Much recent attention has been recently given to depletion of U.S. natural gas reserves, particularly since many forecasts predict a 30 TCF annual gas market. A comprehensive look at the way initial production, decline rates, and reserves have changed over the last 30 years in Texas, the source of 1/3 of the country’s natural gas, leads to concern about whether current drilling activity will be able to maintain the current supply, much less increase gas production 1.

The decline rates in new Texas gas wells have changed from about 20% in the first year for wells drilled in the 1970’s and 1980’s, to more than 55% for wells drilled in 1998 and 1999. At the same time, the contribution to the state’s supply from new wells has sharply increased from 8% of the state’s supply to more than 15%. Although the initial production rates from an average well have actually improved from a low of 15 MMCF per month in the early 1980’s, to 44 MMCF per month in 1999 due to improved completion technology and horizontal drilling, the combined effects of fewer completions and high decline rates suggests that a decrease in Texas’ production capacity may occur in the near future. Drilling above the current activity will be necessary to sustain the state’s gas production.

Normalized rate vs. time curves were developed for each year since 1970 to obtain initial rates and decline profiles. The curves were extrapolated to an estimated ultimate recovery, changing from 6 BCF per well in the early 1970’s to 1 BCF per well in the late 1990’s.

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