DECIDING on CAPACITY CALCULATION METHODOLOGY FOR THE TEXAS SUBMERGED LANDS CAPACITY ASSESSMENT

Currently the Bureau of Economic Geology’s Gulf Coast Carbon Center is undertaking a study of the Texas state waters in the Gulf of Mexico in order to assess the potential for permanent carbon dioxide storage in the subsurface in order to help mitigate green house gas emissions. This region was selected due to its proximity to a large volume of industrial sources of carbon dioxide, extensive geological knowledge due to decades of oil and gas exploration and the expansive size of the area extending 10 miles offshore and approximately 200 miles along the coast.

One objective of the study is to estimate the capacity of Miocene reservoirs on a regional scale. Before this can be accomplished a comprehensive data collection must be finalized. Based on the data compiled, a capacity calculation methodology will be selected. Currently there are a variety of methods in the literature which can be utilized, varying greatly in their approach, required data, and resulting accuracy of the calculation. For this, a separate assessment was conducted. Numerous papers presenting specific methodology approaches were reviewed and a summary and comparison was prepared; when the majority of the data collection is completed, it will be possible to select the most applicable method in order to correctly utilize the available data for the capacity assessment.

For the summary and comparison, seventeen papers were evaluated. Based on these papers, capacity methodology was divided into 4 different categories: volumetric based estimation, production based estimation, pressure differential/compressibility method, and a coefficient concept method. Many papers exhibited characteristics of two or three methodologies; a Venn-style diagram was prepared in order to visualize where the emphasis in calculation methodology lies and identify the overlap. Based on these papers, the prominence of the volumetric based estimation method becomes apparent.

While the data collection is not yet complete, five papers were selected for further research due to their applicability to the initial data. The next few months will see the finalization of the data collection and the selection of a best methodology for the Texas Submerged Lands Capacity Assessment.