Reservoir Description For Triassic-Ⅲ Reservoir At THN1 Section Of Tahe Oil Field

The Tahe oilfield THN1 gas reservoir locates above the THN No.8 structure belt which is in the southwest of the Tarim Basin Akekule Arch Shaya uplift, the main gas-bearing strata is the Triassic Akekule group middle-oil member, the reservoir went into operation in 2007, presently suffers a serious gas flooding, rapid production decline, so further comprehensive adjustment is needed. This paper uses the seismic, drilling, logging, and various types of analysis and test data for fine description of the THN1 middle-oil member condensate gas reservoir structural traps, reservoir characteristics, fluid properties and the establishment of Gas Reservoir Geology model, providing geological foundation for further development in the adjustment program.The THN1 Tari middle-oil gas reservoir is a composite trap which is controlled by lithologic up dip pinch out, fracture and micro-amplitude anticline with NWW distribution. The middle oil-member is a composite sand body, which is an overlapping pattern of braided delta front cover and underwater distributary channel with the thickness of 11-19m. Reservoir lithology is mainly gray-light gray, medium to coarse grained, pebbly coarse-grained lithic sandstone, lithic sandstone and feldspar in the fine sand conglomerate. Generally Sandstone composition and structure maturity are low, the overall properties represent a near-source strong hydrodynamics. Compaction is the primary mode of action to reduce the porosity in the diagenetic process. Dissolution makes porosity increase by 8% percent. The reservoir is now principally at the stage A of diagenetic process. Pore type is mainly composed of intergranular pores, intergranular dissolution pores, with small amount of dissolution pores, intragranular micro-pores, intragranular micro-fractures, grain edge seam, kaolinite crystal micro-pores and micro-cracks. Pore combination is mainly composed by residual interparticle pores structure. Throat structure is mainly mesoporous pore structure-a large hole large throat, face high, good connectivity; has an average of 23.7% porosity and permeability 490.74×10-3μm2, which is medium-high porosity, high permeability reservoir, sedimentary environment and diagenesis are the main factors effect the reservoir properties. Storage layer and interlayer have strong heterogeneity, horizontal heterogeneity is weak, the average density of reservoir interlayer is 0.095, and average frequency of interlayer is 0.10. Horizontal Layer continuity is not fine, has limited resistance of bottom water coning. Evaluation of the THN1 middle oil-member gas reservoir is ClassⅠandⅡreservoir type. The gas reservoir type is a compound condensate gas reservoir with side water and oil ring, which is mainly composed of lithologic pinch out and controlled by fault. Reservoir is a normal temperature and pressure system, flowing pressure is generally lower than saturation pressure in the high position of wells now, retrograde condensation is apparent near the grave shaft.