Effectiveness of Different Hydraulic Fracturing Treatments in Low Permeability Reservoirs

Abstract

This paper was prepared for the 48th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, held in Las Vegas, Nev., Sept. 30-Oct. 3, 1973. Permission to copy is restricted to an abstract of not more than 30 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract Various hydraulic fracturing techniques (high viscosity fluid, oil in water dispersion, oil and water emulsion, large water volume, and the common standard water fracturing methods) have been used in the completion of oil wells in reservoirs that have low permeability (less than 1 millidarcy). Reservoir information from over 100 wells in the same geographical area, such as production records, bottom-hole pressure buildup tests, and geophysical well pressure buildup tests, and geophysical well logs were used to determine the effectiveness of different fracturing techniques. Two independent methods were used in the analysis. First, data from well interference tests and bottom-hole pressure tests were used to calculate effective fracture lengths. Although fracture length depends on many factors in addition to fracture technique "type"— type of rock, pressures, volumes of fluid, etc.—it was found that a standard water fracturing method with similar volumes of fluid and sand produced various fracture lengths. The horizontal distance calculated for these vertical fractures varied from 100 to about 1,000 feet in length. In the second method of analysis, the effects of five different hydraulic well fracturing procedures on long-term oil production were studied using a statistical production were studied using a statistical model called analysis of multiple covariance. The results indicated that the oil and water emulsion fracturing technique produced from 34 to over 100 percent more oil than any of the other techniques, with the standard water fracturing method being second best. Both described evaluations indicate the complexity of choosing an induced hydraulic fracture treatment that will be most effective for the recovery of oil from low permeability reservoirs. Introduction Induced hydraulic fracture treatments have added approximately 8 billion barrels of oil to this Nation's reserves during the 25-year period from 1946 to 1970. The total oil added period from 1946 to 1970. The total oil added to reserves during this period of time was 72 billion barrels; therefore, fracture treatments accounted for about 11 percent of this increase.