Coal gas reservoir has different physical properties from sand and shale stone formation, it is difficult for conventional test to get formation parameters.

煤气储层具有与砂泥岩地层不同的储层物性，常规测试很难获取地层参数。

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Horizontal maximum and minimum principal stresses are nearly equal in shale formation, and very different in sand formation.

在泥岩段水平最大与最小主应力基本相等或相差甚小，在砂岩段才呈现较大差异。

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There are many factors to affect identification of oil and gas bearing layers in the sand-shale formation.

在砂泥岩地层中，影响油、气层识别的因素较多，尤其在复杂地质条件下准确识别油气层难度更大。

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Rather, as a consequence of injecting water and sand into the shale formation to crack the rocks so gas and oil will flow, massive amounts of waste water comes back to the surface with significant amounts of contaminants as a result of leaching out salt, heavy metals and trace amounts of radioactive materials from the rock formation itself.

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