Shock absorber for a downhole tool, and running gear for downhole surveying

Abstract

A shock absorber (24) for a downhole tool (18) is disclosed. The shock absorber (24) includes a downhole portion (32) defining a bore (34), and an uphole portion (36) configured for direct or indirect connection to the downhole tool (18). The uphole portion (36) has a stanchion (38) extending from one end and which carries a piston (40). The piston (40) is slidably engaged with the bore (34) to allow relative axial movement of the uphole portion (36) and the downhole portion (32). A first resiliently deformable member (42) is arranged between the uphole portion (36) and the downhole portion (32), and arranged to be compressed when the uphole portion (36) and downhole portion (32) move axially relative to each other in a first direction. A second resiliently deformable member (44) is arranged between an end of the bore (34) and the piston (40) to be compressed when the uphole portion (36) and downhole portion (32) move axially relative to each other in a second direction opposite to the first direction.

1 . A shock absorber for a downhole data acquisition tool configured for wireline retrieval, the shock absorber including:
 a downhole portion defining a bore;   an uphole portion configured for connection to the downhole data acquisition tool, the uphole portion having a stanchion extending from one end, the stanchion carrying a piston slidably engaged with the bore to allow relative axial movement of the uphole portion and downhole portion;   a first resiliently deformable member arranged between the uphole portion and the downhole portion to be compressed when the uphole portion and downhole portion move axially relative to each other in a first direction; and   a second resiliently deformable member arranged between an end of the bore and the piston to be compressed by the piston when the uphole portion and downhole portion move axially relative to each other in a second direction opposed to the first direction,   the downhole portion having one or more abutment surfaces arranged at a specific position along the bore to abut the piston to limit relative axial movement of the uphole portion and the downhole portion in the second direction and, as a result, limit compression of the second resiliently deformable member,   the downhole portion arranged to collide, directly or indirectly, with a static object when lowered downhole by wireline to cause the relative axial movement of the uphole portion and the downhole portion, and consequently cause compression of at least the first resiliently deformable member.   
     
     
         2 . The shock absorber of  claim 1 , wherein the one or more abutment surfaces are defined by an annular shoulder arranged to extend into the bore and at least partially surround the second resiliently deformable member. 
     
     
         3 . The shock absorber of  claim 2 , wherein the shoulder is defined by a collar mounted at a defined location along the bore. 
     
     
         4 . The shock absorber of  claim 1 , wherein the piston carries a resiliently deformable body arranged across a downhole end of the piston to allow abutting an end of the bore to be compressed. 
     
     
         5 . The shock absorber of  claim 1 , wherein the downhole portion defines at least one first flush port adjacent each end of the bore, each first flush port arranged to convey fluid from within the bore to outside of the downhole portion. 
     
     
         6 . The shock absorber of  claim 5 , wherein the downhole portion defines at least one second flush port arranged partway along the bore between the first flush ports, the, or each, second flush port arranged to convey fluid from within the bore to outside of the downhole portion. 
     
     
         7 . The shock absorber of  claim 6 , wherein the, or each, second flush port comprises a slot extending axially along the bore. 
     
     
         8 . A shock absorber for a downhole data acquisition tool configured for wireline retrieval, the shock absorber including:
 a downhole portion defining a bore;   an uphole portion configured for connection to the downhole data acquisition tool, the uphole portion having a stanchion extending from one end, the stanchion carrying a piston slidably engaged with the bore to allow relative axial movement of the uphole portion and downhole portion;   a first resiliently deformable member arranged between the uphole portion and the downhole portion to be compressed when the uphole portion and downhole portion move axially relative to each other in a first direction;   a second resiliently deformable member arranged between an end of the bore and the piston to be compressed when the uphole portion and downhole portion move axially relative to each other in a second direction opposed to the first direction   the downhole portion defines at least one first flush port adjacent each end of the bore, each first flush port arranged and dimensioned to convey fluid and particulate from within the bore to outside of the downhole portion,   the downhole portion arranged to collide, directly or indirectly, with a static object when lowered downhole by wireline to cause the relative axial movement of the uphole portion and the downhole portion, and consequently cause the piston to travel along the bore to expel fluid from at least one of the flush ports.   
     
     
         9 . The shock absorber of  claim 8 , wherein the downhole portion defines at least one second flush port arranged partway along the bore between the first flush ports, the, or each, second flush port arranged and dimensioned to convey fluid and particulate from within the bore to outside of the downhole portion. 
     
     
         10 . The shock absorber of  claim 9 , wherein the, or each, second flush port comprises a slot extending axially along the bore. 
     
     
         11 .- 23 . (canceled) 
     
     
         24 . A running gear assembly for downhole surveying, the assembly including:
 a wireline retrieval connector arranged at an uphole end of the assembly;   a downhole tool arranged downstream of the wireline retrieval connector;   a shock absorber according to  claim 1 , the shock absorber arranged downstream of the downhole tool; and   an overshot arranged at a downhole end of the assembly.   
     
     
         25 .- 26 . (canceled) 
     
     
         27 . A running gear assembly for downhole surveying, the assembly including:
 a wireline retrieval connector arranged at an uphole end of the assembly;   a downhole tool arranged downstream of the wireline retrieval connector;   a shock absorber arranged downstream of the downhole tool, the shock absorber including:
 a downhole portion defining a bore; 
 an uphole portion having a stanchion extending from one end, the stanchion carrying a piston slidably engaged with the bore to allow relative axial movement of the uphole portion and downhole portion; 
 a first resiliently deformable member arranged between the uphole portion and the downhole portion to be compressed when the uphole portion and downhole portion move axially relative to each other in a first direction; 
 a second resiliently deformable member arranged between an end of the bore and the piston to be compressed when the uphole portion and downhole portion move axially relative to each other in a second direction opposed to the first direction; 
 the downhole portion having one or more abutment surfaces arranged at a specific position along the bore to abut the piston to limit relative axial movement of the uphole portion and the downhole portion in the second direction and, as a result, limit compression of the second resiliently deformable member; 
   a coupling device arranged downstream of the shock absorber to couple two axially adjacent components of the assembly, the coupling device including an elongate body defining a longitudinal axis and having a pair of spaced engagement structures, each engagement structure configured to engage one of the axially adjacent components, the body including a frangible portion configured to fracture when force exerted on the body exceeds a defined threshold; and   an overshot arranged at a downhole end of the assembly.   
     
     
         28 . The running gear assembly of  claim 27 , including a releasable coupling assembly connected between two adjacent components of the assembly, the releasable coupling assembly including:
 a downhole body configured to connect to one of the adjacent components,   an uphole body configured to connect to the other of the adjacent components, each of the downhole body and the uphole body having a complementary engagement structure configured to releasably engage the bodies, and   a sleeve rotatably mounted on one of the downhole body and the uphole body, the sleeve configured to be manually rotatable to axially translate between a locked position to cover the engagement structures, and an unlocked position to expose the engagement structures to allow uncoupling the adjacent components.