Water Stewardship

Guidelines for Minimum Standards in Water Well Construction, Province of British Columbia — June 1982

APPENDIX 8: PERMANENT WELL, TEST WELL AND TEST HOLE ABANDONMENT

1. Introduction

Permanent well and test hold abandonment means that the well should be filled in such a manner that vertical movement of water within the well bore, or the annular space surrounding the casing is effectively and permanently prevented and the water is permanently confined to the specific zone in which it originally occurred. Unsealed abandoned wells may be a hazard to public health, safety and welfare and to the preservation of the ground water resource. A well needs to be checked first before it is sealed to see that there are no obstructions to the sealing operation. Removal of well screens, liner pipes or casings may be necessary in some cases to obtain a permanent seal. Casing opposite zones which cannot be readily removed must be split with a casing ripper to insure subsequent sealing by grout above, and where applicable below, the aquifer zone. Unless the annular space around the outside of the casing was cemented when the well was drilled, the upper portion of the casing should be removed to prevent surface water from entering the water-bearing strata by following down the casing.

2. Flowing Artesian Wells

A flowing artesian well, particularly if water is escaping around the outside of the casing to surface or even to another formation, needs very special attention. First a permanent cement seal should be placed between the casing and the points from which the water is escaping. However, to do this the flow must first be stopped and the water level lowered in the well. This can be accomplished by:

1. Pumping the well and drawing down the water level.
2. Pumping adjacent wells and drawing down the water in the artesian well.
3. Using high specific gravity fluids to stop the flow./li>
4. Where there is a particularly large flow, special measures may have to be taken. These include large stone aggregates (not more than 1/3 the diameter of the hole), steel shavings.

A well packer or a bridge can be used to restrict the flow at the bottom of the confining zone and this enables the appropriate sealing material (usually neat cement or sand and cement grout piped under pressure) to be placed above it.

3. Placement of Grout

Cement grout, sand and cement grout or concrete used as sealing materials in abandonment operations should be placed by the use of grout pipe, tremie, cement bucket or dump bailer in such a way so as to avoid segregation or dilution of the sealing materials. Dumping from the well head should not be permitted. Where seals are to be placed within casing, liners, filter packs, etc., only neat cement with maximum 5% by weight bentonite clay should be used, and the casing liner, etc., should be first thoroughly perforated or ripped. Elsewhere seals intended to prevent vertical movement of water in the well or bore hole can be cement, sand and cement or concrete. Minimum cement seal length where dimensions permit should be 10 feet.

4. Placement of Fill

Above an aquifer the non-producing zones can be filled with sand, sand and gravel, cement and sand or concrete. Non-producing zones above the uppermost aquifer seal should be filled with materials that are less permeable than the surrounding formations.

It is recommended that the uppermost 5 feet of the bore hole to land surface be filled with material suitable to the intended land use.

5. Special Conditions

Mineral exploration holes, dewatering wells, temporary service wells, etc. should also be abandoned according to the above stated standard for water supply wells.

6. Records

All information relative to the abandonment procedures and methods, the location of the abandoned well, should be recorded on the well record form and copies supplied to the owner and also to the Ministry of Environment.

7. Conclusions

Because of the complexities involved in some cases of well abandonment, each one should be considered as an individual problem and the design, construction of the well and the hydrogeology must be considered and studied before final selection of materials, methods and procedures can be finalized. It would be wise where there is doubt as to the well construction or the hydrogeology to adopt those materials and procedures which will give the greatest possible chance for a successful and permanent sealing operation.

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