X-ray CMT images of abiotic carbonate precipitation in porous media from a supersaturated solution

Description

This file contains X-ray computed microtomography (CMT) images used to analyze abiotic carbonate precipitation in porous media from a supersaturated solution. An X-ray transparent and rigid-walled polycarbonate column was developed to hold the sand pack tight during the carbonate precipitation process. The column consisted of a polycarbonate tube with an inner diameter of 3.18 mm, an outer diameter of 9.53 mm, and a height of 44.1 mm. Two polycarbonate discs and two stainless steel springs were used to confine the sand pack in the polycarbonate column. Dry sand particles were hand-tamped on the polycarbonate disc attached to the spring in the column. Then, this compacted sand pack was topped with the second disc and spring, to hold it in position during the experiment. Calcium carbonate (carbonate) precipitation was achieved by using supersaturated solution of carbonate. The supersaturated carbonate solution was flowed to the sand pack to induce calcium carbonate precipitation using the sand grain surfaces as nucleation sites. The flow continued until the porosity was reduced to ~17%, at which point the peristaltic pump could not circulate the fluid at the given flow rate due to the flow resistance caused by lowered porosity and permeability. The sand pack was X-ray CMT imaged prior to precipitation procedure which is referred to as baselines scan (Scan 0). During the experiment, X-ray CMT imaging was conducted on the sand pack column when a significant reduction in permeability was observed. Total three precipitation scans (Scan 1,2, and 3) were obtained.