This week (week of Aug 25), DTD has completed an 860 foot horizontal biosparge well, planned as a pilot for what may become an extensive array of wells to clean up historical petroleum contamination at a decommissioned military fuel storage facility. The well will be used to inject air at low volume and pressure into the groundwater to stimulate in situ microbial activity to consume the fuel hydrocarbons.
The project – in planning for over a year – required a unique blend of directional drilling technologies that DTD has mastered over the years. The well path is situated in an area densely packed with active fuel pipelines, active monitoring wells, and abundant surface obstacles – the bore even passes beneath an active electrical substation. At some locations, the curving bore path, 45 feet deep, passes within a few feet of deep groundwater monitoring wells. Besides the physical obstacles, the electromagnetic spectrum at the site is saturated with interference from pipeline cathodic protection and electrical lines (and the substation) as well as passive interference from pipeline appurtenances.
For this reason, DTD selected the Gyroscopic Steering Tool (GST) as the locating technology of choice to guide the well along a precision path. As described in a recent DTD newsletter, the GST uses solid state, high-tech inertial guidance technology to provide real time positioning and steering guidance as the drilling advances. During the drilling, the bore never deviated more than a half-foot, and usually much less, in any plane from the design path. A testament to the skills and accuracy of the GST, as well as DTD’s experience drilling supervisor, James Ditto, the 860′ bore was completed in a little over two days. DTD used our CMS 9030 drill rig – capable of 90,000 pounds of thrust – for the project, supported by a 4000 gallon capacity mud recycler and other materials handling equipment.
Due to the potential for caving conditions in the bore that might hinder placement of the well screen and riser in this single-ended, or blind, bore, DTD used a variation of our patent-pending Knock-Off technology to install the well materials after the pilot bore was completed. After tripping out the GST tooling, the Knock-Off rods were advanced to the bottom of the bore. The well materials – 4″ diameter Schedule 80 PVC – were then advanced through the drill rods and anchored at the end of the bore. With this technique, DTD can confidently install relatively weak PVC well screen even in an extended length bore such as this one.
Remaining tasks at the site include well development and surface completion – all routine tasks once the critical parts of the process – drilling and screen installation – are completed. The well is expected to be put into operation later this year, and further installations at the site will be considered on the basis of the results of the pilot test.