Solid Stem Auger Sampling in Saturated Materials

The primary problem with drilling in loosely consolidated, saturated materials is collapse and filling of the hole as the augers are removed. Methods for cleaning out an auger hole above the water table will not work in this case, because whatever materials are removed will simply be replaced by additional saturated material. Therefore, the methods for obtaining representative core samples in this environment are restrictive and laborious. However, there are times when a sample need is great...

Solid Stem Augers

Samples obtained from solid-stem auger-drilled holes usually are a mixture of the penetrated materials. Material samples that are deposited around the surface perimeter of the hole are representative of the penetrated materials howevei they are a mixture of several feet of the lithology encountered by the drill head. With experience, the driller can feel some textural changes while drilling at the approximate depth at which these changes are encountered in the hole. These notations, combined...

Drive Core Sampling

Hydrologists usually rely on a mixture of drill cutting samples bailed from the hole to determine the grain-size distribution of an aquifer material from which to select the proper screen-size-slot openings for constructing an observation well or production well. However, the cable-tool drill provides an easy method for determining the true grain-size distribution by means of drive-core sample analyses. Drive cores can easily be taken in dry materials or saturated materials with the cable-tool...

Hydraulic Rotary Coring

Drilling Rigs Sketch

Hydraulic-rotary coring is commonly referred to as diamond drilling. The name seems to fascinate people, possibly because it was originally used to explore for gold and other valuable minerals. Even today, when coring is used to collect samples for many reasons, this fascination with coring still exists. Coring is the one method of drilling that extracts from the earth an actual piece of the earth that the hydrologist, geologist, engineer or other scientist can feel, see, and study in great...

Methods of Drilling

The methods of drilling with air are basically the same as those methods used for hydraulic-rotary drilling. Air is used instead of a drilling mud as the circulating medium to cool the bit and remove the bit-drilled cuttings from the hole. The injection pump is used in conjunction with the air compressor to aid in the removal of sticky, wet cuttings from the hole otherwise they tend to accumulate on the drill pipe and also plug the bit. Drilling foam, polymers, and other drilling additives can...

Coring Procedures in Rock

Basic techniques of air-rotary coring are almost identical to techniques of hydraulic-rotary coring air, rather than a drilling mud, is circulated to lift and carry the drill cuttings out of the hole, and, at the same time, cool the bit. All working components are the same, except the mud pump is replaced with an air compressor. In air-rotary coring, the same hydraulic-rotary problems of loss of circulation can occur, and, if the additives described in the following section are not adequate to...

Shelby Tube Samples

Sometimes, undisturbed, Shelby-tube samples may be required from a hydraulic-rotary drilled hole. The use of the Shelby-tube sampler is restricted, however, because the sampler cannot be washed in due to the ball-check valve in the sampler. The ball-check valve is needed in the head assembly of the sampler to retain the sample in the tube upon withdrawal of the sampler from the hole. To sample using the Shelby-tube sampler first spot the bottom several feet of the hole with the high-gel...

Solid Stem Auger Sampling in Unsaturated Materials

Picture Thin Walled Open Tube Sampler

If a formation of interest is encountered in the process of auger drilling, the following techniques for securing a core sample may be used. 1. Remove the auger so all the cuttings on the auger flight do not fall back to the bottom of the hole. This usually is best accomplished by a very stow clockwise auger rotation, while pressing into the material as hard as possible. This will result in the cuttings packing on the bottom of the auger flights and not falling back to the bottom of the hole,...

Hollow Stem Auger Sampling in Unsaturated Materials

Core sampling through the hollow-stem auger in unsaturated materials is a relatively simple process. Unlike the problems of loose material left in the hole when solid-stem augers are pulled, the hollow-stem auger remains in the ground to act as a casing and hold out any potential caving materials. The only loose material remaining in the hollow-stem auger-drilled hole is 2-3 in. of material loosened by the pilot bit, that has not been moved up the auger flight. The method for sampling through...

Hollow Stem Auger Sampling in Saturated Materials

Core sampling through hollow-stem augers in saturated materials encounters problems that require different techniques than those described for the unsaturated zone. The greatest problem is piping. When the center-assembly plug and pilot bit are withdrawn, there is a tendency for the viscous slurry of cuttings, still contained in the bottom of the hole, to be pumped upward into the hollow-stem augers. Withdrawal of the center-plug assembly is analogous to a piston pump that pulls this viscous...

Drive or Push Core Samples

The geologist-hydrologist too often relies on a mixture of cuttings to make critical decisions on the selection of screen-size openings and proper TYPICAL CHART FOR 2-7 8 DRILL PIPE 24.5 x G.P.M. TYPICAL CHART FOR 2-7 8 DRILL PIPE 24.5 x G.P.M. FEET MINUTE Figure 29. Pump delivery versus return velocity. FEET MINUTE Figure 29. Pump delivery versus return velocity. placement of the screens. Also, obtaining an in-situ representative sample is sometimes necessary of the formations being sampled...

Drilling Mud Pit Construction

The necessity of using high-viscosity drilling fluids for coring unconsolidated materials presents problems in settling out cuttings, which, if not settled out, would cause excessive weight of the drilling fluid resulting in greater hydrostatic head of the drilling mud column and consequently deeper drilling-fluid invasion. The manner and size of the drilling-mud pit construction is important to the cuttings settling process because the drilling mud must keep moving, if the cuttings are to...

Air Rotary Coring

Air-rotary coring of rock is an established procedure that uses air instead of a water-laden drilling mud to circulate the cuttings out of the hole many core drillers prefer this method to mud-rotary coring. In some instances, the air-rotary coring method cuts faster and provides less-contaminated core. Our discussion of the method will be very brief and describes some advantages and disadvantages so a hydrologist can decide if it is the proper method to specify, considering the intended use...

Reverse Circulation Drilling

The method of reverse-circulation drilling was designed primarily for drilling large-diameter production wells in unconsolidated formations. The practical minimum diameter about 16 in. for drilling holes by the reverse-circulation method almost precludes its being used for test-hole drilling. However, this method provides the best cuttings samples of any drilling method because of the large intake capacity of the bit 5 in. or more this method also provides fast delivery of cuttings to the...

Lost Circulation of Drilling Fluid

Partial or complete loss of drilling-fluid circulation sometimes occurs when hydraulic-rotary coring of rock is performed. This toss results from encountering fractures or high-intergranular permeability in the rock, large solution openings in limestone-associated rocks, and cavernous or scoria-cinder zones in basalts Teasdale, 1980 . Blind coring is sometimes attempted no drilling fluid circulated to the surface however, this method could result in stuck or lost drill pipe. If the coring is...

Procedures of Sampling in Hydraulic Rotary Drilling

As apparent from the discussion of mud and hole-control problems when the hydraulic-rotary system is used for drilling, taking representative samples of penetrated formations is difficult and relies on the skill and experience of the driller. We describe the normal collection of cuttings samples, as well as taking drive or push-core samples to provide more representative samples in a hydraulic-rotary drilled hole. The washing action of the drilling mud as it moves bit-generated cuttings up the...

Removal of Core Barrel from the Hole

After the core has been collected, the core barrel is retracted a short distance several inches to break off the core. If standard coring rods and core barrel are used in the coring operation, the rods are tripped out of the hole and the core barrel is dismantled in much the same manner as described in a later section, Removal of rock core from the inner tube. The wireline system of coring provides the advantages of not having to trip the coring rods out of the hole after each core run is...

Removal of Unconsolidated Sediment Core from the Inner Barrel

Longyear Drilling Pump Out Adaptor

Removal of the core of unconsolidated sediments from a standard wire-line core barrel differs from the procedure used for removing a rock core. The removal procedure is as follows 1. The solid inner barrel is removed from the outer core barrel and is placed in a chain-type pipe vise. The core-retainer shoe is then unthreaded from the lower end of the inner barrel and the swivel-head assembly is unthreaded and removed from the upper end. 2. The clayey filter cake on the outside of the core will...

Methods of Coring

Mud Density Depth

Coring Procedures in Unconsolidated Sediments Hydraulic-rotary coring of unconsolidated sediments for the purpose of obtaining undisturbed cores is extremely difficult, compared to hydraulic-rotary coring of rock. Most core drillers consider it impossible to core unconsolidated materials and, as a consequence, many will not attempt it. These unconsolidated materials are most commonly referred to as overburden and they are cased off in the exploration-drilling industry, prior to starting any...