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fax 01-972-952-9435. AbstractDrilling in deep water environments, such as the Gulf of Mexico (GoM), presents the potential for a variety of wellbore and operational problems.Wellbore stability, rates-ofpenetration (ROP), hole cleaning, and pressure management are but a few of the key operational parameters affected by the choice of drilling fluid for a given well. Synthetic-base muds (SBM) provide excellent wellbore stability and maximum ROP, particularly in combination with PDC bits. Conversely, management of equivalent circulating density (ECD), pump initiation and surge pressures are more difficult to control with SBM due to the effects of temperature and pressure on rheological properties. The inability to effectively control these drilling parameters can result in catastrophic lost circulation events, which negatively impact operating costs arising from non-productive time (NPT), as well as the high unit cost of the SBM. This paper highlights the development and application of a new constant-rheology synthetic-based mud (CR-SBM), designed to overcome the problems associated with pressure management when using SBM in deepwater operations. Unlike conventional SBM, this new fluid exhibits a "constant rheology" profile under the conditions encountered in deepwater operations. With the fluid's constant rheology profile, downhole surge pressures and ECD are minimized, thus reducing the frequency and severity of lost circulation events. In addition, the CR-SBM has consistently facilitated delivery of hole cleaning and barite suspension objectives in directional wells.The CR-SBM presented in this paper is unique in the sense that the near constant profile of key rheological properties was achieved using organophilic clay and without the use of special emulsifiers. In general, the components of the CR-SBM are the same as conventional SBM. Case histories are presented that demonstrate the degree to which the new CR-SBM increases deepwater operational efficiency by reducing downhole mud losses and non-productive time.

A 1999 SPE/IADC paper (52782) identified and documented solutions to a number of drilling problems encountered in Ultra-deepwater drilling. Since that time the industry has pushed the water depth record beyond 10,000' of water and drilling depths below 32,000'. A number of new problems have occurred in the last 8 years that have been caused by mechanical failures (equipment stressed to its limits) or human error. In the Gulf of Mexico recent drilling has encountered problems drilling salt and tar that the industry had not previously experienced. Three operators active in deepwater GOM have collaborated on this paper to document problems under the assumption that understanding what can go wrong is the best way to avoid problems. Introduction In 1999 the water depth drilling record was 7,520'. There were 56 rigs advertised as being capable of drilling in greater than 5,000' of water1. The water depth record is now 10,011' 2 and there are 74 rigs capable of drilling in greater than 5,000' of water3. In the 1990s there were 148 wells drilled in the Gulf of Mexico in greater than 4,000' of water. By the 2000s (mid 2006) there have been 524 wells drilled in greater than 4,000' of water. The authors' companies have drilled 291 of these wells in the Gulf of Mexico since 2000. The number of wells being drilled in deepwater has increased. The water depth, total depth and complexity of those wells drilled in deepwater GOM has also increased. The depth record is now 34,189' MD4.

TX 75083-3836 U.S.A., fax 1.972.952.9435. AbstractA 1999 SPE/IADC paper (52782) identified and documented solutions to a number of drilling problems encountered in Ultra-deepwater drilling. Since that time the industry has pushed the water depth record beyond 10,000' of water and drilling depths below 32,000'. A number of new problems have occurred in the last 8 years that have been caused by mechanical failures (equipment stressed to its limits) or human error. In the Gulf of Mexico recent drilling has encountered problems drilling salt and tar that the industry had not previously experienced. Three operators active in deepwater GOM have collaborated on this paper to document problems under the assumption that understanding what can go wrong is the best way to avoid problems.

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This paper describes the methods and technologies employed during the drilling of the Jolliet Development wells. The Jolliet development wells were drilled from a subsea drilling template in water depth of 1760 feet. INTRODUCTION The field is currently producing from the first Tension Leg Well Platform (TLWP) in the Gulf of Mexico which was installed after completion of the drilling phase. Jolliet development drilling operations were conducted between July 1987 and May 1989 after installation of the drilling template. The drilling performance attained on this project was outstanding when compared with other wells drilled in this type of frontier environment. This paper presents an overview of the methods and equipment used to optimize deepwater drilling from a template and therefore ultimately realize substantial savings. Key elements of the successful Jolliet drilling program were a result of THOROUGH PRE-PLANNING through superior teamwork between operations and engineering personnel and the inclusion of state of the art. The detailed drilling rig specification, steerabledirectional drilling motors, MWD tools with downhole torque and bit weight capabilities, development of an All oil Mud System utilizing LVT base oil, implementation ofimproved hole cleaning techniques areindicative of the detailed approach taken throughout the drilling program. Personal computing capabilities played a major part in the ability to thoroughly analyze and optimize drilling. Each of these elements were continually fine tuned and adjusted through a detailed system of concurrent critique. TEAM ORGANIZATION The Jolliet drilling team was formed well in advance of drilling template installation. Personnel from many different departments within the company were pulled together to form the team. Company management made a committment to ensure that the expertise ofindividuals within the company was utilized to the fullest. The team was organized with a central point of focus around the DrillingSupervisor. All planning and optimization was funnelled to and from the DrillingSupervisor for implementation as illustrated in Figure 1. PROJECT OBJECTIVES The first step in assurance of a successful drilling program was to clearly define the MISSION of the drilling team and the program. Clear and concise objectives were defined. Safety From the outset safety was identified ag the team's most important priority. The safety of the drilling operation and all team members was considered first when planning and executing all operations. Protection of the environment and compliance with governmental regulations were addressed and included within the umbrella of the "Safety Objective". Well Productivity Maximum well productivity, as a result of minimum exposure to formation damage during drilling operations, was considered paramount. Drilling practices as well as the mud system and additives were closely scrutinized to ensure minimum formation damage. Primary cementation Good primary cement jobs were identified as an absolute requirement for the efficient depletion of the Jolliet reservoirs. Primary cementation techniques were fined tuned for integration with subsea wellheads. This of course resulted in a minimum requirement for remedial cement jobs both during and after drilling operations.

The combination of a newly developed extreme-tensile-strength steel wireline cable armor and polymer encapsulation technologies has recently created a second generation of low-torque, extreme-strength wireline cables. The high-pull system is complemented with high-capacity winch units for surface data acquisition, tension-relief capstans, and downhole well accessories. The resulting surface pull capacity of wireline conveyance reaches 26,000 lbf, a 25% increase over the strongest system available previously. When the 21,000-lbf system was introduced in 2010, deepwater fishing incidents dropped to less than 1% of total descents. However, with 3 days per fishing operation, associated deepwater fishing time remains high. The new high-pull system has been deployed in the Gulf of Mexico since October 2014. Pulls exceeding 21,000 lbf made it possible to prevent four instances of otherwise unavoidable fishing incidents, saving more than 12 deepwater fishing days and USD 9 million of rig time. In 2015 Gulf of Mexico fishing incidents have dropped to a record low 0.4% of total descents.