Study on sweet layers evaluation method for coal measures gas joint development

Abstract

This paper selects the main geological factors that affect the coal measure gas (CMG) development, and adopts a multi-level fuzzy mathematical method to construct a sweet layer evaluation system. Among the factors concerned, the reservoir reformability possesses the highest weight, followed by the resource abundance and the gas recoverability. On this basis, the lower Shihezi and Shanxi formations of a vertical well(HN-02) in Pingdingshan Mining Area is evaluated for selecting CMG development sweet layers. As a result, 15 sweet layers are selected, including 7 coal seams, 7 shale layers and 1 tight sandstone layer. Among these sweet layers, the 21 coal, the 42 coal and its floor carbonaceous mudstone have good resource conditions. The 43 coal roof fine sandstone and mudstone, the 42 coal floor thin coal seam and carbonaceous mudstone, as well as the bottom mudstone of the lower Shihezi Formation possess high reformability. During the CMG development stage, the sweet layers are suggested to be perforated and fractured preferentially, which would be conducive to improve the recoverable resources within the well control range and the reservoir stimulation effect under an limited fracturing scale, so as to promote the efficient production of coal measure gas.

Keywords

• coal measure gas development
• multi-level fuzzy mathematics method
• resource condition
• reformability
• sweet layer