Published: 07/08/2019
Published: 07/08/2019
A well that was geosteered offshore Sakhalin Island to explore a previously untapped part of the reservoir needed to be production logged to understand the contributions from each zone of interest. This understanding was required before the operator could consider bringing in a jackup drilling rig for future exploration drilling. However, the geosteered well profile posed challenges for logging, gradually climbing the last 3,200 m to 94° inclination at total depth of 8,000-m MD.
A train of four conventional tractors had been deployed to convey Flow Scanner horizontal and deviated well production logging system. The tractors were unable to progress past 7,200-m MD. At that depth, friction sharply increased and the tractors could not sustain the necessary head tension above 600 lbf to continue. Obtaining a complete production log across the zone of interest in the inclined section required a tractor that could consistently provide higher force.
To overcome the conveyance force limitation, Schlumberger proposed using the 21/8-in TuffTRAC extreme-performance wireline tractor. Because the TuffTRAC iX tractor is new to the market, Schlumberger conducted a full system integration test (SIT) to confirm its capabilities for multipletractor deployment with ultralong cables. The SIT was also used to quantify the maximum pull force available inside a section of 5½-in tubing from eight- and six-drive configurations. Both configurations significantly outperformed the four conventional tractors previously used, sustaining a constant 750-lbf head tension with eight drives and 600-lbf with six drives while pulling against the “hard stop” of a cable clamp in place. Peak head tensions were 2,000 lbf and 1,500 lbf, respectively. The successful SIT convincingly demonstrated to the operator that the six-drive configuration with 12 wheels could convey the production logging toolstring the complete distance in the well.
TuffTRAC iX tractors are ideal for deploying with long cables because they optimize the use of surface power. The two wheels of each tractor drive section are electromechanically driven, which achieves more than 45% conversion efficiency from the supplied electrical power. With these low power requirements, even in dry gas wells the tractor never has to be stopped to cool down.
The Flow Scanner system was successfully conveyed to 8,000-m MD by the six-drive configuration of TuffTRAC iX tractors in both shut-in and flowing conditions despite high tool friction and cable drag. High compressive forces were measured—up to 230 lbf—in pushing the toolstring uphill during flowing conditions, resulting in significant wear on the wear rings but no detrimental effect on tractor performance.
The total tractoring distance was 10,600 m during production logging and the time to reach the 8,000-m target depth was just 21 hours. This represented an efficiency gain of about 100% against the conventional tractor deployment, which saved significant rig time equating to USD 330,000.
In addition to the efficiency savings, the enabling technology of the TuffTRAC iX tractor in acquiring a complete set of high-quality data supported the operator in making informed key decisions affecting the development and exploration of the field.
Challenge: Obtain critical production log in a geosteered well to 8,000-m MD with a 3,200-m toe section at up to 94° inclination, where conventional tractors cannot sustain sufficient head tension.
Solution: Deploy the production logging toolstring using a six-drive, 12-wheeled configuration of TuffTRAC iX extreme-performance wireline tractors to efficiently provide the necessary head tension.
Results:
