Emplacement of intrusions of the Tarim Flood Basalt Province and their impacts on oil and gas reservoirs: A 3D seismic reflection study in Yingmaili fields, Tarim Basin, northwest China

Abstract

A basaltic dike-sill network is emplaced into the shallow subsurface of the Yingmai-2 dome, northern Tarim Basin, northwest China. The 3D seismic reflection imaging suggests that these dikes and sills are fed from an intrusion at the focal area of the dome. This basaltic intrusion has a width of approximately 3000 m and thickness of approximately 1000 m, and it is connected with a much larger Early Permian igneous body in the northern Tarim Basin. An unconformity between the Permian basalt lava flows and the base Triassic conglomerates truncates the dome, meaning that the dome must have developed prior to the Triassic. The basaltic intrusion that emplaced beneath the dome likely pushed the surrounding middle Cambrian salts away and instigated uplift of the overlying upper Cambrian to the lower Permian strata. In most cases, igneous activity plays a negative role on formation of oil and gas reservoirs. However, in the Yingmai-2 case, intrusive magmatic activity has caused “forced folding” of the overburdened strata and controlled the formation of a large commercial oil trap. We suggest that the magmatic activity thus also acts as a positive role on the local formation of a producing petroleum system.