喷漏同存条件下堵漏压井技术——以四川盆地九龙山构造龙探1井为例

龙探1井在对四川盆地九龙山构造深部中二叠统栖霞组超高压气藏的钻进中,受井身结构的限制,同一裸眼井段内面临高温超高压复杂压力剖面,?190.5 mm井眼钻进至栖霞组发生溢流,在控压循环加重的情况下引起下喷上漏,如何安全处理成为该井能否顺利完成的关键。为此,在仔细分析龙探1井喷漏同存复杂情况和处理技术难点的基础上,确定出把上部漏层与下部高压气层进行隔离、提高漏层的承压能力以满足平衡钻井要求的处理技术思路,制定出GZD刚性颗粒+核桃壳+HHH堵漏配方的具体处理实施办法:(1)通过正、反推压井液将气体污染钻井液推回漏层,降低关井的井口压力,再采用隔离法注水泥封隔喷、漏地层,阻断井下内循环;(2)堵漏施工中采用井口压力升高的时间和堵漏浆的注入量推算出漏层大致位置,推测漏失通道的大小、漏层对堵浆的吸收能力等漏层性质,作为后续作业调整堵漏浆的粒度、浓度、使用量的依据。采取上述措施成功地将龙探1井上三叠统飞仙关组承压能力提高到2.35 g/cm~3并顺利钻穿栖霞组,下?168 mm套管固井。结论认为,适宜的堵漏配方能有效地扩大钻井液安全密度窗口,该实例可为该区及其他地区处理此类问题提供有益的经验。

Well killing and plugging technology under the coexistence of blowout and circulation loss: A case study on Well Longtan 1 in the Jiulongshan structure,Sichuan Basin

Due to the restriction of the casing program, Well Longtan 1 is faced with the following problems in the drilling of the ultra-high pressure gas reservoir of Permian Qixia Fm in the deep area of Jiulongshan structure of the Sichuan Basin. The complex pressure profile of high temperature and ultra-high pressure occurs in the same open hole section. Overflow happens when the Ø190.5 mm borehole drills into Qixia Fm. And blowout in the lower part and circulation loss in the upper part is induced with the increase of pressure control circulation. In this situation, the key to the successful completion of Well Longtan 1 is to deal with these difficulties. In this paper, the complex coexistence of blowout and circulation loss in Well Longtan 1 was analyzed and the difficulties related to treatment technologies were researched. Then, the technical idea of separating the upper thief zone from the lower high-pressure gas reservoir and increasing the bearing capacity of the thief zone to satisfy the drilling fluid density required by balanced drilling was figured out. In addition, the specific treatment measures of GZD rigid particles + walnut shells + HHH plugging formula were worked out as follows. First, drive the gas-contaminated drilling fluid back into the thief zone by impelling the kill fluid forward and backward so as to reduce the shut-in wellhead pressure. And then inject the cement by using the isolation method to plug blowout layer and thief zone and stop the downhole internal circulation. Second, the time for wellhead pressure rising and the injection amount of plugging slurry in the process of plugging are used to predict the approximate location of the thief zone and estimate the characteristics of the thief zone, e.g. the size of the leak channel and the absorption capacity of the thief zone to plugging slurry, so as to provide a basis for adjusting the size, concentration and usage of plugging slurry in the subsequent operations. With these measures, the bearing capacity of Well Longtan 1 in Feixianguan Fm was successfully increased to 2.35 g/cm3, and Qixia Fm was smoothly drilled and cementing was conducted by using the Ø168 mm casing. In conclusion, this appropriate plugging formula can effectively enlarge the safe density window of drilling fluid and provide useful experience for dealing with similar problems in this block and other areas.