Experimental Studies On The Filtration Mechanisms In Low Permeability Heavy Oil Reservoirs

With respect to the low permeability reservoir and heavy oil reservoir, low-permeabilityheavy-oil reservoir is more difficult to develop. In this paper, the study the seepagemechanism can effectively provide guiding significance for development of this kind ofreservoir and lay the foundation for enhancing oil recovery.In this paper the seepage flow characteristics of both low permeability reservoir andheavy oil reservoir are summarized. In the low permeability reservoirs, because of thecharacteristics, such as complicated pore structure, low porosity, strong pore throat effect,high specific surface, the fluid flow in the reservoir is non-linear flow. The starting pressuregradient appears in low permeability reservoir flow, when the pressure gradient is smallerthan the starting pressure gradient, the fluid cannot flow. because of the high viscosity of thecrude oil, which increase the extra viscous force, the seepage process in heavy oil reservoirbecomes more complicated.The starting pressure gradient experiment of low permeability heavy oil reservoirs iscarried on by the method of rate-pressure. According to the starting pressure gradient,respectively discusses the relationship between starting pressure gradient and rockpermeability, fluid viscosity, mobility as well as the temperature, then regress to get thestarting pressure gradient theory chart. Starting pressure gradient decreases with increasingpermeability, increases with the increasing viscosity, and decreases with the increasingtemperature. Starting pressure gradient and mobility show good power law relationship.At the same time, the oil-water and oil-gas two-phase relative permeability experimentsof low permeability heavy oil reservoir have been carried on in this paper by the method ofnon-steady-state method, and obtain the relative permeability curve and its relativepermeability characteristics. Relative permeability curves of low permeability heavy oilreservoir characteristics embodied in: high irreducible water saturation, the lower the permeability, irreducible water saturation is higher; high residual oil saturation, the lower thepermeability, residual oil saturation is higher; narrow scope of two-phase flow, the lower thepermeability, irreducible water and residual oil saturation is higher, thus squeezing two phaseseepage flow range make it narrow; oil phase permeability declining quickly, water phasepermeability rising slowly, final value is low. With the reduction of permeability, isotonicpoint has a tendency to move to the right.