The method of non-stationary flooding and the conditions for its effective use in the operation of an oil field

Abstract

The article describes the essence of unsteady waterflooding, which is one of the most effective methods of increasing the oil recovery factor, used to change the direction of filtration flows, which makes it possible to engage in the development of undeveloped oil reserves and reduce the rate of watering of the deposit in productive reservoirs. A common technological method of unsteady water flooding is the use of cyclic modes of operation of injection wells. The essence of this method is that at an unsteady state in the oil deposit, there are conditions for the continuous manifestation of elastic forces of the reservoir system. In a heterogeneous reservoir between different zones, channels, and fluid flows there are gradients of hydrodynamic pressures, due to which there can be fluid flows from one layer to another, from fractures to blocks, as well as changes in flow directions. During unsteady flooding of heterogeneous formations, a part of oil reserves in low-permeability layers or zones remains uncovered by injected water. The waterflooded reservoir appears as an unsystematic alternation of watered and oil-saturated microflows.  While creating in such reservoirs alternately changing in value and direction of pressure gradients, conditions for injection water penetration into stagnant oil-saturated low-permeable zones and channels appear in the oil reservoir and oil movement from them to active drainage zones. As a result of the analysis, the positive effect of the implementation of unsteady waterflooding technology was revealed, and recommendations for improving its application at other operational facilities of oil fields were given.