Drilling assembly and method of drilling for unstable and depleted formations

A liner assembly for drilling into an unstable formation, comprising:

• a substantially elongate annular body, wherein the elongate body includes:
• a liner portion having a bottom, and
• a shoe portion attached to the liner portion at the bottom thereof with the shoe portion having a cutter mounting portion thereof;
• cutters carried on the cutter mounting portion;
• a liner rotating mechanism for rotating the liner assembly to drill a wellbore into the unstable formation so that at least a section of the elongate body is disposed in the unstable formation after drilling with the cutters;
• and
• a drillable portion for being drilled out after the elongate body is set in the wellbore with the section of the body set in the unstable formation, the liner drillable portion including
• a shoe cutter mounting portion that is made of a drillable material, and
• relief spaces formed in the cutter mounting portion so that, when the material of the drillable cutter mounting portion is being drilled out by a drill bit, the cutters will release as the drill bit cuts through the mounting portion and reaches the relief spaces to minimize damaging contact of the drill bit with the cutters.

A liner assembly for drilling into an unstable formation, comprising:

• a liner having a substantially annular wall of a first predetermined diameter, having a central longitudinal axis, and having a bottom;
• a shoe carried by the liner at the bottom of the annular wall and having a bottom face, wherein the shoe has:
• a bottom face with an outer periphery thereof having a predetermined diameter, and
• a cutter mounting portion having
• radial blades attached on the shoe bottom face and extending generally radially outward towards the face outer periphery and from inward locations on the face that are spaced from each other, and
• gauge cutters on the blades that are carried slightly beyond the shoe face periphery to form a bore in the unstable formation having a diameter greater than the shoe face predetermined diameter;
• sets of cutting elements mounted to the shoe and extending generally radially outward along the shoe, the sets of cutting elements including:
• inner cutting elements that are spaced from each other on generally opposite sides of the longitudinal axis, and
• outer cutting elements that are mounted at positions beyond the liner wall predetermined diameter, the inner cutting elements mounted at a radially innermost position relative to the outer cutting elements, and the outer cutting elements mounted at a radially outermost position relative to the inner cutting elements;
• and
• a shoe rotating mechanism for rotating the shoe and the cutting elements carried thereon, wherein rotation of the shoe and the cutting elements drills a bore into the unstable formation having a second predetermined diameter that is greater than the first predetermined diameter so that, as the shoe advances downhole, the liner moves into the larger diameter bore to minimize bore damage into the unstable formation.

A liner assembly for drilling into an unstable formation, comprising:

• a liner having a substantially annular wall of a first predetermined diameter, having a central longitudinal axis, and having a bottom;
• a shoe carried by the liner at the bottom of the annular wall;
• sets of cutting elements mounted to the shoe and extending generally radially outward along the shoe, wherein the cutting elements are mounted at predetermined positions and orientations relative to the longitudinal axis with the predetermined positions and orientations being selected so that resultant forces from the cutting action of the cutting elements are directed towards a predetermined location on the shoe to minimize shoe vibrations and stabilize the shoe during cutting, the sets of cutting elements including
• inner cutting elements that are spaced from each other on generally opposite sides of the longitudinal axis, and
• outer cutting elements that are mounted at a radially outermost position relative to the inner cutting elements, the inner cutting elements mounted at a radially innermost position relative to the outer cutting elements, and the outer cutting elements are mounted at positions beyond the liner wall predetermined diameter;
• and
• a shoe rotating mechanism for rotating the shoe and the cutting elements carried thereon, wherein rotation of the shoe and the cutting elements drills a bore into the unstable formation having a second predetermined diameter that is greater than the first predetermined diameter so that, as the shoe advances downhole, the liner moves into the larger diameter bore to minimize bore damage into the unstable formation.

A liner assembly for drilling into an unstable formation, comprising:

• a liner having a substantially annular wall of a first predetermined diameter, having a central longitudinal axis, and having a bottom;
• a shoe carried by the liner at the bottom of the annular wall;
• sets of cutting elements mounted to the shoe and extending generally radially outward along the shoe, the sets of cutting elements including
• inner cutting elements that are spaced from each other on generally opposite sides of the longitudinal axis, and
• outer cutting elements, the inner cutting elements mounted at a radially innermost position relative to the outer cutting elements, and the outer cutting elements mounted at a radially outermost position relative to the inner cutting elements and at positions beyond the liner wall predetermined diameter;
• radial blades attached to the shoe and having sections thereof distal from the shoe on which the cutting elements are mounted with the shoe and blades thereof being formed of a drillable material for being drilled out by a drill bit after the liner portion is set with at least a section thereof in the unstable formation, and
• a shoe rotating mechanism for rotating the shoe and the cutting elements carried thereon, wherein rotation of the shoe and the cutting elements drills a bore into the unstable formation having a second predetermined diameter that is greater than the first predetermined diameter so that, as the shoe advances downhole, the liner moves into the larger diameter bore to minimize bore damage into the unstable formation.

A rotary liner assembly for drilling a bore hole into unstable formations, the rotary liner assembly comprising;

• a substantially annular liner having a longitudinal axis for being rotated in the bore hole about its longitudinal axis;
• a shoe including cutter mounting blades at the leading end of the liner aligned along the liner longitudinal axis for rotating therewith;
• cutting elements mounted on the blades for engaging the formation and cutting therein as the liner and shoe are rotated;
• and
• reliefs in the blade arms for drilling of the blade arms by a drill bit after the rotary liner assembly has drilled into the unstable formation and at least a section of the liner is set therein to advance the bore hole beyond the liner with the drill bit cutting into the blade arm reliefs to release the cutting elements from the blade arms to minimize damaging contact of the drill bit with the cutting elements.