Drilling of Oil and Gas Wells

Drilling an oil well in the system of impact on the rocks is divided into mechanical and non-mechanical. In the case of a mechanical method the actions are performed with a tool, which acts directly on the rock and breaks it. During a non-mechanical method, direct contact with the source rock is eliminated, and its destruction takes place.

Drilling of oil and gas wells with non-mechanical methods (thermal, hydraulic, electrophysical) is not currently practiced.

Mechanical methods used in wells drilling

Shock Method

As a result of drilling of oil and gas wells, there is a breaking of rocks by a Bit (1) hanging on a rope. It is thrown through the block, which is mounted on the mast (5), with the use of a shock rod (2), rope rocket, hanging on a rope (3-4).

Thus, the reciprocating mechanism provides drilling machine (6). Rope elongation occurs respectively deepening of the well, a turning of the bit ensures cylindricity.

Drilling tools are regularly removed from the well and a bailer that looks like an elongated bucket with a valve at the bottom is immediately lowered to clean the face of oil and gas wells of the destructed rocks. After diving into the mixture from the drilled rock particles and liquid, the valve opens, filling the bailer with this mixture. The valve closes when the bailer is lifted, extracting the mixture up. The casing is lowered in the well, the length of the casing increases respectively with the deepening of the bottom-hole. These actions are aimed at preventing the borehole walls from collapse.

Rotation Method

The method of rotation drilling is not accompanied by attacks on the rock, but a destructive effect of rotating drilling bit, which is under the influence of the axial load. Thereby, the torque is transmitted directly to the bit or drill pipe string through a surface of rotation (the rotor). The same effect may occur with a downhole motor, which is mounted above the bit in three ways:

• turbodrill, hydraulic turbine driven in rotation by means of a flushing liquid injected during the drilling in oil and gas wells;
• electric drill, with motor cable, protected against the ingress of liquid, powering of the motor during the drilling of oil and gas wells is supplied from the surface;
• Screw motor, downhole hydraulic machine using a screw mechanism for transforming the flushing fluid flow energy into mechanical energy, rotational motion for the efficient drilling of oil and gas wells.

Demolition of rocks at the bottom is characterized by two types of drilling oil and gas wells:

• full hole frilling, performed on the whole area;
• core drilling, performed exclusively on the ring for extraction of the core, which helps to produce the analysis of the composition, properties and structure of rocks and saturated rock fluids.