Shushufindi adopts subsurface workflows on Delfi for optimized drilling campaign
Background
Consortium Shushufindi (CSSFD) manages a services contract with Ecuador’s national oil company, Petroecuador, for the Shushufindi-Aguarico oilfield—a 3.9 billion bbl original-oil-in-place field with 160 wells covering an area of approximately 400 km2.
The production is mostly light oil, coming mainly from Cretaceous fluvio-estuarine and shallow marine U and T sandstones in the Napo formation, with mild to strong aquifer support. Production started in 1972, and today the average recovery factor stands at 33%. The field is associated to an elongated anticline in a north-south direction, limited to the east by inverted faults.
Challenge
The Shushufindi-Aguarico field reached a peak production of 120,000 bbl/d in 1986, and declined in yield until water injection started in U reservoir in 2014. The field is currently producing 58,000 bbl/d, mostly from two primary reservoirs (out of five productive formations) through vertical and deviated wells.
As in many other mature fields, Shushufindi-Aguarico faces challenges due to continued depletion of the most homogenous reservoirs, water encroachment, and higher water cut on structural flanks.
The field development strategy focused on drilling deviated wells that could target several reservoirs to be produced individually. Due to environmental sensitivity, and the need to reduce production footprints in the Amazon region, wells are drilled in clusters that currently hold up to 12 wells. Well architecture has been evolving from S and J-type wells, to highly deviated J-type wells.
Increasing the recovery factor is a critical objective that has been approached by improving sweep efficiency through reservoir pressure support and water flooding optimization, evaluating secondary reservoirs, as well as assessing bypassed oil in the attic of the structure of the main reservoirs. Bypassed oil in the attic refers to oil in the uppermost reservoir subunits, that has been proven successfully in recent deviated wells.
A field development plan for a new drilling campaign to increase the recovery factor, which also targeted bypassed oil in the attic, required a higher stratigraphical subunit resolution, for a thorough and rigorous analytical interpretation of key data, including 3D seismic, core data, drilling cuttings, conventional and special wireline logs.
Uncertainty quantification for controlled risks also necessitated the processing of thousands of dynamic simulations. Building and evaluating these field development plans under uncertainty is a time-consuming task, with traditional on-premises solutions and infrastructure unsuitable for non-stop operations.
Solution
Adopting subsurface profiles and On Demand Reservoir Simulation on Delfi™, CSSFD was able to generate an optimized field development plan for a new drilling campaign, to increase the recovery factor, targeting bypassed oil in the attic.
The field development scenario was then defined, incorporating the attic oil analytical foundations, and running thousands of dynamic simulations to identify additional areas of remaining bypassed oil, with a view to quantifying the production associated with the most efficient well geometry to drain them. This attic oil has paradigm shifting potential for future field development.
Leveraging the Delfi platform’s best-in-class domain science, workflow integration and cloud scalability, an optimized field development plan could be generated in two months—a third of the time it would normally take. The Delfi platform also enabled CSSFD to speed up the simulation processes, and take advantage of the capability to run multiple different scenarios varying quantity, well-spacing and well geometry in a short period of time.
Each candidate well location was assessed in terms of production profile and estimated ultimate recovery, considering their respective uncertainty range. This workflow also allowed a rapid comparison of deviated wells versus horizontal wells.
Once each location was delineated, an optimization analysis was performed to define the optimal horizontal section lengths, and run uncertainty analyses on the effective reservoir length, and the impact on initial oil rate, water rate, and cumulative production.
Both analytical and numerical simulation results were cross-checked. The analytical scenario identified two areas of focus—and the simulation using the Delfi platform added further five—to be assessed by a multi-discipline team. In total, four areas of concentration were retained in the final field development plan.
Results
Leveraging the Delfi platform’s best-in-class domain science, workflow integration and cloud scalability, an optimized field development plan could be generated in two months, versus the six months it would have taken with traditional on premises solutions. Simulation studies that used to take more than 12 hours on premises, could be completed in less than an hour with On Demand Reservoir Simulation on Delfi.
The results of the optimization study obtained for all the areas of interest, highlighted nine horizontal well opportunities. Drilling horizontal wells was identified as the best strategy, preferred over the deviated commingle completion, as the volume recovered by horizontal wells represented new reserves that could not be drained otherwise. In the areas chosen, and compared to the deviated wells approach, horizontal wells were projected to improve the initial oil production rate by a factor of 2.5, and double the estimated ultimate recovery, resulting in a more economically attractive development plan.
Drilling horizontal wells is also aligned with CSSFD’s commitment to reduce CO2 emissions, since a single horizontal well can replace at least two deviated wells, reducing drilling and supervision time, and minimizing the environmental footprint in the region. This combined methodology allowed CSSFD to prove the potential of bypassed attic oil, and propose a pilot horizontal well to be drilled during 2023 in one of the selected areas. This approach could fundamentally change the way the company exploits the field
