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Pore-throat sizes in sandstones, siltstones, and shales: Reply

November 2, 2011

In his discussion of my article (Nelson, 2009), W. K. Camp takes issue with the concept that buoyancy is not the dominant force in forming and maintaining the distribution of gas in tight-gas accumulations (Camp, 2011). I will restrict my response to the issues he raised regarding buoyant versus nonbuoyant drive and to a few comments regarding water saturation and production. I claim that the pressure generated in petroleum source rocks (Pg), instead of the buoyancy pressure (Pb), provides the energy to charge most tight sandstones with gas. The arguments are fourfold: (1) buoyant columns of sufficient height seldom exist in low-permeability sand-shale sequences, (2) tight-gas systems display a pressure profile that declines instead of increases upward, (3) gas is pervasive in overpressured systems, and (4) source rocks can generate pore pressures sufficiently high to charge tight sandstones.

Publication Year 2011
Title Pore-throat sizes in sandstones, siltstones, and shales: Reply
DOI 10.1306/12141010159
Authors Philip H. Nelson
Publication Type Article
Publication Subtype Journal Article
Series Title American Association of Petroleum Geologists Bulletin
Index ID 70003315
Record Source USGS Publications Warehouse
USGS Organization Central Energy Resources Science Center