Abstract

Ordovician carbonate is important for petroleum exploration and production in the Tarim Basin. The matrix porosity of the carbonate reservoirs is usually less than 2% because of their age-old sedimentary history and depth (deeper than 5500 m). The storage spaces are secondary dissolution pores and fractures which are dominated by visible dissolution caves, holes, and fractures (Zhou et al., 2006). The reservoirs are therefore called fractured-cavernous reservoirs. Good quality reservoir usually appears as a strong reflection (called “bead-like reflection” or “BR”) on poststack seismic sections, and the corresponding reservoir is called a fracture-cave body (FCB) which is the main drilling target of current E&P in Tarim Basin. The FCBs are unevenly distributed in carbonate strata, and the storage spaces inside an FCB are also unevenly distributed. Therefore, the reservoirs have both macroscopic and microscopic heterogeneities, which bring great challenges to petroleum exploration.

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