柴达木盆地深层天然气测井识别方法研究

Method Study on Deep Gas Logging Identification in Qaidam Basin

柴达木盆地深层储层岩石成分复杂,物性相对较差,钻井液密度大、侵入严重。用石英砂岩交会图骨架值参数法计算的孔隙度误差较大,钻井液的高侵使计算的含气饱和度偏高,造成油气层的误判。岩石颗粒密度分析认为,储层为非纯石英砂岩,含有高密度碎屑颗粒。采用了基于岩石颗粒密度实验的零孔隙度骨架参数选取方法,所得参数与岩心分析结果吻合,提高了孔隙度计算精度。通过采用视地层水电阻率法和反映储层结构与孔隙大小的变m值方法提高了测井解释符合率,解决了流体性质识别问题,从理论上证明了视地层水电阻率方法能消除钻井液侵入对饱和度计算的影响。研究成果应用于实际生产,取得了良好的应用效果。

In the deep reservoir of Qaidam Basin, the rock mineral compositions are complicated, physical properties are relatively poor, and heavy drilling fluid density makes formation intrusive seriously. The error is large by using quartz sandstone porosity cross plot method to calculate the porosity, the increased resistance invasion of drilling fluid makes high gas saturation calculations, resulting in a misjudgment of gas layers. It is believed that non-pure quartz sandstone reservoir containing a high density of rock debris particles from the particle density analysis. The porosity obtained from the method of selecting zero porosity matrix parameters based on test of grain density is consistent with analysis result of core data, thus improving the calculation accuracy of the porosity. By using the method of apparent formation water resistivity and the method of varying m-value which reflects reservoir structure and pore size, logging interpretation concordance is improved, the problem of fluid identification is solved, and so theoretically the apparent formation water resistivity method can eliminate the impact of drilling fluid invasion on saturation calculations. The research results are applied to natural gas exploration, and good application results are achieved.