塔里木盆地下寒武统肖尔布拉克组丘滩体系类型及其勘探意义

基于钻井岩心、薄片以及露头的详细研究,根据地貌背景、沉积物类型和沉积特征差异,将塔里木盆地肖尔布拉克组缓坡丘滩体划分为4种类型:颗粒滩型、丘滩型、滩坪型和台坪型。颗粒滩型主要发育于塔中-巴东地区的"平台"地貌背景下,以鲕粒和砂屑等高能沉积片状发育为特征;丘滩型发育于柯坪-巴楚地区的匀斜缓坡背景,以微生物丘和藻砂屑滩发育为主,呈"小丘大滩";滩坪型发育于阿克苏地区,微生物丘不发育,颗粒滩和潮坪相大面积发育;台坪型发育于轮南-牙哈区,具类似"孤立台地"特征,东侧边缘陡,发育高能丘滩沉积,西侧较缓,以低能微生物丘/席为主。不同类型丘滩体系的储层差异明显,颗粒滩型和滩坪型以Ⅱ类储层为主,分布稳定,有利于储层规模发育;丘滩型和台坪型可发育Ⅰ类储层,储层呈块状分布,具规模优质储层发育潜力。提出塔中-巴东地区应以寻找岩性圈闭为目标,柯坪地区应寻找构造相对稳定、保存条件较好的目标,轮南-牙哈区高能丘滩带值得探索。

Types of mound-shoal complex of the Lower Cambrian Xiaoerbulake Formation in Tarim Basin,northwest China,and its implications for exploration

Based on the observation of cores and thin sections,as well as the detailed survey of outcrops,the ramp mound-shoal complexes of the Lower Cambrian Xiaoerbulake Formation of Tarim Basin can be divided into four types:grain beach,mound shoal,shoal flat,and platform inner flat,in accordance with their differences in geomorphology,sediment category,and sedimentary features.The grain-beach type complex,occurring in relatively flat platform settings in the Tazhong-Badong area,is characteristic of high-energy oolites and intraclastic grainstones growth in slices.The mound-shoal type complex,occurring in ramp settings in the Keping-Bachu area,is characterized by the prosperity of microbial mounds and algae-intraclastic grainstone shoals,displaying a feature of large shoals interspersed by small mounds.The shoal-flat type complex usually occurs in Aksu area with absence of microbial mounds and widespread grain beaches and tidal flats.The platform-inner-flat type complex is developed in the Lunnan-Yaha area,characterized by "isolated platform" with a steep eastern slope (filled with high-energy mound shoal deposits) and a relatively gentle western slope (dominated by low-energy microbial mounds or mats).Reservoirs in different mound-shoal complexes developed distinctive features.The grain-beach and shoal-flat types usually develop Type Ⅱ reservoirs with consistent distribution over large areas; while the mound-shoal and platform-inner-flat types tend to develop Type Ⅰ reservoirs,which are blocky and high-quality reservoirs,and may distribute in a large scale.In conclusion,lithologic traps should be a focus of exploration in the Tazhong-Badong area.While much attention should be paid to those tectonically stable traps with good preservation conditions in the Keping area,the high-energy mound-shoal complexes should be the exploration target in the Lunnan-Yaha area.