突变理论在煤层气储层评价中的应用——以准噶尔盆地砂沟井田为例

煤层气储层评价的方法较多，但将突变理论应用于该类储层的评价则少见。为此，在分析突变理论原理的基础上，综合考虑A（资源特征）、B（开采性能）、C（煤层特征）、D（构造特征）等因素，根据层次分析法原理，建立由目标层、准则层和指标层组成的煤层气储层评价多层次结构，确定了煤层气储层评价突变模型。其中指标层A1（含气量）、A2（资源丰度）、A3（含气饱和度）构成燕尾突变模型；B1（储层渗透率）、B2（储层压力）、B3（顶板孔隙度）、B4（底板孔隙度）构成蝴蝶突变模型；C1（煤层厚度）、C2（煤级）、C3（灰分）构成燕尾突变模型；D1（构造特征）、D2（水文特征）构成尖点突变模型；准则层A、B、C、D构成蝴蝶突变模型。运用突变理论对新疆准噶尔盆地南部煤田砂沟井田煤层气储层进行了评价，得出砂沟井田煤层气储层中下侏罗统八道湾组（J₁b）第5号煤层最有利，然后依次为第6、8、9、19号煤层。突变理论模型与模糊综合评判结果一致，该方法减少了以往评价模型中人为主观因素，评价方法更简单，评价结果更可靠，为煤层气储层评价提供了一条新途径。

Application of catastrophe theory to CBM reservoir evaluation of the Shagou Coalfield, Junggar Basin

There are many methods for CBM gas reservoir evaluation, but the catastrophe theory is rarely used in such methods. Based on an analysis of the principles of the catastrophe theory, a multi level hierarchy is established consisting of a target layer, a criteria layer and an index layer for the evaluation of CBM reservoirs by comprehensively considering A (resource characteristics), B (exploitation performance), C (reservoir characteristics), D (structural features). A catastrophe model was built for CBM reservoir evaluation. The index layers A1 (gas content), A2 (resource abundance) and A3 (gas saturation) constitute a swallow tail catastrophe model; B1 (reservoir permeability), B2 (reservoir pressure), B3 (porosity of the coal seam roof) and B4 (porosity of the coal seam floor) constitute a butterfly catastrophe model; C1 (coal seamthickness), C2 (coal rank) and C3 (ash content) constitute a swallow tail catastrophe model; D1 (structural feature) and D2（hydrology characteristic） constitute a cusp catastrophic model. The criterion layers of A, B, C and D constitute a butterfly catastrophe model. The CBM reservoirs in the Shagou Coalfield of the Zhunnan mining area, southern Junggar Basin, were evaluated by using the catastrophe theory. It is believed that the coal seam M5 in the Middle Lower Jurassic Badaowan Fm is the most favorable CBM reservoir, followed by coal seams M6, M8, M9 and M19. The results are in good agreement with that obtained by using the fuzzy mathematic method. Compared with other CBM gas reservoir evaluation methods, this method is much simpler and more reliable and can also minimize the influences of subjective factors.