SPE 100991 New Completion Solution For Multi Layer Gas Fields: A Case History [PDF]

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SPE 100991 New Completion Solution for Multi Layer Gas Fields: A Case History M.A. Arianto, SPE, Y. Susatyo, SPE, B. Srisantoso, SPE, and Sumaryanto, SPE, VICO Indonesia Copyright 2006, Society of Petroleum Engineers This paper was prepared for presentation at the 2006 SPE Asia Pacific Oil & Gas Conference and Exhibition held in Adelaide, Australia, 11–13 September 2006. 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, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes 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 where and by whom the paper was presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax 01-972-952-9435.



Abstract Recently an experimental completion, called “Dual Monobore” was implemented in VICO Indonesia. The paper will describe an implementation of this completion as a new solution adopted in VICO to optimize both gas production and reserves recovery from multi layer gas reservoirs. Using monobore completion concepts, the “Dual Monobore” completion has the flexibility to allow simultaneous but separate production from depletion drive reservoirs and water drive reservoirs. Introduction VICO Indonesia is the operator of the Sanga-Sanga PSC in East Kalimantan (Indonesia) with four major gas fields and production of about 600 MMSCFD of gas, 11,000 bcpd of associate condensate and 14,000 bopd of oil. A typical field consists of more than 500 unique reservoirs that have permeability ranging from less than 1 md to more than 1,500 md and pay zone depths ranging from 1500 ft to 13,000 ft. As a mature field, the reservoir management challenge is to optimize the completion to maximize the commercial rate and to optimize reserves recovery from even marginal reservoirs. Typically the “long life” and low rate reservoirs are deeper, and are characterized by low permeability (1 to 100 mD) and a depletion drive mechanism, while the shallower and most prolific (permeability ranging between 100 to 1000 mD) reservoirs are characterized by a strong water drive mechanism. Starting the completion from the deeper section will give only a low gas rate which is less attractive for new well performance. This needs to be commingled with several additional zones to increase the rate to avoid liquid loading problems. Alternatively, starting the completion from the shallower section provides higher gas rate but can result in severe difficulties when isolating watered out perforations and additional difficulties when accessing the deeper reservoirs



because of mechanical restrictions (in front of the isolated perforations) and because of sand or debris accumulation. A new completion solution was needed to address this issue in an economic way. This paper presents a case history describing an implementation of an experimental completion called “Dual Monobore”. It will discuss completion operations, well head, cement bond log result and perforating gun orientation. Completion History The completion philosophy within VICO has changed considerably over the years. Currently (as of December 2005) more than 600 wells have been drilled. In the early field developments between 1970 and 1994, the philosophy was to use conventional completions with one or two production strings as dual/single selective completions (FIG.2). The tubing strings were either 3-1/2” or 2-3/8” and the production casing was either 9-5/8” or 7”. There was usually a long string completion on the very bottom of the well, one or more selective completions produced behind sliding sleeves and a short string completion on the top. Typically a completion required numbers of single packers and a dual packer, several sliding sleeves and an on-off connector, which resulted in a lot of sealing mechanism areas, which could be subject to leaks and communication. Many difficulties were encountered during the installations of such completions, resulting in crooked tubing because of excessive setting weights, packer failures, TCP guns not fired, sliding sleeves not moving, wireline plug problems due to junk and communication due to erosion and corrosion in the tubing strings. In some cases, the completions had to be pulled before production had even begun. The preferred perforating method was to utilize TCP to achieve deep penetration with underbalanced perforation. These guns were hung off both the long and short strings, which prevented production logging tools to be run across perforated zones for reservoir evaluation purposes. Regarding reservoir management issues, several problems have been identified. The commingled zones on selective completions could reduce the reserves recovery of the overall commingled zones since the performance of each zone was different (due to depleted BHP or water-out problems). It was difficult to have individual data acquisition in commingled zones produced behind an SSD. This led to the necessity of developing a new completion type. In 1997, a team was formed to review and evaluate the drilling and completion philosophy and a simple monobore completion program with a 4-1/2” pipe cemented from TD to



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the surface was recommended. This type of completion resulted in drilling and completion cost savings of around $200,000 per well down to the deepest zone at 14,000 ft. It was mechanically simpler because there was no completion jewellery required. Perforation could be done without requiring a rig and it was quicker to add and isolate zones. If additional deliverability was required, more zones could be perforated to provide extra gas rate. Initially for deeper low permeability sands VICO adopted a modular gun system for safe underbalanced perforation. Subsequent zones would be perforated using e-line with limited underbalance. The 4-1/2” monobore delivered a similar rate to that of two strings of 3-1/2” tubing. However in the lower permeability and/or depleted reservoirs, this 4-1/2” monobore was susceptible to liquid loading problems thus reducing reserves recovery. Adding new perforation zones helped to solve this loading problem but later on some wells were shown to suffer from cross flow. The problem became more complicated if one of the commingled zones produced water early and killed the other open zones. In 2003, a combination of monobore on the bottom and packer type completion on top was introduced, called ‘monobore hybrid completion’. Even though this completion helped in optimizing reserves recovery from the marginal zones at the bottom of the well and reduced the cost compared to conventional completions, the risk of leaks and communication due to the sealing mechanism still remained. Proposed Completion A new completion type was required that met the following requirements: it should be packerless to reduce the cost and complexity of rig operation; it should allow flexibility on production strategy within a multilayer gas reservoir; it should allow individual zones to be added or isolated; and it should be of a smaller tubing size to avoid liquid load-up problems. The solution that was developed is referred to as a “Dual Monobore” completion. This followed the monobore concept but used dual 3-1/2” tubing cemented from TD to surface. Some risks in implementing this experimental completion were: - it had never been applied in VICO Indonesia - a stand-off mechanism between two strings to overcome the cement isolation issue was required. - running dual strings simultaneously and dual string cementing practices were seen as challenging - gun orientation could be an issue Application In 2005 VICO drilled three Dual Monobore wells which delivered proven additional value to the business. Several variations on the theme were applied, such as open hole and casing cemented, shallow and deep well, high and low permeability reservoir. Field characteristic Two of these wells were drilled on the crest of the Badak Anticline and one was drilled on the crest of the Nilam field. Both of the Badak wells were drilled vertically to the main



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reservoir target with the first well (well X) reaching total depth (TD) at 10,571’ TVD (targeted on the deep reservoir) and the second well (well Y) at 6,311’ TVD (targeted on the shallow reservoir). The Nilam well (well Z) was drilled slightly directionally, with the kick off point at 8,500 ft and maximum angle 15.63 degrees. The well was drilled to TD at 13,668 ft Well Drilling & Completion The wells were drilled early in 2005, and electrical logging and sampling was performed for well evaluation. Well X (FIG.3) experienced wellbore stability problems which resulted in a drill string being left in the hole and an abandoned lower section. The well was completed as a dual 31/2” monobore cemented inside 9-5/8” casing. Well Y (FIG.4) and well Z were completed as a dual 31/2” monobores cemented in open hole. In all cases dual pipe - surface handling equipment was required to allow pipe reciprocation during the cementing job. Centralizer & Cement Bond A Dual string centralizer was installed in both open hole and cased hole applications as a stand-off mechanism between the two strings (FIG.5). This was required to enable both strings to be run into the hole simultaneously instead of individually as was the previous VICO practice. Additional surface equipment on the rig, such as dual ram BOP, dual pipe handling tools was also required. The cementing process was carried out by pumping cement thru the Long String. A through tubing cement bond evaluation was run on the Long String for both Well Y and Z to evaluate cement bonding. In the deeper single monobore section, the log indicated excellent bonding on both tubing to cement and cement to formation with average amplitude of less than 5mV. In the dual monobore section, good bond was also recorded, despite concern about how the tool would respond in this type of completion. Wellhead This Dual Monobore completion required a different set up for the wellhead compared to previous VICO completions (FIG.6). A dual slip mechanism complete with pack-off was set in the tubing head since both strings were run simultaneously instead of the tubing hanger system that was required previously on dual conventional completions. A tree adapter was also required to accommodate the need for back pressure valves. The rating of the tree was to the same VICO standard as that in previous dual completion systems. Orienting Perforation Unlike a single monobore completion, the existence of adjacent pipe was a concern during the perforation jobs. Consequently an electric gun orientation system with magnetic flux detection called Perforation Orientating Tool (POT) was utilized. A POT surface simulation was carried out for the conditions found in Well X (dual completion inside cased hole) and in Well Y (dual completion cemented in open hole) with a set-up that modeled the downhole conditions. In the cased hole situation, the maximum magnetic flux was



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measured when the tool faced the adjacent casing (in the opposite direction to the other tubing string). This was because the casing has more steel when compared to the tubing. The perforating gun phasing was configured to shoot in the opposite direction to the magnetic sensor which aligned with the MINIMUM flux. In the open hole condition, the results were the opposite, and perforation was in the direction opposite to the MAXIMUM flux (FIG.7). Results All wells were completed as Dual 3-1/2” Monobores successfully without experiencing any operational issues. Cement bond logs were run after and confirmed good cement bond quality on both single and dual monobore sections. The POT was used to orient the guns according to the recommendations of the surface simulations, and this resulted in perforation being carried out without impacting the adjacent string. The change of completion design from either dual conventional or 4-1/2” monobore to dual 3-1/2” monobore in VICO does not impact the drilling of the well significantly since the hole size does not change. It also allows the flexibility to change the completion to a single monobore completion if required based on the electric logging evaluation results if required. The 3-1/2” completion additionally favours the current mature field conditions since critical flow rate is important to overcome the liquid loading issue. This completion design has allowed us to optimize the policy of bottoms-up perforation in both the deep tighter sands in the long string and the shallower more prolific water drive sands perforated in the short string. Cost Effective In term of drilling and completion cost, this completion is more economic compared with dual conventional packer type completions since the total rig-time is reduced by 5 to 7 days. Rig-time is similar to that of a 4-1/2” monobore completion well, but the economics are more attractive since it is possible to produce from both strings simultaneously. Conclusions 1. The 3-1/2” Dual Monobore completion has been demonstrated to be a feasible alternative for future VICO completions in multilayer reservoirs. 2. It is economically more attractive than dual conventional selective completion types and 4-1/2 monobores. 3. It allows the flexibility of producing from two different strings simultaneously, reducing any requirement to commingle production from different zones. 4. Reserves recovery is improved by allowing production to a lower critical rate when compared with 4-1/2” monobores. Acknowledgements The author would like to thank the management of VICO Indonesia and BP Migas to publish this paper. We also would like to thanks to Ronald Gunawan, Bill Turnbull, Robert Nikijuluw, Roberto De Mitri (Asset Team) and Drilling Department for support and discussion.



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Nomenclature TCP: Tubing Convey Perforation POT: Perforation Orienting Tool BOP: Blow Out Preventer mD: milli Darcy (permeability) BHP: Bottom Hole Pressure ID: Inner Diameter TD: TotalDepth TVD: True Vertical Depth



References



1. Ismanto, B., Mike Hass, John Dyer: “New Well Architecture Successfully Optimizes the development of fluvio-deltaic Multi-layered Gas Field” paper SPE 64394 2. Gunawan, R., and Dyer, G.R:”Tubing Size Optimization in Gas Depletion Drive Reservoirs”, paper SPE 37001 presented in 1996 SPE Asia Pacific Oil and Gas Conference, Adelaide, October 28-31. 3. Brown, K. E., and Lea. F.:”Nodal System Analysis of Oil and Gas Wells”, JPT (Oct.1985) 1751. 4. Ikoku, Chi U., Natural Gas Reservoir Engineering, John Willey & Sons (1984) 141.



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FIG.1. VICO Indonesia (Sanga-sanga PSC)



FIG.2. Typical Conventional Completion



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3-1/2" Tubing



3-1/2" Tubing TOC ~ 1,800' 9-5/8" 2,315'



Perf: 5,785'-5,790' (5')



Perf: 7,117'-7,122' (5')



3-1/2" to 5,898'



Perf: 7,346'-7,361' (15')



Float Collar @ 7,466' MD



SS Tbg @ 7,491'MD



LS Tbg 7,498' MD



9-5/8"EZSV @ 7,500'MD



9-5/8"@ 7,555'MD



FISH Perf: 6,115'-6,120' (5') Float Collar 6,276' TD 10,571' MD



FIG.3. Well X Diagram



3-1/2" to 6,308' TD 6,311' MD



FIG.4. Well Y Diagram



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FIG.5. Dual Centralizer



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FIG.6. Wellhead



GUN Direction



GUN Direction Min



2 x 3.5 inside 9-5/8 casing



Max



FIG.7. Gun Orienting Simulation



2 x 3.5 in the open hole