Drilling into presalt formations has been a long-standing issue due to the rapid changes in the diameter of the borehole during drilling operations either because of creep or wash-out dissolution.
The caliper log measures the internal diameter of the borehole.
Oriented caliper logs measure mechanically the diameter of the borehole and link it with geographical information.
The gas extraction conditions and the diameter of the borehole should first be used to determine the correct size and type of material to increase resistance.
In the compressive failure zone, the borehole casing should be thickened to resist the compressive stress, while in the shear failure zone, the key shear strata should be reamed to increase the diameter of the borehole.
Because the eccentricity of 3 mm of the down-hole tool can be regarded as being negligibly small, the sum of both the point-symmetrical data in some orientation are approximately the diameter of the borehole for that orientation.
Therefore, breakouts can be detected using the (four-arm) caliper log tool that provides two diameters of the borehole cross section (Reinecker et al. 2003).
These sizes are adopted, taking into consideration the focus distance, size of laser displacement sensor, and Japanese standards of borehole diameters.
Fig. 7 Time variations of borehole diameters relative to the initial ones for the data of each orientation in Fig. 6.
In Fig. 7, the time variations of borehole diameters relative to the initial ones, of the same data of Fig. 6, are depicted for some orientations, say N90°E (hereafter N90, and similar expressions for others), N120, N150, N180, N210, and N240.
The 3D borehole thermal resistance of coaxial GHEs with a borehole diameter of 152.4 and 203.2 mm (6 and 8 in).
