--> Abstract: Understanding the Relationship Between Porosity and Permeability Using High-Pressure Mercury Injection Capillary Pressure Data Gives Insight Into Hydrocarbon Recovery, by John S. Sneider and George Bolger; #90078 (2008)

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Understanding the Relationship Between Porosity and Permeability Using High-Pressure Mercury Injection Capillary Pressure Data Gives Insight Into Hydrocarbon Recovery

John S. Sneider1 and George Bolger2
1Sneider Exploration, Inc., Kemah, TX
2PetroTech Associates, Houston, TX

A study using over 400 samples with porosity, permeability and mercury injection capillary pressure (MICP) data identified several key parameters calculated from MICP data that characterize reservoir quality and quantify the likelihood of hydrocarbon recovery. The sum of pore- throat diameter x the porosity accessed by a pore-throat of a given diameter (SumDB)accurately predicts permeability using the equation kair = 10(C1*LOG(SumDB) - C2) over a range of permeability from <0.001 md to over 1000 md , where C1 = 1.6337 and C2 = 2.2081. The "Pseudo Pore Throat Aperture" (PPTA) is equal to SumDB/(Total Porosity), and is the effective hydraulic radius of the rock. The PPTA can be used to divide the reservoir into flow units. A cross plot of porosity versus permeability contoured by PPTA indicates that the size of the connecting pore-throats controls the effectiveness of porosity toward permeability. At higher porosity values, pore-throat size is the dominant control on permeability. Porosity has a greater impact on permeability as the hydraulic radius and the porosity of the rock decrease. Although the research is preliminary, the ability of hydrocarbons to be produced seems to be linked to a combination of pore-throat size and fluid properties. When comparing rocks with the same air permeability but different porosities, rocks with lower porosity are better reservoirs because the pore-throats are larger, and therefore will have higher relative permeability to hydrocarbons. The more viscous the fluid, the larger the pore-throats must be to recover the hydrocarbons.

Using this logic, effective porosity values are determined by fluid type using different pore-throat size cut-offs. Pay in a field can be ranked based on pore-throat size cutoffs and fluid properties.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas