Nature of the changes in clay minerals of the high temperature drilling fluids
The mineral reactions in the sepiolite and palygorskite-based drilling fluids were systematically examined with X-ray diffraction and analytical electron microscopy before and after hydrothermal treatments. Both sepiolite and palygorskite were converted into smectites and other mineral phases in fluids containing either chlorides or hydroxides. The conversion rate usually increased with increasing temperature. Below 600/sup 0/F, the smectite occurred as thin films with irregular outlines with a high layer charge, whereas discs or platelets with hexagonal outlines were formed above 600/sup 0/F. The conversion of sepiolite (or palygorskite) to smectite at low temperatures (< 600/sup 0/F) was accomplished through epitaxial growth of smectite films around sepiolite (or palygorskite) fibers. At higher temperatures (> 600/sup 0/F), smectites and other new mineral phases were formed through a dissolution-precipitation mechanism. Smectite formed from sepiolite was chemically and structurally a trioctahedral variety; however, smectite formed in the palygorskite fluids consisted of trioctahedral and di-trioctahedral phases. The ditrioctahedral phase with approximately equal amounts of Al and Mg in the octahedral sheets was an unusual reaction product. The rheological properties of the fluids such as viscosity and fluid loss, were related to the mineralogical changes at elevated temperatures. The formation of smectite platelets, discs, and other new mineral phases obviously exerted a detrimental effect on the rheology of the fluids.
- OSTI ID:
- 5929322
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020300* -- Petroleum-- Drilling & Production
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CHEMICAL REACTIONS
CLAYS
COHERENT SCATTERING
DIFFRACTION
DRILLING FLUIDS
ELECTRON MICROSCOPY
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUELS
HIGH TEMPERATURE
MICROSCOPY
MINERALS
OXYGEN COMPOUNDS
PETROLEUM
RHEOLOGY
SCATTERING
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SMECTITE
VISCOSITY
X-RAY DIFFRACTION