DESIGN, OPTIMIZATION AND ECONOMIC ANALYSIS OF CRUDE OIL PRODUCTION IN GAS LIFTWELLS OF A WATERFLOOD RESERVOIR

Abstract

Waterflooding is geared towards maintaining the bottomhole pressure profile of reservoirs to maintain a significant production level. It dictates the Inflow Performance Relationship, a graphical representation of the Bottom Hole Pressure plotted against the flow rate. However, due to constraints in the fluid properties and dynamics of the wellbore, not all of these flow rates can be delivered to the well surface and one of the underlying reasons is the density of the fluid column. Artificial    Lifting then comes in to increase the Vertical Lift. One of which is Gas Lifting- reinjection of produced gas to lighten the fluid column.  This lowers the VLP Curve as a smaller bottom pressure value can now be used to deliver a higher production. The intersection of the VLP and IPR Curves then shows us the expected production flow rate and bottom hole pressure.  However, there exist a limiting GLR where the decrease in the hydrostatic pressure will be offset by an increase in the frictional pressure drop and this places a caveat on the limit of Gas that can be injected into the well Columns as increasing flowing GLR would result in a reduction in BHP, hence a limiting GLR where the decrease in density will be offset by an increase in the Frictional Pressure Drop. This then beckons the Analyst to use the PROSPER software to arrive at some modifications and suggestions to increase production. For this, an onshore region well, named herein as Well Alpha was modelled both with a GL design and a Natural Flow.  Alpha with a Top node pressure of 200psig, water cut at 22% and Total GOR of 445 scf/STB and with the implementation of the Gas Lift, the sensitivity analysis on GLR shows the possibility of increasing the production by 40%. The Economic Analysis carried out using MATLAB showed that it is economically viable at a discount rate of 8 %, Inflation rate of 3%, oil price of $40 amongst other economic parameters and there exists a greater return on investment.