A drill string for rotary drilling of underground mining machines includes a first elongate drill string member and a second elongate drill string member. The first member has a main section and a male end, and the second member has a main section and a female end. The male and female ends each have respective threads to provide a thread coupling between the male and female ends, the thread coupling enabling the male end to be secured inside the female end such that the male and female ends overlap axially. A thread lead of the respective threads of the male and the female ends are greater than a diameter of the male end and the female end.

A mechanical connector, including a telescopically assembled mechanical connector, is provided with one or more sets of threads on substantially matching frustoconical surfaces of a pin and a box of the connector. Thread generatrix angles on the loaded and unloaded sides of the threads are measured to normals to the shared axes of the box and of the pin. This invention introduces mismatching of the generatrix angles along the interacting surfaces on the loaded and/or unloaded sides of the threads, which result in slight interference fit(s) along the thread surfaces. The effect is more even distribution of the bearing loads on the threads, reductions in the maximum shear loading and more uniform bending of the threads. Already good leak resistance of the connector can be additionally improved. The above modifications can be introduced to traditional connectors and to connectors designed to transfer high torsional loads.

A bottom hole assembly may include a shaft having threads, a first fastener member positioned on the shaft, the first fastener member having first fastener threads that mesh with a first portion of the threads on the shaft, and a second fastener member positioned downhole of the first fastener member on the shaft, the second fastener member having second fastener threads that mesh with a second portion of the threads on the shaft, wherein the first fastener member and the second fastener member interact with each other such that an uphole face of the first fastener threads are pressed against a downhole face of the first portion of the threads on the shaft and a downhole face of the second fastener threads are pressed against an uphole face of the second portion of the threads on the shaft.

Threaded tubular connection comprising a tubular female end extending from a main body of a first tubular member, and a tubular male end extending from a main body of a second tubular member, such that the tubular female end comprises a machined outer cylindrical surface close to the female free end having a first outer diameter and a second machined outer cylindrical surface above a threaded portion of the female end, a second outer diameter of the second outer cylindrical surface being bigger than the first outer diameter.

A threaded tubular connection includes a tubular female end extending from a main body of a first tubular member, and a tubular male end extending from a main body of a second tubular member, such that the tubular male end includes a first machined inner surface close to the male free end and a second machined inner cylindrical surface above a threaded portion of the male end such that a second inner diameter of the second machined inner cylindrical surface is smaller than a first inner diameter of the first machined inner surface.

A threaded connection between adjacent drill string components comprises a threaded female connection end adapted to receive a correspondingly threaded male connection end, the two ends each having first and second portions of different tapers. Tubular members, drill string tools and other drill string components comprising the female or male ends described herein are also provided.

The present disclosure provides a portable seafloor drill rig for a submersible for multi-point core drilling, including a power head, a reduction gear box, an emergency jettison device, a drilling tool, and a temperature and pressure-retaining device. a water supply connector and the power head are arrange on a top plate of the reduction gear box. An output shaft of the power head is connected to an input shaft of the reduction gear box, and an output shaft of the reduction gear box is provided with a central hole, which is in communication with a water inlet hole of the water supply connector. An output shaft of the reduction gear box is connected to the emergency jettison device, and the temperature and pressure-retaining device can perform temperature and pressure-retaining storage of the core drilled by the drilling tool.

Provided is means for connecting oil well pipes together with a compact/simple structure and the strength that significantly exceeds the limits of prior art even without the flange, etc. An oil well pipe coupling structure includes a first oil well pipe and a second oil well pipe, the external thread portion has a first external thread portion, a substantially tapered second external thread portion, and a third external thread, the internal thread portion has a first internal thread portion, a substantially tapered second internal thread portion, and a third internal thread portion the first external thread portion is screwed to the first internal thread portion, the second external thread portion is screwed to the second internal thread portion, the third external thread portion is screwed to the third internal thread portion, and the first oil well pipe and the second oil well pipe are coupled together.

An alignment sub may include a first sub body part rotatably coupled to a second sub body part. The first sub body part and second sub body part may be respectively non-rotatably coupled to a first wellbore tool and a second wellbore tool. A lock screw switchable between an unlocked state and a locked state may fix an angular position of the first sub body part relative to an angular position of the second sub body part when the lock screw is in the locked state.

Connectors may be used for connecting case settings in high temperature wells, such as geothermal or oil wells. The connector is simple in design and is able to take up thermal expansion due to temperature change when high temperature media starts to flow through the casings and when the well needs to be cooled down for maintenance.