Destruction effect on Meso-Neoproterozoic oil-gas traps derived from Meso-Cenozoic deformation in the North China Craton

Abstract

As the first extensively developed sedimentary cover in the North China Craton (NCC), the thick Meso- to Neoproterozoic strata have great exploration potential for hydrocarbons. However, the Meso-Cenozoic Indosinian, Yanshanian and Himalayan movements caused the Meso-Neoproterozoic strata in the NCC to experience various deformations and even destroyed Meso-Neoproterozoic primary oil-gas reservoirs, especially their trap conditions. Until now, how each Meso-Cenozoic tectonic movement influenced the development and evolution of Meso-Neoproterozoic oil-gas traps in different parts of the NCC has remained unclear. The Indosinian Movement caused Meso-Neoproterozoic rocks to undergo gentle folding, as well as limited thrusting, and mainly brought about the creation of contractional anticlinal traps in the NCC. In contrast, the early Yanshanian Movement mainly triggered their vertical movement and may have introduced some stratigraphic and faulted-related traps. The middle Yanshanian Movement led to the Meso-Neoproterozoic strata being involved in more intense differential folding, thrusting and strike-slip faulting in the western, central, and eastern NCC, at the cost of destroying the earlier-formed structures, especially those in the central-eastern NCC. Thus, the mid Yanshanian Movement showed both constructive and destructive effects on the formation and evolution of the Meso-Neoproterozoic oil-gas traps and made them develop incoherently in different parts of the NCC. The late Yanshanian and Himalayan movements did not affect the Meso-Neoproterozoic strata in the western NCC, but caused those in the middle NCC to be uplifted and eroded further, whilst strata in the eastern NCC became inverted, subsided and buried. As a consequence, it led to the continuous destruction of the Meso-Neoproterozoic structural-related traps for Meso-Neoproterozoic primary hydrocarbons in the central-eastern NCC, and the formation of the Meso-Neoproterozoic buried-hill traps for Cenozoic hydrocarbons in the eastern NCC. Based on our structural analysis, it is suggested that the Meso-Neoproterozoic primary hydrocarbons could have accumulated in various Meso-Neoproterozoic structural-related traps with the overlying well-preserved Paleo-Mesozoic strata, especially, those in the southwest Ordos Basin. The promising Meso-Neoproterozoic buried-hill traps for Cenozoic hydrocarbons are mainly located in the western Bohai Bay Basin and the south part of the southern North China Basin.