In Shell Exploration & Production, swelling elastomers have been deployed in a variety of applications: as a means to establish zonal isolation in liner completions, as a production separation packer, and as an integral part of an expandable open hole clad. In these applications, the elastomers have been run in various open hole, casing, and tubing sizes. A total of around 60 deployments in Shell have been recorded, all of which were technically successful. Case examples of each of the three mentioned applications will be presented from Shell operations in the North Sea, the Middle East, and the Far East. Introduction In most areas where Shell operates, especially in the more mature oil field environments, there is a high focus on well cost reduction. Various technology applications have been identified to meet this business need and allow the operator to drill wells cheaper and smarter, making the most of existing infrastructure. One technology that is experiencing a rapid uptake is the application of swelling elastomer packers. These packers, which swell naturally when exposed to the appropriate swelling agent, have successfully been used as a replacement for traditional mechanical packers and cement. The business case for using swelling elastomer packers is different per application and can include time savings as well as direct tool cost savings. Shell implemented swelling elastomers in combination with the deployment of a Solid Expandable Tubular (SET) system called Open Hole Clad (OHC) in July 2002. First application of swelling packers for zonal isolation was in the South Furious field in Malaysia in June 2003. Since then, over 60 deployments have taken place in operations in Malaysia, Brunei, Nigeria, Gabon, Oman and the UK. Theory and Definitions A swelling elastomer packer, or swelling packer, is a rubber element vulcanised onto pipe. The main property of the rubber is that it swells significantly when exposed to either aromatic hydrocarbons or saline water through a process of absorption. An oil swellable packer is a swelling elastomer packer, which swells primarily through the absorption of hydrocarbons. This is a diffusion process. Typical operating temperatures for oil swellables are 80–130°C. A water swellable packer is a swelling elastomer packer, which swells through the absorption of (saline) water. This is an osmosis process. Typical operating temperatures for water swellables are 50–90°C. The three main design parameters of swelling packers are life-span, pressure rating, and swelling time. Because of the relatively recent development of swelling packers, our understanding of these parameters is still growing and a full theoretical treatment of the subject is beyond the scope of this paper. The main factors to consider in determining the three design parameters are temperature and the geometry of the pipe, packer and borehole. Pressure ratings have been tested up to 3500 psi, although higher ratings have been recorded in the industry. Swelling times in our operations range widely from 5 to 50 days. The case examples provided in this paper show three distinctly different uses of the swelling elastomer packer: the liner completion, the production isolation packer, and the expandable open hole clad. A liner completion is defined as a liner system with slots or perforations to allow access to the producing formation. The swelling packers are used in combination with blank liner joints to isolate oil bearing zones from water zones, where conventionally a cement column would be used. The production isolation packer is defined as a seal between a production tubing and a production liner in order to isolate the various perforated sections. Swelling packers are used to replace conventional hydraulically or mechanically set packers. An expandable open hole clad is defined as an expandable tubular used to seal off water bearing formations or water producing fractures in a barefoot well section. Swelling elastomers are used to provide the seal between formation and tubular.
No one wants or expects to have to drill a relief well; however, it is a fact that a number of relief wells are required each year. Recent events have drawn attention to the need for, and the benefit of, comprehensive contingency relief well planning. On a deepwater Gulf of Mexico (GOM) well, it was noted that "Active Electro Magnetic Ranging" technology would not work at the planned intercept depth due to the presence of a large salt body. Furthermore, the planned survey program would result in a relatively large Ellipse of Uncertainty (EOU) at the desired intercept depth, which would make a relief well intercept on a first pass unlikely to succeed. A combination of "Passive Magnetic Ranging" and a modified survey program was identified as the solution to demonstrate the ability to intercept the target well on the first attempt. Due to the inherent problems associated with "active" ranging technologies in salts (De Lange, J.I., Darling, Toby J., 1990), "passive" MWD Ranging was identified as the likely ranging technique due to the fact that it is not impacted by formation type (salt). Based upon the modified survey program, it was determined that a reliable range of detection of eighty feet (80’) would be required to qualify passive magnetic MWD Ranging technology as the primary ranging technique should a relief well be required. This detection range would allow a "no flyby" intercept (also referred to as a direct intercept) by the theoretical relief well. To confirm this capability, a qualifying demonstration protocol was established and executed using casing joints that would ultimately be run into the well. The proving tests were conducted first with only remnant magnetization of the casing joints and then again after the casing joints had been magnetized with a coil.
Development of subsalt pay zones in deepwater GoM typically includes drilling long intervals of halite formation. Despite the relatively low UCS, salt drilling presents a unique challenge due to its plastic nature and tendency to creep. These factors coupled with complex deepwater casing programs necessitate the use of hole enlargement while drilling techniques. The difficulties of HEWD in salt is further magnified in deviated wellbores where maintaining the directional wellplan becomes a key performance objective.Using a 4D modeling program has resulted in improved HEWD ROP and directional control in salt on several deepwater GoM projects. The software allows engineers to model various RSS BHAs, optimize the bit/reamer cutting structure and prepare operating parameter recommendations tailored for the directional plan.Well A A Mississippi Canyon j-shaped well called for maintaining tangent at 44degrees through a 100% salt 14.5 x16.5 interval. Using a new reamer cutting structure design with a selected PDC allowed the operator to drill 7852ft at an ROP of 54.7ft/hr. The directional objective in the 12.25x14.75 interval of the same MC well was to hold tangent at 44 degrees before dropping to 15degrees. A new cutting structure design with a selected PDC was employed on the RSS/BHA. The 6022ft interval was drilled in one-run with an average ROP of 80ft/hr. Well BMaximum ROP was the primary objective in an 8877ft, 14.75x16.5 section of a s-shaped well which included building and holding at 35 degrees before dropping back to vertical in 100% salt. Bit and reamer recommendations and drilling parameter recommendations to maximize ROP were developed by calibrating the data from the offset well, Well A. The new cutting structure and pre-job planning resulted in a total run ROP of 97.5 ft/hr with an average on-bottom ROP of 129.1 ft/hr, an 80% improvement compared to offset.
Operations were being conducted with a drill ship in deepwater, harsh environment conditions offshore Nova Scotia. After securing the well, the rig disconnected the Lower Marine Riser Package (LMRP) from the lower Blow Out Preventer (BOP). After disconnecting, dynamic loads caused an uplift of the marine riser, ultimately resulting in a failure of the tensioner ring support and loss of the riser/LMRP to the seabed. No personnel were injured in this incident and no spilling of synthetic base mud to the environment occurred. This paper provides a summary of the root causes and contributing factors for the incident. The Tripod beta method was used to conduct the review of the incident. The scope of the review included the following: Measured data (rig heave, tensioner stroke, tensioner pressures)Moonpool video camera recording of riser and tensioners during and after disconnectAnalytical models for vessel & marine riser dynamics, including the riser tensioner anti-recoil systemRig/moonpool geometry, riser tensioner ring design, and space-outWeather forecastingOperating procedures Based on initial findings, further studies and analyses were conducted to better understand the dynamic behavior during the transition phase from initial disconnect to the hang-off position. Forecasted Metocean conditions from a late winter storm indicated the potential to exceed the threshold for rig heave, with the marine riser connected to the well. In preparation for disconnecting the LMRP, the well was secured with two barriers, a storm packer and closed blind shear rams. Once the rig heave limit was reached, the LMRP was disconnected from the lower BOP stack. Seven minutes after unlatching the LMRP, the riser tensioner profile on the slip joint outer barrel lifted off the riser tensioner ring and landed back onto the tensioner ring off-center. This uneven loading caused the tensioner ring halves to separate, dropping the LMRP and riser to the sea floor. Analysis showed that one of the most critical phases of disconnecting the LMRP from the BOP occurs immediately after disconnecting and prior to moving the rig a safe distance from well center. The investigation indicated that the root causes of the event included human factors, such as adding additional air to tensioner system and re-setting of the Riser Anti Recoil System (RARS) prior to final hang-off condition. Contributing factors included the dynamic behavior of the riser and a lack of specific procedures for addressing the dynamic system conditions during the critical transition phase. The paper provides additional information for riser/tensioner configuration and riser dynamics analyses during harsh environment conditions. In particular, additional analyses are presented for the transition phase from disconnect to hang-off position. Initial data is provided for further development of a smart disconnect algorithm, based on machine learning techniques of hind cast data.
Water production management starts to play a more important role as reservoirs mature. Production logging is required to identify watered out intervals in producers and thief zones in injectors. The interpretation of logs acquired in horizontal, barefoot wells in highly fractured, heterogeneous, carbonate reservoirs is challenging at least. Yet this technique has been successfully applied in Petroleum Development Oman (PDO) in the Yibal and Al Huwaisah fields (Fig. 1) and has lead to significant production improvements after the subsequent water shut off. Expandable Open Hole Clad (OHC) systems, with external seals, have been deployed to shut off water in both horizontal producers and injectors. The seal between the expanded pipe and the formation is further enhanced by elastomers with the ability to swell upon contact with formation fluids. Case histories are presented to demonstrate the viability of this new technology. Introduction As oil fields mature, production wells experience co-production of oil and water because of aquifer encroachment and/or water injection. Controlling the water production is one of the major challenges in reservoir management. Diagnosis of the zone of water influx in horizontal well bores, however, is not always straightforward and must certainly preceed any remedial water shut off treatments. This paper starts with a discussion on the water shut off technique using expandable tubulars, followed by two case histories in which more details are provided concerning production logging, expandable clad installation and production results. Technology Overview Previously published papers have discussed the concepts of Solid Expandable Tubular (SET) technology1 and the effect of the expansion process on the system's tubulars2,3 and connectors4. The specific system used in PDO, with the required adaptations, will be reviewed in this paper. The basic principle is the down hole enlargement (expansion) of a solid pipe. Expansion is achieved with a cone that can either be pushed (typically by hydraulic force) or pulled through the pipe. SET can be applied for both well construction and remediation5. Four general types of SET products can be identified:The Expandable Cased Hole Liner (CHL) is set in a cased hole environment and is typically used to isolate perforations or damaged or corroded casing.The Expandable Open Hole Liner (OHL) is used in the well bore construction process to provide an additional liner whilst minimizing Internal Diameter (ID) loss. This provides more options in the well design process to reach the required Total Depth (TD) without compromising hole size.
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