Thief zones—commonly caused by fractured or highly permeable formations—can lead to lost circulation, which disrupts well cementing, jeopardizes the wellbore, and increases costs because of lost or delayed production. It also often results in NPT and costs associated with the implementation of various remedial measures. In Argentina’s Anticlinal Grande Field, an operator was encountering such losses during a multiwell drilling campaign. A solution was required that would isolate the lost circulation zone after the wellbore below it was cemented and enable placement of a second cement stage above the thief zone, back to surface.
Any packer used for isolation had to set in open hole and withstand tough running-in conditions in the deviated and undergauge boreholes. The ability to rotate and place weight on the packer while running in was also essential. The operator had used swell packers in some wells but wanted a more cost-effective solution.
SLB external casing packers are robust expandable stainless steel devices that can withstand reciprocation and rotation to pass through doglegs and tight spots. They can be used for any stage cementing operation to provide zonal isolation and prevent fluid migration in the annulus.
The packer was made up to the casing string and run in. After the first stage was cemented, the packer was set in open hole by applying pressure in the casing. The pressure caused the integral stainless steel sleeve to expand outward, conforming to the shape of the borehole. A patented thin layer of bonded elastomer ensured sealing despite any irregularities in the borehole wall.
Ten 5.5-in packers were installed in 9.2-in open holes, at depths ranging from 1,968 ft [600 m] to 5,577 ft [1,700 m]. The cementing campaign was a complete success. In each well, the packer isolated the thief zone and enabled cementing operations to resume; cement was pumped back to surface through a stage collar above the packer. The operator saved 30% in packer costs in addition to the rig time saved through on-demand expansion and immediate sealing.
