Massive hydraulic fracturing well, Federal No. 498-4-1, Rio Blanco County, Colorado. Final report

This project is an MHF of a previously untreated Mesaverde interval in a well in northwest Colorado. The rocks involved may have been deposited during a marine invasion of long-continued, swamp environments. If so, they would have possessed superior primary reservoir properties. The logging program, identical to those used in the nearby Rio Blanco Nuclear and MHF Project wells, supplied contradictory information. The frac could furnish better understanding of the log suite, better parameters for pre-frac judgments of productive potential and further proof of the commercial capabilities of the formation. The frac job was performed as designed. A total of 775,000 lbs of sand in a total of 276,000 gallons of gelled water (YF4PSD) were injected. The injection pressures ranged from 2,000 to 1,300 psig at rates from 37 to 10 BPM. During the post-frac clean up, 30% of the frac fluid flowed back in 36 hours. Following eight days of swabbing and a total fluid recovery of 46%, the well began continuous flow, which within an additional three days brought total fluid recovery to 70%. Then gas flow increased from gas-cut water to 800 MSCF/D and declined to about 200 MSCF/D within 22 days. After over four months of production and cumulative frac fluid recovery of 82%, the gas rate appears to stabilize at around 130 MSCF/D with about 7 BF/D which contain over 50% oil. The post-frac to pre-frac production ratio is 2:1. It is concluded that revision of interpretive methods and/or logging programs is required if consistency in selecting zones most productive of gas and most receptive to stimulation is to be achieved. Injecting large volumes into short vertical intervals appears presently economically unattractive in this area. Properly designed moderate volume multiple fracs may achieve commercial deliverability