residue work in Texas was developed without reference to that of McQueen. 

 In 1946 Ireland called a conference of active workers on insoluble residues. 

 This conference resulted in the publication of a standardized terminology and 

 a chart for description (Ireland, 1947), which is published herein in a modified 

 form (see Table 5-1) 



PREPARATION OF RESIDUES The materials treated for insoluble residues 



are well cuttings, cores, and outcrop samples. 

 Types of Samples The most desirable outcrop samples are chan- 



nel samples or a composite mixture of each 

 exposed stratum within a 5-foot or other close-spaced interval. Point-to-point 

 correlation is rarely possible, because there is very little probability of sampling 

 exactly the equivalent point some distance away. A 6-inch layer outcropping 

 within a 5-foot interval will not represent the whole interval, and it cannot be 

 correlated with the equivalent interval a mile away, which may have a 6-inch 

 layer exposed a foot above or below the one in the first outcrop. Only zones or 

 intervals may be correlated successfully. Outcrop samples of unweathered 

 chips, without lichen, soil, or other extraneous matter, are desirable. 



Oil- or water-well cuttings and cores are the most widely used materials 

 for residues. Cable-tool cuttings are the best samples, because they contain 

 a minimum amount of caved material and because each sample represents a com- 

 posite of the rock within the sampled interval. 



Rotary-tool cuttings are the most common well samples and are generally 

 the only type of samples available from deep wells. They are also the worst 

 samples. Caving is very common because long sections of the drill hole are not 

 cased. If shale beds or loosely aggregated materials lie above a given sample, 

 caving may reduce the amount of indigenous material of the sample to such 

 a small percentage that an insufficient amount of residue or none will be left after 

 solution. Such samples may require the use of forceps for picking out chips of 

 the indigenous material for solution. Drilling time, electric logs, and a thorough 

 knowledge of the section facilitates the identification of the indigenous material. 



Well cores must be split and a fragment taken from each inch or short in- 

 terval; and the whole must be mixed for the equivalent of a 5-foot sample, or 

 for a shorter interval if the lithology changes. Otherwise, inconclusive point-to- 

 point correlation would be necessary. 



The observable amount of indigenous material in a sample having 80 to 

 90 percent shale caving may be increased by placing two or more unit volumes 

 of the sample in acid, and, after solution, sieving out as many unit values less 

 one. Thus, if three units were used, two units would be sieved out after 

 solution. This will leave less than one unit volume, which will have a minimum 

 amount of caved material but several times more residue from the indigenous 



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