--> ABSTRACT: The Characteristics and Formation Mechanism of Deep Tight-Gas Sandstone Reservoir in Kuqa Foreland Depression of Tarim Basin, NW China, by Liu, Chun; Ronghu, Zhang; Zhang, Huiliang; Wang, Bo; #90135 (2011)

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The Characteristics and Formation Mechanism of Deep Tight-Gas Sandstone Reservoir in Kuqa Foreland Depression of Tarim Basin, NW China

Liu, Chun 1; Ronghu, Zhang 1; Zhang, Huiliang 1; Wang, Bo 1
(1)Hangzhou Research Institute of Petroleum Geology, Zhejiang, China.

Tight sandstones, the Late Cretaceous Bashijiqike Formation of the Kuqa foreland depression of Tarim basin, is disconformably overlain by over 8000m of clastic red beds in Cretaceous and Tertiary sequence, which is deep-tight sandstone typical. To study the tight-gas reservoir potential of the sandstones, a variety of methods (including core, thin sections observation, logging, scanning electron microscope, core lab analysis, microprobe analysis and acoustic emission measure etc.) were applied to research the characteristics and formation mechanism of deep tight-gas sandstone reservoir.

The results indicated the sandstones are feldspar lithic and rock debris arkosic, rich in sedimentary and volcanic rock fragments. Quartz overgrowths and pore-filling carbonate cements (calcite, dolomite, anhydrite and feldspars) occluded most of the porosity during early to deep burial, assisted by late compaction that improved packing and fractured quartz grains. Minor cements include pore-filling clays, ankerite and authigenic feldspar. The store spaces include protogenesis intergranular hole, the intergranular dissolution pore, the few feldspar and lithic dissolution pore, the corrosion split, micropore, with some fracture. Porosity and permeability of 113 samples averages 5.08% and 0.029 mD, and it is extra-low porosity and permeability reservoir, which shows a modest reservoir potential. However, the unusual growth of fracture provides considerable possibility that high production for such tight sandstones. The extra-low porosity and permeability mainly result from sedimentation, digenesis and tectonic compression.

Deep-bury, fine particles and rich argillaceous set the seal on not good porosity and permeability. Compaction narrowed the store spaces and cementation reduced the size of pore, which together resulted in the forming of tight sandstone. Commonly, the maximum paleostructure stress that comes from tectogenesis is 100Mp in Kuqa foreland depression, which reduced the porosity as high as 10%. Based on the distribution characteristics and homogeneity temperature of fluid inclusion, and combined the burial, thermal and hydrocarbon generation histories of source rock, the hydrocarbon charged reservoir after tight sandstone formed.

 

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.