沁水盆地南部煤储层裂缝测井响应与参数重构

Logging response and parameters reconstruction of coal reservoir fractures in the southern Qinshui Basin

煤层气开发效果很大程度上受控于煤层裂缝发育特征,沁水盆地南部同样如此。根据相似露头区野外地质调查、岩心观测以及成像测井、常规测井等资料,对比分析该区煤储层裂缝发育特征及其常规测井裂缝响应,建立了煤储层裂缝的常规测井识别方法,分析了该方法的应用效果。结果表明,研究区煤储层裂缝以构造剪切缝为主,发育北东—南西向、北西—南东向、近东—西向和近南—北向4组;裂缝多为有效裂缝,以高角度和倾斜裂缝为主,规模较小,密度变化大。常规测井裂缝的响应特征主要表现为低电阻、深浅侧向电阻率呈现正幅度差,三孔隙度测井向孔隙度变大偏转但不明显,高伽马值、扩径现象明显,测井曲线会出现波动。在此基础上,重构了异常变化指数,对常规测井曲线进行处理,经过加权合成裂缝预测指数对煤储层裂缝发育情况进行预测,预测结果得到了岩心及成像测井资料的验证。

Effect of coalbed methane development is obviously influenced by the fracture characteristics in coal reservoir,and it is true for southern Qinshui Basin.According to the data on investigation in field with similar outcrops, core description,Formation Microscanner Image analysis and conventional logging, researches about fractures in coal reservoir formation were carried out on its development characteristics and response characteristics on conventional logging, based on which we get the method of identifying fractures in coal reservoir and analyse the application effect of this method.Fractures in research area are mainly tectonic shear fractures in NE,NW, near EW and near NS directions,and most of them are valid with high angle or some dip, small scale and great changeable density.The response characteristics of fractures in conventional reservoir are mainly represent as low resistivity,positive amplitude difference in laterolog resistivity of shallow and deep formation, some, but not obvious, deflection to larger porosity in three porosity log, high gamma value, obvious diameter extension, certain fluctuations in logging curve.On this base, anomaly index were reconstructed, fracture predictive index were composed by weighting processed logging curve to predict the fractures features in coal bed.The predictive result agrees well with core and FMI,which show that this method can provide certain reference function in identifying fractures in coal reservoir.