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Pump Capacity Determination For Two-phase Vertical Fluid Flow
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CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF STUDY
In the production system, Pressure drop has been a major issue in the field. These pressure drops could be experienced as a result of valves and fittings
installed, due to friction along pipe sections or in lifting fluid up to a certain level.
As these pressure drops are identified, and the economic flow rate of a reservoir fluid is known, pumps may be employed to reduce the effect of pressure drop and maintain a given fluid flow rate for good economic recovery. These pump applications are usually analysed to determine an optimum Hydraulic pump requirement for a given fluid system and pipe diameter. It can form one of the basic aspect to be considered during well completion in selecting production tubing diameter.
In general, a pump is a device used to transport liquids, gases, and slurries. However,the term pump is usually used to refer to liquid handling equipment. The purpose of the pump is to provide a certain pressure at certain flowrate of a process stream. The pressure requirement is dictated by the process andpiping involved, while the flow rate is controlled by the required capacity in thedownhole units.
At least one out of every 10 barrels of oillifted in the world’s oil and gas operations are produced using an ElectricSubmersible Pump (ESP). Typical installationsproduce liquids in the 2,000 to 20,000 bpd range,making the ESP an effective and economical meansof lifting large volumes of fluids from great depthsunder a variety of well conditions.
There are several types of pumps used for liquid handling. However, these can bedivided into two general forms: positive displacement pumps (including reciprocatingpiston pump and the rotary gear pump), and centrifugal pumps. The selection of thepump type depends on many factor including the flow rate, the pressure, the nature ofthe liquid, power supply, and operating type (continuous or intermittent).
The power requirement for a mechanical system, like pumps and compressors, isgiven by the general mechanical balance equation:
P = -mWs = m 1.1
All terms in this equation take their normal meaning with m being the mass flow rate,and α a coefficient used to take into account the velocity profile inside the pipe (forlaminar α = 0.5, while for turbulent α = 1). The required work (or power) given by Pis the total work that needs to be delivered to the fluid. This work will be drawn froma motor (operated with electricity or engines). The conversion between the motor andpump power is not complete and an efficiency is defined to describe the powerconversion. The efficiency is given by: 1.2
The input power can be measured from the source. For example, if the pump is
operated with electricity, the input power will be I×V (current times voltage). Theoutlet power can be determined using Equation (1.1).
1. Static head (Δzterm): the height to which the fluid will be pumped.
2. Pressure head ( term): the pressure to which the fluid will be delivered (ina pressurized vessel for example). The pressure units must be converted to lengthunits using relation.
3. System or dynamic head (F term): the energy lost due to friction in pipes, valves,fittings, etc.
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