API Publ 4717:2002 pdf download

API Publ 4717:2002 pdf download.Predictors of Water-soluble Organics (WS0s) in Produced Water- A Literature Review.
2 Chemical Composition of Produced Water
2.1 ORIGINS OF PRODUCED WATER
During millions of years of geologic time, petroleum and natural gas may accumulate in porous scdinwnts (e.g., sands) trapped between layers ohmpcrrncablc rock deep within the earth (Collins. 1975). ‘Miter may be trapped during millions of years with the oil and gas. This water may be derived from ancicnt fresh or salt water (connate water) and often is as old as the fissil fuels in the reservoir. When the hydrocarbon reservoir is tapped by a well, the produced gases and fluids may contain connate water. Also, in some oil fields, fresh or salt waler may be injected into the reservoir through injection wells to displace oil toward the production wells. Sometimes, this injection water channels through to the production well and is produced with the oil and gas. The water produced with oil and gas is called produced water. produced ftinnation water. or oiltield brine (Net1 1987. 1997: Black et al. 1994).
Belire the crude oil can be refined or the gas processed, the water must be removed, During offshore operations. separation of the produced water from the oil and gas may take place on the production platform or the oil/gas/water mixture may be sent through a pipeline to a shore faciliy where the produced waWr is separated from the oil and gas. If no re-injected, the produced water is treated to meet regulatory limits 11w oil and grease so it may be discharged to the ocean from the platlonn or from an ocean outfall from a shore-based treatment facility. The current limit for total oil and grease in produced water destined kr ocean disposal in U.S. Federal and Upper Cook Inlet. AK, waters is 42 mg/I ppm) daily maximum and 29 mgI L monthly average (Otto and Arnold. 1996: Veil, 1997).
The oillgaslwater mixture may be processed through devices to separate the three phases from one another. On western Gulf of Mexico platforms, the types of equipment used to remove oil and grease from produced water include, in order of frequency of use, mechanical and hydraulic gas floatation unils, skimrner.. coalescers. hydnicyclones. and filters (Otto and Arnold. 1996). Chemicals may be added to the process stream to improve the efficiency of oiL/gas/water separation. Even with the most advanced separation equipment. the oil/water separation is not l00° efficient. If the oil/water separation system is efficient. however, most of the chemicals remaining in the treated produced water are in solution or colloidal suspension in the water.
To prevent corrosion. foaming, scale formation, hydrogen sulfide formation, and bacterial growth, or to improve the efficiency and completeness of oiL/water separation. small amounts of specialty chemicals may be added to the production stream at different steps in the production and treatnwnt process (Hudgins. 1989. 1991, 1992). Most of these chemicals remain in the oil or gas phase: others are water-soluble, remain in the produced water, and are discharged. Approximately l9’/o of the ofFshore production chemicals used on platf&rns in the North Sea are discharged in treated produced water. including more than 50% of the emulsiflers, surtlictanis, oi removing agents, and scale inhihitcws(van 1-kittum et al.. 1992:
Ynnesdal and Furuholt, 1994: Hudgins, 1994). Only small amounts (less than 20% of the amounts used) of corrosion inhibitors, oxygen scavengers, emulsion breakers. defoamers. and gas treatment agents are discharged with produced waler.