BRISTER, BRIAN S., New Mexico Bureau of Mines and Mineral Resources, Socorro, NM

ABSTRACT: Geological Criteria For Successful Waterfrac Stimulations And Potential Of The Lewis Shale, San Juan Basin, As Candidate

Low permeability, naturally fractured, gas charged formations have become common geological targets for exploration and development. Such reservoirs are typically marginally economic to drill, complete and produce until break-through technologies are applied. Waterfracs are high fluid volume (10,000 bbl or more) and low proppant volume (typically 1/2 lb/gal) slick-water hydraulic fracture treatments (fracs) designed to reduce stimulation costs for wells requiring massive fracs to access reservoir storage. Some examples of waterfrac applications are the Cretaceous Austin Chalk (success) of south Texas, Mississippian Barnett Shale (success) and Morrowan Marble Falls lime (success?) of the Fort Worth Basin, and the Cretaceous Cotton Valley sand (success) and Travis Peak sand (failure?) of the East Texas Basin. Geological criteria for success include- 1) Low permeability, 2) naturally fractured, 3) thick, 4) dry gas, 5) not depleted (good pressures), 6) low fluid sensitivity, and 7) sealed from water-bearing permeable or depleted zones.

There are a number of potential waterfrac candidates in the thick, source-rock shales of the Cretaceous western interior seaway in the Rocky Mountain region. The Lewis Shale of the San Juan Basin- I) is low permeability (microdarcy), 2) lies within a basin :veil known for fracture-enhanced production, 3) exceeds 1000 feet in thickness, 4) is thermally mature (gas window), and 5) is undepleted. Fluid sensitivity is an issue due to presence of bentonite beds. Careful design of fracs is required to keep the stimulation "in-zone" due to potential for fracture growth into water-bearing Fruitland Coal and partially depleted Mesaverde and Pictured Cliffs reservoirs.

AAPG Search and Discovery Article #90915©2000 AAPG Rocky Mountain Section, Albuquerque, New Mexico