Buck, J. Randolph, Member AIME, Northern Natural Gas Co., Omaha, Nebr. Publication Rights Reserved Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and considered for publication in one of the two SPE magazines with the paper. Abstract This paper is directed to the significance of gas reserves and the availability of such reserves to natural gas pipeline companies. Various uses for these computed data within a gas supply department and a transmission company as a whole are suggested. Sources of basic data, the treatment of gas well and casinghead gas, the development of area specialists, together with general procedures followed in the active prosecution of reserves work are indicated. A distinction is made among the terms availability, deliverability, and potential. Each may be considered from the individual well, total field, gathering system, or total company points of view. The problem of gas well stabilization, with particular regard to the ability of wells to maintain certain flow rates under continuous production, is emphasized from the standpoint of the regulatory necessity for a pipeline company to demonstrate an adequate gas supply to meet requirements of the presently proposed or future sales. Very practical problems are involved in the extreme case of low deliverability and high reserves on a per-well basis. The demonstrated difficulty of a pipeline company to maintain a 12-year availability life without creating a condition of oversupply, or bulge gas, is reviewed. General requirements and procedures followed in a certificate application proceeding before the Federal Power Commission are briefly discussed. Meanings for the terms "reserve life index" and "availability life" are included with a review of the effect of an unrealistic availability life control on the industry. Introduction In the state of Texas, petroleum engineers qualify themselves in the field of petroleum and natural gas. Although oil and gas constitute one basic industry, many engineers, particularly the older ones, have devoted the large portion of their time and effort to problems relating to the production of oil. The realignment of a sizeable proportion of the emphasis to problems peculiar to gas has been a development of the past decade wherein the marketability of gas has increased tremendously. The continually expanding sales of gas has been achieved by the pipeline segment of the total oil and gas industry in a complex process involving producers, consumers and certain regulatory bodies. Because of the present magnitude of the gas industry in light of its more recent rapid growth, it is believed not too late to set down a synopsis of how and why gas transmission companies actively engage in and rely upon reserves and availability studies.