Tectonic relief evolution and large-scale karstification of an Ordovician supergiant reservoir, North Tarim uplift, northwestern China

The discovery of an Ordovician supergiant, karst-type oil field in the North Tarim uplift, northwestern China, has triggered inter-est in hydrocarbon exploration in deeply buried paleouplifts. For multiphase uplift, a comprehensive understanding of large-scale, karst reservoir distribution requires knowledge of structural evo-lution from a three-dimensional perspective and its influence on karstification. High-resolution seismic and borehole data reveal that the North Tarim uplift can be subdivided into four seg-ments from west to east. These segments exhibit along-strike variations in geological architecture, deformational magnitude, and eroded thickness. The evolution of this paleouplift is charac-terized by differential uplift of the various segments correspond-ing to the growth and linkage of multisegment faults and folds. Notably, the early Paleozoic tectono-stratigraphic evolution within the Southern slope is characterized by the transformation of a southwest-dipping monocline into two independent struc-tural highs, implying significant tectonic relief evolution. Karst reservoirs, as targets of recent exploration, are characterized by various types of pore spaces and different degrees of karstifica-tion, and are distributed in different locations. The presence of a tectonic uplift significantly affects the distribution of karst units, indicating a spatial-temporal correlation between tectonic relief evolution and karstification. Tectonic relief evolution explains the superimposition of multiple types and stages of karstification at a single location. The improved karst evolution model that considers multiphase uplift can better interpret the superimposi-tion of various genetic types of karst reservoirs, thereby provid-ing theoretical guidance for karst reservoir prediction and future exploration in deep-marine basins associated with multiphase paleouplifts.