as i have tested the wear rate of the WC drill bit, depends on grain size of the rock sample used during drilling operation (weight loss method).
For medium-grained sandstone the wear rate of the drill bit is 6.66 mm/sec (Temperature induced is around 91 degree centigrade)
whereas in case of fine-grained sandstone the wear rate of the drill bit is 10 mg/sec.(Temperature induced is around 128 degree centigrade).
what is the difference between and reason behind these two rock samples.
You probably need to look at the basic rock properties of the 2 sandstones. Is the porosity the same? How well cemented are the grains? Are the properties uniform - e.g. permeability can be different in orthogonal directions? etc...
Vijay the grain size is not the issue but the strength of the rock which depends on many other factors other than the grain size such as cementation (some sandstones are cemented with carbonate cement or even gypsum) which makes the rock very weak others are cemented with quartz which make them really hard. other factors are the porosity and permeability (porous and permeable rocks are softer than their compact counterparts), bioturbation, fracturing, age (Younger rocks are softer due to less compaction) and many other factors. so i suggest you talk about the wear of the WC drill bit versus rock strength rather than their grain size. regards
Fadhil
Agreed with the views of Fadhi Saooni Sir. I think besides petrophysics, Rock mechanics studies (compressive strength etc) will be helpful in finding the answer. Regards.
thank you very much for you kind reply, thanks a lot sir.
Fadhil Sadooni sir please send me your mail ID for communication regarding my work sir. please help me out sir
Vijay, good question. If you do not consider other parameters then the grain size is one factor that influences the rock strength, permeability and porosity aspects. The finer the grain size harder and less porous is the rock. Therefore, fine grained rocks normally ihave greater wearing effect on rocks and vice versa. However, rock abrasivity is one important factor that can overcome the grain size effect. This means even if the rock is medium grain size but more abrasive then it will have a greater wearing influence on bit in comparison to fine grained non-abrasive rock.- Prof. Rai
Is not the effective bailing out of drill cuttings also a factor in drill bit wear and tear / abrasion / life? lf drill cuttings get bailed out efficiently, then probably drill wear and tear gets reduced, as it will be churning the drill cuttings inside the drill hole.
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