LAUSR

Abstract The eastern margin of the Ordos Basin in the Linxing area has great potential for exploration of natural gas. However, the intrusion of the Zijinshan igneous pluton and associated hydrothermal activities have affected the sandstone reservoirs. Through the data analyses of rock thin sections, cathodoluminescence, X-ray diffraction, vitrinite reflectance, fluid inclusions, and reservoir physical property, this paper aims to clarify the influences of magmatic-hydrothermal activity and to explore the response characteristics of reservoir porosity and permeability. From the outer zone to the inner zone, the closer to the pluton, the closer the contact between the reservoir clastic particles, which confirms the compression caused by magma intrusion. The differences in feldspar dissolution and alteration, siliceous cementation, clay mineral content, vitrinite reflectivity, homogenization temperature and salinity of fluid inclusions, confirmed that magmatic-hydrothermal activity affected fluid properties and evolution of strata temperature. Combined with the vertical distribution characteristics of feldspar dissolution-alteration and the abnormal conversion of clay minerals, it is considered that the influence of hydrothermal fluid was limited to the reservoir under the thick mudstone of the Xiashihezi Formation. Magma intrusion causes the development of reservoir fractures, thus the permeability of the reservoir decreases from the inner zone to the outer zone, and the porosity presents the distribution pattern of “high-low-slightly high”. The reservoir porosity and permeability genetic model was established to provide references about favorable areas for oil and gas exploration and development in the Linxing area and areas with similar geological history.