Patent Publication Number: US-7708061-B2

Title: Cup tool, cup tool cup and method of using the cup tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation-in-part of U.S. patent application Ser. No. 10/979,414 filed Nov. 2, 2004. 

   MICROFICHE APPENDIX 
   Not applicable. 
   FIELD OF THE INVENTION 
   This invention generally relates to wellhead isolation equipment and, in particular, to a cup tool for use with wellhead isolation equipment. 
   BACKGROUND OF THE INVENTION 
   Most oil and gas wells require stimulation to enhance hydrocarbon flow to make or keep them economically viable. The servicing of oil and gas wells to stimulate production requires the pumping of fluids into the well under high pressure. The fluids are generally corrosive and/or abrasive because they are laden with corrosive acids and/or abrasive proppants. 
   In order to protect components that make up the wellhead, such as the valves, tubing hanger, casing hanger, casing head and blowout preventer equipment, wellhead isolation equipment, such as a wellhead isolation tool, a casing saver or a blowout preventer protector is used during well fracturing and well stimulation procedures. The wellhead isolation equipment generally includes a high pressure mandrel that is inserted through wellhead components to isolate the wellhead components from elevated fluid pressures and from the corrosive/abrasive fluids used in the well treatment to stimulate production. A sealing mechanism, generally referred to as a sealing nipple or a cup tool, connected to a bottom of the high pressure mandrel is used to isolate the wellhead components from high fluid pressures used for well stimulation treatments. 
   Various sealing mechanisms provided for wellhead isolation equipment are described in prior art patents, such as U.S. Pat. No. 4,023,814, entitled A TREE SAVER PACKER CUP, which issued to Pitts on May 17, 1977; U.S. Pat. No. 4,111,261, entitled A WELLHEAD ISOLATION TOOL, which issued to Oliver on Sep. 5, 1978; U.S. Pat. No. 4,601,494, entitled A NIPPLE INSERT, which issued to McLeod et al. on Jul. 22, 1986; Canadian Patent 1,272,684, entitled A WELLHEAD ISOLATION TOOL NIPPLE, which issued to Sutherland-Wenger on Aug. 14, 1990; U.S. Pat. No. 5,261,487 entitled PACKOFF NIPPLE, which issued to McLeod et al. on Nov. 16, 1993; and Applicant&#39;s U.S. Pat. No. 6,918,441 entitled CUP TOOL FOR HIGH PRESSURE MANDREL, which issued Jul. 19, 2005. These sealing mechanisms include an elastomeric cup that radially expands under high fluid pressures to seal against an inside wall of a production tubing or casing. 
   The elastomeric cups are commonly bonded to a steel ring, sleeve or mandrel. In the most common construction, the two-part elastomeric cup is bonded to a steel ring that sides over a cup tool tube, also referred to as a cup tool mandrel. An O-ring seal carried by the steel ring provides a fluid seal between the two-part elastomeric cup and the cup tool tube. 
   In spite of all the known cup tools, there still exists a need for an improved cup tool that is simple and inexpensive to manufacture and provides a reliable seal at very high fluid pressures. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to provide a cup tool that is simple and inexpensive to manufacture and provides a reliable seal at very high fluid pressures. 
   The invention therefore provides a cup tool for providing a high-pressure fluid-tight seal in an annular gap between the cup tool and a casing or a tubing in a cased wellbore, the cup tool comprising: a cup tool tube having a threaded upper end for connection to a high-pressure mandrel, the cup tool tube having an outer surface over which a two-part elastomeric cup is slidably mounted for reciprocal movement from an unset position for entry of the cup tool into the wellbore to a set position in which the annular gap is obstructed by a top part of the two-part elastomeric cup to contain fluid pressure below the two-part elastomeric cup, the outer surface of the cup tool tube having a lower region of a first diameter and an upper region with a second, larger diameter and a tapered region between the upper region and the lower region; and the two-part elastomeric cup including a bottom part having a lip seal that rides against the outer surface of the cup tool tube, and seals against the tapered region of the cup tool tube to provide a high pressure seal between the cup tool tube and the bottom part of the two-part elastomeric cup when the two-part elastomeric cup is in the set position. 
   The invention further provides a cup tool for providing a high-pressure fluid-tight seal in an annular gap between the cup tool and a tubing or casing in a cased wellbore, the cup tool comprising: a cup tool tube having a threaded upper end for connection to a high-pressure mandrel, the cup tool tube having an outer surface over which a two-part elastomeric cup is slidably mounted for reciprocal movement from an unset position for entry of the cup tool into the wellbore to a set position in which the annular gap is obstructed by a top part of the two-part elastomeric cup to contain fluid pressure below the two-part elastomeric cup, the outer surface of the cup tool tube having a lower region of a first diameter and an upper region of a second, larger diameter and a tapered region between the upper region and the lower region; and a bottom part of the two-part elastomeric cup including a lip seal that rides against the outer surface of the cup tool tube and seals against the tapered region of the cup tool tube to provide a high pressure seal between the cup tool tube and the bottom part of the two-part elastomeric cup when the top part of the two-part elastomeric cup is in the set position. 
   The invention yet further provides a cup for a cup tool that provides a high-pressure fluid-tight seal in an annular gap between the cup tool and one of a cased wellbore and an inner wall of a tubing suspended in a cased wellbore, the cup comprising: a hollow generally tubular two-part elastomeric body having an outer wall and an inner wall, the outer wall of a bottom part of the two-part elastomeric body extending downwardly past the inner wall and terminating on a bottom end in an annular depending skirt, and the inner wall of the bottom part including a lip seal that rides against an outer surface of a cup tool tube, and seals against a tapered region of the cup tool tube to provide a high pressure seal between the cup tool tube and the bottom part of the two-part elastomeric cup when the two-part elastomeric cup is in a set position in which a top part of the two-part elastomeric body seals the annular gap. 
   The invention still further provides a method of sealing an annular gap between a high pressure mandrel and a casing or a tubing in a cased wellbore in order to isolate pressure-sensitive wellhead components from high-pressure fracturing and stimulation operations in a well, the method comprising: connecting a cup tool tube to a bottom end of the high-pressure mandrel, the cup tool tube having an outer surface over which a two-part elastomeric cup is slidably mounted for reciprocal movement from an unset position for entry of the cup tool into the wellbore to a set position in which the annular gap is obstructed by a top part of the two-part elastomeric cup to contain fluid pressure below the two-part elastomeric cup, the outer surface of the cup tool tube having a lower region of a first diameter and an upper region of a second, larger diameter and a tapered region between the upper region and the lower region; sliding the top part and a bottom part of a two-part elastomeric cup over the cup tool tube, the bottom part including a lip seal that rides against the outer surface of the cup tool tube, and seals against the tapered region of the cup tool tube to provide a high pressure seal between the cup tool tube and the bottom part of the two-part elastomeric cup when the two-part elastomeric cup is in the set position; connecting a bullnose to a bottom end of the cup tool tube; inserting the cup tool into the casing or the tubing in the cased wellbore; and injecting high pressure fluids through the high pressure mandrel and the cup tool into the wellbore to force the two-part elastomeric cup upwardly and the top part against a shoulder at a top of the cup tool tube, thereby forcing the lip seal against the tapered region, while forcing the top part of the two-part elastomeric cup into the set position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, in which: 
       FIG. 1  is a schematic cross-sectional view of a cup tool in accordance with one embodiment of the invention prior to setting an two-part elastomeric cup of the cup tool; 
       FIG. 2  is a schematic cross-sectional view of the embodiment shown in  FIG. 1  subsequent to setting the elastomeric cup; 
       FIG. 3  is a schematic cross-sectional view of a cup tool in accordance with a second embodiment of the invention prior to setting the elastomeric cup; 
       FIG. 4  is a schematic cross-sectional view of the embodiment shown in  FIG. 3  subsequent to setting the elastomeric cup; 
       FIG. 5  is a schematic cross-sectional view of a cup tool in accordance with a third embodiment of the invention prior to setting the elastomeric cup; 
       FIG. 6  is a schematic cross-sectional view of the embodiment shown in  FIG. 5  subsequent to setting the elastomeric cup; 
       FIG. 7  is a schematic cross-sectional view of a cup tool in accordance with a fourth embodiment of the invention prior to setting the elastomeric cup; 
       FIG. 8  is a schematic cross-sectional view of the embodiment shown in  FIG. 7  subsequent to setting the elastomeric cup; 
       FIG. 9  is a schematic cross-sectional view of a cup tool in accordance with a fifth embodiment of the invention prior to setting an two-part elastomeric cup of the cup tool; 
       FIG. 10  is a schematic cross-sectional view of the embodiment shown in  FIG. 9  subsequent to setting the elastomeric cup; 
       FIG. 11  is a schematic cross-sectional view of a cup tool in accordance with a sixth embodiment of the invention prior to setting the elastomeric cup; 
       FIG. 12  is a schematic cross-sectional view of the embodiment shown in  FIG. 11  subsequent to setting the elastomeric cup; 
       FIG. 13  is a schematic cross-sectional view of a cup tool in accordance with a seventh embodiment of the invention prior to setting the elastomeric cup; 
       FIG. 14  is a schematic cross-sectional view of the embodiment shown in  FIG. 13  subsequent to setting the elastomeric cup; 
       FIG. 15  is a schematic cross-sectional view of a cup tool in accordance with and eighth embodiment of the invention prior to setting the elastomeric cup; and 
       FIG. 16  is a schematic cross-sectional view of the embodiment shown in  FIG. 15  subsequent to setting the elastomeric cup. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In general, as will be explained below, the invention provides a cup tool for providing a high-pressure fluid seal in an annular gap between a high-pressure mandrel and a casing or a production tubing in a wellbore. The cup tool includes a cup tool tube having a threaded upper end for connection to the high-pressure mandrel, an elastomeric cup that is slidably received on a cup tool tube. A top end of the elastomeric cup is forced upwardly and over an annular shoulder at the top to the cup tool tube to a set position when the cup is exposed to elevated fluid pressures, thereby extruding into the annular gap to provide the high-pressure fluid seal. In the set position, a lip seal on an internal surface of the cup sealingly engages a tapered external surface of the cup tool tube to provide a high-pressure fluid-tight seal between the elastomeric cup and the cup tool tube. A bullnose, or the like, is threadedly fitted to a bottom of the cup tool tube to protect the cup while guiding the cup tool through a wellhead. 
   As shown in  FIG. 1 , a cup tool  300 , in accordance with one embodiment of the invention, includes a cup tool tube  302  (also known as a cup tool mandrel). The cup tool tube  302  includes an annular shoulder  304  at a threaded upper end for connection to the high-pressure mandrel (not shown). The cup tool tube also has an external surface with a lower portion  305  of a first diameter, an upper portion  307  of a second, larger diameter and a tapered portion  306  between the first and second regions, the utility of which will be described below. The cup tool further includes an annular abutment  308  with a radius slightly larger than that of the cup tool tube  302 . 
   The cup tool  300  connects to the high-pressure mandrel to form a lower end of a wellhead isolation tool, casing saver or blowout preventer protector for isolating pressure-sensitive wellhead components from the deleterious affects of high-pressure fracturing and stimulation fluids. In order to isolate the pressure-sensitive wellhead components, the cup tool includes an elastomeric cup  310  for sealing off an annular gap  320  between the cup tool  300  and a tubing  330 , which may be a casing in a cased wellbore or a production tubing in the wellbore. As shown in this embodiment, the elastomeric cup  310  is slidably received on the cup tool tube  302 . The elastomeric cup  310  abuts the annular abutment  308  when the cup is in an unset position for entry into the wellbore. The elastomeric cup  310  has a downwardly depending skirt portion  312  which defines an annular cavity  314  between the skirt portion  312  and the cup tool tube  302 . 
   The elastomeric cup  310  also includes a lip seal  316  that protrudes both downwardly and radially inward and rides against an inner surface of the cup tool tube  302 . The lip seal  316  seals against the tapered portion  306  of the cup tool tube  302  when the elastomeric cup  310  is forced upwardly by fluid pressure to a set position shown in  FIG. 2 . 
   As shown in  FIG. 1 , an optional gauge ring  340  is located beneath an annular shoulder  304  at a top end of the cup tool tube  302 . The gauge ring  340  can be retained on the cup tool tube by frictional or threaded engagement. The gauge ring  340  can be made of metal and machined to provide one or more right-angled steps engaged by the top end of the elastomeric cup  310  to inhibit the elastomeric cup from moving to the set position as it is stroked into the wellbore, while facilitating extrusion of the elastomeric cup  310  into the annular gap when the elastomeric cup  310  is exposed to high fluid pressures. The function of the gauge ring  340  is explained in detail in Applicants&#39; U.S. Pat. No. 6,918,441 which issued Jul. 19, 2005, the specification of which is incorporated herein by reference. 
   A bullnose  350 , or the like, is connected, by threads or other suitable connector, to a bottom end of the cup tool tube  302 . The bullnose  350  helps to guide the cup tool through the wellhead and also protects the elastomeric cup  310  during insertion of the cup tool through the wellhead. 
   In one embodiment, the elastomeric cup  310  is made of polyurethane having a Durometer of 80-100. In another embodiment the elastomeric cup  310  has a Durometer of 90-100. The elastomeric cup can be made of any elastomeric material having a durometer of 80-100, including other polymers, nitrile rubber, carbon reinforced rubbers or polymers, etc. During testing, the fluid-tight seal provided by a cup tool having a polyurethane cup has successfully contained fluid pressures of at least 22,500 psi without loss of seal or damage to the elastomeric cup  310 . Accordingly, the cup tool is simple and inexpensive to manufacture and provides a reliable high pressure fluid seal for isolating pressure-sensitive wellhead components during well fracturing and stimulation operations. The cup tool also permits well stimulation to be safely conducted at fluid pressures that approach a pressure rating of the well casing. 
     FIG. 2  illustrates the cup tool with the elastomeric seal in the set position. Fluid pressure  360  in the well causes the elastomeric cup  310  to move both upwardly and radially outwardly (due to pressurization of the annular cavity  314 ). The skirt portion  312  of the cup presses against the tubing  330  to form a seal therewith. Due to the fluid pressure  360 , the cup moves upwardly, extruding over the annular abutment  308 , until the lip seal  316  seals against the tapered portion  306  of the cup tool tube  302  and a top portion  318  of the elastomeric cup  310  is forced against the gauge ring  340 . Under elevated fluid pressures  360 , the top end  318  of the elastomeric cup  310  is extruded into the annular gap  320  between the gauge ring  340  and the tubing  330 , thus forming a high-pressure fluid-tight seal between the gauge ring  340  and the tubing  330 . 
   Three other embodiments of the invention are shown in  FIGS. 3-8 . Most of the components of these three other embodiments are identical to those described above and are not redundantly described below. 
     FIG. 3  shows a cup tool  300  in accordance with another embodiment of the invention, with the elastomeric cup  310  in the unset position. As is apparent from  FIG. 3 , the cup tool  300  does not have a gauge ring. The cup tool  300  merely has a cup tool tube  302  with an annular shoulder  304  machined to present a right-angled step to the top of the elastomeric cup  310 . 
     FIG. 4  shows the cup tool shown in  FIG. 3  after the elastomeric cup  310  is forced to the set condition. When exposed to fluid pressure  360 , the skirt portion  312  of the elastomeric cup  310  expands outwardly into sealing contact with the inner surface of the tubing  330 . The elastomeric cup  310  is forced upwardly, extruding first over the annular abutment  308  and then, if the fluid pressure  360  is sufficiently high, over the annular shoulder  304  into the annular gap  320  to form a fluid-tight seal between the cup tool and the tubing. As the elastomeric cup  310  is forced upwardly, the lip seal  316  comes into engagement with the tapered portion  306  of the cup tool tube  302 , and forms a high pressure seal therewith. Setting the elastomeric cup  310  seals the annular gap between the cup tool  300  and the tubing  330 , thus isolating the pressure-sensitive wellhead components from the affects of high-pressure fracturing and stimulation fluids in the well. 
     FIG. 5  shows a cup tool  300  in accordance with another embodiment of the invention. The cup tool  300  includes a gauge ring  340  having three right-angled steps. As was explained above, right-angled steps impede setting of the elastomeric cup  310  as is travels down through the wellhead. As shown in  FIG. 5 , the gauge ring  340  includes a first step  342 , a second step  344  and a third step  346  of increasing radius. 
     FIG. 6  shows the cup tool shown in  FIG. 5  after the elastomeric cup  310  is set. If fluid pressure  360  in the well rises above a first threshold pressure, the elastomeric cup  310  extrudes over the first step  342 . If the fluid pressure is further elevated beyond a second threshold pressure, the elastomeric cup  310  extrudes over the second step  344 . If the fluid pressure is further elevated past a third threshold pressure, the elastomeric cup  310  extrudes over the third step  346 . 
     FIG. 7  shows a cup tool  300  in accordance with yet another embodiment of the invention. The cup tool  300  has a cup tool tube  302  with an annular shoulder  304 . 
   Integrally formed with the annular shoulder  304  on the underside thereof is a plurality of square steps  370 , which include a first step  372 , a second step  374  and a third step  376 . The first, second and third steps function in the same way as the gauge rings  340  described above. 
     FIG. 8  shows the cup tool shown in  FIG. 7  after the elastomeric cup  310  is set. If fluid pressure  360  in the well rises above a first threshold pressure, the elastomeric cup  310  extrudes over the first step  372 . If the fluid pressure is elevated above a second threshold pressure, the elastomeric cup  310  extrudes over the second step  374 . If the fluid pressure is further elevated above a third threshold pressure, the elastomeric cup  310  extrudes over the third step  376 . 
   As shown in  FIG. 9 , the cup tool  300  includes a two-part elastomeric cup  303  having a bottom part  311  for providing a high-pressure seal around the cup tool tube  302  and a top part  319  for sealing off the annular gap  320  between the cup tool  300  and the tubing  330 , which as explained above may be a casing in the cased wellbore or the production tubing in the cased wellbore. As shown in this embodiment, the two-part elastomeric cup  303  is slidably received on the cup tool tube  302 . The top part  319  of the two-part elastomeric cup  303  abuts the annular abutment  308  when the two-part elastomeric cup  303  is in an unset position for entry into the wellbore. The bottom part  311  of the elastomeric cup  303  has a downwardly depending skirt portion  312  which defines an annular cavity  314  between the skirt portion  312  and the cup tool tube  302 . 
   The bottom part  311  of the two-part elastomeric cup  303  also includes a lip seal  316  that protrudes both downwardly and radially inwardly and rides against an inner surface of the cup tool tube  302 . The lip seal  316  seals against the tapered region  306  of the cup tool tube  302  when the two-part elastomeric cup  303  is forced upwardly by fluid pressure to a set position shown in  FIG. 10 . 
   In one embodiment, the two-part elastomeric cup  303  is molded as a single piece, and the top part  319  is a parted from the bottom part  311  using a lathe and a parting tool, in a manner well known in the art. It should be understood, however, that the bottom part  311  and the top part  319  could be molded separately. If the bottom part  311  and the top part  319  are molded separately, they may have somewhat different Durometers. It should be noted that the bottom part  311  has a square top edge that meets with a square bottom edge of the top part  319 . Thus the two parts  311 ,  319  are forced upwardly in unison over the cup tool tube  302  from the unset to the set position when the two-part elastomeric cup  303  is exposed to elevated fluid pressure, which may be natural well pressure and/or the fluid pressure induced by well stimulation fluid pumped down the through the cup tool tube. In one embodiment, the top part is about 1¼″ (31.8 mm) long. Experimentation has shown that the cup tool  300  performs a well if the top part  319  has a length of between about 1⅛″ (28.6 mm) and about 1⅜″ (34.9 mm). 
   As shown in  FIG. 9 , an optional gauge ring  340  is located beneath an annular shoulder  304  at a top end of the cup tool tube  302 . The gauge ring  340  can be retained on the cup tool tube by frictional or threaded engagement. The gauge ring  340  can be made of metal and machined to provide one or more right-angled steps engaged by the top part  319  of the two-part elastomeric cup  303  to inhibit the two-part elastomeric cup  303  from moving to the set position as it is stroked into the casing or tubing, while facilitating extrusion of the top part  319  into the annular gap when the two-part elastomeric cup  303  is exposed to high fluid pressures. 
   In one embodiment, the two-part elastomeric cup  303  is made of polyurethane having a Durometer of 80-100. In another embodiment each part of the two-part elastomeric cup  303  has a Durometer of 90-100. The two-part elastomeric cup  303  can be made of any elastomeric material having a durometer of 80-100, including other polymers, nitrile rubber, carbon reinforced rubbers or polymers, etc. During testing, the fluid-tight seal provided by a cup tool  300  having a polyurethane cup has successfully contained fluid pressures of at least 22,500 psi without loss of seal or damage to the two-part elastomeric cup  303 . Accordingly, the cup tool is simple and inexpensive to manufacture and provides a reliable high pressure fluid seal for isolating pressure-sensitive wellhead components during well fracturing and stimulation operations. The cup tool  300  also permits well stimulation to be safely conducted at fluid pressures that approach a pressure rating of the well casing. 
     FIG. 10  illustrates the cup tool  300  with the two-part elastomeric cup  303  in the set position. Fluid pressure  360  in the well causes the two-part elastomeric cup  303  to move upwardly and the top part  319  moves radially outwardly (due to pressurization of the annular cavity  314 ). The skirt portion  312  of the bottom part  311  presses against the casing or tubing  330  to form a seal therewith. Due to the fluid pressure  360 , the two-part elastomeric cup  303  moves upwardly, and the top part  319  extrudes over the annular abutment  308 . Meanwhile, the lip seal  316  seals against the tapered portion  306  of the cup tool tube  302  and the top part  319  of the two-part elastomeric cup  303  is forced against the gauge ring  340 . Under elevated fluid pressures  360 , the top part  319  of the two-part elastomeric cup  303  is extruded into the annular gap  320  between the gauge ring  340  and the tubing  330 , thus forming a high-pressure fluid-tight seal between the gauge ring  340  and the casing or tubing  330 . 
     FIG. 11  shows a cup tool  300  in accordance with another embodiment of the invention, with the two-part elastomeric cup  303  in the unset position. As is apparent from  FIG. 11 , the cup tool  300  does not have a gauge ring. The cup tool  300  merely has a cup tool tube  302  with an annular shoulder  304  machined to present a right-angled step to the top part  319  of the two-part elastomeric cup  303 . 
     FIG. 12  shows the cup tool shown in  FIG. 11  after the top-part  318  of the two-part elastomeric cup  303  is forced to the set condition. When exposed to fluid pressure  360 , the skirt portion  312  of the bottom part  311  of the two-part elastomeric cup  303 , which is in sealing contact with the inner surface of the casing or tubing  330 , forces the top part  319  of the two-part elastomeric cup  303  upwardly. The top part  319  extrudes first over the annular abutment  308  and then, if the fluid pressure  360  is sufficiently high, over the annular shoulder  304  into the annular gap  320  to form the fluid-tight seal between the cup tool  300  and the casing or tubing. As the two-part elastomeric cup  303  is forced upwardly, the lip seal  316  of the bottom part  311  comes into engagement with the tapered region  306  of the cup tool tube  302 , and forms a high pressure seal therewith. Setting the two-part elastomeric cup  303  seals the annular gap between the cup tool  300  and the casing or tubing  330 , thus isolating the pressure-sensitive wellhead components from the affects of high-pressure fracturing and stimulation fluids in the well. 
     FIG. 13  shows a cup tool  300  in accordance with another embodiment of the invention. The cup tool  300  includes a gauge ring  340  having three right-angled steps. As was explained above, right-angled steps impede setting of the two-part elastomeric cup  303  as is travels down through the wellhead. As shown in  FIG. 13 , the gauge ring  340  includes a first step  342 , a second step  344  and a third step  346  of increasing diameter. 
     FIG. 14  shows the cup tool shown in  FIG. 13  after the top part  319  of the two-part elastomeric cup  303  is set. If fluid pressure  360  in the well rises above a first threshold pressure, the top part  319  of the two-part elastomeric cup  303  extrudes over the first step  342 . If the fluid pressure is further elevated beyond a second threshold pressure, the top part  319  of the two-part elastomeric cup  303  extrudes over the second step  344 . If the fluid pressure is further elevated past a third threshold pressure, the top part  319  of the two-part elastomeric cup  303  extrudes over the third step  346 . 
     FIG. 15  shows a cup tool  300  in accordance with yet another embodiment of the invention. The cup tool  300  has a cup tool tube  302  with an annular shoulder  304 . Integrally formed with the annular shoulder  304  on the underside thereof is a plurality of square steps  370 , which include a first step  372 , a second step  374  and a third step  376 . The first, second and third steps function in the same way as the gauge rings  340  described above. 
     FIG. 16  shows the cup tool shown in  FIG. 15  after the top part  319  of the two-part elastomeric cup  303  is set. If fluid pressure  360  in the well rises above a first threshold pressure, the top part  319  of the two-part elastomeric cup  303  extrudes over the first step  372 . If the fluid pressure is elevated above a second threshold pressure, the top part  319  of the two-part elastomeric cup  303  extrudes over the second step  374 . If the fluid pressure is further elevated above a third threshold pressure, the top part  319  of the two-part elastomeric cup  303  extrudes over the third step  376 . 
   For certain operations, it may be desirable to install two cup tools  300  in a double cup tool configuration. In a double cup tool configuration, two cup tools are connected end-to-end, with a suitable adapter in between. The lower cup tool typically has a bullnose and acts as the primary seal while the upper cup tool connects to the high-pressure mandrel and acts as a backup seal to prevent fluid leakage if the primary seal fails. A double cup tool is disclosed is in Applicant&#39;s above-referenced United States patent. 
   The invention therefore provides a cup tool  300  with the two-part elastomeric cup  303  that is slidably received on a cup tool tube  302  without the necessity of bonding either part of the two-part elastomeric cup to metal. Accordingly, the cup tool  300  is simple and inexpensive to manufacture and maintain. Furthermore, the cup tool  300  has been successfully tested to fluid pressures exceeding 22,500 psi. 
   Modifications and improvements to the above-described embodiments of the present invention may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.