长宁地区优质页岩储层非均质性及主控因素

Factors Controlling Heterogeneity in the High-quality Shale Reservoirs of the Changning Region

通过大量实验测试数据的统计分析,明确了川南地区长宁区块优质页岩各小层间存在较强的非均质性,分析了优质页岩储层发育的控制因素。五峰组—龙马溪组下部储层的脆性矿物含量高,黏土矿物含量相对较低(平均为24.5%);储层的储集空间类型多样,以有机质孔隙为主,储层物性在纵向上具较强的非均质性,孔隙度主要在0.73%～10.25%,平均约为4.19%;五峰组和龙一_1亚段5个小层的总含气量在1.27～4.19m^3/t,平均达到2.74m^3/t,龙一_1亚段1小层含气量最高,其次为2小层和3小层,4小层含气量最低。沉积条件是优质页岩发育的物质基础,石英含量高和有机质发育有利于优质页岩储层的形成;压实作用与胶结作用是页岩储层发生致密化的主要机制,而溶蚀作用和有机质热成熟在一定程度上可改善页岩储层质量。

Based on statistical analyses on numerous experimental measurements, sub-layers of the high-quality shales in Changning, Southern Sichuan, were found to be strongly heterogeneous, and the factors controlling the development of highquality shale reservoirs were analyzed. There are high brittle mineral contents but relatively low clay mineral contents（mean24.5%） in the lower reservoir of the Wufeng-Longmaxi Formation. The reservoir has various types of reservoir spaces, although organic matter pores dominate. Relatively strong vertical heterogeneity is noted. Porosity primarily varies between0.73% and 10.25%, with an average of about 4.19%. The total gas contents in the five sub-layers in the Wufeng Formation and Long 11 sub-member of the Longmaxi Formation are 1.27～4.19 m3/t,with an average of 2.74 m3/t. The Long 111 sub-layer has the highest gas content, followed by the Long 112 and Long 113 sub-layers, whereas the Long 114 sub-layer has the lowest gas content. Sedimentation conditions are the basis for high-quality shale development. High contents of quartz and organic matter facilitate the formation of high-quality shale reservoirs. Compaction and cementation are the major mechanisms for densification in shale reservoirs, while dissolution and organic matter thermal maturity can improve the shale reservoir quality to a certain degree.