The Boscán field is a giant heavy oil reservoir (10° API) located in western Venezuela. The field is operated by the Empresa Mixta PetroBoscán. OOIP is estimated as high as 35 billion barrels. For over 60 years of production history, only ~5% of the OOIP has been recovered thereby considerable development opportunities remain at Boscán to increase recovery. Drilling highly deviated completions has proven to be a successful strategy to maximize oil recovery and mitigate ever increasing water production. The southern part of the reservoir is in contact with an active aquifer where a high contrast in fluid viscosity is present between formation water and heavy oil (0.7 vs. 350 cP) generating large differences in the mobility ratio. This causes premature water breakthrough and sharp increases in water cuts over short periods of time. Water production during the last 10 years has exceeded the handling, separation and injection capabilities at Boscán leading to a significant number of wells being prematurely shut-in. In the past, in order to control water production, shorter vertical wells were drilled and bottom water shut-off jobs were performed. However, these strategies have proven unattractive since overall net pay was reduced and coning tendencies were high. A new strategy was introduced of drilling highly deviated wells to maximize the reservoir exposed and mitigate water production by reducing pressure drawdown in the near wellbore region. Recently, a ~5.5 million upscaled grid-block reservoir simulation model was developed and is being utilized to understand the aquifer impact and for optimal field development. Initial simulation results confirmed that highly deviated wells perform better and delay water conning. This paper focuses on a deviated well strategy to increase recovery per well from a heavy oil reservoir with a strong aquifer influx. It shows how multi-disciplinary teamwork is being utilized to develop and execute the strategy and how Boscán may be used as an analogy for other fields having similar reservoir conditions.
A 12-million cell (150m ϫ 150m ϫ 1m), 3D geocellular model covering the Boscán field has been constructed. This presentation describes the results of this full-field reservoir model construction that has integrated core, well, seismic, pressure, and performance data.In 2007, new 3D seismic was acquired over the south area of the field. The seismic was reprocessed with pre-existing 3D to enhance mapping of structural and stratigraphic features and provide better spatial control, improving on previous interpretations made with only well data and 2D seismic lines.The re-processed 3D was used to re-evaluate horizon and fault mapping over the field. Using coherence-based methods, a study of regional tectonics for the area, and well correlation and performance data, we imaged a structural volume and different fault patterns originating from the main field-bounding Boscán fault. Though many of the faults do not have significant vertical offset, they appear to have pronounced effect on fluid movement and compartmentalization.Electrofacies modeling tying core to logs was used to define trends and spatial probability of reservoir and rock properties across the field. In addition, seismic attribute data was qualitatively used to help guide reservoir variability between wells and define potential depositional features within a tidally-influenced fluvial-deltaic system.Multi-point statistics (MPS) was applied to allow use of field-scale regional trends and shapes that mimic depositional features to ensure that spatial probability derived from seismic and well data could be honored. Multiple scenarios have been generated that capture the uncertainties in reservoir connectivity and associated distribution of rock quality parameters across the model area. Cells were populated with two-component lithofacies, volume of shale (VSH), effective porosity (PHIE), effective water saturation (SWE), and permeability (PERM) using a Petrophysical model developed from an extensive database of 1000ϩ wells.The full field 3D geocellular model has been downscaled to several workable smaller sector models to help address specific past performance and future dynamic behavior. Production history matching and numerical fluid flow simulation is currently underway. The focus of the history matches, in part, is to shed light on fault compartmentalization, reservoir connectivity and quality distribution, and fluid movement associated with an encroaching aquifer and water injection for pressure maintenance through time.
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