S115井承压堵漏及盐膏层钻井液技术

塔河油田古生界石炭系地层存在膏盐岩层，埋深为5175～5304m，厚度达130m。该膏盐岩层纯而且集中，钻井过程中极易发生溶解、膨胀、井眼缩径、井壁坍塌，造成起钻遇阻、下钻遇卡等现象。决定采用欠饱和盐水钻井液和配套的钻井技术措施。钻进盐膏层时，保持钻井液性能稳定，控制钻井液密度，以平衡地层压力，抑制盐膏层的蠕变；及时检测Cl^-含量，将Cl^-含量控制在160000～175000mg／L之间，保证适度溶解盐膏层井壁，防止缩径发生复杂情况；对于漏失层采用全井分段间隙式堵漏工艺，每次泵入量不宜太多，泵速不宜太高，按照“少量多次”的原则进行憋压。现场应用表明，该钻井液体系和配套的钻井技术措施，满足了盐膏层钻进，保证了盐膏层上部地层的稳定，井眼无坍塌现象，盐膏层钻进顺利，无阻卡现象，5次电测均一次到底，下套管、固井施工顺利。

Pressure bearing sealing technique and drilling fluid technology for S115 well

In Tahe oilfield, the presence of salt-gypsum bed of 130 m existing at depth of 5175-5304 m in the Carboniferous system of Palaeozonic. formation is a potential to solute and swell in drilling, which often cause accidents of hole shrinkage or well bore collapse. Undersaturated salt water drilling fluid and assorted drilling measures were decided to apply in the salt-gypsum section. Measures includes: 1) Keep the drilling fluid in stable property, control the density to balance the formation pressure, then to inhibit creep deformation; 2) Measure the Cl content in time, and condition it within 160000-175000 mg/L, to prevent problem of hole shrinkage; 3) Use step-by-step sealing technology in the thief zone, the volume injected should not be too much, and the rate of pumping should not be too high. Field using directed that the fluid and the assorted drilling measures fulfilled requirements of drilling in salt-gypsum section, the upper formation remained stable, and there were not problems appeared in drilling and subsequent operations.