Insights into the Weathering Crust Reservoirs of Granitoids: A Case Study from Qinghai Oilfield of Qaidam Basin, Northwest China

With proven reserves of 9.836 × 1010 m3, the largest known natural gas reservoir among terrigenous basement rocks has been discovered within granitoids northern Qaidam Basin. Due to their high heterogeneity, genesis reservoirs remains unknown. Herein, structure weathering crust in and potential controlling factors on development mechanism are discussed using a multidisciplinary approach based data from cores, thin sections, scanning electron microscopy (SEM), conventional imaging logs, physical property major elements analyses. Moreover, classification standard is established. The dissolution belt holding diverse spaces accounts for more than 50% total porosity, while disintegration main context cleavage fractures crack fractures. original pores exist mainly crystal grains quartz mica, secondary were generated by alteration aluminosilicate minerals as well biotite or hornblende. quality these controlled mineral composition, tectonic uplift, faulting, paleogeomorphology. femic granitoid reservoir-forming lithology case dissolution, felsic likely develop cracks. formation significantly linked presence faulting. These belts mostly induced deformation along Altyn fault late Oligocene early Miocene. diversity paleogeomorphology influences extent weathering. exhumation terrane Jurassic Cenozoic corresponds hypergene leaching period granitoids. Three types present rocks: fractured-porous (Type Ⅰ); porous Ⅱ); fractured Ⅲ). developed granitic gneiss granite, was formed diorite gneiss. that dominated Type Ⅰ Ⅱ. highest reservoir, which type, crust, porosity ranging 1.56% 8.48% permeability 0.03 mD 14.48 mD. mechanisms provide further information hydrocarbon exploration worldwide.