Abstract
Most of oil fields are developed on waterflooding. In some regions there are many fields with strong water drive. In both cases oil production is accompanied by water production.
From economical point of view income is proportional to oil production but operating expenses are proportional to liquid production. So, excessive water production can decrease profitability of a project. In some economical software there is a dependency of watercut upon oil displacement. But in reality foregoing dependencies are drastically different from field to field. This paper is devoted to finding regularities and confirmation them by means of analytical and numerical calculations.
Several influencing parameters are considered – such as relative permeabilities, fluid viscosities, fluid densities, heterogeneity and permeability profile, permeability anisotropy, layer slope, fractures, aqufer size and activity, well distance and patterns, position of perforation intervals, pressure drawdown, maximum allowed watercut. Those factors could be divided into two global groups – geological and technological.
Ultimate fraction of mobile oil displaced (volume sweep efficiency) depends on many factors. That is why field ultimate recovery factor is always less then laboratory displacement factor. But even laboratory waterflooding experiments show wide range of watercut vs. sweep dependencies for core samples from the same field. For the same maximum watercut (e.g. 98%) we can get from 0.6 to 0.9 sweep.
The quantity of water produced per unit of produced oil depends both on geology and technology. It's impossible to change geological environment but we can chose a proper method to develop any field. Field examples and practical recommendations are presented in the paper.
