Pore Space Characteristics Research Articles

Resolving Pore-Space Characteristics by Rate-Controlled Porosimetry

SummaryBy monitoring the mercury capillary pressure in rate-controlled porosimetry (intrusion) experiments, new information regarding the pore space of a rock sample has been obtained. With this technique, called an apparatus for pore examination (APEX), it is now possible to resolve the pore space of a rock sample into two interconnected parts. One part identifies the individual pore systems (pore bodies), which are low-energy sumps or regions of low capillarity. The other part corresponds to the pore throats that interconnect with pore systems.New capillary-pressure curves have been obtained by partitioning the total capillary-pressure curve (normal capillary-pressure curve) into two subcurves: the subison capillary-pressure curve, which details the distribution of pore bodies, and the rison capillary-pressure curve, which details the distribution of pore throats. We present APEX data on Berea sandstone and San Andres dolomite that show the volume distribution of low-capillarity regions within the pore space of these rocks. These regions of low capillarity are the principal pore-space regions that trap the residual nonwetting phase upon imbibition of a strongly wetting fluid, as measured by toluene/air systems. The residual nonwetting-phase saturations as determined by the APEX method and by the toluene/air method are in excellent agreement. Thus, the detailed volume distribution of pore systems responsible for trapped nonwetting-phase saturation is determined from APEX measurements, which can have important implications for EOR.

PHYSICAL PROPERTIES OF SYNTHETIC SANDSTONE ROCKS1

ABSTRACTA novel process is used to coat glass spheres with a polymerizing thermo‐setting resin, only microns thick. Synthetic rocks of known grain size distribution and pore space characteristics are then made by heating the resin‐coated glass spheres under compression in a special mould. The dynamic Young's moduli of these rocks are found to be affected by the percentage of resin content (cement) and the synthetic diagenesis rather than the grain size and permeability.

Quantitative image analysis of finite porous media

SUMMARYReconstruction, from serial sections, of a branch‐node chart containing the connection pattern of the pore channels in small sandstone samples, and computation of genus are described.Seventy‐eight serial sections were obtained by serially grinding off layers of about 10 μm thickness from a 1 × 1 mm sample, whose pores had been filled with Wood's metal, and taking photomicrographs of the polished sections. Edge effects and rock enclosed by pore space were accounted for in the construction of the branch‐node chart. The importance of boundary effects was reflected by the difference between the minimum and maximum estimates of genus, Gmin and Gmax, respectively.The Berea sample (with porosity of 23% and average grain size of about 200 μm) was found to have essentially one main network containing over 87% of all pore space features, plus a number of very much smaller boundary networks representing ‘dents' on the sample sides. The number of anomalies from missed connections was found to be small and unlikely to cause significant error in the genus calculations. Both Gmin and Gmax for the sample were found to be essentially those of the one continuous main network.

THE MOISTURE RÉGIMES OF SOILS DEVELOPED ON KEUPER MARL

SummaryThe moisture régimes of several representative profiles of the Worcester series developed on Keuper Marl are described and interpreted using a simple field technique supplemented by determinations of pore space, moisture content, and moisture release characteristics. It is suggested that the textural B horizon of coarse blocky structure is the cause of waterlogging which occurs seasonally in the upper 61 cm of these soils. The C horizon, which has a fine blocky structure and a lower clay content, is more permeable, and determinations of pore space and moisture content showed an appreciable volume of air voids in it when the overlying horizons were fully saturated with water.After subsoiling to a depth of 76 cm at one site, the soil was waterlogged less often and then only for shorter periods than formerly.

Teodorovich's Method for Determining Permeability from Pore-Space Characteristics of Carbonate Rocks: GEOLOGICAL NOTES

Outlines the method developed by the Russian geologist G. I. Teodorovich for calculating permeabilities of carbonate reservoir rocks from thin-section analysis of pore-space configuration, and reviews results of its application, noting an average discrepancy of about 10 percent between calculated and measured permeability values.