Wells – Processes – Cementing – plugging or consolidating
Patent
1998-04-23
2000-07-04
Neuder, William
Wells
Processes
Cementing, plugging or consolidating
166300, E21B 3313
Patent
active
060824565
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns an agent and a method for establishing different types of zone sealings in oil wells, gas wells and other well types located onshore or in the seabead, including wells in connection with exploitation of ground water.
DESCRIPTION OF RELATED ART
When sealing water producing layers or establishing the sealing of well zones, coiled tubing or interconnectable pipes are inserted, the latter also used as drill stem which can be provided with expanding sealings to shut off the casing section in the zone in question. The zone to become isolated is then supplied with a sealant which is allowed to set and hence shut off the zone.
In the case of oil wells, this is done to shut off undesirable water or gas supply, and in the case of gas wells, is done to establish a seal against water supply and to isolate polluted zones in ground water wells.
Moreover, there may be a need for sealing the annulus between the tubing and the casing in wells because of damage to the tubing caused by collapse in formation and subsequent damage to pipes.
Another type of sealing method involves a shut off plug for wells which are to be shut off permanently or temporarily, or a so-called "kick-off" plug to prepare a site for the drilling of a new well from the remaining upper section of a former well.
In the drilling of multiple branched wells there is a need to reinforce and seal the transition zones of the surrounding formation. These transition zones are subject to large mechanical stresses.
The prior art methods make use of cement. However, a disadvantage of cement is that the curing step may require up to 24 hours, which is a disproportionately long period of time, and waiting time on the production site is a very costly operation when offshore. Another disadvantage is that the strength of cured cement material in certain applications is insufficient. A further disadvantage of cement is that in view of its particle based structure the material exhibits a relatively poor penetration capability in formations, which again may result in a reduced sealing effect.
NO Patent 176878 describes a polymer-based cementing agent for use in warm zones of a well at a temperature of 120-200.degree. C., comprising diallylphthalate (DAP), including isomers, prepolymers and/or oligomers of the same. The agent comprising the filler material among other things is polymerized by means of an initiator (organic peroxide) and prepares a cured sealing mass for different applications. A polymer based sealant of the type described in this patent has the general advantage of exhibiting relatively rapid curing after setting, contrary to cement in which the mass first sets and then cures gradually with time. The sealant of NO Patent 176878 is not applicable to well zones having more moderate temperatures, such as 5-120.degree. C., and in many applications the curing time of the sealant will be too long and the mechanical strength of the cured mass will be too low. Another disadvantage of the unmodified DAP based polymer in such fields of application is that the cured polymer shrinks by 10-15 vol % compared to the starting composition. Therefore, the composition will have to be supplied with a shrink compensating additive in the form of a pre-dried bentonite.
SUMMARY OF THE INVENTION
The main object of the invention is to provide a polymer based sealant of the type described above for establishing different types of seals in well zones having a temperature of from 5 to 120.degree. C., and wherein the sealant cures more rapidly, results in higher strength and reduces shrink in cured material, compared to prior art agents.
This object is achieved by an agent and a method according to the invention, where the agent according to the invention comprises a monomer, an initiator, an inhibitor and optionally a filler as well as other additives. According to the invention, the agent comprises a prepolymer in the form of an at least partially unsaturated polyester or epoxy vinylester, and moreover at least one vinyl-conta
REFERENCES:
patent: 3635289 (1972-01-01), Van Dyk
patent: 5212234 (1993-05-01), Van Grasse et al.
patent: 5436396 (1995-07-01), Bailey et al.
Dahl-Jorgensen Einar
ye Bjarte Arne
Neuder William
Walker Zakiya
Wecem AS
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