Kaji-Semoga (KS) field, a mature field located in South-Sumatra, requires more efficient production operation to reduce production lifting cost. Since 2008, KS field has been experiencing gas shortage due to the decline in associate gas production. As a result, some of the gas lifted producer wells need to be converted to another type of Artificial Lift (AL). After various studies and trials, it was concluded that ESP (Electrical Submersible Pump) was the most suitable alternative. Currently, the AL system is dominated by ESP with total deployment 140 of 190 producing wells, contributing 70% to the field's overall oil production, i.e. a total of 9,500 BOPD. Furthermore, KS field purchases gas as fuel for the electricity system, which is mainly consumed by AL. Therefore, efforts have been made to evaluate and obtain significant cost reduction in power consumption of ESP through power efficiency assessment and feasibility of new technology implementation. Power efficiency assessment for ESP application becomes a promising attempt to reduce ESP power consumption. Components which mostly affect the power consumptions are pumps and motors. With this understanding, technology selection of ESP has been carefully determined to obtain significant result in power efficiency. Permanent Magnet Motor (PMM) is one of the ESP technologies that offers higher efficiency, higher power factor, greater power density and wider operating speed compared to conventional induction motor (IM). Short term field trial PMM ESP application has been conducted. Field-testing procedures and measurements on power consumption are presented both for PMM and existing IM at identical condition (head generated, motor rating, pump type & fluid rate). It yielded conclusive result that PMM has higher power efficiency. Thus, a wider application is justified and expected to have substantial energy savings and cost reductions. Currently, PMM is utilized at 20% of ESP wells in KS field. Field observation of these PMM-ESP units revealed power efficiency improvements by as much as 10-30% compared to IM ESP units. This improvement has led to the reduction of fuel gas consumption, which we have estimated to potentially save the company almost $ 750,000 per year in power generation expenditure. In the future, all IM ESP are planned to be replaced by PMM to gain higher cost reduction.
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.
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.
Hydraulic fracturing has been established as one of production enhancement methods in the petroleum industry. This method is proven to increase productivity and reserves in low permeability reservoirs, while in medium permeability, it accelerates production without affecting well reserves. However, production result looks scattered and appears to have no direct correlation to individual parameters. It also tend to have a decreasing trend, hence the success ratio needs to be increased. Hydraulic fracturing in the South Sumatra area has been implemented since 2002 and there is plenty of data that can be analyzed to resolve the relationship between actual production with reservoir parameters and fracturing treatment. Empirical correlation approach and machine learning (ML) methods are both used to evaluate this relationship. Concept of Darcy's equation is utilized as basis for the empirical correlation on the actual data. The ML method is then applied to provide better predictions both for production rate and water cut. This method has also been developed to solve data limitations so that the prediction method can be used for all wells. Empirical correlation can gives an R2 of 0.67, while ML can gives a better R2 that is close to 0.80. Furthermore, this prediction method can be used for well candidate selection means.
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