Spectrum of pore types and networks in the deep Cambrian to Lower Ordovician dolostones in Tarim Basin, China

Abstract The complex tectonic activities and multi-stage diagenetic modifications lead to the formation of a heterogeneous pore network spectrum ranging from macropores (centimeter-size) to nanometer-size pores ( Three types of matrix dolomites (dolomicrite, microbial dolomite and crystalline dolomites) and two types of dolomite cements (saddle dolomite or crystalline dolomites) are recognized in the Cambrian to Lower Ordovician dolostones. The pore systems include open vugs (enlarged dissolution pores), fabric dissolution pores, intercrystal (dissolution) pores, micro-fractures, as well as intracrystal pores, forming dual or multiple pore networks. The NMR T2 spectra are mainly characterized by bi-modal distributions and mostly right-skewed. The very low T2 components (  1000 ms) represent the vuggy pores with pore sizes spanning from hundreds of μm to thousands of microns. The transition zones (100 ms