DOE Digest

Unconventional Gas, Fractured Reservoirs and Infill Drilling

DOE recently announced that New Mexico Tech has completed a five-year study for optimization of infill drilling in naturally fractured tight gas reservoirs for the San Juan Basin. Their final report indicates that optimal infill drilling could increase gas recovery anywhere from 23 to 46 percent. In the San Juan Basin well/reservoir productivity varies greatly. Natural fractures and their associated reservoir permeability and permeability anisotropy influence drainage efficiency and infill well potential.

The study generated a wealth of information about optimizing infill drilling and developed a simple to use Infill Well Location Calculator (http://
octane.nmt.edu/software/Infill.asp) designed specifically for small independents. The study also demonstrated a methodology to define the elliptical drainage area and recoverable gas for existing wells, evaluate hydraulic fracture simulation treatments and their impact on well drainage area and infill well potential, determine the optimal location and number of new infill wells to maximize economic recovery, and forecast the increase in total cumulative gas production from infill drilling.

Following an initial small-scale study of the Blanco Mesaverde reservoir with one operator, New Mexico Tech began working with other producers in 1998 through a cooperative agreement with DOE. They conducted a basin-wide study for both the Mesaverde and Dakota formations. The objective of this project was to develop a methodology to determine optimum well spacing, patterns, and type (vertical or horizontal) to maximize gas recovery from naturally fractured tight gas reservoirs.

Burlington Resources and BP were granted permission to site new well locations based on drainage area and drainage pattern of previously drilled wells. Typically, wells are drilled on a given well spacing and pattern (usually square) specified by the regulatory agency. For certain formations, gas operators have been able to convince the commission to reduce well spacing so that additional reserves could be produced. This was the first approved deviation in the Mesaverde tight gas sandstone reservoirs in the San Juan Basin, and the approval was a direct result of this project.

Several independent gas operators have approached New Mexico Tech

• GasTIPS: A quarterly publication, produced in partnership between the Strategic Center for Natural Gas & Oil and the Gas Technology Institute, that highlights natural gas technology research in the gas exploration, production, and processing areas.

• Fire in the Ice: A quarterly publication highlighting the National Methane Hydrate R&D Program

• Class Act: A publication highlighting DOE's Reservoir Class Program

• Eye on Environment: A publication highlighting DOE's Oil and Gas Environmental Research Program

Logon to www.netl.doe.gov/scngo/
index.html.

Researchers at the Bureau of Economic Geology, the University of Texas at Austin, and the New Mexico Bureau of Geology and Mineral Resources have completed a new digital oil-play portfolio of the major Permian Basin oil reservoirs. The portfolio was developed as part of DOE's Preferred Upstream Management Practices Program.

The portfolio defines 32 oil plays in the Permian Basin and assigns all reservoirs that had cumulative

production of > 1 million barrels through 2000 to a play. Each of the 1,339 reservoirs was mapped in a GIS system. The portfolio contains a summary description of each play including illustrations of key reservoir characteristics and reservoir data tables. This new portfolio updates and expands the information in the pioneering volume Atlas of Major Texas Oil Reservoirs (Galloway and others, 1983), which included only reservoirs in the Texas part of the Permian Basin that had produced more than 10 million barrels of oil.

The draft final report (pdf format) to DOE, the reservoir database (Excel format), and PDF versions of the play maps are available online at www.beg.utexas.edu/
resprog/permianbasin/play
analysis.htm. The report will be published as a BEG Report of Investigations on a CD-ROM containing the database of reservoirs within each play, maps in Geographic Information Systems (GIS) format showing play outlines and reservoir locations, and summary information on reservoir heterogeneity and development practices.

DOE is seeking proposals for its Microhole Technology Development II solicitation scheduled to close Oct. 6, 2004. FIELD DEMONSTRATION proposals should demonstrate drilling well(s) using coiled tubing (MHT) drilling technology. Proposals must meet several conditions. One award—up to $1,000,000 of DOE money (50% cost share required)— is anticipated for drilling of at least three wells during a one-year period. TECHNOLOGY DEVELOPMENT proposals should address developing new tools in the areas of advanced monobore concepts, microhole coiled tubing bottom hole assembles, and microhole completion and production equipment. Multiple awards are anticipated in each area. Projects should take no more than three years. Being development rather than demonstration, only 20% cost share is required.

Full solicitation information available on DOE NETL's website www.netl.doe.gov/business/
solicit/index.html.