The Argyll Field was discovered in 1971, brought on stream in 1975, and has the distinction of being the first oil producing field in the U.K. North Sea. Development wells have been completed with sub-sea wellheads and connected by flow lines to a floating production platform. After ten years of production the field has produced over fifty million barrels of oil. Development drilling has proved commercial oil from five reservoir zones in rocks ranging in age from Devonian to late Jurassic. The geology of each zone is discussed in relation to environments of deposition, structure and reservoir parameters. Field development and performance are reviewed and the timing and contribution of each reservoir to the production history are described. The benefits which have been achieved from continuing geological, petrophysical and engineering studies for identifying and establishing petrophysical and engineering studies for identifying and establishing further development possibilities are emphasised. The complex nature of the reservoir and its effect on fluid movement and productivity are explained. The field has been produced by natural depletion which has been achieved by virtue of an effident water drive. This paper highlights the importance of geology and engineering in reservoir development planning. Introduction The Argyll Field was discovered in 1971, brought on stream in 1975, and has the distinction of being the first oil production field in the U.K. North Sea. It is located in the central North Sea, some 200 miles east of Montrose, Scotland (Figure 1). The field structure is a tilted fault block measuring some 7 km by 2.5 km and enclosing a productive area of approximately 2800 acres (figure 2). The structure lies mainly in U.K. Block 30/24 and partly in Block 30/25a. Water depths in this area vary from 246 to 265 feet. By the end of 1984, the field had produced 53.1 MMSTBO. Block 30/24 constitutes part of U.K. Licence P073 awarded as part of the U.K. first licensing round in September, 1964. The field is operated by Hamilton Brothers Oil and Gas Limited. The Partner participants' interests are: Hamilton Oil GB Plc (28.8%), Hamilton Brothers Petroleum (U.K.) Ltd (7.2%), RTZ Oil and Gas Ltd (25.0%), Texaco North Sea U.K. Co Ltd (24.0%), Blackfriars Oil Company Ltd (12.5%) and The Trans-European Company Ltd (2.5%).

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This paper presents the integrated approach for the redevelopment of the waterflood in Howard-Glasscock field located primarily in Howard County, Texas. Originally discovered in 1925, the majority of production is now commingled across the Guadalupe, Glorieta and Clearfork formations. This is a mature field which is currently in the midst of a 5 and 10 acre infill drilling program that began in 2009. Emphasis has primarily been focused on drilling producing wells, but the basis for this project was to optimize an existing waterflood to guide the development strategy of the field moving forward.A study of the production of the wells drilled since 2009 identified stronger performance in wells with offset waterflood support. On average, waterflood was responsible for a 22% improvement in the expected recovery per well, despite a lack of patterns or a comprehensive waterflood management plan. As a result, a multi-disciplined team was commissioned to design a strategy for the redevelopment of the flood and more active management of the daily operations. Geology and reservoir engineering aspects were used to characterize the reservoir in conjunction with classical waterflood methods to understand the current performance and validate the expectations for secondary recovery.Fracture orientation was studied based on cases of early breakthrough and was utilized in pattern identification and well placement to maximize sweep and discourage direct communication between injectors and producers. Further, the success of the waterflood in Howard-Glasscock relies on the ability to control the flow of water over a 2,000 foot vertical interval. To address this, the team has implemented a surveillance plan with improved monitoring and communication with the operations team to enhance the collection of data and in order to react to the dynamics of a waterflood. The rapid response to injection observed in this field requires proper surveillance and timely control of water flow which ultimately drives the success of the program by moving water from high water cut intervals to bypassed oil zones.This paper details the systematic approach that was used to design the redevelopment plan for a waterflood in a 90 year old field. The scope of work is being implemented and represents an adjustment in the development plan of Howard-Glasscock moving forward. Ultimately, the enhanced performance observed in recent drilling programs and the continued success of development in this mature field hinges on understanding and managing the waterflood moving forward.