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

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.