Macrolithotype characteristics of coal seam and their controls on coalbed methane well productivity in the Hancheng block of the southeastern margin of Ordos Basin.

Previous studies about factors on coalbed methane production cannot meet the need for refined development. This work attempts to study the impact of macrolithotype characteristics known before fracturing on well production, to enable the developer to predict the production potential of each well in advance and adopt a precise development strategy. Logging data of 216 wells were obtained to predict macrolithotypes distribution of No. 3, 5, and 11 seams in the Hancheng block. And macrolithotype characteristics were described from two aspects: the proportion of bright layers in thickness (PBLT) and the number of layers per meter (NLPM), and their impact on well productivity were evaluated respectively by analyzing the production data. The results show that PBLT value increases from No.11 to 3 seams. PBLT has a positive correlation with well productivity. Bright type has the highest productivity potential (771 m3/d), followed by semi-bright type (681 m3/d), and semi-dull type (436 m3/d). There is a negative correlation between NLPM and productivity. Stable type has the highest productivity potential (1049 m3/d), followed by relatively stable type (719 m3/d), and unstable type (405 m3/d). Thick coal seams with high NLPM may not have much production potential. Under multi-seam production, seams with high PBLT should be selected, and NLPM can be used as a critical index to estimate the inter-seam interference before fracturing. [ABSTRACT FROM AUTHOR]