In Poland there are approximately 60 oil fields located in different geological structures. Most of these fields have been producing for several years to several dozen years, and now require redefining of the development plan by utilizing an improved oil recovery (IOR) or enhanced oil recovery (EOR) method to achieve a higher oil recovery factor. Here we present the redevelopment plan for the Polish Main Dolomite oil field, that aimed to optimize and maximize the oil recovery factor.

Considering all available geological and reservoir data, both a static and dynamic model were built and calibrated for three separate reservoirs connected to the same production facility. Then the comprehensive study was performed where different development scenarios was considered and tested using reservoir numerical simulation. The proposed redevelopment scenarios included excessive gas reinjection to the main reservoir, additional high-nitrogen (N2) gas injection from a nearby gas reservoir (87% of N2), carbon dioxide (CO2) injection, water injection, polymer injection, water-alternating-gas (WAG), well stimulation, and a combination of these methods. Development plans assumes also drilling new injection and production wells and converting existing producers to gas or water injectors.

The key component in development scenarios was to arrest the pressure decline from the main field and decrease the gas/oil ratio (GOR). An additional challenge was to implement in the simulation model all key assumptions behind various development scenarios, while also taking into account specific facility constraints and simultaneously handling separate reservoirs that are connected to the same facility, and hence affecting each other.

From numerous scenarios, the scenario that requires the least number of new wells was selected and further optimized. It considers the drilling of only one new producer, one new water injector, and conversion of some currently producing wells to gas and water injectors. The location of the proposed well and the amount of injection fluids was optimized to achieve the highest oil recovery factor and to postpone gas and water breakthrough as much as possible. The optimized case that assumes low investments is expected to improve incremental oil production by 90% over No Further Actions Scenario. However, the study suggests the potential of more than tripling incremental oil production under a scenario with considerably higher expenditures. The improved case assumes drilling one more producer, four new water injectors, and injection of three times more water.

The presented field optimization example highlights that in many existing Polish oil fields there is still a potential to reach higher oil recovery without considerable expenditures. However, to obtain more significant oil recovery improvement, higher capital expenditure is necessary. To facilitate the selection of the best development scenario, a detailed economic and risk analysis needs to be conducted.

You can access this article if you purchase or spend a download.