Paper: Recent Mechanical And Chemical Improvements In Foam Fracturing

Since the first foam fracturing treatment in approximately November of 1974, great strides have been made in both the technology of foam per se and the equipment to handle same. Countless numbers of papers, presentations and patents have been presented. A sampling of these is listed in the bibliography of this paper. The early foam fracturing treatments were conducted using water, foamer, and nitrogen injection trucks. The treatments were small and sand concentrations quite normally did not exceed two to three pounds per gallon downhole. It was always a very frightening experience for a company man, who had not been on a foam frac, to attend his first treatment. A company man who was used to visual read-out of both flow rate and pressure of all materials going down hole was in for quite a surprise on the early foam fracturing treatments. Nitrogen rate, which in many cases is produced by anywhere from 5 to 50 trucks, was measured by counting pump strokes on the units. A nitrogen treater would stand in the frac van and indicate to the company man what the rate was at all times. One could monitor with flowmeters, clean and dirty fluid rate of the base fluid to be pumped. But unless one was very trusting, one never really knew what was being pumped downhole. Without the benefit of both low-pressure and in-line high-pressure densiometers, one really never knew that the sand concentration was and because of the complexity of the density of the foam fluid there was very little in the way of checking same. In spite of all the aforementioned problems, many successful foam fracturing treatments, in fact hundreds, were conducted in just this manner. This says a great deal for the diligence of nitrogen treaters and fracturing operators. Quite thankfully, today foam fracturing is not such a black art. We in today's industry have quite functional in-line flowmeters for measuring the exact rate of nitrogen as it is pumped downhole. Most foam fracturing treatments should be conducted utilizing both in-line low-pressure densiometers for measurement of sand concentration in the concentrate as well as high-pressure in-line densiometers for measuring the final concentration of sand in the foam. Both of these measuring techniques, in addition to much improved sand handling capabilities from the service companies, utilizing either specialized valving in their pumps or sand concentrators, allow sand concentrations up to and including 8 pounds per gallon. Foam fracturing treatments have been conducted approaching two million pounds of sand with pump times well over 10 hours. Foam fracturing pump rates have varied anywhere from 5 barrels per minute up to 150 barrels per minute. Foam fracturing has indeed become another very useful tool for oil companies in the enhancement of production of oil and gas. Recently, a new development in this area has been the utilization of the emulsion foam/CO2 technique which has given new emphasis to energized gaseous foam fracturing.