Chevron Injection Wells

Complete details of acid gas injection schemes in the literature are rare. Lock (1997) gives details of two injection schemes operated by Chevron Canada Ltd. These are the most completely described schemes available in the open literature. Other schemes are described, but too much important information is omitted to do a reasonable job of calculating the profile. 

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Figure 9.2 The calculated injection profile for the Chevron Acheson Well.

In Western Canada there are more than 40 injection schemes. The first of these, the Chevron Acheson, near Edmonton, Alberta, began in 1989 and continues in operation today (Lock, 1997). Most of these injection schemes are quite small. About 80% are less than 5 MMSCFD. However, the largest is licensed to inject about 30 MMCFD. The composition of the injected gas ranges from essentially pure COz to essentially pure H2S and most everything in between. Injection pressures (the pressure at the wellhead) range from 4 000 to 13 000 kPa (600 to 1900 psia). Well depths are typically between 1000 and 3000 m (3,300 and 9,800 ft), with the deepest at about 3500 m (11,500 ft). 

From Lock (1997) the disposal well at the Chevron West Pembina site has a depth of 2800 m (9186 ft), and the composition of the acid gas injected is approximately 21.93% carbon dioxide, 77.17% hydrogen sulfide, and 0.90% methane (dry basis). Keushnig (1995) gives the reservoir pressure of 28.8 MPa (4177 psia). Lock (1997) gives this as "about 30 000 kPa" so the value from Keushnig (1995) will be used here. It was further estimated that the reservoir temperature was 110°C (230°F) and the injection temperature was 0°C (32°F). 

Although small quantities of sour water may be disposed of by injection into deep wells or by adding to the plant waste water disposal system, these are not viable options for most plants. Normally the sour water is either processed in a sour water stripper (SWS), which produces a vapor phase containing both ammonia and acid gases, or it is selectively stripped in a two-colunon system such as the Chevron WWT process, which produces separate ammonia and hydrogen sulflde-rich gas streams. 

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