3D printing sandstone porosity models

The petroleum industry requires new technologies to improve the economics of exploration and production. Digital rock physics is a methodology that seeks to revolutionize reservoir characterization, an essential step in reservoir assessment, using computational methods. A combination of X-ray computed microtomography, digital pore network modeling, and 3D printing technology represents a novel workflow for transferring digital rock models into tangible samples that can be manufactured in a variety of materials and tested with standard laboratory equipment. Accurate replication of pore networks depends on the resolution of tomographic images, rock sample size, statistical algorithms for digital modeling, and the resolution of 3D printing. We performed this integrated approach on a sample of Idaho Gray Sandstone with an estimated porosity of 29% and permeability of 2200 mD. Tomographic images were collected at resolutions of 30 and [Formula: see text] per voxel. This allowed the creation of digital porosity models segmented into grains and pores. Surfaces separating pores from grains were extracted from the digital rock volume and 3D printed in plastic as upscaled tangible models. Two model types, normal (with pores as voids) and inverse (with pores as solid), allowed visualization of the geometry of the grain matrix and topology of pores, while allowing characterization of pore connectivity. The current resolution of commodity 3D printers with a plastic filament ([Formula: see text] for pore space and [Formula: see text] for grain matrix) is too low to precisely reproduce the Idaho Gray Sandstone at its original scale. However, the workflow described here also applies to advanced high-resolution 3D printers, which have been becoming more affordable with time. In summary, with its scale flexibility and fast manufacturing time, 3D printing has the potential to become a powerful tool for reservoir characterization.

1. Summary of the Discoveries hitherto made in the Ossiferous Beds of the Basins of the Forth and Clyde

The author gave a summary of the discoveries which had taken place during the course of the session relative to the ossiferous beds of the basins of the Forth and Clyde. The additional information contained in his paper comprised, in the first place, an account of the older class of strata upon which the carboniferous group of rocks (in which saurian remains had been found) were supposed, in an unconformable position, to rest. Some of these were referred to a system of beds, which geologists consider as of a newer transition class, intermediate to grauwacke schist and coal strata. Thus, it was found that a peculiar hard and gray sandstone, containing mica, and occasionally alternated with siliceous schist,—which in Shetland succeeds to clay-slate; which, near Loch Ness, succeeds to a transition granite; and, on the north of the Tay, to grauwacke schist,—was thrown up on the south of the Forth, near North Berwick, in the form of immense severed beds or fragments, shewing that this transition-rock (an important one in the series of Scottish strata) is to be regarded as in some places fundamental to the coal measures of the district. This older grey sandstone is also alternated, either with aluminous strata of the same general character, or with a hard sandstone of a reddish colour.