Heavy duty matrix bit

An apparatus and method for manufacturing a downhole tool that reduces failures occurring along a bondline between a cemented matrix coupled around a blank. The cemented matrix material is formed from a powder and a binder material. The blank includes an internal blank component and a coating coupled around at least a portion of the surface of the internal blank component. The internal blank component includes a top portion and a bottom portion. The internal blank component is substantially cylindrically shaped and defines a channel extending through the top portion and the bottom portion. The coating is a metal in some exemplary embodiments. The coating reduces the migration of the binder material into the blank thereby allowing the control of intermetallic compounds thickness within the bondline.

BACKGROUND OF THE INVENTION

This invention relates generally to downhole tools and methods for manufacturing such items. More particularly, this invention relates to infiltrated matrix drilling products including, but not limited to, fixed cutter bits, polycrystalline diamond compact (“PDC”) drill bits, natural diamond drill bits, thermally stable polycrystalline (“TSP”) drill bits, bi-center bits, core bits, and matrix bodied reamers and stabilizers, and the methods of manufacturing such items.

Full hole tungsten carbide matrix drill bits for oilfield applications have been manufactured and used in drilling since at least as early as the 1940's.FIG. 1shows a cross-sectional view of a downhole tool casting assembly100in accordance with the prior art. The downhole tool casting assembly100consists of a thick-walled mold110, a stalk120, one or more nozzle displacements122, a blank124, a funnel140, and a binder pot150. The downhole tool casting assembly100is used to fabricate a casting (not shown) of a downhole tool.

According to a typical downhole tool casting assembly100, as shown inFIG. 1, and a method for using the downhole tool casting assembly100, the thick-walled mold110is fabricated with a precisely machined interior surface112, and forms a mold volume114located within the interior of the thick-walled mold110. The thick-walled mold110is made from sand, hard carbon graphite, ceramic, or other known suitable materials. The precisely machined interior surface112has a shape that is a negative of what will become the facial features of the eventual bit face. The precisely machined interior surface112is milled and dressed to form the proper contours of the finished bit. Various types of cutters (not shown), known to persons having ordinary skill in the art, can be placed along the locations of the cutting edges of the bit and can also be optionally placed along the gage area of the bit. These cutters can be placed during the bit fabrication process or after the bit has been fabricated via brazing or other methods known to persons having ordinary skill in the art.

Once the thick-walled mold110is fabricated, displacements are placed at least partially within the mold volume114of the thick-walled mold110. The displacements are typically fabricated from clay, sand, graphite, ceramic, or other known suitable materials. These displacements consist of the center stalk120and the at least one nozzle displacement122. The center stalk120is positioned substantially within the center of the thick-walled mold110and suspended a desired distance from the bottom of the mold's interior surface112. The nozzle displacements122are positioned within the thick-walled mold110and extend from the center stalk120to the bottom of the mold's interior surface112. The center stalk120and the nozzle displacements122are later removed from the eventual drill bit casting so that drilling fluid (not shown) can flow though the center of the finished bit during the drill bit's operation.

The blank124is a cylindrical steel casting mandrel that is centrally suspended at least partially within the thick-walled mold110and around the center stalk120. The blank124is positioned a predetermined distance down in the thick-walled mold110. According to the prior art, the distance between the outer surface of the blank124and the interior surface112of the thick-walled mold110is typically 12 millimeters (“mm”) or more so that potential cracking of the thick-walled mold110is reduced during the casting process.

Once the displacements120,122and the blank124have been positioned within the thick-walled mold110, tungsten carbide powder130is loaded into the thick-walled mold110so that it fills a portion of the mold volume114that is around the lower portion of the blank124, between the inner surfaces of the blank124and the outer surfaces of the center stalk120, and between the nozzle displacements122. Shoulder powder134is loaded on top of the tungsten carbide powder130in an area located at both the area outside of the blank124and the area between the blank124and the center stalk120. The shoulder powder134is made of tungsten powder or other known suitable material. This shoulder powder134acts to blend the casting to the steel blank124and is machinable. Once the tungsten carbide powder130and the shoulder powder134are loaded into the thick-walled mold110, the thick-walled mold110is typically vibrated to improve the compaction of the tungsten carbide powder130and the shoulder powder134. Although the thick-walled mold110is vibrated after the tungsten carbide powder130and the shoulder powder134are loaded into the thick-walled mold110, the vibration of the thick-walled mold110can be done as an intermediate step before, during, and/or after the shoulder powder134is loaded on top of the tungsten carbide powder130.

The funnel140is a graphite cylinder that forms a funnel volume144therein. The funnel140is coupled to the top portion of the thick-walled mold110. A recess142is formed at the interior edge of the funnel140, which facilitates the funnel140coupling to the upper portion of the thick-walled mold110. Typically, the inside diameter of the thick-walled mold110is similar to the inside diameter of the funnel140once the funnel140and the thick-walled mold110are coupled together.

The binder pot150is a cylinder having a base156with an opening158located at the base156, which extends through the base156. The binder pot150also forms a binder pot volume154therein for holding a binder material160. The binder pot150is coupled to the top portion of the funnel140via a recess152that is formed at the exterior edge of the binder pot150. This recess152facilitates the binder pot150coupling to the upper portion of the funnel140. Once the downhole tool casting assembly100has been assembled, a predetermined amount of binder material160is loaded into the binder pot volume154. The typical binder material160is a copper alloy or other suitable known material. Although one example has been provided for setting up the downhole tool casting assembly100, other examples can be used to form the downhole tool casting assembly100.

The downhole tool casting assembly100is placed within a furnace (not shown) or other heating structure. The binder material160melts and flows into the tungsten carbide powder130through the opening158of the binder pot150. In the furnace, the molten binder material160infiltrates the tungsten carbide powder130to fill the interparticle space formed between adjacent particles of tungsten carbide powder130. During this process, a substantial amount of binder material160is used so that it fills at least a substantial portion of the funnel volume144. This excess binder material160in the funnel volume144supplies a downward force on the tungsten carbide powder130and the shoulder powder134. Once the binder material160completely infiltrates the tungsten carbide powder130, the downhole tool casting assembly100is pulled from the furnace and is controllably cooled. Upon cooling, the binder material160solidifies and cements the particles of tungsten carbide powder130together into a coherent integral mass310(FIG. 3). The binder material160also bonds this coherent integral mass310(FIG. 3) to the steel blank124thereby forming a bonding zone190, which is formed along at least a chamfered zone area198of the steel blank124and a central zone area199of the steel blank124. The coherent integral mass310(FIG. 3) and the blank124collectively form the matrix body bit200(FIG. 2), a portion of which is shown inFIGS. 2 and 3. Once cooled, the thick-walled mold110is broken away from the casting. The casting then undergoes finishing steps which are known to persons having ordinary skill in the art, including the addition of a threaded connection (not shown) coupled to the top portion of the blank124. Although the matrix body bit200(FIG. 2) has been described to be formed using the process and equipment described above, the process and/or the equipment can be varied to still form the matrix body bit200(FIG. 2).

FIG. 2shows a magnified cross-sectional view of the bonding zone190located at the chamfered zone area198(FIG. 1) within the matrix body bit200in accordance with the prior art.FIG. 3shows a magnified cross-sectional view of the bonding zone190located at the central zone area199(FIG. 1) within the matrix body bit200in accordance with the prior art. Referring toFIGS. 2 and 3, the coherent integral mass310is bonded to the steel blank124via the bonding zone190that is formed along the surface of the steel blank124and which extends inwardly into the interior portion of the steel blank124. A portion of the binder material160diffuses into the steel blank124and reacts with the steel blank124to form this bonding zone190. The bonding zone190includes intermetallic compounds290. These intermetallic compounds290have an average hardness level of about 250 HV, which corresponds to about twice the hardness of the binder and steel matrix. According toFIG. 2, the bonding zone190is formed having a thickness215ranging from about sixty-five micrometers (μm) to about eighty μm in the chamfered zone area198(FIG. 1). According toFIG. 3, the bonding zone190is formed having a thickness315ranging from about ten μm to about twenty μm in the central zone area199(FIG. 1). The thicknesses215,315and/or volumes of the bonding zone190are dependent upon the exposure time and the exposure temperature. Exposure temperature is related to the type of binder material160that is used to cement the tungsten carbide particles to one another. Manufacturers typically use the same binder material160over long periods of time, such as ten year or more, because of the knowledge gained with respect to the binder material160used. Thus, the exposure temperature is substantially the same from one casting to another. Exposure time is not always the same, but instead, is related to the bit diameter that is to be manufactured. When the bit diameter to be manufactured is relatively large, there is a larger volume of tungsten carbide particles that cemented to one another. Hence, the exposure time also is relatively longer, thereby providing more time for cementing the larger volume of tungsten carbide particles. Thus, since the exposure temperature is the same from one casting to another, and the exposure time is the same for casting similar bit diameters, it follows that the thicknesses215,315of intermetallic compounds290formed within the bit is consistent from one casting to another for a same bit diameter.

Initially, natural diamond bits were used in oilfield applications. These natural diamond bits performed by grinding the rock within the wellbore, and not by shearing the rock. Thus, these natural diamond bits experienced little to no torque, and hence very little stress was experienced at the bonding zone190of the natural diamond bits. With the advent of PDC drill bits, the bits sheared the rock within the wellbore and began experiencing more torque. However, these initial PDC drill bits were fabricated relatively small, about six inch diameters to about 12¼ inch diameters, and the prior art fabrication method described above continued to perform well. Later, PDC drill bits were fabricated having larger diameters and failures began occurring along the bonding zone190. Specifically, decohesion began occurring between the blank124and the coherent integral mass310, or matrix, at the bonding zone190. These intermetallic compounds290are a source for causing mechanical stresses to occur along the bonding zone190during drilling applications because there is a contraction of volume occurring when the intermetallic compounds290are formed. Now that cutter technology has improved, the demand placed upon the bits have also increased. Bits are being drilled for more hours. Bits also are being used with much more energy, which includes energy produced from increasing the weight on bit and/or from increasing the rotational speed of the bit. This increased demand on the bits is causing the decohesion failure to become a recurring problem in the industry. As the thickness or volume of the intermetallic compounds290increases, the risk of decohesion also increases.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates generally to downhole tools and methods for manufacturing such items. More particularly, this invention relates to infiltrated matrix drilling products including, but not limited to, fixed cutter bits, polycrystalline diamond compact (“PDC”) drill bits, natural diamond drill bits, thermally stable polycrystalline (“TSP”) drill bits, bi-center bits, core bits, and matrix bodied reamers and stabilizers, and the methods of manufacturing such items. Although the description provided below is related to a drill bit, embodiments of the present invention relate to any infiltrated matrix drilling product.

FIG. 4shows a cross-sectional view of a blank400in accordance with an exemplary embodiment. The blank400includes an internal blank component410and a metal coating420coupled around at least a portion of the surface of the internal blank component410. The internal blank component410is similar to the blank124(FIG. 1) above. The internal blank component410is a cylindrically, hollow-shaped component and includes a cavity412extending through the entire length of the internal blank component410. According to some exemplary embodiments the internal blank component410also includes a top portion414and a bottom portion416. The top portion414has a smaller outer circumference than the bottom portion416. According to some exemplary embodiments, the internal blank component410is fabricated from steel; however, any other suitable material known to people having ordinary skill in the art is used in other exemplary embodiments.

The metal coating420is applied onto at least a portion of the surface of the internal blank component410. In some exemplary embodiments, the metal coating420is applied onto the surface of the entire internal blank component410. In other exemplary embodiments, the metal coating420is applied onto a portion of the surface of the internal blank component410. For example, the metal coating420is applied onto the surface of the bottom portion416, which is the portion that bonds to the matrix material, or a coherent integral mass710(FIG. 7), which is described below. The metal coating420is applied onto the internal blank component410using electroplating techniques. Alternatively, other techniques, such as plasma spray, ion bombardment, electro-chemical depositing, or other known coating techniques, are used to apply the metal coating420onto the internal blank component410in other exemplary embodiments. The metal coating420is fabricated using a material that reduces the formation of intermetallic compounds690(FIG. 6) along the surface of the blank400(FIG. 4). Specifically, the metal coating420reduces the migration of binder material560(FIG. 5) from the coherent integral mass710(FIG. 7) into the internal blank component410at the temperature and exposure time during the fabrication process. The metal coating420is fabricated from nickel according to some exemplary embodiments. Alternatively, the metal coating420is fabricated using at least one of brass, bronze, copper, aluminum, zinc, gold, molybdenum, a metal alloy of any previously mentioned metal, or any other suitable material that is capable of reducing the migration of binder material560(FIG. 5) into the internal blank component410. Alternatively, a different type of coating, such as a polymer coating, is used in lieu of the metal coating.

The metal coating420is applied onto the internal blank component410having a thickness422ranging from about five μm to about 200 μm. In another exemplary embodiment, the metal coating420has a thickness422ranging from about five μm to about 150 μm. In yet another exemplary embodiment, the metal coating420has a thickness422ranging from about five am to about eighty μm. In a further exemplary embodiment, the metal coating420has a thickness422ranging less than or greater than the previously mentioned ranges. In certain exemplary embodiments, the thickness422is substantially uniform, while in other exemplary embodiments, the thickness422is non-uniform. For example, the thickness422is greater along the surface of the internal blank component410that would typically form a greater thickness of the intermetallic compound during the fabrication process, such as the chamfered zone area598(FIG. 5).

FIG. 5shows a cross-sectional view of a downhole tool casting assembly500using the blank400in accordance with the exemplary embodiment. Referring toFIG. 5, the downhole tool casting assembly500includes a mold510, a stalk520, one or more nozzle displacements522, the blank400, a funnel540, and a binder pot550. The downhole tool casting assembly500is used to fabricate a casting (not shown) of a downhole tool, such as a fixed cutter bit, a PDC drill bit, a natural diamond drill bit, and a TSP drill bit. However, the downhole tool casting assembly500is modified in other exemplary embodiments to fabricate other downhole tools, such as a bi-center bit, a core bit, and a matrix bodied reamer and stabilizer.

The mold510is fabricated with a precisely machined interior surface512, and forms a mold volume514located within the interior of the mold510. The mold510is made from sand, hard carbon graphite, ceramic, or other known suitable materials. The precisely machined interior surface512has a shape that is a negative of what will become the facial features of the eventual bit face. The precisely machined interior surface512is milled and dressed to form the proper contours of the finished bit. Various types of cutters (not shown), known to persons having ordinary skill in the art, are placed along the locations of the cutting edges of the bit and are optionally placed along the gage area of the bit. These cutters are placed during the bit fabrication process or after the bit has been fabricated via brazing or other methods known to persons having ordinary skill in the art.

Once the mold510is fabricated, displacements are placed at least partially within the mold volume514. The displacements are fabricated from clay, sand, graphite, ceramic, or other known suitable materials. These displacements include the center stalk520and the at least one nozzle displacement522. The center stalk520is positioned substantially within the center of the mold510and suspended a desired distance from the bottom of the mold's interior surface512. The nozzle displacements522are positioned within the mold110and extend from the center stalk520to the bottom of the mold's interior surface512. The center stalk520and the nozzle displacements522are later removed from the eventual drill bit casting so that drilling fluid (not shown) flows though the center of the finished bit during the drill bit's operation.

The blank400, which has been previously described above, is centrally suspended at least partially within the mold510and around the center stalk520. The blank400is positioned a predetermined distance down in the mold510. The distance between the outer surface of the blank400and the interior surface512of the mold510is about twelve millimeters or more so that potential cracking of the mold510is reduced during the casting process. However, this distance is varied in other exemplary embodiments depending upon the strength of the mold510or the method and/or equipment used in fabricating the casting.

Once the displacements520,522and the blank400have been positioned within the mold510, tungsten carbide powder530is loaded into the mold110so that it fills a portion of the mold volume514that is around the bottom portion416of the blank400, between the inner surfaces of the blank400and the outer surfaces of the center stalk520, and between the nozzle displacements522. Shoulder powder534is loaded on top of the tungsten carbide powder530in an area located at both the area outside of the blank400and the area between the blank400and the center stalk520. The shoulder powder534is made of tungsten powder or other known suitable material. This shoulder powder534acts to blend the casting to the blank400and is machinable. Once the tungsten carbide powder530and the shoulder powder534are loaded into the mold510, the mold510is vibrated, in some exemplary embodiments, to improve the compaction of the tungsten carbide powder530and the shoulder powder534. Although the mold510is vibrated after the tungsten carbide powder530and the shoulder powder534are loaded into the mold510, the vibration of the mold510is done as an intermediate step before, during, and/or after the shoulder powder534is loaded on top of the tungsten carbide powder530. Although tungsten carbide material530is used in certain exemplary embodiments, other suitable materials known to persons having ordinary skill in the art is used in alternative exemplary embodiments.

The funnel540is a graphite cylinder that forms a funnel volume544therein. The funnel540is coupled to the top portion of the mold510. A recess542is formed at the interior edge of the funnel540, which facilitates the funnel540coupling to the upper portion of the mold510. In some exemplary embodiments, the inside diameter of the mold510is similar to the inside diameter of the funnel540once the funnel540and the mold510are coupled together.

The binder pot550is a cylinder having a base556with an opening558located at the base556, which extends through the base556. The binder pot550also forms a binder pot volume554therein for holding a binder material560. The binder pot550is coupled to the top portion of the funnel540via a recess152that is formed at the exterior edge of the binder pot550. This recess552facilitates the binder pot550coupling to the upper portion of the funnel540. Once the downhole tool casting assembly500has been assembled, a predetermined amount of binder material560is loaded into the binder pot volume554. The typical binder material560is a copper alloy or other suitable known material. Although one example has been provided for setting up the downhole tool casting assembly500, other examples having greater, fewer, or different components are used to form the downhole tool casting assembly500. For instance, the mold510and the funnel540are combined into a single component in some exemplary embodiments.

The downhole tool casting assembly500is placed within a furnace (not shown) or other heating structure. The binder material560melts and flows into the tungsten carbide powder530through the opening558of the binder pot550. In the furnace, the molten binder material560infiltrates the tungsten carbide powder530to fill the interparticle space formed between adjacent particles of tungsten carbide powder530. During this process, a substantial amount of binder material560is used so that it fills at least a substantial portion of the funnel volume544. This excess binder material560in the funnel volume544supplies a downward force on the tungsten carbide powder530and the shoulder powder534. Once the binder material560completely infiltrates the tungsten carbide powder530, the downhole tool casting assembly500is pulled from the furnace and is controllably cooled. Upon cooling, the binder material560solidifies and cements the particles of tungsten carbide powder530together into a coherent integral mass710(FIG. 7). The binder material560also bonds this coherent integral mass710(FIG. 7) to the blank400thereby forming a bonding zone590, which is formed at least at a chamfered zone area598of the blank400and a central zone area599of the blank400, according to certain exemplary embodiments. The coherent integral mass710(FIG. 7) and the blank400collectively form the matrix body bit600(FIG. 6), a portion of which is shown inFIGS. 6 and 7. Once cooled, the mold510is broken away from the casting. The casting then undergoes finishing steps which are known to persons of ordinary skill in the art, including the addition of a threaded connection (not shown) coupled to the top portion414of the blank400. Although the matrix body bit600(FIG. 6) has been described to be formed using the process and equipment described above, the process and/or the equipment can be varied to still form the matrix body bit600(FIG. 6).

FIG. 6shows a magnified cross-sectional view of the bonding zone590located at the chamfered zone area598(FIG. 5) within the downhole tool in accordance with the exemplary embodiment.FIG. 7shows a magnified cross-sectional view of the bonding zone590located at the central zone area599(FIG. 5) within the downhole tool in accordance with the exemplary embodiment. Referring toFIGS. 6 and 7, the blank400includes the internal blank component410and the metal coating420, which is applied onto the surface of the internal blank component410. The coherent integral mass710is bonded to the blank400via the bonding zone590that is formed along the surface of the blank400and which extends inwardly into the interior portion of the blank400. According to some exemplary embodiments, the metal coating420is thinly applied onto the internal blank component410so that a portion of the binder material560diffuses into both the metal coating420and the internal blank component410and reacts with the metal coating420and a portion of the internal blank component410to form this bonding zone590. The bonding zone590includes intermetallic compounds690, which are similar to the intermetallic compounds290(FIG. 2). According toFIG. 6, the bonding zone590is formed having a thickness615ranging from about five μm to less than sixty-five μm in the chamfered zone area598(FIG. 5). In another exemplary embodiment, the bonding zone590is formed having a thickness615ranging from about five μm to less than fifty μm in the chamfered zone area598(FIG. 5). In yet another exemplary embodiment, the bonding zone590is formed having a thickness615ranging from about five μm to less than thirty μm in the chamfered zone area598(FIG. 5). According toFIG. 7, the bonding zone590is formed having a thickness715ranging from about two μm to less than about ten μm in the central zone area599(FIG. 5). In another exemplary embodiment, the bonding zone590is formed having a thickness715ranging from about two μm to less than eight μm in the central zone area599(FIG. 5). In yet another exemplary embodiment, the bonding zone590is formed having a thickness715ranging from about two μm to less than six μm in the central zone area599(FIG. 5). The thicknesses615,715and/or volumes of the bonding zone590are dependent upon the exposure time, the temperature, and the thickness of the metal coating420that is applied onto the internal blank component410. As previously mentioned, the metal coating420reduces the migration of binder material560from the coherent integral mass710into the blank400during the fabrication process.

FIG. 8shows a magnified cross-sectional view of the bonding zone590located at the chamfered zone area598(FIG. 5) within the downhole tool in accordance with another exemplary embodiment.FIG. 9shows a magnified cross-sectional view of the bonding zone590located at the central zone area599(FIG. 5) within the downhole tool in accordance with another exemplary embodiment. Referring toFIGS. 8 and 9, the blank400includes the internal blank component410and the metal coating420, which is applied onto the surface of the internal blank component410. The coherent integral mass710is bonded to the blank400via the bonding zone590that is formed along the surface of the blank400and which extends inwardly into the interior portion of the blank400. According to some exemplary embodiments, the metal coating420is applied onto the internal blank component410such that a portion of the binder material560diffuses into a portion of the metal coating420but not into the internal blank component410. The diffused binder material560reacts with a portion of the metal coating420to form this bonding zone590. The bonding zone590includes intermetallic compounds690, which are similar to the intermetallic compounds290(FIG. 2). According toFIG. 8, the bonding zone590is formed having a thickness815ranging from about five μm to less than sixty-five μm in the chamfered zone area598(FIG. 5). In another exemplary embodiment, the bonding zone590is formed having a thickness815ranging from about five μm to less than fifty μm in the chamfered zone area598(FIG. 5). In yet another exemplary embodiment, the bonding zone590is formed having a thickness815ranging from about five μm to less than thirty μm in the chamfered zone area598(FIG. 5). According toFIG. 9, the bonding zone590is formed having a thickness915ranging from about two μm to less than about ten μm in the central zone area599(FIG. 5). In another exemplary embodiment, the bonding zone590is formed having a thickness915ranging from about two μm to less than eight μm in the central zone area599(FIG. 5). In yet another exemplary embodiment, the bonding zone590is formed having a thickness915ranging from about two μm to less than six μm in the central zone area599(FIG. 5). The thicknesses815,915and/or volumes of the bonding zone590are dependent upon the exposure time, the temperature, and the thickness of the metal coating420that is applied onto the internal blank component410. As previously mentioned, the metal coating420reduces the migration of binder material560from the coherent integral mass710into the blank400during the fabrication process.