ZYSD高失水固结堵漏技术在顺北5-9井中的应用

Control Mud Losses in Well Shunbei-5-9 with ZYSD High Fluid Loss Solidifying Slurry

顺北5-9井是位于顺托果勒低隆北缘构造重点区域的一口评价井,该井志留系地层承压能力低,诱导性裂缝发育,受激动压力极易开启、扩展致漏,而桥塞堵漏粒径级配困难大,承压能力不足,此外志留系有发育高压盐水层,也增加了堵漏难度。邻井多口井发生严重复杂漏失、井壁失稳卡钻甚至弃井。针对志留系堵漏一次成功率低、地层承压能力低、井漏时效高等问题,采用ZYSD高失水固结堵漏技术,封堵时间小于30 s,承压能力大于18 MPa。现场应用表明,ZYSD高失水固结堵漏7次,堵漏一次成功率100%,井漏处理时间较邻井减少81%;现场试压8.5 MPa,志留系当量密度达到1.51 g/cm^(3),成功解决了顺北5-9井的井漏、出水等复杂问题。

The Well Shunbei-5-9 is an appraisal well drilled in the potential area of the low uplift Shuntuoguole north margin.The Silurian system penetrated by this well has low pressure bearing capacity and plenty of induced fractures which are easy to widen and extend when pressure surge is applied,and mud losses are thus occurring.When using bridging lost circulation materials(LCM)to control mud losses,it is difficult to have suitable particle size distribution of the LCMs,and the LCMs deposited on the surface of the wellbore has pressure bearing capacity that is not sufficient to resist mud losses again.Furthermore,there are high pressure saltwater zones developed in the Silurian system,making the mud loss control more difficult.Several wells drilled nearby experienced severe mud losses,borehole wall collapse and even well abandonment.To overcome the difficulties encountered in controlling mud losses in the Silurian system,a ZYSD high fluid loss LCM was used.ZYSD is able to seal off the mud loss channels in 30 s,and the formation plugged with ZYSD has pressure bearing capacity of at least 18 MPa.This technique has been used 7 times in field operation and were all successful.Time spent dealing with mud losses was reduced by 81%.Mud loss zones treated with ZYSD had pressure bearing capacity of 8.5 MPa.Equivalent circulation density of mud when drilled into the Silurian system was 1.51 g/cm^(3).The application of the ZYSD technique successfully solved mud losses and water kick problems encountered in drilling the Well Shunbei-5-9.