TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe U.S. Department of Energy (DOE), National Energy Technology Laboratory has been conducting research on low permeability gas reservoirs for over 30 years. Major field experiments like the multiwell experiment and the multi-site experiment at Rifle, Colorado, have provided tremendous insight into the characterization of low permeability gas sands, the associated natural fracture network, and the implications of hydraulic fracturing. Since the early 1990's, the DOE has focused its research efforts on developing technologies and methodologies to detect and characterize natural fractures in the subsurface and on demonstrating methods for enhancing production.Several successful technology advances are expected to have significant impact on the recovery of natural gas from low permeability formations. A horizontal well recently completed at 15,000 feet in the Frontier Formation in Wyoming, in conjunction with Union Pacific Resources (UPR), initially flowed 14 MMcfd and in the first 9 months recovered 2.75 Bcf of gas. UPR has two more wells underway and plans to drill additional wells based on the success of this project. Natural fracture detection techniques have been successfully demonstrated in existing fields in the Piceance and Wind River basins. An integrated 3-D seismic and geomechanical modeling approach was demonstrated in the Piceance basin and more recently in conjunction with the horizontal well drilled by UPR/DOE. The use of 3-D seismic attributes was demonstrated in the Wind River Basin.DOE initiated several new projects to begin work in October 1999 that will (1) demonstrate the use of natural fracture detection technologies as an exploration tool and (2) advance the state-of-the-art in natural fracture detection by developing new techniques to quantify fracture properties that control the flow and transport of gas. This paper will provide a detailed discussion for the projects that have recently been completed and for the new projects along with their implications for enhancing gas production from low permeability gas reservoirs.

The U.S. Department of Energy (DOE), National Energy Technology Laboratory has been conducting research on low permeability gas reservoirs for over 30 years. Major field experiments like the multiwell experiment and the multi-site experiment at Rifle, Colorado, have provided tremendous insight into the characterization of low permeability gas sands, the associated natural fracture network, and the implications of hydraulic fracturing. Since the early 1990's, the DOE has focused its research efforts on developing technologies and methodologies to detect and characterize natural fractures in the subsurface and on demonstrating methods for enhancing production. Several successful technology advances are expected to have significant impact on the recovery of natural gas from low permeability formations. A horizontal well recently completed at 15,000 feet in the Frontier Formation in Wyoming, in conjunction with Union Pacific Resources (UPR), initially flowed 14 MMcfd and in the first 9 months recovered 2.75 Bcf of gas. UPR has two more wells underway and plans to drill additional wells based on the success of this project. Natural fracture detection techniques have been successfully demonstrated in existing fields in the Piceance and Wind River basins. An integrated 3-D seismic and geomechanical modeling approach was demonstrated in the Piceance basin and more recently in conjunction with the horizontal well drilled by UPR/DOE. The use of 3-D seismic attributes was demonstrated in the Wind River Basin. DOE initiated several new projects to begin work in October 1999 that willdemonstrate the use of natural fracture detection technologies as an exploration tool andadvance the state-of-the-art in natural fracture detection by developing new techniques to quantify fracture properties that control the flow and transport of gas. This paper will provide a detailed discussion for the projects that have recently been completed and for the new projects along with their implications for enhancing gas production from low permeability gas reservoirs. Introduction As new discoveries from conventional supplies decline, future supplies of natural gas will increasingly have to come from low permeability (tight) reservoirs. Basins containing significant resources and reserves include the Greater Green River, Piceance, Wind River, Uinta, and Anadarko. Other basins and plays also hold large resources of gas. The 1992 National Petroleum Council's (NPC) natural gas study1 concluded that 232 Tcf could be technically recoverable from low permeability sand formations. Assuming that technology improvements continued, the NPC estimated that 349 Tcf could be produced. In their most recent study2, the NPC states that "deeper wells, deeper water and nonconventional sources will be the key to future supply." Nonconventional production in the Rocky Mountain region is projected to increase by 1 Tcf per year by 2010 and as much as 1.5 Tcf per year by 2015. Significant technology hurdles must be addressed and overcome to assure a cost-competitive supply from these sources. Gas production from low permeability formations is hindered by the formations' capability to allow gas to flow to the wellbore. Hence, economic production of natural gas can only occur where the flow path to the wellbore is enhanced. Geologic processes have created natural fractures in most formations that provide channels for gas to flow. In areas where the natural fracture network is extensive and dense, economic production can be achieved without wellbore enhancements. However, most low permeability formations require hydraulic fracturing to connect the wellbore to the formation to allow commercial production. The challenges facing industry are locating the areas of dense fracture networks and determining whether horizontal wells or vertically stimulated wells are more economical.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractMajor studies completed by the U.S. Department of Energy/ National Energy Technology Laboratory (NETL) have documented or demonstrated advances for improved storage deliverability and new storage facilities. These technological advances are very important for maintaining the reliability of the natural gas infrastructure since energy forecasts predict that the Nation's demand for natural gas is likely to exceed 30 Tcf per year by 2015. The anticipated growth in electricity generation demand for natural gas will require the delivery system to be re-optimized to meet larger off-peak swing loads as well as peakday requirements that could increase from 111 Bcf per day (1997) to 152 Bcf per day by 2015.Four new and novel fracture stimulation technologies -liquid CO 2 with proppant, propellant, tip-screenout, and extreme overbalanced fracturing -were tested in eight different storage fields. In total, 29 fracture treatments were performed as part of the project. Several of these new and novel stimulation technologies provided attractive deliverability enhancement results and addressed the special concerns of gas storage operators. Three new projects were started in the fall of 1999 to investigate improved remedial treatment technologies.Studies of the technical and economic merits of four advanced storage concepts were also completed. Three of these new or improved storage methods can provide storage in areas where conventional storage is not available or does not meet the requirements of end-users. The large-scale projects, lined rock caverns and refrigerated-mined caverns, have been shown to be superior to LNG storage when using several cycles. A feasibility study of storing gas as hydrates found that a single formation and decomposition cycle could be achieved within 24 hours in a 2.25-MMcf process. Using an advanced constitutive model developed for nuclear waste isolation in salt, the fourth study found that minimum working gas pressure in most existing salt cavern storage facilities can be lowered 10 percent without compromising cavern stability. Extrapolating these results across the salt cavern industry would result in a 17-Bcf increase in storage capacity with no changes to existing infrastructure. A fifth study, initiated in 1999, is investigating the feasibility of storing gas in basalt aquifers.

Major studies completed by the U.S. Department of Energy/National Energy Technology Laboratory (NETL) have documented or demonstrated advances for improved storage deliverability and new storage facilities. These technological advances are very important for maintaining the reliability of the natural gas infrastructure since energy forecasts predict that the Nation's demand for natural gas is likely to exceed 30 Tcf per year by 2015. The anticipated growth in electricity generation demand for natural gas will require the delivery system to be re-optimized to meet larger off-peak swing loads as well as peak-day requirements that could increase from 111 Bcf per day (1997) to 152 Bcf per day by 2015. Four new and novel fracture stimulation technologies - liquid CO2 with proppant, propellant, tip-screenout, and extreme overbalanced fracturing - were tested in eight different storage fields. In total, 29 fracture treatments were performed as part of the project. Several of these new and novel stimulation technologies provided attractive deliverability enhancement results and addressed the special concerns of gas storage operators. Three new projects were started in the fall of 1999 to investigate improved remedial treatment technologies. Studies of the technical and economic merits of four advanced storage concepts were also completed. Three of these new or improved storage methods can provide storage in areas where conventional storage is not available or does not meet the requirements of end-users. The large-scale projects, lined rock caverns and refrigerated-mined caverns, have been shown to be superior to LNG storage when using several cycles. A feasibility study of storing gas as hydrates found that a single formation and decomposition cycle could be achieved within 24 hours in a 2.25-MMcf process. Using an advanced constitutive model developed for nuclear waste isolation in salt, the fourth study found that minimum working gas pressure in most existing salt cavern storage facilities can be lowered 10 percent without compromising cavern stability. Extrapolating these results across the salt cavern industry would result in a 17-Bcf increase in storage capacity with no changes to existing infrastructure. A fifth study, initiated in 1999, is investigating the feasibility of storing gas in basalt aquifers. Introduction Most natural gas consumed in the U.S. is not produced in the areas where it is most needed. To get gas to the customers, the Nation uses 1.5 million miles of natural gas pipelines capable of moving 111 billion cubic feet (Bcf) of gas daily. However, the amount of gas needed varies at time scales much shorter than can be accommodated by the production and pipeline systems. In general, demand varies seasonally, but the exact timing and magnitude of peak demand is largely determined by the weather, and is therefore unpredictable. As a result, gas is injected into more than 400 storage reservoirs, located near the points of demand, each year from April through October. Roughly 3.8 trillion cubic feet (Tcf) of storage gas is available to help meet peak demands. Pipelines and storage work together to comprise a natural gas distribution system that efficiently balances the need for steady year-round production with seasonal variation in use.