FRACTURED RESERVOIR E&P IN ROCKY MOUNTAIN BASINS: A 3-D RTM MODELING APPROACH

Ortoleva, P. ; Comer, J. ; Park, A. ; Payne, D. ; Sibo, W. ; Tuncay, K.

Indiana University (United States)

关键词: Natural Gas;    Heat Flux;    Source Rocks;    Compressibility;    Hydrology;   

DOI  :  10.2172/834039
RP-ID  :  NONE
RP-ID  :  FG26-99FT40264
RP-ID  :  834039

美国|英语

来源: UNT Digital Library

【 摘 要 】

Key natural gas reserves in Rocky Mountain and other U.S. basins are in reservoirs with economic producibility due to natural fractures. In this project, we evaluate a unique technology for predicting fractured reservoir location and characteristics ahead of drilling based on a 3-D basin/field simulator, Basin RTM. Recommendations are made for making Basin RTM a key element of a practical E&P strategy. A myriad of reaction, transport, and mechanical (RTM) processes underlie the creation, cementation and preservation of fractured reservoirs. These processes are often so strongly coupled that they cannot be understood individually. Furthermore, sedimentary nonuniformity, overall tectonics and basement heat flux histories make a basin a fundamentally 3-D object. Basin RTM is the only 3-D, comprehensive, fully coupled RTM basin simulator available for the exploration of fractured reservoirs. Results of Basin RTM simulations are presented, that demonstrate its capabilities and limitations. Furthermore, it is shown how Basin RTM is a basis for a revolutionary automated methodology for simultaneously using a range of remote and other basin datasets to locate reservoirs and to assess risk. Characteristics predicted by our model include reserves and composition, matrix and fracture permeability, reservoir rock strength, porosity, in situ stress and the statistics of fracture aperture, length and orientation. Our model integrates its input data (overall sedimentation, tectonic and basement heat flux histories) via the laws of physics and chemistry that describe the RTM processes to predict reservoir location and characteristics. Basin RTM uses 3-D, finite element solutions of the equations of rock mechanics, organic and inorganic diagenesis and multi-phase hydrology to make its predictions. As our model predicts reservoir characteristics, it can be used to optimize production approaches (e.g., assess the stability of horizontal wells or vulnerability of fractures to production-induced formation pressure drawdown). The Piceance Basin (Colorado) was chosen for this study because of the extensive set of data provided to us by federal agencies and industry partners, its remaining reserves, and its similarities with other Rocky Mountain basins. We focused on the Rulison Field to test our ability to capture details in a well-characterized area. In this study, we developed a number of general principles including (1) the importance of even subtle flexure in creating fractures; (2) the tendency to preserve fractures due to the compressibility of gases; (3) the importance of oscillatory fracture/flow cycles in the expulsion of natural gas from source rock; and (4) that predicting fractures requires a basin model that is comprehensive, all processes are coupled, and is fully 3-D. A major difficulty in using Basin RTM or other basin simulator has been overcome in this project; we have set forth an information theory technology for automatically integrating basin modeling with classical database analysis; this technology also provides an assessment of risk. We have created a relational database for the Piceance Basin. We have developed a formulation of devolatilization shrinkage that integrates organic geochemical kinetics into incremental stress theory, allowing for the prediction of coal cleating and associated enhancement of natural gas expulsion from coal. An estimation of the potential economic benefits of the technologies developed or recommended here is set forth. All of the above findings are documented in this report.