Wells – Processes – Cleaning or unloading well
Reexamination Certificate
2000-05-04
2002-04-30
Bagnell, David (Department: 3672)
Wells
Processes
Cleaning or unloading well
C166S299000, C166S063000
Reexamination Certificate
active
06378611
ABSTRACT:
The invention relates to a procedure and a device for treating well perforations, in particular through wireline work.
BACKGROUND OF THE INVENTION
When a well is drilled, the final architecture of its completion usually depends strongly on its profile and the layering of the geological reservoirs encountered.
By “completion” we mean the final installation of the production tubing as well as all auxiliary equipment for bringing in a well.
The characteristics of the reservoirs such as pressure, bottom temperature, permeability, porosity, height of the area of interest, height of the stretch of water, type of compacted, deconsolidated or gritty sandy formation, expected well or injection yields, etc., make it possible to choose the “layer/hole” link system that is best suited to the various reservoirs identified and selected as the possible water, oil or gas producer or injector.
Problems may occur when exploiting a well. For the most part, these problems are the following:
an area starts experiencing an abnormal production of water,
an area starts to cave in and produce sand,
the pressure of an area decreases to the point where its production ceases,
the percentage of gas produced by an oil area increases abnormally
As soon as one of these problems becomes apparent, it is important to react quickly in order to avoid any harmful effects and prevent the situation from worsening which could result in considerable production losses and therefore a loss of profitability.
Until now, several techniques were used to resolve the issues tied to these problems.
FIG. 1
represents a situation commonly called “Selective completion”. In a drilled hole
1
surrounded by a casing
2
and waterproof cement
3
, and in which is located a production tubing
4
equipped with bringing in sliding sleeves
6
and
7
, packers
5
,
8
and
10
are arranged so as to isolate the areas of perforation Z
4
, Z
5
and Z
6
to be treated. Stopping or consolidating the perforations then requires the use of a complex drilling device as the traction capacity of the latter must be sufficient to remove the existing completion and reinstall a new one after the stopping or consolidation.
These operations also require that the annular spaces between the production casing and the production tubing be filled with fluids that are designed to counterbalance the pressures of the various reservoirs. We then risk damaging certain areas that are sensitive to these fluids, for example clayey areas that may intumesce.
The operations that must be carried out under the lower packer
10
can be performed using a technique known to the man of the art under the name “Coil tubing” or that known under the name “Snubbing”. Unfortunately, these techniques have the disadvantage of requiring that an area be abandoned by injection of polymer resins when the temperature of the area is compatible with the chemical formulation of the resin, or the cement. Thus, any perforated area that still has potential for production is lost when is it located under a resin or cement plug.
FIG. 2
represents a situation commonly called “Multiarea completion” where the areas to isolate or consolidate are located under the production packer
11
. In this case, it is possible to use “Snubbing” or “Coil rubbing” or to function using an electrical line wireline work unit with isolation by inflatable packet
12
. Access to all perforated areas is possible, however, we still lose areas Z
7
, Z
8
located under the inflatable packer
12
.
FIG. 3
represents a situation commonly called “Monobore completion” where the production tubing is none other than the casing. In this case, all perforated areas are accessible from one same diameter and therefore it is much easier to isolate a perforated area by injecting cement or anchoring a liner using the wire line work unit than it is in the previous cases. One may also use a liner
13
of the “Patch” type which can be found on the market and has a fine malleable envelope. Unfortunately, these patches can only efficiently guarantee the isolation of an area when the pressure of the reservoir is less than the pressure that prevails in the production tubing, because of a flattening effect. As this situation is quite infrequent, we use patches with envelopes that are hard and thicker in order to be able to guarantee a bidirectional waterproof quality. The disadvantage of these patches comes from the fact that their removal often creates a problem and therefore it is no longer possible to place another patch at a lower level.
These isolation or consolidation techniques of a perforation area are very delicate as there is a high risk of damaging certain perforation intervals that have great potential. Furthermore, they require stopping the production for long periods of time, often 8 to 15 days, which creates a significant shortfall that needs to be made up.
Therefore it would be interesting to have a system that makes it possible to intervene, preferably by wire line, in a production tubing, even of small diameter, while only requiring that the production be interrupted for a short period of time.
In addition, such a system should be able to be used in all cases represented in the figures.
SUMMARY OF THE INVENTION
The applicant has been able to develop a procedure and a device that make it possible to treat the perforations of a well, in order to plug or isolate them, which resolves the problems and corrects the weaknesses that have just been mentioned.
The procedure as set forth in the invention consists mainly of the following successive steps:
(a) a dehydration powder chamber that produces a large volume of high pressure gas at a high temperature and a composite powder chamber designed to treat the perforation are arranged close to the perforation to be treated;
(b) the dehydration powder is set on fire;
(c) once the combustion of the dehydration powder is over, the composite powder is set on fire so the treatment of the perforation may take place.
The device as set forth in the invention consists essentially of:
means of locating and positioning the device inside the well;
a first chamber designed to contain dehydration powder and capable of freeing the gases produced during the combustion of the dehydration powder located close to the perforation to be treated;
a second chamber designed to contain composite powder and capable of freeing the gases and other components produced during the combustion of the composite powder at a point located close to the perforation to be treated;
means of igniting the powder contained in the first chamber;
means of igniting the powder contained in the second chamber once the combustion in the first chamber is over.
Thus, according to a first method of execution of the invention, the composite powder consists at least of propulsive combustible powder and an alloy designed to plug the perforation.
According to a second method of execution of the invention, the composite powder contains propulsive combustible powder and consolidation beads, so as to consolidate the perforation.
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Bagnell David
Dougherty Jennifer R.
Sughrue & Mion, PLLC
Total Fina S.A.
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