Challenges of Installing ESP in Natural Flow Wells

Abstract

In natural flowing wells, the energy source is the reservoir pressure. The pressure that makes the oil flow from the reservoir to the bottom of the well is known as the flowing bottom hole pressure. When bottom hole pressure is relatively high, the pressure can raise the oil to the wellhead, and even into the gathering manifolds and the separator, with time the reservoir pressure depleted gradually which will decline the natural flow rate, when the rate becomes less than the commercial rate the artificial lift method will be used to overcome losses in reservoir pressure. Electrical submersible pump (ESP) is one of the most efficient artificial lift methods used in the oil industry for lifting moderate to high volume of fluids from wellbores to surface, proper sizing and selecting of the ESP system mainly depends on accurate data especially that pertaining to the well’s capacity, if the given data is not accurate then the design will usually be marginal and lead to premature failure. Here we present cases of premature failures in electrical submersible pump (ESP) system due to natural flow and suggest approaches to minimize the effects of natural flow on the ESP system. Natural flow was the root cause of premature failure with direct impact on ESP components for fourteen wells, and the effect of natural flow on ESP components has been classified into two cases: ESP pump failure due to the natural flow force. ESP power cable failure due to Erosion/Corrosion. Using Dismantle, Inspection and Failure Analysis (DIFA) reports and history of target wells in this study, we will analyze the data for each case separately to get conclusions and recommendations to deal with the effects of natural flow on ESP components. In the first case, diverting oil flow through ESP system while the well is naturally flowing might damage internal components of the ESP pump in case the flow rate is more than capacity of the pump, or even keeping the pump running out of recommended operating range (ROR) will lead to pump premature failure. In the second case in harsh environments like natural flowing wells with high amount of free gases and corrosive due to sour gases, the right selection of ESP cable is critical and the proper choice of its type in many cases has a direct impact on the life of the ESP installation, which will be proven in the conclusion of the second case. Based on the conclusions for each case, this paper will provide recommendations to minimize the effects of natural flow on ESP system to avoid premature failures for such cases.