Discussion of Application of Oil Muds
- J.W. Bloemendal (Consultant)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling Engineering
- Publication Date
- October 1986
- Document Type
- Journal Paper
- 395 - 395
- 1986. Society of Petroleum Engineers
- 1.5 Drill Bits, 1.11 Drilling Fluids and Materials, 6.5.3 Waste Management, 1.6 Drilling Operations, 5.3.4 Integration of geomechanics in models
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I would like to comment on three oil-mud papers: "Behavior of Oil Muds During Drilling Operations," "Low-Toxicity Oil Muds: A Knowledge of Downhole Rheological Behavior Assists Successful Field Application," and "Magnesium Oil Mud Provides Gauge Hole in Bischofite/Carnallite Formations" (April 1986 SPEDE, Pages 97-106, 107-14, and 115-21, respectively).
I fully agree that an oil mud is superior in drilling unstable, deviated, or water-sensitive formations. I have serious doubts, however, about the practical and economical application because of the disadvantages mentioned by most authors but not discussed enough to convince me to give up my opposition to oil-based muds (OBM's).
I question the higher rate of penetration claimed for relaxed API-WL OBM's compared with water-based fluids, because the improved performance of OBM's might be largely or entirely a result of the beneficial effects of polycrystalline-diamond-compact bits, higher API-FL, lower effective bottomhole density, better lubricity (which results in higher weight on bit), higher revolutions per minute, more favorable rheological properties, and probably many more effects that cannot be recognized easily in practice. Maybe we still have our equipment for laboratory drill tests rigged up to investigate the isolated effect of OBM's while the other factors are changed one at a time.
The maintenance of an OBM generally is easier than for a complicated polymer system but, as indicated by some authors, it requires very experienced engineers to prevent the mud from flipping in certain circumstances. prevent the mud from flipping in certain circumstances. Working with complicated muds in many cases just means asking for trouble.
OBM's have been reported to cost about twice as much as an expensive water-based mud (WBM), but I know that the expenses to wash the cuttings and to return enormous volumes to shore for burning are not charged to the mud bill where they belong. This makes the mud twice again as costly. In areas where lost circulation is a problem, we lose that more expensive mud!
We also have environmental problems. Oil disposal in the sea is not permitted worldwide. Disposal of mud that contains more than 1 percent mineral oil is not allowed, so obviously the disposal of cuttings wash water, washed cuttings, etc., is not allowed when an OBM is in use. Washing the cuttings removes only 10 to 20 percent of the OBM and the oily wash water travels the same route as the oily "washed" cuttings-down the caisson! When environmentalists realize this, OBM's may no longer be allowed to be used. Incinerators or flares take too much space on platforms and might pollute the air. The application of platforms and might pollute the air. The application of so-called low-toxicity oil muds solves nothing; these are still mineral oils and will be detected by the approved testing equipment. While the low-toxicity muds are slightly less toxic than base oils that contain aromatics, this reduction in toxicity is cancelled by the organic agents added to the mud to make it a drilling fluid.
In my opinion, all the above arguments are handled too lightly when application of an OBM instead of a WBM is decided.
Related papers:SPE 13001, SPE 11356, SPE 13158
Related discussions and replies:SPE 15965, SPE 16445, SPE 16456, SPE 17012
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