> Making the bend in performance testing. At the Schlumberger Reservoir Completions Technology Center in Rosharon, Texas, USA, the OrientXact system was tested at bends ranging from 5° /100 ft [5° /30 m] to 10° /100 ft [10° /30 m]. Wireline- conveyed gyroscopes con rmed orientation variance at 6° or less through the bend sections, indicating that the OrientXact swivel and gun carrier designs would perform as required by Hydro in eld applications with severe doglegs.
Bending a gun string can generate signifi cant torsional stress on the assembly, risking rotation away from the desired perforation orientation (above right). To address this problem, engineers developed a series of directionally biased gun carriers designed in increments of 30° preferred- bend direction. These gun carriers can be positioned in the gun string to coincide with the trajectory of the wellbore. When biased carriers are positioned in their preferred bend direction, they assist in the orientation of the gun string. After the guns are fi red, the orientation system is designed to continue applying torque, keeping the carrier exit holes upright and preventing internal charge debris from pouring into the wellbore.
Later developments include a new gun- carrier material with no preferential bend direction. Gun carriers made from this bend-free, or nonbiased, material generate no torsional stresses. When used with other nonbiased internal
> Bend-free gun carrier material. With conventional gun carrier materials, rotational torque generated by running the perforating string into the wellbore will rotate perforating guns away from their intended orientation. New bend-free carrier designs, advances in material science and tight manufacturing tolerances allow OrientXact gun strings to bend through wellbore deviations without causing gun misalignment.
gun hardware, they can be used anywhere in the gun string, independent of the wellbore trajectory. To verify the system’s orientation, engineers designed an OCD Orientation Confirmation Device. The OCD unit records perforation orienta- tion to the nearest 0.5° . Data are downloaded when the tool reaches surface. Only two OCD units per section are required to confirm the orientation direction of all perforation tunnels. The new OrientXact system met each of the Hydro engineering and performance require- ments. Relying on novel passive, orienting weights and gun sections joined by roller-bearing swivels, the system is capable of handling high loads. It is
self-orienting, requiring weighted spacers for only the most diffi cult deviated-borehole condi- tions. A new charge design provides deep and slim perforating tunnels, and prevents excessive debris and postfiring chemical precipitation. Dirty low-side perforation tunnels are avoided through 10° /350° phasing. The OrientXact system was fi rst deployed for Hydro in the Visund fi eld in November 2001.
7. Stenhaug et al, reference 5.
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