Offshore-Field Development Plan Changed From Steel Structures to Artificial Islands

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper OTC 22015, ’A Supergiant- Offshore-Field Development-Plan Change From Steel Structures to Artificial Islands,’ by A. Modavi, SPE, ExxonMobil Upstream Ventures; Abdul Hakeem Al Muflehi and Ihab O. Tarmoom, SPE, Zakum Development Company; Bakheet Saeed Al Khatheeri, Abu Dhabi National Oil Company; and Adil M. Noman, SPE, ExxonMobil Production Company, prepared for the 2011 Offshore Technology Conference, Houston, 2-5 May. The paper has not been peer reviewed. The field operator has a mandate to increase production by 40%. If the current steel-platform development plan were continued, many new wellhead-platform towers (WHPTs), thousands of kilometers of additional subsea pipelines, and significant facilities upgrades on existing satellites and on the central processing platform would be required. The increasing complexity and cost of such an expansion motivated a major change of the development plan through construction of artificial islands and the use of extended-reach and long-horizontal completions. Introduction The field is 84 km offshore Abu Dhabi, UAE. It was discovered in the early 1960s and covers approximately 1200 km2. Fig. 1 shows a simplified diagram of the current field infrastructure, which comprises a manned (500-person) central-platform complex and three smaller manned satellite gathering platforms. Facilities are connected by more than 1000 km of flowlines to 80 unmanned WHPTs, each having as many as 14 well slots. Before changing the development plan to the island-based concept, the plan had been to continue installing 25 new WHPTs. Significant upgrades to facilities on the existing satellite platforms and the central processing complex were planned to handle the increased oil-, gas-, and water-production streams and water injection, including requirements for future artificial lift and gas injection. Initially, field development used pattern vertical-well producers and vertical water-injection wells. The plan changed gradually to use linedrive patterns with relatively short (maximum 3,000-ft) horizontal completions. Use of the artificial-island concept as drilling and production centers for the subject field was introduced as an alternative to continued development with WHPTs. The island-based development plan uses a four-island development scenario with extended-reach-drilling (ERD) and long-reservoir-contact wells (i.e., horizontal displacements up to 30,000 ft and horizontal completions up to 10,000 ft). The development-drilling plan will be optimized continuously, taking into account new field information and new technologies. The major difference between the new plan and the previous plan is that well placement, spacing, length, and orientation take into account geological variations across the field. Compared with the old WHPT development plan, the island-based plan will double reservoir contact by use of long horizontal completions, resulting in a significant increase of the target field-plateau rate and future production reliability.