US2646129A

US2646129A - Well construction

Info

Publication number: US2646129A
Application number: US7870A
Authority: US
Inventors: James M Dunn
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-02-12
Filing date: 1948-02-12
Publication date: 1953-07-21
Anticipated expiration: 1970-07-21

Description

July 21, 1953 J. M. DUNN WELL CONSTRUCTION Filed Feb. 12. 1948 INVENTOR. L/amee [Z flunrz BY Affff.

Patented July 21 1953 James M. Dunn, Sandpoint, Idaho Application February 12, 1948, Serial No. 7,870

My invention relates to improvements in well drilling in quicksand formations.

In many parts of the country the matter of drilling shallow wells for a water supply has been a difficult problem because the water supply is found in a sand formation where the sand is of such fineness and uniformity that flow into a well hole of reasonable diameter is not sufficient.

Modern pumping equipment on the farms is capable of lifting a large volume in a short time. This makes it imperative to have a relatively large reservoir of water on hand for the pump. In the sand formation casing is necessary to prevent caving. If water flows into the well only from the bottom, the fine sand carried with the water and material in solution in the water tend to settle on the bottom during periods when the .pump is not operating and soon seal off the water I am aware that methods have been patented for placing gravel layers around perforated casing in wells. In allsuch cases of which I am aware howeventhe well casin is perforated before being put in the well and the manner of providing the filter bed of gravel differs in essential respects from my method. I r

It is the principal purpose of my invention to provide a method and means for producing a shallow well in water carrying uicksand, whereby an adequate water reservoir is maintained and the sand is not subjected to such forces as to cause it to flow into the reservoir.

The nature and advantages of my invention will appear more fully from the following description and the accompanying drawings, illustrating a preferred form of the invention as applied to two common conditions encountered in Well drilling.

In the drawings:

Figures 1, 2 and 3 illustrate diagrammatically the steps of producing a Well in a water bearing sand formation.

In the soil formations that give difficulty to well drilling because of the quicksand, formations are commonly encountered where the water bearing sand is covered with a layer of clay or other soil thatwill .notcave readily. This type of'formation is illustrated in Figures 1 to 3 inclusive, where the water bearing quicksand is shown at it) and the covering layer, which will vary greatly in depth, is illustrated at I I.

Referringnow to Figures 1 to 3, the initial step is to drill the well hole large enough to take the casing employed. In the locality where I operate it is common practice to use a casing of about 2 Claims. (01. 166-26) around the casing at 20.

two foot diameter in sections of about three feet length. This part of the hole is drilled until the water bearing sand layer is reached. This part of the Well is indicated at I 48 in Figure 1. The next step is to apply a reamer to the drill and, at a level several feet above the sand, begin reaming out the hole soas to provide an enlargement of several inches thickness in the lower portion of the'hole in the clay. This portion of the well is indicated at 5. The depth and diameter of the reamed out portion IE will depend upon the circumstances in any particular well. However, a depth of ten feet is generally sufficient.

The casing sections I6, I! and [8 are now lowered into the hole, with the bottom section resting in the sand. A conical cap 19 is set upon the top section and coarse material such as crushed stone or gravel is poured into the hole around the casing sections until the reamed out portion I5 is filled as nearly as'possible to the top of the casing. The cap 99 is then removed and casing sections are added to complete the casing to ground level. Next a drill of the same size as the inner size of the casin is let down and utilized to remove the sand within the easing. Initially as the sand within the casing is removed, some of the sand around the casing flows inward and enlarges the cavity somewhat The gravel will flow down into this cavity but not sufiiciently to form a proper filter'bed. As the casing sections are lowered, additional casing sections are added, thus increasing the weight of casing and forcing it further into the sand. The sand within the I casing is removed and the lowering of the casing is continued until the desired depth of reservoir, below the top of the'sand layer, is provided. This may necessitate letting the casing down as much as fifteen feet into the sand.

During the lowering of the casing the bottom section of the casing is held from sinking faster than desired by cables or wires 2|. When the proper final level is reached these cables are anchored to the top section of casing so that the casing sections are prevented from spreading. The joints between casing sections are lapped as shown by the

flanges

22 and 23. Suitable caulking is used to seal the joints. The cables or wires 2! must be placed on the outside, as shown in Figure 2, in order that the auger drill can be operated.

Finally, after the casing is completed, small holes 25 are bored in one of the casing sections which is located at the proper distance below the water level. Normally the holes are provided the level of the holes 25.

about three feet below the water level. When the holes are bored sand first runs in through them with water. This creates a hollow around the casing for the gravel to move down. Sand will continue to flow out of the holes until the gravel fills around the holes to form an adequate filter bed.

When the well is put into use, the pump will have the large reservoir within the casing below the top of the sand level to draw on. As the water level drops, due to withdrawal by the pump, water will flow into the casing through the holes 25. Enough of these holes are provided to give a fairly heavy flow. However, even if the water level in the casing is lowered by the pump to a substantial distance below the holes 25, the pressure forcing the water through the holes 25 is not increased beyond the pressure that develops as soon as the water level in the casing falls below the level of the holes 25. It is evident that, as soon as the water level in the casing uncovers all of the holes 25, the pressure diiferential is the difference between the pressure at the outside end of a hole and atmospheric pressure in the casing at the level of the holes. If the pump uses up some of the water in the casing below the level of the holes 25 this will not decrease the atmospheric pressure in the casing at Therefore, the pressure forcing the water through the holes 25 does not increase further as the water level in the casing gets farther below the level of the holes 25. Of course, if the level of water within the casing is above the level of the holes 25 the pressure forcing water through the holes will be less than if the water level is at the level of the holes 25. The lateral flow of water by gravity through the gravel will not carry any appreciable amount of sand into the casing. The flow of water into the well through the holes 25 appears to improve with use of the well, probably because the flow establishes channels that extend out for some distance in all directions from the casing. Any sand that flows in through the holes 25 settles to the bottom of the Well and causes no trouble. I find that best resultsare obtained by using a sharp gravel or crushed stone. In some areas the sand is so fine and uniform that it cannot be trapped by smooth well rounded gravel particles to a sufficient extent to prevent undesirable flow of sand into the well. However, I have been able to handle this condition by proper selection of gravel.

It is believed that the nature and advantage of my invention will be clear from the foregoing description.

I claim:

1. A well drilling method for providing wells in water bearin quicksand which comprises drilling the well of casing size to the water bearing layer of uicksand, enlarging the lower portion of the well by reaming immediately above the water level, lowering imperforate casing sections into the well and suspending them to rest in the uicksand and extend below the reamed out opening, building up the casing to a height just below the top of the reamed out portion of the well, covering the casing, pouring a body of gravel in the space around the casing formed by the reaming operation, removing the cover and adding casing sections to the top of the well, and, with the casing sections in place and stationary, removing quicksand at the bottom of the casing, thereby causing water bearing quicksand around the bottom of the casing to cave inward and part of the gravel body in the enlarged portion around the suspended casin to flow down and spread into the caved area, then lowering the casing, adding casing sections at the top, as the lowering progresses, until a substantial storage space for water is cased in below the caved area, and providing a band of small openings in the wall of the casing located near the top of the storage space but below the water level, draining sand and Water from the surrounding area through said openings and thereby causing the gravel to flow down into the area around said openings and form a filter bed.

2. A well drilling method for providing wells in water bearing 'quicksand which comprises drilling the well of casing size to the water bearing layer of quicksand, enlarging the lower portion of the well by reaming immediately above the water level, lowering imperforate casing sections into the well and suspending them to rest in the -quicksand and extend below the reamed out opening, building up the casing to a height just below the top of the reamed out portion of the well, covering the casing, pouring a body of gravel in the space around the casing formed by the reaming operation, removing the cover, completing the casing, and, with the casing sections in place and stationary, removing quicksand at the bottom of the casing, and. lowering the casing, adding casing sections at the top, as the lowering progresses, until a substantial storage space for water is cased in below the caved area, providing a band of small openings in the wall of the casing located near the top of the storage space but below the water level, draining sand and water from the surrounding area into the storage space thereby causing the gravel to move down into the area around the openings, and tying the top and bottom casing sections together to prevent separation of casing sections by subsequent settling of the .lower sections.

JAMES M. DUNN.

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