The Challenges of Developing a Deep Offshore Heavy-Oil Field in Campos Basin
- Fernando Pacifico Figueiredo (Petrobras) | Celso Cesar M. Branco (Petrobras S.A.) | Fabio Prais (Petrobras Intl.) | Marcelo Curzio Salomao (Petrobras S.A.) | Cristina Cledia Mezzomo (Petrobras)
- Document ID
- Society of Petroleum Engineers
- Latin American & Caribbean Petroleum Engineering Conference, 15-18 April, Buenos Aires, Argentina
- Publication Date
- Document Type
- Conference Paper
- 2007. Society of Petroleum Engineers
- 5.6.4 Drillstem/Well Testing, 2.4.5 Gravel pack design & evaluation, 2.4.3 Sand/Solids Control, 1.2.2 Geomechanics, 3.1.2 Electric Submersible Pumps, 6.5.2 Water use, produced water discharge and disposal, 5.6.9 Production Forecasting, 1.6 Drilling Operations, 5.2.1 Phase Behavior and PVT Measurements, 5.5.11 Formation Testing (e.g., Wireline, LWD), 3.1.6 Gas Lift, 5.1.7 Seismic Processing and Interpretation, 5.5.8 History Matching, 5.4.1 Waterflooding, 5.1.2 Faults and Fracture Characterisation, 3.1 Artificial Lift Systems, 4.5 Offshore Facilities and Subsea Systems, 4.1.2 Separation and Treating, 4.1.5 Processing Equipment
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Deep offshore oil production demands very high investments (CAPEX) so its development must rely on a careful planning. This frequently takes place in a setting with very limited amount of information due to high costs of appraisal operations. The figure becomes even more complicated when heavy oils are the target: low energy reservoirs require water flooding which, in turn, reflects in low recoveries and excessive water handling, not to mention other production problems.
This paper highlights different simulation studies that have been performed in order to set up an economical development plan for a 16 API 1700m water depth oil reservoir offshore Campos Basin. The main reservoir consists of a high thickness turbidite channel crossed by a N-S fault whose hydraulic conductivity is the main uncertainty. Vertically the reservoir is composed of three zones, where the upper one has a gas cap partially in contact with the two bottom ones. These structural complexities required a detailed study for positioning injectors and horizontal producers based on a decision tree analysis. The impact of other uncertainty variables was also identified and studied: horizontal permeability, vertical to horizontal permeability ratio, water-oil relative permeability and productivity index. Particular attention was given to the injectivity decline due to the planned produced water re-injection. Vertical and horizontal injection wells performances were compared in a scenario under strict geomechanical restrictions. The simulation model was also used to evaluate the possibility of developing marginal areas close to the main reservoir body.
The study leaded to a robust strategy for the water injection scheme. Risk and marginal reservoir analysis helped the decision of the features of the future production system in terms of oil and liquid processing capacity and adoption of some flexibility to make feasible the future development of marginal areas.
Exploration efforts offshore Brazil have been indicating important heavy-oil discoveries in deepwater reservoirs. The economic exploitation of these reservoirs presents technological and economic challenges that must be addressed. Therefore, the initial development plan must be defined through a detailed optimization study, considering economic indicators, oil recovery and risks 1, 2.
The development of Marlim Sul Field was planned in four modules: module 1 started in 2001 and has two production units producing 200,000 bopd. Module 2 will start the production through P-51 platform in 2008 and modules 3 and 4 are in development phase. These two last areas present special difficulties since they have oil viscosities greater than 20 cP at reservoir conditions. The introduction of new technologies could mean the solution for the feasibility of these projects.
Thus a research project was developed in the scope of Petrobras Offshore Heavy Oil Technological Program (PROPES) that comprised the following objectives: optimization of the drainage plan, taking into account the application of extended horizontal wells (around 800 m), evaluation of the use of high capacity plants for the processing of produced fluids and evaluation of the performance of artificial lift methods comparing the efficiency of gas lift and electrical submersible pumps. Studies related to the impact of the main N-S fault of the reservoir on the development plan, the consideration of uncertainties on rock and fluid properties and the analysis of the injectivity decline had also been performed.
This work focuses on the optimization of a development plan for Marlim Sul Field's third and fourth modules aiming at establishing a robust strategy encompassing all the geological and technological uncertainties.
Reservoir General Data
Marlim Sul Field is located in Campos Basin, distant approximately 120 km from north coast of Rio de Janeiro State, Brazil. It stands in water depths varying from 800m to 2600m in an area of 572 km2. Figure 1 depicts the field location.
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