化学凝胶堵剂承压堵漏技术在顺北3井的应用

顺北3井是位于塔里木盆地顺托果勒低隆北缘构造的一口勘探井，该井二叠系火成岩裂缝发育，地层胶结差、易破碎，承压能力弱，钻井时发生6次井漏，先后使用桥浆、水泥浆等堵漏方式，堵漏效果不佳，一次堵漏成功率低。针对二叠系地层承压能力弱等问题，通过复配使用多种特殊纳米级堵漏材料，研制出一种化学凝胶堵剂HND-1。通过机理分析可知，HND-1具有"多元协同封堵"作用，能够大幅地提高地层的承压能力。室内性能评价结果表明，用HND-1配制的化学凝胶堵漏浆的稠化时间在4~20 h内可调，24 h的抗压强度可达12 MPa以上，密度在0.8~2.25 g/cm3内可调，与其他外加剂的配伍性能好。HND-1化学凝胶堵漏浆在顺北3井二叠系裂缝性漏层进行了现场试验，承压效果良好，现场试压5 MPa，30 min压降为0.2 MPa，二叠系当量密度达到1.55 g/cm3，满足了二叠系承压能力的要求。 

Application of Chemical Gel LCM on Well Shunbei-3

Well Shunbei-3 is an exploration well located on the north rim of the Shuntuoguole low uplift in Tarim Basin, Xinjiang. This well penetrated the Permian system igneous rocks which have developed fractures, poor cementation, easy-to-break zones and low pressure bearing capacity. Six times of lost circulation during drilling were dealt with bridging agent lost circulation material (LCM) and cement slurry, and the results were unsatisfactory because of low success rate of the first try in lost circulation control. To resolve the lost circulation problem taking place in the low pressure bearing capacity formation of the Permian system, a chemical gel LCM, HND-1, was developed with several nanophase LCMs. Analyses of the mechanisms of HMD-1 indicated that HND-1 had the ability of controlling lost circulation through "synergism" of multiple LCMs, and it can substantially enhance the pressure bearing capacity of formation. Laboratory evaluation demonstrated that chemical gel LCM slurry formulated with HND-1 had thickening time adjustable between 4 h and 20 h, and the compressive strength of the LCM slurry after 24 h was 12 MPa or higher. The HND-1 LCM slurry had density adjustable between 0.8 g/cm3 and 2.25 g/cm3, and was compatible with other drilling fluid additives. The HND-1 LCM slurry was tried in the controlling of lost circulation occurred in the Permian system penetrated by the well Shunbei-3, and good results were obtained. The thief zones were pressurized at 5 MPa, with pressure drop of only 0.2 MPa in 30 min. The equivalent density of the Permian system reached 1.55 g/cm3, satisfying the density requirement for drilling in the Permian system.