Reservoir Characteristics and Factors Controlling the Jurassic Sangonghe Formation in Zhongguai Uplift,Junggar Basin

Key words: 
• reservoir physical properties /
• Zhongguai Uplift /
• Sangonghe Formation /
• controlling factors

Abstract: As a positive sub-tectonic unit in the Junggar Basin,the accumulation background of the Zhongguai Uplift is very favorable for gas exploration. The physical properties and main controlling factors of the Sangonghe Formation sandstone reservoir were studied by observing the petrographic characteristics of rock cores and thin sections in selected main wells,and by X-ray diffraction(XRD) analyses,well logging,scanning electron microscopy(SEM) and mercury injection,revealing that the sandstone reservoir consists mainly of feldspathic litharenite and lithic sandstone. Particles in phase 2 of the Sangonghe Formation are larger than those in phase 1 and were mainly of average size,with medium structure maturation and low composition maturation. The porosity and permeability of the reservoir was low in places,but it was mainly of medium porosity and permeability. Sedimentary microfacies at the foreedge of underwater distributary channels in braided river deltas accounted for pore and sand particle development in the reservoir. Analyses of the evolution over this period indicated that reservoir compactness was mainly influenced by compaction and cementation;following the latter,dissolution may have increased the porosity of the reservoir to some extent and offered favorable pathways for gas accumulation.