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A study of these records and an interview with the field superintendent of this company, Mr. F. J. Prehoda, brought out the fact that cement previously placed in the bottom of the well, was carried back into the formation. This probably accounted for the failure of the various cementing joks to shut off the water. This department recommended that the company pump mud-laden fluid into the sands near the bottom of the well. Mr. Prehoda, who has had considerable experience in the use of mud-laden fluid, readily agreed to try the experiment, and co-operated with the State Mining Bureau in the matter of eliminating the water trouble which was spreading to adjoining wells on this and neighboring properties.

Previous to the beginning of mudding operations, Mr. Prehoda reported that the well had been bridged from bottom (1285') up to 1100', with brick and rocks driven down by the tools. On May 10, 1917, the bridge was drilled out to a depth of 1185' and mudding operations started. The oil string was set at a depth of about 1100', and mud about the consistency of rotary mud pumped into the well through threeinch tubing which extended to a depth of 1168'. About 24 hours after mudding operations were started in this well, Salt Lake Oil Co. Wells Nos. 329, 330, 347 and 318 and Rancho La Brea Oil C'o. Well No. 38, pumped water (arrying considerable mud. I'pon request from this department the wells of the Salt Lake Oil Co. producing this mud were shut down.

After mudding operations had been in progress for over a month without any apparent success to mud up the formations, this department suggested that sawdust be used in addition to the mud in order to stop up the pores, or openings, in the formation penetrated by the mud. A favorable effect was immediately noticed in that, shortly afterwariis, June 21, circulation was obtained. Following this, the well was thoroughly mudded by forcing mud-laden fluid into the formatio under a pump pressure of 100 pounds per square inch. The well was shut down, leaving the mud-laden fluid standing at the surface.

Mr. Prehoda reported to this department that a total of about 700 cubie yards of adobe and 40 cubic yards of sawdust were pumped into the well during the first mudding operation.

On August 1, 1917, the mud was washed out of the well and the well bridged from 1109 to 1095' by tamping rock into the formation and the bottom of the well cemented with 50 sacks of cement pumped through tubing, bringing the top of the cement plug up to a depth of 1080'.

After cementing, the well was allowed to stand about three weeks and put on the pump and produced between three and four hundred barrels of clear, salty water per day. No mud used during mudding operations appeared in the well.

About a month after the cementing of Well No. 41, water again broke into Rancho La Brea Well No. 38. Subsequent to water breaking into this well, Rancho La Brea Well No. 41 was mudded a second time. This latter operation was started on November 13, and was finished on December 4. During this second mudding operation, four feet of the cement plug in the bottom of the well were drilled out, five old bullropes cut into three-inch lengths mixed with adobe, about 70 yards of adobe and 10 yards of sawdust were pumped into the well under a pressure of about 100 pounds per square inch. During this mudding operation, Rancho La Brea Well No. 38 was shut down. On December 11, when the pumps at Rancho La Brea Well No. 41 were practically “stalled” and the well taking only a small amount of mud, Well No. 38 was put on the pump and began to pump muddy water. Well No. 11 immediately began to take more mud. For three days Well No. 38 pumped muddy water and then started to pump a small amount of oil. According to the production report, this well produced 300 barrels of oil and 200 barrels of water during the month of December, 1917, while the mud-fluid stood at the surface in Well No. 41.

The information relative to work done at the first and second mudding operations at this well were furnished this department by Mr. F. J. Prehoda.

Accompanying this report is a statement showing the monthly production of oil and water of Salt Lake Oil Company's Wells Nos. 329, 330, 347 and 348, and Rancho La Brea Oil Company Well No. 38. These wells were directly affected, and produced mud during the initial mudding operation of Rancho La Brea Well No. 41. This table shows that these wells averaged a total of about 500 barrels of oil and 4445 barrels of water during the months of January, February, March, April and May, 1917. This was before Rnacho La Brea Oil Co. Well No. 41 had been mudded up. The table shows that these wells were shut down during June and July. From August to January inclusive, these wells averaged 2259 barrels of oil and 4230 barrels of water per month, showing a net average increase of oil to 1759 barrels per month. This increase of oil is probably due to work done in mudding Rancho La Brea Well No. 41.

It is interesting to note at this time that the well is standing full of mud-laden fluid up to a depth of 140 feet from the surface, and from this depth up to surface, the well stands full of clear water. Previous to mudding operations, fluid stood at a depth of 173 feet and could not be lowered by bailing. The fact that mud-laden fluid and water stands at the level indicated, tends to prove that water is not penetrating the oil-bearing formations at this well. This is rather interesting in view of the fact that this well has been standing undisturbed for a period of about four months.

One factor of great importance in the study of water conditions in the area under discussion, is the presence of large quantities of water in certain wells in the Salt Lake field previous to penetration of “bottom water" in Rancho La Brea Well No. 41. Available figures indicate that Rancho La Brea Well No. 41 was not the cause of the principal water trouble in the adjoining wells. The mudding of this well, however, has bettered the water condition of the adjoining wells, and has resulted in a marked increase in the production of oil.

The main source of the present water trouble affecting wells of the Salt Lake Oil ('ompany mentioned in this report, antedates the deepening of Rancho La Brea Well No. 41, and may possibly come from one of the abandoned wells which may have been improperly plugged.

It is the opinion of the Deputy Supervisor that while water sands in Rancho La Brea Well No. 41 may be mudded up, that the oil sands in this well have also been thoroughly mudded. This department has recommended that the Rancho La Brea Oil Company leave Well No. 41 shut down for a certain period of time. It has also been recommended that the Rancho La Brea Oil Company and the Salt Lake Oil Company gauge the production of certain of their wells located in the vicinity of Rancho La Brea Well No. 41, and furnish this department with the results of these gauges, in order that further study of the water situation in this area may be made.



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MR. PREHODA: In regard to Well No. 41 it was water we were after, being under the impression it was good boiler water. We intended to (arry 63 casing to the first shale below the oil sand and land it; but as the oil sand was running in we were umable to tell when the shale had been reached until water had made its appearance. The water was not noticeable until we reached 1190 then it raised within 170 ft. of the surface. The well was drilled to 1248 ft. then the water tested as to its value for boiler purposes. Finding the water of no value we proceeded to plug the well and shut the water off. I had the well plugged to 1180' and cemented. After letting it stand three weeks, had it opened to test and found there was no cement; it must have washed away. Then it was plugged up to 1120' and again cemented it stood for three weeks more, and tested only to find the same results. The well was cleaned out and the 63 casing was allowed to follow, after which we found that shale had been gone through from 1085' to 1118'. The well was bridged to 1090' and was cemented. After standing a period of three weeks was tested and found the cement set but the water was not shut off. The well was pumping one month and produced only warm salty water. After consulting Mr. Kirwan we agreed to mud the well in hopes of mudding the passages which we thought were leading from this well to our No. 38 a distance of 500' away; also the Salt Lake wells which are from 1500' to 2000' distant. I had used the mud two days when Mr. Foster informed that his wells on the Salt Lake were pumping mud. After imparting this information to Mr. Kirwan he took the matter up with Mr. Wooten and wells were shut down and mudding started again. About 600 yards of adobe were pumped in, but could not get any circulation. Mr. Kirwan suggested that I get some sawdust and mix it in the mud, which I did, and after using some 25 yards, finally got a circulation ten to fifteen minutes at a time and the fluid would disappear. It continued this way for a week or ten days. Each day the circulation remained longer until the fluid did not leave. I kept circulating for one week and then let the well stand for about one month. Then I consulted Mr. Kirwan and we decided to pump the wells; the Salt Lake was notified and I started No. 38 on our property and it went to making oil the first day and the Salt Lake wells also showed more oil than they had for monthis before. After four weeks our Well No. 38 went to pumping mud again. I at once went to Well No. 41 and found that the fluid had gone down to the water level of 170'. Put a crew on mudding it again. This time I used bull rope chopped up fine and 8 yards of sawdust and 60 yards of adobe. Had no trouble in getting circulation and I had 400 pounds pressure put on the well after the pumping was started. I had No. 38 started to see if it would have any effect on the pressure and I found that it did. So I had the crew pump in mud for two more days when the pump was stalled again. Then let the well stand four weeks more, when starting it again it pumped muddy water for two days when oil began to appear and in one week was pumping 30 per cent oil and has been improving daily and at this writing is doing 50 per cent oil.

My first experience with mud was November, 1912. I had Mr. Perkins cement Well No. 51 for me. When I went to test the well, found the water was not shut off. We drilled about 20' further and then cemented the 81". The cement set that time all right, but the water was still there. We couldn't get circulation. I had a hydraulic pump there2200 pounds pressure on it. I stated that we couldn't get circulation. I then got this mud and a tapering shoe. I drilled the hole ahead, got the mud all ready and I circulated the mud awhile and drove my shoe down into this small hole- I did not wait for it to set--but I bailed it out and let it stand for seven days and the well was just as dead at the end of seven days as it was the first day. From that time I went to using mud.

MR. KIRWIN: What was the depth of that well, Jr. Prehoda?
MR. PREHODA : On the drilling well? I think it was 1200'.

MR. KIRWIN: Do you think that was a combination of formation shut-off or due to the mud only?

MR. PREHODA: I think it was a good deal the mud.

MR. STONER: From the description of Well No. 41, all the mud you pumped went into the oil sands.

MR. PREHODA: I had my 65" down below the oil sands.

MR. STONER: It is a question in different areas whether or not the oil would stand that much mud and come back. MR. PRELODA: I don't know. I never pumped 11. . :

Forty-one stands today. Q. The mud you used was all black adobe mud?

Yes. All black adobe mud. Every day when we pumped this mud in the well we would first shovel all the sand that accumulated in the bottom of this sump hole out.

Q. How do you figure the oil got into the pay sand? Did the sawdust stay out of your well into the bottom water sand ?

Yes sir, and followed that channel. I have wells much closer than the Salt Lake that were never affected at all. In fact, I have one well that's in front of one of the Salt Lake wells and it is not affected, vet one of their wells was affected. It shows that there must be an underground channel connecting those wells together.

MR. STONER: In mudding up wells like that, the mud would follow the line of least resistance.

MR. PREHODA: The reason I don't think there is much mud in my own sand is this: I think after you mud a certain length of time, the mud

: accumulates below the shoe and would keep it out of the oil sand. I think it coats over just the same as in a rotary hole.

Q. This rotary mud that you used: was that light? 1. No, it is heavy'.

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