Study On Reservoir Characteristics And Distribution Of Donghe Sandstone Member In Central Tarim Basin

The Upper Paleozoic Donghe sandstone with significant production and reserves of oil and natural gas in the Tazhong area is the typical case of oil and gas-rich marine clastic sandstone reservoirs, and its discovery was a major turning point for oil and natural gas exploration in Tarim Basin. The previous studies have shown that detrital sandstones reservoir from Tazhong area have characteristics of diversities, complexity and strong heterogeneity. However, little is known about the distribution of reservoir have serious constraining the exploration progress. Therefore, the characteristics of different clasitic sandstone reservoir, reservoir quality and spatial distribution are necessary to be researched deeply and evaluate objectively.Based on summarizing on the results of previous studies and using of the drilling, the cores, the logging, the physical properties and mercury injection data, the lithology characteristics,reservoir space types of sandstone reservoir of Upper Paleozoic Donghe Formation were studied, and the work of classification and distribution characterstics of the reservoir was done.The sand bodies of the Donghetang Formation in Tazhong area are in general spreading nearly in north-south, thick in NW and thin in SE. Donghe sandstone is the coastal sand body, which forms in the context of persistent transgressive deposition in the Late upper Devonian to early Early Carboniferous, and is transgressive system of the bottom conglomerate or the bottom glutenite strata of Bachu formation, which is a wear lithostratigraphic units. The main rock type includes quartz sandstone, lithic quartz sandstone, with a few lithic sandstone.Donghe sandstone reservoir is characterized by primary granular pores, granular corrosion pores, intergranular corrosion pores, large pores, pore matrix, micro-cracks in several pore types, with residual native bore-tablets dissolved pore combination types as the basic combination.Donghe sandstone reservoir in Tazhong area has experienced diagenesis Generally. In the influence of diagenesis and sedimentation control, the sandstone reservoir forms high porosity and high permeability reservoirs, which average porosity is12.74%, the average permeability is130.30×10-3μm2, and permeability positive correlation.The research interpreted the porosity and permeability of the33wells in the study area using log data and achieved good results. Based on log interpretation porosity and evaluation criteria, Donghe Formation sandstone reservoirs in Tazhong area can be divided into three categories. Evaluation of reservoirs suggest that the most excently development reservoirs of Donghe Formation in Tazhong area are One Class Reservoir and Two Class Reservoir. The Two Class Reservoir is most widely distributed. The thickness of the One Class Reservoir and the Two Class Reservoir are thinner, which development single-layer thickness above10m in individual wellsin the reservoirs. The most proportion of One Class Reservoir and Two Class Reservoir, in the whole stratum are more than50%, the distribution of which are not homogeneity in the stratum.Studies suggest that the reservoir depositional environment, the lithology and the physical properties control of its distribution.