Reservoir Studies of the Seltjarnarnes Geothermal Field, Iceland

The Seltjarnarnes geothermal field in Iceland has been exploited for space heating for the last 16 years. A model of the field has been developed that integrates all available data. The model has been calibrated against the flow rate and pressure decline histories of the wells and the temperature and chemical changes of the produced fluids. This has allowed for the estimation of the permeability and porosity distribution of the system, and the volume of the hot reservoir. Predictions of future reservoir behavior using the model suggest small pressure and temperature changes, but a continuous increase in the salinity of the fluids produced. 10 figs., 23 refs

Integrated TEM, XRD and electron-microprobe investigation of mixed-layer chlorite smectite from the Point-Sal ophiolite, California

Five basalt samples from the Point Sal ophiolite, California, were examined using HRTEM and AEM in order to compare observations with interpretations of XRD patterns and microprobe analyses. XRD data from ethylene-glycol-saturated samples indicate the following percentages of chlorite in mixed-layer chlorite-smectite identified for each specimen: (i) L2036 almost-equal-to 50%, (ii) L2035 almost-equal-to 70 and 20%, (iii) 1A-13 almost-equal-to 70%, (iv) 1B-42 almost-equal-to 70%, and (v) 1B-55 = 100%. Detailed electron microprobe analyses show that 'chlorite' analyses with high Si, K, Na and Ca contents are the result of interlayering with smectite-like layers. The Fe/(Fe + Mg) ratios of mixed-layer phyllosilicates from Point Sal samples are influenced by the bulk rock composition, not by the percentage of chlorite nor the structure of the phyllosilicate. Measurements of lattice-fringe images indicate that both smectite and chlorite layers are present in the Point Sal samples in abundances similar to those predicted with XRD techniques and that regular alternation of chlorite and smectite occurs at the unit-cell scale. Both 10- and 14-angstrom layers were recorded with HRTEM and interpreted to be smectite and chlorite, respectively. Regular alternation of chlorite and smectite (24-angstrom periodicity) occurs in upper lava samples L2036 and 1A-13, and lower lava sample 1B-42 for as many as seven alternations per crystallite with local layer mistakes. Sample L2035 shows disordered alternation of chlorite and smectite, with juxtaposition of smectite-like layers, suggesting that randomly interlayered chlorite (< 0.5)-smectite exists. Images of lower lava sample 1B-55 show predominantly 14-angstrom layers. Units of 24 angstrom tend to cluster in what may otherwise appear to be disordered mixtures, suggesting the existence of a corrensite end-member having thermodynamic significance

Assessment of lacustrine/fluvial clays as liners for waste disposal (Lake Van Basin, Turkey)

Potential use of lacustrine/fluvial type clays in Lake Van Basin (Turkey) as liner material is investigated by studying their chemical, mineralogical and technological properties. The results show dominant clay minerals being Ca-smectite along with illite, swelling chlorite, and chlorite. Na-smectite, palygorskite, and kaolin group minerals with lesser quantities are also determined in some samples. Cation exchange capacities of samples are between 12 and 23 meq/100 g; plasticity index is between 13 and 39%; calculated hydraulic conductivity is between 2.7 x 10(-9) and 4.5 x 10(-11); volumetric swelling capacity is between 6 and 10%. It is concluded that clays in the basin have suitable properties to be used as liner materials, with some localities having better clays as liner materials than the others. The results also indicate economical potential of fluvial/lacustrine clays and highlight their important role in sustainable development of environmentally sensitive areas, among them the Lake Van Basin itself