Coring tools including core sample flap catcher and related methods

A core sample catcher for a coring tool includes at least one flap catcher member movably coupled to an inner barrel of the coring tool. The at least one flap catcher member is configured to move between a first position and a second position. A passageway extending through the inner barrel is at least substantially un-occluded by the at least one flap catcher member in the first position and at least partially occluded by the at least one flap catcher member in the second position. The core sample catcher also includes a piston member located and configured to retain the at least one flap catcher member in the first position. The piston member is sized and configured to release the at least one flap catcher member as the piston is forced upward within the inner barrel by the core sample. Components are provided and assembled to form core sample catchers.

FIELD

The disclosure relates generally to core sample catchers used in conjunction with coring tools for obtaining core samples from earth formations within a wellbore, and to methods of fabricating and using such core sample catchers and coring tools.

BACKGROUND

When evaluating whether a given earth formation contains valuable materials, such as hydrocarbons, a core sample from the earth formation may be procured using a bottom-hole assembly (BHA) often referred to in the art as a “coring tool.” A coring tool generally includes a core bit, which may be a hollow earth-boring rotary drill bit having a longitudinal aperture extending through the center thereof. As a result, when the core bit drills through the formation, a generally cylindrical core sample is formed within the longitudinal aperture extending through the center of the core bit. A substantially non-rotating inner barrel is positioned longitudinally within an outer tubular member, commonly tanned a “core barrel” of the coring tool above the core bit, and is configured and positioned to receive the generally cylindrical core sample therein as the core sample is formed by the core bit as the core bit drills into the earth formation and the coring tool lowers around the core sample.

Once the core bit has drilled a core sample of desirable length, a core catcher is used to fracture the core sample and separate the core sample from the formation near the core bit. The core catcher is typically a collet structure that allows the core sample to pass through the collet into the inner barrel of the coring tool, but that tightens around the core sample when the coring tool is pulled upward away from the bottom of the wellbore to prevent the core sample from backing out from the coring tool through the core catcher. In other words, when the coring tool is pulled upward away from the bottom of the wellbore, the core catcher grips the core sample and generates tensile forces within the core sample below the core catcher that fracture the core sample, allowing it to be retained within the inner barrel and returned to the surface for analysis.

Some formations comprise loose or unconsolidated formation material. For example, some formations may comprise unconsolidated sand. In such formations, a collet type core catcher may not retain all of the core sample within the inner barrel, as the loose formation material may simply fall out of the coring tool through the opening of the core catcher. Other configurations of core catchers have been developed in an effort to retain such unconsolidated formation material within the inner barrel of the coring tool. For example, flap catchers have been developed that include one or more flap members that move between a first open position and a second closed position after a core sample has been formed and received within the inner barrel. The flap catcher substantially covers the central opening in the core bit, which forms the core sample as the core bit drills the formation material around the core sample, and prevents or at least hinders unconsolidated material from falling out from the coring tool as the coring tool is returned to the surface for analysis of the core sample.

BRIEF SUMMARY

In some embodiments, the present disclosure includes a core sample catcher for use with a coring tool for obtaining a core sample from a subterranean formation. The coring tool includes an inner barrel configured to receive a core sample, and the core sample catcher includes at least one flap catcher member movably coupled to the inner barrel of the coring tool. The at least one flap catcher member is configured to move between a first position and a second position, and a passageway extending through the inner barrel is at least substantially un-occluded by the at least one flap catcher member in the first position and at least partially occluded by the at least one flap catcher member in the second position. A piston member is located and configured to retain the at least one flap catcher member in the first position, and the piston member is sized and configured to be forced upward within the inner barrel by the core sample and release the retention of the at least one flap catcher member in the first position by the piston member as the core sample is received within the inner barrel.

In additional embodiments, the present disclosure includes coring tools that include such core sample catchers. For example, a coring tool for use in obtaining a core sample from an earth formation within a wellbore may include a core bit, an outer tubular member coupled to the core bit, and an inner barrel pivotally secured within the outer tubular member above the core bit. The inner barrel is configured to receive a formation core sample therein as the core sample is formed by the core bit as the core bit drills through an earth formation. A core sample catcher as described herein may be coupled to the inner barrel proximate the core bit.

In still other embodiments, the present disclosure includes methods of fabricating such core sample catchers. For example, a method of forming a core sample catcher for use with a coring tool for obtaining a core sample from a subterranean formation may include movably coupling at least one flap catcher member to an inner barrel such that the at least one flap catcher member is configured to move between a first position and a second position. A passageway extending through the inner barrel is at least substantially un-occluded by the at least one flap catcher member in the first position and at least partially occluded by the at least one flap catcher member in the second position. The method may also include disposing a piston member within the coring tool. The piston member retains the at least one flap catcher member in the first position. The piston member may be sized and configured to be forced upward within the inner barrel by the core sample and release the retention of the at least one flap catcher member in the first position by the piston member as the core sample is received within the inner barrel.

DETAILED DESCRIPTION

The illustrations presented herein are not meant to be actual views of any particular core sample catcher, coring tool, or component thereof, but are merely idealized representations employed to describe illustrative embodiments. The figures are not necessarily drawn to scale.

As used herein, the relative term “upward” means and includes in a direction from a core bit toward a surface of a coring operation. Similarly, the relative term “downward” means and includes in a direction from a surface of a coring operation toward a core bit. Likewise, the term “higher” may indicate a position closer to the surface of the coring operation relative to the core bit, and “lower” may indicate a position closer to the core bit relative to the surface of the coring operation.

FIG. 1is a longitudinal cross-sectional view of a coring tool100that includes a core sample catcher102and a core bit104. The coring tool100has a coupling member105at an upper, proximal end106, and the core bit104is disposed at the lower, distal end108of the coring tool100. The coupling member105at the upper, proximal end106is configured to couple the coring tool100to another component of a drill string (not shown), and may be, or include a part of, a swivel member110.

The swivel member110includes an outer tubular member112that is fixedly coupled to the coupling member105, such that outer tubular member112rotates in unison with rotation of the coupling member105caused by rotation of the drill string. The swivel member110also includes an inner assembly114supported within the outer tubular member112by bearings such that the inner assembly114is rotationally decoupled from the outer tubular member112. Thus, the inner assembly114may remain substantially rotationally stationary during rotation of the drill string, coupling member105, and the outer tubular member112.

The core bit104at the lower distal end108of the coring tool100may comprise any type or configuration of core bit104. The core bit104is coupled to the outer tubular member112of the swivel member110by an outer tube116comprising one or more tubular segments coupled end-to-end, such that rotation of the outer tubular member112of the swivel member110(by rotation of the drill string) causes rotation of the core bit104.

As the core bit104is rotated in a coring operation, a generally cylindrical core sample of the formation being drilled is formed within a central opening in the core bit104. As the core bit104drills through the formation and forms the core sample from uncut formation material within the center of the core bit104, the core sample advances into and relatively upward through the core bit104by way of the central opening and into an inner barrel118disposed within the outer tube116. The inner barrel118also may comprise one or more tubular segments coupled end-to-end.

During normal operation, the coring operation will continue until a core sample of desirable length has been formed by the core bit104and received within the inner barrel118. The core sample catcher102is configured to catch or retain the core sample received in the inner barrel118and prevent the core sample from backing out from the coring tool100, and is used to fracture the core sample and separate the core sample from the formation near the core bit104. As discussed in further detail below, the core sample catcher102may include a flap catcher that is useful for retaining loose or unconsolidated formation material within the inner barrel118.

FIG. 2is an enlarged view of the core sample catcher102of the coring tool100ofFIG. 1separate from other components of the coring tool100. The core sample catcher102includes a generally tubular shoe120, and a flap catcher tube126coupled to the shoe120. The shoe120has a lower end122and an upper end124. The flap catcher tube126has a lower end128and an upper end130. The lower end128of the flap catcher tube126may be coupled to the upper end124of the shoe120using threads, for example. The upper end130of the flap catcher tube126may be configured for coupling to a lower end of the inner barrel118of the coring tool100(FIG. 1). While the shoe120and the flap catcher tube126are described above and shown in the figures as two individual parts coupled with the inner barrel118, those skilled in the art will appreciate that the shoe120and the flap catcher tube126may comprise one integral part, i.e., a unitary structure. Furthermore, in some embodiments, the shoe120, the flap catcher tube126, and the inner barrel118may similarly comprise a unitary structure. Thus, the shoe120and the flap catcher tube126may be characterized as the inner barrel118or as portions of the inner barrel118.

At least one flap catcher member132is disposed within the flap catcher tube126. Although only one flap catcher member132is illustrated in the embodiment ofFIGS. 2 and 3, the core sample catcher102may include two or more such flap catcher members132in additional embodiments. The flap catcher member132is movably coupled to a wall of the flap catcher tube126and configured to move between a first open position (shown inFIG. 2) and a second closed position (shown inFIG. 3). The flap catcher member132may be movably coupled to the wall of the flap catcher tube126using, for example, a hinge136. As a non-limiting example, the hinge136may include a pinned connection, as shown inFIG. 2. In other embodiments, the hinge136may include an elastic member coupled to or integrally formed with the flap catcher member132.

As shown inFIG. 2, a passageway140extends longitudinally through the core sample catcher102. The passageway140is at least substantially un-occluded by the flap catcher member132when the flap catcher member132is in the first open position shown inFIG. 2. The passageway140is at least partially occluded by the flap catcher member132(FIG. 3) when the flap catcher member132is in the second closed position shown inFIG. 3so as to retain core sample material within the inner barrel118(FIG. 1) of the coring tool100.

The core sample catcher102of the coring tool100may further include a spring member138that is located and configured to bias the flap catcher member132toward the second closed position ofFIG. 3. The spring member138may be disposed between the flap catcher member132and the wall of the flap catcher tube126. In some embodiments, the spring member138may comprise a leaf spring. In other embodiments, the spring member138may be a coil spring or other spring configuration. In some embodiments, the spring member138may be coupled only to the wall of the flap catcher tube126and configured to bear against the flap catcher member132. In other embodiments, the spring member138may be coupled to both the wall of the flap catcher tube126and the flap catcher member132. In yet other embodiments, the spring member138may be coupled only to the flap catcher member132, and configured to bear against the wall of the flap catcher tube126. In still other embodiments, a protrusion (not shown) may be located between the wall of the flap catcher tube126and the flap catcher member132and the flap catcher member132may be elastically bent over the protrusion when in the first position, so that it is biased towards the second position by elastic strain of the flap catcher member material.

With continued reference toFIG. 2, the core sample catcher102further includes a piston member144. The piston member144may be initially disposed within the flap catcher tube126, and may be located and configured to retain the flap catcher member132in the first open position shown inFIG. 2until a core sample of a formation is received within the coring tool100, as described in further detail below with reference toFIGS. 4 through 7. In particular, the piston member144may be sized and configured to be forced upward within the flap catcher tube126, so as to release the retention of the flap catcher member132in the first open position, by a core sample as the core sample is received within the flap catcher tube126. The piston member144may include one or more openings from its upper end to its lower end to allow the flap catcher member132to be retained in the first open position shown inFIG. 2, without occluding the fluid passageway140through the core sample catcher102. For example, the piston member144may include a central bore145extending through a central portion of the piston member144. As a result, the inner barrel118(FIG. 1) of the coring tool100may be flushed with fluid while “tripping” the coring tool100into the wellbore. In some embodiments, fluid may be actively pumped through the inner barrel118to wash formation cuttings or other foreign particulate matter out from the inner barrel118until the coring operation is started. In some embodiments, the piston member144may also include one or more apertures147that allow a fluid flowing through the central bore145to flow from the central bore145, through the one or more apertures147, and flush an exterior of the piston member144. The central bore145in the piston member144may be sized and configured to create minimal resistance to a flow of fluid through the inner barrel118. For example, the flow resistance of the piston member144may be low enough that flow of fluid through the piston member144during normal operation does not cause undesired movement of the piston member144. Retaining the flap catcher member132in the first position by the piston member144allows flushing the inner barrel118with fluid before the coring operation starts without requiring openings in the flap catcher member132. Openings in the flap catcher member132are undesirable because core material may fall through the openings in the flap catcher member132, and part of the core sample might be lost while tripping the coring tool102out of the hole. The piston member144may also reduce the likelihood of damage to a core sample202(FIG. 5), the flap catcher member132, the hinge136, or the spring member138that may occur if the flap catcher member132were in an initially closed position (FIG. 3) and were forced open by the entry of a core sample (e.g., core sample202inFIG. 5). Furthermore, forced opening of the flap catcher member132by a core sample202entering the inner barrel118may also increase the likelihood of the core sample202jamming within the inner barrel118.

As shown inFIGS. 2 and 3, the flap catcher member132and the piston member144may have interacting features configured to prevent the piston member144from moving in the downward direction through the shoe120. For example, such interacting features may comprise a recess146in an outer side surface of the piston member144, and a complementary projection148on the flap catcher member132that extends at least partially into the recess146, as shown inFIG. 2. The recess146and the projection148may have shapes that are sized, located, and otherwise configured to allow the projection148of the flap catcher member132to slide out from the recess146in the flap catcher tube126responsive to longitudinally upward movement of the piston member144within the flap catcher tube126, and to prevent the projection148of the flap catcher member132from sliding out from the recess146in the flap catcher tube126responsive to longitudinally downward movement of the piston member144within the flap catcher tube126.

For example, the recess146may extend into the wall of the piston member144at an acute angle to the longitudinal axis of the fluid passageway140extending through the core sample catcher102. The complementary projection148of the flap catcher member132also may be oriented at substantially the same acute angle to the longitudinal axis of the fluid passageway140. The orientation of the acute angle may be such that downward movement of the piston member144is precluded, while upward movement of the piston member144is enabled.

A recess150also may be formed in the inner surface of the wall of the flap catcher tube126, and the recess150may be sized and located to allow the flap catcher member132to move into the recess150as the piston member144slides upwardly within the flap catcher tube126. The recess150may extend circumferentially around the inner surface of the wall of the flap catcher tube126. A central axis of the recess150may be coaxial with a longitudinal axis of the inner barrel118, or the central axis of the recess150may be offset with respect to the longitudinal axis of the inner barrel118. Some embodiments of the core sample catcher102may not include any recess150. In other embodiments, the flap catcher tube126may include multiple recesses.

A float sub housing a float valve (i.e., a back pressure valve) preventing drilling fluid from backflowing upwardly through the coring tool100, may be connected to the coring tool100or the bottom-hole assembly (BHA) above the coring tool100to prevent the piston member144from moving in the upward direction within the coring tool100until the piston member144is moved upwardly by a core sample entering the core sample catcher102.

In some embodiments, the core sample catcher102may further include a core catcher152, e.g., a collet catcher or a spring catcher. The core catcher152may be configured to allow a core sample to pass through the core catcher152, through the flap catcher tube126, and into the inner barrel118of the coring tool100. The core catcher152may also be configured to tighten around the core sample when the coring tool100is pulled upward away from the bottom of the wellbore to prevent the core sample from backing out from the coring tool100through the core catcher152. Thus, the core catcher152grips the core sample and generates tensile forces within the core sample below the core catcher152that fracture the core sample when the coring tool100is pulled upward away from the bottom of the wellbore. The portion of the core sample within the coring tool100then may be retained within the inner barrel118and returned to the surface for analysis.

As shown inFIGS. 2 and 3, the core catcher152may be disposed within the shoe120. The core catcher152may have a tapered outer side surface154, and the shoe120may have a complementary tapered inner side surface156disposed adjacent the tapered outer side surface154of the core catcher152. The tapered outer side surface154and the tapered inner side surface156may be disposed at an acute angle to a longitudinal axis of the fluid passageway140, and the acute angle may be oriented such that, as the core catcher152is forced downwardly within the shoe120or the shoe120is forced upwardly with respect to the core catcher152, the interaction between the tapered outer side surface154of the core catcher152and the tapered inner side surface156of the shoe120generates stress and corresponding strain within the core catcher152in the radially inward direction, such that any core sample within the core catcher152is squeezed by the core catcher152. Grooves158may be formed on inner and/or outer surfaces of the core catcher152, to enhance the compressive strain of the core catcher152and the grip of the core catcher152on any core sample within the core catcher152when the core catcher152is in a state of radially inward compressive strain. The inner diameter of the core catcher152may be smaller than an outer diameter of a core sample (e.g., core sample202inFIG. 5) cut by the core bit104(FIG. 1) so that interference between the core sample202cut by the core bit104and the core catcher152ensures that the tapered outer side surface154of the core catcher152is seated securely against the tapered inner side surface156of the shoe120when the coring tool is removed from the borehole. As a non-limiting example, the grooves158may be gaps between built-up areas of hardfacing material.

The core catcher152may abut against a radially, inwardly projecting shoulder160formed on the inner surface of the shoe120that prevents the core catcher152from moving in the upward direction within the shoe120beyond the shoulder160. The piston member144may be disposed at least partly inside the core catcher152before the core starts to enter and pass through the core catcher152. Interference between the piston member144and the core catcher152when the piston member144is disposed within the core catcher152may create stress and a corresponding strain that increases the inside diameter of the core catcher152. Increasing the inside diameter of the core catcher152in this manner may enable the core sample202(FIG. 5) to enter the inside diameter of the core catcher152without colliding with the core catcher152. As the core sample202pushes the piston member144upward out of the core catcher152, the strain may be relieved, and the core catcher152may constrict around the core sample202. Interference and friction between the core catcher152and the piston member144may prevent the piston from unintended movement in response to fluid flow.

FIGS. 4 through 7are simplified depictions of the coring tool100in operation. As shown inFIG. 4, upon commencing a coring operation in a subterranean formation200, rotation of the core bit104will result in formation of a generally cylindrical core sample202within a central opening extending through core bit104and within the shoe120of the core sample catcher102. WhileFIGS. 4 through 7show the lower end of the shoe120at the same depth as the face of the core bit104, those skilled in the art will appreciate that the lower end of the shoe120may be located at some distance above the face of the core bit104. The piston member144is disposed within the flap catcher tube126, and retains the flap catcher member132in the first open position (FIG. 2). Additionally, the projection148of the flap catcher member132is disposed within the recess146in the piston member144(as shown inFIG. 2) to prevent downward movement of the piston member144within the core sample catcher102. As shown inFIG. 4, the top of the core sample will pass through the core catcher152and impinge upon a bottom surface of the piston member144. The internal diameter of the piston member144may be smaller than an internal diameter of the core catcher152to ensure that the core sample202will bear against the lower surface of the piston member144.

Referring toFIG. 5, as the core bit104advances through the formation200, the length of the core sample202increases, and the core sample202extends a further distance into the coring tool100. In the position shown inFIG. 5, the top of the core sample202had pushed the piston member144upward within the flap catcher tube126to a position at which the flap catcher member132is disposed laterally adjacent the piston member144, but the projection148of the flap catcher member132has been forced out from the recess146in the outer surface of the piston member144. Thus, the flap catcher member132has been displaced by the piston member144into the recess150formed in the inner side surface of the flap catcher tube126so as to allow the core sample202to pass by the flap catcher member132as the core sample202is received into the coring tool100, as shown inFIG. 6. The recess150in the figures is shown to be axis symmetric and concentric with the outer surface of the flap catcher tube126. However, in other embodiments, one or more recesses which are not axis symmetric or not concentric with the outer surface of the flap catcher tube126may provide the same functionality. The spring member138(FIG. 7) may hold the flap catcher member132against the side of the core sample202as the core sample202passes by the flap catcher member132.

As shown inFIG. 7, when a core sample202of sufficient length has been received through the core sample catcher102and into the inner barrel118(FIG. 1) of the coring tool100, the coring tool100may be pulled upwardly within the wellbore. If the core is stable, (i.e., consolidated formation material) pulling upwardly on the coring tool100within the wellbore causes the core catcher152to constrict around the core sample202, generating tensile forces that will result in fracture of the core sample202proximate the core catcher152and separation of the core sample202from the formation200. The core sample202is held by the core catcher152while the coring tool100moves to the surface. However, if the core sample202is unstable (i.e., unconsolidated formation material), the core sample202may disintegrate and fall from the flap catcher tube126of the inner tube shoe120because of its higher density relative to the fluid inside the coring tool100. In this case, the flap catcher member132will be moved through the unconsolidated formation material (potentially initiated by the optional spring member138) to the closed position. The flap catcher member132serves to retain the core sample202and any loose or unconsolidated formation material within the inner barrel118(FIG. 1) while the coring tool100is returned to the surface of the formation for analysis of the core sample202.

Additional, non-limiting embodiments within the scope of this disclosure include:

A core sample catcher for use with a coring tool for obtaining a core sample from a subterranean formation, the coring tool comprising an inner barrel configured to receive a core sample, the core sample catcher comprising: at least one flap catcher member movably coupled to the inner barrel of the coring tool, the at least one flap catcher member configured to move between a first position and a second position, a passageway extending through the inner barrel being at least substantially un-occluded by the at least one flap catcher member in the first position and at least partially occluded by the at least one flap catcher member in the second position; and a piston member located and configured to retain the at least one flap catcher member in the first position, the piston member sized and configured to be forced upward within the inner barrel by the core sample and release the retention of the at least one flap catcher member in the first position by the piston member as the core sample is received within the inner barrel.

The core sample catcher of Embodiment 1, wherein the piston member comprises a central bore disposed in the passageway of the coring tool.

The core sample catcher of Embodiment 2, wherein the piston member comprises one or more apertures in a wall of the piston to allow at least a portion of a drilling fluid flowing through the central bore to flush an exterior surface of the piston member.

The core sample catcher of any one of Embodiments 1 through 3, further comprising a spring member configured to bias the at least one flap catcher member toward the second position.

The core sample catcher of Embodiment 4, wherein the spring member comprises a portion of the flap catcher member comprising a resilient material.

The core sample catcher of any one of Embodiments 1 through 5, further comprising a core catcher disposed inside the inner barrel.

The core sample catcher of Embodiment 6, wherein at least a portion of the piston member is disposed at least partly within a portion of the core catcher prior to beginning a coring operation.

The core sample catcher of any one of Embodiments 1 through 7, wherein the at least one flap catcher member and the piston member have interacting features configured to prevent the piston member from moving in a downward direction.

A coring tool for use in obtaining a core sample from an earth formation within a wellbore, comprising: a core bit; an outer tubular member coupled to the core bit and an inner barrel pivotally secured within the outer tubular member above the core bit, the inner barrel configured to receive a formation core sample therein as the core sample is formed by the core bit as the core bit drills through an earth formation; and a core sample catcher coupled to the inner barrel proximate the lower end of the inner barrel, the core sample catcher comprising: at least one flap catcher member movably coupled to the inner barrel, the at least one flap catcher member configured to move between a first position and a second position, a passageway extending through the inner barrel being at least substantially un-occluded by the at least one flap catcher member in the first position and at least partially occluded by the at least one flap catcher member in the second position; and a piston member located and configured to retain the at least one flap catcher member in the first position, the piston member sized and configured to be forced upward within the inner barrel by the core sample and release the retention of the at least one flap catcher member in the first position by the piston member as the core sample is received within the inner barrel.

The coring tool of Embodiment 9, wherein the piston member comprises a central bore disposed in the passageway of the coring tool.

The coring tool of Embodiment 10, wherein the piston member comprises one or more apertures in a wall of the piston to allow at least a portion of a drilling fluid flowing through the central bore to flush an exterior surface of the piston member.

The coring tool of Embodiment 10 or Embodiment 11, further comprising a spring member configured to bias the at least one flap catcher member toward the second position.

The coring tool of Embodiment 12, wherein the spring member comprises a portion of the flap catcher member comprising a resilient material.

The coring tool of any one of Embodiments 9 through 13, wherein the core sample catcher further comprises a core catcher disposed inside the inner barrel.

The coring tool of Embodiment 14, wherein the piston member is disposed at least partly within a portion of the core catcher prior to beginning a coring operation.

The coring tool of any one of Embodiments 9 through 15, wherein the at least one flap catcher member and the piston member have interacting features configured to prevent the piston member from moving downward through the inner barrel.

A method of forming a core sample catcher for use with a coring tool for obtaining a core sample from a subterranean formation, the method comprising: movably coupling at least one flap catcher member to an inner barrel such that the at least one flap catcher member is configured to move between a first position and a second position, a passageway extending through the inner barrel being at least substantially un-occluded by the at least one flap catcher member in the first position and at least partially occluded by the at least one flap catcher member in the second position; and disposing a piston member within the coring tool, to retain the at least one flap catcher member in the first position using the piston member, the piston member sized and configured to be forced upward within the inner barrel by the core sample and release the retention of the at least one flap catcher member in the first position by the piston member as the core sample is received within the inner barrel.

The method of Embodiment 17, further comprising providing a core catcher within the inner barrel.

The method of Embodiment 18, further comprising disposing the piston member at least partly inside the core catcher.

The method of Embodiment 19, wherein disposing the piston member at least partly inside the core catcher comprises elastically increasing an inside diameter of the core catcher by interference between the piston member and the inside diameter of the core catcher.

While certain illustrative embodiments have been described in connection with the figures, those of ordinary skill in the art will recognize and appreciate that the scope of this disclosure is not limited to those embodiments explicitly shown and described herein. Rather, many additions, deletions, and modifications to the embodiments described herein may be made to produce embodiments within the scope of this disclosure, such as those hereinafter claimed, including legal equivalents. In addition, features from one disclosed embodiment may be combined with features of another disclosed embodiment while still being within the scope of this disclosure, as contemplated by the inventors.