Characteristics and development practice of deep coalbed methane reservoir in southern Ningwu Basin
JIA Huimin
HU Qiujia
ZHANG Cong
LI Kexin
HE Shan
SANG Guangjie
LI Jun
LIU Chunchun
Abstract：To clarify the reservoir characteristics and development potential of deep coalbed methane reservoir in the southern Ningwu Basin,this paper takes coal seam No.9 in Ningwu-nan Block in southern Ningwu Basin as the research object.Based on the coring test data,well logging and fracturing data,and production data of evaluation wells in Ningwunan Block,by conducting a comparison of key reservoir parameters under the same burial depth with south-ern Qinshui Basin and the eastern edge of the Ordos Basin,the typical characteristics of deep coalbed methane reservoir in the study area were defined,and the formation mechanism of the reservoir characteristics was explained based on the burial history and thermal evolution histo-ry of the study area.Finally,the development countermeasures for deep coalbed methane in the study area were put forward based on the field development practices.The results show that compared with the southern Qinshui Basin and the eastern margin of Ordos Basin,the study area has the reservoir characteristics of low degree of thermal evolution(Ro,max with an average value of only 1.10％),low gas contents,low gas saturation,a low reservoir tempera-ture gradient(DT with an average value of 1.51 ℃/hm,which is only about 1/2 of the eastern margin of the Ordos Basin)and strong hydrodynamic conditions(the daily water volume rea-ches 40-450 m3 or more).The study area has a low paleothermal gradient and experienced a large uplift in the early to middle stage of Yanshan movement,resulting in a relatively low de-gree of thermal evolution,which further leads to a relatively low quantity of hydrocarbon gen-eration.So the pore which the gas was injected in has a relatively large radius,leading to weak reservoir self-sealing ability.What's more,combined with the strong hydrodynamic condi-tions,a large amount of gas has dissipated,resulting in a relatively low gas contents in the study area.The low present geothermal gradient and the gas contents result in a relatively low gas saturation.Because of the formation characteristics of the study area,it is much more dif-ficult to develop deep coalbed methane than the eastern margin of Ordos Basin.The field pilots indicate that the development adaptability of vertical wells is poor,and the multi-stage and multi-cluster fracturing of horizontal wells is expected to achieve beneficial development.The main problem is that the water production of a single well is up to 450 m2/d,and the effective de-pressurization of the reservoir pressure is much more difficult.So it is necessary to further op-timize drilling and fracturing parameters to control the water production capacity and depres-surize the reservoir pressure to the most.
Keywords：southern Ningwu Basindeep coalbed methanereservoir characteristicsdevelop-ment performance
Publication Date：2025-01-29
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：13( 149-160,185 )