Abstract

For several years the chemical industry has used diatomaceous earth system as a standard in effluent dewatering. Recognizing the similarities in clarity requirements between effluent dewatering and brine completion-fluid filtering, a new diatomaceous earth filtration system has been designed, tested, and is successfully being used in Gulf Coast operation.* The system consistently shows a one-pass solid efficiency of greater than 98%, at varying flow rates. Resulting solid concentrations average 74 parts per million (ppm, 0.007% by volume) and have been recorded as low as 10 pgm. This is a 40% improvement in removal efficiency and a filtrate that is 17 times cleaner, after one pass filtration, than the average of several existing cartridge units.

The efficiency of filtering high density brines is dependent upon several factors including the effectiveness of the filtration system, the physical characteristics of the brine and suspended solids, and operator experience.

Filtration removal efficiency and Industry standards for brine cleanliness can to modified to become more realistic and field-oriented. In future filter unit evaluations or comparisons, an absolute term of removal efficiency, which is defined by multivariable correlations through time, should be utilized. And rather than a maximum particle size standard, the Industry standards for brine cleanliness should be field-oriented and can be based on a concept of clarity and degree of contamination.

CONCEPT

The Diatomaceous Earth (DE) system is based on the concept of bed filtration. Bed filtration uses a porous and permeable bed as a filter media. The porous and permeable bed as a filter media. The concept is; that suspended solids will be removed by this media as the fluid passes through. The DE system includes the premise that the contaminating solids can themselves be used as part of the filter media.

FILTRATION RESULTS

Test results on brines ranging in weight from 11.1 ppg, CaCl2, to 14.4 ppg, CaCl2-CaBr2, demonstrate ppg, CaCl2, to 14.4 ppg, CaCl2-CaBr2, demonstrate an average removal efficiency of over 98%. The filtrate averaged 74 ppm remaining suspended solids after one filtration pass at varying flow rates. ibis is a 40% increase in removal efficiency and a filtrate that is 17 times cleaner, relative to remaining parts per million suspended solids, than recently tested per million suspended solids, than recently tested cartridge filters. A detailed comparison twill be presented later in the text. presented later in the text. The individual fluid samples recorded mean solids concentration values, removal efficiencies, and relative particle size distributions as shown in Table 1 as well as particle size midpoint average of contamination data as shown in Table 2. Figures 1 and 2 are field photographs illustrating the degree of particle removal by fluid clarity comparisons. particle removal by fluid clarity comparisons. Whereas, Figures 3 and 4 are photomicrographs of the 13.2 ppg filtration test comparing the solids contamination and relative size distribution of the particles in influent are effluent samples. A study of particles in influent are effluent samples. A study of the photomicrographs and the fluid analysis reports indicates that the DE filtration system removes the suspended solids immaterial of the particle size. Figures 5 through 7 are graphic illustrations of midpoint averages of contamination in terms of parts per million versus particle size, in microns, for each per million versus particle size, in microns, for each of the fluids. It should be noted that the up and downstream curves are very similar in configuration. This presentation also illustrates that approximately 90% of the suspended solids will range between 5 and 25 microns in size.

UNIT DESIGN

The DE unit presently utilized in Gulf Coast operations is a filter press design. The flow path of this type design is illustrated by Figure 8.

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