A Case Study Comparison of Wells Drilled With and Without MWD Directional Surveys on the Claymore Platform in the North Sea
Authors: Newton Robert , Kite Robert L. , Stone Frederick A. 
Published: December 2007

Introduction

Occidental Consortium, North Sea-Claymore Platform

Occidental of Britain Inc. and Occidental Petroleum (Caledonia) Ltd., subsidiaries of the Occidental Petroleum Corp., are operators of a North Sea Petroleum Corp., are operators of a North Sea consortium including Getty Oil (Britain) Ltd., Allied Chemical (Great Britain) Ltd., Thomson North Sea Ltd., and the British National Oil Corp. (BNOC).In March 1972 the Occidental consortium was awarded a petroleum license for six blocks in the U.K. sector of the North Sea. In May 1974, the Claymore field was discovered. Although Claymore did not have the recoverable reserves, recovery factor, or expected daily production that nearby Piper field had, Claymore still was considered a Piper field had, Claymore still was considered a viable economic proposition, especially with the proximity of the Piper field and associated oil proximity of the Piper field and associated oil pipeline from the Piper platform to the Occidental pipeline from the Piper platform to the Occidental terminal at Flotta in Orkney.The Claymore platform is 100 miles northeast of Aberdeen, Scotland, in 364 ft of water on Block 14/19. It is a twin-derricked, steel-jacketed, drilling and production platform. The platform was designed with 36 slots to accommodate 27 producing wells, eight injection wells, and one water-disposal well. Claymore was spudded in April 1977. Six wells were predrilled and 20-in. casing was set before drilling predrilled and 20-in. casing was set before drilling into the productive zone was undertaken.Main formations in the Claymore area consist of Eocene sands and silts; Paleocene sands, clays, and shales; Cretaceous limestone, chalk, shales, and sands (productive zone); Jurassic shales and sands (productive zone); Triassic shales; Zechstein limestone (productive zone); and Carboniferous shales and sands (productive zone). A geological section of the Claymore area with typical bottomhole assemblies (BHA's) is shown in Fig. 1A.From mid-1977 to late 1978, 15 directional wells were drilled from Claymore A platform using conventional wireline tool orientation and single-shot directional surveying techniques. From Sept. 1978 to Oct. 1979 the Teleco measurement-while-drilling (MWD) system was used to provide survey data and tool orientation in the drilling of 10 wells.

Teleco MWD System

Teleco Oilfield Services Inc. was formed in 1972 as a joint venture of Raymond Industries Inc. and Societe Nationale Elf Aquitaine for the purpose of developing an MWD system for directional surveying. Teleco became a public-owned company in April 1979. Following extensive technological development and field testing, commercial service was initiated in Sept. 1978 in the North Sea and Gulf of Mexico.

A comparative study was made on wells drilled on the Claymore platform in the North Sea with and without the measurement-while-drilling (MWD) system. This case study accurately quantified the direct tine savings and showed the second-tier benefits to be as significant as the direct savings.

JPT

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