3-D Modeling of Transportation Framework of Tight Sandstone Reservoir in Foreland Thrust Belt, Kuqa Depression

Abstract

Based on analogy between reservoir bed and outcrop, and combining core analysis, imaging logging interpretation, geo-stress analysis, and casting sections, scanning electron microscope, confocal laser scanning, and CT scan data analysis, with the control of sedimentary microfacies, by using effective thickness of sand body and gas saturation as main parameter indices, this paper builds a 3D model of transportation framework of Bashijiqike tight sandstone reservoir bed of the Cretaceous in the Keshen 2 gas field with geological reserves over hundred billions cubic meters. The transportation system of the Keshen 2 gas field can be divided into two types: medium and large scale transportation system with meter scale fractures, and micro transportation system with penetrating particles fracture, micro fracture-grain-edge fracture, micro pore and throat. (1) Medium and large scale transportation system mainly developed in the axial structure of squeezing fold and showed high angle tension fractures. Fractures strike is mainly west and east. Dip direction is mainly south and north. Fractures are partly filled–unfilled and associated with heterotropic and netted fractures. Average density of fractures is 0.35 per meter with fracture density over 0.5 per meter accounting for 15%. Fractures dip is 50°~90°. Aperture is 50~400 μm with peak value being 200~400 μm. These fractures are the main vertical migration path for natural gas. (2) According to the combination of fracture, pore and throat, the micro transportation system can be divided into multi-stage fracture-pore combination mode, single-stage fracture-pore combination mode and throat-pore combination mode. When the fracture is filled and half-filled, transporting efficiency of the first two kinds of combination mode are relatively low and throat-pore combination mode is the main micro transportation system. When the fracture is half-filled and unfilled, transporting efficiency of the multi-stage fracture-pore combination mode and single-stage fracture-pore combination mode are relatively high, and become the main micro transportation system. (3) A comprehensive migration pattern is proposed to determine the favorable gas accumulation areas, in which natural gas in tight sandstone of the Keshen 2 gas field transports vertically from low permeability layer to relatively high permeability layer and laterally north and south is the main migration direction while west and east is the supporting direction.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015