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Collaborating Authors
Results
Abstract Prediction and analysis of the coalbed methane (CBM) production ischallenging especially at the early stages of the recovery when production issubject to two-phase flow conditions. CBM reservoirs are dual-porosity systemsthat are characterized by a complex interaction of coal matrix and cleat systemthat are coupled through desorption process. As a result, the conventionalmethods cannot be utilized to predict CBM production. Currently, only numericalmodels (simulators) can be used to predict (CBM) production behavior since theyincorporate the unique flow and storage characteristics of CBM reservoirs. Often, the number of variables needed for evaluation of a given prospect isgreater than that typically measured. In such cases, parametric studies areconducted to evaluate the impacts of reservoir properties on recovery factor, well performance, and future revenues. However, parametric studies with areservoir simulator is cumbersome, time consuming and expensive. Therefore, there is a need for scientific, user-friendly tools that can assist the typicalgas producers in evaluation of CBM prospects. This study presents a set of production type curves for CBM reservoirs. Areservoir model that incorporates the unique flow and storage characteristicsof CBM reservoirs was employed to generate the type curves. Our previous study(SPE 91482) introduced a new set of dimensionless groups that led todevelopment of unique set of type curves. The impact of basic reservoircharacteristics was also investigated to confirm the uniqueness of the typecurves. This study investigates the impact of key parameters including isothermconstants and relative permeability data on the type curves. The type curvescan be used to predict and/or analyze gas and water the production from CBMwells both during de-watering and stable gas production phases. The issuesconcerning the application and limitation of the type curves are alsopresented. Finally, a type curves-based simple yet reliable tool with graphicaluser interface (GUI) was developed. This tool can be used for predictingand analyzing production performance of CBM reservoirs with simple and straightforward input requirements. This tool is particularly useful for parametricstudies to evaluate CBM prospects. Introduction CBM has grown from an unconventional gas play in the 1980's into acommercially important, mainstream natural gas source. CBM proven reserves inthe United States have increased from 3.7 Tcf in 1989 to 18.75 Tcf in 2003 andcurrently account for over 10 percent of the estimated total U.S. natural gasreserves. This number is expected to increase even further as more resourcesare discovered and a better understanding of the existing resources isachieved. The contribution of CBM to U.S. annual gas production has exceeded 8percent and is expected to increase for next two decades. However, for CBM toreach its true potential in the U.S. energy equation, substantial increase inCBM production in less developed basins, such as the Northern AppalachianBasin, must be achieved. Therefore, it is necessary to develop tools that makeit possible for producers to seriously consider this important resource. Thereis a need for scientific, user-friendly tools that can assist the typical gasproducers in evaluation of CBM prospects.
Abstract Coalbed Methane (CBM) currently accounts for nearly 8 percent of U.S. annual gas production and approximately 12 percent of estimated total U.S. natural gas reserves. Coalbed methane proven reserves in the United States have increased from 3.7 Tcf in 1989 to 18.5 Tcf in 2002. This number is expected to increase even further as more resources are discovered and a better understanding of the existing resources is achieved. Appalachian Basin accounts about 10 percent of U.S. CBM resources. However, CBM production is very limited in the Appalachian Basin. The contribution of CBM to overall mix of natural gas sources in U.S. is expected to increase for next two decades. However, this cannot be achieved without substantial increase in CBM production in the Appalachian Basin. The problems causing the lag in development of CBM in the Appalachian Basin need to be overcome for CBM to reach its true potential in the U.S. energy equation. Gas production from CBM reservoirs is governed by complex interaction of single-phase gas diffusion through micro-pore system (primary porosity) and two-phase gas and water flow through cleat system (secondary porosity) that are coupled through desorption process. In order to effectively evaluate CBM resources, it necessary to utilize reservoir models that incorporate the unique flow and storage characteristics of CBM reservoirs. These models are often complicated to use, expensive, and time consuming. The typical gas producers in the Appalachian Basin suffer from the lack of scientific, user-friendly tools that can assist them in development of CBM resources. Therefore, it is necessary to develop tools that make it possible for typical (small to medium size) producers to seriously consider this important resource. This study presents a set of production type curves that would help the producers to predict the production from their CBM wells. As a consequence, the producers would be able to make better, more informed decisions regarding the CBM resources in the region. A reservoir model that incorporates the unique flow and storage characteristics of Coalbed Methane reservoirs was employed in this study to develop the type curves. The type curves provide a reliable tool to predict the production performance of CBM reservoirs both during de-watering and stable gas production phases. The application and issues concerning the production performance of CBM reservoirs are also discussed. Introduction After a humble beginning in the 1980's, coalbed methane (CBM) has become a significant natural gas resource worldwide. Presently CBM accounts for 8 percent of total annual U.S. dry gas production and 12 percent of estimated total recoverable U.S. natural gas resource base. The contribution of coalbed methane to the overall mix of natural gas resources in the U.S. is expected to increase in the next two decades. Northern Appalachian Basin, which is comprised mainly of large areas of West Virginia, Pennsylvania, and Ohio, is one of the most potential basins in United States. The basin's CBM resources have been estimated to be 61 Tcf. To date, CBM production in the basin however has been virtually non-existent. The projected increase in CBM production in US cannot be realistically achieved without a substantial increase in CBM production in the Northern Appalachian Basin. The technical problems and uncertainties causing the lag in development of CBM in the Northern Appalachian Basin need to be overcome for CBM to reach its true potential in the U.S. energy equation. The typical gas producers in the Northern Appalachian Basin suffer from the lack of scientific, user-friendly tools that can assist them in development of CBM resources. Therefore, it is necessary to develop essential tools that make it possible for the operators to realistically evaluate and characterize coalbed methane reservoirs.
- North America > United States > West Virginia (1.00)
- North America > United States > Virginia (1.00)
- North America > United States > Pennsylvania (1.00)
- (3 more...)
- Geology > Structural Geology > Tectonics > Compressional Tectonics > Fold and Thrust Belt (1.00)
- Geology > Rock Type > Sedimentary Rock (0.68)
- North America > United States > West Virginia > Appalachian Basin (0.99)
- North America > United States > Virginia > Appalachian Basin (0.99)
- North America > United States > Tennessee > Appalachian Basin (0.99)
- (7 more...)