Coal seam degasification and its efficiency are directly related to the safety of coal mining. Degasification activities in the Black Warrior basin started in the early 1980s by using vertical boreholes. Although the Blue Creek seam, which is part of the Mary Lee coal group, has been the main seam of interest for coal mining, vertical wellbores have also been completed in the Pratt, Mary Lee, and Black Creek coal groups of the Upper Pottsville formation to degasify multiple seams. Currently, the Blue Creek seam is further degasified 2-3 years in advance of mining using in-seam horizontal boreholes to ensure safe mining. The studied location in this work is located between Tuscaloosa and Jefferson counties in Alabama and was degasified using 81 vertical boreholes, some of which are still active. When the current long mine expanded its operation into this area in 2009, horizontal boreholes were also drilled in advance of mining for further degasification of only the Blue Creek seam to ensure a safe and a productive operation. This paper presents an integrated study and a methodology to combine history matching results from vertical boreholes with production modeling of horizontal boreholes using geostatistical simulation to evaluate spatial effectiveness of in-seam boreholes in reducing gas-in-place (GIP). Results in this study showed that in-seam wells' boreholes had an estimated effective drainage area of 2050 acres with cumulative production of 604 MMscf methane during ~2 years of operation. With horizontal borehole production, GIP in the Blue Creek seam decreased from an average of 1.52 MMscf to 1.23 MMscf per acre. It was also shown that effective gas flow capacity, which was independently modeled using vertical borehole data, affected horizontal borehole production. GIP and effective gas flow capacity of coal seam gas were also used to predict remaining gas potential for the Blue Creek seam.

中文翻译：

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垂直和煤层内水平井生产分析与随机地质统计算法的集成，以估计煤层的开采前甲烷排放效率：Blue Creek 煤层，阿拉巴马州

煤层脱气及其效率直接关系到煤矿开采的安全。Black Warrior 盆地的脱气活动始于 1980 年代初期，使用垂直钻孔。尽管属于 Mary Lee 煤组的 Blue Creek 煤层一直是煤矿开采的主要煤层，但在上 Pottsville 地层的 Pratt、Mary Lee 和 Black Creek 煤组中也完成了垂直井筒对多个接缝进行脱气。目前，Blue Creek 煤层采用煤层内水平钻孔提前 2-3 年进一步脱气，以确保安全开采。这项工作中的研究地点位于阿拉巴马州的塔斯卡卢萨县和杰斐逊县之间，并使用 81 个垂直钻孔脱气，其中一些仍然活跃。现有长矿在2009年扩大作业时，在开采前也进行了水平钻孔，仅对Blue Creek煤层进行进一步脱气，确保安全生产。本文提出了一项综合研究和方法，将垂直钻孔的历史匹配结果与使用地质统计模拟的水平钻孔的生产建模相结合，以评估煤层钻孔在减少就地气体 (GIP) 方面的空间有效性。本研究的结果表明，煤层内井的钻孔估计有效排水面积为 2050 英亩，在大约 2 年的操作期间累计生产 604 MMscf 甲烷。随着水平钻孔的生产，Blue Creek 煤层的 GIP 从平均每英亩 1.52 MMscf 下降到 1.23 MMscf。还表明，使用垂直钻孔数据独立建模的有效气体流量影响水平钻孔生产。GIP 和煤层气的有效气体流量也被用来预测 Blue Creek 煤层的剩余天然气潜力。