OKLAHOMA ACADEMY OF SCIENCE 107 



XX. "DRILLITE" AND ITS SIGNIFICANCE TO THE 



GEOLOGIST 



A. C. Shead 



From the Oklahoma Geological Survey. 



The term "drillite" has been appHed to an artificial ineta- 

 inorphic rock produced by the rotary core drill, particularly where 

 fluid circulation has been cut off from the bit in contact with the 

 rock, thus preventing the lieat generated by friction from escaping 

 rapidly from its point of origin. 



The main outstanding feature of this material, in some in- 

 stances, is its close superficial resemblance to basaltic igneous rock 

 and the consequent mistake of the geologist in thinking that the 

 drill has encountered a crystalline rock and the likelihood of the 

 ribondoninent of the h.ole for this reason. This danger has been 

 emphasized by Pratt'-'' and by Wratherf and its reality can be at- 

 tested .by the writer who was misled into making the following 

 analysis of such a "drillite" or "fused core." 



Analysis of "Drillite" from depth of 2985 feet in the Daymen 

 well near Grandfield, Oklahoma, in SW.^4sec. 35, T.3S., R.16W. 



SiO„ 49.60 Percent 



Al.,6„ 15.86 Percent 



Fe.'Ol" 0.72 Percent 



Feb " 17.84 Percent 



MgO 1.92 Percent 



CaO 7.03 Percent 



Xa.,0 0.92 Percent 



K.,6 •- 2.12 Percent 



H,0 0.42 Percent 



H^'O plus L 1.98 Percent 



Tib., 0.65 Percent 



P.,0"- - 0.213 Percent 



.S "_-- 0.25 Percent 



Cr.,0, Very faint Trace 



\\^)'o 0.09 Percent 



Total 99.613 Percent 



Even the chemical composition is that of a rather unusual bui 

 not impossible basalt where ferrous iron largely replaces magnesia. 

 Hov/cver, this high ferrous iron is very remarkable and lead 



*Pratt Wallace E. A note on supposed evidence of the volcaric orgin 

 nf Gulf Coast domes": Bulletin American Association of Petroleum Geologists, 

 Vol. 5, No. I. p. 91 Jan. ar d Feb. 1921. 



tWrather, W. E. Supposed igneous rock from Wichita County, Texas 

 wells: Bulletin, Amencai. A-'ssociation of Petroleum Geologists, Vol. S, No. 4. 

 _]). 512, July and Aug. 1921. 



