Miscellaneous Subsurface Methods 685 



well. Figure 370 illustrates a typical water-locating survey, comprising 

 two traverses of the formation after the check run to determine condition- 

 ing of the fluid in the well. Two points of water entry are indicated. A 

 subsequent plug-back to 3,626 feet reduced the water seven percent, the 

 amount entering the well at 3,613 feet. 



A clean well, free of cavings and other material that might interfere 

 with the operation of the water-locator equipment, is an important pre- 

 requisite to a successful survey. If the well has been killed with water, 

 or water has set on the formation over an extended time, the well should 

 be produced and then allowed to come to a static level before the survey. 



The fluid electrolyte is distributed throughout the water in the well 

 by means of a special bailer. In a flowing well it is necessary to lubri- 

 cate the survey to be run immediately after the electrolyte has been 

 dumped. 



After a test run to verify proper conditioning of the well fluid, the 

 well is produced, either by flowing, swabbing, or bailing, to allow forma- 

 tional fluids to enter the well. A traverse then is made with the electrode 

 to determine where dilution of the electrolyte is occurring. The number 

 of traverses that may be necessary usually depends upon the rate at 

 which the well produces water. 



THE POROSITY AND PERMEABILITY OF CLASTIC . 

 SEDIMENTS AND ROCKS 



GEORGE H. FANCHER 



The occurrence of petroleum depends fundamentally upon the ability 

 of fluids to move through strata of the earth's crust. From a physical 

 point of view, all problems relating to the origin and accumulation of 

 oil, natural gas, and water in, and their production from, the depths of 

 the earth's crust involve the flow of fluids through porous media. The 

 porous media of consequence are sedimentary in origin in the main and 

 include such clastic sediments as silts and soils; unconsolidated sands 

 and consolidated rocks, such as sandstone and limestone, both oolitic and 

 massive; and other porous rocks of lesser economic significance in the 

 oil industry. 



Some Characteristics of Sediments 



The characteristics of the solid constituents of sediments important 

 to evaluation of those physical properties which determine the behavior 

 of fluids in the sediments may be expressed in terms of at least six meas- 

 ureable parameters. These are 



(1) size 



(2) shape (sphericity) 



Note: The illustrations in this section were prepared by Williara E. Fickert, Department of Petro- 

 leum Engineering, University of Texas. 



