The precise identification of mineralogic composition made possible by 

 the X-ray diffraction methods will permit the correlation of formations where 

 other data are lacking, or may prevent erroneous correlation based on unreliable 

 information. Identification of the kind and amount of minor constituents in 

 apparently homogeneous, thick formations may subdivide the sequence in such 

 a manner as to demonstrate the stratigraphic relationship to similar formations 

 occurring elsewhere. 



The analysis of reservoir rocks by X-ray diffraction may reveal details 

 of composition otherwise overlooked. In particular, the kind and amount of 

 interstitial clay may critically control effective porosity and permeability of 

 formations by changes in hydration and degree of flocculation as a consequence 

 of change in the solutions saturating the rock. Flocculation or deflocculation 

 and hydration or dehydration of clay minerals are controlled by their mineralogy 

 as well as by their environmental changes. Hence, the susceptibility of clay 

 minerals to change during the water-flooding or other secondary-recovery pro- 

 grams can be detected by X-ray diffraction analysis of reservoir rocks. 



The geologist and engineer will find that X-ray diffraction methods increase 

 the reliability of geologic logging. The method supplements petrographic tech- 

 niques of logging drill core, making possible quick and precise identification of 

 even exceedingly fine-grained types and complex mixtures. In addition, the 

 method can supply basic data on petrography and mineralogy necessary to 

 interpret more completely the electric and gamma radiation logs of drill holes. 

 Both engineers and geologists are finding that the X-ray method of analysis is 

 a powerful tool in the identification of potentially unsound materials in founda- 

 tion strata or construction materials proposed for use in dams, powerhouses, 

 buildings, and other large engineering works. 



Finally, X-ray diffraction analysis, both of geologic materials collected 

 from outcrops in the field and from cores of the synthetic materials in the 

 laboratory will yield detailed knowledge of processes involved in deposition, 

 consolidation, and induration of sediments. The methods of X-ray diffraction 

 analysis are unsurpassed in effectiveness and efficiency in the tracing of pro- 

 gressive changes in mineralogy and structure of materials. Application of these 

 methods will demonstrate the process of recrystallization during consolidation 

 and induration, such as may occur in unstable minerals like clays, and the 

 formation of new minerals, such as feldspar, mica, and zeolites. Only when 

 these and related processes are understood will the conditions of petroleum 

 formation, migration, accumulation, and production be understood fully. 



The versatility and adaptability of X-ray diffraction methods have justified 

 recognition by the petroleum geologist, engineer, and chemist. For one problem 

 the methods may afford merely a valued supplement to other techniques; for 

 another problem the methods may be indispensable to a successful solution. 



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