Abstract
A membrane deaeration pilot study undertaken on seawater from an onshore seawater intake, successfully demonstrated removal of dissolved oxygen to less than 10 parts per billion without the use of chemical oxygen scavenger. To assess the commercial viability of adapting membrane deaeration technology to offshore oil and gas applications, a comparative evaluation of size, weight, capital cost, and operating cost for membrane deaeration versus conventional vacuum tower deaeration was performed.
The comparative evaluation considered membrane and vacuum tower deaeration technologies across a range of injection flow rates, from 30,000 – 250,000 barrels per day. Multidisciplinary engineering and design was conducted for each technology at specific injection flow rates within this range. Detailed 3D models, material take-offs, and weight reports were produced for each design. The capital cost study was prepared, with the goal to estimate direct field cost for installation of each technology. These costs were derived using quotes from vendors and installed cost norms for similar offshore installations. Operating costs were developed using quotes for consumables and estimations for power cost.
The comparative evaluation indicated that selection of membrane deaeration technology over conventional vacuum towers resulted in the following offshore facilities impacts:
60 – 70% dry and operating weight savings across the entire range of injection flow rates studied.
30 – 60% total size savings, with increased savings at elevated injection flow rates.
10% footprint savings from 125,000 – 250,000 barrels per day. The footprint of membrane deaeration is larger at small flow rates.
Selection of membrane deaeration technology over conventional vacuum towers results in the following offshore economic impacts:
10 – 15% direct field cost savings from 30,000 – 125,000 barrels per day. Direct field cost savings between 5 – 10% from 125,000 – 250,000 barrels per day, as economies of scale of vacuum towers begin to take effect.
50 – 60% annual operating cost savings across the entire range of injection flow rates studied, based partially on an assumed cost per kilowatt-hour for offshore power generation.
This study accounts for parameters which have not been addressed in previous literature to date:
Costs related to the installation of each deaeration technology on offshore topsides
Impacts on the entire topsides process due to selection of each deaeration technology (i.e., injection booster pumps, chemical injection facilities, etc.)
