Ground-Water Services Inc.

1. Topography or the presence of low areas are not always positive indications of the presence of bedrock fractures.

2. Shallow ground water and/or springs are not always positive indications of ground water within deeper bedrock.

3. The use of wires and forked sticks to locate wells (dowsing) is based upon simple electromagnetic principles; however, the user of these tools cannot distinguish favorable from unfavorable geology. They are also unable to determine the depth of the fractures or the expected flow rates. A comparison of modern geophysical methods to dowsing is presented below.

4. Geology beneath the area is the determining factor.

5. Bedrock fractures (openings) determine the presence and migration pathways for ground water through rock.

6. Geologic contact zones are primary targets for water wells due to the development of fractures along the contact zone. However, the center of contact zones may be deeply weathered; wells in these areas may be low yielding.

7. The alignment of abundant fractures across an area promotes the long-term dependability of a well and usually indicates a productive well.

8. Geophysical surveying can detect deep horizontal fractures within solid rock.

9.. Geophysical surveying can distinguish between quartz seams that are solid, those that are partially fractured, and those that contain productive fracture zones.

10. Geophysical surveying can detail the depth of the fractures, thereby preventing unnecessary drilling.

11. Geophysical surveys can be interpreted to indicate the expected flow rate from a well.

12. Hydrofracing in fractured rock areas is a method to improve a well's performance and dependability. Hydrofacing in unfractured areas is usually not beneficial.

The techniques we utilize have resulted in successfully interpreting subsurface conditions. Evidence of success is exemplified in finding a well site capable of yielding 300 to 800 gpm within the metamorphic rock
of North Georgia.

300- 800 gpm well

WHAT YOU NEED TO KNOW BEFORE HAVING A
WATER WELL DRILLED IN BEDROCK AQUIFERS
By
H. Dan Harman, Jr., P. G.
Ground-Water Services, Inc.

BACKGROUND INFORMATION
Ground water within bedrock aquifers exists in fractures or openings within the rock. The fractures are sometimes associated with quartz veins and geologic contact zones within igneous and metamorphic rock. The contact zones are either textural or mineralological changes which change the electrical properties of the rock. A successful well is drilled at a location to intersect the most fractures and contact zones possible. If you don't know where the fractures are and their depth, you are only guessing at the drilling location and the depth to drill.

Some drillers and some geologists use topographic features to locate well sites, but I have found that this ground surface feature method does not give enough information and usually does not indicate the actual fracture occurrences at depth in the rock.

WELL DOWSING (Why It Works and Why It Fails)
Some drillers and individuals use either sticks or wires to locate drilling sites. The history of dowsing dates back several hundred years, and has alot of misconceptions. The stick or wires very simply respond to the naturally occuring electromagnetic energy coming from the earth. Water, which conducts electricity, has its own electromagnetic energy field when confined in rock fractures. The water filled fracture is electrically distinct from the surrounding non-electrical rock. This is why dowsing works.

In addition to water filled fractures, mineral veins such as quartz also have their own electromagnetic properties. This fact then presents an identification problem for the dowser. The dowser cannot tell the difference between the water filled fracture and the quartz vein. This is why some dowsers fail to find water.

To prove my point, a comparison was conducted to locate a quartz vein which was visible in an outcrop in the Atlanta area. The attached photograph shows the quartz vein. Traverses were conducted right to left along the hill over the vein. The Wadi instrument, which I use, was conducted first. The computer printout clearly indicates the size and depth of the quartz vein which is visible and a vein which was not visible. The solid vertical lines indicate the quartz vein and the dotted lines indicate the fractured portion of the veins.

The second traverse was a compass traverse. The compass headings were taken every 25 feet along the traverse over the hill. The compass needle, which normally changes directions only due to magnetic bodies, does in this case, change directions due to electromagnetic energy. The first change was over a portion of the unexposed quartz vein, however the greatest change was over the exposed quartz vein. Note that the compass only indicated a broad area, not the exact location of the veins.

The third traverse was one with metal wires. The only distinctive movement of the wires was over the exposed quartz vein. The wire and compass traverses do not indicate what lies beneath the ground surface, only that there is some body with electromagnetic energy. In constrast, the Wadi survey clearly shows the location, size, orientation, depth and identity of the body. In my opinion, a wise investigator would choose a traverse which gives the most subsurface knowledge.

MODERN WELL LOCATION TECHNIQUES
There are established geophysical methods that can be used to locate the fractures and determine the depth of the fractures. These methods are based on simple electromagnetic and electrical resistivity principles and the fact that water conducts electricity. Ground water moving through rock has its own electromagnetic signal that can be detected by the appropriate instrument. A computer printout of the location, orientation and depth of the fractures can be generated as shown by the above example. The depth of investigation of the Wadi instrument is approximately 250 feet.

A second geophysical method is electrical resistivity. Since water conducts electricity, the favorable areas to drill are those where the resistivity is low. High resistivity values indicate dry rock with little or no ground water. Knowing the general geology of an area also will indicate if the underlying rock will contain sufficient ground water. The geophysical methods detail the fractures within a generally favorable geological parent rock. The depth of investigation of the resistivity method can be as deep as 1,000 feet. The resistivity method can also be used to estimate the flow rate to be expected from a well. This estimation is based on the resistivity values, the fractures and contact zones detected and past experience.

An investigation which includes the above geophysical methods is far superior to a compass or dowsing survey. The geophysical surveys are objective and definitive.

WELL HYDROFRACING FOR WELL FLOW RATE IMPROVEMENTS
Eventhough geophysical methods can greatly reduce drilling risks, there are those locations and fractures that just do not yield as much water as initially expected. Wells like this require hydrofracing to improve the well's yield.

Hydrofracing is a process conducted after the well is drilled. It involves conducting a tv camera inspection of the well to detail the depth and physical condition of the fractures. This allows the operator to position inflatable packers into the well above and below the fractures. Water under very high pressure is injected into the fractures to enlarge and extend them away from the well, thereby allowing more ground water to enter the well at a faster rate. The hydrofracing process results in the interconnection of more fractures.

The key factor for the success of hydrofracing is the presence of additional fractures in the immediate vicinity of the well. This is where the geophycial surveys help by identifying where these additional fractures exist.

SUMMARY
Before having a well drilled into rock, learn the modern methods available which are applicable to your situation. Having as much knowledge as possible reduces risks and gets the most for your investment.

Comparison
Wadi, Compass and Metal Wire Traverses
Over
Electromagnetic Structures