Article outline

Purpose:

Monitoring and optimization of periodical regime of oil wells, which are operated by sets of electrical submersible pump, by the help of mathematical modeling methods

Methodology:

To describe multiphase flow in the reservoir and well elements (casing, tubing, annulus) the quasi-stationary model is suggested to use as an alternative to non-stationary model. This enables to accelerate the duration of optimization calculations without losses in computational accuracy

Findings:

1) The problem of spreading of disturbance in multiphase flow in round tube is studied. Three characteristic time stages of non-stationary solution are highlighted

2) The comparison of results of calculations of non-stationary and quasi-stationary models for describing of multiphase flow in well elements is done. It is obtained that the quasi-stationary model shows error of calculation of the main parameters of the problem (averaged and extreme during one periodic cycle of pumping/accumulation values of liquid rate, well flow pressure, dynamic level) of about 1% compared with non-stationary model

Conclusions:

1) By the model examples (part of a tube and oil well) it is shown that the influence of non-stationary effects in multiphase flow in tubes with reference to the problem of periodic operating of oil well by electric submersible pump is minimum and non-stationary model of the well in such problems can be replaced by quasi-stationary without losses in solution accuracy

2) For practical use it is advisable to switch from the solution of partial differential equations to the simplified correlations like Beggs-Brill or Ansari to calculate the pressure drop in tubes, which is solved by explicit numerical methods