. Bulletin. mud-laden fluid iu oil and gaswells : Bull. 134, Bureau of Mines, 1916, 86 pp. 80 UKDEEGROUXD CONDITIOKS IK OIL FIELDS. or by landing the pipe on a good seat of tough shale, sticky clay, hardshell, or limestone for a formation shut-off. Where the top watershave a considerable hydrostatic head the cementing method shouldbe used. Before the pipe is landed several feet of small hole shouldbe drilled ahead in order to insure a tight fit for the casing shoe. Samples of water from drilling wells should be collected foranalyses. In a finished well the top waters may have access to the und
. Bulletin. mud-laden fluid iu oil and gaswells : Bull. 134, Bureau of Mines, 1916, 86 pp. 80 UKDEEGROUXD CONDITIOKS IK OIL FIELDS. or by landing the pipe on a good seat of tough shale, sticky clay, hardshell, or limestone for a formation shut-off. Where the top watershave a considerable hydrostatic head the cementing method shouldbe used. Before the pipe is landed several feet of small hole shouldbe drilled ahead in order to insure a tight fit for the casing shoe. Samples of water from drilling wells should be collected foranalyses. In a finished well the top waters may have access to the under-lying oil sand through a defective water shut-off, but water mayalso enter a properly drilled well from a neighboring well where theupper waters have access to the oil sand and are working through toother wells. Bottom or other water may likewise come from aneighboring well. In the Avell itself top water may have access to the hole by: (1)The shut-off being too high; (2) the water leaking around the shoe. E-Bottom FiGDEB 17.—Hypothetical sketch to show different water sands. Wells 1,Mere drilled to the same depth, but only la got oil. ,-^Water often oc-D curs higher onthe steep sideof the fold. la, and lb of the water string; (3) poor coupling connections due to crossthreading or the pipe not being sufficiently screwed together; (4)collapsed casing; (5) a split in the casing, the pipe worn throughby the drilling line, or corrosion of the casing by strong corrosivewaters in the sands. An interesting example of a water string being cemented too highis shown in figure 18. It was not understood why this well did notmake Avater, as the correlation indicated that the shut-off was toohigh. During a period of reclaiming pipe the oil string was cut at1,851 feet and pulled, as shown by the center sketch of figure this, the well showed an appreciable amount of water, andfor some time the source of this water was not known. An analysisof the water and a study of adjacent
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectminesandmineralresou
