Abstract
A high performance technology has been developed for unstable waterflooding of layered-heterogeneous producing reservoirs of oil fields with a thermal gradient. The technology is based on cyclic injection of a thermoactive low-viscosity oil-soluble liquid polymer composition into the formation, which passes into a high-viscosity phase in situ, blocking the produced formation water flow. Application of the technology results in the increase of area of stimulation, both along the strike and vertical sweep efficiency. Monitoring the reservoir filtration characteristics enables control of the profile of the mixture advance in the formation. The effect of unstable injection of the proposed thermoactive polymer composition on the residual resistance factor was studied in an experimental setup consisting of two parallel-connected linear reservoir models with different permeability. The composition contains a working agent, a dispersant and sea water. The optimal ratio of the components that make up the composite mixture was determined as a result of laboratory and experimental studies. The viscosity behavior of the composite mixture at different temperature values for reservoir conditions is determined. Monitoring techniques for reservoir filtration properties have been developed in order to control the flow profile of the mixture in the reservoir. The analysis of the obtained results showed the efficiency of this technology for layered-heterogeneous reservoirs with a thermal gradient and the availability of overflows. This technology enables aligning area of stimulation, both along the horizontal and vertically using smaller volumes of the agent and with a slight change in the injection pressure. Unstable injection of the composite system provides a significant additional removal of residual oil. Thermoactive polymer composition should be injected cyclically in order to increase the reservoir coverage, align the frontal advance and for enhanced oil recovery due to the involvement of low-permeability oil-saturated areas into the development. This method allows you to change the direction, flow rates, and create unsteady cyclic pressures. A redistribution of formation fluids, a decrease in capillary pressures and the flow of a working agent into oil-saturated low-permeability zones occurs under the positive and negative pressure drops in the formation. The proposed technology was implemented in the section V of the block of the «Neft Dashlary» field (X horizon) in April-June 2016 and in the section of the «Pirallahi» field (KSw) in February-March 2017. At the pilot site of the «Neft Dashlary» field, the impact effect continued until May 1, 2017. Additional oil production in the period from 01.05.2016 to 01.05.2017 made up 3201.4 tons. Additional oil production at the selected area of the Pirallahi field by the end of 2017 made up 170 tons.
