Abstract:

The Upper Paleozoic clastic buried hill is an important field for oil and gas exploration in Kongnan area of Huanghua Depression, and the lower Shihezi Formation is the main gas formation with low degree of exploration. The study on the reservoir characteristics and controlling factors of lower Shihezi Formation is still a blank field. Based on the analysis of ordinary thin sections, cast thin section, scanning electronic microscope and physical properties, this paper studied reservoir characteristics of the lower Shihezi Formation in Kongnan area and their influencing factors. The result shows that clastic rock reservoir of the lower Shihezi Formation belongs to braided river sedimentary system, rock types are mainly gray medium-coarse graind lithic quartz sandstone and feldspathic sandstone of channel microfacies, the reservoir space of inner buried hill mainly includes secondary intergranular dissolved pores and structural fracture, the porosity and permeability are 5%～10% and 0.5～10 mD respectively, and the reservoir is a cracked-poroustype with super-low porosity and extra low permeability. Deposition, diagenesis and tectonization are the three factors controlling the reservoir quality, of which microfacies, lithofacies and tectonization determine the formation and development of buried hill inner reservoir, and favorable reservoirs are laterally distributed in the stacked area of channel and diara sand and fracture-developed zones. This comprehensive study shows that the reservoir of type Ⅰ is located in the principal part of the thrust structure zone and the main reservoirs to increase production in the future.

Key words:  carbonate microfaies , Middle Triassic , Leikoupo Formation, Tianjingshan Formation, Hanzeng area of Jiangyou