Herrenknecht Vertical designed a unique test rig based on a design brief from Shell’s international R&D center. It has been in operation since 2007 to test new drilling technologies and work processes for exploring oil and gas deposits.
In Rijswijk, the Netherlands, a specialized 250 metric tons test rig has been operating regularly since 2007. The rig, which is installed next to the Shell R&D center, is used to test new drilling technologies and work processes for exploring oil and gas deposits. This globally unique offsite test setup relieves real field operations where tests of new technology, procedures or material would usually be realized.
This rig’s location only a few meters from the engineers’ and scientists’ office windows is not its only remarkable attribute; its technical features also distinguishes it from the industry standard. Together with Shell’s drilling specialists, Herrenknecht Vertical has developed a R&D rig precisely adapted to the requirements of work in the Rijswijk R&D center. The rig’s substructure, for example, is made up of four hydraulic cylinders whose height can be varied by more than 2 meters to allow any combination of wellhead spools to be used. In addition, the rig can be moved laterally so that work can be carried out on three test wells alternately.
On June 26, 2010, Shell E&P and Herrenknecht Vertical together carried out a pull test to study the impact of a sudden loss of hook load on the rig. Caused for example through the loss of the drill pipe, this scenario is very dangerous, particularly on conventional drilling rigs with rope drawworks, since the hook and the traveling block on the ropes are propelled rapidly upwards. The loss of control over the rope drawworks and the danger of falling parts are extremely hazardous for everyone on the rig, and they can also seriously damage the equipment. This is where an important advantage of the Herrenknecht Vertical rigs comes into play. The hydraulic cylinders of the hoisting system can absorb and cushion the energy, which is released abruptly when the load breaks, preventing the impacts described. This greatly increases safety for personnel and equipment.
Vibration measurements at the top drive were carried out during normal rig operation before the start of the test. Additionally, a second measurement was made afterwards to serve as a comparison and so detect possible damage. For the pull test, the drill pipes connected to the top drive were anchored in the well and a pre-defined breakage with a pre-defined load was triggered using shear devices. During the experiment, several rig data and test parameters, such as hook load, cylinder and pump pressures, were monitored and recorded. The result: the maximum distance on the hoisting cylinders at the time of the load breakage with a load of 123 metric tons amounted to only 200 millimeters, and the rise in vibration measured was negligible.
The evaluation of the recorded data, the comparative measurement of vibrations at the top drive and the subsequent examination of the entire rig did not show any abnormality or damage, so confirming the advantages of Herrenknecht Vertical’s hydraulic rig concept.
The special design of the top drive’s axial main bearings particularly contributed to this positive result. The bearings are resiliently biased and have a cushioning effect via the drill pipe in the case of impact. This means that impacts can be compensated for, as they may occur for instance in the case of a sudden loss of hook load or when using shear devices (jarring), and the top drive is protected. On conventional drawwork rigs, the top drive needs to undergo an inspection after every use of drilling jars, which is time consuming and costly.
In addition to the dynamic pull test, the indicated hook load of the TI-250 test rig was verified, since Shell had not used the rig to full hook load capacity before. For this test, the drill pipe was anchored in the well without shear devices and the hook load was gradually increased from 150 to 250 metric tons and then maintained. Also in this test, all parameters were within the normal range. The tests carried out confirm that the TI-250 test rig meets the performance parameters indicated for normal operation with no problems, and that it can also easily cope with exceptional impacts such as a sudden loss of hook load.
However, it is not only the hydraulic hoist system, which greatly increases the work safety of Herrenknecht Vertical drilling rigs. Their high degree of automation, using hands-off technologies such as the hydraulic pipe handler, minimizes personnel requirements and considerably reduces the risk of LTIs. Further advantages of Herrenknecht Vertical hydraulic rigs are the low space requirements and noise emissions, as well as high tripping speeds and simple skidding.
In addition to the test described above, Shell’s drilling experts have gained valuable knowledge from operating the Herrenknecht Vertical rig in Rijswijk. Designed in close cooperation between Herrenknecht Vertical and Shell to meet precisely the requirements for this unique setup, the test rig produced results that otherwise may have been impossible or that would have to be generated during costly interruptions of field operations. Beyond the specific R&D setup, the rig is fully capable of all “normal” drilling operations with respect to the hoisting system and top drive installed similar to rigs in the field, except that it is stationary and installed next to the R&D center for testing under constant and repeatable conditions.
The Herrenknecht Vertical rig is one of the quietest on the market. In combination with its high safety standards, it was qualified to be placed directly in the backyard of Shell’s R&D center. This, together with the advantages in terms of the precise control of the drilling process through the hydraulic hoisting and rotary system, made the TI-250 test rig the first choice for this special application.
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