A subterranean formation is drilled using a drill bit of a bottomhole assembly to form a wellbore in the subterranean formation. The bottomhole assembly includes a storage chamber and sidewall coring bits. While the bottomhole assembly is disposed within the wellbore, a sidewall of the wellbore is cut into using the sidewall coring bits to obtain sidewall core samples. While cutting into the sidewall of the wellbore using the sidewall coring bits, fluid is circulated through the wellbore. The sidewall core samples are received within the storage chamber.

A method of determining the depth of a sidewall core sample taken from a borehole relative to a reference log of the borehole. The method includes obtaining a reference log recorded on a reference log depth scale and a borehole image log recorded on a borehole image log depth scale of a portion of the borehole from which the sidewall core sample has been taken. The method further includes generating a calibrated borehole image log from the borehole image log and the reference log and identifying a candidate sidewall core image artifact in the calibrated borehole image log. The method also includes assigning a confidence value for the candidate sidewall core image artifact based on a characteristic of the candidate sidewall core image artifact, and determining, using the confidence value, a probability that the sidewall core sample was collected at a certain depth on the reference log depth scale.

A method of determining the depth of a sidewall core sample taken from a borehole relative to a reference log of the borehole. The method includes obtaining a reference log recorded on a reference log depth scale and a borehole image log recorded on a borehole image log depth scale of a portion of the borehole from which the sidewall core sample has been taken. The method further includes generating a calibrated borehole image log from the borehole image log and the reference log and identifying a candidate sidewall core image artifact in the calibrated borehole image log. The method also includes assigning a confidence value for the candidate sidewall core image artifact based on a characteristic of the candidate sidewall core image artifact, and determining, using the confidence value, a probability that the sidewall core sample was collected at a certain depth on the reference log depth scale.

A long-distance core drilling method suitable for a horizontal geological core drilling rig. (1) An active drill rod is connected to a drill rod, which is connected to a wireline-coring outer-tube drilling tool. (2) A steel-pipe string is connected to a fishing device, and the fishing device is connected to a spearhead on a core tube, which is placed to a designated position through a pipe-feeding mechanism. (3) A washing pump is started. (4) A core drilling is carried out. (5) A core is pulled out. (6) The steel-pipe string and the fishing device are reconnected. (7) The core tube is salvaged. (8) The core tube and drill pipe are replaced. (9) A hole is swept. (10) Steps (1)-(9) are repeated until the hole is drilled to a designated depth. (11) The core tube and the wireline-coring outer-tube drilling tool are recovered.

A long-distance core drilling method suitable for a horizontal geological core drilling rig. (1) An active drill rod is connected to a drill rod, which is connected to a wireline-coring outer-tube drilling tool. (2) A steel-pipe string is connected to a fishing device, and the fishing device is connected to a spearhead on a core tube, which is placed to a designated position through a pipe-feeding mechanism. (3) A washing pump is started. (4) A core drilling is carried out. (5) A core is pulled out. (6) The steel-pipe string and the fishing device are reconnected. (7) The core tube is salvaged. (8) The core tube and drill pipe are replaced. (9) A hole is swept. (10) Steps (1)-(9) are repeated until the hole is drilled to a designated depth. (11) The core tube and the wireline-coring outer-tube drilling tool are recovered.

A method (60) of determining core orientation of a core sample (12) cut from the ground by a drill rig (10) having a drill string and a drill bit (20) coupled to a downhole end of the drill string. Drilling data (Cn, Rn) is continuously acquired while the drill rig (10) is operating to cut and retrieve the core sample (12). The drilling data is a combination of core orientation data Cn and rig operational data Rn, where the rig operational data is constituted by either one or both of: (a) near bit rig data Nn; and, (b) at surface rig data Sn. The drilling data is analyzed for a specific pattern of rig operational data Rn indicative of the core sample being broken from ground by operation of the drill rig (10). On detection of the specific pattern, the orientation of the core sample prior to being broken from the ground is the acquired core orientation data Cn coinciding with that specific pattern of rig operational data Rn.

A method (60) of determining core orientation of a core sample (12) cut from the ground by a drill rig (10) having a drill string and a drill bit (20) coupled to a downhole end of the drill string. Drilling data (Cn, Rn) is continuously acquired while the drill rig (10) is operating to cut and retrieve the core sample (12). The drilling data is a combination of core orientation data Cn and rig operational data Rn, where the rig operational data is constituted by either one or both of: (a) near bit rig data Nn; and, (b) at surface rig data Sn. The drilling data is analyzed for a specific pattern of rig operational data Rn indicative of the core sample being broken from ground by operation of the drill rig (10). On detection of the specific pattern, the orientation of the core sample prior to being broken from the ground is the acquired core orientation data Cn coinciding with that specific pattern of rig operational data Rn.

A long-distance core drilling method suitable for a horizontal geological core drilling rig. (1) An active drill rod is connected to a drill rod, which is connected to a wireline-coring outer-tube drilling tool. (2) A steel-pipe string is connected to a fishing device, and the fishing device is connected to a spearhead on a core tube, which is placed to a designated position through a pipe-feeding mechanism. (3) A washing pump is started. (4) A core drilling is carried out. (5) A core is pulled out. (6) The steel-pipe string and the fishing device are reconnected. (7) The core tube is salvaged. (8) The core tube and drill pipe are replaced. (9) A hole is swept. (10) Steps (1)-(9) are repeated until the hole is drilled to a designated depth. (11) The core tube and the wireline-coring outer-tube drilling tool are recovered.

A long-distance core drilling method suitable for a horizontal geological core drilling rig. (1) An active drill rod is connected to a drill rod, which is connected to a wireline-coring outer-tube drilling tool. (2) A steel-pipe string is connected to a fishing device, and the fishing device is connected to a spearhead on a core tube, which is placed to a designated position through a pipe-feeding mechanism. (3) A washing pump is started. (4) A core drilling is carried out. (5) A core is pulled out. (6) The steel-pipe string and the fishing device are reconnected. (7) The core tube is salvaged. (8) The core tube and drill pipe are replaced. (9) A hole is swept. (10) Steps (1)-(9) are repeated until the hole is drilled to a designated depth. (11) The core tube and the wireline-coring outer-tube drilling tool are recovered.

A subterranean formation is drilled using a drill bit of a bottomhole assembly to form a wellbore in the subterranean formation. The bottomhole assembly includes a storage chamber and sidewall coring bits. While the bottomhole assembly is disposed within the wellbore, a sidewall of the wellbore is cut into using the sidewall coring bits to obtain sidewall core samples. While cutting into the sidewall of the wellbore using the sidewall coring bits, fluid is circulated through the wellbore. The sidewall core samples are received within the storage chamber.