Patent Application
20190242241
The invention relates generally to systems and methods for creating lateral tunnels within and stimulating subterranean formations surrounding wellbores.
Acid tunneling is a method of forming tunnels within a subterranean formation using acid injection. Tools which are used currently for acid tunneling typically have a bottom hole assembly which features a wand having an acid-injection nozzle. The wand is connected to a base portion by a pair of flexible joints. These tools use increased fluid pressure pumped from surface to flex the joints of the tool, thereby changing the angle of the wand of the tool and influence the direction of the tunnel being created by acid injection. The tunnels which are created often undesirably curve or arc in an upward fashion through the formation due to the upward movement and force of the wand from to pressure increases which cause joint flexure during tunneling. Oftentimes, indexing tools are used to rotate the acid tunneling bottom hole assembly to try to help orient the acid-injection nozzle angularly within the wellbore prior to flexing the tool joints. As acid is injected, a tunnel is formed in the formation which extends radially away from the main wellbore.
The inventors have recognized that with many conventional acid tunneling tool designs, it can be difficult or impossible to positively control the direction of tunnel development. The wand can become oriented in a number of different directions given the variability of angular bending and the dependence of flexure on fluid pressure from the surface. Improper orientation of the wand at the beginning stage of tunnel creation can result in the tunnel being developed in a different direction than is desired. Indeed, the inventors believe that with most conventional acid injection tool, the direction of tunnel development is substantially random. Also, small changes in the directions of flexure or variations in formation material could undesirably create a crooked tunnel which could potentially cause the acid tunneling tool could become stuck in rock and difficult to remove from the wellbore. Further, the inventors have recognized that, currently, there is no practical way to verify the direction and angle of bend for the wand during operation.
The invention provides acid tunneling systems and methods for acid tunneling having positive direction control, or steering, for the development of tunnels. A steerable acid tunneling system is described which includes a running string with an affixed acid tunneling bottom hole assembly. The acid tunneling bottom hole assembly preferably includes an acid injection tool having a wand which is connected to a base portion with a single flexible joint. In an alternative embodiment, the acid injection tool does not have a flexible joint. One or more nozzles are located within the distal end of the wand to inject acid in an axial direction. The acid tunneling bottom hole assembly also preferably incorporates a data sub which is operably associated with one or more sensors. In preferred embodiments, there are one or more sensors which can measure or detect the orientation of the wand, including angular deviation and azimuth. Tube-wire or another power and data conduit is preferably included within the running string to transmit detected information to a controller at the surface. Other telemetry means, such as optical fiber, could also be used. Information obtained by the sensors is preferably used to control operational aspects of the acid injection tool. The information is preferably also used to map tunnels as tunnels are being formed by creating three-dimensional representations of the tunnels within the formation. This feature provided real-time monitoring capability for the direction of tunnel development and potentially for the mapping of tunnels.
In certain embodiments, a caliper is incorporated within the bottom hole assembly to measure tunnel diameter and/or topology of tunnels. This allows the diameter and/or topology of tunnels being formed to be measured in real-time. An operator can then make corrective adjustments to the tunneling process, if needed, such as by increasing the diameter of portions of a tunnel being formed. Alternatively, a caliper may be run into the wellbore after tunneling has been created in order to measure the diameter of portions of a completed tunnel. The inventors have found that use of a caliper is beneficial in that it allows an operator to optimize acid concentration to create a smaller diameter tunnel and not waste acid flowing away from the tunnel face.
In an exemplary method of operation, a whipstock is first run into and secured within the wellbore. The whipstock is oriented in direction of desired tunnel formation. Thereafter, a steerable acid tunneling system is run into the wellbore. The wand of the acid tunneling tool is angularly (i.e., azimuth) oriented within the wellbore by the landing surface of the whipstock. Additionally, the slope of the whipstock landing surface will also dictate the initial orientation of the wand of the acid tunneling tool. Injection of acid will then develop a tunnel in a predetermined direction, as dictated by the whipstock.
In certain embodiments, a pulsating tool is incorporated into the bottom hole assembly. The pulsating tool can help create larger tunnels and increase acid reaction efficiency.
For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein:
An acid tunneling bottom hole assembly 36 is affixed to the distal end of the running string 32. The acid tunneling bottom hole assembly 36 includes an acid tunneling tool 38 which is used to flow acid which is pumped from surface 14 into the formation 16. The acid tunneling tool 38 includes a cylindrical base portion 40 and an acid injection wand 42. An articulable joint 44 connects the base portion 40 and the injection wand 42. Each of the first and second articulable joints 38, 40 allows the connected members to be moved angularly with respect to one another. The articulable joint 44 may be constructed and operate in the same manner as those used in the StimTunnel™ acid placement tool which is available commercially from Baker Hughes, a GE company, LLC of Houston, Tex. Preferably, the acid injection wand 42 is provided with end nozzles 46 for injection of acid into portions of the formation 16 surrounding the wellbore 10. This configuration is preferred for acid tunneling because the acid flow through the end nozzles 46 will be directed generally in the direction of intended tunnel creation (i.e., the direction toward which the acid injection wand 42 is pointing.
The acid tunneling bottom hole assembly 36 also preferably includes a caliper 48 which is capable of measuring or detecting the diameter or shape or size of a borehole surrounding the bottom hole assembly 36. The caliper 48 includes at least one finger 50 which protrudes radially outwardly from the caliper body 52 to make contact with the surrounding wall. Preferably, the caliper 48 is an imaging caliper which can provide a real-time, detailed visual representation of the shape and topology features of a surrounding surface. A suitable caliper device for use in this application is the Baker Hughes Imaging Caliper which is available commercially from Baker Hughes, a GE company, LLC of Houston, Tex. Information provided by the caliper 48 is useful to balance acid concentration versus tunnel creation. For instance, it is usually unknown whether acid injected from an acid tunneling tool is dissolving rock in front (i.e., distal end) of the tool, contributing to increased tunnel length, or is flowing toward the back (i.e., proximal end) of the tool, contributing to tunnel width (diameter) only. Information provided by the caliper 48 could be used to improve the acid pumping rate and coiled tubing tripping speed while creating tunnels. Incorporation of the caliper 48 into the acid tunneling bottom hole assembly 36 allows operators to obtain such tunnel data in real time and adjust the operational parameters (i.e., acid pumping rate and coiled tubing tripping speed) on the fly. Also, this tunnel data could be used to create a database which includes identification of the tunnel(s) being created, reservoir properties, acid strength, pumping rate(s), and tripping speed.
The acid tunneling bottom hole assembly 36 also preferably includes a data sub 54. The data sub 54 includes electronics storage or memory 56 to receive and store information received from sensor(s) 58. The one or more sensors 58 are preferably disposed upon the wand 42 of the acid tunneling tool 38 and are interconnected with the storage or memory 56 by a data conduit 60. The one or more sensors 58 will preferably include an inclinometer which will detect or measure the inclination of the wand 42 (with respect to vertical) within the wellbore 10. In addition, the one or more sensors 58 also preferably include a compass or azimuth measurement device which will identify the angular orientation of the wand 42 with respect to azimuthal directions (N, E, S, etc.).
A data communications conduit 62, such as tube-wire, is preferably used to transmit the received information to a surface-based controller and storage medium 64 from the data storage or memory 56. Telecoil® is a preferred arrangement for this application and is coiled tubing which incorporates tube-wire that can transmit power and data. Tube-wire is available commercially from manufacturers such as Canada Tech Corporation of Calgary, Canada. Conduit 62 is shown within the flowbore 34 of the running string 32 and is operably interconnected with the controller/storage medium 64 at surface 14 as well as the caliper 48 and data storage 56 within the acid tunneling bottom hole assembly 30.
The controller/storage medium 64 may be programmable, and preferably includes suitable programming to use mathematical modeling to determine the location and orientation of the wand 42 within the wellbore 10. Suitable programming for this application includes CIRCA™ RT modeling software for coiled tubing applications. CIRCA™ Tools software may be used for geometric setup of tool angle, and CIRCA™ software may be used to model forces and pressures in coiled tubing. Each of these software packages is available commercially from Baker Hughes, a GE company, LLC of Houston, Tex. When CIRCA™ RT is used for modeling, a current coiled tubing force analysis is extended to take into account the tri-dimensional tunnel length extension by considering the chemical reaction between acid and formation rock and the mechanical erosion due to the fluid jet from nozzle 46 within the tunnel 74. Information provided by sensor(s) 58 is thereby used to model or map the tunnel 74 and other tunnels by generating and displaying a representation of these tunnels within the formation 16.
It is currently preferred that articulable joints 66 be used between the acid tunneling tool 38, the caliper 48 and the data sub 54 components within the acid tunneling bottom hole assembly 30. The use of articulable joints 66 between some or all of these adjacent components will aid disposal of the bottom hole assembly 30 into tunnels that are created by acid tunneling. However, articulable joints are not necessary to operation of the acid tunneling bottom hole assembly 30 and, depending upon the angle of departure for the direction 72 of intended tunnel development, may be omitted.
During acid tunneling, acid is flowed from an acid supply 68 at surface 14 by pump 70 through the flow bore 22 of the running string 20 to the bottom hole assembly 26. The pump 70 is preferably a variable speed or variable capacity pump.
In the depicted embodiment, the acid tunneling bottom hole assembly 30 includes a pulsating tool 76 which is shown located between the caliper 48 and the data sub 54. A suitable pulsating tool for use in this application is an EasyReach Extended Reach Tool which is available commercially from Baker Hughes, a GE company, LLC of Houston, Tex. The pulsating tool 76 uses water hammer effect to create pressure waves within acid that is pumped down to the acid tunneling tool 38 from surface 14.
Preferred methods of operation, are illustrated in
To begin tunneling, acid is then flowed by the pump 70 from the acid supply 68 to the acid tunneling tool 38 in order to exit the end nozzle 42, as illustrated in
In order to form the lateral tunnel 74, at least some portion of the process of forming tunnel 74 within the formation 16 is preferably controlled based upon information sensed by the sensor(s) 58 relating to the angular and azimuthal orientation of the wand 42. Data sent to the controller 64 at surface 14 is used to control the acid tunneling tool 38. For example, acid flow to the acid tunneling tool 38 may be increased by the pump 70 and/or actuation of the pulsating tool 76 to increase tunnel length. Alternatively, if the caliper 48 detects that the diameter of the tunnel 74 being created is too small, then the nature of the acid being used or its flow rate or the location of the wand 42 within the tunnel 74 may be altered to cause the tunnel 74 diameter to be increased.
One method of increasing diameter of the tunnel 74 is to increase the acid concentration while continuing to create new tunnel length (i.e., acid injection). Only so much acid is used to react against the formation 16 prior to being displaced back toward the wellbore 10. An operator could then displace formation 16 material at the same pump rate but with a higher acid concentration leaving more acid available to react on the smaller tunnel 74 and increasing its diameter.
An alternative method of increasing tunnel diameter is illustrated in
In order to optimize tunneling processes, most if not all, injected acid should be used to extend the tunnel length. If too much acid is pumped too fast, some of it will not have time to react with the formation 16 rock at the distal tunnel end 80 and it will flow back towards the main wellbore 10. There it could uncontrollably enlarge the tunnel and/or create wormholes without knowing how much acid is used to extend the tunnel lengths and how much acid is increasing tunnel diameter. Tunnel length can be optimized by determining and pumping an amount of acid that is sufficient to extend tunnel length without wasting excess acid which would diametrically enlarge the tunnel 74. By using real-time telemetry, software modeling and a caliper 48, the pumped acid volume can be optimized to reduce job cost and logistics.
Directional control and steering for the acid tunneling bottom hole assembly 30 are primarily achieved by virtue of the whipstock 18 and its angled landing surface 22. Once the acid tunneling bottom hole assembly 30, and primarily the wand 42, become oriented in the desired tunneling direction 72, acid injection will continue to develop the tunnel 74 in that desired direction 72. The procedure of simultaneously jetting acid (via nozzle 46) and pushing force upon the bottom hole assembly 30 in the desired direction 72 extends the length of the lateral tunnel 74 in the desired direction 72. In contrast to tunneling techniques which have formed curved or arched tunnels, tunnels created using the systems and methods of the present invention tend to be substantially linear or straight rather than curved.
The direction of tunnel creation and the dimensions of the tunnel being created can be monitored in real-time as the lateral tunnel 74 is developed. As a result, operators at surface 14 can develop three-dimensional maps or representations which include the shape, direction and topological features of lateral tunnel 74 and other tunnels which are developed using the systems and methods of the present invention.
It should be understood that the invention provides systems for conducting acid tunneling within a wellbore. An exemplary system includes a whipstock 18 having an angled landing surface 22, the whipstock 18 being secured within a wellbore 10. The system would also include a steerable acid tunneling arrangement 30 which has an acid tunneling tool 38 that is azimuthally oriented within the wellbore 10 by the whipstock landing surface 22. The acid tunneling tool 38 has a wand 42 which presents a nozzle 46 to inject acid in the desired tunneling direction 72, and the wand 42 is angularly oriented (with respect to vertical) by the landing surface 22 of the whipstock 18. Sensor(s) 58 are associated with the wand 42 to detect angular inclination and azimuthal direction of the wand 42 which is indicative of the direction of tunnel 74 development. The sensor(s) 58 provided a signal indicative of the sensed information to the controller 64 at surface 14. In particular embodiments, the acid tunneling tool 38 is included within an acid tunneling bottom hole assembly 30 which also includes a caliper 48 which is configured to measure the diameter and/or topology of the tunnel 74. Also in particular embodiments, the acid tunneling bottom hole assembly 30 includes pulsating tool 76. The pulsating tool 76 will temporarily and intermittently restrict flow of acid which is flowing toward the acid tunneling tool 38 to create pressure pulses which could minimize the acid volume further. For pressure peaks developed by the pulsating tool 76, the acid flow rate, and so that acid volume, can be reduced to obtain essentially the same pressures as with higher acid flow rates used without a pulsating tool. In preferred embodiments, tube wire is used to transmit detected information about tunnel direction and/or diameter and/or topology to a controller 64 at surface 14.
Additionally, the invention provides methods for acid tunneling wherein a whipstock 18 is first secured within a wellbore 10, the whipstock 18 presenting an angled landing surface 22. Thereafter, an acid tunneling arrangement 30 having an acid tunneling tool 38 is run into the wellbore 10. The acid tunneling tool 38 contacts the whipstock 18 and the landing surface 22 azimuthally orients the acid tunneling tool 38. The landing surface 22 of the whipstock 18 also angularly orients a wand 42 of the acid tunneling tool 38 with respect to vertical as the wand 42 is lowered further onto the landing surface 22. Acid is pumped through the acid tunneling tool 38 to inject acid in a desired tunneling direction and form a lateral tunnel 74. During tunneling, the angular inclination and azimuthal direction of the wand 42 is detected by one or more sensors 58. The detected information is transmitted to a controller 64, and the information is used to steer the acid tunneling tool 38 and/or create a map or representation of the tunnel 74. In some embodiments, the information is used to create a map or representation of the tunnel 74.
