川西坳陷雷四³亚段沉积微相特征及对储层的影响

Microfacies Characteristics and Its Effects on Reservoir Forming of the Third Period of the Forth Leikoupo Formation in Western Sichuan Depression

摘要: 四川盆地西部坳陷中三叠统雷口坡组雷四³亚段沉积了一套厚度大、纵向连续性好、分布范围广的白云岩，多口钻井在该套白云岩钻揭高产工业气流。在大量岩心、薄片分析基础上，探讨了沉积微相特征及其对储集层发育的影响。川西坳陷雷四³时期为局限台地环境背景下的潮坪沉积，进一步可识别出灰坪、藻灰坪、(藻)云灰坪、(藻)灰云坪、云坪、藻云坪、泥云坪7个微相；雷四³沉积时期沉积水体浅且相对海平面变化频繁，早期发育云坪、藻云坪环境易发生准同生白云岩化，形成大规模的准同生白云岩，为储层发育奠定了基础。

Abstract: In the third period of the forth Leikoupo Formation, Middle Triassic, in western Sichuan depression, a set of dolomite with huge thickness, good longitudinal continuity and wide distribution is deposited. Plenty of drillings gain high nature gas production in this set of dolomite. According to abundant analysis of cores and thin sections, sedimentary microfacies characteristics and its effects on reservoir forming are discussed. During the third period of the forth Leikoupo Formation in western Sichuan depression, the tidal plat deposition system within the restrict platform includes 7 microfacies, such as lime flat, algae lime flat, dolomite lime flat, dolomite flat, algae dolomite flat and mud dolomite flat. The water is shallow and relative sea-level changes frequently during the period. Penecontemporaneous dolomitization, forming a large scale of penecontemporaneous dolomite, is apt to be happened in environment of dolomite flat and algae dolomite flat which builds the fundament of reservoir development.