Automation Facilities and Production - Leman Field

Abstract

When gas was discovered in the North Sea, it was evident from the start that adverse weather and sea conditions would make manned production platform operation difficult, and expensive. Amoco and its partners decided that automated production facilities would reduce operating costs and provide dependable and positive control of gas production. Amoco has designed and installed a shore controlled, field-wide automated production facility in the Leman Field located 38 miles offshore in the English North Sea. The system will initially control the production from 30 wells on three platforms. Gas flows through a glycol dehydration plant located on the production platform. The purpose of this plant is to obtain contractual water dewpoint and eliminate hydrate problems. The gas is then carried to shore via 30-inch pipeline. At the landfall the gas is processed in mechanical refrigeration plant which provides the required hydrocarbon dewpoint. The system is primarily designed to assure the delivery of the daily contract quantity of gas to the purchaser. Secondarily, the system provides the operator with continuous monitor of the production operation. The communication link from shore to platform consists of a solid state microwave system which includes separate channels for telemetry, telecontrol and speech. Since the whole system floats on the purchaser's pipeline, it is important that rate be accurately maintained. Individual well rates are set from shore. In case of loss of a well or individual production unit, transducers proportionally adjust each well to maintain sales rate. In addition, the system incorporates a pressure override which adjusts the rates should the purchaser's line pressure fluctuate. Production data and alarms are visually displayed and periodically printed out in the control room. Alarms which are not corrected result in a shutdown of the particular unit. Amoco U.K. and its partners, the British Gas Council, and subsidiaries of Texas Eastern Transmission Corporation and Amerada Petroleum Corporation, spudded their first well in Block 49/27 of the English North Sea on June 13, 1966. This well was completed as a gas discovery encountering 700 feet of gross pay in the Rotliegendes Sandstone. Production tests, at rates up to 25.5 MMCFPD indicated good well potential and confirmed a large structure first tapped by the Shell-Esso Group with their 49/26-1 well six miles to the northwest. This structure has subsequently proved to be a large northwest - southeast trending anticline with approximately 100 square miles of closure and gas reserves estimated at 11 trillion cubic feet. Prior to this discovery the Amoco Group had drilled a successful wildcat in Block 49/18, 27 miles to the northeast of the Leman Field. This well, the first drilled by the Group, and a successful discovery in the Rotliegendes, was tested at rates up to 25.3 MMCFPD, establishing the Indefatigable Field. Amoco and its partners decided to develop and produce these reserves as rapidly as possible. At the inception of the design phase of the drilling and production facilities for this large offshore discovery, an analysis of several reports on weather and sea conditions was made.