Maximizing Production From Gravel Packed Wells at Gullfaks Field by Stimulation and Installation of Multiphase Booster Pumps

Abstract

Abstract The Tarbert and Ness formations in Gullfaks are poorly consolidated with high porosity and productivity. Mound 50 cased hole gravel packs have been installed to date, most of which have performed well with regard to sand control. Data obtained from permanent downhole pressure gauges show a significanfly lower Productivity Index in the gravel packed wells compared to conventionally perforated producers. At increasing drawdown and watercuts, wells with PI less than 100 Sm3/D/bar (40 BBL/psi) become rate limited by the 65 bar (1000 psi) separator pressure at Gullfaks. Maintaining and improving production from the individual gravel packed wells must therefore be done by stimulation or by artificially reducing backpressure against the wellhead. Chemical treatments to remove near-wellbore damage have been effective in several cases, yielding a temporary or permanent increase in productivity and oilrate. Calcium carbonate scale can be efficiently removed by bullheading 5 % HCl. Wells which do not respond to acid or have risk of increased watercut can be mechanically stimulated by reperforating the gravel pack. This will generally induce a sand limitation. In 1994, a pilot multiphase pump unit was installed at the Gullfaks A platform to gain operating experience with the technology and improve production from two of the gravelpacked wells. The pump has proved capable of increasing production from the A-28 well by 300 Sm3/D (1800 BOPD) and has extended the lifetime of the 1000 Sm3/D A-5H well by one year. Based on the positive results of the pilot programme, 3 new multiphase pump units of higher capacity will be installed topside Gullfaks A and Gullfaks B during 1998/99. This system will be capable of boosting a total of nine wells from 45 bar manifold pressure up to the required 65 bar separator inlet pressure. P. 439