Factors Affecting on Dissolution Porosity in Deep Burial Clastic Reservoirs-Examples from Jizhong Depression and Tarim Basin

Key words: 
• clastic reservoir /
• diagenesis /
• secondary porosity /
• Jizhong depression /
• Tarim basin

Abstract: Secondary porosity caused by dissolution of primary skeleton grains and chemical cements is the most important petroleumstorage spaces in deep burial elastic reservoirs. Lithic arkose is the main component of Triassic reservoir sandstones in the Tarimbasin ; carbonate cement in the reservoir ranges from 5 % to 35 %，and in the Tertiary of the Jizhong Depression the common reser-voir rock is arkose, of which carbonate cement is between 3 % and 35 %.The feldspathic grains and carbonate cement provide 6a-sic materials for the formation of solution porosity. Cores taken from below 3500m in Jizhong Depression show the maximumporosity < 20 % and maximum permeability<100 x 10^-3pm². Most of the samples have porosity<10 % and permeability<10x10^-3pm²;In the Tarim basin the Triassic sandstone reservoirs buried deeper than 5000m still have maximum porosity > 20 %and permeability 1000 x 10^-3pm². Production shows that when elastic reservoir buried deeper than 3500m in Jizhong Depressionthe fluid production is always less than 1002/d; while in the Tarim Basin when buried below 5000m, Tertiary elastic reservoirs stillhave an oil production of 500t/d and gas 100000m³/d. This paper compares the deep burial elastic reservoirs in the Tertiary of theJizhong Depression with the Triassic of Tarim Basin and discusses the factors affecting the porosity evolution in deep burial situa-lion. Geotemperature and multiple hydrocarbon sources are the main factors that bring about the difference of reservoir storage ca-pacify in deep burial elastic reservoirs in the Jizhong Depression and the Tarim Basin.