TABLE 12-1 



'Comparison of Effective to Total Porosity 

 (By laboratory measurement) 



depends on the type of rock to be tested, the number of analyses to be made, 

 and the degree of accuracy required. 



Determination of Bulk Volume 



It is preferable to use the same specimen for both porosity and permeability 

 measurements. The sample is prepared by drilling a cylindrical plug approxi- 

 mately lxl inches parallel to the bedding plane of the core, or by sawing a 

 cube of the same dimensions. The cube has one advantage over the plug in that 

 the vertical permeability can be determined on the same specimen by simply 

 rotating the cube in the holder. The sample, whether cylinder or cube, is cleaned 

 of oil by extraction with suitable solvents in a Soxhlet or any of the pressure 

 and centrifugal types developed by the various core laboratories for the rapid 

 extraction of oil. Toluene, benzene, benzene-alcohol mixtures, pentane, and 

 other solvents are suitable; chloroform and carbon tetrachloride are not recom- 

 mended because of the possibility of hydrolysis resulting in the production of 

 acids. The sample is then dried under infra-red lamps or in an electric oven, 

 and cooled in a moisture-free atomsphere. 



(1) Bulk-Volume Determination By Submergence of a Saturated Sample 



The extracted and dried samples are placed in a wide-mouthed jar closed 

 with a rubber stopper fitted with a two-way stopcock. One side of the stopcock 

 is connected to a vacuum pump and the other to a funnel containing the saturant. 

 The jar and samples are evacuated and the stopcock turned to admit the saturant 



232 



