Bent sub

To deflect the bit in the desired direction a bent sub (w th typically 1° to 2° bend) which can be oriented from surface is inserted in the string just above the motor. 

The gravity tool face angle, or angle between the plane defined by the borehole axis and the vertical and the plane defined by the borehole axis and the BHA axis below the bent sub, can also be calculated. Figure 4-226 shows the gravity tool face angle. It is readily calculated using the equation... 

An interesting problem that can be solved with the steering tool or the MWD measurements is the trajectory forecast when drilling ahead with a given bent sub (constant angle), and a given tool-face angle. 

After drilling the mud motor length with a given tool face angle and a given bent sub angle, what is the borehole deviation and orientation likely to be at the mud motor depth ... 

Geosteering is usually done with a mud motor. A mud motor with bent sub allows changing of orientation and inclination without pulling the drillstring out. Steering is done by rotating it a small angle. 

Bent sub Sub used on top of a downhole motor to give a nonstraight bottom assembly. One of the connecting threads is machined at an angle to the axis of the body of the sub. 

Hydraulically operated bent sub A deflection sub that is activated by hydraulic pressure of the drilling fluid. 

Application of a deflecting tool (e.g., downhole motor with a bent sub) requires determining the orientation of the tool so that the hole takes the desired course. There are three effects to consider when setting a deflection tool ... 

T. Tarnai. We don t deal with dynamics it was a static calculation. We considered elastic bars, which are usually in sub-stress. We found the equilibrium configuration, under which the structure has a certain shape, and in this case we can find only the coordinates of the proper nodes. We found the planes of the curved members which are circular or curved, and whether or not you have twisted or bent elements. In this case the member forms a helix too, but we can make no further comment at this stage. 

MacDowell, A.A. et al., Progress towards sub-micron hard x-ray imaging using elliptically bent mirrors, in X-ray Microfocusing Applications and Techniques, McNulty, I., Ed., vol. 3449, 1998, p. 137, SPIE Proceedings, Bellingham, WA. 

If one has differentiated information about elementary particles like protons, neutrons and electrons which connect to questions of chemical bonding, misconceptions can arise which mix bent water molecules or the 11-protons nucleus of a sodium atom with macroscopic characteristics of matter (see also Sect. 4.3). Since electrons are not ordinary basic particles of matter in the sense of atoms, ions and molecules, but are recognized more as charged clouds, orbital or through the particle-wave duality, the mixing of macroscopic and sub-microscopic characteristic properties should be avoided more carefully. 

In very special cases, the square-pyramidal ligand arrangements in these butterfly-type sub-units are distorted towards trigonal-bipyramidal coordination sites. Within the picture of the bent bond, this transition would disrupt the metal-metal bond and should be directly attributable to electronic variations within the ligand spheres of the metal atoms. 

Murthy, H. N. S. Sadashiva, B. K. Observation of a transition from non-switchable B7 mesophase to an antiferroelectric sub-phase in strongly polar bent-core compounds. J. Mater. Chem. 2003,13, 2863-2869. 

The /2-type semiconductor bands are bent upward at the polymer-SC interface, as shown. 0/R is the electronic level corresponding to the 0/R redox potential rest state (a) laser excitation (b) charge transport in polymer (i.e., polymer switching) (c). The processes occurring in chronological order are laser excitation of the SC (sub-nanosecond) (b) charge transfer to polymer (subnanosecond) (b) oxidation-reduction of initial polymer layers (subnanosecond risetime falltime from ca. 10 ns to microseconds) (c) charge transport in bulk polymer (slow process) (c). 

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