This paper describes the efforts to compile the current understanding of recommended practices for static and dynamic modeling in tight gas sandstone reservoirs. One of the developed frameworks is applied in the Moxa Arch in southwestern Wyoming to generate a full field simulation model to guide informed decisions on well spacing and infill drilling locations while differentiating between incremental volumes and rate acceleration.
The proposed frameworks have been developed by a multidisciplinary group of experts from the technology group and the North America Gas business at BP. They are based on a range of business problems such as drilling and completions design, spacing, pattern and location of infill wells, and depletion planning. The frameworks provide step by step guidelines as to how a modeling study should be conducted in order to meet certain reservoir management objectives. A decision tree is initially suggested which guides the user through the different characteristics of the modeling study in order to select what framework to employ. Five general frameworks have been differentiated by geologic complexity and number of wells with an underlying business objective. Each framework is then subdivided based on the impact on productivity of gas condensate and water dropout and mobility in the reservoir or the well. It is expected that these frameworks can be used to provide guidelines in starting a modeling project from scratch and identify gaps between the recommended practice and ongoing modeling efforts that could yield erroneous results.
The framework corresponding to the multi-well, full field simulation model with complex geology has been tested and used to guide the progress of a modeling study in Moxa. The model integrates results of recent geological, petrophysical, classical reservoir engineering, and production performance studies with the simulator. 2D models of the Frontier and Muddy formations are run on predictive mode with wells controlled by rate based on decline curve analysis and remaining gas maps are generated to identify undepleted areas with infill drilling potential. These maps are then overlaid with first year average production rate (IP365) and expected ultimate recovery (EUR) contour maps to further refine the location of new drilling opportunities. Application of the modeling frameworks in the Moxa Arch has helped identify number, drilling sequence and approximate location of infill wells. It has also suggested that a particular development strategy could accelerate recovery as opposed to add volumes in certain parts of the development area.