The design of a gas storage field and associated dehydration plant for transient hourly flow is more complex than for steady-state flow. The major difference is that a transient gas flow facility requires 30 to 100 percent more capacity than a steady flow for the same daily gas rate. Further, water in the gas withdrawn from storage is not a problem under steady-state conditions but causes many operating and processing problems under transients. Low ground temperatures cause the formation of gas hydrates and free liquids in the gathering systems and plant.

The effect of these liquids is minimized, but not eliminated, by removing the free water at the wellhead and heating the gas to 125 degrees F. Careful operation is still required on startup to avoid freeze-ups and to deliver pipeline quality gas into the transmission system. pipeline quality gas into the transmission system. The water problems are analyzed qualitatively for the effect on the final design.

Introduction

A. BACKGROUND:

Colorado Interstate Gas Company (CIG) operates a natural gas storage field near Denver, its major market. A map of CIG's main transmission system and storage field is shown in Figure 1. Gas supplies are located far from Denver in Kansas, Oklahoma, Texas, and Wyoming. The Fort Morgan storage reservoir, when it is filled during the summer, supplies gas to Denver on cold days throughout the winter.

Clean, dry gas is used to fill the reservoir. However, water in the reservoir is picked up and carried back out when the stored gas is withdrawn. A dehydration plant is required at the field site to remove the water before the gas reenters the transmission system for sale to Denver.

This same site also houses injection compressors to pump the gas into the ground during the summer.

Since the Fort Morgan storage field and plant are located only 60 miles from Denver, plant are located only 60 miles from Denver, they undergo quite variable gas flow rates and pressures. The unusual features of the design to handle the transient operations are the main topic of this paper.

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