New Technology Applications for Improved Attic-Oil Recovery: Slim Smart Completions

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper IPTC 12365, "New Technology Applications for Improved Attic-Oil Recovery: The World's First Slim Smart Completions," by Stig Lyngra, SPE, Abdulkareem M. Al-Sofi, SPE, Uthman F. Al-Otaibi, SPE, Mohammed J. Alshakhs, SPE, and Ahmad A. Al-Alawi, SPE, Saudi Aramco, prepared for the 2008 International Petroleum Technology Conference, Kuala Lumpur, 3-5 December. The paper has not been peer reviewed. Smart completions, passive inflow-control devices (ICDs), and maximum-reservoir-contact (MRC) wells are some recent technologies used to enhance recovery and extend the life of mature oil fields. In a Saudi Aramco field, one challenge was to maximize production from the inadequately swept attic-oil zone. Since 1995, new technology has improved oil recovery from this thin attic-oil zone. Technology deployments included recompletion with short-radius-horizontal (SRH) sidetracks, single-lateral re-entry sidetracks equipped with passive ICDs, and multilateral MRC wells equipped with intelligent completions. A slim smart completion (SSC) was run in a multilateral sidetrack enabling production optimization and control of individual laterals. Introduction This field in Saudi Arabia was discovered in the early 1940s. A pressure-support program was started after 8 years of primary depletion. During a 24-year period, the produced solution gas was reinjected as part of the reservoir-pressure-support program. Gas injection was into the primary reservoir at the crest of a high-relief dome feature. A flank water-injection program was started in the mid-1950s, and it became the main field pressure-support mechanism. After more than 60 years of production, approximately 57% of the oil initially in place in the primary reservoir has been produced. Still, the field water cut has remained less than 35%. The absence of vertical barriers, relatively long distance from injector to first-row producers, and managed production offtake have allowed gravity to play the primary role in the recovery process. The main-reservoir permeability distribution (higher permeability toward the top, excluding the top 25 ft) allowed oil production from the top section while gravity drainage occurred in the lower, poorer reservoir section. As a result, water production has been very limited. The normal production practice during the first 34 years was to shut in any producing well with crude samples containing salt. Attic-Oil Target Zone The attic-oil section is approximately 25 ft thick. Saturation logs run in 2007 in wells very close to flank injectors indicated that this interval is at original oil saturations. Fig. 1 is a schematic showing the main layering of the attic-oil interval.