The Kaji-Semoga fields in South Sumatra, Indonesia, are mature, waterflooded oil fields with ESP's in more than half the wells. To minimize oil deferment due to down-hole ESP problems, an ESP-gas lift hybrid was implemented in 2009. The idea was to install gas lift as a backup so the well could be kept on production, albeit at reduced rate, until the ESP could be serviced or replaced. During the period 2011-2012, 97 wells had the hybrid lift system installed and ESP problems occurred 23 times in these wells. The availability of the ESP-gas lift hybrid minimized oil deferment and allowed approximately 24,000 bbls of oil to be produced while waiting for the ESP to be serviced or replaced. However, the previous hybrid design used just a single gas lift valve as an unloader and injection point. Performance analysis of the previous design showed that the gas lift performance could be optimized if the injection point was, on average, about 300 feet deeper. But that would be too deep for unloading, so the gas lift hybrid system was redesigned by incorporating two gas lift valves, one a shallower unloading valve and the other a deeper injection valve. Between April 2013 and March 2014, twenty-four wells had the redesigned ESP-gas lift hybrid installed. Performance analysis of the design was conducted at KS-XXX well when it had an ESP down-hole problem. After the redesigned gas lift was activated, it increased drawdown by 121 psi compared to the previous design, kept the liquid lifting to 57% of ESP production rate (compared to 25% of ESP production rate with the previous gas lift hybrid design) and minimized oil deferment leading to 540 bbls of additional oil production in this one instance. Analysis of the overall performance of the redesigned ESP-gas lift hybrid is onging, but results are similarly good.

Continuous gas lift system is currently widely used as artificial lift in Kaji-Semoga Field, in fact at about 46% of total producing wells. The average depth of gas lift wells in Kaji-Semoga is 3,200 ft, utilizing 2 to 5 conventional gas lift valves in a single production string. Common problems experienced when optimizing gas lift wells in Kaji Semoga field are instability of flow due to fluctuation of gas lift injection rate and pressure, limited gas injection volumetric rate, and limited compressor discharge pressure that leads to limited casing head pressure at well head, especially for remote wells with high tubing pressure at injection point.A new injection valve type, venturi orifice gas lift valve with breaking-out gas device, has been studied and proposed as a solution to the aforementioned problems. This type of valve has been installed as gas lift injection valve at some pilot wells by using slick-line unit. The aim of venturi orifice is to reduce pressure difference between casing (upstream) and tubing (downstream) at injection point and to deliver a greater amount of gas lift injection at the same casing head pressure (compared to traditional orifice valve). Meanwhile, the aim of the breaking-out gas device is to break the injected gas into very small bubbles and homogenize with the liquid so that flow stability can be achieved.Selected candidates for pilot wells are the ones with high productivity index (PI), high flowing pressure gradient (above 0.18 psi/ft) and limited gas lift manifold pressure. Well modeling and simulation have been conducted for these selected wells using production optimization software to predict gas lift well performance after installation of new injection valve, whereupon the simulation result is matched with actual data.Applying venturi orifice gas lift valve has produced successful results: the liquid rate of the pilot wells has increased by about 40%, with 30% gas injection rate increment under the same conditions. Computer simulation also provided similar results to the actual well performance and met expectations. The pay-out time (POT) of this project was less than 2 days.

<em>The gas lift lifting system is widely used as an artificial lift on the X Field, with an average depth of gas lift production wells of 3,000-3,500 ft. Design of 3 to 5 Gas lift Valves (GLV) designwith size of 1 inch is ussualy applied. While at the point of gas injection, the GLV square edge orifice is applied. The problem in the optimization of gas lift wells is the flow instability due to gas flow rate fluctuations, the limited volumetric gas injection and limited gas compressor pressure. With the limited compressor pressure, the lift flow and gas design speed is very dependent on the amount of pressure on the compressor, the production wells with limited injection pressure will result in a limited amount of gas injection, the square edge orifice requires a pressure difference of 40% to achieve the maximum gas flow rate. This study aims to find the modification of the GLV orifice geometry to improve the efficiency of the gas lift system so that it can get optimal production. This GLV design modification includes changing the GLV orifice geometry. Design studies using Computational Fluid Dynamic (CFD) simulations aim to analyze any changes in GLV geometry design to the performance of the gas flow rate in the orifice valve described in the valve performance curve. The design modification approach is in accordance with the GLV venturi orifice geometry and the availability of equipment for GLV modification. The CFD simulation results of the first modification geometry by increasing the orifice diameter from 0.25 to 0.5 inch with the condition of upstream 650 psig and downstream 625 psig pressure increasing the injection gas flow rate capacity by 355% and modifying the second geometry with the venturi orifice form by 280%. In modifying the shape of the orifice venture to reach critical flow requires a pressure difference of 10%. Based on simulation results, the modified orifice application is able to increae production up to 44%.</em>

No abstract

Sistim gas lift digunakan sebagai artificial lift di lapangan XXX, dengan kedalaman rata-rata sumur produksi gas lift sebesar 3.000-3.500 ft. Menggunakan desain 3 hingga 5 Gas lift Valve (GLV) dengan ukuran 1 inch. Salah satu permasalahan pada optimasi sumur gas lift adalah, terbatasnya jumlah gas injeksi yang dapat diinjeksikan akibat keterbatasan tekanan compressor. Penelitian ini bertujuan untuk mencari modifikasi geometri GLV untuk meningkatkan efisiensi sistim gas lift sehingga dapat mendapatkan produksi yang optimal. Modifikasi desain GLV ini mencakup perubahan geometri orifice GLV. Kajian desain dengan menggunaan simulasi Computational Fluid Dynamic (CFD) bertujuan untuk menganalisis setiap perubahan desain geometri GLV terhadap performance laju alir gas di dalam GLV yang digambarkan dalam valve performance curve. Pendekatan modifikasi desain sesuai dengan geometri venturi orifice GLV dan ketersediaan peralatan untuk melakukan modifikasi GLV. Hasil dari simulasi CFD modifikasi pertama dengan meningkatkan diameter orifice dari 0.25 inch ke 0.5 inch dengan kondisi tekanan upstream 650 psig dan downstream 625 psig meningkatkan kapasitas laju alir gas injeksi sebesar 355% dan modifikasi kedua dengan bentuk orifice venturi  sebesar 280%. Pada modifikasi bentuk orifice venturi untuk mecapai laju alir gas injeksi maksimal membutuhkan perbedaan tekanan sebesar 10%. Dengan optimasi peningkatan kapasitas laju alir injeksi dari hasil Simulasi menunjukan potensi kenaikan produksi sumursebesar 44.9%.