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Directional wells (S-shape). Over time, the seabed has been altered by the salt movement which has created numerous big faults extending up to the seabed as well as big caverns and valleys. This condition limits the ability to drill vertical wells into the reservoir. To date, RSB has successfully drilled an S-shape directional well with a 24° angle inside the salt in order to reach the reservoir. This challenging directional well required extensive planning in terms of geomechanics, salt stability, directional strategy, and tools. This was the first S-shape directional well drilled using power drive with an 18 and 1/8-in. bit and simultaneously under-reaming to 20 in.
Hard and silicified carbonates drilling. The formation is extremely hard (UCS-30-35K) and abrasive due to the silicified nature. This slow drilling challenge requires the application of the latest bit and turbine technology. New bit and downhole tool technology is still under study and field trial.
Well testing. There are several challenges for well testing in ultra-deepwater environments such as deep presalt wells, formation damage, and flow assurance (hydrates). To mitigate these risks, RSB is using the latest technology such as a special subsea test tree system with the ability to cut coil tubing of up to 1.75-in. outside diameter with a disconnection time of 20 seconds; a wireless annular pressure buildup monitoring system for casing annulus; real-time downhole data acquisition system during the entire drillstem test to guide drilling decisions; a high flowrate (10 gpm) subsea monoethylene glycol injection system and lower completions with formation isolation valves.
Setting the building blocks
Brazilian presalt discoveries are not only surrounded by a salt layer which is difficult to see and drill through, but they are also located in ultra-deepwater; a challenging environment for facility development.
To deliver successful projects in such a difficult environment, it is crucial to identify what can be built in order to best satisfy all project requirements. RSB is using the "building blocks approach" for its facilities visualization phase in order to define a broad and clear range of feasible development architectures from which, later on, the best will be selected.
The building blocks approach is a well-known technique for complex problem solving, which consists of finding alternative solutions to subsets of the overall problem, thus narrowing down the potential range of solutions. RSB has adapted this approach by following these processes, grouped into two stages -- qualitative and semi-quantitative.
During the qualitative stage, a range of possible solutions is defined to its broadest extent and then narrowed down. Through a number of brainstorming exercises, the requirements and scope are studied and a list of "building blocks" for the field development is generated. Potential concepts for each of these items are identified and assessed. Once each building block has a set of possible solutions, a portfolio of potential development architectures is defined and ranked by feasibility, commercial, and technical success factors.
At the second stage, with a reduced but considerable number of potential development facilities architectures, capex estimates are generated at class five accuracy, and risks and opportunities are identified for each alternative architecture, providing risk-inclusive estimates which are used to rank the different architectures.
The final semi-quantitative stage combines rankings from the previous steps: expected capex efficiency ratio, and technical and commercial soundness, which produces a unified ranking that is used for selecting the most preferable architectures. This is then passed to concept selection and conceptualization studies.
It is important to note that the aim of this screening methodology is not only to select the highest scoring cases for further progression, but also to develop knowledge of the facts and concepts that drive the accuracy of each alternative.
The authors
Jose Luis Algibez is Exploration Manager, Block BM-C-33, Brazil, for Repsol Sinopec. Algibez joined Repsol in 1995 and has been involved in the company's oil and gas exploration and development business from field geology to wildcat drilling, including oil field development. Jose has lived and worked in Algeria, Bolivia, Libya, the USA, Venezuela, and Brazil where he has managed newly discovered oil fields and assessed them for further development.
Luis Batalla is Facilities Engineering Manager of BM-C-33, Brazil, for Repsol Sinopec. Batalla joined Repsol in 2005 and has been the Facilities Engineering Manager of the BM-C-33 development since 2012. He has over 16 years of experience in oil and gas projects. In addition, Batalla is experienced in all aspects of offshore and onshore surface facilities developments, as well as in refining and petrochemical projects.
Bipinchandra Dugam is an Engineering Manager for Repsol Sinopec in Brazil. He joined Repsol in 2007 and has worked as an Engineering Manager (Drilling & Completions) in Brazil since August 2012. Bipinchandra has over 10 years' experience in drilling engineering, well planning, and testing and directional drilling.
