Abstract
This paper presents a unique case study on offshore exploration to prove the commercial potential of oil reserves in the Gulf. It describes the design of a downhole testing platform with a new type of pump. An operating company drilled new appraisal wells to evaluate the presence of multizone reservoirs with heavy oil. The objectives were to confirm the presence of oil reservoirs and well deliverability and prove the field development concept. The well test included the production of heavy oil with an electrical submersible progressive cavity pump (ESPCP) under different regimes, followed by the build-up. The surface testing system was used to manage the fluid at the surface and measure the flow rates. The downhole testing system (DST) was integrated with ESPCP to lift the fluid and to use wireless real-time telemetry to measure the pressure and temperature at different depths.
The reservoir testing was highly successful in proving the commercial potential of the new reserves. The ESPCP was a key element in ensuring continuous reservoir fluid flowing to the surface to achieve flow stability for accurate estimation of the productivity index. Moreover, the progressive nature of the pumping minimized the effect of asphaltene and wax deposition, which could have solidified the fluid in the wellbore during the shut-in period, requiring intervention with coiled tubing.
The ESPCP system is designed for large range of flow rates and features a specialized Y-tool to address potential contingencies. This solution represents a global pioneering implementation aimed at mitigating the risks associated with electrical generation from the permanent magnet motor (PMM) during well completion and retrieval processes. Additionally, the novel well schematic architecture facilitates well interventions using coiled tubing (CT) and sand screen control, enhancing operational efficiency and safety. The stimulation system was designed to improve reservoir productivity by respecting the pump limitations in terms of pH. It also required that the pump material be upgraded to be able to lift corrosive fluid such as acid.
The downhole testing system allowed us to record the build-up with downhole shut-in, obtain reservoir fluid samples without intervention, and record the data in real time for pressure transient interpretation. Real-time monitoring allowed us to interpret the data in real time and optimize the test duration. Combining multiple gauges at different depths allowed us to evaluate friction losses in completion during high viscous fluid production.
For the first time, the ESPCP was integrated with conventional downhole testing to lift heavy oil reservoirs offshore for production evaluation. In this paper, we provide details about the unique workflow, the lessons learned, and recommendations to the industry based on nine production tests at three wells.
