A logistical and technical challenge
A tropical climate with lots of rain, high humidity and vast remote areas barely accessible by road characterize Bahia, a state in northeast of Brazil that is about the size of France. Conducting an oilfield development campaign in this setting was clearly a logistical and technical challenge, particularly if a large number of deep wells were to be drilled. Numerous wells means rigging up a drilling rig, rigging it down again and then moving it to the next location. This normally takes time, which is expensive in the oil business and is better spent drilling.
For the Bahia region, Brazilian energy company Petrobras campaign therefore required two rigs that could be rigged up and down as quickly as possible without having to order specialized heavy crane equipment and without paying extra money for the crane to reach a remote spot in the jungle. Herrenknecht Vertical in Schwanau, Germany developed and delivered two tailor-made rigs of the TI-350 Slingshot type to the region of Alagoinhas, some 100 kilometers north of Salvador de Bahia, the state’s capital.
Quick and easy rig-up and rig-down
The rigs‘ innovative feature is the self-erecting slingshot system and telescopic mast. They are assembled at the drilling location in a compact, horizontal position. The substructure and mast are then raised using an integrated hydraulic cylinder lifting system. Raising of the complete rig to the required working level can be done without additional equipment such as heavy cranes.
Also, the telescopic mast works with hydraulic cylinders. Instead of hoisting the drill string and the top drive with ropes as with conventional drawworks, a Herrenknecht Vertical developed hydraulic cylinder hoisting system with a doubles stroke of 22 meters is used. Joystick control in the driller’s cabin ensures swift and precise operations in the borehole. The advantage of the hydraulic system is its uniform way of working from the first millimeter – whereas when rope drawworks are used, a delayed and uneven reaction is unavoidable as the rope expands under tensile load.
Manual pipe handling, which has been the norm for decades, is now carried out by the hydraulic horizontal-to-vertical pipe handler. The pipes are provided at a defined hand-over position by the horizontal catwalk in front of the rig, from where the hydraulic gripper arm transports the pipe as doubles to the vertical well center position at the touch of a button from the control panel in the driller’s cabin. Subsequent steps, such as making up the connection at the rig floor and at the top drive, are also largely automated and can be monitored from the control cabin. Since this means that no-one needs to work in hazardous areas, the risk of LTIs is minimized.