关键词: 塔里木盆地, 奥陶系, 埋藏溶蚀作用, 颗粒石灰岩, 成因机理

Abstract:

The comprehensive study of some samples from the Ordovician granule limestone in Tarim Basin showed that the burial dissolution could be classified as in-source dissolution and out-source dissolution based on the macro-microcosmic petrology and geochemistry features. There are different origin and migration path for the acid fluids in two stages of dissolution. The burial dissolution fluids might be organic acid, CO₂ and H₂S originated from the maturation of organic matters and decomposition of hydrocarbon. The fluid of in-source dissolution came from the organic matter in granule limestone, while the fluid of out-source dissolution mainly came from the shale source rocks far away from granule limestone strata. The burial dissolution reservoir was resulted from the actions of the in-source dissolution and the out-source dissolution. The granule limestone firstly formed the unattached pinholes under the action of in-source dissolution and afterwards suffered wide dissolution from the out-source fluid moving along the unconformities, seams, ruptures and associate fissures. The mineral composition of the stratum and the thermal convection of fluid are the important factors for forming the favorable reservoir.

Key words: Tarim Basin, Ordovician, burial dissolution, granule limestone, genesis mechanism