Reentry Drilling Research Articles

U-Shaped Re-Entry Drilling Revitalizes Depleted Reservoirs Offshore Congo

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 191436, “Extended-Reach U-Shaped Re-Entry Drilling in Shallow, Depleted Fractured Reservoirs in Congo’s Oldest Offshore Oil Field,” by Mike Tony Chembou, Bruno Valeri, Lois de Crevoisier, Michel Akue, and Vincent Rodet, Perenco Congo, and Gabriele Ghia, Achille Mouamba, and Ali Lazzem, Schlumberger, prepared for the 2018 SPE Annual Technical Conference and Exhibition, Dallas, 24–26 September. The paper has not been peer reviewed. Against the background of a low-oil-price environment, a redevelopment project was launched to give a second life to a shallow, depleted, mature offshore Congo oil field with viscous oil (22 °API) in a cost-effective manner. The solution selected was to drill U-shaped side tracks (inclination at total depth=115°) from the original boreholes on an existing platform at a water depth of 60 m. The objective was to create a second drainage area. The project team used innovative, low-cost techniques to overcome many challenges. Geological Context and Objectives Under 27 platforms (four to five well-heads each), an accumulation of heavy, viscous oil is trapped in three reservoir layers. The field was produced with a combination of cold mode followed by a period of hot mode from steam injection. The consequence is a depleted (0.3-sg) and highly steam-fractured reservoir where fluid loss presents one of the primary challenges for infill development. The pilot project consists of re-entering the current producers and then deepening them in a U shape to access the same shallow reservoirs more than 200 m away from the initial production leg. All reservoirs share the same water table identified below an impermeable formation underneath the target layers. To avoid water breakthrough, the trajectories were planned with up to 18°/30 m to prevent the well from entering the water-bearing layer, with minimum 30-m true vertical depth standoff from the oil/water contact. Well Design and Architecture The well architecture is selected to match the existing mother-well construction. All selected re-entry candidates are producing wells showing the following well architecture: 9 5/8-in. casing set as intermediate casing at approximately 100 m measured depth (MD) below the rotary table A mixed string composed of cemented blank 7-in. casing and uncemented 7-in. slotted liner in front of the pay zones. An external casing packer (ECP) was installed between the two strings, and a cementing job was performed above the ECP. The float shoe at the bottom, therefore, was uncemented and prone to be untorqued during re-entry The completion system consisted of progressive-cavity-pump or sucker-rod-pump strings, depending on the wells. To fulfill the geological and reservoir objectives, the wells were re-entered by drilling a 6-in. hole section from a 7-in. float shoe to the U-shaped total depth before a 4½-in. liner was run. The sand-face completion evolved slightly from the first two wells (blank perforated) to the last three wells (slotted liner).

Challenges, Lessons Learned, and Successful Implementations of Multilateral Completion Technology Offshore Abu Dhabi

Summary Zakum Development Company (ZADCO), with the support from shareholders and the cooperation of Abu Dhabi Marine Operating Company (ADMA-OPCO), successfully completed the final design of the multilateral completion (MLC) system for Reservoirs A and B through the Multilateral Tie Back System (MLTBS) project. Well T-2 in the Upper Zakum field was recompleted as dual lateral/dual producer using a re-entry drilling system (RDS) Version 2 and a dual bore deflector (DBD) oriented and set on a latch coupling in the 7-in. liner hanger assembly. According to Technology Advancement Multilateral (TAML) level specification, the final MLC is categorized as TAML Level-4 E-2-PN-D/4-TR-SEP (Level-4, existing well application, two junction, producer with natural lift, dual completion, tubing reentry, separated flow). The multilateral liner hanger (MLLH) system (i.e., accommodating a latch coupling in 7-in. liner hanger assembly to have a certain access to the upper lateral) was the first successful application of that kind in the world. The teamwork and integrated approach for the trial planning and implementation, as well as lessons learned from a predesign trial (TAML Level-4 E-2-PN-D-TR-SEP using straddle assembly) for Well T-1 completed in 2000, have led to reaching the final goal of the MLC in Well T-2, which provides ZADCO with the following reservoir benefits: -Independent coiled tubing access to the upper (Reservoir A) and lower laterals (Reservoir B) through a dual completion to perform effective stimulation and reservoir monitoring.-Full bore access to each lateral immediately after pulling out the completion, which is an additional feature to the predesign of an MLC for Well T-1.-Allow selective water shutoff to cope with water breakthrough into the upper-cased lateral.-Possibility of extending well life by drilling a secondary lateral through a window joint installed in the upper-cased lateral. Moreover, another MLC trial, installed in the quadrant multilateral well RL-2 in 2005, has been successfully implemented by using mechanically selective through tubing re-entry equipment. This success was largely because of the lessons learned from a similar MLC design implemented in well RL-1 in 2001. These successful trial implementations proved the MLC system is applicable for any new/re-entry wells in ZADCO reservoirs, which provides new methods of reservoir management, and creates new completion strategies for ZADCO field development. This paper covers the MLC strategies, lessons learned through the successes and failures and the additional challenges planned for the future of the MLTBS project.

Technology Focus: Mature Field Revitalization (January 2009)

Technology Focus Even as new discoveries are developed and produced, substantial additional reserves can be secured by enhancing recovery from mature fields. Mature fields have the potential to contribute significantly to future reserves—provided that recovery can be optimized. Usually, it is the new discoveries that capture the attention of the oil industry; however, 70% of the hydrocarbon liquids produced in the world today actually come from mature fields. With most of the world's potential oil provinces having already been explored and major new discoveries becoming increasingly rare, mature fields are destined to play an ever-more-prominent role in energy supply. It is generally accepted that 30 to 35% of the original oil in place will be recoverable by the end of the normal production period. However, advances in technology (fueled by higher oil prices) are making it feasible to access remaining reserves. Considering the substantial quantities of remaining oil at stake, boosting the recovery factor on all the world's oil fields by a mere 1% would cover 3 years of worldwide consumption. Techniques to improve the recovery factor include: secondary- and tertiary-recovery schemes, horizontal and multilateral drilling, improved perforation and stimulation methods, new completion techniques, advanced logging procedures, and optimal placement of the new wells. Mature fields, however, offer their own set of challenges. In addition to dealing with aging installations and earmarking investments to access additional reserves, all aspects must be considered carefully from a project-economics point of view. Water is another problem in reservoirs nearing the end of their production life; most oil companies produce far more water than oil, raising environmental concerns and water-handling expenses. Consequently, mature fields would require a strategy that is based on tapping bypassed oil, improving recovery from existing producing zones, cutting costs, and implementing leading-edge technologies to maximize production. Mature Field Revitalization additional reading available at the SPE eLibrary: www.spe.org SPE 113684 • "Mature-Field Rejuvenation of a Tight Gas Carbonate Utilizing Coiled-Tubing Underbalanced-Drilling Techniques" by C. Mykytiw, SPE, FX Solutions Group, et al. SPE 113271 • "Techniques in Marginal and Mature Fields in the Pannonian Basin, Hungary: Case Study" by A. Holoda, MOL, et al. SPE 112940 • "The Omar Field (NE Syria) Is Overcoming Its Mid-Life Crisis" by J. Neidhardt, Shell, et al. SPE 112586 • "Horizontal Extended-Reach Re-Entry Drilling of Sidetracks at Sakhalin Island Increases Oil Production From Mature Oil Fields" by M.L. Drnec, SPE, Schlumberger, et al.

Technology Focus: Coiled Tubing Applications (June 2008)

Technology Focus Viewed from the wide perspective of the exploration and production industry, the coiled-tubing (CT) fraternity might be regarded as a relatively small group of fringe players who plastically deform pipe for a living. However, the truth is that CT has grown into a business generating USD 3 billion in revenue and has become an indispensable tool in many operating locations. Like many emerging technologies, the first decade of CT's existence was mostly a struggle to stay alive; but having survived the challenges of the early years where pipe failure was a regular occurrence (Who doesn't remember a CT string inexplicably parting in a well and the subsequent fishing operation?), the industry changed gears and began to expand outside niche areas. In more than 3 decades of continuous development, we have seen CT materials reach an unprecedented level of manufacturing reliability such that premature pinholes have been virtually eliminated. As a result, pipe sizes have increased and strings have become longer, which in turn has propelled the technology in ever-increasing directions. Thirty years ago, a typical string weighed approximately 12,000 lbm, while today we routinely use strings weighing in excess of 60,000 lbm, with some of the larger strings tipping the scales at 120,000 lbm or more. The technology has evolved from its traditional role of gas lifting and sand cleanouts to embrace such diverse applications as re-entry directional drilling, CT fracturing, multilateral stimulation, and grass-roots drilling to name just a few. The papers selected for this feature are designed to highlight just how far the technology has come and hopefully stimulate the reader along some new avenue of investigation. Interestingly, many of the early adopters of this technology are still active in the field, having dedicated much of their working lives to both the advancement of the technology and the exploitation of such technology in new applications. I never cease to be amazed at their ingenuity, and I am confident that the next generation will continue the legacy of the pioneers. Coiled Tubing Applications additional reading available at the SPE eLibrary: www.spe.org SPE 110382 • "Case History: Application of Coiled-Tubing Tractor to Acid Stimulate Openhole Extended-Reach Power-Water-Injector Well" by Ayedh M. Al Shehri, SPE, Saudi Aramco, et al. SPE 106639 • "16Cr Coiled-Tubing Field Trial at Prudhoe Bay, Alaska" by J.Y. Julian, SPE, BP plc, et al.

Plasma Channel Miniature Hole Drilling Technology

With growing economic and environmental pressures, oil companies seek ways to increase the oil recovery from every well. Re-entry drilling of horizontal sidetracks from existing wells and multilateral drilling for new wells are techniques which help to achieve that increase. However, new approaches are needed to reduce the cost and to improve efficiency of rotary drilling methods used for these purposes. A new nonrotary plasma channel drilling (PCD) method for drilling of small diameter holes (3.5-15 cm) in oilfields for sidetrack creation and multilateral drilling is described in this paper. The method relies upon the use of the energy of impulse spark discharges which are formed inside the rock formation ahead of the drill position. Repeated formation of the plasma channel results in an effective and controlled drilling action. Plasma channel drills developed at Strathclyde University are able to cut clearly defined circular holes in medium hard sandstone with speeds of up to 16 cm/min using specific energies as low as 400 J/cm/sup 3/. Plasma channel drilling has the potential to increase the lifetime of oil wells and would significantly reduce the cost of exploration drilling and subsurface data acquisition. PCD technology can also be a cost-effective and practical solution for other applications such as mineral mining, water boring and scale removal where micro-hole drilling is essential.

Horizontal Re-entry Drilling With Coiled Tubing: A Viable Technology

Abstract Horizontal drilling technology has been the fastest growing segment of the oil and gas industry over the last few years. With the diversity of reservoirs in the Western Canadian Basin, Canada is widely recognized as a leader in this technology. Due to economic, environmental, and surface logistics concerns, reentry drilling from existing wellbores is often an extremely viable solution to horizontal development in existing reservoirs. By utilizing an existing wellbore, many of the costs can be avoided and often troublesome formations are already secured behind casing. Coiled tubing drilling is also a fast growing technology in Canada, and the obvious advantages of coiled tubing for a safe, efficient drilling operation which lends itself easily to "underbalanced" or "live well" operations have propelled it into the horizontal re-entry market. This paper examines the rationale behind the selection of coiled tubing as a viable drilling technology for horizontal reentry drilling. A summary of the field trials is also included along with a discussion on the current focus of technology development. Objectives In 1995, Morrison Petroleums initiated a program of re-entry drilling in several Mannville pools of Southern Alberta. The objectives of the program were as follows:Accelerate production of Mannville pools in Southern Alberta.Improve total recovery within economic limits.Determine most cost effective technology for reservoir management.Take advantage of royalty relief schemes available for reentries under current regulatory structure. Technology Evaluation Why Horizontal Re-entries? The primary technology options for reservoir management available were as follows: The selection of coiled tubing underbalanced drilling as a reservoir management tool to enhance economics of pool development was arrived at after consideration of the above objectives. The primary technology options available were as follows:Vertical infill drillingHorizontal new well infill drillingHorizontal re-entry drilling The above options could further be divided into overbalanced and underbalanced drilling techniques and could be conducted with conventional jointed pipe drilling technology or coiled tubing drilling technology. The overall economics of re-entering an existing well and drilling a horizontal wellbore versus drilling a new vertical or new horizontal well were projected to favour the horizontal re-entry. The elimination of requirements for lease acquisition allows for a more cost effective and timely reservoir development scheme. The royalty schedule for re-entry drilling also offered additional incentive over new drills in this area. Old marginal wells do not recover reserves in place before economic limits are reached. Horizontal drilling was expected to provide better reservoir access, improved drainage efficiency and an improved recovery factor. Three wells were selected as candidates for coiled tubing underbalanced drilling after consideration of the above objectives. Why Underbalanced Drilling? The reservoir in question consists of tight sandstone with low permeability and porosity and depleted pressure. As a result, these wellbores are difficult to clean up with post-drilling stimulations. Formation damage problems can be circumvented by maintaining underbalanced conditions while drilling.

Short-Radius Lateral Drilling System

Abstract Development of a rotary-guided short radius curve drilling tool is described. Improvements over prior tools include an anti-whirl PDC bit, a stronger and smoother flexible joint, a signalling valve to assist in tool face orientation, and a computer-aided system to monitor orientation while drilling. The tool drills a smooth radius of curvature which conforms to a simple relationship between the bit tilt angle and the distance between two points of contact with the wellbore. The authors advocate using this type of tool to economically enhance oil recovery in mature fields by laterally recompleting existing wells. Eight short radius lateral wells were drilled at 5000 ft depth in West Texas during field testing of the tool. Introduction There are numerous mature oil fields in the United States and other countries that are experiencing declining production. Unfortunately, even after the latest enhanced recovery methods are utilized, vast oil resources will be left unproduced. Lateral wellbores drilled from existing wells offer the potential to drain more oil than would be recovered otherwise. Laterals may be used to tap fresh oil by intersecting fractures, penetrating pay discontinuities, and draining up-dip traps. Lateral recompletions can correct production problems such as water coning, gas coning, and excessive water cuts from hydraulic fractures which extend below the oil-water contact. Synergistic benefits may result from coupling lateral recompletions with enhanced recovery techniques to solve conformance problems, contact unswept oil by recompleting injection wells, and to redirect sweep by converting existing well patterns into line-drive configurations. Lateral recompletions strategies can take advantage of the current production infrastructure, capital resource of existing wellbores, known resources of oil in place, and secondary and tertiary recovery technology. A major impediment to the widespread use of lateral re-entries is that drilling and completion of the laterals must be done relatively "cheaply." Workover economics in mature fields require substantial cost reductions over the methods most often used for drilling new horizontal wells. The need for a reliable reduced-cost drilling system that utilizes the equipment and cost structures of workover and repair services provided the impetus for a development and field test program in West Texas where laterals were drilled in 8 wells. This paper primarily discusses development of the curve drilling portion of the re-entry system. Even though this is a small part of the overall effort to place a re-entry lateral in a well, it is a critical and costly part. Once the curve is drilled, the lateral is rotary drilled with a somewhat more conventional stabilized bottomhole assembly and the same articulated drillstring that is used for curve drilling. Curve Drilling Tool Background For a re-entry drilling system to be technically successful it must be capable of drilling a consistent radius of curvature and drilling the curve in the desired direction. These requirements arise from the necessity to (1) position the end of the curve within a precise depth interval so the lateral can traverse the payzone as desired, (2) place the lateral in a direction dictated by well spacing, desired sweep pattern, or other geological considerations, and (3) to establish a smooth curve to facilitate drilling the lateral and completing the well. P. 693^