Calcite Scale Research Articles

Magnetic Treatment of Water–A Theoretical Quantum Model

It is claimed that magnetic treatment of water can prevent formation of hard calcite scale on the walls of hot–water containers, and devices based on this phenomenon are already commercially for industrial use. The present paper puts forward and examines a theoretical model with a view to explain why the low–energy magnetic field of a permanent magnet is effective at all and why the phenomenon persists for some time after the treatment (memory effect).

Training in industrial uses of geothermal energy

Specialized training in industrial uses of geothermal energy is available in Iceland. The Geothermal Training Programme of the United Nations University (UNU) has operated in Iceland since 1979 with six months' annual courses for professionals in either Geological Exploration, Borehole Geology, Geophysical Exploration, Borehole Geophysics, Reservoir Engineering, Chemistry of Thermal Fluids, Geothermal Utilization, or Drilling Technology. The trademark of the training is to give university graduates with some practical experience in geothermal work, intensive on-the-job training in their specialization. Industrial applications of geothermal resources is one of the options open to participants in the Geothermal Utilization course. Participants selecting this option have mainly been trained in drying processes and how to adapt the design of conventional steam or hot water/air drying systems to the specific characteristics of the geothermal fluids. One participant studied food drying using low-temperature geothermal energy, and two dealt with heat exchanger selection for geothermal applications and the merits of the combined use of geothermal resources for electricity production and industrial utilization. Of other options directly relevant to industrial applications can be mentioned the selection, installation, and operation of downhole pumps in geothermal wells, the prediction of calcite scaling, and materials selection.

Scale Control Aids Gas Recovery

The East Hitchcock field has produced natural gas since 1958. Toward the end of the primary production phase, the wells watered out and formed excessive amounts of calcite scale. Acidizing was required frequently. In recent years, some of these wells were recompleted for coproduction. Because large volumes of brine are produced, scale control is necessary. Prets Unit No. 1 was successfully treated by an inhibitor squeeze, while Thompson Trustee Unit No. 1 was completed with two treat strings installed at calculated depths to administer scale inhibitor downhole. An inhibitor squeeze protects the formation and the perforations as well as the production tubing, surface equipment, and disposal system. Periodic interruption of production, however, is required to repeat the squeeze, and the concentration of inhibitor in the produced brine is controlled by the chemistry of the inhibitor salt. Installation of treat strings requires that the tubing be pulled and reinstalled with the treat strings clamped to the tubing OD. The concentration of inhibitor in the effluent brine is controlled by a surface injection pump connected at the top of the treat string.

Carbonate scaling characteristics in Dixie Valley, Nevada geothermal wellbores

Calcite scale deposits in seven wellbores were logged with Schlumberger's multifinger caliper. The bottom of the scale is found at the deepest flash point. It thickens to a maximum in 46 to 107 m and then diminishes over a total length of 290 to 518 m. Scale deposition rates range from 267 to 911 kg of fluid produced for each cm 3 of scale deposited. The dominant variable controlling the deposition rate is the pre-flash calcium content which increases with decreasing fluid entry temperature. Data from one pair of wells indicate a 22.44 cm (I.D.) wellbore can have an initial scale deposition rate about 30 % greater than a 31.53 cm wellbore. Downward movement of the flash point lengthens the scaled interval. Estimated times between scale cleanouts should be 3 to 4 months for wells with 22.44 cm production casing and 6 to 12 months for wells with 31.53 cm casing.

The Role of Bicarbonate Ion in Calcite Scale Formation

Summary In this paper, we study the influence of the seed surface area, supersaturation ratio, bicarbonate ion concentration, and pH on the calcite precipitation rate. All other things being constant, the rate is a nearly linear function of seed surface area and supersaturation ratio. The rate also, surprisingly, depends on the concentration of bicarbonate ion, which is not a thermodynamically relevant species. There is no discernable effect of pH on the rate after the effects of pH on the supersaturation ratio and bicarbonate ion concentration are accounted for.

A downhole gas separator for methane production from geopressured aquifers

The downhole gas separator is a semipermeable device that produces methane gas from solution in brine by a diffusion process. It is in the form of a 6 in (15·2 cm) diameter, 1000 ft (303 m) long cylinder located downhole near the brine/methane-producing formation. As brine flows upward past the separator, 90 percent of the brine methane is extracted while 60 percent and 19 percent of the brine carbon dioxide and hydrogen sulfide, respectively, are extracted. The preferential extraction of methane over carbon dioxide and hydrogen sulfide, achieves a purification of the product gas. Subsequently, the brine flows further upward and into a shallower disposal reservoir penetrated by the same wellbore; surface brine handling is entirely eliminated. The separator is assembled at the wellhead from one hundred 10 ft (3 m) long segments in the fashion of a production string. Because of operations at near bottomhole pressures, maintenance requirements due to calcite scale are reduced substantially over surface-type equipment.