Webster Field Unit Waterflood Facilities
Authors: Moore B.L. 
Published: December 2007

The Webster Field in Harris County, Texas is one of the larger reserves operated by Exxon Company, U.S.A., and is currently being waterflooded at rates in excess of 50,000 barrels of water per day. Preliminary reservoir studies indicated a need for Preliminary reservoir studies indicated a need for water injection to control the movement of the oil column in this Frio sand reservoir and thereby increase ultimate recovery. Based on results of more detailed studies, including reservoir simulation, the field was unitized and a waterflood system was designed and built during the three year period 1972–75. The system, which provided for use of both source and produced waters, included source water wells and related facilities, water clarification facilities, injection pumps, an injection water distribution system, and injection wells. The facilities were automated through utilization of an existing field-wide Computer Production Control System.

This paper describes the planning effort associated with the design of the project, design considerations, operational results, and current surveillance activities. This surveillance program includes water quality analysis, corrosion control, and computerized preventive maintenance scheduling for the plant facilities.

Introduction

The Webster Field is located approximately 20 miles southeast of downtown Houston, Texas, as indicated in Figure 1. The field was discovered in 1937 by Humble Oil and Refining Company (now Exxon Company, U.S.A.), and contains a major oil reserve, overlain by a large gas cap and underlain by water. Since discovery. development has progressed such that the field now contains 144 wells, producing approximately 60,000 barrels of oil per day. Prior to unitization in 1973, the productive limits of the field encompassed 52 individual leases. representing more than 660 mineral royalty interests. The major producing horizon is the Frio sand occurring at approximately 6,000 feet. Major faulting in the area results in varied production drive mechanisms in various parts of the field. It was from a requirement to control the movement of the gas-oil and oil-water contacts in the largest fault segment that the Webster Waterflood Project was conceived.

This paper describes the basic design of the waterflood system, and a review of the first three years of operations. A schematic of the waterflood station is shown in Figure 2. The system consists of the following major pieces of equipment:Four 10,000 barrel inlet water settling tanks with accompanying transfer pumps.Seven up-flow rapid sand filters.Four 2,800 barrel clean water surge tanks.Three seven stage horizontal split-case centrifugal pumps each driven by a 1,400 HP natural gas fueled internal combustion engine.A distribution system consisting of more than 11 miles of internally and externally coated injection laterals varying in size from 2 7/8" OD to 8 5/8" OD connecting about 20 injection wells with the waterflood plant. Maximum working pressure on this system is 2160 psig.

The complete system is closed to exclude oxygen and the entire plant piping system is designed to allow use of both produced saltwater and water from source wells without mixing the waters. Peripheral equipment includes a complete supply gas system, skim oil recovery, storage and disposal systems, filter backwash pumps and control system, and a backwash water recovery and storage system consisting of storage tanks and a natural gas de-aeration column.

There were three significant features of the Webster Waterflood Station:The design of the inlet water settling tanks.A high level of automation incorporated into the waterflood system.