Gas lift optimization utilising automation gas lift valve

Abdalsadig, M 2017, Gas lift optimization utilising automation gas lift valve , PhD thesis, University of Salford.

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Gas lift is one of the most common forms of artificial lift, particularly for offshore wells. This is due to its relative downhole simplicity, flexibility, reliability, and ability in operating over a wide range of flow rates with the limited well head space. Generally, Gas lift optimization can reduce the operating cost with increase in the Net Present Value (NPV) and maximization of the recovery from the asset.

All of the previous researches have reported that conventional gas lift technologies’ designs have limitations on gas lift valve. Nonetheless, traditional gas lift technologies that were designed and developed in 1950’s do not have resistance when subjected to high temperature and high pressure in subsea wells. This therefore unable the flows of the gas lift to be coherently controlled. Moreover, gas-lifted oil wells can lead to failure unless a smart gas lift valve unit is used in the controlling the amount of the gas inside the tubing string.

In this study, an automation gas lift valve unit with the corresponding control line was experimentally simulated on a dedicated apparatus. This enables real-time data on the gas lift valve to the surface to be demonstrated and accordingly analyzed. Under the conventional method of practice the injection pressure of the gas is normally used in operation of the valve. Whereas in this investigation the port size of the gas lift valve was remotely adjusted from the assumed surface using the apparatus. A devoted computer program LabVIEW was also used in determination of the gas passage through the smart gas lift valve, thus distilling the real time data. The results have shown those optimizations are achievable at high gas injection pressure when 87 psi is used and when the valve is 15% open (or 0.95mm port size diameter). Also, the wellhead pressure reaches to the minimum value of 0.9 psi in which high-pressure drop between the reservoir pressure and the top surface will occur.

Throughout this investigation, water was used as a working fluid since the column of corresponding water in petroleum production tubing has the highest hydrostatic pressure of 2.8 psig compared with crude oil. Hence, during the gas lift process crude oil will be less cumbersome to produce than water.

The results present the maximum production rate of 18.3 lit/min (with 83% improvement on production) could be achieved. The results obtained experimentally were also used in constructing an economic analysis from the use of smart gas lift valve for different scenarios namely: (i) in gas lift natural flow and (ii) the gas lift wells. It was demonstrated that the flow rate can be enhanced from 91bbl/day to 166.5 bbl/day for the gas lift natural flow, and from ‘Zero’ (or non-production) to165.6 bbl/day for the gas lift well. Based on these results, the NPV of the gas lift natural flow will be approximately $2793 on $37 per barrel and for the gas lift well will be about $6127.2

Item Type: Thesis (PhD)
Schools: Schools > School of Computing, Science and Engineering > Salford Innovation Research Centre
Date Deposited: 19 Feb 2018 16:02
Last Modified: 27 Aug 2021 20:45

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