Quartz Dissolution  Causes and Influencing Factors in the Silurian Marine Clastic Reservoir Rocks in Central Tarim Basin

Key words: 
• mechanism of quartz dissolution /
• influencing factor /
• marine clastic rocks /
• Kalpintag Formation /
• Tarim Basin

Abstract: A large number of secondary porosity due to quartz overgrowths dissolution, at the top of the Lower Sandstone the bituminous sandstone near the unconformity in Kepingtag Formation, in the Silurian marine clastic reservoirs in the central of Tarim Basin. By microscopic and SEM observation, dissolutions of SiO₂ of sandstone reservoirs can  be divided into 3 types, in which the reservoir constructive roles  include quartz siliceous particles edge of dissolution and overgrowths dissolution, while carbonate replacement of quartz and silicon has little constructive. The path of the SiO₂ dissolution path can be divided into the alkaline environment and acidic environment, statistics show that SiO₂ dissolution generally in the alkaline environment of development, but the low level, dissolved in the acidic environment of the type of organic acids, the number of fluid properties, dissolved in fluid ability, as well as the formation temperature requirements are more demanding. Quartz dissolution under acidic fluid medium conditions in the study is the ancient reservoirs destruction process by microbial degradation of hydrocarbons releasing large amounts of oxalic acid plays a major role, because it reduces the surface of the quartz grains  activation energy of the dissolving  reaction, and formation water alkali metal ion salt effect  role, which greatly improve the dissolution rate of SiO₂ lysate spread into the ground water was taken away, resulting in a strong quartz dissolution phenomena, research also shows that the dissolution degree of strong but has a strong limitations. Dissolution of SiO₂(solution) role is to provide a certain amount of space for oil and gas, and important significance to the deep clastic rocks in the Tarim Basin.