TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA Gulf of Mexico deepwater subsea development project required seawater injection for pressure maintenance of the producing reservoir. Typical water injector performance in the Gulf of Mexico has been characterized by rapidly declining injectivities that could be partially restored by frequent acid treatments. This type of performance was unacceptable for this field development plan, which required one subsea water injector capable of injecting up to 25,000 BWPD continuously for up to five years.Two changes to typical Gulf of Mexico water injector completion design were incorporated: 1) an openhole frac pack completion, and 2) a unique downhole filter system. These changes resulted in improved water injector performance compared with that typically experienced in the Gulf of Mexico. Initial injectivity was excellent and remained so over the entire injection period. No acid stimulations were required to either initiate or maintain injection. This paper presents the design and installation aspects as well as the actual performance results for this water injector.

The Morpeth Field is located in the Ewing Bank area of the Gulf of Mexico in 1,670 feet of water. British-Borneo acquired the field in 1995 from Shell Offshore Inc (SOI) and now holds a 100% working interest in the field with SOI retaining a financial interest. The field has been developed utilizing a mono-column tension leg platform (TLP) known as SeaStar®, a proprietary design of Atlantia Offshore Limited. This paper describes British-Borneo's Morpeth Field development and entry into the deepwater Gulf of Mexico. In successfully undertaking this project, British-Borneo has demonstrated that an independent oil company can economically develop a marginal deepwater prospect using an innovative, "first of a kind" development concept. Introduction The Morpeth Field is an oil and gas development located in Ewing Bank Blocks 921, 964, and 965 in 1,670 feet of water in the Gulf of Mexico. Estimated reserves in the order of 70 mmboe make it a marginal development by typical deepwater Gulf of Mexico standards. A relatively low number of high productivity wells (each well having initial flow rates on the order of 15,000 bopd) is required for optimum reservoir development. The oil has an API gravity of 32 and a 1,000 GOR with a paraffin content of 0.77%. British-Borneo is an independent UK based oil and gas production company and has been active in the shallow waters of the Gulf of Mexico since 1989. The deepwater Gulf of Mexico was identified as a province that could offer substantial growth opportunities in terms of the excellent hydrocarbon potential and, interestingly, which also contained a number of undeveloped discoveries in various company portfolios. It was with these undeveloped discoveries in mind that in 1995, British-Borneo entered into a strategic alliance with Atlantia Offshore Limited to develop Atlantia's innovative and low cost deepwater development solution, the SeaStar® "mini" tension leg platform (TLP). The SeaStar®, which comprises a mono-column TLP, is ideally suitable for fields requiring a relatively low number of wells and little subsequent well intervention later in field life. This was seen as a key by the British-Borneo subsurface team to enable the meaningful pursuit of the undeveloped discoveries in the deepwater. One such opportunity was the Klamath Field discovered by SOI in 1991. This discovery presented an ideal opportunity for the mono-column TLP requiring a small (four) number of development wells. British-Borneo and Shell quickly consummated a deal utilizing this new technology. The field was then renamed Morpeth after the past chairman, Sir Douglas Morpeth. The field development plan was quickly agreed upon, based fundamentally upon tying back three subsea production wells and one subsea water injection well to the TLP. The wells are connected to the TLP by 4-inch ID flexible flowlines, where the TLP is host to a full processing production facility. The design capacity is for 35,000 barrels of oil per day, 42 mmscfd of gas, 28,000 barrels per day of water injection, and 10,000 barrels of produced water per day. Oil and gas are processed to trunkline specifications, then exported through steel catenary risers into the sales pipelines. Additional production can be tied into the export pipelines at a subsea tie-in sled located four miles from the platform in 1,200 feet of water. The Morpeth project was completed in 21 months from project sanction to first oil. This was 6 months earlier than first projected during conceptual engineering. Not surprisingly, some budget growth was experienced from the initial budget estimates generated early in the conceptual phase of this "first of a kind" project. While half of the cost increase was a result of signi

Sinple, eliver assisted subsea carpletions have been installed and operated successfully in many shallow water oil fields around the world. Although these simple subsea trees have not received the notoriety of their more "glam:>rous" deep-water relatives, shallow subsea trees are far nore n1.IlOOrous. Simple trees have proven themselves to be reliable, cost effective alternatives for shallow to lrediUIII water depth carpletions where "COllplex" diverless trees are not required. 'nUs paper presents a history of the developrent and evolution of simple subsea trees and describes several typical applications. The relative econanics l:ebleen "simple" and "COllplex" subsea carpletions are discussed, along with general guidelines for deterIni.nin:J when and where the use of sinple subsea is appropriate.

The Morpeth field is developed using three satellite subsea production wells and one water injection well clustered together in a line with 50 ft well spacing. The cluster of wells produces to a SeaStar mini-TLP located approximately 1500 feet to the North. The satellite wells produce through individual flowlines linked near the trees by pigging loops, reflecting a concern with wax deposition and hydrate prevention and remediation. The subsea wells are controlled through two umbilicals from the SeaStar.

No abstract