The results of a joint research and field effort to develop commercial gas production from the very low permeability Muddy "J" Formation in the Wattenberg Field near Denver, Colorado, by the application of MHF (Massive Hydraulic Fracturing) are presented.
The Muddy "J" Formation is approximately 50 ft thick and found at a depth of about 8,000 ft. The bottom-hole temperature in these wells is 260 ° F. Initial attempts to develop the gas potential in this field were made by stimulating wells with 40,000 to 50,000 gal gelled water fracturing treatments. These efforts resulted in increased gas production; however, the rapid decline of gas production rates with timeindicated that the stimulations would be economic failures.
Laboratory studies were made to evaluate various fracturing fluids and to investigate fracture flow capacity with various proppant plans. Using these studies, a stimulation program was developed which utilized a polymer emulsion fracturing fluid. Treatments with up to 500,000 gal of fluid and 1,000,000 lbs of sand have been conducted. Field case h1scories are discussed and the results of MHF treatments are compared with the conventional fracturing treatments.
It was found that the well and treatment payout time was inversely proportional to the treatment size in the better areas of the field showing that the larger treatments are more desirable than the smaller ones. In the poorest areas of the field, well and treatment payout is indefinite at the current interstate gas price.
With an increased demand for gas, better wellhead gas price and improved technology, the energy companies are now devoting more attention to the "tight" gas reservoirs heretofore considered noncommercial. Amoco is one such company, and the Wattenberg Field of Colorado is a reservoir which typifies the "tight gas reservoir". Through advancements in fracturing technology, Wattenberg is now considered commercial.
The Wattenberg Field is located in the western portion of the D-J Basin in Adams and Weld Counties, Colorado, and comprises an area of 980 square miles (627,000 acres). The field was discovered in 1970 and for the past two years has been under intense development with approximately 48O gas wells having been drilled by various companies. Amoco, however, is the major operator having drilled over 300 wells to date.
The Muddy "J" Formation of Cretaceous age is the major gas producing zone in Wattenberg.1 This blanket type of extremely low permeability (0.05 to 0. 005 md) is round at depths ranging from 7600 ft to 80400 f t (sec Table 1 for other pertinent data). The reservoir is stratigraphically controlled by sand pinchont to tile southwest: and loss in permeability to the northeast. Natural productivity from this very tight formation ranges from a small show of gas to 100 MCFD.
One of the most significant aspects of the Wattenberg Muddy "J" development program has been the unlocking of gas reserves from this formation through new hydraulic fracturing technology. Wattenberg has been the stage for the evolution of "Massive Hydraulic Fracturing" (MHF).