Efficient Operations In A Mature Oil And Gas Producing Area
Authors: Nisbet R.C. 
Published: December 2007

Exxon's operations in South Texas are keyed heavily on the production of gas reserves which are sold in a major intrastate industrial market. Maintaining the sales capability to this market requires a continuing aggressive effort. This paper describes Exxon's approach for meeting these sales through proper planning, development, and operation of these production properties. The "area of interest" for this paper covers Exxon's Kingsville and King Ranch Gas Plant Districts which are responsible for operating the properties in the southern portion of Exxon's South Texas Division, Production Department.

Introduction

Exxon's oil and gas operations in the "area of interest" are spread throughout a ten county area as shown in Figure 1. The majority of these operations are on Exxon leases located on several large South Texas ranches. In the 1960's, the primary emphasis in this area was on oil production and cycled gas liquids; the major markets for natural gas were just being developed. Today, the major part of the operations in this area involves gas rather than oil. Secondary recovery operations by waterflooding have been completed on most oil reservoirs where feasible. Gas cycling operations have been terminated. Current operations are keyed primarily to the blowdown of gas caps and depletion of non-associated gas reserves. Tremendous changes have occurred from the oil operations of the 1960's to gas operations of today as indicated below.

1960's Current Oil production, MB/D 100 12

Gas sales from main plant, 300a 1500 MMcf/D

Gas injected - cycling and net 900 7 ratio, MMcf/D

Waterflood injection, MB/D 121 8

a. 1962–64

Total gas production from this area now averages over 1.8 Bcf/D. The King Ranch Gas Plant, a 100% Exxon-owned facility located near Kingsville, Texas, serves as a central gas processing and conditioning center. This plant started operations in 1960 as an ambient processing facility with 1.7 Bcf/D capacity. In 1967 the plant was expanded with the addition of a more efficient refrigerated processing unit operating at -40 degrees F. The addition increased total plant capacity to a peak 2.7 Bcf/D. Over 85% of the total Exxon gas production in this area is processed through the King Ranch Gas Plant and transported by Exxon Gas System, Inc. to intrastate industrial and utility markets. The plant is currently processing about 1.6 Bcf/D of gas. Other statistical data for this producing area are listed in Table 1. There are 417 active oil completions and 1066 active gas completions.

Approximately one-half of the plant inlet gas is produced through numerous gas separation/dehydration produced through numerous gas separation/dehydration stations located in outlying fields. Two main gathering systems bring this gas into the plant at 1000 psig processing pressure; one system with dual 26" to 20" diameter pipelines pressure; one system with dual 26" to 20" diameter pipelines extends 32 miles eastward from the plant and another system with a single 24" to 10" diameter pipeline extends 81 miles southward from the plant. The remaining half of the plant inlet gas is produced from three major fields, all of plant inlet gas is produced from three major fields, all of which are located within an eight mile radius of the plant.

Cycling and pressure maintenance operations were conducted for 10 to 13 years in five major fields and involved the use of approximately 40,000 HP of reciprocating injection compressors located at the King Ranch Gas Plant and at two satellite compressor stations. The gradual phase down of cycling and pressure maintenance operations phase down of cycling and pressure maintenance operations permitted the implementation of an orderly plan for permitted the implementation of an orderly plan for recylindering and repiping these injection compressors for lower pressure boost gas service.

This paper describes Exxon's approach for the efficient management of these producing properties for economic depletion of all gas reserves. Major topics to be discussed will include (1) planning studies for the development and operation of each reservoir, (2) recylindering and repiping of cycle compressors, (3) conversion of gas gathering systems to blowdown operations, (4) relocation of gas compressor units, (5) monitoring of production operations, (6) maintenance of facilities, (7) equipment reliability review, and (8) energy conservation measures.