延川南深部煤层气井防漏堵漏技术

延川南区块深部煤层气资源丰富，但钻井过程中漏失严重。为了降低漏失发生频次及其造成的经济损失，保证该区块煤层气井安全高效成井，在分析该区块地质特征和漏失机理的基础上，研究形成了由随钻堵漏钻井液和承压堵漏工艺组成的煤层气井防漏堵漏技术。延川南区块上部地层孔隙发育，以孔隙型渗漏为主，采用加入5%复合堵漏材料的随钻堵漏钻井液进行防漏堵漏；下部地层天然裂缝发育，以裂缝性漏失为主，采用加入7%复合堵漏材料的随钻堵漏钻井液进行防漏堵漏；对于储层段等裂缝易扩展的地层，采用加入10%复合堵漏材料的随钻堵漏钻井液进行堵漏。针对煤层气井无防喷器或封井器无法实施承压堵漏的问题，研制了井口简易胶塞封隔器，形成了煤层气井承压堵漏工艺。延川南区块深部煤层气井应用防漏堵漏技术后，漏失率由41.53%降至23.07%，处理漏失的时间也大幅缩短。现场应用表明，煤层气井防漏堵漏技术可降低延川南区块深部煤层气井的漏失率，缩短钻井周期，降低钻井成本，提高该区块煤层气的开发效益。 

Antileaking and Lost Circulation Control Technology for Deep Coalbed Methane Well in the Yanchuannan Block

The Yanchuannan Block possesses rich deep coalbed methane resources but has serious lost circulation problems during the drilling process. In order to reduce the frequency of the occurrence of lost circulation, minimize the economic losses induced by lost circulation, and ensure the safe and efficient development of coalbed methane wells,we developed a anti-leaking and lost?circulation?control technology. Based on the analysis of the geological characteristics and the lost circulation mechanism, the new technology incorporated plugging-while-drilling fluids and pressure-bearing plugging process was proposed. In the Yanchuannan Block where the upper formations develop pores, pore-type lost circulation predominates, 5% composite plugging materials are added to the drilling fluid for?lost?circulation?control. The lower formations develop natural fractures, and are dominated by fracture-type lost circulation, accordingly 7% composite plugging materials are added to the plugging-while-drilling fluids for leakage prevention and plugging. For the formations where fractures can easily propagate, plugging-while-drilling fluids with 10% composite plugging materials were applied for plugging. In order to solve the problems that some coalbed methane wells have no blowout preventer or that the blowout preventer can’t perform pressure-bearing plugging, a packer with simple rubber plug at the wellhead was developed, which formed the pressure-bearing anti-leaking and lost?circulation?control technology for coalbed methane wells. After applying the technology to the deep coalbed methane wells in the Yanchuannan Block, the lost circulation rate was reduced from 41.53% to 23.07%, and the treatment time of lost circulation was also greatly shortened. The results also indicated that the proposed technology can lower the lost circulation rate of deep coalbed methane wells in the Yanchuannan Block, shorten drilling cycles, reduce the drilling cost, and improve the development benefits of coalbed methane in this block.