BZ34-2EP-P1S井钻井液技术

BZ 34-2EP-P1S drilling fluid technology.

BZ 34-2EP-P1S井是对BZ34-2-P1井进行侧钻的一口调整井,以提高油井利用率及油田储量动用程度,预计侧钻后该井产能可达100 m3/d。该井主要钻井技术难点在于井壁易于失稳,而且井较深,需要在相对高的钻井液密度下进行油气层保护。该区块构造应力大,井眼力学不稳定的因素明显,井壁失稳属于硬脆性页岩的剥落坍塌。由于受构造应力的作用,地层坍塌压力系数较大,为1.30~1.40,破裂压力系数检测值为1.8~2.0,最小水平主应力当量钻井液密度最小为1.60 g/cm3。经过大量的前期研究和现场调整,优选了PEM钻井液。该体系是在常规的PF-PLUS聚合物体系中引入JLX水基防塌润滑剂和经过化学改性的具有类硅酸盐结构的高温防塌剂WLD配制而成的,具有良好的润滑性能;能有效抑制钻屑的分散和造浆,防止井壁坍塌,保证井眼稳定和井下安全;具有保护油气层、环境安全的特点,无油类和重金属盐类,可以直接排放。其抑制防塌机理为体系中各种处理剂的协同作用,在钻进中必须保证PF-PLUS、PF-JLX-C、KCl、PF-TEX和PF-WLD在钻井液中有足够的加量。采用该钻井液及屏蔽暂堵和成膜油层保护技术,成功完成了BZ34-2-P1S调整井的钻井作业,侧钻后该井获得了较高的产量。讨论了PEM钻井液的作用机理,分析了井壁失稳的原因及其控制措施,对该区块今后作业提出了建议。

In BZ34-2 field,the accumulative oil production has been 371.7×10~4 m^3,recover percent of reserves has been 10.6%,combined water cut has been 22.1% by July,2002.There are many disadvantages if the oil field will be produced continually.In order to solve these problems and improve oil output,it was decided to put the well stimulation into effect by drilling sidetracking in well BZ34-2-P1 which expect to attain 100 m^3/d output after stimulation.In the area,the formation with larger structural stress and hardly brittle core easily occurs sloughing,the mechanic factor affecting borehole stability is obvious,severe sloughing has ever happened in previous exploration and development.So it is difficult to drill,and to protect the reservoir drilled with high density fluid.PEM drilling fluid has been chosen on the basis of lots of early studies and fluid adjusting.The system is formulated by adding low molecular weight polyglycol surfactant,JLX,high temperatureresisting anti-sloughing agent modified which structure is similar to silicate,WLD,into conventional polymer drilling fluid,PF-PLUS.Its inhibitive mechanism is coordinated action of all additives in fluid.During drilling,the dosage of PF-PLUS、PF-JLX-C、KCl、PF-TEX and PF-WLD must be enough.The adjustment well BZ34-2-P1S has been finished by using PEM drilling fluid,shield-temporary plugging and membrane protecting reservoir technology,and it gained higher output after its sidetracking.Moreover,this paper discussed the mechanism of the PEM drilling fluid,analyzed the factors affecting and controlling wellbore stability,and provided suggestion for future operation in this area.