Experience in Gravel Packing Long, Perforated Intervals in Deviated Holes (includes associated papers 12886 and 13309 )

Abstract

Summary This paper presents the philosophy, criteria, and technique used in arriving at the gravel-packing method for Sabah Shell Petroleum Co. Ltd. 's(SSPC's) operations. It also analyzes and discusses problems and efforts to resolve them with the aid of an evaluation tool. Introduction All the gravel-packing operations were done in the South Furious field completions. The field is located offshore northwest Borneo, some 120 miles northeast of Labuan Island. The completion intervals comprise a series of inter bedded sands and shales with porosities between 20 and30% and permeabilities of 100 to 500 md. Hydrocarbon occurrences vary from 1,100 to 7,600 ft subsea (ss). Local experiences pointed out the need to gravel-pack most of the proposed completions. Previous efforts at gravel-packing intervals, typically of less than 50 ft, had been satisfactory. However, premature screen outs were noted in intervals that were initially only some 100 ft long. The difficulties increased with increasing interval length(single gross interval of 653 ft being the longest) and deviation angle(maximum of 52deg.) and also with differences in the permeabilities of the different sand layers. To understand the nature of the problem, a neutron log was used to locate the position ofthe gravel and the presence of voids. The placement technique was modified by trial and error until an acceptable technique was achieved. This paper discusses the evolution of this technique. Completion Philosophy The limited areal extent of the sands, which stacked to form very long hydrocarbon columns, resulted incompletions across large groups of sands having common pressure regimes. Two-phase vertical-flow calculations indicated optimal tubing size to be 3 1/2 in. We set 9 5/8-in. casing across completion intervals with 4 1/2- and 6 1/8-in. wire-wrapped screens(WWS) across bottom and subsequent intervals. The coupling of the 3 1/2-in. tubing restrictedthe use of the 4 1/2-in. screen to the bottom interval. The internal gravel-pack technique was preferred over under reamed gravel pack because of greater flexibility, satisfactory in flow performance (local experience), and shorter installation time. To alleviate the need for future recompletions and high work over costs. all possible oil sands were included in the initial completion. To ensure seal integrity and minimize complexity, there was a maximum of only four zones per well. Sand Failure Criteria Experience in northwest Borneo indicated that sand control is required for zones with sonic transit times At >90usec/ft. In South Furious field, this was placed at+5,000 ft ss. JPT P. 2079^