Unconventional acid stimulation in the permian

Unconventional wells
JUSWT123216 Unconventional acid stimulation - Well Intervention - Welltec
  • Lateral depth +/- 6,800’ TVD
  • Lateral length 5,001’
  • Tractored total +/- 15,000’


An operator in Texas wanted to stimulate production zones in a horizontal well individually with acid. Conventional ball-drop frac sleeves couldn’t be used, as each sleeve had to be closed before opening the next. The operator had been in contact with Welltec® regarding our substantial knowledge of horizontal intervention during the design phase.

Subsequently, Welltec tools were incorporated into the well design and the operator chose Welltec to perform this complicated sliding sleeves operation. The well was located in a field in the Permian Basin in Texas. The operator required the opening of a number of 4½” sliding sleeves to acid frac through them individually, close them and move on to open the next sequential sleeve in an 18 stage completion while remaining in wellbore.


The preferred solution consisted of a Well Tractor®, Well Stroker®, and Well Key® with dual acting keys. This is a highly feasible solution; significantly less expensive and much more time efficient than the jointed pipe or coiled tubing alternatives. Prior to load out, a System Integration Test (SIT) was carried out at the Welltec facility in Houston, TX.

The test confirmed that the Welltec tools would be ideal for the operation, and concluded that it takes two strokes to fully open or close the sleeve. The SIT verified that the toolstring (with keys deactivated) would be able to pass through the closed sleeve; that it could locate the profile correctly; and that the activated Well Key was able to engage the sleeve shifting profiles from above and below. The test also showed that the combination of Well Key and Well Stroker could overcome the friction holding the sleeve closed and move the sleeve fully to open the position. The inactive tools could be pulled back to a position above the sleeve without inadvertently engaging the profile closing the sleeve, and the Well Key and Well Stroker combination could close the sleeve again after the acid stimulation.


This successful exercise left the operator with all 18 intervals stimulated individually in isolation from each other without the use of drop balls. Because Welltec was able to stay in the wellbore while the acid stimulation was in progress, the operator saved considerably in terms of time and money.

The extensive pre-job planning and research was an important contributor to the success of this job, which was completed in just five days. In comparison it would have taken 10 days using coiled tubing and 20 days with a workover rig. The operator was very pleased with the results of the operation and has since asked us to make another trip in the well to manipulate some sleeves that they had accidentally closed with a completion string.

This successful exercise left the operator with all 18 intervals stimulated individually in isolation from each other without the use of drop balls.