The results of a joint research and field effort to develop commercial gas production from the very low permeability Muddy "J" Formation in the Watten-berg Field near Denver, Colorado, by the application of MHF (M assive 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 time indicated 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 histories are discussed and the results of MHF treatments are compared with the conventional frac-turing t reatments. 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 inter-state gas price. INTRODUCTION With an increased demand for gas, better well-head gas price and improved technology, the energy companies are now devoting more attention to the "tight" gas reservoirs heretofore considered non-commercial. Amoco is one such company, and the Wattenberg Field of Colorado is a reservoir which typifies the "tight gas reservoir". Through advance-ments 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