The Application of Massive Hydraulic Fracturing to the Tight Muddy "J" Formation, Wattenberg Field, Colorado
Authors: Fast C.R. , Holman G.B. , Covlin R.J. 
Published: December 2007

Laboratory and field research in Colorado's Wattenberg field showed that commercial gas production was feasible from the very tight Muddy "J" formation using massive hydraulic fracturing. Results indicate that the largest treatments are economically justified in the better areas of the field.

Introduction

This paper presents the results of a joint research and field effort to develop the very low permeability (0.05 to 0.005 md) Muddy "J" formation in the Wattenberg field by the application of massive hydraulic fracturing (MHF). In this paper, MHF is defined as having a vertical fracture penetration of more than 1,500 ft in each direction from the wellbore. Wattenberg gas production is from the very tight Muddy "J" formation, which is about 50 ft thick and is found at a depth of about 8,000 ft. The bottom-hole temperature in Wattenberg wells is 260 deg. 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 that used a polymer emulsion fracturing fluid and a pillar proppant placement technique. Treatments with up to 500,000 gal of fluid and 1,000,000 lb of sand were conducted. Field case histories are discussed and the results of MHF treatments are compared with those of conventional fracturing treatments. In addition, shut-in temperature logs run before and after treatment, production performance, and mechanical rock properties were evaluated. This information clearly indicates that the largest treatments are economically justified in the better areas of the field, and the fracture penetration is on the order of 3,000 ft.

Field Description

With an increased demand for gas, better wellhead gas prices, and improved technology, energy companies prices, and improved technology, energy companies are now devoting more attention to the "tight" gas reservoirs heretofore considered noncommercial. The Wattenberg field near Denver is a reservoir that 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, Colo., and comprises an area of 980 sq miles (627,000 acres) The field was discovered in 1970. During 1974 and 1975 it was under intense development, with approximately 480 gas wells drilled by various companies. Amoco Production Co. is the major operator, with more than 300 Production Co. is the major operator, with more than 300 wells drilled.

The Muddy "J" formation of Cretaceous age is the major gas producing zone in Wattenberg. This blankettype sand of extremely low permeability (0.05 to 0.005 md) is found at depths ranging from 7,600 to 8,400 ft (see Table 1 for other pertinent data). The reservoir is stratigraphically controlled by sand pinchout to the southwest and loss in permeability to the northeast. Natural productivity from this very tight formation ranges from a small productivity from this very tight formation ranges from a small show of gas to 100 Mcf/D.

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