Velocity-sensitive characteristics and main controlling factors of tight glutenite reservoirs in Baikouquan Formation of Maxi slope

The glutenite reservoir in Xinjiang have a strong velocity (flow rate) sensitivity and its main control factors are not clear because of its wide particle size distribution and strong heterogeneity. In this study, different techniques were used for core analysis with core samples from Baikouquan Formation in Maxi slope, including thin section analysis, scanning electron microscope, high-pressure mercury injection and velocity sensitivity experiments. The results show that the clay minerals content has a weak influence on the velocity sensitivity of the samples, while the physical property is the main factor affecting the sensitivity of the glutenite reservoir, and the permeability ratio decreases rapidly at first and then slowly declines with the increase of flow rate. When the permeability is less than 0. 1×10-3 μm2, with the improvement of reservoir physical properties, the throat gradually becomes larger, and some minerals (particles) that were difficult to pass through the throat can pass through the throat along with the fluid flow, and so the velocity sensitivity index decreases with the improvement of permeability. When the permeability is greater than 0. 1×10-3 μm2, the throat radius involved in flow changes little, but the pores are well connected and there are many connected throats. More clay minerals that did not move firstly in the pores begin to move along with the flowing displacement fluid. But when there are enough minerals (particles), the throat can be blocked, resulting in the decrease of permeability and the increase of velocity sensitivity index with the improvement of permeability. © 2024 University of Petroleum, China. All rights reserved.