Removal of Water-Soluble Organics From Produced Brine Without Scale Formation

摘要

Water-soluble organics (WSOs) are included in the measurement of oil and grease (O&G), a conventional pollutant controlled by the Clean Water Act. WSOs partition to the produced brine at the production pH, but to the extraction solvent used to measure the O&G at the test pH of < 2. The predominant chemical species comprising WSOs in Gulf of Mexico crude oil brines are medium-chain carboxylic acids. Chemicals can be added to desolubilize these species in conjunction with treatments to remove the resultant emulsion. For a variety of reasons, the most reliable and cost-effective desolubilization agents have proven to be the nonvolatile, multiprotic oxo acids (e.g., H_xSO_x and H_xPO_x). However, in the presence of many common divalent cations in the brine, these form insoluble scale deposits. Moreover, in the presence of WSOs in mixed production, this scale becomes oil-wet and uninhibitable. A new treatment comprising a new class of desolubilizer in conjunction with certain polymers has now been shown to be equally reliable and cost-effective without the formation of scale, even at extreme concentrations of divalent cations. The chemistry is explained and case histories chronicled to illustrate its effectiveness in the field.