塔里木轮南奥陶系碳酸盐岩高压油气藏水平井及大斜度井欠平衡钻井技术

UNDER BALANCE PRESSURE DRILLING TECHNIQUES OF THE HORIZONTAL WELL AND HIGH ANGLE DEVIATED HOLE IN ORDOVICIAN CARBONATE ROCK HIGH PRESSURE RESERVOIRS IN LUNNAN REGION OF TALIMU BASIN

塔里木轮南地区碳酸盐岩裂缝性油气藏地层压力系数与地层破裂压力系数相近，钻井液安全密度窗口小于循环压耗，钻井过程中井漏和溢流经常同时发生，无法进行正常钻进和起下钻作业。针对喷漏共存以及碳酸盐岩不能实现稳产等难题，通过对解放１２８水平井和轮古２大斜度井的欠平衡钻井实践，总结分析了水平井、大斜度井欠平衡钻井的准备及其相关钻井技术。采用了环空打一个重“泥浆帽”，关井，钻具内用清水作为冷却液边漏边钻，顺利地完成了一口造斜点５０６０ｍ，斜深５７５０．３０ｍ（垂深５３４１．７３ｍ），水平段长２５９．４７ｍ的水平井；使用边喷边钻钻井工艺，成功地钻成了一口造斜点５１０２ｍ，斜深５５００ｍ（垂深５３６８．１３ｍ），水平位移２７７．２ｍ的大斜度井（井斜６６°）。利用“吊罐”起下钻技术，解决了井漏情况下的换钻头、测斜、中测、电测、完井等作业。

In the fractured carbonate reservoirs in Lunnan region of Talimu Basin, the formation pressure coefficient and formation fracture pressure coefficient are similar to each other, the safety density window of drilling fluid is less than the circulating pressure loss, in drilling the lost circulation and overflow often happen at the same time, thus obstructing the normal drilling and roundtrip. In accordance with some difficult problems as the coexistence of the well blowout and lost circulation and that the stable production couldn't be realized in carbonate reservoir, the preparation and relevant drilling techniques of under balance pressure drilling of the horizontal well and high angle deviated well are summarized and analyzed through the under balance pressure drilling practice in the horizontal well Jiefang 128 and high angle deviated well Lungu 2. A horizontal well with a kickoff point of 5060 m, an oblique depth of 5750.30 m (a vertical depth of 5341.73 m) and a horizontal section length of 259.47 m was smoothly drilled through applying the following measures as making a heavy 'mud cap' around the annular space, shut in well and losing circulation while drilling by use of water as the cooling liquid in the drill string and a high angle deviated well with a kickoff point of 5102 m, an oblique depth of 5500 m (a vertical depth of 5368.13 m), a horizontal displacement of 277.2 m and a diviation angle of 66 。 was successfully drilled by use of the technique of blowing out while drilling. Through applying 'Hanging Jar' roundtrip technique, all the works as changing bit, slope measurement, drillstem test, wireline well logging and well completion have been finished under lost circulation condition.