Several extended reach-restricted completion-smart wells required matrix acid stimulation using Coiled Tubing (CT). These wells are equipped with Mechanical Formation Isolation Valve (MFIV) in the tubing end which needs to be reopened by using CT to access mother-bore for performing acid job. CT simulation results for these wells showed coil can reach only 60-70% of open hole interval. Calibrated friction coefficients were used in CT simulation based on the data base developed from other wells in the same area. Only CT-Tractor simulation showed 100% reach with maximum tractor over pull of 3200 lbs from the lock-up depth.
World’s slimmest CT tractor was developed in collaboration specifically to address the challenges of extending CT reach past lock-up depth during acidizing and other intervention jobs in minimum restriction extended reach well. The world’s slimmest tractor (2 1/8" outside diameter; OD) was able to provide a pulling force of 3200 lbs and was powered by intervention fluid pumped through coiled tubing. The tractor has many failsafe features and self-cleaning mechanism of gripper arms to overcome the challenges encountered while tractoring in open hole.
Four smart wells (with minimum restriction 2.81") were successfully matrix acid stimulated while the CT-Tractor combination were able to extend the reach of CT beyond lock-up depth. CT-Tractor was run-in-hole (RIH) to lock-up depth and then tractor was activated from that depth to extend the reach of CT. At total depth (TD), the tractor was isolated and de-activated by dropping steel ball. The wells were acid stimulated while pulling-out-of-hole (POH). Pre-flush was pumped while RIH at low pumping rate to avoid activating tractor before lock-up depth and after lock-up, pre-flush was pumped through tractor to activate the tractor.
This paper outlines the tractor characteristics, matrix acid stimulation jobs design parameters, detailed operational data captured and the learning curve achieved during job execution.