The Marlim field was discovered in February 19859 by the exploratory 1 RJS 219 A drilled in a water depth of 850 meters. This pushed the deepwater exploratory campaign culminating in several deep and ultra-deep water discoveries in Campos Basin. The necessity to overcome the environmental conditions, associated with a giant field located in high water depth and reservoir characteristics, were the main challenges in the search for new technologies in the way to operate the field. These developments were achieved by a research program created at Petrobras R&D Center. This program counted on Petrobras expertise acquired during Campos Basin development and with traditional oilfield equipment suppliers through technological agreements that led to the first oil in March 1991. The field extension and the reservoir characteristics required a large number of subsea wells and, consequently, several production platforms, so the development plan was based on the implementation of several phases in different periods. This model, also used in several other developments in Campos Basin, allowed that the required huge investments and resources to be distributed along the field development. Moreover, it allowed innovative solutions to be proposed and introduced by new oilfield equipment suppliers along the project in order to optimize CAPEX. Marlim is a remarkable achievement to the oil industry that culminated with a peak production of 650,000 bopd in 2002. It also served as a laboratory for other deepwater developments offshore Brazil. With the field maturation new challenges are being faced in order to increase the recovery factor and to reduce the OPEX. This paper will provide an overview of Marlim Field, the main achievements and problems faced up to this moment to manage its development. Introduction The Marlim field was discovered in February 1985 by the exploratory well 1 RJS 219 A drilled in a water depth of 850 meters. This discovery pushed the deepwater exploratory campaign culminating in several deep and ultra deepwater discoveries in Campos Basin. Located in the northeastern part of Campos Basin, about 110 km offshore the state of Rio de Janeiro, the Marlim field is part of the Oligocene Carapebus formation and covers an area of approximately 130 Km2, in water depths ranging from 650 meters to 1,050 meters. From rock quality point of view Marlim field Oligocene reservoirs are excellent with average porosity around 30%. The reservoirs have low silt, clay and calcite content. The core analyses of various wells indicate mean permeability of 2000 mD, mean porosity of 30% and highly friable sandstone. Marlim's reservoir exploitation strategy relies heavily on water injection as a source of reservoir energy replenishing. The field development plan was based on various phases by means of subsea wells, subsea manifolds and floating production units whose development had been scheduled in different periods in order to make feasible the huge investments and resources required. It also improved the overall performance of the field development once each phase guided the next ones through the experience obtained during its own development. To support the field development, a research program was created in the company in 1986 - the PROCAP - focusing on all the technologies required to install the first Floating Production Unit for the Marlim field.

Drilling and completion in Campos Basin have been in constant evolution, from the first subsea wells and fixed platforms to latest horizontal wells in deepwater. This paper will first present the lessons learned with drilling and completion in shallow water to latest wells drilled and completed in Roncador in the range of 1,800 meters of water depth. Exploratory drilling will be also addressed. The main points to be presented are: well design, horizontal and multi lateral wells, well head design, well control, operations with dynamic positioning vessels, completion and sand control techniques and their evolution. Second, this paper will address some challenges presenting the problems as PETROBRAS see them, what are the solutions that we are adopting and what do we expect from the industry. The issues that will be presented are: well design for production of heavy oil, dual gradient drilling, intelligent completion systems for monitoring and controlling multiple zones, production or injection from or into a single well, isolation inside horizontal gravel-packed wells, gravel packing long horizontal sections under very low formation fracture gradient. Introduction Campos Basin exploratory activities started in 1971 first with jack ups (Penrod 89) and later with moored drillships that culminated with the discovery of Garoupa field in 1974 at 124 meters of water, soon followed by other shallow water discoveries (Namorado, Enchova, Pargo and others) that came on stream in subsequent years. Petrobras started in 1984 a deepwater exploratory campaign with successful discoveries as Albacora (1984), Marlim (1985), Albacora Leste (1986), Marlim Sul (1987) and Roncador (1996). Campos Basin developments along these 25 years of production have imposed many learnings and challenges in the drilling and completion operations. Several projects were implemented from shallow to ultra deepwater using jack ups, fixed platforms, moored floating rigs and dynamic positioning (DP) rigs in drilling, completion and workover operations. These different projects required different approaches and the key was to use the learnings of each field development in future projects. The most important evolution in drilling and completion operations was seen when we moved towards deeper water. It allowed, in conjunction with the subsea hardware evolution to put the first deepwater well on stream in September 1984 (well 3-PU-2-RJS at 307 meters of WD) and the first ultra deepwater field on stream in 1999 (Roncador). In general, the geological carachteristics in Campos Basin are: shallow reservoirs, no occurrence of shallow gas or HPHT formations. Moreover, the environmental conditions in Campos Basin are mild but with high currents. On the other hand several critical issues have to be still overcome in drilling and completion operations to cope with the challenges of producing in ultra deepwater (2,000 - 3,000 meters) as: steep slope seabed, shallow and unconsolidated reservoirs (Miocene and Oligocene) and expensive operations. Nowadays there are 650 wells drilled in WD up to 1,500 meters and 114 wells drilled in WD deeper than 1,500 meters. Ultra deepwater under going field developments will lead Petrobras domestic production to reach 1.9 million barrels of oil per day by 2005.

Dynamically Positioned (DP) rigs started out in Campos Basin with an exploratory drilling program in waters around 900 meters deep. After this, these vessels were used in shallow water workover and completion jobs, where conventionally moored rigs could not work due to the cluttered sea floor. Despite their success, DP rigs do present failures such as black-outs, drift-offs, and drive-offs. Any such failure can end up in a collision with a surface or subsea obstacles, of catastrophic implications. A mathematical method was established based on probabilistic statistical analysis of vessel characteristics, black-out elapsed times, and time between total power failures to determine the minimum distance that a DP rig can work from an obstacle. This method led to the so called restriction diagram. Safety alternatives were also pursued, in partnership with the contractors, for the cases when it is necessary to operate inside the restriction diagram, such as safety anchors and safety boats. Real scale experiments were performed to test the feasibility of safety anchors for a DP semi submersible working in a close proximity to an obstacle. Furthermore, restriction diagrams, DP vessel characteristics, and safety devices have helped to choose from the available rig fleet the best unit to perform certain tasks such as well completions in a cluttered area. As a result, restriction diagrams have grown to be powerful tools to use in deep water fields development using subsea flowlines. Introduction Petrobras started its deep water drilling program using DP rigs in 1984, when the wildcat well 1 RJS 2 19 A was drilled in Campos Basin in 840 meters of water depth. 011 discoveries in waters as deep as 900 meters pushed the geological studies to deep and ultra deep waters and more DP rigs were necessary to develop a fast growing and promising exploratory drilling program. The success of DP rigs also pushed its use to shallow water workover jobs, where conventionally moored rigs could not work due to the cluttered sea-floor. Increasingly deeper water subsea completions naturally followed the discoveries. Between 1984 and December 1992, almost 8,000 days of DP operations were logged in drilling, workover, and completions operations. Moreover, for the incoming years a greater number of DP rigs would be necessary to meet the exploratory and development programs almost entirely held in Campos Basin (Figure 1). This increasing activity of DP rigs, led Petrobras to create in 1992 the Dynamic Positioning Safety Program(1) (DPPS) which is a partnership program with the DP rigs contractors to minimize the risk of station keeping failure to avoid its catastrophic consequences. Among the initial DPPS projects, there was one entitled "Risk Equivalence" that aimed to answer questions like: how safe is a DP rig when working in close proximity to another DP rig, a moored rig, or production unit? Which is the most adequate DP rig to perform certain tasks? What minimal distance a DP unit should maintain from surrounding obstacles to avoid collisions? These questions came from the the initial DP experience in Campos Basin, where 53 emergency disconnections were observed from 1984 to 1992.

The first question that arises when deep water completion (DWC) is discussed is the definition of deep water. This concept varies from company to company but Petrobras is considering deep water from 600m to 1200m water depth. From that depth until 3.000 m is ultradeep waters. DWC comprises many special equipment, mostly hydraulic operated. Most of the equipment under consideration in this paper may be similar to shallow water completion with Wet Christmas Tree (WCT) already installed but expertise, field experience and wide vision is crucial because the problems are fully different. This technical paper deals exactly with this subject. It intends to show few of the failures that Petrobras had in the last years with deep completion using wet christmas tree system. But more important than showing the failures or problems, the point is to analyze the solution that was given to all the problems. Knowledge, creativity, teamwork and patient were the basis for deriving this technology leader in the world. Introduction Deep offshore completion is still a rather new technology in our petroleum engineering world and many critical points still are under research(1). We could say that only in the last 3 years the 1.000m water depth was overcome mainly in countries as Brazil and the USA. In Brazil, the discovery of Marlim, Albacora, Bijupira, Salema, Caratinga and recently Roncador fields in Campos Basin made possible for the Brazilian government petroleum company Petrobras to invest in deep water production technology(2). This paper will discuss only part of the production technology which is the completion engineering related solely to wellhead equipment. Wellhead equipment we mean all production equipment that are installed from the wellhead connector to the well christmas tree. This includes multifarious equipments as (1) Housing for the permanent drilling base; (2) Production Adapter Base and running tool; (3) Production Tubing Hanger and running tool; (4) Wet Christmas Tree; (5) WCT Tree Cap and running tool; (6) accessories as Completion Riser, Terminal Head and Corrosion Cap (Fig. 1). In deep water drilling and completion, most of the incidents which resulted in rig loss time in the last 7 years were collected in a special report called ROA or Report for Abnormal Operations. More than a 1.000 ROAs form a special database which comprises field experience of Petrobras in treating different problems in drilling and completion in deep water and, more important, the analysis, solution and recommendation for each case. In this technical paper few cases where selected for presentation trying to cover most of the equipment /technique already cited. Main Production Wellhead Equipments In this paragraph the main production wellhead equipment and components will be briefly described. The objective is to indicate how the equipments look like, how they work, common sizes and main parts (3). Drilling Housing. The drilling housing is part of the permanent drilling guide base and is connected to the top of the 20 in. casing (Fig. 2). In deep waters, the standard nominal external diameter is 16 3/4 in. After cementing the 20 in. casing, the housing stays about 2 m above the mudline and has the following purpose:to hold up the 20 in. casing;to be a seat for the next casing hangers;to provide connection and support for the Blow Out Preventer (BOP). This housing has a H-4 profile which will allow the BOP H-4 connector to hold and resist hydraulic pressure, weight and mechanical stresses (Fig. 3). Drilling Housing. The drilling housing is part of the permanent drilling guide base and is connected to the top of the 20 in. casing (Fig. 2). In deep waters, the standard nominal external diameter is 16 3/4 in. After cementing the 20 in. casing, the housing stays about 2 m above the mudline and has the following purpose:to hold up the 20 in. casing;to be a seat for the next casing hangers;to provide connection and support for the Blow Out Preventer (BOP). This housing has a H-4 profile which will allow the BOP H-4 connector to hold and resist hydraulic pressure, weight and mechanical stresses (Fig. 3).

As the development of Marlim field was planned back in the mid 80's the challenge was to develop subsea hardware and techniques that would allow completion of 148 wells in water depths ranging from 600 to 1100 meters. As the first Guidelineless Subsea Trees were designed and manufactured the key to success was, indisputably, the flowline connection method. Starting with the Lay Away method, a natural extension of the guideline concept, Petrobras is now purchasing subsea trees with a 4th generation flowline connection method. Subsea Trees interfaces were standardized among different manufacturers and a simplified Water Injection Tree was introduced in order to improve the economics of the project. Pigging capacity and ethanol injection (for hydrates prevention) became required features for all Subsea Trees. A total of six Subsea Diverless Guidelineless Manifolds are planned for Marlim field, two of which are already installed. These Manifolds were designed based on the experience from early ones that are now in operation in Albacora field. Marlim field has been a laboratory for the development of production techniques and hardware for ultra deep water. In keeping to its role, the Multiphase Pumping System, a boosting technology with far reaching application is scheduled for installation in Marlim field in 1999. Now, with the Marlim Project halfway to completion, the evolution of hardware and techniques will be presented, along with a discussion on the issues that drove this evolution and the resulting benefits. INTRODUCTION During the 80's the number of subsea completions increased worldwide due to several reasons. In Brazil this increase was due to Petrobras option to develop Campos Basin by way of subsea completions tied up to Floating Production Units. Early oil production, reduced financial commitment and flexibility for changes as more information about the field is gathered were the main advantages. Since the first subsea tree was installed at 189 m waterdepth in April 1979, the exploratory activity has been successfully moving to ever deeper waters. In 1984 it was installed a subsea tree at 307 m water depth, the first worldwide beyond diving limit, using a horizontal remote flowline connection system. In spite of being a great achievement, the remote flowline connection system showed to be troublesome, with leaks resulting from misalignment of connecting flowlines and requiring the use of complex pull-in tools. Shortly after, as more experience was acquired, the use of this system was discontinued and diver assisted flowline connection was made a standard for shallow water up to 300 m water depth. In 1984, Petrobras decided to use Dynamic Positioning(DP) Rigs on an exploratory drilling program in the 900 m water depth range which culminated with the discovery of the giant fields Albacora (250 to 950 m water depth) and soon after Marlim (600 to 1100 m water depth). The development of a new diverless flowline connection system was required. That is when the Lay Away Connection System appeared (1987), being first used with Guideline Subsea Tree in a conventionally moored rig, in water depth of 411 m in Marimba Field. In the Lay Away Connection Method the flowline bundle is run with the subsea Tree, thus eliminating many of the existing problems of subsea flowline connections.