关键词: 塔河油田, 奥陶系, 灰岩, 埋藏溶蚀作用, 溶蚀孔隙

Abstract: Well-developed burial dissolution was found in Yijianfang Formation limestone of Tahe Oilfield.The burial dissolution pores are very important reservoir space for oil-gas in the southern slope of Tahe Oilfield.According to the shape of dissolution pores and the source of dissolving fluids,the burial dissolution can be sub-divided into two types including self-sourced dissolution and foreign-sourced dissolution.The aggressive components for the self-sourced dissolution include organic acids,CO₂ and H₂S derived from thermal maturation of organic matters preserved in the limestone.The self-sourced dissolution is generally weak,because there is a little amount of organic matters and limited aggressive components in the limestone.Consequently,the self-sourced dissolution can only create some small,rounded and isolated dissolution pores at the position where the organic matters were preserved.The aggressive components for the foreign-sourced dissolution include organic acids,CO₂ and H₂S,which were derived from organic matters in hydrocarbon source rocks.The aggressive components mixed with oil/gas-bearing fluids migrated into the limestone along faults,fractures,unconformity surfaces and stylolites from hydrocarbon source rocks.Some relatively large and connected pores were generally formed in the foreign-sourced dissolution.The models for the two types of dissolution were proposed.

Key words: Tahe Oilfield, Ordovician, limestone, burial dissolution, dissolution pores