Wells – Processes – Placing fluid into the formation
Reexamination Certificate
1998-12-23
2001-07-17
Bagnell, David (Department: 3673)
Wells
Processes
Placing fluid into the formation
C166S186000, C166S191000, C166S306000
Reexamination Certificate
active
06260622
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a tool and method for injecting treatment fluids, such as a sand consolidation agent or production stimulation chemical and an overflush fluid, into a formation surrounding an underground borehole.
It is known from U.S. Pat. No. 3,765,484 to treat an unconsolidated e.g. sandy subsurface earth formation surrounding an underground borehole by introducing a treatment fluid which comprises a consolidation agent into the pore spaces of the formation in the vicinity of the wellbore.
The tool known from this prior art reference is designed to inject a treatment fluid into the formation via perforations in a well casing. Other tools for injecting a treatment fluid into a formation via perforations in a well casing are disclosed in U.S. Pat. Nos. 3,487,877; 3,593,910 and 3,861,465.
The known tools generally comprise a pair of axially spaced packers which define an annular space via which the treatment fluid is injected into the surrounding perforations.
A limitation of the known tools is that they are designed to inject a batch of treatment fluid over a limited length interval via perforations into the formation. If parts of the formation surrounding perforations at different levels in a well are to be treated then the tool is moved to another level and the injection of a batch of treatment fluid is repeated once the tool has been positioned adjacent the perforations.
It is an object of the present invention to provide a tool and method which are able to inject treatments fluids, such as a sand consolidation agent, stimulation chemicals and/or overflush fluids over a long interval into a formation surrounding an underground borehole.
SUMMARY OF THE INVENTION
The tool according to the invention thereto comprises
a tool body which defines a longitudinal axis that extends in use in a longitudinal direction within an underground wellbore;
at least three axially spaced swab assemblies which are carried by the tool body such that in use at least two axially spaced annular spaces are formed between the tool body and the wellbore; and
at least two treatment fluid supply conduits which are each connectable in fluid communication with one of the annular spaces.
Preferably the fluid supply conduits comprise a pair of concentric coiled tubings and each fluid supply conduit is connectable to a pump which is adapted to pump fluid at a controlled flow rate via the supply conduit and associated annular space into the pore spaces of the earth formation surrounding the annular space.
The method in accordance with the invention of injecting fluids into a formation surrounding an underground borehole using the above-described tool comprises moving the tool in a longitudinal direction through the wellbore; and simultaneously pumping a first treatment fluid via one of the fluid supply conduits into the pore spaces of the formation surrounding one of the annular spaces whilst a second treatment fluid is pumped via another fluid supply conduit into the pore spaces of the formation surrounding another annular space.
Preferably, the tool is pulled or pushed through the borehole by the supply lines and a preflush fluid is injected into the pore spaces of the formation surrounding the wellbore in front of the tool via an annular space surrounding the supply lines.
It is also preferred that the first treatment fluid is injected via the foremost annular space surrounding the tool body which carries the swab assemblies and a second treatment fluid is injected via the rearmost annular space surrounding the tool body.
If in that case the fluid supply lines comprise a pair of concentric coiled tubings it is furthermore preferred that the first treatment fluid is injected into the foremost annular space via the outer coiled tubing and the second treatment fluid is injected into the rearmost annular space via the inner coiled tubing, which inner tubing extends through the center of the tool body such that it is in fluid communication with the rearmost annular space.
Furthermore it is preferred that the first and second treatment fluids are pumped into the annular spaces at controlled pump rates which are proportional to the speed at which the tool is moved through the wellbore.
The tool and method according to the present invention enable injection of treatment fluids over any length of an underground formation surrounding a wellbore in an accurate, simple and reliable manner.
The tool according to the invention allows continuous pumping of treatment fluids into the formation while the tool is moved along the target completion zone. The treatment fluids are pumped continuously via the annular spaces between the swab assemblies into the formation. At any one time only a limited zone is treated, resulting in improved placement. No wellbore cycling to new fluids is necessary because the annular spaces between the swab assemblies remain filled with one type of fluid thus further improving placement. As a result of more efficient placement treatment volumes can be reduced. The interval length which can be treated is increased at significantly reduced cost.
The tool and method according to the invention can be used for any matrix treatment of longer completion intervals in which more than one treatment fluid needs to be placed into the formation.
It is observed that U.S. Pat. No. 3,935,910 discloses a method for molding a protective sleeve and tubing onto the bore-hole wall during drilling. The known sleeve and tubing, however, form an impermeable internal lining of the wellbore which protect the borehole against caving in and no material is injected into the surrounding formation.
Furthermore, it is observed that Australian patent AU 548335 discloses a well sampling device which comprises a series of resilient packer elements between which two annular spaces can be created via which pore fluids can be sampled simultaneously from different levels in the well. The known device is, however, not moved through the well during the sampling activity. Finally it is observed that German gebrauchsmuster DE 8801702 U discloses a water purification well in which water is injected radially into an annular sandy layer surrounding the well via an upper annular space and subsequently sucked into the well via a lower annular space. Also this device is not moved through the well during the water purification process.
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W. B.Bleakley, Production Editor, “Where we stand on sand consolidation,”The Oil and Gas Journal, Mar. 13, 1967, pp. 87-93.
Blok Reinoud Hendrik Jurgen
Bossaerts Jan Dirk
Bagnell David
Lee Jong-Suk
Shell Oil Company
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