RESERVOIR ENGINEERING SIMULATIONS, PRIORITIZATION OF LABORATORY EXPERIMENTS, AND DESIGN OF FIELD RESEARCH FOR COALBED SEQUESTRATION

The world’s first carbon dioxide-enhanced coalbed methane pilot project in the San Juan Basin has indicated that sequestration of carbon dioxide in unmineable coal seams may be both technically and economically feasible. Thus, coalbed sequestration is a promising candidate for early commercialization; both reservoir simulations and identification of the most-needed laboratory and field research measurements are needed now.

In the implementation of new technologies for underground injection of fluids, field-scale reservoir simulators traditionally are used in the design of pilot and demonstration projects. However, they also may be used to perform sensitivity studies and to help identify those chemical, geophysical, flow, and other measurements that are most-needed for optimization of the new technology.

We have performed parametric studies of the effects of various (uncontrollable) coal-seam properties and (controllable) engineering parameters on carbon dioxide sequestration. These properties include porosity, permeability, cleat spacing, pod size, sorption isotherm, sorption rate, and reservoir pressure, water saturation, and gas composition. Engineering parameters explored include various combinations of vertical and horizontal wells, and well lengths and orientations.

These results may contribute not only to site selection and design of operating conditions, but to choice and interpretation of both field measurements (such as well-test measurements of permeability) and laboratory measurements (such as the effects of confining pressure on sorption isotherms, flow through cleats, and coal swelling). The results may also help to guide the development of advanced simulators that include such features as explicit cleats (instead of dual porosity) or advanced gridding methods.