Patent Application
20130112436
Hydrocarbon fluids are obtained from subterranean geologic formations, referred to as reservoirs, by drilling wells that penetrate the hydrocarbon-bearing formations. In some applications, a well is drilled through multiple well zones and each of those well zones may be treated to facilitate hydrocarbon fluid productivity. For example, a multizone vertical well or horizontal well may be completed and stimulated at multiple injection points along the well completion to enable commercial productivity. The treatment of multiple zones can be achieved by sequentially setting bridge plugs through multiple well interventions. In other applications, drop balls are used to open sliding sleeves at sequential well zones with size-graduated drop balls designed to engage seats of progressively increasing diameter.
In general, the present disclosure provides a methodology and system for stimulating or otherwise treating multiple intervals/zones of a well by controlling flow of treatment fluid via a plurality of flow control devices. The flow control devices are provided with internal profiles and flow through passages. Hydraulic darts are designed for selective engagement with the internal profiles of specific flow control devices, and each dart may be moved downhole for engagement with and activation of a specific flow control device.
Certain embodiments will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate only the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:
In the following description, numerous details are set forth to provide an understanding of some illustrative embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.
The disclosure herein generally relates to a system and methodology which facilitate multi-zonal completion and treatment of a well. For example, the methodology may comprise completing multizone vertical wells and/or horizontal wells that benefit from stimulation at multiple injection points along the wellbore to achieve commercial productivity. The individual well zones can be subjected to a variety of well treatments to facilitate production of desired hydrocarbon fluids, such as oil and/or gas. The well treatments may comprise stimulation treatments, such as fracturing treatments, performed at the individual well zones. However, a variety of other well treatments may be employed utilizing various types of treatment materials, including fracturing fluid, proppant materials, slurries, chemicals, and other treatment materials designed to enhance the productivity of the well. The present approach to multi-zonal completion and treatment reduces completion cycle times, increases or maintains completion efficiency, improves well productivity, and increases recoverable reserves.
Also, the well treatments may be performed in conjunction with many types of well equipment deployed downhole into the wellbore. For example, various completions may employ a variety of flow control devices which are used to control the lateral flow of fluid out of and/or into the completion at the various well zones. In some applications, the flow control devices are mounted along a well casing to control the flow of fluid between an interior and exterior of the well casing. However, flow control devices may be positioned along internal tubing or along other types of well strings/tubing structures deployed in the wellbore. The flow control devices may comprise sliding sleeves, valves, and other types of flow control devices which may be actuated by a member dropped down through the tubular structure.
Referring generally to
In
In the example illustrated, wellbore 24 extends down through a subterranean formation 30 having a plurality of well zones 32. The downhole equipment 22 comprises a plurality of flow control devices 34 associated with the plurality of well zones 32. For example, an individual flow control device 34 may control flow from tubular structure 26 into the surrounding well zone 32 or vice versa. In some applications, a plurality of flow control devices 34 may be associated with each well zone 32. By way of example, the illustrated flow control devices 34 may comprise sliding sleeves, although other types of valves and devices may be employed to control the lateral fluid flow.
As illustrated, each flow control device 34 comprises a seat member 36 designed to engage a dart 38 which is dropped down through tubular structure 26 in the direction illustrated by arrow 40. Each dropped dart 38 may be hydraulically controlled to selectively engage a specific seat member 36 of a specific flow control device 34 to enable actuation of that specific flow control device 34. For example, the hydraulic control may be exercised via hydraulic pressure and/or flow rate acting against the dart 38 and controlled from a surface location. Engagement of the dart 38 with the specific, corresponding seat member 36 is not dependent on matching the diameter of the seat member 36 with a diameter of the dart 38. In the embodiment of
In the example illustrated, each seat member 36 comprises a profile 44, such as a lip, ring, unique surface feature, recess, or other profile which is designed to engage a corresponding engagement feature 46 of the dart 38. By way of example, the profile 44 may be formed in a sidewall 48 of seat member 36, the sidewall 48 also serving to create longitudinal flow through passage 42. In some applications, the engagement feature 46 is controlled by a hydraulically actuated mandrel which may be moved relative to a surrounding dart housing according to hydraulic input, e.g. hydraulic pressure and/or flow rate. The engagement feature 46 may be selectively actuated at a desired corresponding flow control device to prevent passage of the dart 38 and to enable shifting/actuation of that specific flow control device 34.
Referring generally to
In one example of a multizone treatment operation, the darts 38 are selectively, hydraulically actuated in a manner enabling engagement of seat members 36 sequentially starting at the lowermost or most distal flow control device 34. The dart 38 initially dropped is pumped down through flow control devices 34 until the engagement feature 46 is actuated radially outwardly into engagement with the profile 44 of the lowermost seat member 36 illustrated in the example of
After the initial well zone is treated, a subsequent dart 38 is dropped down through the flow through passages 42 of the upper flow control device or devices 34 until the engagement feature 46 is actuated and locked outwardly into engagement with the next sequential profile 44 of the next sequential flow control device 34. Pressure may then again be applied down through the tubular structure 26 to transition the flow control device 34 to a desired operational configuration which enables application of a desired treatment of the surrounding well zone 32. A third dart 38 may then be dropped for actuation and engagement with the seat member 36 of the third flow control device 34 to enable actuation of the third flow control device and treatment of the surrounding well zone. This process may be repeated as desired for each additional flow control device 34 and well zone 32. Depending on the application, a relatively large number of darts 38 is easily deployed to enable actuation of specific flow control devices along the wellbore 24 for the efficient treatment of multiple well zones.
The methodology may be used in cemented or open-hole completion operations, and darts 38 are used as free fall and/or pump-down darts to selectively engage and operate sliding sleeves or other types of flow control devices 34. Additionally, the darts 38 may be designed to enable immediate flow back independent of chemical processes or milling to remove plugs. In open-hole applications, hydraulic set external packers or swellable packers may be used to isolate well zones along wellbore 24.
In one example of an application, the flow control devices 34 are sliding sleeve valves which are initially run-in-hole with the casing 28 to predetermined injection point depths for a fracture stimulation. A casing cementation operation is then performed utilizing, for example, standard materials and procedures. In open-hole applications, open-hole packers may be used instead of cementation. Prior to fracture stimulation, a pressure activated sliding sleeve valve set opposite the deepest injection point is opened or, alternatively, this interval can be perforated using a variety of perforating techniques. In other applications, the sliding sleeve valve at the deepest injection point may be opened via the initial dart 38.
After creating the desired opening or openings at the deepest injection point, fracture treatment fluid is pumped into this first interval. During a treatment flush, a dart 38 is pumped down and this initial dart is actuated to engage a specific sliding sleeve 34. In some applications, the first interval may not be fracture treated but instead used to allow pumping down the first dart 38. When the dart 38 engages, fluid is pumped to increase pressure until the sliding sleeve 34 shifts to an open position. At this stage, the fracture treatment fluid is pumped downhole and into the surrounding well zone 32. This process of launching darts 38 in the treatment flush is continued until all of the intervals/well zones 32 are treated. The well may be flowed back immediately or shut-in for later flow back. The darts 38 may later be removed via milling, dissolving, or through other suitable techniques to restore the unrestricted internal diameter of the casing.
The flow control devices 34 may comprise a variety of devices, including sliding sleeves. One example of a flow control device/sliding sleeve valve 34 is illustrated in
In the embodiment illustrated, seat member 36 is in the form of a sliding sleeve 62 slidably positioned along an interior surface of the housing 56 between containment features 64. During movement downhole, the sliding sleeve 62 may be held in a position covering flow ports 58 by a retention member 66, such as a shear screw. The sliding sleeve 62 further comprises profile 44 designed to engage the engagement feature 46 of a dart 38 when the engagement feature 46 is in an actuated position. In some applications, the sliding sleeve 62 may comprise a secondary profile 68 designed to engage, for example, a suitable shifting tool. The secondary profile 68 provides an alternative way to open or close the sliding sleeve valve 34. When a designated dart 38 is engaged with profile 44 via engagement feature 46, application of pressure against the dart 38 causes retention member 66 to shear or otherwise release, thus allowing sliding sleeve 62 to transition along the interior of housing 56 until ports 58 are opened to lateral fluid flow. The seated dart 38 also isolates the casing volume below the sliding sleeve valve 34.
According to various environments described herein, the hydraulic darts 38 may be controlled from the surface using gross changes to flow or pressure. Both flow change and pressure change types of hydraulic darts 38 generally are designed so that a dart will temporarily seat against profile 44 and then pass through the flow control device 34 after a certain pressure is exceeded, e.g. after an applied pressure is sufficient to flex a collet carrying engagement feature 46. In one embodiment of pressure controlled hydraulic darts, a mandrel is moved relative to a collet in response to a pressure differential across the dart 38. A spring member is used to counter movement of the mandrel by pushing the mandrel in an uphole direction. The stiffness of the spring member is selected such that it will compress at a differential pressure (delta P) less than that required to push the engagement feature 46 past the internal profile 44. An orifice is used to regulate the flow of control fluid between two sides of a piston attached to the mandrel. Additionally, a check valve may be provided in parallel with the orifice to allow the mandrel to move back to its rest position at a quicker rate.
The orifice introduces a timing factor. For example, a certain amount of time is required for the mandrel to complete its motion and to lock the engagement feature 46 in place. If the pressure differential increases during the mandrel transition interval, the dart 38 is moved through the flow control device 34 and re-set. Additionally, a dart 38 that has been set by locking engagement feature 46 for interaction with profile 44 can be released by dropping the pressure below a spring pressure level and waiting a predetermined period of time to allow the mandrel to re-set. Once re-set, an increase in the pressure difference above the pressure differential needed to move the engagement feature 46 past the internal profile 44 allows the dart 38 to be pumped through that particular flow control device. In
Referring generally to
Within open interior 74, a ball or other type of flow blocking member 84 is positioned to seat against an internal seat 86 within mandrel 70. The flow blocking member 84 and internal seat 86 cooperate to function as a check valve which allows pressure to be applied in a downhole direction while allowing flow back in an uphole direction. Pumping down fluid against dart 38 and member 84 tends to shift mandrel 70 with respect to the dart housing 72, as illustrated in
The illustrated example of dart 38 further comprises an internal cavity 94 containing an internal fluid 96, e.g. hydraulic fluid, which passes through an orifice 98 as mandrel 70 is moved relative to dart housing 72. The orifice 98 controls locking of engagement feature 46 according to a predetermined pressure and time period. For example, pressure from above may be applied against dart 38 to create a pressure differential sufficient to overcome spring member 88 without pushing engagement feature 46 and collet 82 past the internal profile 44. While this pressure level is held, the mandrel 70 is transitioned relative to dart housing 72 until locking member 80 locks engagement feature 46 and collet 82 in the radially outward position against internal profile 44, as illustrated in
If the pressure differential is sufficiently decreased, spring member 88 is able to shift mandrel 70 with respect to dart housing 72 back to its original re-set position. A check valve 100 may be employed to enable faster return of the mandrel 72 its original position by allowing a freer flow of the internal dart fluid 96 as the mandrel 70 transitions back through dart housing 72. In the embodiment illustrated, a compensator piston 102 also is positioned within internal cavity 94 and acts against internal fluid 96. The compensator piston 102 can move to allow the total volume of internal fluid 96, e.g. oil, in the dart 38 to change due to, for example, thermal expansion. In an alternate embodiment, the compensator piston 102 may be located above or on an opposite side of orifice 98, as illustrated in
In the table below, various states of the mandrel 70 and the corresponding functions of dart 38 are set forth based on the pressure differential applied to the dart. In this example, the pressure differential may be lower or higher than the pressure differential required to compress spring member 88, to flex collet 82 (i.e. move engagement feature 46 past the internal profile 44), and/or to shear the shear member 66 of the flow control device 34 engaged by the dart 38. Various pressure differentials, mandrel states, and dart functions can be provided as follows:
Referring generally to
For example, the hydraulic dart 38 may be pumped down through the casing 38 or other tubular structure in and un-actuated configuration, as illustrated in
Referring generally to
The velocity fuse 104 remains against seat 86 as long as the pressure above the velocity fuse 104 is higher than below. If the pressure differential is reduced to a level which allows the spring 106 to push the velocity fuse off the corresponding seat 86, the flow blocking member 84 is again shifted to an open position. If the available flow is less than the predetermined flow rate, the flow blocking member 84/velocity fuse 104 remains open.
A pressure differential is produced by the fluid flowing through the velocity fuse 104. If this pressure differential times the area of the mandrel seal 78 exceeds the spring preload of spring member 88, the mandrel 70 is shifted and spring member 88 is compressed. This flow rate can be referred to as the spring flow rate. Similarly, there is a predetermined flow rate which creates a sufficient pressure differential so that engagement feature 46 can be moved past the internal profile 44, e.g. the collet 82 can collapse to allow passage of the engagement feature 46. This flow rate can be referred to as the collet flow rate.
In operation, the dart 38 is dropped or pumped down until the engagement feature 46 engages the internal profile 44 of a flow control device 34, as illustrated in
In the table below, various states of the mandrel 70 and the velocity fuse 104 along with the corresponding functions of dart 38 are set forth based on the flow rate conditions applied to the dart. In this example, the flow rate may be lower or higher than required to compress spring member 88, to flex collet 82 (i.e. move engagement feature 46 past the internal profile 44), and/or to close the velocity fuse 104. Various flow rate conditions, mandrel states, velocity fuse states, and dart functions can be provided as follows:
If the flow control dart 38 is set in the wrong flow control device/sliding sleeve 34, the dart 38 may be released by sufficiently lowering the flow rate to release the collet 82/engagement feature 46 from locking member 80.
In some applications, the hydraulic darts 38 may be modified to add a pressure relief valve in parallel with the orifice 98 to allow high flows/pressures to lock the dart 38 more quickly. Additionally, the darts 38 may be used with feedback systems to track the darts position at the surface. For example, each passage of the dart 38 through a corresponding internal profile 44 generates a pressure pulse that can be counted at the surface. Additionally, when dart 38 is set or locked in engagement with a corresponding internal profile 44, the dart can serve as a two-way reflector which can be pinged from the surface to verify position before committing to a final pressure increase to open or otherwise change the configuration of the flow control device.
Referring generally to
The system and methodology described herein may be employed in non-well related applications which require actuation of devices at specific zones along a tubular structure. Similarly, the system and methodology may be employed in many types of well treatment applications and other applications in which devices are actuated downhole via dropped darts without requiring any changes to the diameter of the internal fluid flow passage. Different well treatment operations may be performed at different well zones without requiring separate interventions operation. Sequential darts may simply be dropped into engagement with specific well devices for actuation of those specific well devices at predetermined locations along the well equipment positioned downhole.
Although only a few embodiments of the system and methodology have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.
