Petroleum Exploration in North Texas and the Discovery of Floodable Reservoirs
Authors: Gee David E. 
Published: December 2007

American Institute of Mining, Metallurgical and Petroleum Engineers, Inc.

Introduction
Approximately 2 billion bbl of oil have been produced in North Texas [District 9] during a period of exploitation exceeding 60 years. Cumulative production from the district is about 7 percent of the total for the State of Texas, and 2 percent of the national total.
The largest oil fields of North Texas were discovered prior to 1940, and most of them are now, or have been, the site of major secondary recovery projects. The cycle of discovery, development, and secondary recovery has been repeated for many of the smaller and intermediate size pools. Over 250,000 acres are now under flood or pressure maintenance within the district.
Methods of increasing the production of wells above their natural rate began in the area about 1914, when it was discovered that the daily volume of casinghead gas and oil decidedly rose as shallow wells were pumped with a vacuum-on the casing. Around 1928, the Railroad Commission ceased to issue vacuum permits, and repressuring the producing zone with permits, and repressuring the producing zone with residual casinghead gas and produced gas from outside sources was substituted.
Water flooding of sandstone reservoirs began as early as the 1930's with a mixture of success and failure. A great increase in this kind of activity began around 1949 and resulted in rapid utilization of the supply of floodable reservoirs discovered in the past through the installation of over 1,500 individual secondary projects within the district. projects within the district. This activity was accompanied by an abrupt decrease in exploratory drilling beginning in 1957. The number of significant new fields discovered greatly diminished, and the incidence of potentially floodable new reservoirs dropped to an annual rate approximately one-sixth of the 1956 total.
These conditions become increasingly critical to the future of the producing industry of the area as the district's annual production declines. production declines.

RECENT PRODUCTION HISTORY
Railroad Commission District 9 reached a peak in annual production in 1956 with an peak in annual production in 1956 with an output of over 77 million bbl. Proration curtailed subsequent yearly totals as illustrated by Fig. n The truncating effect of a decreasing number of annual producing days, or equivalent in percents extends through 1964.
During the last 3 years, progressive increase in the number of producing days has not resulted in a rise in annual production. The indicated deficit is greatest for 1967 when the district's annual production decreased approximately 1.7 percent to a total of 67.2 million bbl despite an increase of 25 producing days over 1966 [Fig. 1]. producing days over 1966 [Fig. 1].Much of the district's production is classified as "County Regular" and not subject to appreciable monthly variation in volume unless through normal decline. Consequently, these data show that the annual contribution of the area's prorated fields and active water floods.. formerly a buoyant factor, is no longer sufficient to meet current market or emergency demand nor to reverse natural depletion of the district's reserves.