Control of micro-wettability of pore-throat on shale oil occurrence: A case study of laminated shale of Permian Lucaogou Formation in Jimusar Sag, Junggar Basin, NW China

The control of micro-wettability of pore-throat on shale oil occurrence in different types of reservoir spaces remains unclear. Take the shale oil reservoir of the Permian Lucaogou Formation in the Jimusar Sag, Junggar Basin as an example, the reservoir space in laminated shale and the control of micro-wettability of pore-throat on shale oil occurrence were studied by using scanning electron microscope (SEM), multi-stage pyrolysis, quantitative fluorescence, nuclear magnetic resonance (NMR) and other techniques. The results show that there are mainly two types of laminated shale in the Lucaogou Formation, namely laminated shale rich in volcanic materials + terrigenous felsic, and laminated shale rich in volcanic materials + carbonate. The former type contains feldspar dissolution pores and intergranular pores, mainly with felsic mineral components around the pore-throats, which are water-wet and control the free shale oil. The latter type contains carbonate intercrystalline pores and organic pores, mainly with oil-wet mineral components around the pore-throats, which control the adsorbed shale oil. The oil-wet mineral components around the pore-throats are conducive to oil accumulation, but reduce the proportion of free oil. In the Lucaogou Formation, free oil, with high maturity and light quality, mainly occurs in the laminated shale rich in volcanic materials + terrigenous felsic.

Automated summary

The study reveals that there are two main types of laminated shale in the Permian Lucaogou Formation, namely laminated shale rich in volcanic materials + terrigenous felsic, and laminated shale rich in volcanic materials + carbonate. The former is water-wet and controls the occurrence of free shale oil, while the latter is oil-wet and controls the occurrence of adsorbed shale oil.