Pore throat size distribution and oiliness of tight sands-A case study of the Southern Songliao Basin, China

Abstract

In this study, several methods such as mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR) for characterizing the pore throat size distribution of tight sandstone reservoirs were selected. The differences of mercury injection parameters such as maximum interconnected pore throat radius, median radius, mercury injection curve, and pore throat distribution curve of oil-bearing and oil-free samples were compared. By designing the algorithm program and using the mercury injection data, the coefficient of converting the T2 relaxation time to the pore-throat radius was corrected, and the pore throat distribution of different oil saturation samples were analyzed. Environmental scanning electron microscope (ESEM) was also used to observe the microscopic pores and the oil in them. Using the above data, we systematically analyzed the control of pore throat distribution on the oiliness. It is found that the oiliness depends on the maximum interconnected pore throat radius, and the oil saturation depends on the oil migration front pressure and pore volume. The oiliness of tight sand has good relationship with pore throat size distribution, and the better reservoir petrophysical properties result in better oiliness. Statistics on the pore throat size distribution of oil-bearing tight sands were carried out and main intervals of pore throat size distribution of oil-bearing reservoirs were given in this paper. This understanding provides a basis for searching sweet spots in the future exploration of the tight oil.