二连盆地吉尔嘎朗图凹陷煤层气储层特征及勘探潜力

Characteristics of CBM reservoirs and exploration potential in Jiergalangtu sag of Erlian basin

通过分析二连盆地吉尔嘎朗图凹陷煤层的煤厚分布、煤岩煤质、孔隙、等温吸附等特征,并从生气条件和保存条件方面分析其勘探潜力。结果表明,吉尔嘎朗图凹陷煤层厚度10~394 m,显微煤岩组分以腐植组为主(体积分数为80.5%~96.7%),为低煤级褐煤;煤层Langmuir体积为3.55~10.88 m^3/t,平均7.29 m^3/t;煤孔隙结构以微孔和小孔为主,孔隙形态多为开放型的圆筒孔或平板孔,这类孔隙结构对煤层气的吸附能力强,煤层气含量为0.97~3.83 m^3/t,平均2.08 m^3/t。综合以上分析认为,研究区东南部为下一步煤层气勘探目标区,其优势特征为:煤层离正断层较远,煤层气不易散失;煤层顶板岩性以泥岩和粉砂质泥岩为主,有利于煤层气的保存、次生生物气的补给。

The coal seams distribution, petrographic characteristics and coal qualities, pore characteristics, and isothermal adsorption features of coal seams in Jiergalangtu sag of Erlian basin were analyzed. The exploration potential of CBM was predicted from the aspects of CBM generation and preservation conditions. It was considered that the coal seams in this sag are at a stage of low-rank of lignite with a thickness of 10？394 m and coal macerals are dominated by huminite with a volume fraction of 80.5%？ 96.7%. Langmuir volumes are high, ranging of 3.55-10.88 m3/t with a average of 7.29 m3/t. Pore structures axe dominated by micropores and small pores, with the open cylindrical pore or parallel-plate pore morphologies, which provides a favorable condition for CBM desorp-tion. Then the gas content of the coal seams in this area was tested to be from 0.97 to 3.83 m3/t with a average of 2.08 m3/t. The exploration potential of the sag is comprehensively evaluated and the target areas of CBM explora-tion in the future are the southeast of the sag. There are three advantages. Coal seams are away from normal faults and CBM is not easy to escape. ？The roof lithologies of coal seams are mainly mudstone and silty mud-stone, which are beneficial to the preservation of CBM. ③There is the supply of secondary biogenic gas.