Improving Steam Injection in California

Identification of problem

Operators in Bakersfield, California, utilize steam injection wells as part of their operations. Single holes are perforated in a cemented casing string at various depths, allowing operators to inject steam into the formation at different depths to improve production on nearby wells. Over time, the majority of the steam will begin to inject into one of these holes, preventing steam from entering the rest of the perforations in the well. When this occurs, it is necessary to plug off the “thief” hole. The traditional method of doing this was to place a casing patch over the hole. This created a restriction in the well and over time the patches began to leak due to the high temperature steam.

Issues to overcome

Temperature in these wells during steam injection can reach as high as 330°F (165°C) and the operator wanted full bore access in the casing after the hole was plugged. Although steam could be injected into the zone, injecting a viscous fluid like cement or resin was difficult and due to the downhole temperature often unreliable.

Application

Utilizing a wireline unit, a Wel-lok™ Perf-lok was set inside the 3 ½” casing across the ¼” perforation hole. The bismuth alloy was melted, flowed into the perforation hole via gravity (no injection required) and expanded after solidifying to plug the hole. The remaining bismuth alloy plug inside the 3 ½” casing was milled out leaving only an alloy plug in the perforation hole and full bore access inside the casing.

Outcomes/Conclusion

After successfully setting and milling out the alloy plug, an injection survey was performed. This survey showed the “thief” hole had been plugged and all the steam was being injected into perforations deeper in the well, just as the client had requested.