塔里木盆地寒武系沉积模式与烃源岩发育

综合利用露头、钻井和地震资料,解剖了塔里木盆地中下寒武统沉积特征,并建立其沉积模式,预测烃源岩的分布。研究认为,塔里木盆地寒武系发育缓坡和台地—陆棚2种沉积模式,沉积演化总体上呈台地前缘斜坡由缓至陡、坡度由小到大的变化趋势。结合寒武系沉积格局以及烃源岩的沉积构造、岩性组合、矿物成分与成烃生物特征,认为寒武系有效烃源岩主要形成于深水陆棚环境。成烃生物与深水陆棚沉积环境协同演化,表现为深水陆棚泥质区以底栖藻生物相占优势,而深水陆棚钙质区以浮游藻生物相占优势。深水陆棚相在整个寒武纪期间不断发生空间上的变迁,形成了纵向上叠置、平面上交错的烃源岩分布特征。肖尔布拉克组下部黑色薄层泥质灰岩发育于深水陆棚相,沉积环境暗示这套岩性组合可能是塔里木盆地西部地区一套有效的烃源岩。

Sedimentary model and development of the Cambrian source rocks in the Tarim Basin,NW China

Outcrop, drilling and seismic data were utilized to analyze in detail the sedimentary characteristics of the Middle and Lower Cambrian in the Tarim Basin. A sedimentary model was established to provide a scientific basis for the prediction of source rock distribution. The studies suggested that both the sedimentary models of ramp and platform-shelf were involved in the Cambrian deposition in the Tarim Basin. As a whole, the trend of the Cambrian sedimentary evolution was characterized by the variation of a low angle to steep platform margin. It was assumed that the effective source rocks of Cambrian in the Tarim Basin were mainly formed in a deep water shelf environment combined with the Cambrian sedimentary pattern and the sedimentary structure, lithological assemblage, mineral composition and hydrocarbon generating organisms of the source rocks. Hydrocarbon generating organisms evolved together with the deep water shelf sedimentary environment. In the argillaceous and calcareous deep water shelf, the advantage of biofacies lay with benthic algae and planktonic algae, respectively. As a result of the migration of the deep water shelf through the Cambrian period, the distribution of source rocks was vertically stacked and laterally staggered. Since the black thin marlite in the lower Xiaoerbulake Formation developed in a deep water shelf, the sedimentary environment suggested that it was expected to be another source rock of the western Tarim Basin.