Characteristics and evaluation of Cretaceous-Paleogene reservoirs in the northern Tarim basin

Abstract：The main lithologies in the Cretaceous-Paleogene in the northern Tarim basin are litharenite and feldspathic litharenite, which are in the middle diagenetic stage. The main pore spaces are relict primary intergranular pores, intergranular solution pores, intragranular solution pores, pores in grain films and matrix micropores. However, there are certain differences in rock composition, diagenetic evolution and pore association types in different areas and intervals of strata, thus resulting in appreciable difference in hydrocarbon storage capacity, which is mainly controlled by the primary sedimentary environment and diagenesis. According to the lithologies and physical parameters of Paleogene and Cretaceous reservoirs in different areas and tectonic belts, the reservoirs in the region mainly fall into four classes. Classes I and II are main targets for oil and gas exploration and reservoirs of class III belong to low-permeability ones and may serve as targets for gas exploration, while the class IV reservoirs are very low-porosity, very low-permeability and very compact type reservoirs and even non-reservoirs.