Schlumberger

Case Study: StethoScope Service Maximizes Oil Recovery Offshore Brazil

Analysis of fluid dynamic behavior and reservoir connectivity reveals need to accelerate injection well drilling

Challenge: Acquire formation pressures in highly deviated wells to appraise reservoir in deepwater field offshore Brazil.

Solution: Use StethoScope formation pressure-while-drilling service and TOP time-optimized pretests.

Result:

  • Determined dynamic process of reservoir fluids.
  • Detected nonlinear reservoir depletion.
  • Proved existence of long lateral reservoir connectivity.
  • Redefined true bubble pressure value.
  • Discovered potential increase in oil reserves.

Improve understanding of dynamic reservoir behavior

An operator was conducting an extensive drilling campaign to appraise a reservoir in a deepwater field offshore Brazil. During the campaign’s exploration phase, MDT modular formation dynamics tester runs were made in all channels of the pilot wells at virgin conditions. Analysis of the results showed that the pressure gradient had a constant value that corresponded to a homogeneous hydrocarbon (black oil) from base to top of the upper reservoir sand channels. A single fluid phase also was found in the lower channels located in the sandstone interval.

As the campaign moved into the development phase, the operator wanted to acquire detailed formation pressure information to improve understanding of connectivity and dynamic reservoir behavior to optimize production. Well deviation and complex trajectories created challenges in acquiring the pressure information.

Identify fluid phase change

The StethoScope service and TOP pretests provided the pressure information the operator needed. By using a setting piston to push the packer with the test probe against the formation, the StethoScope service created a seal, regardless of probe orientation or wellbore deviation. TOP pretests automatically reduced acquisition time to just 5 minutes by adjusting test rate and drawdown volume to the conditions encountered.

Formation pressures measured at various depths identified a change in the fluid phase from black oil at the base of the reservoir to free gas at the top. This multiphase behavior, contrasted with the single-fluid phase found in the exploration pilot wells, indicated that the reservoir fluids were undergoing a dynamic process.

Maximize oil recovery

Analysis of the formation pressure information provided by the StethoScope service and TOP pretests was instrumental in determining the dynamic process of the reservoir fluids. It was also instrumental in detecting nonlinear reservoir depletion, proving the existence of long lateral reservoir connectivity, redefining the true bubble pressure value, and discovering a potential increase in oil reserves. The results of this analysis revealed the need to accelerate drilling of injection wells for pressure maintenance to optimize potential oil recovery. Short-term plans for field development include the acquisition of pressure measurements in all injector and pilot wells to further improve understanding of reservoir behavior and maximize oil production.


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