Abstract
Well intervention in horizontal extended reach wells (ERWs) comes with a myriad of challenges and in the case of coiled tubing the overarching impediment is in reaching the target depth (TD). Frictional forces act against the coiled tubing (CT) while being pushed from surface, this eventually leads to helical buckling of the tubing and early lockup where no further progress is made. Advances have been made over the last decade with the development of high-tech downhole CT tractors that deliver a strong pulling force to overcome these frictional forces. Restrictions in the well completion require these tractors to collapse to 2-1/8″, and then to expand to the cased or open hole size of up to 6-1/8″. With many wells having a larger bore size of 8-1/2″, a CT tractor did not exist to improve the coverage in those type of wells.
At first glance, modifying the existing tractor for 6-1/8″ sized holes to function in 8-1/2″ sized holes could be accomplished by simply extending the lengths of the arms. However, the reality is a little more nuanced with several innovations required to deliver the same pulling force as the 6-1/8″ tractor version. This new generation of downhole compact high expansion tractors have improved push-links and newly designed grippers to enable rig-less acid stimulation and production logging in ERWs.
The high expansion tractor is an important facilitator in CT well interventions to tackle challenging ERWs by increasing the coverage in 8-1/2″ hole sizes. The CT tractor design, development, testing and first deployment was conducted in 2021. The major advantages gained from increasing the reach can be summarized as follows:
The CT high expansion tractor enables successful reservoir surveillance and production monitoring, including improved reservoir understanding providing data to update and calibrate reservoir models.
Acid stimulation in 8-1/2″ open hole wells on CT targeted fluid placement to improve well productivity to increase revenue per well.
Detecting and then shutting off water inflow zones with CT techniques, avoiding the need for drilling a side track.
This new generation of slim tractors is the first in the industry to operate in wells with a diameter of 8-1/2″ and an operating range from 8″ to 10″. The key metric to successful acid stimulation or logging applications in ERWs is the ability to achieve maximum coverage of the openhole section. These engineered solutions demonstrate how creative innovations in technology design are improving accessibility in ERWs, resulting in superior reservoir management outcomes.
