莺-琼盆地新型高温高压水基钻井液技术

The Development and Application of High Performance Water Base Muds for HTHP Wells in Yingqiong Basin

位于南海西部的莺歌海-琼东南盆地(下称:莺-琼盆地)具有井底压力与温度双高、安全作业密度窗口极窄等特点,在高温高压工况下引发钻井液流变性难以控制、井下恶性漏失、电测仪器阻卡和储层保护难度大等情况.因此,基于此区块复杂的地质条件,经过多次的室内试验研究,在常规聚磺高温高压水基钻井液的基础上,通过引入甲酸钾作为配方抑制剂,同时优选抗高温聚合物以及磺化钻井液材料,在提高了体系的抑制性同时,有效地降低了钻井液的活度,并且通过加重材料的优选,钻井液的流变性得到了改善,使得体系具有较低的高温高压滤失量,密度2.5 g/cm3的体系可以抗高温达240℃.现场实践表明,新型高温高压水基钻井液体系具有良好的抗高温性和流变性,较低的高温高压滤失量,优良的滤饼质量,同时根据电缆测井井壁取心结果,此新型水基钻井液体系的储层保护效果良好.

High temperature and high pressure deep wells drilled in Yinggehai penetrated formations with narrow density windows.Conventional polymer sulfonate drilling fluids become highly viscous and difficult to flow in complex geological environment,and false thick mud cakes are generated.These generally result in resistance to drill pipe tripping,pipe sticking and lost circulation.A high performance water base drilling fluid has been formulated in laboratory with new high temperature polymers replacing conventional polymers.Laboratory evaluation shows that the high performance water base drilling fluid with density 2.50 g/cm3 maintained its thermal stability for a long time at 240℃,was resistant to the contamination caused by 50 g/L drilled cuttings,50 mL/L formation water and 5 g/L CO2,and performed well in reservoir protection,the return permeability reaches 84.6%.This high performance drilling fluid has been used on a well in Yinggehai with formation pressure coefficient of 2.20~2.40 and formation temperature between 190℃and 200℃,which conventional polymer sulfonate drilling fluid has failed the drilling operation previously.This proved that the high performance water base drilling fluid had good high temperature stability and superior rheology.The successful application of the high performance drilling fluid has provided an reference for selecting drilling fluids for HTHP complex well drilling.