Patent Application
20150267501
1. Field of the Invention
The present invention relates to the intentional inducement of downhole formation damage in a target zone to produce deep plugging of the formation matrix and sealing the zone at the wellbore face.
2. Description of the Related Art
Prediction of formation plugging damage that occurs while drilling wells is an important factor in optimizing an oil field's development. The economic impact of near-wellbore drilling-induced damage and cleanup efficiency has led to significant progress in both experimental and numerical studies in order to assess wellbore flow properties during oil production.
The possibility of causing formation permeability plugging damage exists during operations throughout the life of the well. Wellbore damage can cause a reduction in the natural capability of a reservoir to produce its fluids, such as a decrease in porosity or permeability, or both. Damage can occur near the wellbore face which can be relatively easy to repair or deep into the rock which may be difficult to repair.
Damage can occur when sensitive formations are exposed to drilling fluids. Formation plugging damage in a wellbore is generally caused by several mechanisms which can include the following:
In well completions, there are several recognized damage mechanisms, such as the invasion of incompatible fluids swelling the formation clays, or fine solids from dirty fluids plugging the formation matrix. Because damage can significantly affect the productivity of any well, adequate precautions should be taken to avoid such damage during all phases in the life of a well.
Natural or induced impairment to production can develop in the reservoir, in the near-wellbore area or the perforations. Natural damage occurs as produced reservoir fluids move through the reservoir, while induced damage is the result of external operations and fluids in the well, such as drilling, well completion, workover operations or stimulation treatments. Some induced damage triggers natural damage mechanisms. Natural damage includes phenomena such as fines migration, clay swelling, scale formation, organic deposition, including paraffins or asphaltenes, and mixed organic and inorganic deposition. Induced damage includes plugging caused by foreign particles in the injected fluid, wettability changes, emulsions, precipitates or sludges caused by acid reactions, bacterial activity and water blocks. Wellbore cleanup or matrix stimulation treatments are two different operations that can remove natural or induced damage. Selecting the proper operation depends on the location and nature of the damage.
The current practice to shut off a water zone requires a rig to case and cement the entire open-hole and to selectively perforate the oil zone while isolating and maintaining the water zone behind the casing and cement.
In general, formation plugging is considered to be an undesirable phenomenon. The problem to be addressed by the invention is how to utilize these phenomena to plug the porosity and to kill the permeability of a water zone and to retain the oil productive zone in an open hole to allow flow to the wellbore.
The present invention provides a method and apparatus to shut off an undesirable water zone in an open hole well by intentionally inducing formation plugging damage in the zone. By this method, the benefits associated with producing the oil zone from an open-hole rather than from perforations in cemented casing is maintained. The method and apparatus of the invention employs coiled tubing to deploy the components down hole and thereby avoids the need for a costly rig and other of the requirements of the prior art methods to shut off the water zone.
Thus, the present invention provides a rigless method for sealing off undesirable target zones in an existing open-hole well. An inflatable chemical balloon system that is deployed by coiled tubing is used to induce permanent skin damage to the surface and the adjoining region of the undesirable water zone. In one embodiment of the invention, a specially configured and dimensioned multi-section balloon is used to inject a formation plugging fluid during inflation; following full inflation, the body of the balloon is softened and melted, and retained against the wall of the well in the target zone.
An inflating container assembly is filled with a formation plugging fluid and includes at least one, but preferably a plurality of pressure-operated inflating valves and is surrounded by an inflatable balloon. The inflating valve or valves when open provide fluid communication between the interior of the inflating container and the balloon.
A sealed chemical container is secured above the inflating container and fluid communication between the containers is provided by a normally closed one-way pressure activated valve. The chemical container is provided with a chemical reactant and the inflating container is filled with a formation plugging fluid at the surface, and both are sealed before being deployed downhole. A circulation valve with a programmable timer provides fluid communication between the coiled tubing and the chemical container.
The two containers and the balloon are lowered to the target zone by the coiled tubing, thereby avoiding the need for a rig. Upon introduction of the pressurized fluid chemical reactant into the chemical container through the one-way pressure valve, there is initiated a controlled explosive exothermic chemical reaction above the inflating container. At a preset pressure, the valve to the inflating container opens to pass the exothermic reaction products and displaces the plugging fluid into the central balloon which, first inflates and simultaneously discharges the formation plugging fluid into the annulus of the target zone between the exterior surface of the balloon and the wall of the wellbore. The expansion of the central balloon also forces the formation fluid and the plugging fluid from the annulus into the formation, thereby intentionally inducing formation damage to eliminate or reduce the flow of formation fluids, e.g., water. The heat of the exothermic reaction as conveyed by the hot reaction products, then softens and/or melts the body of the balloon against the wall of the well to provide a permanent barrier or thermoplastic skin to seal off the undesirable zone.
The balloon's materials of construction are similar to the construction of an inflatable packer and can include fabric or wire reinforced rubber or other polymeric materials. As such, the production of the balloon is within the skill of the art. The balloon can be fabricated in accordance with known methods for producing an expandable polymeric product, e.g., as by molding which can also include a vulcanization step as in the production of rubber articles such as, e.g., inflatable well packers, bicycle inner tubes, and the like. The balloon can be provided in a generally cylindrical configuration having an axial opening with an internal diameter to permit the molded element to be slipped over the inflating container to which it is secured, e.g., by an appropriate adhesive that will provide a fluid-tight seal around the top, bottom and interior surfaces which divide the three-section balloon into separately inflatable chambers.
The central balloon can advantageously include one or more of the following structural elements:
The ratchet ring has overlapping teeth in the internal opposed facing sides of the overlapped surfaces which permit unidirectional expansion. The teeth are uniform, but asymmetric, with each tooth having a moderate slope on one side and a much steeper slope on the other side. The moderate slope allows the overlapped part to slide during expansion of the ring, and the steeper slope prevents the ring from collapsing after expansion. As noted above, the ratchet ring is contained inside a flexible, extendable tube with an opening, whereby two ends face each other when the tube is relaxed. The flexible circular tube keeps the teeth of the ratchet ring aligned, and the opening of the tube allows expansion of the ring inside of it.
In an alternative embodiment, the central balloon can be strengthened by an expandable wire stent similar to those used in medical applications for coronary stenting. The stent is embedded in the wall of the balloon between a pair of extendable polymer webs so that as the balloon is inflated by formation plugging fluid and chemical reaction products the stent can expand to thereby reinforce and support the balloon against the wall of the wellbore and maintain an effective seal.
In order to facilitate the separation of the portions of the central balloon secured to the inflating container from the outer wall of the central section following the full expansion and melting of the portion that is in contact with the wall of the wellbore, the originally molded balloon can be produced with weakened circumferential top and bottom sections that will soften and provide a highly elastic margin between the portion that is sealed and retained against the wellbore wall and the remaining margins that remains attached by adhesive to the inflating container.
Similarly, the upper and lower sections of the balloon which initially inflate to provide a seal with the wellbore wall and provide barriers to the flow of the formation plugging fluid from the central balloon can also be provided with one or more weakened areas that will result in their rupture under the force of a predetermined pressure that is subsequently delivered from the surface via the coiled tubing. The weakened areas can be produced by reducing the thickness of the polymer wall. Alternatively, the entire upper and lower balloons can be fabricated from a different polymeric composition having properties that will permit its more rapid expansion and eventual rupturing under the downhole conditions of pressure and temperature.
The polymeric formulation(s) for the respective sections of the balloon are chosen to produce the desired characteristics under the initial already elevated downhole temperature at the target zone, which is predetermined by conventional well logging techniques. The formulation also takes into account the increase in temperature of the already heated balloon produced by the exothermic chemical reactants which eventually come into contact with the interior surface of the zone sealing portion of the balloon to raise its temperature to the softening/melting point while it is fully expanded against the wall of the wellbore.
The chemical balloons have the capability of being inflated to contact the wall of the wellbore with the assistance of the expansive force created by the exothermic chemical reaction. After reaching the wall, the central balloon responds to the heat of the reaction products to soften and preferably melt against the wall of the well and create permanent skin damage, i.e., the sealing of the surface of the target zone. The selection and adaptation of existing chemical reactants to effect the method of the present invention is within the skill of the art;
The central balloon can be fitted or integrally formed with a single weakened diaphragm or a number of weakened areas spaced apart over its surface that will rupture at the start of inflation and permit the passage of the pressurized formation plugging fluid that is inside the inflating container, while also allowing the balloon to fully inflate and reach the wall of the wellbore. Alternatively, one or more pressure-activated one-way valves can be provided in the wall of the central balloon to pass the pressurized plugging fluid. The upper and lower balloons are configured to inflate faster than the central balloon to provide a fluid-tight annular compartment against the wall of the well. The central balloon inflates at a slower rate than the adjacent balloon because in an embodiment, the central balloon has one or more valves or a number of weakened areas which are ruptured at the start of inflation to form openings to allow the passage of the formation plugging fluid as the central balloon is inflating. After inflating the central balloon and forcing the formation plugging fluid and any residual wellbore fluid into the formation, the reaction products and the pressure of the explosive force will soften and melt the central balloon causing it to adhere to the wall of the well.
A circulation valve with a timer is attached in fluid communication to the end of the coiled tubing. The downhole end of circulation valve is attached via a pressure-operated inlet valve to the chemical container. The timed circulation valve is used to circulate wellbore fluid to the surface via the coiled tubing while the balloon assembly is lowered through the production tubing. When the apparatus is in position at the target zone, the fluid reactant is pumped down to the circulation valve and any wellbore fluid is displaced through the open circulation valve. At a predetermined time, the circulation valve is closed when it is calculated that the fluid reactant reaches the depth of the circulation valve. The pressure in the coiled tubing is increased, and the fluid reactant passes through the one-way pressure-operated valve into the chemical container. A closed automated system is thus provided to inflate the balloons. Adaptations of commercial timed circulation valve systems which are suitable for use in the method of the present invention are within the skill of the art.
The chemical container is placed below the circulation valve and contains the chemicals required for the exothermic reaction that provides the heat and controlled explosive force. The chemical container is fitted with a pressure-operated inlet valve located at the top of the container in fluid communication with the tubing. The valve opens at a predetermined pressure applied from the surface to initiate the exothermic reaction inside the container after entry of the fluid reactant via the coiled tubing.
A pressure-operated exit valve at the bottom of the chemical container allows the pressurized reaction products to enter the inflating container. A chemical reactant, e.g., sodium metal particles or other suitable reactive material, is placed in the chemical container at the surface and sealed.
The pressure-operated inflating valves open to inflate the three balloons. Alternatively, the pressure-operated inflating valves can be replaced with RFID valves which operate by radio frequency and pumped tags, such as Omega valves. However, pressure-operated inflating valves as described herein are preferred.
The circulation valve timer is set to account for the time required to pump the liquid chemical from the surface to the circulation valve depth. When the fluid reactant reaches the circulation valve depth, the circulation valve closes and the system is pressurized from the surface to open the pressure-operated valve to the chemical container and initiate the reaction. The rapid exothermic reaction increases the pressure in the chemical container to open the valve and allow the reaction products to enter the inflating container and begin displacing the formation plugging fluid from the inflating container.
As noted, the formation plugging fluid is initially contained in the inflating container and is displaced by the highly pressurized, hot reaction products coming from the chemical container above it. As it is displaced, the wall plugging fluid inflates the balloons and fills the upper and lower balloons completely until they expand to positions in contact with the wall of the wellbore. The displaced formation plugging fluid will inflate the upper and the lower balloons faster than the central balloon because the central balloon has an opening in the diaphragm causing it to rupture. The central balloon has at least one valve for discharging fluids, but preferably a plurality of weakened areas that rupture during the expansion of the central balloon, through which the displaced plugging fluid passes into the annulus. The valve(s) or openings in the body of the central balloon allow the passage of a controlled amount of the formation plugging fluid from the inflating container to the outside of the balloon, while at the same time, containing to inflate the balloon, but at a slower rate than the upper and lower balloons.
The central balloon is in contact with the wall of the wellbore after its maximum inflation. As the balloon expands, it pushes the original wellbore fluid and the formation plugging fluid that was inside the inflating container deep into the formation. In this step, the body of the balloon in contact with the hot reaction products resulting from the exothermic reaction initiated in the chemical container. The heat softens and preferably melts the central balloon and forces it against the wall of the well where the balloon is maintained by the expanded ratchet ring. The upper and lower balloons maintain a sealed annular chamber at the target zone. They are not affected by the exothermic reaction products because they are inflated by the formation plugging fluid and there are no openings in them permitting the plugging fluid to escape.
After the target zone has been sealed, additional pressurized fluid is pumped into the coiled tubing from the surface to the upper and lower balloons via the containers and intermediate valves until they rupture to thereby enable the apparatus to be retrieved via the coiled tubing through the production tubing.
In an alternative embodiment of the system and method of the invention, the upper and lower balloons that isolate the target zone when inflated are replaced by a dual inflatable packer system. Each of the packers can be inflated with wellbore fluids by separate electric pumps. The upper inflatable packer and its associated electric pump are positioned above the circulation valve, while the lower inflatable packer and its associated electric pump are positioned below the inflating container. The inflatable section is constructed of a reinforced rubber composition for durability during repeated usage of the assembly. Electrical wiring extends to the wellhead where controls for the pumps are provided. Inflatable packers are well known in the art and can be adapted by one of ordinary skill for use in the invention.
A suitable inflatable packer system is commercially available from Schlumberger under the designation Dual-Packer Module (MRPA) which can be inflated using that company's Pumpout Module (MRPO). This model includes an autoretract mechanism which applies a longitudinal tensile force to assist in retracting the packers after deflation, thereby minimizing drag when the assembly is withdrawn. It is reported in the Schlumberger commercial literature for this system that at temperatures below 107° C./225° F., the inflatable elements retain sufficient elasticity for operation without the retractor mechanism.
As in the embodiment utilizing the upper and lower balloons, the upper and lower inflatable packers are inflated prior to inflation of the central balloon in order to isolate the target zone. The central balloon is inflated in the same manner as the above-described embodiments. Following the full expansion and melting of the central balloon to seal the wall in the target zone, the upper and lower packers are deflated using the electrical pumps and the apparatus is removed from the wellbore via the production tube. In this embodiment, the central balloon can include one or more of the structural elements discussed above such as the straps or bands of rigid high tensile material, the expandable ratchet ring, and the expandable metal stent.
A used in this description and in the claims, the term “balloon” refers to an inflatable member that is positioned at, or adjacent to the target zone that is to be treated prior to being inflated and includes an inflatable packer that can be inflated with wellbore fluids using an associated electric pump. The balloon is preferably mounted coaxially with the longitudinal axis of the coiled tubing and symmetrical in its transverse cross-section. The balloon is preferably dimensioned and configured to expand uniformly to securely engage the surrounding wall of the wellbore once the balloon is fully inflated and thereby center and stabilize the assembly of which it is an integral member so that it resists movement by longitudinal forces.
Preferred embodiments of the invention are described in more detail below and with reference to the drawings in which:
Referring now to the drawings, and specifically to
The un-inflated balloon 12 and related components described below are deployed in the wellbore 11 by coiled tubing 14 which passes through production tube 30 until it reaches target zone 16 of the wellbore. For purposes of describing this embodiment, target zone 16 will be denoted as an “undesirable” water zone. In
The undesirable zone 16 may also represent a lateral drill hole which may be horizontal or angled, and which may have been partially damaged by one or more of a number of factors, including, but not limited to, contact with wellbore fluids used during drilling/completion and workover operations. It is a zone of reduced permeability within the vicinity of the wellbore 11 (i.e., skin), often the result of foreign fluid invasion into the reservoir rock.
The three balloons 12a, 12b and 12c can be made of any suitable flexible thermoplastic expandable material, i.e., a polymer, and preferably rubber, natural or synthetic. Different flexible and resilient materials can be used for each of the three balloons and/or the individual balloons can be produced with different wall thicknesses, physical properties and means for attachment to their supporting surface. The thickness and resiliency of the walls, or sections of the walls of the respective balloons is sufficient to permit the expansion and secure contact with the adjacent wall surface.
As will be described in greater detail below, the balloons 12 are inflated via an exothermic reaction in the chemical container 34 which is initiated by the pumping of a predetermined volume of a fluid reactant 33 (not shown) from the surface via the coiled tubing 14 and through the upper pressure-operated inlet valve 36 into the chemical container 34 and into contact with one or more reactant material(s) loaded in the chemical container 34 during preparation of the apparatus before it is lowered into the wellbore 11. The inflating container 24 is also filled at the surface with formation plugging fluid 25 and has at least three inflating ports. In the preferred embodiment, the three balloons are secured in position on the outside surface of the inflating container 24, e.g., by an adhesive. The central balloon preferably has a plurality of weakened areas that will rupture at the early stages of inflation. After rupturing, the weakened wall will allow the passage of the formation plugging fluid from the inflating container 24 while allowing the balloon 12 to inflate and expand radially into the annular space or compartment defined by the adjacent balloons.
The upper and lower balloons 12b and 12c will inflate first to provide tight seals against the wall of the well at either end of the central balloon, thereby acting as barriers to the plugging fluid 25. This fluid-tight compartment will permit the formation plugging fluid 25 to be forced deep into the formation under the pressure produced by the hot rapidly expanding reaction product. As noted, initially, the wellbore 11 is filled with formation fluids or other completion fluids which are referred to herein as “wellbore fluid.”
Referring now to
Referring again to
The chemical container 34 can contain any suitable chemical reactant(s) 38 that can be activated to produce an exothermic reaction and preferably provide a limited or controlled “explosive” expansion by the addition of a fluid reactant as an activating medium. In the present example, the chemical container 34 preferably houses a supply of pure solid reactant material, such as sodium metal 38, which can later be activated by an appropriate amount of water delivered via the coiled tubing from the surface under pressure to initiate the necessary reaction with sufficient force to rapidly expand the rubber balloons 12. For safe handling, the sodium metal can be submerged in kerosene or other non-reactive liquid in the sealed chemical container 34. Other appropriate known reactant materials are contemplated as within the scope of the invention, provided that they are capable of producing a rapid exothermic reaction.
Once the balloon 12 reaches the target zone 16, a predetermined volume of activating fluid reactant 33 that is required to complete the highly exothermic reaction with the chemical(s) inside the chemical container 34 is pumped into the coiled tubing 14 from the surface. The fluid reactant is followed by a displacing liquid (not shown) which is pumped into the coiled tubing 14 to displace wellbore fluids 31 through the timed circulation valve 32 as is illustrated in
Referring again to
Pressure-operated exit valve 40 is positioned at the bottom of the chemical container 34 and communicates with the inflating container 24. The pressure-operated exit valve is set to open under the pressure generated by the chemical reaction and permit the hot pressurized reaction products to enter the inflating container 24.
Upon entry of the reaction products into inflating container 24, the three pressure-operated inflating valves 26, 27, and 28 open to permit the formation plugging liquid 25 to exit the inflating container and begin inflating the three sections of the balloon 12 according to the predetermined sequence described above. The central balloon 12a inflates at a lower rate because of its relatively greater volume, while the adjacent smaller balloons 12b and 12c will be fully inflated first and provide the required seals with the wellbore wall to isolate the target zone 16. This filling sequence can also be achieved by varying the size or flow rate of the plugging fluid through the valves to the respective balloons 12b and 12c, and/or by lowering the pressure setting at which the valves 26 and 27 open. With reference to
The functioning of the weakened sections 47 in the central balloon 12a is illustrated in
Again referring to
It should be noted that alternative valve arrangements, such as pre-programmed RFID tags operated by radio frequency and pumped tags provided from the surface with prior art electronically actuated valves such as Omega valves, can also be incorporated into the present invention by one of ordinary skill in the art. However, the pressure-operated valves as described above, are presently preferred. The pressure operated valve is a conventional injection-pressure-operated valve such as those manufactured by Schlumberger and Halliburton.
As noted above, the openings 47 in the sidewall of the body of the central balloon 12a will allow the passage of the pressurized formation plugging fluid from the inflating container 24 into the annulus between expanding balloon 12a and the wellbore wall, while also causing the balloon to inflate at a slower rate than the upper and lower balloons, 12b and 12c.
The formation plugging fluid 25 is initially in the inflating container 24. As shown in
As shown in
With reference to
Referring to the stage illustrated in
At this stage of the process, the body of the central balloon 12a is fully exposed to the heat generated in the exothermic chemical reaction from chemical container 34 directly above it.
As noted, the heat of the reaction product melts the central balloon 12a against the wall of the well, and at the same time, it will be retained in position by the expandable ratchet rings 44 and supported longitudinally by the rigid bands or straps 42.
The upper and lower balloons 12b, 12c are not affected by the exothermic reaction because they are initially fully inflated by the formation plugging fluid and there is no aperture in either of these annulus-sealing balloons through which the plugging fluid can escape.
Again referring to
After the parting of the central balloon 120a and the bursting of the upper and lower balloons 120b, 120c, the coiled tubing can be withdrawn from the wellbore 11 with the remnants of the central, upper and lower balloons 120b, 120c, leaving the principal portion of central balloon 120a in position to seal the undesirable water zone of the wellbore 11.
Referring to
For circumferential strength, an expandable ratchet ring 44 is positioned within opened-ended tube 45 which is embedded in, or bonded to the interior surface of the circumference of the central balloon 12c. It is preferable to position ratchet right ring at either end of the central balloon to hold it firmly in position when expanded against the wall above and below the target zone. One or more additional transverse ratchet rings can be provided based on the longitudinal length of the target zone that must be covered by central balloon 12c.
The expandable ratchet ring 44 is comprised of two metal rings 44a, 44b, having overlapping teeth on the inner facing sides as best shown in
Referring to
As shown in the enlarged cross-sectional video of
With reference to
Referring to
With reference to
With reference to
After the target zone 16 has been sealed, the upper and lower inflatable packers 80a, 80b are deflated by the electric pumps 82a, 82b, which withdraw the wellbore fluid 31 from their respective packers and return it to the wellbore. Once the upper and lower packers 80a, 80b are sufficiently deflated, the apparatus is removed from the wellbore through the production tubing 30 via the coiled tubing 14.
The sequence of process steps can be summarized in conjunction with reference the drawings as follows:
Additional displacing fluid is pumped into the coiled tubing 14 from the surface in order to increase the pressure to a sufficient level to open the pre-set pressure-operated upper inlet valve 36. As shown in
As shown in
In
The method and system of the present invention have been described above and in the attached drawings; however, modifications derived from this description will be apparent to those of ordinary skill in the art and the scope of protection for the invention is to be determined by the claims that follow.
| Number | Date | Country | |
|---|---|---|---|
| 61968169 | Mar 2014 | US |
