Frank Hartley , Houston
Mumbai High ESP
Worldwide, the electrical submersible pump (ESP) is an accepted high-volume lift system under a high water cut scenario of up to 11% per well. The advantages of ESP are higher liquid withdrawals, wide flexibility for off take levels, the capability to handle gas production up to 450 GOR, maximizing run life vis-à-vis reservoir response, and sustainable well and field deliverability in the post-ESP scenario. However, the risks posed by excessive gas include deterioration in head-flow performance, unstable flow and cavitations, and, ultimately, failure of the pump/motor.
The purpose of this project is to lay high voltage submarine composite electrical cable to connect various process platforms and wells in the Mumbai High field to facilitate interconnectivity of power generating systems. Initial well selection under the case study was limited to two bridge-connected wellhead platforms with three wells each. These wells are high/moderate GOR, high deviation, and high-angled ERD wells.
The project includes interconnecting 26 wellhead platforms and installing ESPs in 81 oil wells and associated surface facilities. The ESP is expected to help increase oil production from high water cut (90-95%) wells. Additionally, it also is expected to result in net saving on high pressure compressed gas of 3 MMcm/d (106 MMcf/d).
The project is scheduled to be completed by March 2012. The incremental gain of oil and gas through this will be in the order of 5.21 million tons (33.1 MMbbl) and 0.79 bcm (27.84 bcf) respectively by 2024.
MonoDiameter technology
Enventure Global Technology expanded three successive liners giving uniform inside diameter using MonoDiameter technology. With Enventure as the operator, this industry-first well was drilled and completed in April 2007.
The MonoDiameter field appraisal well included the expansion of three consecutive liners achieving a uniform 10.4 in. (26.4 cm) ID. While conventional SET technology decreases the tapering effect of wellbore casing designs. MonoDiameter eliminates it altogether, Enventure says.
“MonoDiameter is no longer a concept; it’s a reality,” says Rick Fontova, Enventure senior vice president. “This industry breakthrough helps address operators’ demands for advanced well construction solutions.”
The telescoping effect of traditional casing has been a barrier to viable economics on potentially significant reservoirs. After research and development, Enventure commissioned a well to be drilled using its MonoDiameter technology suite. The company was operator in the appraisal well and exposed the single-diameter SET systems to real-life well conditions.
“This is a significant achievement for the industry,” says Rob McKee, Technology manager for Enventure. “With the use of MonoDiameter, operators will have more control over liner lengths, enabling them to drill wells deeper with optimum hole size for production.”
Petrobras starts subsea Twister development
Twister BV has finalized a joint technology development agreement with Petrobras for the first phase of a subsea gas processing unit based on Twister technology. The project will apply the results from a 2002 feasibility study by a partnership comprising Shell, FMC-Kongsberg, and Twister BV. The study was funded by the Norwegian government under the DEMO 2000 program. It also benefits from a subsequent European Commission subsidy.
Twister treats gas at supersonic velocities to extract water and hydrocarbon liquids. It requires no chemicals, reducing environmental emissions and exposure to hazardous gas.
Petrobras has purchased a Twister unit for an onshore test expected during 2008 at the Estação Geofísico Vandemir Ferreira de Oliveira plant which processes gas from the Manati platform. The Twister gas processing module will dehydrate and dewpoint Manati gas before delivery as sales gas. The Twister dehydration and dewpointing process produces dry, single-phase export gas to eliminate many flow assurance risks and limitations associated with wet, multi-phase export.
A modular subsea gas processing system including a Twister dehydration unit.
Petrobras has identified the Canapu field in the Espírito Santo basin as the preferred location for subsea pilot system testing.
Subsea gas conditioning benefits include:
- Improved pipeline hydraulic performance. The pressure drop across the Twister process (some 25-35%) can be more than compensated by the reduced pressure drop in the export pipeline. Twister can also allow a lower pipeline design pressure
- Slug prevention. By splitting the flow into single phase gas and condensate streams, terrain or ramp-up induced slugging is prevented and slug-catchers can be avoided. Multi-phase export also limits both pipeline turndown flexibility and maximum pipeline size, sometimes necessitating multiple smaller diameter pipelines and often eliminating the flexibility to tie in future developments.
- Hydrate prevention. MEG supply lines and regeneration facilities can be eliminated. The chemistry of the produced saline formation water combined with hydrate inhibition chemicals can result in operational problems such as chemical degradation and scale deposition. Vacuum glycol desalination facilities are sometimes required to manage glycol salt contamination and its associated operational and corrosion issues
- Corrosion prevention. Twister is an option for corrosive service, which may necessitate a CRA export line, i.e. for gas compositions with a CO2 fraction in excess of 4 mol%. Effective corrosion management for wet gas CS pipelines normally requires routine pigging to maintain a protective chemical film on the inside wall of the pipeline
- Opportunities for pipeline savings where tie-in to an existing export pipeline is possible (e.g. hot tapping).
