Polymer Use in Blowout Control

Abstract

This paper describes a unique application of polymers in a blowout of a high-capacity gas well in the Middle East. The polymers effectively assisted in controlling the blowout by polymers effectively assisted in controlling the blowout by filling up cavities in the formation and diverting or preventing hydrocarbons from entering the wellbore. Although the well was not brought under control completely, the material did reduce the flow rate enough to extinguish the flame. Introduction Blowouts in high-capacity formations require high pump and capture rates for control, even when subsurface communication between the relief hole(s) and the uncontrolled well is good. Control fluids are carried out of the hole by high-velocity flow. A hydrostatic head large enough to overbalance the formation pressure cannot be obtained. Hole enlargement also creates difficulty by retaining control fluids or by causing their dilution with formation fluids before they can take effect. Polymers can be used effectively to reduce the flow rate from the uncontrolled well so that control fluids kept in the hole can control the well. Also, polymers can be used to fill enlarged hole spots and alleviate control-fluid retention or dilution downhole. Using polymers for blowout control evolved during a lengthy control effort of an offshore-Dubai platform development well. The well blew out on July 19, 1975, and flowed uncontrolled until Feb. 24, 1976. Four attempts were made to control the well by directly pumping sea water and mud before using polymers during the fifth attempt. The blowout was not controlled completely, but the gas flow rate was reduced and the flame actually was extinguished. The supply of the most effective polymer became exhausted, so the control operation was terminated. Plans for the next attempt included extensive use Plans for the next attempt included extensive use of polymers; however, the hole was bridged and gas flow ceased, making further control measures unnecessary. Polymers will not be the key to well control every time, but they showed great promise in the Dubai situation and should be a valuable aid to control blowouts. The Blowout The Fateh field L-3 development well had reached 4,180 ft (515 ft below the Asmari gas-water contact) when the kick occurred. A 30-in. conductor had been driven to refusal at 450 ft and a full string of 20-in. casing was cemented at 1,310 ft. The kick control effort was terminated and the rig abandoned when gas broke around the 20-in. shoe and bubbled up under the platform. Eight days after the blowout, the gas ignited and in 2 weeks the rig and platform disappeared beneath the Arabian Gulf. The Asmari limestone formation in the Fateh field has a total thickness of about 540 ft, with a 115-ft gas column at Well L-3. The upper part of the Asmari is vuggy and fractured with permeabilities of several hundred millidarcies. The lower portion of the Asmari is shaly and relatively tight. The entire section of the Asmari gas and water columns was open to the 17 1/2-in. wellbore, resulting in a high-rate gas flow with an indeterminable amount of entrained water. Control Effort Before the well ignited, efforts were made to move barges up to the platform so that surface control measures could be tried. JPT P. 705