Characteristic analysis of deep water gravity flow sediments in Ch6-Ch7 Section of Yanchang Formation in the Binchang Block, southern Ordos Basin, China

Abstract

Massive sandstone without sedimentary structure is developed in the Ch6-Ch7 Section of Yanchang Formation in the Binchang Block, Southern Ordos Basin, which has a good oil and gas show, good productivities and good exploration and development prospect. However, the formation mechanism of the sandstone is still in dispute. It is of great significance to determine the sedimentary facies and sedimentary model of the sandstone in Ch6-Ch7 Section in order to analyze the formation mechanism of sweet spot in the low permeability sandstone reservoirs, to predict the sweet spot distribution model and guide the subsequent exploration and development. In this paper, 15 lithofacies and 3 main types of sedimentary microfacies, namely, sandy debris flow, turbidite and seismite slump microfacies, have been identified by using a large amount of core sedimentary description data, grain size analysis data and geological mapping analysis, and these three kinds of sedimentary assemblies in space. The deep water gravity flow deposition model in the Ch6-Ch7 Section can be summarized as the sublacustrine fan model and can be divided into three subfacies or assemblies: the upper fan subfacies dominated by the assembly of seismite-slump and sandy debris flow, the mid-fan subfacies dominated by the assembly of the sand debris flow-turbidite microfacies and the lower-fan subfacies dominated by turbidite flow-basin plain microfacies assembly.

Keywords

• ordos basin
• binchang block
• ch6-ch7 section
• sandy debris flow
• gravity flow sediment