Environmental Issues of Transient Behavior

Abstract

We are currently witnessing a high-rate of exploitation of oil fields at the stage of declining production. This decline is a result of the depletion of oil fields, which leads to the use of electric submersible centrifugal pumps (ESP) with dynamic head below saturation pressure. In this operating mode, the ESP’s efficiency deteriorates, leading to the overheating of its working elements during operation. The boiling of water contained in the wellstream and salt deposition can take place in an overheated pump. This, in turn, can lead to a premature failure of the centrifugal pump and reduce the economic viability of this oil production method. To eliminate premature failure, such units must be transferred to an operating mode with periodic shutdowns. Yet, the planning of trip-out and restart time schedules is performed in the absence of a proper theoretical justification. Such planning often leads to ESP failures due to the reduction of the electric resistance of cable lines or salt deposition. To prevent salt deposition, oil production companies use different chemicals, which are pumped into the hole annulus and are expected to stop salt deposition when propelled into the pump pot. Chemical treatment practice shows that these reagents perform poorly and may not prevent salt deposition at all. In reality, chemical compounds can damage downhole equipment and its structural elements. Long-term use of these reagents may lead to ecological disaster – the contamination of productive formations and confined groundwater beds. This work investigates the possibility of ESP operation in periodic mode without salt deposition and the exploitation of oil fields without the application of chemical reagents. The development of a periodic operation method allowing for ESP operation without salt deposition could eliminate the use of reagents in oil production and thereby reduce the risk of ecological disasters.