美国得克萨斯古生界和中生界鲕粒的微孔隙度

本文所述的由1-5μm自形菱形方解石组成的微晶化鲕粒采自得克萨斯奥陶系-侏罗系的鲕粒灰岩和泥粒灰岩,其中:露头样品4个,岩心样品3个,岩屑样品7个。微晶化鲕粒的孔隙度可大于15%,渗透率为1毫达西.鲕粒的微晶化不是由淋滤作用所引起,而是在矿物稳定化过程中由文石转化而成方解石。

Microporosity in Ooids: Mesozoic and Palaeozoic of Texas,USA

Porosity within micritized ooids may exceed 15 percent with permeabilities up to about 1 millidarcy. The most porous and permeable micritized ooids all exhibit a characteristic texture: they consist of euhedral calcite rhombs 1 to 5 microns in longest dimension. Massive Cotton Valley gas wells interpreted to produce from this type of microporosity may initially yield as much as 300,000 cubic feet of gas per day or more. Intraooid porosity may constitute a significant reservoir for gas, but not for oil. Micritized ooids from 14 samples ranging in age from Ordovician .to Jurassic exhibit a common fabric and may have been altered by a common process. Micritization of these ooids may have occurred during mineralogical stabilization from aragonite to calcite. The micritized texture of the ooids described in this paper is not a product of leaching, for this type of micritized ooid is common in strata unaffected by leaching. Micritization of ooids may be of great significance to the development of gas fields in grainy rocks which have not been dolomitized or leached. Micritized ooids may also be important in many oil reservoirs with binodal pore sizes.