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Tales from the Field by Jeremy C. Wire Geoconsultants, Inc. The Well that “Walked” In drilling a particularly deep water well, it is customary to drill a straight, vertical borehole with as little deviation from vertical as possible. However, in some geologic settings, it’s not easy to accomplish this task, even when carefully watching weight on the bit during rotation and taking other precautionary measures. When the geology is horizontally layered, perhaps consisting of sandstone and interbedded shale, keeping a vertical borehole may be relatively easy, but where dipping layers are concerned, along with other geologic conditions in the borehole, the bit may tend to wander off course, and work its way in the up-dip direction of the layers. An example of this situation occurred in a geologic setting of a sandstone and shale sequence where a deep exploratory test hole for a well had a planned depth of around 1000 feet. The borehole diameter was 8-3/4 inches and would be reamed out for a small-diameter casing and screen section for a production well if warranted. The test hole was in a relatively small basin, near a major fault where granitic rock was exposed on one side with a dipping sandstone and shale sequence on the other side, not too far away from the location. There were no particularly difficult drilling conditions, with mostly shale being encountered to a depth of about 700 feet. Then sandstone with minor amounts of shale was easily penetrated, continuing to the planned depth of about 1000 feet, where hard granitic rock apparently should have been reached, but was not found. It was decided to drill ahead since borehole conditions were favorable, and this was still an exploratory test hole. Drilling continued first to 1400 feet, then 1800 feet, then to slightly over 2000 feet in depth, all in what appeared to be water-bearing sand- stone. Not wanting to court any bad luck, drilling was stopped at this point. There was some indication the borehole had drifted, based on some difficulty in making trips in and out for bit changes, but no serious “sticking” problems occurred. Since this test hole for a well was by far the deepest drilled in the area, in addition to the usual downhole geophysical logs, it was decided to run a dipmeter survey throughout the length of the borehole. This type of log would determine the dip of the sandstone and shale formation, as well as the drift amount from the vertical, and the direction of borehole along its entire length. The borehole was nearly vertical to a depth of about 1400 feet, but at this point it started deviating as much as 30 degrees from the vertical, or slightly more, to the bottom of the hole. In addition, sandstone layers were indicated to be inclined as much as 40 degrees in the direction of the bit. As far as could be determined, the bit was drifting in the up-dip direction of the bedding. The test hole was reamed out, there not being a serious attempt to straighten it in the deviated section, and six-inch steel casing with mill slots was installed to a total depth of slightly below 2000 feet. As far as we know, the well is still producing today, and for those of us who worked on the project, it is still referred to as the well that “walked”. Jeremy Jeremy Wire may be contacted via e-mail to michele@worldwidedrillingresource.com Nitrate Coated Premium Liners 5x6, 5x8, & 5x10 Gardner Denver 5-1/2x8 & 5-1/2x10 Gardner Denver 7-1/2x8 & 7-1/2x10 Gardner Denver Rods Heat-Treated & Chromed 5x6, 5x8, & 5-1/2x8 Gardner Denver 5x10 & 5-1/2x10 Gardner Denver 7-1/2x8 & 7-1/2x10 Gardner Denver New Pumps In Stock Gardner Denver 4x5 TEE Triplex. Gardner Denver 5-1/2x5 TEE Triplex Gardner Denver 4x5 or 4-1/2x5 Duplex Gardner Denver 5x6 Duplex Gardner Denver 5x6 Air Drive Duplex Gardner Denver 5x8 Duplex Gardner Denver 5-1/2x8 Duplex Gardner Denver 7-1/2x8 Duplex Gardner Denver 7-1/2x10 Duplex Gardner Denver 5-1/2x5 THE Triplex Gardner Denver 5x8 PAH Triplex Call for Prices. We Have a Variety of Brands of Mud Pump Parts and Power Units in Stock. Special or Obsolete Parts Made to Order . Cash for Surplus Mud Pumps . Rebuilt Mud Pumps 4-1/2x6 Gaso Duplex 4-1/2x6 Oilwell Duplex Gardner Denver 4-1/2x8 PA-8 Triplex Gardner Denver 5x6 Duplex Gardner Denver 5x10 Duplex Gaso 5x10 Duplex OVER 300 PUMPS IN STOCK Armstrong Machine Co. Inc. Pocahontas, IA 50574 USA 712-335-4131 ~ 24 Hours 7 Days a Week • Fax: 712-335-4565 800-831-4527 USA & Canada (8AM to 4PM Monday-Friday) armstrongmachine.com amci@armstrongmachine.com Hydraulic Grout Pumps 5”, 6”, & 7-1/2” 46 AUGUST 2019 WorldWide Drilling Resource ® EXB