Carbonate Diagenesis and Quantitative Evaluation of Its Control over the Reservoir──Exemplified by Carboniferous Bioclastic Limestone Member in Hetian River Gas Field, Tarim Basin

The influence of diagenesis on the carbonate rock reservoir is obvious and serious. The Carboniferous bioclastic limestone member is an important gas-producing formation in Hetian River gasfield in Tarim basin. Principal diageneses are cementation, compaction, pressure-solution, dolomitization, solution and fracturing, which control the reservoir properties of the bioclastic limestone member. The cementation and compaction are main pore destroyers, which destroy almost all primary pores and part of secondary solution pores. Sutures can be formed by pressure-solution and serve as reservoir space and channels for hydrocarbon migration. Dolomitization occurs in penecontemporaneous stage that coincides with the seawater seepage-reflux model. 30 percent of total porosities are provided by intercrystal porosities. The porosity has good correlation with dolomite content. The buried solution is formed by sulphuric acid and can form solution pores, which provide more than 37.5 percent of total porosities. The structural fractures make up the principal permeability contributor of the reservoir.