Treating water for injection in an offshore environment has always been challenging. As injection water quality becomes more stringently specified to maximize oil production across a wide range of reservoir geologies, the technical and economic complexity of treating the water dramatically increases. The more stringent treatment can include fine filtration to improve injectivity, specific ion treatment such as sulphate, calcium, magnesium removal to reduce precipitation risks and/or to enable chemical EOR, low salinity treatment for IOR/EOR, and deaeration to very low levels of oxygen to reduce corrosion.
One of the most significant aspects of this added complexity is the inherent weight and footprint of the various unit operations of the water treating facilities that are necessary to achieve rigorous treatment. The weight and footprint of these facilities directly impacts capital costs, which in turn affects the economic viability of greenfield projects and, to an even larger degree, dictates the feasibility of brownfield improvements.
The need for robust, lightweight and compact water treatment technologies for offshore injection has driven innovations in filtration, desalination, softening, sulphate removal, and deaeration. Relative to existing conventional seawater injection facilities composed of media filtration followed by vacuum tower deaeration, the subject innovations achieve an approximate 50 and 90% reduction in footprint and weight, respectively. A number of these technologies have recently undergone pilot and field testing to improve their technology readiness levels prior to full-scale commercialization, and to demonstrate capital costs savings. In addition, operating costs were evaluated. This paper presents the performance results of the pilot and field tests of two of these compact technologies: high production reverse osmosis membranes, and membrane deaeration. In addition to performance results, weight and footprint reductions associated with the technologies are provided to demonstrate the expected savings.