Experimental study of cryogenic treatment of Karaganda coal samples

Q1 Earth and Planetary Sciences
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Abstract

Karaganda Coal Basin bears the largest undeveloped reserve of coalbed methane (CBM) in Kazakhstan, which lacks water resources for implementing large-volume hydraulic fracturing. Cryogenic fracturing utilizing liquid nitrogen (LN2) has been trialled in fields and is a waterless fracturing technique under intensive research these days. This study aimed to evaluate the cryogenic treatment efficacy of Karaganda coal samples as well as to understand the coal permeability evolution during the thawing period. X-ray fluorescent spectrometry (XRF) and microscope imaging identified the compositional and structural heterogeneities of coal specimens mined from different interlayers. Acoustic emission test, permeability measurement, and microscope imaging comparatively characterized the dry coal structure alteration before and after immersion into LN2. Cryogenic treatment slowed down the S-wave velocity through coal specimens, enhanced permeability by over 65 % after temperature recovery as well as created new fractures, enlarged existing ones, and spalled coal particles. Dynamic permeability evolution against temperature rise during the thawing process has been successfully captured for the first time. Overall, the experimental measurements support that the LN2 cryogenic fracturing technique would be effective in stimulating coalbeds for CBM production in Karaganda Coal Basin.

卡拉干达煤炭样品低温处理实验研究
卡拉干达煤炭盆地拥有哈萨克斯坦最大的煤层气(CBM)未开发储量,该盆地缺乏实施大体积水力压裂的水资源。利用液氮(LN2)的低温压裂技术已在煤田中试用,是目前正在深入研究的一种无水压裂技术。本研究旨在评估卡拉干达煤炭样本的低温处理效果,并了解解冻期间煤炭渗透率的变化情况。X 射线荧光光谱法(XRF)和显微镜成像确定了从不同夹层开采的煤炭样本的成分和结构异质性。声发射试验、透气性测量和显微镜成像比较了浸入 LN2 前后干煤结构变化的特征。低温处理减缓了通过煤炭试样的 S 波速度,温度恢复后透气性提高了 65% 以上,并产生了新裂缝,扩大了现有裂缝,剥落了煤炭颗粒。在解冻过程中,首次成功捕捉到了透气性随温度升高而变化的动态过程。总之,实验测量结果证明,在卡拉干达煤炭盆地,LN2 低温压裂技术可以有效地刺激煤层生产煤层气。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Petroleum Research
Petroleum Research Earth and Planetary Sciences-Geology
CiteScore
7.10
自引率
0.00%
发文量
90
审稿时长
35 weeks
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