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Breakthrough of shallow shale gas exploration in Taiyang anticline area and its significance for resource development in Zhaotong, Yunnan Province, China
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LIANG Xing,XU Zhengyu,ZHANG Zhao,WANG Weixu,ZHANG Jiehui,LU Huili,ZHANG Lei,ZOU Chen,WANG Gaocheng,MEI Jue,RUI Yun
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Table 5 Criterion of shallow shale gas sweet spot selection in Zhaotong demonstration zone.
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| Type | TOC>2% shale thickness/m | Total porosity/
% | Total gas content/
(m3•t-1) | Shale gas reservoir pressure coefficient | Brittle index | Caprock conditions of
shale gas reservoirs | Structural
deformation
strength | Regional cap thickness/m | | Ⅰ | >30 | >4 | >4 | 1.2-1.6 | >65 | Tight lithology, large thickness, stable distribution, and high breakthrough
pressure (marlstone, shale) | Weak (dominated by fold deformation, compressive closed fault) | >50 | | Ⅱ | 30-10 | 2-4 | 2-4 | 1.2-1.0 | 65-50 | Relatively tight lithology, medium thickness, stable distribution, relatively high breakthrough pressure (tight sandstone, limestone) | Medium (folds and faults are relatively developed) | <50 | | Ⅲ | <10 | <2 | <2 | <1.0 | <50 | Unconsolidated lithology, small thickness, instable distribution, low breakthrough pressure (sandstone, crushed limestone) | Strong (open faults, connected to the
surface) | / |
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