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PBO Strainmeter Installation Update: A Whole New Frontier! (3)


Day number three of the BSM activity at Clark West continues. Crews are thankful for the beautiful morning weather, sunny and clear skies with temperatures in the fifties. While waiting for the loggers to arrive from Seattle, WA, people kept busy around the work site moving rock and piles of cuttings, preparing casing, and bagging samples. Overnight, water had filled the majority of the hole, stopping at just 31 feet below the ground surface. By 11am, the logging crew from Golder Associates were on site and ready to begin a series of four different logging tests. Each test takes quite a bit of time, having to lower the instrument to the bottom of the drill hole and slowly pull it up to the top, continuously taking measurements along the way.

The first instrument inserted into the hole was a caliper. Used to measure the diameter of the borehole and to make sure the hole is clear of any debris. The caliper has three legs that extend out to detect the diameter of the borehole wall. In addition, the caliper can also tell where a fracture zone might be, not only for alerting crews to areas where equipment might get hung up when inserting into the hole, but also to give the crew even further information about the characteristics of the hole. With the caliper moving at a slow 6 feet per minute, it took about an hour to complete the test. Immediate results of the test showed that there was a mixture of smooth and rough patches throughout the hole. Not surprisingly, when the instrument passed the clay layer identified during the drilling, the diameter of the hole expanded.

The second test was done with a full wave sonic tool. This instrument measures how fast sound travels using P and S waves. This test provides information on the strength and density of the rock. Data from these observations need to be post processed before any results can be determined. The instrument moved at a speed of 9 feet per minute taking a little over an hour to finish the test.

An acoustic televiewer was inserted next, moving the slowest at 3 foot per minute. The televiewer takes a 360 degree line scan while moving up through the hole yielding an image that is used to determine the dip and dip direction of the fractures in the rock. Fractures that cut through the rock at an angle will show up on the computer screen as a sinusoid. Immediate results show a very rough, uneven wall without a lot of structure most likely caused by the pounding of the hammer drill bit. Just as the inclinometer read yesterday, the televiewer is logging a 1.7 - 1.8 degree inclination.

The fourth instrument was a natural gamma tool which measures natural radiation from the rock, specifically from radioactive isotopes of potassium, uranium, and thorium. These isotopes occur naturally in certain quantities in most rock and can help detect naturally formed boundaries, such as the clay layer that was found while drilling.

Finally, a self-potential (SP) and resistivity test was taken to determine the electrical conduction properties of the rock. This is another way to determine where there are rock boundary and lithology changes.

After examining the data further, detailed results will be put in report and posted on the PBO web site.

As the day crept on, the temperature continued to drop. By the time crews packed up at 7pm, it had dropped to a chilly 34 degrees. Everyone was happy to go home for the day to warm up and get a good night sleep. Moving right along, at the crack of dawn tomorrow morning the crews will begin inserting 6-inch casing.


Last modified: 2020-01-28  22:54:10  America/Denver