Chapter 33 

 CARBONATE POROSITY AND PERMEABILITY 



W. C. Imbt 



Division Exploration Superintendent 



Stanolind Oil and Gas Company 



Houston, Texas 



STATEMENT OF PROBLEM 



The petroleum industry's main interest in carbonate rocks is in the 

 formation of porosity and permeability. Many dolomites and lime- 

 stones contain liquid hydrocarbons; however, the porosity or perme- 

 ability factors are frequently so low that it is not economically pos- 

 sible to produce the contained fluids or gases. The industry has devel- 

 oped techniques of increasing porosity and permeability; however, 

 only a relatively small amount of fundamental research has been 

 undertaken in the mechanics and development of naturally occurring 

 porosity and permeability. The need for systematic research in car- 

 bonate porosity becomes more urgent when it is realized that over 

 half of the world's presently known petroleum reserves are contained 

 in carbonate rocks. 



For many years the industry has carried on experimentation with 

 and practiced secondary recoA^ery of liquid hydrocarbons from sand- 

 stone reservoirs. Employing the motivating force of injected or intro- 

 duced water, or injection of air or gas into key wells, has resulted 

 in phenomenal recoveries of oil above that produced by natural means 

 with normal reservoir behavior. Repressuring of the oil sands in 

 western Pennsylvania, eastern Illinois, eastern Kansas, and Oklahoma 

 has resulted in the recovery of millions of barrels of oil which would 

 have otherwise been lost to our national petroleum economy. In some 

 of the eastern Kansas secondary recovery projects, more oil will 

 be recovered during the secondary phase of production than was ob- 

 tained by normal producing practice. 



Unfortunately, only a small amount of secondary recovery has been 

 attempted in carbonate reservoirs, and this with varying degrees of 



616 



