空气、氮气钻井技术在普光气田的应用

川东北普光气田上部陆相地层岩石硬度级别为硬到极硬，可钻性级值总平均约在6级；地层倾角大，介于30°～75°之间，井身质量控制困难；裂缝发育，易漏且漏失井段长。为此，在普光气田推广应用了空气、氮气钻井技术，目前已实施完成9口井，正在实施的有11口井。与使用常规钻井液的钻井工艺相比，第一次开钻平均机械钻速达到7.7 m/h，是使用常规钻井液钻井的2.6倍，钻井周期缩短10～20 d；第二次开钻平均机械钻速达到12.7 m/h，是使用常规钻井液钻井的8倍，钻井周期缩短60～90 d；同时，空气、氮气钻井技术在该气田解决防斜打直、减少地层漏失等问题方面也取得了重大突破。

AIR & NITROGEN DRILLING TECHNIQUES USED IN PUGUANG GASFIELD

The rock hardness of the upper terrestrial formation in the Puguang Gasfield is from the large to the largest, with its average drillability value of about Grade Ⅵ, the angle of strata dip as high as up to 30-50°. In addition to the susceptible circulation loss resulting from well developed fractures, well drillings here have obviously great difficulty in controlling the wellbore quality. After air and gas drilling was adopted here for more than one year, 9 wells have been successfully completed and another 11 wells under drilling at present. After comparing between the drilling by air and gas and the previous drilling by conventional drilling slurry, this study found that when using air and gas drilling at the first drilling section, the ROP reached up to 7.7 m/h, 2.6 times of that by the previous drilling, and the drilling cycle was shortened by 10-20 d; at the second drilling section, the ROP was 12.7 m/h, 8 times of that by the previous drilling, and the drilling cycle was cut down by 60-90 d. Through summarizing many successful practices for air and gas drilling in the Puguang Gasfield, this paper put forward that this drilling technique have made great breakthrough in many issues like how to drill directional wells against their deviation, how to avoid the circulation loss, and so on.