Hawkins Inert Gas Plant: Design And Early Operation
Authors: Kuehm Harold G. 
Published: December 2007

The Hawkins Inert Gas Plant, largest of its type in the industry, is located approximately 20 miles north of Tyler, Texas. This paper describes the design features of a pressure maintenance compressor plant intended to inject an average daily volume of 120 MMscf/D of boiler flue gas into the Hawkins Woodbine Reservoir, the equipment included to convert the potentially corrosive elements in the exhaust gas into safe components, the more significant design problems that developed during design and start tip, construction details of the new plant, and the early operating history of this unique installation.

Introduction

On January 1, 1975 the Hawkins Field, located about 20 miles north of Tyler, Texas, was unitized with approval of the Texas Railroad Commission. Unitization represented the culmination of many years of effort by both Exxon and the other Unit owners. This date also signaled the formal beginning of the design, and later construction and operation, of the Hawkins Inert Gas Plant.

Extensive reservoir studies prior to Field unitization indicated a need to use gas drive rather than the natural water drive to maximize Field recovery, and to minimize and then prevent residual oil loss as a result of oil movement into the gas cap, because of the gradual decline in the gas cap pressure. Because sufficient natural gas traditionally used in the industry was not available either in the Hawkins Field or elsewhere on an economical basis, a plan was devised and approved to use steam boiler exhaust gas for pressure maintenance injection needs. Steam produced in the inert gas generators would be used to drive the steam turbines that in turn drive the compressors used to compress the boiler exhaust gas.

This paper describes the design features of a pressure maintenance plant intended to inject an average daily volume of 120 MMscf/D of boiler exhaust gas into the reservoir, the equipment included to convert the potentially corrosive elements in boiler exhaust gas into inert safe components, the more significant problems that developed during design and startup, construction details of the new plant, and the early operating history of this unique new installation. It will not address any aspect of Field unitization or additional reservoir oil recovery that will be achieved as a result of operating this new inert gas plant. Further, no attempt will be made to compare the design and results to comparable processes. processes.

DESIGN

The inert plant is made up of three identical trains operating in parallel. Figure 1 shows schematically the major items for one train. Following the flow from left to right, each train has two inert gas generators (steam boilers), two catalytic reactors, a direct contact cooler, a 20,000 BHP compressor train driven by a steam turbine, and an inert gas dry bed dehydration unit. There are five stages of compression in 22 wheels and 3 cases that compress the inert gas from 0 psig to 1800 psig. Each train is designed to produce 44 MMscf/D of inert gas for a total design capacity of 132 MMscf/D. Considering normal downtime for preventive maintenance, annual average injection preventive maintenance, annual average injection rates were targeted for 120 MMscf/D from the Plant. Plant. Corrosion is the single most important operating disadvantage of using; boilers and/or engine exhaust gases for oil field pressure maintenance service.