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The AAPG/Datapages Combined Publications Database

AAPG Special Volumes


Pub. Id: A004 (1935)

First Page: 1035

Last Page: 1052

Book Title: SP 7: Geology of Natural Gas

Article/Chapter: Estimation of Natural Gas Reserves

Subject Group: Field Studies

Spec. Pub. Type: Special Volume

Pub. Year: 1935

Author(s): P. McDonald Biddison (2)

Editor(s): H. A. Ley


This paper presents the mathematical premises on which are based the estimation of natural gas reserves. The data used in the estimation of natural gas reserves are the records of (1) initial and current reservoir pressures, (2) volume of gas withdrawn, (3) the physical properties of gases, and (4) the physical properties and areal extent of the gas-bearing reservoir. Equations are given which include corrections for the Previous HitdeviationTop of gases from Boyle's law, and the determination of bottom-hole pressures from well-head pressures in closed wells. Three cases common to the determination of bottom-hole pressures are described. Six cases concerned with the estimation of original and remaining natural gas reserves in a reservoir are set forth.

Not many years past, natural gas wells were valued according to their ability to produce gas--a sum of dollars for each million cubic feet of daily open-flow capacity. Because many in the industry, even as late as 1919, held that the supply of natural gas in the United States had reached its climacteric and would soon be exhausted, little interest was taken in the determination of natural gas reserves within a reservoir, but the determination of reserves became necessary with the enactment of the Federal Tax laws of 1917. The discovery of large gas supplies, mostly west of Mississippi River and far removed from adequate markets, increased the need for precise reserve estimates. To utilize these supplies in distant markets, large capital expenditures were necessary. To insure the safet of these expenditures, as far as adequacy of supply was concerned, well grounded estimates of the supply (reserves) were prerequisite.

The amount of a natural gas reserve determined by competent engineers is based on commonly accepted physical laws. It is a reliable determination, often for conservative reasons less than the amount finally realized. No natural gas system, built around supplies determined by competent engineers as adequate, has ever encountered financial difficulties because the reserves were found to be inadequate.

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