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.