SPM Applications in Geochemistry and Minerals Technology

Dr. C. Hall, Schlumberger Cambridge Research Limited, High Cross, Madingley Road, Cambridge, CB3 OEL, U.K.

Dr. G. Graham, Department of Petroleum Engineering, Heriot-Watt University, Riccarton, Edinburgh EH14 4AK, U.K.

AFM is already established as a unique tool for scientists who study mineral surfaces in contact with water and aqueous solutions. The ability to image while varying solution concentration, flow rate, temperature and electrolyte potential enables corrosion, electrode position, and mineral growth and etching processes to be monitored in real time.

An important application is the study of mineral growth and etching processes in the field of geochemistry (1). A TopoMetrix Discoverer™ has been used to monitor in-situ growth of barium sulfate in supersaturated solution. Barium sulfate is an inorganic scale deposited in hydrocarbon reservoirs.

[Barium sulfate] [Barium sulfate] Click image for a closer look, click ICON for a high resolution (JPG) file 185k.

Figure 1 , (010) Barium sulfate surface imaged following flow of supersaturated barium sulfate solution.

A single crystal of barium sulfate was cleaved producing monatomically flat surfaces separated by crystallographically aligned steps. The crystal was mounted in the Discoverer™ AFM fluid cell and exposed to degassed supersaturated barium sulfate solution. Solution concentration was maintained constant using gravity feel to ensure a laminar flow over the tip and substrate.

Rapid growth of spiral shaped crystals is observed. Figure 1 shows growth containing both single and double headed spirals. Larger area scans reveal these spirals are aligned along step edges. It is predicted that these spirals originate from screw dislocations. Spiral growth is dependent on the density of surface steps and defects arising from mineral fracture. On ultra-flat surfaces with low step densities, no spirals were observed even after three hours of imaging. This work forms part of a study to characterize growth mechanisms and kinetics under different conditions and to investigate the properties of growth inhibitors.

REFERENCES

(1) - C. Hall, Society of Petroleum Engineers, paper SPE28996 (1995) 533-541

Re-printed from the Summer 1996 Applications Newsletter Volume 96-1 : For a hard copy, contact Support -
Jan McNerney janmc@topometrix..com

Other articles from the TopoMetrix Applications Newsletter - Summer 1996
[biofilm] Marine Sulfate Reducing Bacterium "AFM Studies of Bacterial Biofilms"
[folant]FOLANT Method Offers Unique Capabilities "Nanostructuring Using Combined Laser / STM"
[Magneto-Optic NSOM] Magneto-Optic NSOM "Magneto-optic Investigations With Aurora™ NSOM"
[NSOM res]Near-field Optical Microscopy "A Breakthrough in Resolution"

Home - Top