Stocks of naturally formed hydrocarbon gases, which are usually associated with petroleum fields or gas hydrate formations. Distributions are geologic maps, models, and other observations that indicate locations and volumes of underground stocks. Assessments evaluate locations, methods, and profitability of gas extraction and transportation; environmental impacts; and (or) other interactions with other uses. Predictions are the results of models or projections of future gas reserves based on projected extraction, or they are predicted changes in profitability and risk due to economic, regulatory, technological, and environmental changes.