SPE-176195-MS Coiled Tubing Gas Lift Design and Troubleshooting - Case History [PDF]

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SPE-176195-MS Coiled Tubing Gas Lift Design and Troubleshooting - Case History I Ketut Oscar Edy, Danang N. Wicaksono, Reza Saputra, and Ferry Anantokusumo, VICO Indonesia



Copyright 2015, Society of Petroleum Engineers This paper was prepared for presentation at the SPE/IATMI Asia Pacific Oil & Gas Conference and Exhibition held in Nusa Dua, Bali, Indonesia, 20 –22 October 2015. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright.



Abstract VICO Indonesia is an Oil and Gas company which has operated mature fields located in the onshore part of East Kalimantan which has been on production for over 30 years. The fields are dominated by gas reservoirs with a much lower presence of oil reservoirs. Production mechanisms cover from natural depletion to weak and strong water drive, particularly in some of the shallow areas. Recent well completions include single and dual slimhole monobore. The field is a perfect combination of stratigraphic and structural traps with more than 4000 sandstone reservoirs where around 450 of those are oil reservoirs. The oil recovery factor for these reservoirs is in the range of 10-30%. Oil development in this fields performed using gas lift as the main artificial lift while several wells still flowing naturally. Coiled tubing gas lifted (CTGL) wells contributes to 60-80% of current oil production of 8000 BOPD. Totally, 50 CTGLs have been installed in VICO Indonesia where most of those considered successful. The main problem found related with initial operation after installation. Lesson learned has been summarized including the design and the procedure for initial operation. Coiled tubing gas lift design and troubleshooting are rarely found in literature. Thus, this paper presents the detail step by step design and how to troubleshoot the possible failure during early operation. This approach exhibits a real benefit to recover more untapped hydrocarbon with more aggressive program.



Introduction VICO Indonesia is the operator of the Sanga-Sanga Production Sharing Contract located onshore of the Mahakam delta, East Kalimantan, Indonesia since 1968. The fields are dominated by gas reservoirs with a much lower presence of oil reservoirs. Over 30 years the PSC has only produced 28% of the estimated original oil in place. VICO has 7 producing fields (Badak, Semberah, Nilam, Lempake, Mutiara, Pamaguan and Beras) as depicted in Figure 1, in a complex fluvial deltaic deposition with more than 4000 gas and oil reservoir, mixed of depletion and water drive mechanism reservoir. Oil deposit found on shallower depth, while on deeper depth mostly gas. As a major gas producer, gas lift is the most suitable artificial lift for Vico given the adequate volume of gas availability. Former completion design included the application of gas lift mandrels in a single or dual selective completion named as conventional gas lift. However, evolution has been made on completion design to address the nature of the reservoir, accelerating production, and considering



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Figure 1—Sanga Sanga PSC (after Wijanarko et al. 2012)



flexibility and cost. These recent completions known as single and dual monobore slimhole are not favorable for conventional gas lift. These slimhole completions are suitable with the application of coiled tubing gas lift (CTGL). The evolution of completion types in VICO are depicted in Figure 2.



Figure 2—Well completions evolution (after Wijanarko et al. 2012)



Totally more than 50 CTGL has been installed in VICO and many more will be installed in the future as the most favorable artificial lift. At the moment, CTGL wells are contributing to 60-80% of current oil production and successfully maintaining oil production.



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Completion Types A new completion type called monobore completion was installed in VICO since 2005. This completion is a new solution in completing multi-layer reservoir to optimize reserve recovery and reduce drilling cost. Since then this completion has become the most common completion in VICO. There are more than 500 wells drilled and completed using this type of completion to date. The monobore wells use single or dual production tubing cemented to surface. Dual Monobore completion well is using 3-1/2⬙ tubing diameter while single monobore is using 3-1/2⬙ or 4-1/2⬙ tubing. These tubing sizes give difficulties on implementing downhole pump lift because of its limited diameter. The typical configuration of these completions can be seen in Figure 2.



Coiled Tubing Gas Lift Prior to 2010, conventional gas lift is the only artificial lift used in Vico’s oil wells. Since the wide implementation of monobore completion, CTGL is the most suitable and common practice for these completion. CTGL uses 1,5⬙ coil tubing inserted into the monobore well. The bottom-hole-assembly of CTGL consists of coiled tubing connector, nipple, check valves, centralizer, and nozzle. The coil tubing is hanged above the wellhead using special coil tubing hanger which then connected to gas lift line. The gas is injected through coiled tubing then mix with reservoir fluid and flow to surface through annulus between tubing and coil tubing. The typical installation of CTGL is shown in Figure 3.



Figure 3—Coiled tubing gas lift typical installation (after Wijanarko et al. 2012)



Coiled Tubing Gas Lift Design. Coiled tubing gas lift is a single point injection gas lift without unloading valve. Thus the objective of the design is to define the deepest possible injection with the available injection pressure. During design, two most important things need to be considered are: 1) Ensure the injection pressure is sufficient to kick of the standing liquid at the point of gas injection. 2) Ensure pressure drawdown exist given the desired tubing head pressure and the flowing gradient. In the case of no drawdown, it can be considered to install intermittent gas lift application.



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Design procedure can be described as the following steps: 1) Perform bottom hole pressure (BHP) survey, both static and flowing then plot the result. 2) Start from maximum available injection pressure at surface (Pkick-off), compute a maximum injection pressure line. 3) Start from Pkick-off - ⌬Pvalve at surface, establish a design injection pressure line parallel to the maximum injection pressure line; where ⌬Pvalve is pressure drop across valve and can be taken as 100 psi. 4) Define the point of injection from the intersection between design injection pressure line and BHP result. This will ensure that the kick-off procedure can be done. 5) Perform nodal analysis to estimate gas injection rate and the oil rate. This should honor the desired wellhead pressure and reservoir pressure (ensure the drawdown). The design procedure is illustrated in the following figure.



Figure 4 —CTGL design procedure and the pressure relationship



Pressure Data Acquisition. Bottom hole pressure survey, both flowing gradient survey (FGS) and static gradient survey (SGS) need to be acquired prior to CTGL design. The data is required to define the point of injection and to estimate drawdown pressure. Failure to obtain representative BHP data could result in kick-off failure. Below is the proposed procedure for BHP data acquisition to minimize the risk of kick-off failure: ● ● ● ●



Open the well to the system Perform FGS under stable condition (do not open the well to atmospheric prior or during FGS) Shut in the well Run SGS



Either FGS or SGS can be used for CTGL design. However, FGS is more recommended since it will give deeper injection depth in most cases. Troubleshooting. The preparation prior to well reactivation is very important. Based on experience, the most failure during reactivation is the effect of failure during preparation (i.e. plugging in nozzle due to debris from welding).



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Below are procedures for CTGL reactivation: 1) 2) 3) 4) 5) 6)



Clean up or flush the gas lift line and gas lift skid to ensure no debris left from welding work Shut in the well Inject the well with maximum available pressure while in shut-in condition Open the well to the system If kick of fail then re-do step 2-3 then open the well to atmospheric pressure If step 5 fails to kick off the well, then: a. Shut-in the well b. Pressurize the well by injecting gas lift pressure to annulus between coiled tubing and tubing until pressure in annulus equal with pressure in gas lift system c. Inject the well with max injection pressure while in shut in condition d. Open the well to atmospheric system



7) If kick-off still fail, then use nitrogen to kick-off followed by gas lift injection by using gate valve 8) After kick-off, reduce and adjust the injection pressure to get optimum rate The common problem on CTGL reactivation in VICO related with kick-off failure and nozzle clogged by debris. While the first problem can be solved with the procedure given above, the later problem required another well intervention. Result. More than 70 CTGL have been installed in VICO Indonesia since 2010. Prior to the introduction of CTGL, conventional gas lift is the only artificial lift used in VICO’s oil wells. Since the wide implementation of monobore completion, CTGL is the most suitable and common practice for the completion. The figure below shows the contribution of CTGL in the production since early 2014.



Figure 5—Vico oil production (Jan 2014 – May 2015)



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Summary 1) Coiled tubing gas lift is a proven and effective artificial lift in monobore completion. This method is fit for purpose with recent and most completion configuration in Vico. 2) The determination of point of injection is very important to ensure both kick-off and drawdown pressure. 3) The preparation prior to well reactivation takes a critical part to ensure no failure during operation. 4) CTGL has a big role in sustaining oil production in Vico. CTGL wells are contributing to 60% of current oil production.



References Arianto, M. A., Susatyo Y., Srisantoso B., and Sumaryanto. 2006. A New Completion Solution for Multi Layer Gas Fields: A Case History. Presented at the SPE Asia Pacific Oil & Gas Conference and Exhibition, Adelaide, Australia, 11-13 September. SPE-100991-MS. http://dx.doi.org/ 10.2118/100991-MS. Guo, Boyun., Lyons, W. C., and Ghalambor, A. 2007. Petroleum Production Engineering A Computer-Assisted Approach. Oxford, UK: Gulf Professional Publishing. Kramadibrata, A. T., Sumaryanto, and Panjaitan, P. R. 2011. Developing Oil in Monobore Well Completion Using Permanent Coil Tubing Gas Lift Application. Presented at the SPE Asia Pacific Oil and Gas Conference and Exhibition, Jakarta, Indonesia, 20-22 September. SPE-147903-MS. http://dx.doi.org/10.2118/147903-MS. Manatrakool, C., Dyer, S., and Son, N.H. 2013. Restoring Monobore Well Life with Novel Coiled Tubing Gas Lift Dip Tube in a Highly Corrosive Environment. Presented at the SPE/ICoTA Coiled Tubing & Well Intervention Conference and Exhibition, The Woodlands, Texas, USA, 26-27 March. SPE-163887-MS. http://dx.doi.org/10.2118/163887-MS. Naguib, M.A. et alet al. 2000. Guideline of Artificial Lift Selection for Mature Field. Presented at the SPE Asia Pacific Oil and Gas Conference and Exhibition, Brisbane, Australia, 16-18 October. SPE-64428-MS. http://dx.doi.org/10.2118/64428-MS. Oyewole, P.O. and Lea, J.F. 2008. Artificial Lift Selection Strategy for the Life of a Gas Well with some Liquid Production. Presented at the 2008 SPE Annual Technical Conference and Exhibition, Denver, Colorado, USA, 21-24 September. SPE-115950-MS. http://dx.doi.org/10.2118/115950MS. Wijanarko, A. et alet al. 2012. Renewal Plan: Efficient Strategy for Optimum Development in Mature Fields – A Success Story from Sanga-Sanga Assets. Presented at the SPE Asia Pacific Oil and Gas Conference and Exhibition, Perth, Australia, 22–24 October. SPE-158716-MS. http://dx.doi.org/ 10.2118/158716-MS.