巴什二井钻井液堵漏技术

巴什二井是位于塔里木油田山前构造的一口探井，完钻井深3587m。巴什二井下第三系上部地层的复合膏盐层易发生蠕变，缩经，坍塌和软泥岩膨胀，下部地层的砂砾岩和白恶系地层的细砂岩，易发生渗透性漏失，针对漏失性质，采用了不同的堵漏方法，即：对漏速小于5m^3/h的井漏采用随钻堵漏；钻遇砂砾岩、砂酸盐岩地层发生漏速较大的井漏时，采取静止堵漏法；当随钻堵漏和静止堵漏失败后，说明地层存在裂缝，溶洞或压差过大，采用桥接堵漏法，采取的防漏措施有，当确定同裸眼井段内存在若干套压力系数时，要提前下套管封住上部高压地层，再降低钻井液密度钻开下部低压地层，专层专打；钻进易漏地层时，简化钻具结构，用小排量钻过漏层，再恢复正常钻进；下钻时分段循环钻井液，减小环空流动阻力；严禁在漏层附近开泵或划眼。巴什二井采用这套堵漏方法和堵漏措施后，顺利钻穿复杂地层，完钻施工顺利。

Approaches of well lost circulation controlling in well Bashi- 2

Well Bashi-2 is an exploratory well in the piedmont structure of Tarim oilfield, with its TD at 3587 m. The upper formation of the Lower Teriary is consisted of complex gypsiferous salt bed,. and such troubles as creeping, hole filling, sloughing and swelling of the soft mudstone occur frequently. Moreover, permeable lost circulation takes place in the lower formation of the Lower Teriary, which is consisted of gluti-nite and fine sandstone. Different approaches were adopted in accordance with the different lost circulation conditions, e.g. . plugging while drilling methodwas used when the lost rate was lower than 5 m3/h; and when penetrated into the glutinite and carbonate formation, where serious lost circulation was encountered, static plugging method was adopted; if both the plugging while drilling method and the static plugging method failed, then bridging plugging method would be used as there may exist fractures, cavities or large pressure differential. Many preventing methods were also taken, such as casing and isolating the upper high-pressured formation when there were several differential pressure gradients in the same open hole, and then drilling the lower low-pressured formation with lighter drilling fluids. Simplifying the BHA and using low pump rate when drilling through the lost circulation zones, and resuming drilling after passing it. Circulating interval by interval to minimize the annular flowing resistance, and no pump starting and whipping near the location of lost circulation. By adopting these plugging methods in well Bashi-2, the lost circulation zones were smoothly drilled through and it was drilled to the bottom successfully.