability strip, where water block damage rate is 10–29%, solid damage rate is about 10%, and the damage rate of liquid sensitivity is 5–10%. The synergy of broad-spectrum film-forming plugging and water blocking prevention was utilized to optimize formation protection drilling fluid system, the recovery value of the intercepted permeability recovered to more than 92%. Field application of the system on 17 wells showed an excellent formation protection effect, which meet the urgent formation protection needs of the late development of Nanpu 1-5 block. The technological ideas can be a valuable reference for other similar reservoir in China and around the world.

东营组一段是位于渤海湾盆地北部的冀东油田南堡1-5区块的主力生产油藏。该组早在2005年就已投入开发，目前已进入后期开发阶段。水驱开发过程中地层特征不断变化，地层破坏机理认识不清，导致地层保护技术与储层不兼容，进一步造成地层破坏。对于新投产的油井，产量明显低于多年来的预期。通过对开发前期和后期地层特征、剩余油分布和损伤机制的测量和比较，对地层保护钻井液进行优化。储层分析结果表明，随着不断开发，孔喉尺寸减小，非均质性加剧，剩余油多被困在低渗透带，水块破坏率10～29%，固体破坏率约10% , 液敏性损伤率为 5%~10%。利用广谱成膜封堵与防堵水的协同作用，优化地层保护钻井液体系，截获渗透率恢复值恢复到92%以上。该系统在17口井的现场应用显示出良好的地层保护效果，满足了南堡1-5区块后期开发的迫切地层保护需求。