However, within generally used whenever the clearance through the the compaction zone itself, the frictional hold collapsed zone will permit. The procedure is of the formation on a long liner permits transfer simple and relatively inexpensive. The sand fiL of compressive forces to the liner which will ul- is cleaned out with oil, water, or oil-base mud timately result in liner collapse. If the test is satisfactory, slot- As mentioned previously, there are two dis- ted screen liner is run, washed with oil, and the tinct types of compaction collapse, that within liner packer set.
The advantages of this method the producing zone and that in a compaction zone are obvious, but there are certain disadvantages. The problem of are applicable to that type of failure. Normal'pro- existing conditions is required. Examples of the cedure is to clean out to the greatest depth pos- data which must be analyzed are: 1 type of com- sible and then run a hydraulic pulling tool with pletion liner, COS, gun-perforated ; 2 size of spear in an attempt to pull the entire liner.
If casing and liner; 3 location and clearance of this fails, a cut is usually made just below the tight spots; 4 character and contents of forma- hanger and packer and this section pulled. A shortening as the formation compacts; and 2 cement plug is laid in the liner stub up to approx prevent or periodically relieve the friction imately 30 ft below the casing shoe.
The primary bond which transmits the compressive force to liner is then sidetracked and a new hole drilled. Completion procedure is the same as previously discussed. It is our conclusion that a combination of these In gun-perforated or pre-perforated comple- two approaches offers the optimum solution to tions wherein collapse has progressed beyond re- the problem. This device, as illustrated in will permit and then mill a l5-ft ft window Fig.
It has, however, only be applied when there is an adequate shale two fundamental weaknesses, which may be of con- break between the completion zone and water bearin sequence in some installations. These are 1 bearing sands above. In this case, a whipstock is it is pressure tight only to the extent of seal set in the casing stub and a sidetracked hole is reliability, and 2 it can be installed only at drilled and completed with a liner as previously the end of a joint which requires a relief of discussed.
The intermediate millout is utilized the frictional bond along the joint in order when water sands are located in the zone just that it may absorb movement prior to joint fail- above the oil sands or collapse. Normal ure. At this point, a stub liner is readily prevented or relieved and where pressure cemented in the hole and drilling is resumed with tightness is not essential, the casing adjuster oil.
A screen liner is then run inside the stub is the recommended installation. However, in liner. The development of this Whenever there is doubt as to condition of corrugated casing is now a research project with the casing above the collapse zone, or whenever a major casing manufacturer.
Progress to date i liner pulling or sidetrack operations are not very satisfactory and limited quantities for practical, the well is redrilled. The programmed method of installation the oil string, it is normal practice to cut and is illustrated in Fig.
A new hole is then drilled Prevention of friction bond between forma- with water or water-base mud to the sand top and tion and casing is limited to compaction zones casing is cemented. The producing section is not open to production. The procedure utilized drilled with oil and completed as previously des- in other areas and recommended for Creole in new cribed. Planned technique for placement is illus- ods of repairing wells with collapsed casing have trated in Figs.
The process is basic- been discussed. However, no mention has been made ally a two-stage cementation with the gel mater- of the prevention of future collapse in these ial batched behind the second stage. A brief consid- eration of the magnitude of the compressive force Stress relieving of a liner or pre-perforat applied in this compaction phenomenon indicates ed bottom section consists of nothing more than immediately that the solution to the problem lies perforation washing.
However, in a very few of the world's oil fields there exist active earth forces which are of such magnitude that ordinary methods of combating casing collapse are futile. These forces are created by actual movement of the rock or sediments penetrated by the well.
At least two basic types of earth movements in oil fields have been recognized: first, displacement along active fault planes; and second, subsidence of the complete sedimentary section above a zone of compaction. This latter type of movement is the primary cause of casing collapse in the Bolivar Coastal field, and to date has resulted in the repair or redrilling of over three hundred wells.
It is the objective of this paper to discuss the techniques which have been used to repair these wells and the protective measures being taken or proposed for future repairs and new completions. Sign In or Register. Advanced Search. Sign In. Skip Nav Destination Proceeding Navigation. Close mobile search navigation. All Days. Previous Paper Next Paper. Paper Contents.
Your water well contractor will also consider water chemistry and geology. If your well water pH is below 6. Similarly, if the well water has high levels of dissolved solids, it may be corrosive to steel pipes resulting from the galvanic current. When installing a casing, the contractor must avoid excess bending or vertical movements to prevent casing materials from cracking or deforming.
A damaged casing can do more harm than good. Over time, cracks can develop in a casing. Cracking can occur when the ground shifts during a natural calamity such as an earthquake or due to shock waves created by blasts at a nearby construction site.
Stones or other objects that press against the casing can also damage it. If your well casing has splits due to defective or welded seams, it will be unable to prevent groundwater and contaminants from getting in. If lightning strikes the well during a bad storm, the well casing can get damaged.
It can cause leaks to develop. To steer clear of issues, inspect your casing regularly and remember to check the part that sticks up above the ground for leaks and damage. This part is exposed to the elements and is particularly vulnerable to cracking.
A cracked well casing is a recipe for disaster. If the cover on top of your well casing gets damaged, insects and small animals could crawl inside. If they die and decompose, harmful bacteria may get into your water supply. Drinking contaminated water with elevated levels of bacteria is a leading cause of gastrointestinal problems. Many homeowners know the importance of maintaining their casings; however, they fail to notice the signs of a well casing leak.
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