The present application discloses the use of the pre-stressed steel strand in, the procedure of multi-angle core drilling. Using the properties of high strength and toughness of pre-stressed steel strand material, the core internal pipe is pushed inside the drill rod without deformation and damage. The rolling wheel is designed to rapidly take out and put back the pre-stressed steel strand to finish the extracting of the core, without taking out and putting back the drill rod. Without altering the original structure of the drilling machine, the technology of 360 core drilling is realized. Problems of tedious and arduous operations and a low efficiency in multi-angle drilling are resolved completely. The use of the pre-stressed steel strand not only can significantly improve the drilling-in efficiency, but also is beneficial to guarantee the quality of the rock mineral coring, reduce the cost of drilling, lower the labor intensity notably.

The present application discloses the use of the pre-stressed steel strand in, the procedure of multi-angle core drilling. Using the properties of high strength and toughness of pre-stressed steel strand material, the core internal pipe is pushed inside the drill rod without deformation and damage. The rolling wheel is designed to rapidly take out and put back the pre-stressed steel strand to finish the extracting of the core, without taking out and putting back the drill rod. Without altering the original structure of the drilling machine, the technology of 360 core drilling is realized. Problems of tedious and arduous operations and a low efficiency in multi-angle drilling are resolved completely. The use of the pre-stressed steel strand not only can significantly improve the drilling-in efficiency, but also is beneficial to guarantee the quality of the rock mineral coring, reduce the cost of drilling, lower the labor intensity notably.

A drill unit for forming a column in ground which includes an outer drill and a concentric inner drill, where attached to the outer drill there is at least one drill tooth which includes a first face, a second face and a base face wherein: the first face and the second face are immediately adjacent one another and are coterminous at a first edge and a second edge; the base face is the face closest to, or coterminous with, the first terminal end; all faces, except the base face, are independently coterminous with the base face; and extend away from the base face in the same direction; at least part of the at least one drill tooth extends away from the first terminal end to terminate at the second edge; the second edge is the edge of the at least one tooth that is most longitudinally distant from the first terminal end; the first face further includes a first alpha edge, where the first alpha edge is an edge of the first face opposite the first edge; a line joining the first edge and the first alpha edge, where the first face and the base face are coterminous, a first face alignment line, is at an angle of to a perpendicular extending from the first outside surface; the second face further includes a second alpha edge which is an edge of the second face opposite the first edge; and a line joining the first edge and the second alpha edge, where the second face and the base face are coterminous, a second face alignment line, is at an angle of to a tangent on the first outside surface; such that, when in use forming the column, the first edge is configured to be a leading edge.

A drill unit for forming a column in ground which includes an outer drill and a concentric inner drill, where attached to the outer drill there is at least one drill tooth which includes a first face, a second face and a base face wherein: the first face and the second face are immediately adjacent one another and are coterminous at a first edge and a second edge; the base face is the face closest to, or coterminous with, the first terminal end; all faces, except the base face, are independently coterminous with the base face; and extend away from the base face in the same direction; at least part of the at least one drill tooth extends away from the first terminal end to terminate at the second edge; the second edge is the edge of the at least one tooth that is most longitudinally distant from the first terminal end; the first face further includes a first alpha edge, where the first alpha edge is an edge of the first face opposite the first edge; a line joining the first edge and the first alpha edge, where the first face and the base face are coterminous, a first face alignment line, is at an angle of to a perpendicular extending from the first outside surface; the second face further includes a second alpha edge which is an edge of the second face opposite the first edge; and a line joining the first edge and the second alpha edge, where the second face and the base face are coterminous, a second face alignment line, is at an angle of to a tangent on the first outside surface; such that, when in use forming the column, the first edge is configured to be a leading edge.

The drilling tool includes a circular-cylindrical casing pipe; an annular ring bit disposed at a leading end of the casing pipe so as to be coaxial with the casing pipe and rotatable around a central axis of the casing pipe; and a pilot bit inserted into the casing pipe and has a leading end disposed at an inner peripheral part of the ring bit. The ring bit is engaged with the pilot bit in a rotational direction, and thereby is rotatable integrally with the pilot bit and is locked to the leading end of the pilot bit. Drilling tips are mounted on the leading ends of the pilot bit and the ring bit, and first drilling tips at an outermost periphery of the pilot bit and second drilling tips at an innermost periphery of the ring bit overlap each other in a rotational trajectory around the central axis.

The drilling tool includes a circular-cylindrical casing pipe; an annular ring bit disposed at a leading end of the casing pipe so as to be coaxial with the casing pipe and rotatable around a central axis of the casing pipe; and a pilot bit inserted into the casing pipe and has a leading end disposed at an inner peripheral part of the ring bit. The ring bit is engaged with the pilot bit in a rotational direction, and thereby is rotatable integrally with the pilot bit and is locked to the leading end of the pilot bit. Drilling tips are mounted on the leading ends of the pilot bit and the ring bit, and first drilling tips at an outermost periphery of the pilot bit and second drilling tips at an innermost periphery of the ring bit overlap each other in a rotational trajectory around the central axis.

The present invention relates to a collapsible drill bit for use in formation drilling and a method of formation drilling. The drill bit includes a main body having a first cutting diameter and includes a front end with a cutting face supporting one or more cutting elements and a rear end configured to operatively connect to a drill string. The drill bit also includes a retractable portion between the front end and the rear end, the retractable portion including at least one cutting face supporting one or more cutting elements, the retractable portion configured to move between an expanded position in which the retractable portion has a second cutting diameter and a collapsed position in which the retractable portion has a diameter less than or equal to the first cutting diameter. Wherein the retractable portion is caused to move into the collapsed position upon an application of a sufficient force.

The present invention relates to a collapsible drill bit for use in formation drilling and a method of formation drilling. The drill bit includes a main body having a first cutting diameter and includes a front end with a cutting face supporting one or more cutting elements and a rear end configured to operatively connect to a drill string. The drill bit also includes a retractable portion between the front end and the rear end, the retractable portion including at least one cutting face supporting one or more cutting elements, the retractable portion configured to move between an expanded position in which the retractable portion has a second cutting diameter and a collapsed position in which the retractable portion has a diameter less than or equal to the first cutting diameter. Wherein the retractable portion is caused to move into the collapsed position upon an application of a sufficient force.

A bottom hole assembly for a casing-while-drilling operation utilizes a tethered float valve to retrieve the bottom hole assembly after the casing string has been positioned at a desired wellbore depth.

A bottom hole assembly for a casing-while-drilling operation utilizes a tethered float valve to retrieve the bottom hole assembly after the casing string has been positioned at a desired wellbore depth.