Summary
Migration of formation fines has been shown to cause production decline in
many wells. Despite the availability of new downhole tools for use in well
stimulation and completion, the ability to sustain desired production levels is
often plagued with fines migration problems. The solution to this problem is
appropriate treatment to mitigate fines migration at its source. This paper
describes the use of an ultra-thin tackifying agent (UTTA) for stabilizing
fines in high-rate producing or injection wells. This UTTA is applied as part
of an initial prepad in fracturing or gravel-packing operations, as a remedial
treatment, or as a post-treatment following acid fracturing or matrix acidizing
treatments. The primary purpose of UTTA application is to immobilize formation
fines so that they will not detach, migrate with flowing fluids, plug the pore
channels, and reduce the flow path permeability.
Results of laboratory testing indicate that the UTTA system is applicable to
most types of formation fines, including coals, sandstones, and carbonates.
Once injected into the formation matrix or proppant pack, the UTTA forms a thin
film on formation surfaces, encapsulating the fines. Capillary action helps
pull the tackifier into the contact points, fixing the particulate in place
without plugging the pore throat. The UTTA does not require a shut-in time
after its application. The thin film tackifier does not harden, but remains
flexible, enhancing the ability of a formation to withstand stress cycling and
allowing the formation to handle high shear stress during high flow rates.
Introduction
Hibbeler et al. (2003) provide an excellent review of fines migration
mechanisms. Many investigators have examined factors affecting permeability
decline because of fines migration and clay swelling, including salinity
changes, pH, and flow rate (Muecke 1979; Gruesbeck and Collins 1982). Migration
of formation fines is known to cause severe formation damage during production,
limiting the potential production of the well.
Various techniques have been developed in the industry over the years as
fines-stabilizing solutions to overcome the effects of fines migration (Muecke
1979; Sharma and Sharma 1994). Acidizing has often been used to dissolve fines
by “unblocking” and enlarging pore-throat geometry in the formation near the
wellbore to increase the permeability of the formation. Production performance
in wells that have been acidized or acid-fractured has often been
disappointing. High production rates typically last only a short time, followed
by a drastic drop in production because of the damage caused by fines plugging.
Other chemical treatments, such as the inclusion of clay-stabilizing
surfactants as part of the completion fluids, or polymers in remedial
operations, have been applied in an effort to minimize fines migration and
enhance well productivity (Kalfayan and Watkins 1990; McLaughlin and Weaver
1982; McLaughlin et al. 1976). These treatments commonly require that the
treatment fluids be injected deep into the formation matrix, allowing the
surfaces of the fines and pores to contact and interact with the treating
fluid. Large volumes of treating fluid are often required to achieve the
desired results. Most such treatment fluids provide only temporary solutions
because they tend to desorb with time and with the production of fluids from
the well.
© 2007. Society of Petroleum Engineers
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History
- Original manuscript received:
31 August 2005
- Revised manuscript received:
2 October 2006
- Manuscript approved:
3 October 2006
- Version of record:
20 May 2007
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