低压低渗煤层气多分支水平井开发关键技术研究——以沁水盆地郑庄区块15号煤层为例

Research on key technologies for developing multi-branched horizontal of CBM wells in low pressure and low permeability coal reservoirs

摘要:

沁水盆地太原组15号煤层总体低压低渗低饱和，煤储层相对较薄，地质条件复杂，煤层气井产量普遍偏低。以沁水盆地郑庄区块为研究对象，依据本区15号煤层LDP-22H多分支水平井的成功开发经验，全面论述低压低渗煤储层煤层气钻完井工艺、标志层判定、井眼轨迹控制等关键技术。结果表明：采用钻井-录井-测井一体化地质导向技术可以有效卡准目的煤层，同时实时修正钻头轨迹，煤层平均钻遇率在97%以上，极大地提升了煤层有效进尺。865 d的排采实践表明，LDP-22H多分支水平井日产气量突破15万m3，日产气量稳定在8万m3左右，全程累计产气量为2091.5469.3 万m3，实现了超高产和稳产，标志着多分支水平井在低压低渗煤储层煤层气高效开发上有较好的适用性。另一方面，多分支水平井要优化井位，加强水平井底部位排采能力，稳定压降速率，减小对煤储层渗透率敏感性伤害，提高排采的连续性，减少停泵和检修作业频次，保证产能的延续性。

Abstract:

The No.15 coal bed of Taiyuan Formation in Qinshui Basin is generally feathured with low-pressure， low-permeability and low-saturation. The coal reservoir is relatively thin with complex geological conditions， and the coal bed methane （CBM） production is commonly low. Taken the Zhengzhuang Block in Qinshui Basin as the example， the key technology of CBM drilling and completion technology， marker formation determination， and well trajectory control in low pressure and low permeability coal reservoir are discussed comprehensively based on the successful experience of the LDP-22H multi-branch horizontal well in No.15 coal bed.The results show that the integrated geosteering technology of drilling and logging can effectively fix the target coal bed and modify the bit track in real time， which can improve the average drilling rate to above 97% and greatly improve the effective footage. The 865-day drainage and production practice shows that the daily gas production of the LDP-22H multi branch horizontal well has exceeded 150，000 m³， the current daily gas production is stable at about 80，000 m³， and the total cumulative gas production is 20915469.3 m³， achieving ultra-high and stable production， which marks good applicability of the multi branch horizontal well in the efficient development of CBM in low-pressure and low-permeability coal reservoirs. Moreover， it is necessary to optimize the well position， strengthen the drainage and production capacity at the bottom of the horizontal well， stabilize the pressure drop rate， reduce the sensitivity damage to the permeability of the coal reservoir， improve the continuity of drainage and production， reduce pump downtime and the frequency of maintenance operations， and ensure the continuity of production capacity.