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沁水盆地南部煤层气L型水平井排采技术研究及应用

Application of drainage technology for L-shaped coalbed methane horizontal well in Southern Qinshui Basin

  • 摘要: 随着L型水平井成为煤层气主要开发井型,传统煤层气井排采工艺不能满足需要,为了形成适用于L型水平井的排采工艺技术,基于沁水盆地南部马必合作区块L型水平井排采实践,分析了2类有杆排采工艺和3类无杆排采工艺的工作原理、工艺改进及其对L型水平井的适应性,并研究了相关防砂、防气配套工艺,形成了系统的水平井排采工艺。结果表明:① 2类有杆排采工艺通过管柱结构优化、泵结构优化等可以有效减轻杆管偏磨,能够适应L型水平井排采。抽油机+管式泵排采工艺通过优化管柱结构加装扶正器,能够减缓杆管偏磨,通过采用双固定阀长柱塞管式泵能够提升固体颗粒适应性;顶驱螺杆泵排采工艺通过在管柱结构不同部位差异化安装弹簧式扶正器,采用加厚油管,并在狗腿度大的位置加装导向器和双保接箍,能够减轻杆管偏磨。② 无杆管式泵、射流泵、电潜螺杆泵等无杆工艺从本质上消除了杆管偏磨问题,对L型水平井适应性更强,射流泵对固体颗的粒适应性最强,电潜螺杆泵的排量可达50~60 m3/d,无杆管式泵排量一般在20~30 m3/d,射流泵的排量一般在30~40 m3/d。③ 提出的分级下泵、气液分离及循环洗井3项配套工艺,能够有效防砂、防气,提升了主体工艺的适应性。其中,分级下泵工艺即在排采前期将泵挂位置设计在井斜65°~75°处,保留足够的沉砂空间,在排采后期,出砂量减少时,进一步下放管柱,充分释放单井产能;循环洗井工艺即在排采后期,通过循环洗井增加产出液体排量,提升携砂能力;重力分离式气锚可有效实现气液分离,减缓窜气对泵效影响。上述工艺技术在研究区应用后,能够满足埋深1 500 m中深层煤层气水平井的排采需求,L型水平井平均检泵周期由265 d延长至335 d,投产第1年检泵率由29.9%下降至19.8%,实现了L型水平井平稳高效排采。

     

    Abstract: As L-shaped horizontal wells have become the main well type for Coalbed Methane (CBM) development, the traditional CBM wells’ drainage technologies can no longer meet the drainage requirements. In order to develop a series of drainage technologies applicable to L-shaped horizontal wells, this article, based on the drainage practices of L-shaped horizontal wells in the Mabi Cooperative Block in Southern Qinshui Basin, analyzes the working principles, process improvements, and technological adaptability to L-shaped horizontal wells of two types of rod-pumping drainage technologies and three types of rodless-pumping drainage technologies. It also studies the relevant supporting processes for sand control and gas prevention, and forms a systematic horizontal well production technology. The results show that: ① Through the optimization of the string structure and the pump structure, the eccentric wear between the rods and the pipes of the two types of rod-pumping drainage technologies can be effectively reduced, which can adapt to the drainage of L-shaped horizontal wells. For the oil pumping unit process, the eccentric wear can be alleviated by installing centralizers optimize the string structure and using a long plunger tubing pump with double fixed valves to improve the adaptability to solid particles. For the top drive screw pump process, by installing spring centralizers differently at different parts of the string structure, using thickened tubing, and installing a deflector and double protect collars at the positions with large dogleg degrees, the eccentric wear can be reduced. ② Rodless processes such as rodless tubing pumps, jet pumps, and electric submersible screw pumps essentially eliminate the problem of eccentric wear between the rods and the pipes, and have a much stronger adaptability to L-shaped horizontal wells than rod-pumping drainage technologies. Jet pumps have the strongest adaptability to solid particles. The maximum displacement of electric submersible screw pumps can reach 50−60 m3/d, the maximum displacement of rodless tubing pumps is generally 20−30 m3/d, and the maximum displacement of jet pumps is generally 30−40 m3/d. ③ The three supporting processes proposed in this article, namely, the graded pump setting process, gas-liquid separation process, and circulating well cleaning process, can effectively reduce the influence from sand particles and CBM gas, and improve the adaptability of the main processes. Among them, the graded pump setting process is that the pump setting position is designed at the well deviation of 65°−75°in the early stage of production to reserve sufficient sand settling space,while the pump setting position is further lowered to fully release the productivity of a single well,in the later stage of production, when the sand production decreases.The circulating well cleaning process improves the sand carrying capacity by injecting water to increase the production rate in the later stage of production. The gravity separation gas anchor can effectively realize gas-liquid separation and reduce the impact of gas channeling on the pump efficiency. After the above process technologies are applied in the study area, they can meet the production requirements of horizontal CBM wells in the middle-deep layer with a burial depth of 1500 m. The average pump inspection cycle of L-shaped horizontal wells has been extended from 265 days to 335 days, and the pump inspection rate in the first year of production has decreased from 29.9% to 19.8%, achieving stable and efficient production of L-shaped horizontal wells.

     

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