Downhole tool apparatus and method of limiting packer element extrusion

A downhole apparatus for use in a well bore comprising:

• a) a mandrel made of a non-metallic material and having an axial centerline;
• b) a collar spacer ring made of a non-metallic material being secured to the mandrel;
• c) a first plurality of upper slip segments proximate to the spacer ring and encircling a portion of the mandrel, the upper slip segments being restrained in an initial position by a retaining means, the upper slip segments being made of a non-metallic material forming an upper slip means for grippingly engaging the wellbore when set into position, each slip segment having a planar bearing surface;
• d) a non-metallic upper slip wedge encircling and slidable along a portion of the mandrel, the slip wedge located adjacent to the upper slip segments, the upper slip wedge further having a plurality of planar bearing surfaces inclined with respect to the axial centerline of the mandrel being complementary to and for coacting with the planar bearing surfaces of respective slip segments;
• e) a first plurality of non-metallic packer element retaining shoe segments encircling a portion of the mandrel and being positioned and restrained by a retaining means so as to be proximate to the upper slip wedge, the shoe segments having a surface configured to accommodate an end portion of a packer element assembly and further having a cavity for accommodating at least a portion of a shoe segment to shoe segment gap-spanning structural member;
• f) a packer element assembly comprising at least one packer element having a first end portion proximate to and accommodatable by the internal surface of the first shoe segments, the packer assembly generally encircling a portion of the mandrel;
• g) a second plurality of non-metallic packer element retaining shoe segments being positioned and restrained by a retaining means so as to be proximate to an opposite end of the packer assembly and encircling a portion of the mandrel, the second plurality of shoe elements having a surface configured to accommodate the opposite end of the packer element assembly and further having a cavity for accommodating at least a portion of a shoe segment to shoe segment gap-spanning structural member;
• h) a lower non-metallic slip wedge encircling and slidable along a portion of the mandrel, the lower slip wedge located adjacent to a second plurality of lower slip segments, the lower slip wedge further having a plurality of planar bearing surfaces inclined with respect to the axial centerline of the mandrel being complementary to and for coacting with the planar bearing surfaces of respective slip segments;
• i) a second plurality of slip segments proximate to a second end portion of at least one packer element and encircling a portion of the mandrel, the second plurality of slip segments made of a non-metallic material and being initially restrained by a retaining means to form a lower slip means for grippingly engaging the wellbore when set into position, each lower slip segment having a planar bearing surface;
• and
• j) an end most terminating portion to the downhole tool, the terminating portion being proximate to the lower slip segments and being secured to the mandrel;
• wherein the shoe segment gap-spanning structural member serves to limit the extrusion of the packer element proximate to the associated retaining shoe.

A method of limiting the extrusion of packing elements installed about a mandrel of a downhole tool upon the tool being set in a wellbore, the method comprising:

• a) providing at least one packer element retaining shoe having a plurality of shoe segments, each having a packer element face in annular relationship with the mandrel,
• b) providing at least one cavity in at least one of the shoe segments;
• c) providing and installing at least one shoe segment to shoe segment gap-spanning structural member that is sized and configured to be initially accommodated by at least one of the cavities provided in at least one of the shoe segments, the structural member further being sized and configured to allow for the member to substantially bridge a gap that develops between adjacent shoe segments upon expansion of the packer element;
• d) providing means for retaining the shoe segments and the shoe segment gap-spanning structural members in an initial position about the mandrel;
• and
• e) expanding the packer element radially outward so as to cause a portion of the packer element to be forced against the shoe segment gap-spanning structural member and the packer face of the associated shoe segment, which in turn causes adjacent segmented shoe segments to form a gap therebetween and in which the gap-spanning structural member limits extrusion of the packer element proximate to the retaining shoes.