Downhole plugs having single anchoring mechanisms and methods thereof

Abstract

Downhole plugs having single anchoring mechanisms and methods thereof are disclosed. The plug comprises of inner mandrel with proximal portion and distal portion, outer assembly and one or more retaining members. The outer assembly comprises of support element, elastomeric element for sealing the gap between the plug and casing, anchoring mechanism at the distal portion for anchoring the plug to the casing and nose element. The elastomeric element is retained in a compressed state at the downhole end by the anchoring mechanism and at the up hole end by the retaining members. In some embodiments, the retaining members are snap rings that are pushed down from step portions at the proximal portion when the plug is mobilized to a set position thereby retaining the elastomeric element. In some embodiments, the retaining members are ratcheted open rings that ratchet over the proximal portion thus retaining the elastomeric element.

We claim: 
     
         1 . A downhole plug having a single anchoring mechanism, the plug thereof comprising:
 a) a substantially cylindrical hollow inner mandrel, the mandrel thereof having a proximal portion configured to be oriented up hole and a distal portion configured to be oriented downhole;   b) a substantially cylindrical hollow outer assembly being disposed circumferentially around the mandrel, the outer assembly thereof comprising a support element, an elastomeric element, an anchoring mechanism and a nose element, the support element thereof being disposed at the proximal portion, the elastomeric element being disposed between the support element and the anchoring mechanism, the elastomeric element thereof being configured for sealing a gap between the plug and a casing, the elastomeric element thereof having an up hole end contacting the support element and a downhole end contacting the anchoring mechanism, the anchoring mechanism thereof being configured for securely anchoring the plug to the casing, the anchoring mechanism further being configured for retaining the elastomeric element in a compressed state from the down hole end after the plug is mobilized to a set position and the nose element thereof engaging the distal portion; and   c) at least one of a retaining member, the retaining member being housed within the support element, the retaining member thereof being configured for being pushed in a unidirectional manner towards a downhole direction during setting of the plug, the retaining member thereof further being configured for retaining the elastomeric element in a compressed state from the up hole end by preventing the support element from backing off after the plug is mobilized to the set position.   
     
     
         2 . The plug as claimed in  claim 1 , wherein the proximal portion has a circumferential retaining step portion, wherein the retaining member is an expanding ring, the expanding ring thereof being mounted over the step portion, the expanding ring thereof being in a radially expanded state when the plug is in an unset position, at least one of the expanding ring being configured to be pushed down from the step portion to a step base when the plug is mobilized to the set position, the expanding ring that is pushed down from the step portion changing into a relaxed state over the step base thereby retaining the elastomeric element in a compressed state. 
     
     
         3 . The plug as claimed in  claim 2 , wherein the expanding rings are three in number. 
     
     
         4 . The plug as claimed in  claim 2 , wherein the expanding ring is an open ring. 
     
     
         5 . The plug as claimed in  claim 4 , wherein the open ring is a snap ring. 
     
     
         6 . The plug as claimed in  claim 1 , wherein the proximal portion has a series of circumferential retaining step portions, the proximal portion thereof having an outer diameter associated therewith, the proximal portion thereof progressively increasing in the outer diameter from the lowermost step portion to the uppermost step portion, wherein the retaining member is an expanding ring, the expanding ring thereof being mounted over the uppermost step portion, the expanding ring thereof being in a radially expanded state when the plug is in an unset position, at least one of the expanding ring configured for being pushed down from the uppermost step portion to a lower position when the plug is mobilized to the set position, the expanding ring that is pushed down from the uppermost step portion changing into a relatively relaxed state at the lower position thereby retaining the elastomeric element in a compressed state. 
     
     
         7 . The plug as claimed in  claim 6 , wherein the lower position is a step base. 
     
     
         8 . The plug as claimed in  claim 6 , wherein the expanding ring is an open ring. 
     
     
         9 . The plug as claimed in  claim 8 , wherein the open ring is a snap ring. 
     
     
         10 . The plug as claimed in  claim 1 , wherein an outer surface of the proximal portion is partially threaded with ratchet threads, wherein the retaining member is an expanding ring having ratchet threads on an inner surface, wherein the ratchet threads of the expanding ring have corresponding dimensions with the ratchet threads of the proximal portion to enable the expanding ring to ratchet over the proximal portion from an up hole direction towards the downhole direction when the plug is mobilized from an unset position to the set position thereby retaining the elastomeric element in a compressed state. 
     
     
         11 . The plug as claimed in  claim 10 , wherein the expanding ring is an open ring. 
     
     
         12 . The plug as claimed in  claim 1 , wherein the anchoring mechanism comprises of a slip system having teeth facing the downhole direction and a conical ring element, the conical ring element thereof contacting the downhole end of the elastomeric element, the slip system thereof being configured for riding over the conical ring element when the plug is mobilized into the set position thereby breaking and expanding outward followed by biting into the casing and anchoring the plug to the casing. 
     
     
         13 . The plug as claimed in  claim 1 , wherein the plug is a frac plug. 
     
     
         14 . The plug as claimed in  claim 1 , wherein the plug is substantially made of composite material. 
     
     
         15 . The plug as claimed in  claim 1 , wherein the plug has a length of about 12 inches. 
     
     
         16 . A method for isolating a well bore by using a downhole plug having a single anchoring mechanism, the method thereof comprising:
 a) providing a downhole plug, the plug thereof comprising:   a substantially cylindrical hollow inner mandrel, the mandrel thereof having a proximal portion configured to be oriented up hole and a distal portion configured to be oriented downhole;   a substantially cylindrical hollow outer assembly being disposed circumferentially around the mandrel, the outer assembly thereof comprising a support element, an elastomeric element, an anchoring mechanism and a nose element, the support element thereof being disposed at the proximal portion, the elastomeric element being disposed between the support element and the anchoring mechanism, the elastomeric element thereof being configured for sealing a gap between the plug and a casing, the elastomeric element thereof having an up hole end contacting the support element and a downhole end contacting the anchoring mechanism, the anchoring mechanism thereof being configured for securely anchoring the plug to the casing, the anchoring mechanism further being configured for retaining the elastomeric element in a compressed state from the down hole end after the plug is mobilized to a set position and the nose element thereof engaging the distal portion; and   at least one of a retaining member, the retaining member being housed within the support element, the retaining member thereof being configured for being pushed in a unidirectional manner towards a downhole direction during setting of the plug, the retaining member further being configured to retain the elastomeric element in a compressed state from the up hole end by preventing the support element from backing off after the plug is mobilized to the set position;   b) deploying the plug into a well bore to a predetermined location;   c) mobilizing the plug from an unset position to the set position, the anchoring mechanism thereof anchoring the plug to the casing, the elastomeric element thereof sealing the gap between the plug and the casing and the retaining member thereof being pushed in a unidirectional manner towards the downhole direction; and   d) releasing the plug from a setting tool, the anchoring mechanism thereof retaining the elastomeric element in a compressed state from the downhole end and the retaining member thereof retaining the elastomeric element in a compressed state from the up hole end by preventing the support element from backing off.   
     
     
         17 . The method as claimed in  claim 16 , wherein the proximal portion has a circumferential retaining step portion, wherein the retaining member is an expanding ring, the expanding ring thereof being mounted over the step portion, the expanding ring thereof being in a radially expanded state when the plug is in the unset position, at least one of the expanding ring being pushed down from the step portion to a step base when the plug is mobilized to the set position, the expanding ring that is pushed down from the step portion changing into a relaxed state over the step base thereby retaining the elastomeric element in a compressed state. 
     
     
         18 . The method as claimed in  claim 17 , wherein the expanding rings are three in number. 
     
     
         19 . The method as claimed in  claim 17 , wherein the expanding ring is an open ring. 
     
     
         20 . The method as claimed in  claim 19 , wherein the open ring is a snap ring. 
     
     
         21 . The method as claimed in  claim 16 , wherein the proximal portion has a series of circumferential retaining step portions, the proximal portion thereof having an outer diameter associated therewith, the proximal portion thereof progressively increasing in the outer diameter from the lowermost step portion to the uppermost step portion, wherein the retaining member is an expanding ring, the expanding ring thereof being mounted over the uppermost step portion, the expanding ring thereof being in a radially expanded state when the plug is in the unset position, at least one of the expanding ring being pushed down from the uppermost step portion to a lower position when the plug is mobilized to the set position, the expanding ring that is pushed down from the uppermost step portion changing into a relatively relaxed state at the lower position thereby retaining the elastomeric element in a compressed state. 
     
     
         22 . The method as claimed in  claim 21 , wherein the lower position is a step base. 
     
     
         23 . The method as claimed in  claim 21 , wherein the expanding ring is an open ring. 
     
     
         24 . The method as claimed in  claim 23 , wherein the open ring is a snap ring. 
     
     
         25 . The method as claimed in  claim 16 , wherein an outer surface of the proximal portion is partially threaded with ratchet threads, wherein the retaining member is an expanding ring having ratchet threads on an inner surface, wherein the ratchet threads of the expanding ring have corresponding dimensions with the ratchet threads of the proximal portion, the expanding ring thereof ratcheting over the proximal portion from an up hole direction towards the downhole direction when the plug is mobilized from the unset position to the set position thereby retaining the elastomeric element in a compressed state. 
     
     
         26 . The method as claimed in  claim 25 , wherein the expanding ring is an open ring. 
     
     
         27 . The method as claimed in  claim 16 , wherein the plug is a frac plug.