Abstract
The evaluation and prediction of favorable coalbed methane (CBM) sweet spot play an important role in well location deployment and recovery prediction in CBM blocks. This work investigates the CBM geology and accumulation characteristics of No. ( 8 + 9 ) coal in the Carboniferous Taiyuan Formation in Yangjiapo block based on data from 14 CBM wells. The desorption index is proposed to be used to study the CBM desorption potential in Yangjiapo block, and the parameter of reduced water level is adopted to study the CBM hydrodynamics of the block. Furthermore, the analytical hierarchy fuzzy evaluation method is used to evaluate and prediction the CBM development sweet spot in Yangjiapo block. The results show that the buried depth of the No. ( 8 + 9 ) coal seam in Yangjiapo block varies from 693.20 to 1213.20 m, the coal thickness is from 5.40 to 13.10 m, the gas content is from 5.89 to 10.55 m3/t, and the minimum horizontal principal stress is from 9.80 to 20.82 MPa. The desorption potential is better in the southeastern and central-western part of the block. It is found that there is a positive relationship between CBM content and hydrodynamics and indicated that CBM easily concentrates in the lower reduced water level area. The CBM favorable development sweet spot is forecasted to be located in the southeastern part, central-western region, and northeastern part of Yangjiapo block.
Highlights
Coalbed methane (CBM) resources are very abundant in China, especially in the Ordos Basin [1]
The Yangjiapo block is located in the eastern part of the Linxing area, Hedong coalfield, eastern margin of Ordos Basin (Figure 1)
The Yangjiapo block in northeastern Linxing area is located in western margin of Shanxi anticline of North China Platform, eastern margin of Ordos Basin, and northern Hedong Coalfield
Summary
Coalbed methane (CBM) resources are very abundant in China, especially in the Ordos Basin [1]. The Yangjiapo block is located in the eastern part of the Linxing area, Hedong coalfield, eastern margin of Ordos Basin (Figure 1). It covers an area of about 150 km and is rich in the Permo-Carboniferous coal and CBM resources. Most of studies on the CBM in the Linxing area are focused on the geological background and some primary evaluations of CBM reservoirs [3,4,5,6,7,8] These data are insufficient to evaluate the CBM development potential and choose the sweet spot area in Yangjiapo block.
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