ORIGIN AND RESERVOIR OF SANSHANZI DOLOMITE IN LOWER PALEOZOIC OF ORDOS BASIN

Sanshanzi dolomite of lower Paleozoic in Ordos basin is a diachronous compound dolomite body resulted from multiplex dolomization and multimechanism. Two dolomitization environments and seven dolomitization types are recognized. Middle\|coarse crystallized dolomite, residual grain dolomite, fine crystallized dolomite and lime\|dolomite are the important reservoir rocks in this area, and various reservoir spaces are developed. Solution pore, solution fissure and solution stylolite are the main reservoir spaces. Two reservoir rock bodies are developed in Sanshanzi dolomite. The upper reservoir rock body has a good reservoir property, and its forming is related to paleokarst. The reservoir property of lower reservoir rock body is worse than that of the upper body. The forming of lower reservoir concerns with the buried diagenesis.