Abstract

Texaco operates several large steamflood projects in the Southern 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 (Hong, 1978,) 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 96.5% quality 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 two singlephase trunk lines running the length of the field to serve small headers located near the steam injectors. The purpose of these headers is to measure and control 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, this flexibility allows some injectors to receive higher or lower qualities than others. For instance, lower qualities may be warranted for patterns experiencing steam breakthrough, or for areas of the field in which the flood is more mature.

One of the problems associated with this type of operation is the chemical treatment of the dry steam line. A neutralizing amine needs to be added to combat the high pH caused by the formation of carbonic acid. The goal is to hold corrosion to 6.25 mpy (1/8 " over 20 years).

This paper addresses the system design, flow measurement, and automatic control apparatus, as well as the details, results, and sampling techniques of the chemical program.

The Problem: How to Split Flow

To satisfy part of the steam demand for thermal development in the Midway-Sunset field (Bakersfield, California) Texaco contracted to buy approximately 10,500 BPD of steam. The steam, which is supplied from a nearby cogeneration facility, was to serve the stimulation and displacement needs of several properties. The expenses charged to the properties come from two sources. The feedwater, which is delivered by Texaco's Central Water Plant, is charged on a volumetric basis. The cogeneration acility charges for energy added to the feedwater. Therefore, any distribution system needs to accurately measure both volume and energy (quality) for proper expense accounting. Accurate accounting is especially important for properties where substitute fuel agreements or other partners are involved, because outside parties are particularly interested in steam costs charged to them. Both of these situations exist for Texaco in the Midway-Sunset Field.

Currently the steam is divided between just two properties. Section 36 and Government 35, both of Township 315, Range 22E, MDBM. However, the system needed to be designed so the the flow could be divided between any number of properties. Using a standard steam header with common lateral lees was prohibitive because of disproportionate phase splitting.

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