Jiaozuo exploration area is located in the north of Jiyuan fault depression (Jiyuan concealed zone) in the west of South North China Basin. Jiyuan fault depression is a residual basin (slice) divided by late tectonic movement of Carboniferous-Permian coal-bearing basin in northern China, which is covered with Mesozoic and Cenozoic sedimentary caprocks. Coal exploration has initially confirmed that the Carboniferous and Permian coal-bearing strata in the north are covered by Cenozoic strata, while the deep coal-bearing strata in the south are yet to be verified by exploration. Jiaozuo exploration area is located in the northern part of the concealed zone, with a monoclinal structure dipping southeast, with developed folds and faults, which are wide and gentle. The normal faults are NE-NE, NW and EW, and the first two groups are the most developed. The coal-bearing strata are Upper Carboniferous Taiyuan Formation and Lower Permian Shanxi Formation, with Taiyuan Formation 1- 1 coal, Shanxi Formation 1-5 coal and Shanxi Formation 2- 1 coal as the main coal seams, of which 2- 1 coal is the best. 1- 1 coal thickness 0 ~ 2.3 m, 1-5 coal thickness 1.56 ~ 5.2 1 m, 2- 1 coal thickness 0.75 ~1. 2- 1 coal is divided into brittle coal, lump coal and soft coal from top to bottom, indicating that there is structural coal stratification. All the coal seams in the area are anthracite, in which the volatile fraction of 2- 1 coal is 3.78% ~ 7.00%, and the Ro is 3.34% ~ 4.82%. The gas content in coal seam is high, generally greater than 15 m3/t, and the highest is 45.75m3/t. The gas content in coal seam increases with the increase of buried depth of coal seam, and the gas content near fault decreases. Because of the high metamorphic degree of coal and rock, cleavage of coal seam basically does not exist, and the improvement of coal seam permeability mainly depends on structural cracks, so the vicinity of fault or fold axis is the main favorable place to find exogenous cracks.
The exploration area of Jiaozuo is about 1300 km2, and the coalbed methane resources are 1396× 108m3, which has great resource potential. Encun block, located 4 kilometers southeast of Jiaozuo, is sandwiched by two nearly east-west faults and cut by the northeast fault. The nearly east-west fault block has an area of about 186 km2, showing a nose syncline with se strike. 2- 1 The buried depth of coal seam floor is 500 ~ 1000 m, the thickness of coal seam is greater than 6 m, and the gas content is greater than 15 m3/.
1In August, 1995, Zhongyuan Oilfield cooperated with Jiaozuo Coal Mine to explore coalbed methane in Guhanshan Mountain, 25 kilometers east of Jiaozuo. By 19961October, 4 CBM exploration wells had been drilled in Gu 1-4, and the thickness of Shanxi Formation 2- 1 coal seam was 2.60~6.27 meters. All four wells have been tested for gas production, and all three wells have a small amount of gas production except Gu 1 well. The exploration block has complex structure, poor preservation conditions, low gas content in coal seam, complex hydrogeological conditions and poor exploration prospect of coalbed methane. 60 kilometers south of Jiaozuo and 20 kilometers southwest of Zhengzhou, Zhengzhou Natural Gas Company and GEOMET OPERATLNG LNG Company of the United States jointly conducted coalbed methane exploration, and drilled a total of 4 coalbed methane wells, with the target coal seam of Shanxi Formation 2- 1 coal, the buried depth of coal seam is about 350 meters, the coal body structure is pulverized coal, and the permeability is less than 0.001x/kloc-0-3.
Refer to Atlas of Coalbed Methane Basin in China, thickness map of Shanxi Formation II1overlying strata of Jiaozuo Lower Permian, floor structure map of Shanxi Formation II1thickness map of Shanxi Formation II1methane content map of Jiaozuo Lower Permian.