Abstract
A gelled foam is comprised of water, a foaming agent (surfactant), a foaming
stabilizer (polymer) and a cross-linking agent. This system with gel as the
outer phase is more stable than conventional foam that uses water as the outer
phase. Therefore, the gelled foam system prolongs the effective period of water
shutoff. By using the Ross Foamer Device to determine its foaming and stability
characters, we verify that the best foaming agent is 0.3% YG240; the stable
foam agent is 0.2– 0.4% HPAM; the cross-linking agent is 0.09% sodium
dichromate and 0.16% sodium sulphite and nitrogen. On the basis of bench-scale
evaluations of characters on gelation time and water shutoff efficiency, the
pilot test is performed on Well H1340 in the Huoshaoshan fractured reservoir.
The workover program includes washing the larger fissures using a highly
efficient oil displacement agent, injecting gelled foaming agent,
over-displacing fluids, nitrogen and water, then shutting in the well for
hardening. Field tests show that good blocking efficiency is gained in the well
with a water cut decrease of 20 – 50% and oil production increase of 3.7 – 11.0
m3/day.
Introduction
At present, most oil fields in china are in a high water cut period;
injection water and edge water usually breakthrough into oil wells along high
permeability zones, causing oil well productivity to decline and development
results of waterflooding to get worse. As conventional water shutoff techniques
such as mechanical shutoff and chemical shutoff in high permeability zones
associating with limited shutoff diameters and depth, the plugging effects
decreased rapidly and oil recovery from waterflooding has been greatly
affected. In recent years, field tests of profile control with foam have been
developed, yet high permeability zones can not be plugged effectively because
of a short half life and the limited blocking radius of foam agents. Thus, it
is necessary to study the techniques of gelled foam for in-depth water
shutoff.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
28 October 2008
- Revised manuscript received:
5 August 2009
- Manuscript approved:
5 August 2009