Russkoye field, discovered in 1968, is a giant high-viscous oil field located above the Polar Circle in Russia. The commercial development of the field has been a tremendous challenge due to several factors such as a very complex heterogeneous shallow reservoir with a large gas cap, an active bottom aquifer, unconsolidated sands, low temperature, and permafrost zone. At this stage, the development of the field is still on the pilot testing stage in order to understand and evaluate different possible development strategies that assure the maximum recoverable reserves for this kind of field.
As part of the development strategy, eight water injection pattern schemes including horizontal and vertical wells, and different well spacings were simulated to find the optimal waterflooding patterns, and to evaluate different well trajectories, and different injection bottomhole pressures, for the next pilot area.
The water injection pattern schemes evaluated were horizontal wells line drive, 7-spot, 7-spot inverted, 9-spot, 9-spot inverted, 5 spot, combined line drive with horizontal producers and two deviated injectors, and combined line drive with horizontal producers and three deviated injectors.
The complete analysis was carried out on the basis of the technical results and the economical evaluation. Several parameters were studied to compare performance and efficiency of different water injection patterns, such as voidage replacement ratio, cumulative oil, water and gas, production profiles, sweep efficiency, injected pore volume, and reservoir pressure behavior. The optimization of the four well spacings between 100 m and 400 m and the injection bottomhole pressure range was performed using an analytical approximation. The economical evaluation for each water injection pattern analyzed was executed by means of the economical standard analysis: net present value, internal rate of return, profitability index, lifting cost, and payback period.