Jet Drilling in the 

Fairbanks Area 

Alaska

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1539-B

Jet Drilling in the 

Fairbanks Area 

Alaska

By D. J. CEDERSTROM and G. C. TIBBITTS, JR.

CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES 

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1539-B

A new approach to water-well drilling 

in a subarctic agricultural area

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1961
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington 25, D.C.
CONTENTS

	Page 

Abstract__ _ _-__-__-___-_-_---_-_--_-__-_____-__________--_--_--_ B 1

Scope and purpose of report- __--_-------_____-_-_____-__--_________ 1

Synopsis of geologic history_______---.____-_____-_____-_-___-_--____ 2

Ground-water conditions___________________________________________ 3

Water-bearing formations___--_--____-__________-_-___________ 3

Birch Creek schist.________________________________________ 3

Older sand and gravel deposits._____________________________ 4

Tan silt--__--_--_-__--_--______--_--_-----_--_----_--____ 4

Gravel deposits of the Tanana Valley________________________ 4

Jet drilling______________________________________________________ 4

Equipment-__________________________________________________ 4

Drilling open hole.____________________________________________ 10

Setting casing---___-_______________--_-_-_-_____-__----_--_-__ 13

Driving casing.-__--___--______-____-_-_---_-___-__-----_-_-_. 13

Setting casing without removing drill rods ________________________ 16

Special problems______________________________________________ 18

Development and testing of water-bearing deposits.____________________ 20

Test holes drilled in 1954__--__-_-________---__-----_-_--__--__- 22

Summary of test drilling__________________________________________ 24

Use of the jet method of drilling____________________________________ 25

Production drilling____________-_______________---_-_-___-__-_ 26

Simple drilling equipment-_________________________________________ 27

Geologic test drilling--___-___-_____-___-__-___-----__-_-_____--_--- 27

References cited.__________________________________________________ 28

ILLUSTKATIONS

Page 

FIGURE 1. Pump and power unit of jetting rig- ________________________ B-5

2. Tower used in U.S. Geological Survey jet drilling in Fairbanks

in 1954__-__-_______-____._________________-__-___-__- 6

3. Mud pits for jet drilling-_________________________________ 7

4. Driller operating swivel_________________________________ 8

5. Bits used in jet drilling.---__--___________-____--_--_----- 9

6. Activation of drill rods by engine and cathead.-.------------ 11

7. Casing hammer in driving position___-_____-___-_-_-__-__-_ 14

8. Lifting casing using swivel and rod_______________________ 17

in

CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

JET DRILLING IN THE FAIRBANKS AREA, ALASKA

By D. J. CEDERSTROM and G. C. TIBBITTS, JR.

ABSTRACT

The report describes the construction and operation of an experimental jetdrilling machine in the submontane area north of Fairbanks, Alaska. The 

drilling conducted during a 2-month period in the summer of 1954, penetrated 

the Birch Creek schist and the sand-, silt-, and gravel-filled old subordinate 

valleys. Some of the silt has a high organic content and is called muck. Some 

of the muck was permanently frozen. Silt and muck were drilled rapidly, and 

required as little as 1% minutes per foot including time for changing rods, 

whereas drilling time in hard-packed sand and in schist averaged about 15 to 

20 minutes per foot. Frozen muck required about 3 minutes drilling time per 

foot. It is concluded that the method is a practical and economical one for use 

in the area in which it was tried, and it could be used with reasonable success 

in other alluvial areas where boulders are uncommon.

The equipment consisted of a double-acting piston pump capable of furnishing 

fluid at a pressure of 100 psi, a 7- to 8-horsepower type Z single-cylinder engine, 

and a derrick. A reciprocating motion was provided by a crank that operated a 

centrally pivoted beam. The drill rods were 1-inch extra heavy pipe. Z-bits 

and chisel bits were used. Operation of the rig, difficulties encountered, and 

suggestions for avoiding time-consuming trouble are discussed.

The usefulness of the method for general earth testing is mentioned, and 

suggestions are made for jet drilling on a production basis.

SCOPE AND PURPOSE OF THE REPORT

In July and August 1954 a modest drilling program utilizing the 

water-jet method was carried out by the U.S. Geological Survey in 

the submontane area just north of Fairbanks, Alaska, to determine the suitability of this method for use in this region. The method 

was successful, and m-uch interest was shown by well drillers and 

others who believed the method generally adaptable to much of the 

Tanana Valley and, perhaps, elsewhere in Alaska. This report discusses in detail the construction and operation of the jet-drilling 

machine so that the equipment, procedures, and results may be evaluated and utilized by interested persons. The adaptability of the

B-l
B-2 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED- STATES

method for geologic testing is also considered.

The personnel who worked on the project were not trained well 

drillers. The fact that untrained personnel were able to achieve 

fairly good production results indicates the simplicity of this method 

of drilling. The test drilling done in 1954 was a part of an overall 

study of the ground-water resources of the Fairbanks area made by 

the senior author.

The geology and hydrology of the Fairbanks area are discussed 

here only to the extent necessary to furnish background data for a 

better understanding of the functioning of the jet-drilling process 

as used in the area.

SYNOPSIS OF GEOLOGIC HISTORY

An arcuate series of low mountains a few miles north of Fairbanks 

forms part of a range elongated approximately east and west. Near 

Fairbanks these mountains rise from a few hundred feet to more than 

1,000 feet above the floor of the Tanana Valley on which the city is 

located. The mountains have a core of hard rocks, largely Birch 

Creek schist of Precambrian age (Mertie, 1937, p. 46), a deeply weathered slaty to sandy highly micaceous schist in which only a few hard 

layers are found, either quartzite or, more commonly, quartz veinlets. 

Exposures are relatively rare owing to a mantle of fine tan silt of 

Pleistocene age.

The tan silt that covers most of the hills ranges in thickness from a 

few feet to about 300 feet, and is thickest on the lower slopes. On 

some of the slopes and in the mountain valleys, particularly in the 

larger valleys, the silt has a high organic content and is locally referred to as muck. This black muck and the tan silt which have been 

considered for the most part contemporaneous overlie coarse gravels 

flooring the large valleys at low altitudes. However, sandy deposits 

in the submountane area north of Fairbanks are not confined to 

the large creeks. Sand and gravel deposits occur also at various 

depths below silty deposits that almost fill and partly mask old buried 

channels. These deposits may be found at some places at altitudes 

of as much as 800 feet above sea level or 350 feet above the Tanana 

Valley floor. Downslope these coarse deposits merge with highly 

permeable silt and sand and gravel of the Tanana Valley fill. These 

are stream-laid deposits, largely derived from the Alaska Range to the 

south (Mertie, 1937, p. 187).

Much of the alluvium on the Tanana Valley floor is permanently 

frozen. So far as is known, the frozen masses are wedge-shaped, their 

thin edges being along the streams. Away from the streams the 

thickness of frozen ground increases and is known to be as much as
JET DRILLING IN FAIRBANKS AREA, ALASKA B-3

243 feet beneath Fairbanks. The thickness of frozen ground diminishes to a vanishing point on the south-facing mountain slopes 

north of Fairbanks. In the higher part of the mountains only black 

muck in some small valleys leading back into the hills is permanently 

frozen.

GROUND-WATER CONDITIONS

On the lower slopes north of Fairbanks, ground water occurs under 

artesian conditions. Generally, the confinement is due to an impermeable cover of frozen silt, and wells drilled here may flow or, if the 

well does not flow, the static water level may be only a few feet below 

the land surface. Upslope, at the upper limit of permanently frozen 

ground, artesian conditions may change abruptly to water-table conditions, and at the higher altitudes the water levels in wells may not 

rise much higher than the level of the upper limit of permanently 

frozen ground. In one well along the ridge, off Steele Creek Road, 

depth to water is greater than 250 feet below the surface.

On the wide Tanana Valley floor on which Fairbanks is situated, 

ground water occurs under water-table conditions; the water table 

ordinarily is 12 to 14 feet below the surface. Where the ground is 

frozen above the water table, wells must be drilled through the frozen 

ground to unfrozen ground below. In such wells water encountered 

below the permafrost generally rises to the same static level as water 

in wells drilled in unfrozen ground.

WATER-BEARING FORMATIONS 

BIRCH CREEK SCHIST

On the submontane slopes and ridges, ground water ordinarily is 

obtained from schist bedrock. The depth to bedrock there ranges 

from a few feet to more than 300 feet, and is greatest at the lower 

altitudes where bedrock is covered by thick alluvium.

The Birch Creek schist is deeply fissured and weathered, and, in 

some places, the weathered zone is as much as 300 feet thick. The 

weathered bedrock is not completely tight and impermeable, but is 

made up of streaks of fractured more-or-less brittle rock intercalated 

with clayey and sandy layers and a few very hard thin streaks of 

silicified (quartzose) material.

Water is obtained from relatively clean (clay-free) fractured rock. 

Commonly, only a little water is obtained from wells completed in 

broken shistose material. Fractured silicified material ("quartz 

streaks") is ordinarily a better source of water; yields of as much as 

10 gpm (gallons per minute) from wells of 2-inch diameter have been
B-4 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED* STATES

obtained from tapping highly fractured brittle rock, and more than 

50 gpm has been obtained from wells of larger diameter.

OLDER SAND AND GRAVEL. DEPOSITS

Above the level of the Tanana Valley floor, thick sand and gravel 

deposits overlie bedrock in many places, particularly in the large 

valleys transecting the hills. As determined in part by Geological 

Survey test drilling, the small and commonly inconspicuous valleys 

on the higher slopes are floored by sandy material, which, in places, 

is coarse enough and thick enough to be a source of small to moderately 

large supplies of water. (See discussion of test hole 15, p. B-24.) 

The subordinate valleys may be underlain by water-bearing alluvium 

as high as 800 feet above sea level, or 350 feet above the Tanana Valley 

flats. However, to the writers' knowledge, there is not a single well 

in the area that taps these coarse deposits, though at least two wells 

were cased through permeable water-bearing gravelly deposits and 

yielded water from schist at greater depth.

It is the writers' opinion that yields greater than 100 gpm might 

be obtained from properly finished wells drilled in some of these old 

buried channels at fairly high altitudes in the agricultural area north 

of Fairbanks.

TAN SILT

The tan silt is generally impermeable, but seemingly furnishes a 

little water to a few dug wells. A few wells obtain a copious supply 

of highly mineralized water from thin sandy streaks in black muck.

GRAVEL, DEPOSITS OP THE TANANA VAZ.LEY

On the Tanana Valley flats ground water is available practically 

everywhere in large quantities (Cederstrom, 1952, p. 23, 27) from 

coarse gravelly deposits requiring only a minimum of development. 

Wells of 2-inch diameter yield as much as 40 gpm to suction pumps, 

and larger diameter wells are reported to yield as much as 2,800 gpm. 

Ordinarily, wells ending in these formations are not screened and are 

given only a minimum of development.

JET DRILLING

EQUIPMENT

Following Geological Survey test drilling in Fairbanks in 1948 and 

1949 by the cable-tool method, it was decided that further test work 

in the area might be more economically carried out by the jetting 

method, and that a demonstration of the practicability of the jetting 

method in the area would be of interest to many. Accordingly, in
JET DRILLING IN FAIRBANKS AREA, ALASKA B-5

1950, an experienced jet driller, Mr. Leonard Reynolds, of Walkerton, 

Va., was brought to Alaska to build and operate a simple rig suitable 

for the jetting method of drilling. The drilling equipment subsequently built and used is similar to some in commercial use in eastern 

Virginia. More modern equipment undoubtedly would result in an 

appreciable saving of drilling time and would facilitate some of the 

many jetting operations. As built, however, the rig was generally 

satisfactory, and for some operations it performed admirably.

The equipment was assembled initially in Palmer in 1950. After 

drilling in Palmer and Anchorage in 1950, it was decided that basic 

improvements were desirable, and a crank and walking-beam mechanism was added in 1951. The rig was used briefly in Anchorage 

that season. When the Fairbanks work was scheduled, it was further 

decided that the original derrick should be increased in height from 

20 to 28 feet. The height was subsequently reduced later to 25 feet.

A jet-drilling rig consists primarily of (a) a positive displacement 

pump (fig. 1); (b) a source of power for the pump and the drilling 

motion, which is provided by a walking beam and a crank arm; and 

(c) a tower (fig. 2). The tools consist of a string of hollow rods at 

the lower end of which is a drill bit. Water is pumped under moderate 

to high pressure through the rods and issues from the drill bit. The

FIGURE 1. Pump and power unit of jetting rig used in test drilling in Fairbanks in 1Q54. 

577871 O «1 2
B-6 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED- STATES

drilling water carries the cuttings to the surface by upward movement in the annular space between the rods and the walls of the hole. 

It then flows into a series of two or three mud pits (fig. 3) in which 

the cuttings settle, after which the drilling fluid is picked up again 

by the pump (fig. 1). As operated in Alaska, one man on the tower 

rotated the string of rods by hand (in a clockwise direction to keep 

the joints tight) while the machine provided an up-and-down or 

spudding motion to the rods. As needed, necessary slack line was 

released by the operator at the machine (fig. 4).

FIGURE 2. Wood-frame tower used in jet drilling In Fairbanks in 1954.
JET DRILLING IN FAIRBANKS AREA, ALASKA B-7

In the Geological Survey jet drilling of 1954, a 7- to 8-horsepower 

single-cylinder type-Z engine was used. The speed of the engine 

shaft was such that gearing down was desirable. Power was transmitted by V-belts to a second shaft and from the second shaft by chain 

drive to a third shaft (fig. 1), bringing the speed of rotation of the 

third shaft down to about 30 revolutions per minute. On the end 

of the third shaft a disk crank was mounted. A connecting rod 

joined one end of the walking beam with a short crankpin projecting 

through the faceplate. This pin was located off center on the faceplate, connected by a rod to the walking beam, and converted the 

rotary motion of the disk to reciprocating motion. Provision was 

made for changing the length of stroke by changing the pin in the 

faceplate to a position farther away from the axle. Ordinarily, drilling was done with an 11-inch stroke, at 30 strokes per minute.

The pump for jetting was a double-acting two-piston suction type 

rated at 100 psi, though somewhat greater pressures were produced. 

It was belt-driven by a 3-horsepower gasoline engine mounted directly 

above it.

In addition to the equipment described, several other items deserve 

special mention. The swivel, which connects to the string of hollow

FIGURE 3. Water for drilling is drawn by suction hose from third mud pit.
B-8 CONTRIBUTIONS' TO THE HYDROLOGY OF THE UNITED STATES

drill rods, consists of an inner perforated rod that can be rotated 

within a stationary outer shell and receives water from the hose 

through a suitable union (fig. 4). Thus, the rods may be rotated 

while the hose and outer shell of the swivel remain in a fixed position. 

A jetting bit was generally used on the lower end of the drilling 

rods; in contrast to cable-tool bits, most jetting bits are relatively 

light in weight. The weight of the string of 1-inch extra heavy rods 

used in jetting is ordinarily sufficient to provide good cutting action. 

During drilling, dual streams of water emerge 2 to 6 inches above the 

cutting edge of the bit to wash the sides and bottom of the hole. A

FIGURE 4. 'Swivel and drill rods alternately raise and fall In jet 

drilling while operator turns swivel in a clockwise direction, 

twisting at instant of impact.
JET DRILLING IN FAIRBANKS AREA, ALASKA B-9

variety of bits is available (fig. 5), but, in general, it was found that 

a bit with a Z-shaped cutting edge worked very well in unconsolidated 

material and a chisel-type bit worked best in schist.. A bit made from 

a sharpened piece of steel welded across a coupling also cut well, 

but lost gage rather quickly owing to the lack of body.

FIGURE 5. Bits used in jet drilling. A, Straight bit; B, Chisel bit; C, Z-bit; D, Offset 

bit; and E, expansion bit. Photograph courtesy of R. R. Howell Co.
B-10 CONTRIBUTIONS TO THE HYDRO'LOGY OF THE UNITED STATES

Because of the distribution of the weight of the rig, it could handle 

only eight 10-foot rods on a straight lift. Greater lift and stability 

could be gained by placing the machine close to or under the (near) 

derrick legs and bolting the two units together.

Clamps for holding and lifting drill pipe, heavy suction hose and 

flexible wire-wound jetting hose pulleys and sheaves, a drive block, 

wrenches, miscellaneous handtools, and several lengths of new ^4-inch 

or %-inch rope complete the drilling outfit.

DRILLING OPEN HOLE

When mud pits (fig. 3) have been dug and filled with water, a 

string of drilling tools, consisting of swivel, rod, and bit, is suspended 

in place by a rope that passes up through a sheave hung on the crown 

block of the tower and down and under the sheave on the walking 

beam. The rope is snubbed on a cleat on the frame or chasis of the 

pump and power unit (fig. 1). The next step in jetting is to start 

the pump and establish circulation. The engine that operates the 

walking beam is then started, the string of rods moves up and down, 

and, as line is slacked off, the bit strikes the ground and jetting begins 

(figs. 2, 4). Lacking a walking-beam mechanism, the rods may be 

given an up-and-down motion by alternately pulling and releasing, by 

hand, the drilling cable that has been wound several turns around a 

cathead (fig. 6). The initial length of rod is best guided from the 

ground rather than at the swivel head so that a plumb hole can be 

started directly beneath the crown sheave. At this stage, an expansion bit (fig. 5^), an oversized bit, or an offset bit (fig. 5Z>) may be 

used to advantage to produce a hole somewhat larger than the casing 

to be used.

Hole is made by a combination of cutting and washing action; 

greater reliance, however, was placed upon washing action. Efforts 

to speed up progress by more vigorous drilling action were not particularly successful; but in penetrating harder formations, for which 

the jetting method is not particularly adapted, progress depended 

almost entirely on the cutting action of the bit.

Drilling fluid used is ordinarily water to which mud or other 

thickening agent has been added. Such fluid carries out cuttings 

better than water owing to its higher specific gravity and by forming 

a mud cake on the walls of the hole, it reduces water loss and prevents 

caving. As drilling progresses, the level of water in the mud pits 

must be maintained; losses of water may be minimized by addition of 

small amounts of bentonite or drilling clay. If necessary, a fairly 

thin bentonite slurry can be thickened quickly by the addition of a
JET DRILLING IN FAIRBANKS AREA, ALASKA B-ll

little slaked lime. When the slurry attains the consistency of a very 

thin cream, it is too thick for use in silt; it might not, however, be 

too thick for drilling in loose sand where considerable loss of fluid 

occurs. When too thick, the drilling fluid recirculates mud and fine 

sand. This accelerates the wear on the pump plungers and pump 

cylinder linings. The amount of bentonite to be used is determined 

largely by experience. In the 1954 operations, 6 to 10 heaping handfuls were used at the start of drilling, and a few handfuls were added 

every hour or two or when water losses became excessive.

Drilling clay can be most easily mixed by sprinkling small amounts 

on the surface of a mud pit and agitating it with a high-pressure 

stream of water.

When the length of the initial rod has been drilled, the rods are 

suspended in the hole resting upon a suitable U-shaped clamp. The 

hole is then washed for 1 to 5 minutes to eject any wall material that 

caves, after wThich the rod is retracted slightly and suspended by a 

clamp under the lowyer nipple joint (fig. 4). Operations are facilitated by setting a length of oversized casing as soon as possible. 

Thus, if a well of 3-inch diameter is being drilled, a short length of 

casing of 4-inch diameter should be set. This will facilitate changing 

of the rods and yet permit an oversized 3-inch bit to be used until the 

uncased part of the hole begins to cave.

FIGURE 6. Lacking a walking beam or similar mechanism, rods or casing drive weight 

may be alternately raised and dropped by tightening amd loosening the rope wrapped 

around the cathead.
B-12 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

In drilling sand formations losses of water will be minimized and 

the walls of the hole less likely to cave if drilling clay is added to the 

drilling fluid. However, prolonged circulation of heavy drilling 

fluid may cake the walls and make it difficult to obtain water from 

sections of the hole that have become plastered with mud, at which 

time it will be desirable to set casing because caving of the walls will 

probably occur as the water is lowered by bailing or by test pumping. 

Casing an open hole in the unconsolidated formations also will be 

desirable if the drilling is to be discontinued for as short a period as 

a day, or if appreciable caving occurs frequently during the course of 

drilling.

After the rods have been clamped, the pump is shut off, the swivel 

is disconnected, and a new rod is added. The swivel and drill rods 

are then reconnected and suspended on the drill rope, after which the 

clamp is removed from the rods. The pump is then started, the string 

lowered in the hole, and drilling proceeds as before.

When rods are to be changed, they are raised manually and the drill 

rope is removed from the walking-beam sheave and snubbed on a cleat 

on a derrick leg. Similarly, after the new rod" is connected, the rope 

must be transferred from the cleat to the walking-beam sheave without allowing the rods to reach the bottom of the hole. The length 

of rods that can be held while these rope transfers are made is determined by the weight of the men available. As the weight of the 

rods increases, it may become impractical and even dangerous to make 

the transfer without using hoisting blocks. When drilling an uncased 

hole in caving material, the drilling rods should be retracted at least 

the length of one rod before disconnecting the swivel in order to 

minimize the danger of caving around the lower end of the string. 

The tower accordingly must be high enough to accommodate above 

ground the upper rod, the rod to be added, and the swivel.

Caution should be exercised in choosing drilling speed. The tan 

silt was cut so rapidly that a minimum gage hole resulted unless an 

expansion bit was used. A slower stroke of the rods and maximum 

pump discharge will wash the wall of the hole and effectively create 

a wider hole, and thereby premit easier setting of casing.

Drilling in black muck without using casing tends to create a large 

hole. It is probably better to case this material as drilling proceeds, 

but, if an uncased hole is desired, rapid stroke of the rods and minimum use of the jet stream seem most desirable.

It is possible and practicable to drill an uncased hole in hardpacked sand. It may be desirable in some instances to drill several 

feet ahead of the casing to wash the hole to a maximum diameter, but 

the danger of caving and of sandlocking the drill string is ever
JET DRILLING IN FAIRBANKS AREA, ALASKA B-13

present. It should not be attempted unless the jet pump is absolutely 

dependable.

There may be a tendency for a hole to deviate from plumb during 

drilling, particularly during fast drilling. If the hole is to be cased 

eventually, it is desirable to case the hole as drilling proceeds. Casing 

set in a hole will guide the drill rods, and the new hole drilled below 

casing that is plumb will likely be plumb also. In any event, particular attention should be given to the plumbness of the first two or 

three lengths of casing.

SETTING CASING

After drilling an uncased hole as far as desired, casing is set. All 

rods are removed from the hole and set aside. Depending on the 

height of the derrick, they may be disconnected at every second joint, 

or even third joint, and stacked.

Casing is lifted for setting in the hole by a separate line and hook. 

The end of the line by which the pipe is raised may be wrapped 

around the pipe or the hook may engage a rope, chain, or clamp 

device. Lifting ordinarily can be done manually if the casing is 

not more than 3 inches in diameter and 11 feet in length.

The first length of casing should be fitted with a drive shoe, preferably welded to the pipe. If a regular casing shoe is not available, 

a coupling lined with hard welded material may suffice. A tightly 

screwed-up coupling alone is better than nothing and may be sufficient 

for shallow holes in soft material.

The first few lengths of casing may slide down the hole of their own 

weight; therefore, clamps must be provided to prevent the pipe from 

falling out of reach (fig. 7). Clamps should be used as a safeguard 

until the pipe advances with difficulty. If the pipe fails to advance 

of its own weight, it may be rotated with a wrench; but care must be 

taken because the pipe may be released suddenly and fall the remainder of the length to the clamp.

DRIVING CASING

In most holes it will be necessary to drive the casing with a heavy 

weight. The drive weight (fig. 7) is a rectangular block with a center 

lengthwise hole, through which the drill rods pass. However, the 

side of the block is slotted to permit the drive weight to be placed in 

position without disconnecting the rods. Excessive wear on the 

striking surface may be eliminated by adding a steel faceplate. 

The separate line and hook used to handle the pipe may be used to 

pick up the drive weight. As the drive weight should weigh as much

577871 O «1 3
B-14 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATE'S

as 300 pounds, it is lifted by a rope over the cathead (fig. 6). A guide 

rod or a bar passing through the drive weight and into the casing 

is used to hold the weight in proper striking position. A short length 

of 1-inch pipe with a T-fitting or a specially made long pin passing 

through the weight will serve as a guide, or the weight may be guided 

by a short string of drill rods suspended from the crown block (fig. 7). 

Care must be exercised against failure of the guide rod or pin, for 

dropping the rod or pin into the hole will require a fishing job and 

may result in loss of the hole.

FIGURE 7. Drive weight in position to <Mve casing.
JET DRILLING IN FAIRBANKS AREA, ALASKA B-15

Driving can be done in two ways. If the casing advances easily, 

it will probably be preferable to lift and release the weight over the 

cathead, thereby giving a series of light blows and retaining maximum control of casing advance. Manual rotation of the casing may 

still be helpful at this stage. At some later stage casing may advance 

more slowly, and it will be desirable to operate the drive weight with 

the walking beam. It is possible by proper operation of the walking 

beam to apply sharp continuous blows, thereby setting up a continuous 

vibration of the casing, and the casing will advance rapidly, at least, 

at first.

In setting casing, earth material is jarred or sheared off the walls 

of the hole and the hole begins to fill; this material may even push 

up into the casing. Thus, it will almost always be more economical 

of time to discontinue driving and clean out the hole before the full 

length of the hole is cased.

With casing in place, an oversize bit cannot be used; an oversize 

hole, therefore, can be made only by using an expansion bit or offset 

bit (fig. 5), or by slow drilling and rapid washing. Upon resumption 

of jet drilling, if more casing is required, the long string of rods extending to the bottom of the hole need not be removed. The procedure 

to be followed under these conditions is outlined on p. B-16.

At some point casing advance may slow down, and the question 

arises as to the extent that casing may be driven without damage. 

This depends on many factors, such as the material being penetrated, 

the condition of the hole, the strength of the casing, the weight of the 

drive weight, and the length and number of strokes per minute. The 

answer can be determined only by trial and error. However, it was 

found that in medium sand at Anchorage, at a depth of about 100 

feet, 4-inch (11 pounds per foot) threaded pipe tended to telescope 

under hard continued driving with a 300 pound weight; telescoping 

could be minimized by use of heavier pipe or by using welded pipe in 

preference to screw-joint pipe. It was also concluded that cutting 

long threads on thin-wall pipe to make butt joints is not desirable; 

greater strength remains where normal threads with minimum cuts 

are used. In using pipe that does not make butt joints, extra effort 

should be made to secure an exceedingly tight joint.

In operations at Fairbanks, no difficulty was experienced in telescoping of 2- or 3-inch pipe with very hard driving. At one locality 

where hard sand was being cased off, 3-inch pipe was driven for about 

20 hours, advancing about 1-inch per 35 to 70 strokes of the drive 

weight. The pipe was of normal weight with normal-length threads. 

In 1949, when an observation well was being constructed by jetting 

and driving, at one stage 2-inch pipe was pounded all day without
B-16 CONTRIBUTIONS' TO THE HYDROLOGY OF THE UNITED STATES

damage, advancing only a little more than 1 foot in that time. However, although this pipe had standard threads, the couplings were 

reamed to allow the ends of the pipe to butt together inside the 

coupling to form butt joints. The drive weight weighed only about 

100 pounds and was operated by alternately tightening and releasing, 

by hand, the hoisting line which was wound several turns around a 

revolving cathead.

A general rule, to which there are exceptions, however, is that as 

long as the pipe moves it may be driven without damage. Attempting to drive casing when it has reached a solid obstruction may result 

in serious damage to the pipe very quickly.

SETTING CASING WITHOUT REMOVING DRILL RODS

Casing may be joined to a string of casing already in the hole and 

subsequently driven without removing a long string of drill rods 

from the hole.

Assuming that the hole has been drilled approximately one casing 

length or more deeper than the string of casing in the hole, and that 

the casing already in place protrudes to a foot above the surface, the 

procedure is as follows:

1. The string of rods in the hole is retracted until the bit is inside the 

casing.

2. The joint is then disconnected at the surface to free the swivel and 

one length of drill rod.

3. The remaining rods are suspended inside the casing in the hole by 

a clamp.

To pick up the piece of casing to be added, the swivel with one 

length of drill rod attached is lowered, the rod is pushed through the 

length of casing, and the casing is then tied against the swivel by a 

rope or chain. These are then lifted as a unit (fig. 8) and suspended 

over the hole.

The rod in the casing suspended over the hole is now coupled toi 

the rod projecting from the hole. If the rod within the suspended 

casing projects, it may be easily coupled to the rods already in the 

hole. If, however, the rod does not project, coupling the rod to the 

drill string may be difficult and even dangerous if the grip on the 

rod slips while it is being coupled. The operator should not reach up 

inside the suspended casing to bring the drill rods together, but a 

small tool or metal bar should be used to pry the sections into line. 

It should be apparent that, in any event, the drill rod fastened to the 

swivel must extend nearly to the end of the casing to complete the 

coupling.
JET DRILLING IN FAIRBANKS AREA, ALASKA B-17

The rods are tightened by holding the lower coupling and turning 

the swivel handle. The string of rods then is lifted, the clamp is 

removed, and the string is allowed to hang free. The piece of casing 

to be added, still fastened to the swivel, then is lowered into place. It 

is then untied from the swivel, and the coupling is completed. Rods 

are then raised several feet for clearance and driving is begun.

It is not necessary to remove the drive weight when casing is being 

driven as the hole is advanced, nor is it necessary to remove the weight 

to add more rods for drilling additional open hole. However, the 

weight must be removed when casing is added; therefore an open-side 

drive weight is more convenient than one that is a solid block, except 

for the hole through which the drill rods pass.

FIGURE 8. Lifting casing using swivel and one joint of drill rod.
B-18 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATE'S

SPECIAL PROBLEMS

If jet drilling is carried on extensively anywhere in Alaska, resistant earth formations will be penetrated sooner or later. The drilling of these formations will impose considerable strain on the light 

equipment used. Consequently, care must be used to avoid stressing 

the equipment beyond its normal capacity; otherwise, loss of time 

due to equipment breakdown will certainly result.

Short shank bits, such as are commonly available commercially, 

have a distressing tendency to break off at the joint. When this 

occurs, a fishing job will be necessary. Fishing jobs, though well 

planned, do not always recover lost tools. Tool breaking may be 

largely eliminated by welding the bit on a 3-foot length of double 

extra-heavy l^-inch hollow rod. A high-grade-steel reducer coupling should be used to connect the bit shaft with the drill rods. In 

the event that the drill rods should break out of the reducer coupling, 

the bit and shaft will rest upright, and the consequent fishing job 

should not be difficult.

The greatest point of weakness that appeared during long periods 

of hard drilling were at the lowest joint and at the 4-inch nipple 

between the swivel and first drill rod. It is suggested, therefore, that 

after each well is drilled, the last foot of the lowest rod should be cut 

off and the rod rethreaded, and the nipple below the swivel should 

 be replaced by a new one.

It also follows that all threads should be cut absolutely true and all 

joints made up well. Twisting on the swivel in a clockwise direction 

at the instant of impact during drilling operations will tend to keep 

the rod connections tight, in addition to increasing the cutting action 

of the bit.

Fishing for lost rods is accomplished by using a tapered tap made 

especially for the purpose. The tap is lowered into the hole at the 

end of a drill pipe or rod. By careful handling it is usually possible 

to insert the tap in the upper end of the hollow rods. After engagement the tap is turned carefully to cut a thread in the rod. After it 

is connected together, the tap is raised with the string of rods attached.

Forging bits to maintain gage and sharpness was found to be 

expensive and generally unsatisfactory. Use of hard-surface weld 

material on cutting edges and at outer wear points was relatively 

cheap and satisfactory. Use of a bit not up to gage is poor practice 

and ordinarily leads to difficulty.

The height of the tower is an important factor in obtaining satisfactory drilling progress. If the tower is not high enough, standardlength drill rods or casing cannot be handled efficiently. The minimum height that is satisfactory is equal to the length of the casing
JET DRILLING IN FAIRBANKS AREA, ALASKA B-19

used (ordinarily less than 11 feet in half-lengths), the length of the 

swivel and nipple (about 3 feet), the distance between the bottom of 

the sheave and the crown block (about 2 feet), plus a working distance of 4 feet, or a total of 20 feet.

Extra operations may be required where casing follows the hole 

closely; unless the total length of rods is only slightly longer than the 

full length of the casing, substitution of rods or casing, cutting off of 

casing, or other time-consuming operations are involved. Such difficulties can commonly, but not always, be avoided by anticipating the 

lengths of casing and rods that will be needed.

When subsurface conditions require that casing be advanced as the 

drilling progresses, a higher tower and use of shorter lengths of casing 

and rods will eliminate most of the potential difficulties; but the desirability of a high tower must be balanced against its increased weight 

and the greater difficulty in erecting it. The tower used in Geological Survey drilling was somewhat cumbersome and awkward and 

even a little dangerous to erect. Unskilled personnel required 2 to 4 

hours to set it up. Efficient production work would require that a 

derrick be erected safely by one man in half that time. Weight could 

have been reduced somewhat by planing down the rough 4- by 4-inch 

derrick legs and by using lighter braces, but time was not taken to 

test the advantage of thus decreasing the weight. Suggestions are 

made below for other types of towers to suit various needs.

A minor problem in the Fairbanks area is the large amount of 

organic material in the tan silt. This tends to clog the intakes of 

the suction line and the pump (fig. 3). Common window screening 

was used successfully as a filter in the circulating drilling fluid, but 

in at least one location much of one man's time was required to keep 

the screen clean.

Drilling in loose water-bearing sand may be very difficult. Marked 

losses of water that may occur may be minimized by thickening the 

drilling fluid with clay. However, the clay thus introduced may be 

difficult to remove in developing the well. Therefore, in drilling 

loose sand it is advisable to follow the hole very closely with the 

casing, drilling only a few inches before driving casing. It may even 

be necessary to reverse the procedure and drive the casing ahead of the 

hole; but this generally is a slower operation and, because it imposes a 

greater stress on the casing, is to be avoided if possible.

Large boulders are the nemesis of jet drillers. Boulders as large 

as 4 to 5 inches in diameter may stop the advance of casing; but with 

continued alternate drilling, washing and driving, they may be moved 

aside. Glacial till, locally known as hardpan, which is common in 

many places in Alaska, generally is a tough coherent material. In
B-20 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

this material it is generally very difficult to sidetrack even small 

boulders. If the casing can be retracted upon reaching a boulder, or 

if the boulder is discovered ahead of the casing in open drilling, it is 

advisable to break it up by blasting. The use of light cable tools to 

break up boulders is not particularly desirable, unless a combination 

cable tool-jet rig is used. Instead, the cutting power of the drill 

rods may be increased by adding weights to the uppermost drill rod.

DEVELOPMENT AND TESTING OF WATER-BEARING

DEPOSITS

Water-bearing deposits may be recognized (a) by inspection of 

the cuttings brought up with the drilling fluid, (b) by a high rate of 

loss of water from the mud pits, or (c) by discharging water from the 

hole by one method or another.

Sandy formations, particularly coarse gravelly sands, generally 

yield water readily to wells. Marked losses of water in the mud pits 

will generally occur when coarse sands are penetrated, unless the drilling fluid is very thick. In some instances, bailing or pumping will 

quickly establish the water-yielding character of the formation. 

Other sands may be difficult to develop and will require bailing, pumping, and agitation for long periods before they yield appreciable 

amounts of water.

Although a deep uncased hole in unconsolidated formations may 

be drilled successfully by the jet method, lowering of the water in 

the hole to below the static level will promote caving of the walls; 

therefore, the hole should be cased to the water-bearing formation 

before testing is begun.

Some sand deposits will not yield water, or will yield only small 

amounts unless a well screen is used. Where an open hole can be 

drilled ahead of the casing, the screen can be simply lowered in place. 

However, where sand deposits will not stand open, the most practical 

method to set the well screen is to advance the casing to the bottom 

of the water-bearing formation, lower the screen, and then retract the 

casing to expose the screen. Another useful technique is to wash 

the screen down into the loose deposits below the casing on a 1-inch 

wash pipe that passes through a one-way valve at the bottom of the 

screen and is connected by a reverse-thread joint. After the screen 

is set, the wash pipe can be disengaged and removed.

Where casing is 2-inches in diameter, the screen should be fitted 

with an extension of blank pipe that extends well up inside the 2-inch 

casing. Where 3-inch or larger casing is used, screen with a lead 

collar at its upper end will probably be more satisfactory. When .such 

a screen has been placed, the lead collar may be swedged out against
JET DRILLING IN FAIRBANKS AREA, ALASKA B-21

the casing to make a seal. " In any event, after placement of the 

screen, rapid pumping may be sufficient to develop the well. If this 

is not successful, the well may be developed further by pouring water 

into it, or by agitating with a surge block or by compressed air. 

Sand that accumulates during development may be removed by bailing or perhaps, preferably, by running in the drill rods and washing.

For detailed information on the function and use of screens and 

development of wells, the reader is referred to several excellent publications on the subject (Bowman, 1911, p. 98; Johnston, 1951, p. 25; 

Stewart, 1934, p. 25, 48; U.S. War Dept. 1943, p. 192; U.S. Bur. 

Yards and Docks, 1943, chap. 12, p. 16; Bennison and Bollenbach, 

1947, p. 219, 233). Some manufacturers of well screens have published 

this information in pamphlet form.

In jet drilling in bedrock, such as the weathered zone of the Birch 

Creek schist, marked losses of water may occur, suggesting that a 

water-bearing formation has been penetrated. Flushing with fresh 

water or removal of the rods and bailing the hole dry may show that 

the hole has not yet reached the zone of saturation. Careful measurements of the water level, or by the absence thereof, following a 

period of rest (that is, overnight) will show whether or not the 

zone of saturation has been reached. To avoid marked losses of 

water in weathered schist above the water table and therefore to 

be better able to observe drilling-water losses below static level, it 

is desirable to seat casing tightly at some point below the water level, 

as will be possible in many places. In fact, considering the fragmental nature and included granular and clayey material of much 

of the schist, it will probably be desirable to case off to as great a depth 

as possible.

Although water-bearing formations below the water table ordinarily 

may be recognized by losses of water from the mud pits, it is advisable 

to stop drilling and bail or pump the well occasionally to ascertain 

whether water-bearing formations have been penetrated. The most 

efficient time to make such a check is at the end of each day's work, 

because some of the drill rods will have to be withdrawn anyway 

to eliminate the possibility of their being buried by caving overnight. 

An accurate measurement of the water level and further testing, if 

necessary, can be performed the following morning.

Where the water level lies within suction lift of the surface (about 

20 feet), the well may be tested by discharging water without pulling 

all the rods by pumping through the rods. The rods should be retracted at least 20 feet to avoid the danger of clogging the bit or 

sandlocking the string of rods in the event sand is drawn up into the 

well.
B-22 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

Where the static level is more than 20 feet below the surface, testing can be done by bailing, or, if a longer test and more accurate 

data are desired, by pumping with a force-type pump.

Bailing can be done manually, by handling the bailer with a rope 

through the sheave in the crown block. Lifting the bailer with the 

cathead was found to be impracticable on the rig used, because the 

light rope used twisted and tended to wrap around the cathead. 

Where the depth to water is more than 30 or 40 feet, manual bailing 

is slow, hard work, although not entirely impractical. A reel for 

taking up and paying off the bailer line, preferably a thin steel cable 

rather than a light rope line, which could be run by the power engine 

by means of an idler pulley arrangement, would be most helpful.

TEST HOLES DRILLED IN 1954

The drilling of test holes in 1954 will be briefly summarized. The 

conditions found in the drilling of these holes may be considered 

typical of those found in the submontane area north of Fairbanks. 

USGS test hole 11 was drilled on the north side of the Chena Hot 

Springs Road, about one-eighth mile east of the Steese Highway. 

The drilling site was on a saddle, or pass, in a low mountain ridge 

where data on depth to bedrock and the possible presence of deeply 

buried sand were sought.

Tan silt was found to extend to a depth of 54 feet, at which point 

Birch Creek schist was penetrated. While using a 3-inch Z-bit the 

drilling rate in silt averaged 3 minutes per foot. The hole was continued to a depth of 112 feet in weathered schist in which quartz veins 

were present at 67, 74,92, and 112 feet. Because the siliceous material 

(quartz) was cut slowly, as little as 1 inch in 20 minutes, the overall 

drilling rate in weathered rock averaged 20 minutes per foot. The 

hole was stopped in siliceous rock at 112 feet depth. The casing 

advanced easily to 54 feet and with light driving was extended to 70 

feet.

USGS test hole 12 was drilled on the northeast corner of the 

Chena Hot Springs Road and the Steese Highway, high on the slope 

below the pass where hole 11 was drilled. Data on depth to bedrock 

and the possible presence of deeply buried sandy beds were sought.

In this hole tan silt extended to a depth of 84 feet. Below this, 5 

feet of very soft schist was penetrated, and then 11 feet of harder 

schist.

The drilling rate in the silt, using a 3-inch Z-bit, was 2 minutes per 

foot. The drilling rate in the schist, using a 2-inch chisel bit, was 20 

minutes per foot. Open-hole drilling was done in this well, and caving in the lower part of the silt, below the static level of 56 feet, began
JET DRILLING IN FAIRBANKS AREA, ALASKA B-23

a few hours after the hole was completed. The hole was then reamed 

with a 4-inch bit to a depth of 80 feet, and 3-inch casing was set without difficulty.

The well was tested with a cylinder pump for iy2 hours at a rate 

of 3 gpm at 19 feet of drawdown, but clear water was not obtained 

because the casing was not seated on bedrock.

Test hole 13 was drilled at the Bushey Farm on the Steese Highway 

where it crosses the head of a small valley extending back into the 

mountains (fig. 2). Data on the presence of deeply buried sands or 

gravels in this valley were considered of particular importance to the 

investigation.

Black muck extended from the surface to a depth of 96 feet, below 

which 4 feet of medium-gray sand and 8 feet of Birch Creek schist 

were penetrated. The ground was frozen from 7 to 42 feet below the 

surface.

The drilling rate in the unfrozen black muck averaged 1% minutes 

per foot, but drilling in frozen muck was slower, averaging about 3 

minutes per foot. The progress in drilling permafrost seemed to be 

almost entirely a function of the thawing action of the drilling fluid. 

In addition to thawing the bottom of the hole, the circulation caused 

thawing of the walls above and a large irregular hole was created. 

Better progress might have been made by casing off the frozen ground 

at intervals as soon as enough hole had been made to admit a full 

length of casing.

The drilling rate in the sand and bedrock was much greater, about 

15 minutes being required per foot of penetration. When the sand 

was reached, a string of 2-inch casing was literally dropped in the 

hole, and the well was tested. The test efforts were unsuccessful; it 

seems that the fine material present choked off such water as might 

otherwise have been available. However, when the hole reached a 

depth of 108 feet, having passed through 8 feet of yellow, fragmented, 

and sandy weathered rock, the well began to flow at the rate of about 

5 gpm, at a discharge level 4 feet above land surface. The well was 

subsequently pumped at a rate of 20 gpm at a pumping level of 7 

feet below land surface (drawdown of 14 feet).

Test hole 14 was located on the north side of the Farmers Loop 

Road in the SE^NW1/^ of sec. 22. The site chosen was on an alluvial 

slope between two major valleys leading back toward a mountain 

ridge. The depth to bedrock, believed to be slight, was of particular 

interest here as was the presence of deeply buried sands.

The hole was drilled without casing through 183 feet of tan to gray 

silt to bedrock to a depth of 184 feet. No appreciable sand was found 

at the base of the silt sequence. The drilling-time rate averaged iy2
B-24 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED- STATES

minutes per foot, and in 1 day 145 feet of hole was drilled. Even so, 

more than half the time was spent in operations other than drilling. 

A heavy bentonite slurry was used to hold the hole open during drilling. After bailing in an attempt to determine static level, the hole 

caved and was abandoned.

Test hole 15 was drilled off the Farmers Loop Road in sec. 23, 

SW^NE^, in a small stream valley extending back into the mountains. Data on the presence of deeply buried sands and depth to 

bedrock were sought at this locality.

Tan and gray silt, including a coarse sandy zone at 103 to 109 feet, 

was penetrated to a depth of 137% feet. Medium sand extended from 

137% to 143 feet and medium-coarse sand from 143 to 164% feet. 

Below this, 13% feet of silt and 1 foot of fine sand were penetrated. 

The total depth was 179 feet. The drilling rate in the upper silt was 

114 minutes per foot, but in sand it was 18 minutes per foot.

The hole was cased with 3-inch casing and, except for the first 40 

to 50 feet, casing was advanced with difficulty. The last 30 to 40 feet 

of casing advanced very slowly, requiring as many as 64 blows with 

the drive weight to advance it an inch. The reasons for this difficulty 

are believed to be (a) the hole was somewhat crooked owing to fast 

drilling, (b) the hole had not been enlarged appreciably by washing 

action because of fast drilling, (c) and sandy material in the 103- to 

109-foot depth zone tended to follow the pipe and build up skin 

friction.

Time was not available for testing, but, judging from losses of 

water from the mud pits and the appearance of the cuttings, the 

medium-coarse sand between 143 and 164% feet should have yielded 

water if development procedures had been applied.

SUMMARY OF TEST DRILLING

Investigations carried out by the Geological Survey in 1954 showed 

that the unconsolidated formations on the submontane slopes north 

of Fairbanks could be penetrated quickly and easily by the jet 

method of drilling. As experience was gained in operating the rig, 

the average time required to penetrate silt deposits decreased from 

3 minutes per foot at the beginning of the season to 1% minutes per 

foot near the end of the season.

Drilling in bedrock appeared practicable and was reasonably rapid ; 

a total of about 82 feet of rock was drilled at an average rate of 15 

to 20 minutes per foot. Quartz or quartzose rock was penetrated 

only with difficulty.

Unfrozen black muck was drilled somewhat more quickly than tan 

silt; and 35 feet of frozen muck drilled in the 2-month period was pene-
JET DRILLING IN FAIRBANKS AREA, ALASKA B-25

trated without difficulty, requiring about 3 minutes' drilling time per 

foot. The drilling rate in hard-packed sand was comparable to that 

in rock.

USE OF THE JET METHOD OF DRILLING

In considering the applicability of the jet method of drilling in 

the Fairbanks area, the following aspects of this method seem most 

important:

1. The speed of drilling progress is great where conditions are 

favorable.

2. The method may be used effectively in several greatly different 

geologic environments.

3. Holes of any diameter up to 4 inches may be drilled easily, and

4. Modern well screens may be set and the well developed to optimum 

yield.

5. Where conditions are especially favorable, simple equipment as 

described in this paper can be used successfully for the construction of wells.

6. Production drilling, or any kind of difficult or deep drilling, may 

necessitate the use of a commercially built machine that will 

provide greater ease and speed of operation and greater safety 

to the operator.

The writers believe that in the Fairbanks area and other places of 

similar geologic conditions, jet drilling of small-diameter wells will 

be practical. Furthermore, the speed of drilling generally will not 

be slower than that of the cable-tool method, and in many places jet 

drilling will be considerably faster.

The experimental work of the Geological Survey in the Fairbanks 

area shows that the jet drill is effective in the construction of wells 

and test holes in many different types of earth material. Silt and 

muck formations are penetrated with ease. However, not as much 

is known about rock drilling as might be desired. Although much 

of the weathered schist of the Fairbanks area is penetrated easily, 

relatively thick hard layers of rock might be difficult to penetrate 

with the jet drill, although not necessarily more difficult with lightweight cable-tool equipment.

Drilling in the sandy sediments of the valley flats in Fairbanks 

may be entirely practicable. The method may not be notably more 

efficient than the drive-jet method of drilling wells of 2-inch diameter 

now carried out extensively in the area (Cederstrom and others, 1952, 

p. 19). With a jet drill built to deal with the wide range of conditions existing on the slopes and hills, it may be found entirely
B-26 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

practicable to drill wells of 2-, 3-, and 4-inch diameter in the valley 

flat areas also.

Drilling on the valley flats in frozen or unfrozen sandy ground 

will necessarily be relatively slow it may be recalled that at test 

hole 15 an average of 18 minutes was required to drill each foot 

of a hole of 3-inch diameter in hard-packed sand. Jet drilling at 

Anchorage in 1951 indicated that a 4-inch hole might be drilled in 

sandy ground at the rate of from 15 to 30 feet per day when working 

within 100 feet of the surface, including the setting of 4-inch casings. 

It is thought that the drilling of frozen sandy ground will not be 

more difficult than that of thawed sandy ground; in fact, it may be 

less difficult because caving can be reduced to a minimum if the 

casing follows the hole rather closely.

The advantage of using the jet drill, described in this report, on 

the valley flats is its versatility. Holes as large as 4 inches in 

diameter can be drilled with relative ease, thus permitting the use 

of large pumps or, if necessary, permitting relining with smaller 

diameter pipe. The casing installed is open at the bottom, and screens 

of optimum length and slot size may be placed if desired.

PRODUCTION DRILLING

Generally, professional drilling will demand that the best equipment available be used in order that the time factor be reduced to 

a minimum. It is pointed out that modern jet-drilling machines are 

available commercially. These machines are truck- or trailermounted, with a folding steel mast that can be quickly raised and 

lowered. Lever controls are so situated that one man alone can 

perform most operations called for in sinking a well.

However, in some instances, conversion of a cable-tool rig already 

on hand may be practicable by the addition of a relatively inexpensive jet pump activated from a power takeoff on the rig.

Drive-jet outfits in use might be converted to reasonably efficient 

jet drilling with little expense, provided that the engine has adequate 

horsepower and the pump can deliver turbid water at a pressure of, 

perhaps, 50 pounds per square inch or more. Lacking sufficient 

horsepower, excessive gearing down of the engine may be necessary 

and operations may be slower because more block-and-tackle operations will be necessary.

A drilling outfit of the type used by the Geological Survey might 

not be quite practical for production work. Certainly, it would be 

desirable that the entire outfit, including a more easily raised derrick, be trailer- or truck-mounted and that a reel with appropriate 

controls be provided for running a bailer. It should be pointed out
JET DRILLING IN FAIRBANKS AREA, ALASKA B-27

that a separate engine to operate the pump is not necessary, though 

it is desirable to insure good drilling circulation in times of difficulty. 

A jet-drill power unit presently in use in eastern Virginia has both 

pump and walking beam activated by one engine. The pulleys are 

double, one fixed to the pump shaft and one free. By sliding the 

belt from one pulley to another, a clutch arrangement is achieved. 

In the final analysis, what can be used successfully will be decided 

by many factors, chief among which is the cost of the equipment, 

the ingenuity of the driller, and the manner in which he decides to 

conduct his business.

SIMPLE DRILLING EQUIPMENT

Simple jet-drilling equipment can be used where only one or a 

few wells are to be drilled, provided the time required to drill is not 

an important factor and conditions are especially favorable.

One individual in the Steele Creek area was able to wash a %-inch 

pipe down 149 feet in less than 2 days' working time. A simple 

electrically operated household piston pump was used for circulating 

the drilling water. No derrick was used and the wash pipe was 

twisted manually as required, in order to advance the hole. The well, 

which was cased with 2-inch pipe, flows about 5 gpm. Practically all 

the drilling was done in blue muck. The ease of drilling in this 

instance should not be regarded as a criterion of what will commonly 

be penetrated in the submontane area north of' Fairbanks. Holes 

to a depth of 150 feet generally cannot be drilled with such simple 

equipment where ground conditions are at all difficult. Such areas 

normally require the use of proper equipment in the hands of a skilled 

operator.

GEOLOGIC TEST DRILLING

The results of Geological Survey test drilling in the Fairbanks area 

indicate that the jet method of drilling, in addition to being a practical method of constructing water wells in many places, is well suited 

for certain types of geologic investigations. Uncased 2-inch holes 

can be drilled easily in the unconsolidated silty sediments, and where 

exploration is concerned primarily with depth to bedrock or frozen 

ground or the type of alluvial material present, holes can be put down 

quickly and cheaply.

Samples of drill cuttings collected in jet drilling are not as representative of the formations as cable-tool samples, but are adequate 

for many types of study. Although the desirability of test holes for 

ground-water exploration may not be apparent, in many places it 

might be desirable to drill a number of small-diameter holes to locate
B-28 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED. STATES

and determine the maximum thickness of water-bearing deposits before constructing an expensive production well. Such holes, especially where casing is not needed, can be drilled by jetting at small 

expense. The information gained would, first, provide assurance 

that an expensive large-diameter well would be successful and, second, 

would enable contracts to be prepared on the basis of a detailed 

summary of formations to be penetrated in the production well. 

Furthermore, the method by which the well was to be constructed 

and finished could be specified with greater assurance.

Holes of somewhat larger diameter required for special purposes 

can also be drilled without casing and will remain open long enough to 

permit the installation of special devices, as, for example, recording 

temperature.

Investigation of building foundations could be carried out economically and quickly in many places by putting down jetted holes. The 

type of material present, the thickness of unfrozen and frozen ground, 

and the depth to bedrock could be determined with ease; and if special 

equipment is utilized, cores may be taken where required.

REFERENCES CITED

Bennison, B. W., and Bollenbach, W. M., 1947, Ground water, its development,

use, and conservation: St. Paul. Minn., Edward E. Johnson Co., 509 p. 

Bowman, Isaiah, 1911, Well-drilling methods: U.S. Geol. Survey Water-Supply

Paper 257,139 p. 

Cederstrom, D. J., 1952 Summary of ground-water development in Alaska, 1950:

U.S. Geol. Survey Circ. 169, 37 p. 

Cederstrom, D. J., Johnston, P. M., and Subitzky, Seymour, 1953, Occurrence

and development of ground water in permafrost regions: U.S. Geol. Survey

Circ. 275, 30 p. 

Johnston, C. N., 1951, Irrigation wells and well drilling: California Agr. Expt.

Sta. Circ. 404, 30 p. 

Mertie, J. B., Jr., 1937, The Yukon-Tanana region, Alaska: U.S. Geol. Survey

Bull. 872, 276 p. 

Stewart, G. I., 1934, The use of shallow wells in forest fire suppression: Michigan

Forest Fire Expt. Sta., 64 p. 

U.S. Bureau of Yards and Docks, 1943, Handbook on ground-water supply:

Washington, U.S. Navy Dept, chap. 12, 43 p. 

U.S. War Department, 1943, Well drilling: Tech. Manual 5-297, 300 p.

o