塔里木盆地麦盖提斜坡奥陶系风化壳成藏条件

基于地震、钻井资料综合研究,分析塔里木盆地麦盖提斜坡及其周缘古隆起背景上奥陶系风化壳特征及其储集层发育主控因素,探讨该区油气分布规律与勘探方向。区域构造成图与构造解析表明,麦盖提斜坡及其周缘发育塔里木盆地最大规模的奥陶系碳酸盐岩风化壳,与上覆志留系/石炭系泥岩形成优质储盖组合。奥陶系碳酸盐岩历经多期大型岩溶作用,以受古岩溶地貌、构造作用与岩性控制的小型缝洞体储集层为主。已有钻探多位于北部岩溶缓坡—洼地,岩溶作用较弱、充填严重,据古地貌分析与储集层预测,南部岩溶斜坡区储集层应更发育。构造演化与生烃演化史综合分析表明,碳酸盐岩古隆起演化与变迁控制了油气的运聚与分布,具有晚海西期成油、喜马拉雅晚期调整与原油裂解气再成藏的两期充注史。古隆起东西两端的玛南、麦西斜坡区长期位于油气聚集与调整的有利部位,具备形成大面积碳酸盐岩缝洞型岩性油气藏的地质条件,是塔里木盆地碳酸盐岩油气勘探的有利接替领域。

Reservoir-forming conditions of the Ordovician weathering crust in the Maigaiti slope, Tarim Basin, NW China

Based on the formation mechanism of water-soluble gas, combined with the geological conditions of the Palaeogene Huizhou Depression, the resource potential and utilization of water-soluble gas in the Palaeogene Huizhou Depression are analyzed quantitatively using grid calculation method. The Wenchang and Enping Formations of the Palaeogene Huizhou Depression are major source rocks that generate significant quantities of gas and the sandstone reservoirs are weakly overpressured to overpressured on the whole. Calculated according to the thickness, sandstone content, porosity, water saturation, strata pressure, temperature and mineralization of the Wenchang Formation and Enping Formations, the resource volume of water-soluble gas is about 1 791.49×108 m3 and 2 688.5×108 m3, 1.19 and 3.46 times that of the conventional gas, respectively. If the strata pressure is relieved to normal pressure, the degasification volume is 80.84×108 m3 and 97.04×108 m3. The water-soluble gas is an unconventional resource with great potential, and provides continuously gas source for conventional pools through degasification.