Four expandable completion liners (ECLs) have been run in Algeria in two fields-these are the first fully compliant ECLs in Algeria, the first worldwide in gas wells, and the first worldwide in multilateral wells (from Weatherford database). This paper presents the first detailed benchmark study of ECL performance.All systems to date have been run in 8½-in. hole using 5½-in. base-pipe ECL compliantly expanded, and the installations went well. It has been possible to compare ECL performance data against a comprehensive surveillance data set for the two fields where data from existing openhole completions allow meaningful comparisons. The other completions consist largely of slotted liners and some barefoot completions. The tested production rates in each of the wells have been high relative to normal field trends; however, the predominant factor in this is the reservoir character. Pressure-buildup (PBU) analysis indicates that the second well has reduced Darcy skin, while it is considered unproved in the first well (more data over time are needed). There is, however, consistent evidence for a reduction in the rate-dependent proportion of total skin in both wells. This is supported by other studies and a consideration of basic principles.The reduction in the rate-dependent proportion of skin has given an increase in production rate of 5-20% as compared with the computed rate from a slotted liner. This difference assumes no borehole collapse, with analyses and discussion presented of the effect on well performance should borehole collapse occur.The joint venture (JV) is investigating the further use of this technology in smaller hole sizes and possibly in conjunction with fracture stimulation.
Reservoir DescriptionsThe In Salah gas reservoirs are sandstones of Devonian and Carboniferous age. They are hard consolidated sandstones with generally low-to-moderate permeability. The fields typically have multiple sands units that are laterally extensive. The gas is dry, comprising 90-98% methane. CO 2 content varies from 1% in the Carboniferous to 10% in the Devonian reservoirs.Teg is a large four-way dip closed structure with few faults. The infill wells are in the Devonian D55 (Emsian-tidal/shallow marine sand), lower D40 (Siegenian-predominantly clean fluvial sand), and upper D30 (Gedinnian-tidal/estuarine sand/shale) sandstones. The Devonian reservoirs are fluvial to shallow-marine sandstones. Reservoir quality is usually good, with porosities up to 27% and permeabilities up to 150 md, and the sands are laterally well connected. Gas in the Devonian at Teg contains typically 90% methane with 9% CO 2 and 11 ppm H 2 S. The dewpoint at 29 bar is -46°C, water/gas ratio (WGR) is 2 bbl/MMscf, and condensate/gas ratio (CGR) is 0 bbl/MMscf. The Reg field consists of a large four-way dip closed structure covering an area of up to 350 km², which is elongated in a northwest/southeast orientation. A 3D-seismic survey acquired by the JV during the appraisal phase over the crest of the field has confirmed that the structure is exten...
