高演化湖相页岩储层特征及其主控因素--以普光地区中侏罗统千佛崖组千一段为例

Reservoir characteristics of high-evolution lacustrine shale and its main controlling factors:a case study of the 1st member of Qianfoya Formation of Middle Jurassic in Puguang area

为了探讨川东北普光地区中侏罗统千佛崖组千一段湖相页岩储层特征及其主控因素,开展了有机地球化学、矿物组成、孔隙结构参数等分析测试。研究表明:普光地区千一段④小层中发育黑色页岩段,具有较高的有机质丰度(总有机碳质量分数平均为1.46%),干酪根类型以Ⅱ1型为主,镜质组反射率介于1.9%~2.0%,达到高成熟阶段,黏土质量分数介于44.57%~62.24%,石英质量分数介于22.1%~38.6%;孔隙类型以有机质孔为主,比表面积和孔体积均值分别为7.88 m2/g和0.0012 cm3/g,孔隙度均值为4.54%,孔隙结构以锥形孔及四面开放的尖壁孔为主。分析相关性后发现,页岩比表面积和孔体积与总有机碳质量分数的相关性呈先下降后上升趋势,说明随着总有机碳质量分数增加,有机质孔成为页岩孔隙空间的主要贡献者,无机质孔对孔隙发育影响减弱。黏土矿物与充足有机质的混合输入是千一段优质储层形成的基础,中—高碳黏土质页岩是普光地区千一段湖相页岩的关键储集岩相。

In order to study the characteristics and the main controlling factors of the lacustrine shale reservoir in the first member of Qianfuya Formation of Middle Jurassic in Puguang area,Northeast Sichuan,the organic geochemistry,mineral composition and pore structure parameters were analyzed and tested.The research shows that a black shale section developed in the fourth layer of the first member of Qianfuya Formation in Puguang area,which generally has a high total organic matter abundance(TOC is 1.46%on average).Kerogen type is mainly typeⅡ1,vitrinite reflectance is between 1.9%and 2.0%,reaching high maturity stage.Clay content is between 44.57%and 62.24%,and quartz content is between 22.1%and 38.6%.Pore types are mainly organic pores.The mean values of specific surface area and pore volume are 7.88 m^2/g and 0.0012 cm^3/g respectively;the mean value of porosity is 4.54%;the pore structure is mainly cone-shaped and four side opening sharp wall type.By correlation analysis,it is found that the specific surface area,pore volume and total organic carbon content of the shale decrease first and then increase,indicating that with the increase of organic matter abundance,organic pores become the main contributor to the pore space of the shale,and the influence of inorganic pores on the pore development is weakened.The mixed input of clay minerals and sufficient organic matter is the basis for the formation of high-quality reservoirs in the first member of Qianfoya Formation.The medium-high carbon argillaceous shale is the important reservoir facies for lacustrine shale gas in the first member of Qianfoya Formation in Puguang area.