新型高强度堵漏技术在沙南3井中的应用

Application of Mud Loss Control Techniques with High Strength Lost Circulation Materials on Well Shanan-3

沙南3井是位于塔里木盆地北部坳陷沙南构造带沙南3号构造高点的一口重点预探井,古近系库姆格列木群组发育多套复和膏盐岩层,由于盐层以上的地层存在多套低阻砂岩层(漏失压力系数不大于1.4),为保证下部盐膏层安全施工,需大幅度提高盐层以上大段低压层承压能力。通过室内实验优选出以"超强滞留颗粒"和"水化膨胀系列复合堵漏剂"为核心的新型堵漏材料,并优化出适合不同尺寸漏失通道堵漏浆配方,承压能力均达到15 MPa以上,抗返排能力超过5MPa。现场配合多级及多阶承压堵漏工艺,逐步将钻井液密度从1.40 g/cm^3提高到了1.75 g/cm^3,提高承压能力到19 MPa,保证了本井套管顺利下入。

The well Shanan-3 is a key exploratory well located at the No. Shanan-3 structural high in Shanan tectonic zone of the north sag in Tarim Basin. This well penetrated the Kumugeliemu Group of the Paleogene System in which multiple salt zones are developed. Above the salt zones there are multiple sandstones with low leak pressures(coefficient of leak pressure ≤ 1.4). To guarantee the safe drilling of the salt zones, the pressure-bearing capacity of these sandstones should be greatly enhanced. To control the mud losses in this hole section, a new mud loss control slurry was formulated with two core additives, one was a particle material with excellent detainability and the other, a compound lost circulation material which swells at hydration. The mud loss control slurry was optimized to make it adaptable to loss zones with different sizes of mud loss channels. Loss zones treated with the mud loss control slurry had pressure-bearing capacity of at least 15 MPa and resistance to the flow-back of the mud loss control slurry of at least 5 MPa. In field operations, mud loss control techniques of various kinds were used, the mud density was gradually increased from 1.4 g/cm^3 to 1.75 g/cm^3, and the pressure-bearing capacity was increased to 19 MPa, ensuring the smooth running of the casing string.