Steam Separating Solves Phase Splitting Problems in Wet Steam Distribution Systems
Authors: Rector B. P. 
Published: December 2007

Texaco operates large steam floods in the San Joaquin Valley in which Individual wellhead mass flow rates and steam quality measurements are difficult to obtain. Uneven and unpredictable phase splitting at lateral and dead end tees is the problem. In one instance, Texaco has solved this problem by utilizing a horizontal separator to separate 10,500 BPD of 70% quality cogeneration steam.

The separator is able to deliver saturated water and dry steam. These two single phase flows can be divided into any number of flow streams and then measured using simple orifice plate, differential pressure, technology.

The steam flood distribution piping consists of the separator, two single phase trunk lines running the length of the field, and small headers located along the trunk lines. The purpose of these headers is to measure, control, and combine the water and steam for each well, using orifice meters and adjustable chokes. Because each injector is controlled separately, the Injector mass flow rates and steam qualities are independent of one another. Not only does this solve the phase splitting problem, but this flexibility phase splitting problem, but this flexibility Is helpful when some Injectors need higher or lower qualities than others. For Instance, lower qualities may be warranted for displacement patterns experiencing steam breakthrough, or for occasions where patterns requiring different qualities need to be served by the same trunk line. A 36 megawatt cogeneration facility feeds the horizontal separator which is 30 feet long, 5 feet in diameter, and 2.5 inches thick. Saturated water is taken from the bottom and dry steam is taken off the top. Both these flow streams are divided in order to serve two properties. For one property, the water and steam are measured and combined right away before feeding an existing distribution system. For the other, on which a new flood is being started, the two trunk lines run the length of the field to serve the injection headers. The hardware for each injector consists of an orifice meter and choke to control the steam, an orifice meter and choke to control the water, and a fixer to combine the two flows. All this hardware is located at the header so a choke can be set while monitoring the output from the corresponding orifice meter. A spare port on one of the headers is used, not for an injector, but to serve an existing stimulation header. In this way, cogeneration steam is used to provide all the displacement and stimulation steam requirements.

One of the problems associated with this type of operation is the chemical treatment of the dry steam line. The feedwater contains a high concentration of bicarbonate. Therefore, a neutralizing amine is added to combat the high ph caused by the formation of carbonic acid. Steam samples are collected at various points along the line and are monitored for iron concentration and ph. Also, corrosion probes and corrosion coupons are used to verify data. The goal is to hold corrosion to 0.00625 inches/year (1/8 inch over 20 years).

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