页岩气聚集条件及含气量计算——以四川盆地及其周缘下古生界为例

为了研究页岩气聚集条件及含气量的影响因素、计算方法,根据页岩气聚集机理、聚集特征将页岩气聚集的因素分为内部因素和外部因素。内部因素主要包括页岩有机地球化学参数、矿物组成以及物性参数等,外部因素主要包括深度、温度、压力等。通过对四川盆地及其周缘下寒武统和上奥陶统—下志留统41块黑色页岩的有机地球化学参数、矿物组成、物性参数、深度、温度、压力等因素对页岩含气量影响作用的分析,可知反映内部因素的有机碳含量、总烃含量、石英含量、粘土矿物含量、孔隙度(裂缝)、密度、黄铁矿含量和碳酸盐含量等8个参数对页岩气聚集具有重要影响。通过对"二参数"、"六参数"、"八参数"与含气量的多元线性回归得出计算页岩含气量的计算公式,据此公式计算的含气量与实测值吻合良好,且参数越多对页岩含气量的预测越准确。本文建议在条件允许的情况下,尽可能多地利用各种参数对页岩含气量进行预测,以达到更好的预测效果。在勘探早期,建议采用简单易得到的两个最主要参数——有机碳含量和孔隙度进行页岩含气量的计算。

Study on the Shale Gas Accumulation Conditions and Gas Content Calculation-Taking the Lower Paleozoic in Sichuan Basin and its periphery as an Exampl

On the basis of shale gas accumulation theory and accumulation conditions, the controlling factors of shale gas accumulation were analyzed in this paper, which could be divided into internal and external factors. The internal control factors include shale geochemical indices, shale mineral composition and shale petrophysical indicators etc, which is the root cause of things to change and development, the source of the things development and determined the nature and development direction of things. The external control factors include reservoir depth, temperature and pressure of formation, etc, which only through internal control factors work. Things change and development mainly caused by the internal factors, where the depth, temperature, pressure and other external factors have little affect on things change and development. The internal factors and external factors of the shale gas accumulation interdependence and fight each other, thus the power and status of the contradictory position changed, which both determined the shale gas accumulation. Among them the total organic carbon type and content, total hydrocarbon content, quartz content, clay mineral content, porosity(fracture), density, pyrite content and carbonate content of the internal controlling factors are the main factors for generating shale gas reservoir. Using the multiple linear regression between two parameters, six parameters, eight parameters and gas content to obtain the formula for gas content calculation of the shale, and the gas content between the formula calculation and the measured showed linear fit well. The more parameters using, the better it fits. The paper recommended that if conditions permitting, as much as possible using a variety of parameters to predict the gas content of the shale in order to achieve better prediction results. Early in the exploration, it proposed that using the organic carbon content and the porosity which are simple and easy to get to calculate the shale gas content.