In view of the world’s reserves depletion for conventional oil, the more focus is given to, so-called, unconventional sources of hydrocarbons, where the high-viscosity oil fields holds the special place. Firstly, this is due to the fact of genetic relations of high-viscosity oil to the traditional reserves, and secondly, to the tremendous discovered world’s reserves, which exceed the residual conventional oil reserves by times.
The article takes the high-viscosity oil field to show that the long development without the reservoir pressure maintenance leads to a significant decrease of the reservoir pressure. Reduction of the bottomhole pressure below the bubble point pressure is clearly visible in the producing wells. These processes lead to a necessity of converting the most wells, equipped with the electric-centrifugal pumps, to the cyclic mode, resulting in drops of the monthly average oil production. Initial recoverable reserves estimation for the development without the reservoir pressure maintenance proved that the developed recoverable reserves are within 26% from the designed values. It is shown that the efficiency of applying the reservoir pressure maintenance system during the high-viscosity oil field development significantly depends on commencing the injection wells system. The submitted calculations on the geological-hydrodynamic model demonstrated that the commencement of the pressure maintenance system under reservoir pressures of 60-70% from the initial values, allows achieving the designed recovery factor, while the consequent hold of injection system commencement leads to losses in the initial recoverable reserves. Within the pressure range 0.6-0.3 from the initial reservoir pressure, almost the linear dependency is observed, which later changes to a rapid decrease of recovery factor with the reduction of the “start” pressure. Therefore, the late deployment of the pressure maintenance system threatens by the significant losses of the high viscous recoverable reserves.
References
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