- Industry: Oil & gas
- Number of terms: 8814
- Number of blossaries: 0
- Company Profile:
To establish circulation of drilling fluids after a period of static conditions. Circulation may resume after a short break, such as taking a survey or making a mousehole connection, or after a prolonged interruption, such as after a round trip. The operation is of more concern to drillers and well planners with longer static intervals, since immobile drilling fluid tends to become less fluid and more gelatinous or semisolid with time.
Industry:Oil & gas
To enlarge a wellbore. Reaming may be necessary for several reasons. Perhaps the most common reason for reaming a section of a hole is that the hole was not drilled as large as it should have been at the outset. This can occur when a bit has been worn down from its original size, but might not be discovered until the bit is tripped out of the hole, and some undergauge hole has been drilled. Last, some plastic formations may slowly flow into the wellbore over time, requiring the reaming operation to maintain the original hole size.
Industry:Oil & gas
To enlarge a wellbore past its original drilled size. Underreaming is sometimes done for safety or efficiency reasons. Some well planners believe it is safer to drill unknown shallow formations with a small-diameter bit, and if no gas is encountered, to then enlarge the pilot hole. An underreaming operation may also be done if a small additional amount of annular space is desired, as might be the case in running a liner if surge pressures were problematic.
Industry:Oil & gas
To drill with a mud motor rotating the bit downhole without rotating the drillstring from the surface. This operation is conducted when the bottomhole assembly has been fitted with a bent sub or a bent housing mud motor, or both, for directional drilling. Sliding is the predominant method to build and control or correct hole angle in modern directional drilling operations. Directional drilling is conceptually simple: Point the bit in the desired direction. This pointing is accomplished through the bent sub, which has a small angle offset from the axis of the drillstring, and a measurement device to determine the direction of offset. Without turning the drillstring, the bit is rotated with a mud motor, and drills in the direction it points. With steerable motors, when the desired wellbore direction is attained, the entire drillstring is rotated and drills straight rather than at an angle. By controlling the amount of hole drilled in the sliding versus the rotating mode, the wellbore trajectory can be controlled precisely.
Industry:Oil & gas
To drill a secondary wellbore away from an original wellbore. A sidetracking operation may be done intentionally or may occur accidentally. Intentional sidetracks might bypass an unusable section of the original wellbore or explore a geologic feature nearby. In the bypass case, the secondary wellbore is usually drilled substantially parallel to the original well, which may be inaccessible due to an irretrievable fish, junk in the hole, or a collapsed wellbore.
Industry:Oil & gas
To disperse a substance into a colloidal form or to disperse a clay in water to form a colloidal suspension.
Industry:Oil & gas
To deepen the wellbore by way of collecting a cylindrical sample of rock. A core bit is used to accomplish this, in conjunction with a core barrel and core catcher. The bit is usually a drag bit fitted with either PDC or natural diamond cutting structures, but the core bit is unusual in that it has a hole in its center. This allows the bit to drill around a central cylinder of rock, which is taken in through the bit and into the core barrel. The core barrel itself may be thought of as a special storage chamber for holding the rock core. The core catcher serves to grip the bottom of the core and, as tension is applied to the drillstring, the rock under the core breaks away from the undrilled formation below it. The core catcher also retains the core so that it does not fall out the bottom of the drillstring, which is open in the middle at that point.
Industry:Oil & gas
To alternately raise and lower the drillstring, casing string or liner in the wellbore. Reciprocation is usually limited to 30 to 60 ft (9 to 18 m) of vertical travel in the derrick. The purpose of reciprocating the drillstring is usually to clean cuttings and other debris from the wellbore. Reciprocating the strings can improve the chances of a good cement job in casing or liners.
Industry:Oil & gas
To connect pipe together and lower the connected length into the borehole in a controlled fashion. The pipe lengths are usually screwed together either with rotary-shouldered connections for the drillstring, or threaded and coupled connections for casing, liners and most tubing.
Industry:Oil & gas
