Analysis of the factors influencing movable fluid in shale oil reservoirs: a case study of Chang 7 in the Ordos Basin, China

Abstract

Shale oil in the Ordos Basin is one of the most important areas for further exploration. In this paper, the relationships between the organic geochemistry, physical properties, micropore structure and mobile fluid composition of the Chang7 shale were studied via field emission scanning electron microscopy field emission scanning electron microscopy, nuclear magnetic resonance and computed tomography. The results indicate that the shales are mainly composed of quartz, clay and feldspar. The micro/nanopores are composed of mineral intergranular pores, dissolution pores and intercrystalline pores. The pore size of the mobile fluid ranges from 10 to 30 nm and from 0.1 to 10 μm, and a higher temperature is associated with a better fluidity of 10–30 nm. Based on the fractal turning point method, the shale reservoirs are classified as moderate or high heterogeneity. The mobile liquid was mainly controlled by the brittleness index, permeability, permeability, radius of the throat, radius of the pore throat, and volume ratio of the pore throat. The second factor was the heterogeneity strength and burial depth, but the relationship with TOC content and maturity was not obvious.