ABSTRACT
Tight sand formations, because of their peculiar characteristics, do not conform to the well established behavioral patterns normally associated with conventional natural gas reservoirs. These attributes of tight sands render the conventional reservoir models inadequate when applied to tight sands. It is widely projected that gas resources available in these tight formations, which in the Western United States alone stands at about 5,703 Trillion Cubic Feet, may be the cornerstone of the future energy sufficiency of this country. It is also believed that the major bottleneck in the development of these resources is the lack of understanding of the fluid dynamics in these formations. It is therefore imperative to evolve a good model based on a fundamental understanding of the rather unique physics of flow in this media. A very important unconventional characteristic of tight formations is its dual-porosity nature in the form of micro/macropore structure and the pressure-field, concentration-field driven flow potentials imposed on the system. This physics calls for the use of dual-porosity, multi-mechanistic approach for the description of the transport of natural gas in these formations. Such a model is presented here. Both synthetic and actual field examples are used to illustrate the predictive capability of the model. Results show that the conventional single-mechanistic approach tends to under-predict recovery. They also demonstrate that the dual-mechanistic approach is of the essence.
