Fracturing head with replaceable inserts for improved wear resistance and method of refurbishing same

Fracturing heads with one or more replaceable wear-resistant inserts have annular sealing elements for inhibiting fracturing fluids from circulating between the inserts and a main body of the fracturing head. Worn inserts and degraded sealing elements are easily replaced to refurbish the fracturing head without replacing or rebuilding the main body. Service life of the main body is therefore significantly prolonged. In one embodiment, an entire flow path through the main body is lined with wear-resistant replaceable inserts to further prolong the service life of the main body.

CROSS-REFERENCE TO RELATED APPLICATIONS

MICROFICHE APPENDIX

Not Applicable.

TECHNICAL FIELD

The present invention relates in general to the fracturing of subterranean hydrocarbon formations and, in particular, to a wear-resistant fracturing head used to pump high pressure fluids and abrasive proppants into a well requiring stimulation.

BACKGROUND OF THE INVENTION

Subterranean hydrocarbon formations are routinely stimulated to enhance their geological permeability. A well known technique for stimulating a hydrocarbon formation is to fracture the formation by pumping into the well highly pressurized fluids containing suspended proppants, such as sand, resin-coated sand, sintered bauxite or other such abrasive particles. A fracturing fluid containing proppants is also known as a “slurry.”

As is well known in the art, a fracturing head (or “frac head”) has ports to which high pressure conduits known as “frac lines” are connected. The frac lines conduct the highly pressurized slurry from high pressure pumps to the fracturing head. The fracturing head is typically secured to a wellhead valve. The fracturing head includes a main body with a central bore for conveying the slurry downwardly into the well. Due to the high fluid pressures, high transfer rates and the abrasive properties of the proppants in the slurry, components of the fracturing head that are exposed to the pressurized slurry erode or “wash”, as such erosion is referred to by those familiar with well fracturing processes.

As is well known in the art, fracturing heads are expensive to manufacture because they are made from hardened tool steel (AISI 4140, for example). Attempts have therefore been made to provide hardened, wear-resistant inserts that can be replaced in order to extend the service life of a fracturing head. For example, published Canadian Patent Application No. 2,430,784 to McLeod et al., describes a fracturing head with a replaceable abrasion-resistant wear sleeve secured in the main bore in the body of the fracturing head. The fracturing head defines a generally Y-shaped flow path. At least two streams of fracturing slurry are pumped through respective side ports angled at approximately 45 degrees to the main bore. The two streams of slurry mix turbulently at a confluence of the side ports. The slurry then flows downstream through the main bore and into the well. The wear sleeve is positioned so that the respective streams of slurry are directed at the wear sleeve rather than at the body of the fracturing head which,. being of a softer steel that of the wear sleeve, is more prone to erosion. However, due to the location of the wear sleeve, the turbulent slurry impinges a top edge of the wear sleeve, which tapers to a feathered edge. The feathered edge of the wear sleeve thus has a tendency to erode. As the feathered top edge erodes, pressurized slurry flows between the wear sleeve and the body of the fracturing head, eroding the body of the fracturing head, causing damage.

Consequently, there exists a need for a fracturing head with improved wear resistance.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a fracturing head with improved wear resistance.

In accordance with a first aspect of the invention, a fracturing head includes a main body having a side port for connection to a high pressure line that conducts high pressure fracturing fluids from a high pressure pump, the main body including a main bore in fluid communication with the side port for conveying the fracturing fluids through the fracturing head. The fracturing head further includes a replaceable wear-resistant insert secured within the main bore and an annular sealing element disposed around a top end of the insert for inhibiting the fracturing fluids from penetrating an annular gap between the insert and the main body.

In one embodiment, the fracturing head includes a plurality of annular sealing elements disposed between the insert and the main body for inhibiting the fracturing fluids from penetrating the annular gap between the insert and the main body.

In accordance with a second aspect of the invention, a fracturing head includes a T-shaped main body having a main bore that extends from a port in a top end of the main body through a bottom end of the main body; a pair of side ports having side port bores that communicate with the main bore; at least one replaceable wear resistant insert that is received the main bore; and at least one replaceable wear-resistant insert received in each of the side ports.

In one embodiment, the at least one replaceable wear-resistant insert that is received in the main bore includes: a first replaceable wear-resistant insert received in the port in the top end of the main body; a second replaceable wear-resistant insert received in the main body beneath the first insert, the second insert including opposed circular seats for respectively receiving inner ends of the inserts received in the respective side ports; and a third replaceable wear-resistant insert that is received in a retainer flange connected to a bottom end of the main body.

In accordance with a third aspect of the invention, a fracturing head includes a main body having at least two angled side ports for connection to respective high pressure lines that conduct high pressure fracturing fluids from high pressure pumps, the main body including a main bore in fluid communication with the angled side ports for conveying the fracturing fluids through the fracturing head. The fracturing head also includes a replaceable wear-resistant insert secured in the main bore downstream of the side ports, the insert having an impingement surface against which substantially all of a jet of pressurized fracturing fluids directly impinges when pressurized fracturing fluids are pumped through one or more of the angled side ports, the impingement surface being between top and bottom ends of the wear resistant insert. The fracturing head further includes at least one annular sealing element disposed between a top end of the wear resistant insert and the main body for inhibiting the fracturing fluids from penetrating between the wear resistant insert and the main body.

In accordance with a fourth aspect of the invention, a method of refurbishing a fracturing head includes the steps of disassembling the fracturing head; removing a worn replaceable insert from a bore of a main body of the fracturing head; removing, inspecting and replacing any worn annular sealing elements associated with the replaceable insert; inserting a new replaceable insert in the bore of the main body; and reassembling the fracturing head.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In general, and as will be explained in detail below, a fracturing head in accordance with the invention includes one or more replaceable wear-resistant inserts and annular sealing elements for inhibiting fracturing fluids from circulating between the inserts and a main body of the fracturing head. Worn inserts and degraded sealing elements are easily replaced to refurbish the fracturing head without replacing or rebuilding the main body. Service life of the main body is therefore significantly prolonged. As will be described below, in one embodiment, an entire flow path through the main body is lined with wear-resistant replaceable inserts to further prolong the service life of the main body.

As shown inFIGS. 1 and 2, a fracturing head10in accordance with an embodiment of the invention includes a T-shaped main body12. The main body12includes a top port14as well as a pair of opposed side ports16to which high-pressure lines (not shown) can be connected and through which pressurized fracturing fluids can then be pumped. As is known in the art, the fracturing fluids include a slurry of treatment fluids and abrasive proppants which the fracturing head10conducts down the well for fracturing subterranean hydrocarbon formations. The main body12can be secured to the top of a retainer flange18which in turn can be secured to a wellhead assembly (not shown).

As shown inFIG. 2, the fracturing head10further includes one or more of a plurality of replaceable wear-resistant inserts and annular sealing elements collectively designated by reference numeral20. The wear-resistant inserts (or “sleeves”) and associated annular sealing elements can be secured within one or more bores in the fracturing head10in order to provide a wear-resistant flow-path lining that inhibits erosion of the main body12and thus prolongs the service life of the fracturing head10. The various inserts will now be described individually.

As shown inFIG. 2, a main insert22can be inserted into a main bore in the main body12. The main insert22is a thick-walled sleeve having circular apertures at top and bottom ends. The main insert22further includes, in the cylindrical side wall, two opposed circular apertures each surrounded by an annular lip. The main insert can therefore receive respective side port inserts26as well as respective side gaskets33. The side port inserts26are designed to be inserted into respective bores in the opposed side ports16. Similarly, a top port insert24can be inserted into a bore in the top port14. Furthermore, a retainer flange insert28can be inserted into a bore in the retainer flange18.

An upper annular sealing element30and a lower annular sealing element32provide fluid-tight seals above and below the main insert22. The upper annular sealing element30is disposed around a top end of the main insert22to inhibit the fracturing fluids from penetrating an annular gap between the main insert22and the main body12. The lower annular sealing element32is disposed directly beneath the main insert22, i.e., where the main insert22abuts both the retainer flange18and a retainer flange insert28. A pair of side gaskets33provide fluid-tight seals between the side port inserts and the main insert22.

As will be readily appreciated by those of ordinary skill in the art, the fracturing head10may include only a single insert and a respective sealing element or it may include any combination of replaceable inserts and annular sealing elements. The inserts and annular sealing elements may be disposed contiguously to provide a protective lining over the entire flow path or merely over only a portion of the flow path.

FIG. 3is a cross-sectional view of another T-shaped fracturing head10in accordance with another embodiment of the invention. The fracturing head10shown inFIG. 3includes a T-shaped main body12having a main bore13. The main body12also includes a top port14having a top bore15as well as a pair of opposed side ports16having respective side bores17, all of which are in fluid communication with the main bore13. A retainer flange18is secured to the bottom of the main body12. The retainer flange18includes a retainer flange bore19which is also in fluid communication with the main bore. The main bore13, top bore15, side bores17and retainer flange bore19together define a flow path through the fracturing head10.

The side ports16and the top port14are threaded for the connection of high-pressure lines (not shown) for conducting high-pressure fracturing fluids from a high-pressure pump (not shown) into the well. It is common practice to connect high-pressure lines to two of the three ports for inflow of pressurized fracturing fluids into the fracturing head while the third port is closed with a valve and reserved for pressure alleviation in the event of “screenout”. These highly pressurized fracturing fluids mix turbulently at the confluence of the side bores and top bore and then flow downwardly into the well through the main bore13and retainer flange bore19.

As shown inFIG. 3, a main (replaceable wear-resistant) insert22is secured within the main bore13in the main body12. In this embodiment, the main insert22includes a nozzle with an internal taper used to direct a flow of fluid from the side ports (and/or top port) through a bottom of the fracturing head. Upper and lower main annular sealing elements30,32are disposed along the upper and lower surfaces of the main insert22in order to inhibit penetration of abrasive fracturing fluids into an annular gap between the main insert22and the main body12. Consequently, the susceptibility of the main body to erosion is diminished, thus prolonging the service life of the fracturing head.

In the embodiment illustrated inFIG. 3, the fracturing head also includes a second main bore insert23secured within the main bore13upstream of the first main bore insert22. The second main bore insert and the first main bore insert22are separated by the upper annular sealing element30.

As shown inFIG. 3, the side bores17of each side port16are also protectively lined with respective side port inserts26. Similarly, the top bore15of the top port14includes first and second top port inserts24,25separated by a top port annular sealing element34. A pair of side port annular sealing elements36are disposed circumferentially around the side bores17at the abutment of the side port inserts26and the second top port insert25and the second main bore insert23.

As shown inFIG. 3, the retainer flange18includes a retainer flange insert28within the retainer flange bore19. The top of the retainer flange insert abuts the lower main annular sealing element32.

As shown inFIG. 3, a pair of annular grooves38are machined into the bottom of the main body12. Each of the annular grooves38receives an O-ring for providing a fluid-tight seal between the bottom of the main body12and the retainer flange18. Further annular grooves40are machined into both the bottom of the main body12and the top of the retainer flange18for accommodating a metal ring gasket as described in applicant's co-pending U.S. patent application Ser. No. 10/690,142 filed Oct. 21, 2003 and entitled METAL RING GASKET FOR A THREADED UNION, the entire disclosure of which is hereby incorporated by reference herein.

The retainer flange18is secured to the bottom of the main body12of the fracturing head10using threaded fasteners (which are not shown). The retainer flange18includes an upper flange having a plurality of equidistantly spaced bores42. The bores42in the upper flange align with corresponding tapped bores44in the bottom of the main body12.

In one embodiment, the annular sealing elements are ring gaskets made of either a hydrocarbon rubber (such as Viton® Nordel® available from Dow Chemical) or a polyurethane.

In one embodiment, the main body12and the retainer flange18are machined from AISI 4140 heat-treated steel whereas the inserts are machined from a harder steel such as AISI 4340 steel having a Rockwell C Hardness of 48–56.

FIG. 4is a cross-sectional view of a Y-shaped fracturing head in accordance with yet a further embodiment of the invention. In this embodiment, the fracturing head10includes two angled side ports16each having a side bore17in fluid communication with a main bore13. In use, high-pressure lines are connected to the angled side ports16and/or to the top port14in the manner described above. High-pressure fracturing fluids are thus conducted at high velocity down the side bores and/or top bore. These fracturing fluids mix turbulently at the confluence of the main bore, top bore and side bores and the fluids flow downwardly into the well through the main bore13and the retainer flange bore19.

As shown inFIG. 4, a main replaceable wear-resistant insert22is secured in the main bore13downstream of the side ports16. The main insert22has an impingement surface50against which substantially all of a jet of pressurized fracturing fluids directly impinges when pressurized fracturing fluids are pumped through one or more of the angled side ports16. The impingement surface50is a portion of the exposed inner surface of the main insert that is spaced far enough beneath the top of the main insert that substantially none of the jet impinges on the interface between the top of the main insert and the main body. In other words, the main replaceable wear-resistant insert22is positioned within the main bore so that the fracturing fluids pumped through the angled side ports generally impinge only the impingement surface50spaced beneath the top surface of the insert and above a bottom surface of the insert.

As shown inFIG. 4, the fracturing head10may further include one or more annular grooves38that are machined into the main insert and/or the main body. These annular grooves38each accommodate an O-ring for providing a fluid-tight seal between the main insert22and the main body. The O-rings inhibit fracturing fluids from penetrating between the main insert and the main body. As noted above, the seals inhibit erosion of the main body and thus prolong the service life of the fracturing head.

As shown inFIG. 4, the fracturing head10further includes an auxiliary replaceable wear-resistant insert22athat is secured within the main bore13downstream of the main insert22. The auxiliary insert22aincludes a top annular groove in which an O-ring is seated for providing a fluid-tight seal between the auxiliary insert22aand the main insert22. The auxiliary insert22aalso includes three peripheral annular grooves38in which O-rings are seated for providing a fluid-tight seal between the auxiliary insert22aand the bottom of the main body12. In addition, the auxiliary insert22aincludes a bottom annular groove40(corresponding to an annular groove in the top of the retainer flange18) in which a metal ring gasket can be seated to provide a fluid-tight seal between the top of the retainer flange and the bottom of the auxiliary insert.

As shown inFIG. 4, the auxiliary insert22ais retained within the bore13by a retainer ring48which, in turn, is fastened to the bottom of the main body with threaded fasteners46. As was noted above with respect to the previous embodiment, the retainer flange18is secured to the main body12using fasteners that are inserted through boreholes42and threaded into tapped boreholes44.

As shown inFIG. 4, at the top of the fracturing head10is a stud pad60having tapped boreholes62as well as an annular groove in which a metal ring gasket can be seated. The stud pad60permits stacking of two or more fracturing heads.

In one embodiment, the main body12, retainer flange18, retainer ring48and auxiliary insert22aare machined from AISI 4140 heat-treated steel. The main insert22, against which the fracturing fluid impinges, is machined from a harder steel such as AISI 4340 steel having a Rockwell C Hardness of 48–56. The auxiliary insert is made of a softer, more elastic steel which compresses more readily than the 4340 steel of the main insert22, and thus permits the retainer flange to be fastened tightly to the bottom of the main body without risk of cracking the brittle main insert22.

The service life of the fracturing head can be prolonged by replacing worn inserts and/or worn annular sealing elements. To refurbish the fracturing head, the fracturing head is disassembled by detaching the main body from the retainer flange. The inserts and sealing elements can then be removed and inspected. Any worn inserts and/or sealing elements can then be replaced before the fracturing head is reassembled.

Persons of ordinary skill in the art will appreciate, in light of this specification, that minor variations may be made to the components of the fracturing head without departing from the sprit and scope of the invention. The embodiments of the invention described above are therefore intended to be exemplary only and the scope of the invention is limited only by the scope of the appended claims.