ABSTRACT
Produced water (PW) is the water associated with hydrocarbons during the extraction of oil and gas (O&G) from either conventional or unconventional resources. Existing efforts to enhance PW management systems include the development of novel membrane materials for oil-water separation. In attempting to evaluate these emerging physical separation technologies, researchers develop various formulations of test solutions aiming to represent actual PW. However, there is no clear scientific guideline published in the literature about how such a recipe should be prepared. This article develops a protocol for preparing synthetic solutions representing the characteristics and behavior of actual PW and enabling the performance comparisons of different oil-water separation membranes at the bench scale level. In this study, two different brine recipes were prepared based on salts present in actual PW, crude oil was used as the hydrocarbon source, and a surfactant was added to disperse the oil into the aqueous phase. The recipe is accessible to the wider scientific community and was proven to be reproduceable, homogenous, stable, and comparable to actual PW field samples through analytical monitoring measurements and bench scale evaluations.
ABSTRACT
Produced and process water (PPW) from oil and gas operations, specifically in Qatar, are disposed of by deep well injection in onshore facilities. Disposing large volumes of PPW may affect deep well formation sustainability highlighting the need for effective PPW management. Forward osmosis (FO) was applied as an "osmotic concentration" process to reduce PPW injection volumes by 50% using brines and seawater as draw solutions (DS). The energy intensive step of restoring the salinity of the DS was eliminated; the diluted DS would be simply discharged to the ocean. Both hollow fiber and flat sheet FO membranes were tested and the former exhibited better flux and rejection; they are the focus of this study. Optimization experiments, conducted using Box-Behnken statistical design, confirmed that temperature and DS concentration had a substantial effect on performance. To validate the concept, a long-term experiment, under optimized conditions, was conducted with PPW as feed and brine from thermal desalination plant as DS which yielded an average flux of 24 L/m(2)h. The results confirmed that low-energy osmotic concentration FO has the potential for full-scale implementation to reduce PPW injection volumes. Pilot testing opportunities are being evaluated to demonstrate the effectiveness of this technology under field conditions.
