Topic
Effective porosity
About: Effective porosity is a research topic. Over the lifetime, 1199 publications have been published within this topic receiving 26511 citations.
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TL;DR: In this article, the first cross-hole tracer experiment in the upper oceanic crust, using four subseafloor borehole observatories equipped with autonomous samplers to track the transport of a dissolved tracer (sulfur hexafluoride, SF6) injected into a ridge-flank hydrothermal system.
25 citations
TL;DR: In this article, the authors used the same statistical methods used on cumulative curves from sieve analysis of unconsolidated sands to characterize the porosity and displacement pressure of the Williston basin carbonate rocks.
Abstract: Stratigraphic entrapment of oil in carbonate is a function of petrophysics of the reservoir and trap rock. These petrophysical characteristics can be observed from sample examination without extensive laboratory measurements. Petrophysics is an essential addition to the physical measurements of total porosity and permeability routinely collected from reservoir rock samples. Total porosity is a ratio of the rock's void space to its bulk volume. Under subsurface reservoir conditions, this porosity is occupied by fluid of two phases. Commonly the non-wetting oil phase occupies this porosity according to the size and distribution of the rock's pore system. The displacement of interstitial water by oil depends on the size of pore throats. That part not effectively displaced by oil remains as irreducible water saturation within the reservoir. These reservoir properties can be determined from capillary pressure measurements conducted in the laboratory. The capillary pressure curves may be investigated by the same statistical methods used on cumulative curves from sieve analysis of unconsolidated sands. Seven distinctive petrophysical characteristics were evident from 200 samples of Williston basin carbonate rocks studied. These characteristics may be classified by effective porosity, displacement pressure, and pore distribution. Representative examples from this study show good and intermediate reservoir rock as well as reservoir-trap rock. The concept of low effective porosity can explain high water-cut production from carbonate reservoirs.
25 citations
TL;DR: In this article, a combination of optical petrography, SEM, BSE and fluid inclusion was used to reconstruct the diagenetic history of secondary porosity and mass transformation in deep burial sandstones.
25 citations
TL;DR: In this article, a new multiscale fractal transport model with an effective porosity model was proposed based on the fractal theory and the multilayer fractal Frenkel-Halsey-Hill (FHH) adsorption.
Abstract: In order to study gas transport properties of fractured shale gas reservoirs for the accurate estimation of shale gas production, a new multiscale fractal transport model with an effective porosity model was proposed based on the fractal theory and the multilayer fractal Frenkel–Halsey–Hill (FHH) adsorption. In shale matrix, both fractal microstructures of pores (such as pore size distribution, flow path tortuosity, and pore surface roughness) and multiscale flow mechanisms (including slip flow and Knudsen diffusion) were coupled. In fracture network, fractal fracture length distribution, stress compaction, and gas pressure were introduced to formulate a new fracture permeability model. These permeability and effective porosity models were then incorporated into the governing equations of gas flow and the deformation equation of reservoirs to form a numerical model. This numerical model was solved within COMSOL Multiphysics for shale gas recovery. Both transport models in shalematrix and fracture network were validated by experimental data or compared with other models. Finally, sensitivity analysiswas conducted to identify key parameters to gas recovery enhancement. Itwas found that themultilayer gas adsorption and fractal microstructures have great impacts on gas production in shale reservoirs. The cumulative gas production can be increased by 26% after 8000 days when themultilayer adsorbed gas is considered. Larger surface fractal dimension and larger tortuosity fractal dimension represent more roughness pore surface, higher flow resistance, and lower cumulative gas production. Bigger pore diameter fractal dimension means more pores, higher permeability, and higher cumulative gas production. Our model with fractal FHH adsorption was in better agreements with field data from Marcellus and Barnett shale reservoirs than other models.
25 citations
01 Jan 1995
TL;DR: In a H2S-related porosity, porosity can be produced entirely in the deep subsurface and does not have to represent a paleokarst surface or dissolution in the shallow-phreatic or vadose zones as mentioned in this paper.
Abstract: "H2S-related porosity" refers to porosity created in a H2S system where dissolution can be produced by the mixing of waters of different H2S content or by the oxidation of H2S. "Sulfuric acid oil-field karst" refers to a specific kind of H2S-related porosity where carbonate reservoirs of cavernous size have been dissolved by a sulfuric acid mechanism. In a H2S system, porosity can be produced entirely in the deep subsurface and does not have to represent a paleokarst surface or dissolution in the shallow-phreatic or vadose zones. H2S-related porosity is characterized by the large volume of hydrocarbons it can host, by extensive fracture permeability interconnected with "spongework" cavities or caves of tens to hundreds of meters in extent, by porosity related to structural and/or stratigraphic traps, and by the presence of high uranium and/or iron. Possible examples of H2S-generated porosity systems are the Lisburne field, Prudhoe Bay, Alaska, and some of the extremely productive fields of the Middle East.
25 citations