DTD recently completed a project involving the abandonment of two historic wells at a former military installation in Arizona. The wells, originally installed approximately 20 years ago, were some of the earlier wells installed for remediation efforts. Wells were installed to remove hydrocarbon LNAPLs. The next phase of remediation involves steam injection through different wells. To ensure that steam did not travel along the older horizontal wells DTD was contracted to abandon them with grout. Prior to injecting grout DTD perforated the well casings leading to the screened sections. The perforation step ensured that grout would flow into the soils surrounding the well along the screened section, and also along the casing segments.
DTD mobilized a CMS 60×15 drill rig to the project site. This rig was selected from DTD’s inventory for several site specific advantages. One, the rig’s compact size worked well in the confining site. Second, this drill rig has the flexibility to drill at angles from nearly horizontal to vertical. This second advantage was quite useful as one of the wells entered the ground at a 35 degree angle (very steep in the horizontal drill world). Additional equipment included two air activated perforating tools.
Casing perforating was completed over several days. For both wells the casing material was steel. A total of 1,560 feet of casing was perforated with multiple passes of the perforator completed for both wells. After removing the perforating tool the drill string was pushed back down the well for grout injection. Pumping grout through the drill rod ensured that the grout flowed into the screen sections at distances greater than 1,200 feet from the entry. Since the grout mix was a specialty high temperature mix DTD provided an one-off on-site mixer. A total of 44 batches (approximately 44 cu yds.) of grout were mixed on-site and pumped down the well via a grout pump.