Flooding usually means pumping water into an oil reservoir in order to maintain formation pressure and push oil to the bottom of the well. This process requires the use of pipelines that operate under high pressure and thus have a large reserve of unused energy. The scientists from Perm Polytechnic University have proposed using this potential via energy recovery, i.e., recovering and reusing it.
The technology is as follows: the surface facilities are equipped with a system, in which water and oil are mixed and energy is recovered. The active medium is the liquid from the reservoir pressure maintenance system, and the passive medium is the water-oil emulsion obtained from the installation’s oil pipeline. This makes it possible to reduce pressure in production wells, improve the reliability of submersible equipment and decrease the number of equipment failures. After carrying out mathematical modeling, the scientists came to the conclusion that the efficiency of the technology improves with a bigger nozzle diameter: the optimal diameter is 4 mm, with pressure at the inlet of the active medium hovering between 8 MPa and 11 MPa.
The next stage of the study involved oil well tests, which were conducted in three operating modes that differed in water flow, water pressure at the pump inlet, as well as the phase ratio and nozzle diameter. Tests conducted with a nozzle diameter of 4 mm and an active medium pressure of 8 MPa showed that a water flow of 69.6 cubic metres per day allows the systems to reduce pressure by 0.1–0.3 MPa (depending on whether the annular valves are open or closed). This, in turn, makes it possible to increase the additional volume of oil by more than 5%.
“Based on the data obtained, one can note that by reducing the pressure on the installation by 0.3 MPa, it is possible to obtain an additional oil flow rate of 3.48 tons per day. This means that the new technology can be considered efficient. From the results obtained, we found that the proposed system can reduce linear pressures in wells if the operating conditions are chosen correctly,” Aleksandr Lekomtsev, associate professor at the Department of Oil and Gas Technologies, is quoted as saying by Perm Polytechnic University.
