Patent Grant
8939202
The field of the invention is nozzles used in formation fracturing and more particularly nozzles used to enhance the initiation and propagation of formation fractures by adding a feature of cyclical impingement to the initial perforation made by the nozzle assembly.
Fracturing in open hole is a complex subject and has been studied and written about by various authors. Whether using explosives or fluid jets one of the problems with the initiated fractures is in the way they propagate. If the propagation pattern is more tortuous as the fractures emanate from the borehole an undesirable condition called screenout can occur that can dramatically decrease the well productivity after it is put on production.
Hydraulically fracturing from any borehole in any well orientation is complex because of the earth's ambient stress field operating in the area. This is complicated further because of the extreme stress concentrations that can occur along the borehole at various positions around the well. For instance, there are positions around the borehole that may be easier to create a tensile crack than other positions where extreme compressive pressures are preventing tensile failure. One way that has been suggested to minimize this condition is to use jets that create a series of fan shaped slots in the formation with the thinking that a series of coplanar cavities in the formation will result in decreased tortuosity. This concept is discussed in SPE 28761 Surjatmaadja, Abass and Brumley Elimination of Near-wellbore Tortuosities by Means of Hydrojetting (1994). Other references discus creating slots in the formation such as U.S. Pat. Nos. 7,017,665; 5,335,724; 5,494,103; 5,484,016 and U.S. Publication 2009/0107680.
Other approaches oriented the jet nozzles at oblique angles to the wellbore to try to affect the way the fractures propagated. Some examples of such approaches are U.S. Pat. Nos. 7,159,660; 5,111,881; 6,938,690; 5,533,571; 5,499,678 and U.S. Publications 2008/0083531 and 2009/0283260.
Other approaches involved some form of annulus pumping in conjunction with jet fracturing. Some examples of this technique are U.S. Pat. Nos. 7,278,486; 7,681,635; 7,343,974; 7,337,844; 7,237,612; 7,225,869; 6,779,607; 6,725,933; 6,719,054 and 6,662,874.
Pulsing techniques have been used in jet drilling or in conventional drilling to pulse the bit nozzle flow as described in U.S. Pat. Nos. 4,819,745 and 6,626,253. Also related to these applications is SPE paper 130829-MS entitled Hydraulic Pulsed Cavitating Jet Assisted Deep Drilling: An Approach to Improve Rate of Penetration.
Jets mounted to telescoping assemblies have been suggested with the idea being that if the jet is brought closer to the formation the fracturing performance will improve. This was discussed in U.S. application Ser. No. 12/618,032 filed Nov. 13, 2009 called Open Hole Stimulation with Jet Tool and is commonly assigned to Baker Hughes Inc. In another variation of telescoping members used for fracturing the idea was to extend the telescoping members to the borehole wall and to set spaced packers in the annulus so as to avoid the need to cement and to allow production from the telescoping members after using some of them to initially fracture the formation. This was discussed in U.S. application Ser. No. 12/463,944 filed May 11, 2009 and entitled Fracturing with Telescoping Members and Sealing the Annular Space and is also commonly assigned.
The present invention seeks to improve the extent of the fracturing that is accomplished beyond the initial formation perforation that is initiated explosively or with a direct impingement nozzle. The concept is to cyclically bombard the perforation with a jet stream or streams. This is accomplished in several ways including rotationally mounting a spray plate with angled spray exit streams that induce the plate to rotate on its axis. A specific location within the perforation will then by cyclically impinged and then after a pause will be impinged again. Another way is a combination of a stationary and rotating plate to create pulsing jet streams that further extend fractures that initiate in a perforation or from jet impingement in a normal direction. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the specification and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.
A fracturing jet nozzle assembly features a series of angles nozzles on a rotatably mounted plate that operates in conjunction with a central nozzle or nozzles. The slanted nozzles are aimed into the perforation where the central nozzle is aimed directly so that the rotation of the nozzle plate from the slanted nozzles results in cyclic impacts in the perforation from where the fractures will propagate. The cyclic loading results in greater fracture formation and propagation. In another variation, relatively movable plates employing slanted nozzles rotate one plate with respect to another to get the effect of cyclic pulses of jetting fluid impingement in the perforation to enhance formation and propagation of fractures from the perforation.
The assembly 18 is shown in
The skew in the openings 34 directs the jets obliquely as shown by arrows 39 to the straight jet stream 40 coming from opening or openings 32. Additionally, because plate 30 is rotating, the same spot 41 for example does not get impacted with a constant stream but rather gets impacted cyclically as each nozzle 34 spins around and aligns with the spot 41. As a result of this cyclic impact pattern the more fractures 42 are initiated and propagated.
The rotational movement of the nozzles helps to start and propagate fractures during the fracturing procedure by building on the perforations that are there from the perforating or the substantially parallel nozzles if they are used. The pulsing impacts on the borehole wall help to break up the rock and start and extend the fractures. The use of the energy of the flowing fluid to get the turning action keeps the design simple. More elaborate designs that mechanically drive the plate with the nozzles can be used but they would be more expensive and more prone to breakage. The rotating plate can be supported on a stationary bushing made of a soft metal or plastic or composite material. In the alternative more expensive ball or roller bearings can be used. The assembly can be extendable by force of the flow through the nozzles and the extended position can be locked in with a ratchet or body lock ring or some other device that allows relative movement in a single direction. The rotating plate can be a circular disc or it can be an annular shape that surrounds a stationary core where the core has substantially parallel oriented nozzles with respect to the axis of the assembly. The assembly can be in arrays on casing with parallel rows or offset spiral patterns or random locations in a desired zone to be fractured to assure adequate fracturing. While the preferred orientation of each assembly is perpendicular to the axis of the casing in which it is mounted, the assemblies can also be secured in a skewed orientation to the casing axis in a manner where the axis of the assembly 10 either passes through the axis of the tubular 16 or is offset from it.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.
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