Anchor Structure and Downhole Plugging Apparatus

Abstract

An anchor structure is disclosed; the anchor structure is set on a mandrel of a downhole plugging apparatus. The anchor structure comprises (a) a clamping device, (b) a plurality of slips and (c) a conical slip holder, wherein the slips are connected to a conical face of the conical slip holder, and (d) a containing space between the clamping device and the slips; the anchor structure further comprises (e) a stroke pressure compensating device which is set within the containing space and can be compressed to provide pressure for the slips, wherein the containing space is designed to be able to accommodate whole or part of the stroke pressure compensating device in the situation that the slips are anchored into a wellbore wall and the clamping device is in contact with the conical slip holder. The containing space would prevent the stroke pressure compensation device from being damaged or extruded completely, and preclude the clamping device from contacting the slips directly when the slips retract.

What is claimed is: 
     
         1 . An anchor structure provide to a mandrel of a downhole plugging apparatus, comprising:
 a clamping device, a plurality of slips  4 , a conical slip holder  5  and a stroke pressure compensating device, wherein the slips are connected with a conical surface of the conical slip holder  5 , and a containing space is provided between the clamping device and the slips  4 ;   a stroke pressure compensating device in the containing space, which provide a pressure for the slips when it is compressed, wherein the containing space is designed to be able to accommodate whole or part of the stroke pressure compensating device when the slips are anchored into a wellbore wall and the clamping device is in contact with the conical slip holder  5 .   
     
     
         2 . The anchor structure from  claim 1 , further comprises: a size of the slips  4  or the conical slip holder  5  is designed to ensure that when the slips  4  are in contact with the wellbore wall, a distance between the slips  4  and the clamping device is larger than that between the conical slip holder  5  and the clamping device. 
     
     
         3 . The anchor structure from  claim 1 , further comprises:
 the containing space is formed by end faces of the clamping device which are close to the slips  4 , including faces of an external vertical surface  10  and an internal step surface  11  of the clamping device in a radial direction, and space among the vertical surface  10 , the step surface  11  and the slips  4  constitute the containing space;   a radial length of the step surface  11  is smaller than a minimum distance between the slips  4  and the mandrel  1 .   
     
     
         4 . The anchor structure from  claim 2 , further comprises:
 the containing space is formed by end faces of the clamping device which are close to the slips  4 , including faces of an external vertical surface  10  and an internal step surface  11  of the clamping device in a radial direction, and space among the vertical surface  10 , the step surface  11  and the slips  4  constitute the containing space;   a radial length of the step surface  11  is smaller than a minimum distance between the slips  4  and the mandrel  1 .   
     
     
         5 . The anchor structure from  claim 1 , wherein the stroke pressure compensating device is an elastic slip race  9 . 
     
     
         6 . The anchor structure from  claim 3 , wherein the stroke pressure compensating device is an elastic slip race  9 . 
     
     
         7 . The anchor structure from  claim 3  further comprises: the stroke pressure compensating device consists of the elastic slip race  9 , a spring  13  or a constant pressure plunger valve, wherein both ends of the spring  13  or the constant pressure plunger valve are connected to the vertical surface  10  and a elastic slip race  9 , respectively;
 when the spring  13  or the constant pressure plunger valve is compressed to its limitation, its length is less than or equal to an axial distance between the vertical surface  10  and the step surface  11 . 
 
     
     
         8 . A downhole plugging apparatus, comprising:
 a mandrel, a seal assembly which is provided on the mandrel  1 , an upper anchor assembly and a lower anchor assembly that are connected to a upper end and a lower end of the mandrel  1 , respectively;   the upper anchor assembly and the lower anchor assembly consist of anchor structures including a clamping device, a plurality of slips  4  and a conical slip holder  5 , wherein the slips  4  contact to a conical surface of the conical slip holder  5 , and a containing space is provided between the clamping device and the slips  4 ;   the anchor structures also include a stroke pressure compensating device, which is designed in a containing space and can be compressed to provide the slips with a pressure  4 ;   the containing space can accommodate whole or part of the stroke pressure compensating device when the slips  4  are anchored into a wellbore wall and the clamping device contacting with the conical slip holder  5 ;
 the clamping device of the upper anchor assembly comprises a stripper ring  3 ; 
 the clamping device of the lower anchor assembly comprises a lower lock nut  8  which is connected to thread at a bottom end of the mandrel  1 . 
   
     
     
         9 . The downhole plugging apparatus from  claim 8 , further comprising:
 size of the slips  4  and the conical slip holder  5  are designed to ensure that a distance between the slips  4  and the clamping device is larger than that between the conical slip holder  5  and the clamping device when the slips  4  are in contact with the wellbore wall.   
     
     
         10 . The downhole plugging apparatus from  claim 8 , further comprising: the containing space is formed by (1) end faces of the clamping device which are close to the slips  4 , including faces of an external vertical surface  10  and an internal step surface  11  of the clamping device in radial directions, and (2) space among the vertical surface  10 , the step surface  11  and the slips  4 ;
 a radial length of the step surface  11  is smaller than a minimum distance between the slips  4  and the mandrel  1 . 
 
     
     
         11 . The downhole plugging apparatus from  claim 9 , further comprising: the containing space is formed by (1) end faces of the clamping device which are close to the slips  4 , including faces of an external vertical surface  10  and an internal step surface  11  of the clamping device in radial directions, and (2) space among the vertical surface  10 , the step surface  11  and the slips  4 ;
 a radial length of the step surface  11  is smaller than a minimum distance between the slips  4  and the mandrel  1 . 
 
     
     
         12 . The downhole plugging apparatus from  claim 8 , further comprising: the stroke pressure compensating device could be a elastic slip race  9 , a spring  13  or a constant pressure plunger valve. 
     
     
         13 . The downhole plugging apparatus from  claim 9 , further comprising: the stroke pressure compensating device could be a elastic slip race  9 , a spring  13  or a constant pressure plunger valve. 
     
     
         14 . The downhole plugging apparatus from  claim 10 , further comprising:
 the stroke pressure compensating device consists of a spring  13 , a constant pressure plunger valve or a elastic slip race  9 , both ends of the spring or the constant pressure plunger valve are connected to the vertical surface  10  and the elastic slip race  9 , respectively;   when the spring  13  or the constant pressure plunger valve is compressed to its limitation, its length is less than or equal to an axial distance between the vertical surface  10  and the step surface  11 .