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concerns." oil operations require that the industry be in the hands of large Particular attention is called to the current statement that "efficient

shut-offs among small operators is slightly better than nine out of ten. out of every four, while, on the other hand, the average of successful producer in the state shuts off water successfully at less than three wells centage of successful work ranges from 93 down to 71. The largest

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TABLE 1.

Comparison of Results Obtained by Certain Companies in Excluding Water From Oil Wells in California.

July 1, 1917-June 30, 1918.

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Associated

Doheny

General Petroleum

Southern Pacific

Standard

Shut-off Shut-off Per cent Shut-off Shut-off Per cent Shut-off Shut-off Per cent

success

failure

of

success failure

of

success failure

success

success

of success

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Comparison of Results Obtained by Certain Companies in Excluding Water From Oil Wells in California-Continued.

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*Does not include 25 recementing jobs, 22 of which were failures.

Both jobs successful at test, but failed shortly afterwards.

Immediately upon the organization of the department, we were requested to make definite rules regulating the use of rotary tools. Stringent rules were not adopted because it appeared no definite evidence had been collected by the supporters of either the rotary or cable tools. It was also apparent that many claimants were unduly prejudiced in favor of one method or the other. The figures now available show that failures to shut off water occur very much oftener with rotary tools than with cable tools.

The extraordinary difficulty in properly drilling and protecting the Sunset field was pointed out in formal order No. 5, relative to Union Oil Company well No. 7, International. This order was held by some. individuals to be too stringent. Attention is now called to the fact that only one-half of the attempts made in the Sunset field to shut off water in rotary holes are successful.

In the case where the department took legal action, charging falsification of drilling records, the future of the very productive Montebello field was at stake. The figures at hand now show that more than a third of the attempts to shut off water are, failures. Therefore the department has no apologies to offer for exhausting all legal methods in attempting to protect this field.

Both the advantages of careful engineering work and the disadvantage of rotary tools are clearly set forth by the figures showing the percentage. of failures in the Coalinga field. It will be noted that the difference between the success and failure of a shut-off frequently depends upon determining, within five feet, the depth at which a shut-off should be attempted. This can not be determined without geological and engineering work, and requires a log more accurate than can be obtained when rotary tools are used.

The department has frequently been called upon to make definite blanket rulings requiring the use of cement at all wells. We have avoided taking such a position on account of the lack of definite facts. It is, therefore, of special interest to note that a comparison of results shows that cement is not always necessary. In other words, the mere use of cement is not automatically a cure or preventative for all water troubles.

Some operators have argued that the use of large quantities of cement would protect all oil formations left back of a string of casing. This argument has been advanced particularly by some of the concerns having poor records for simple shut-off at the shoe of casing. Therefore, the burden of proof remains upon them.

There are several cementing concerns who do work by contract. Their varying percentage of success is shown by the figures.

There are numerous mechanical details which must be given careful attention if successful shut-offs are to be obtained. Sometimes operators

have indicated that the department is too strict. Such opinions are usually held by persons who have not had wide experience in observing such work, and the details set forth by Mr. Collom will show the careful reader that there is a basis of fact for our requirements.

STATISTICS OF OIL PRODUCTION.

Monthly statistics for various fields and for the entire state are given here for the purpose of bringing records, previously published in Bulletins Nos. 69, 73 and 82, down to date. The figures as in previous publications, are those collected by the Standard Oil Company. They closely check those collected by the Independent Oil Producers' Agency and also the figures collected by this department in the form of sworn statements.

The Lost Hills and Belridge fields show the greatest decline in average daily production per well. All fields, except Lompoc and Santa Maria and Whittier-Fullerton, show a decline in production. It has already been noted that the increases for the Lompoc and Santa Maria field and the Whittier-Fullerton field are due, respectively, to the Casmalia and Montebello fields.

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