Tayvis Dunnahoe
Exploration Editor
Modern exploration goes far to improve drilling success in frontier plays. Recent rounds in the Barents Sea have opened new acreage that will likely be productive within the next decade (OGJ Online, Feb. 1, 2016). In Europe, the question of unconventional resources remains to be answered (OGJ Online, June 6, 2016). While geophysical understanding of the subsurface has gained contrast in today's exploration and development programs, the true nature of undiscovered resources are proven through active drilling.
A wildcat does not hold the same meaning in today's market as it did in the 1930s, and Oil & Gas Journal covered many along the US Gulf Coast during this time. In 1933, Tomball oil field was being opened 35 miles north of Houston. OGJ's Houston bureau documented the event on June 15, 1933, reporting that "There is no definite way of determining without further development just what structural or geological conditions prevail at Tomball."
Yesterday's news
Magnolia Petroleum Co.'s No. 1 Kobs well, spudded in March 1933, opened Tomball field as an oil discovery. OGJ touted the discovery as a "victory for geophysics." The discovery in Tomball produced from the oil and gas-prone Claiborne unit in the Cockfield sand from 5,500 to 5,600 ft.
J. Brian Eby later published, "The Geophysics of the Tomball Oil Field Harris County, Texas," in Geophysics, Vol. 1, No. 1, January 1936, citing, "the geophysical and drilling discovery of the Tomball oil field…marks one of the important mile-posts in the course of Gulf Coast geophysics."
The Tomball discovery was the first geophysical prospect to be admitted to oil field rank before the discovery well was drilled into sand, according to Eby. At the time, OGJ reported, "On wildcat wells, derricks usually are left up for a time but in this case within 5 days after completion of the well nothing was left on the location except the Christmas tree, a separator, and two flow tanks." The derrick and machinery were already drilling a second well.
OGJ described the ensuing land rush as "one of the most sensational wildcat lease and royalty plays on record."
The success at Tomball arrived when refraction seismographs were on the way out, and reflection seismographs were bidding for entrance into the prospecting market. "An oil field discovery on this new type of geophysical prediction was needed to reestablish confidence and insure cooperation on the part of management," Eby said. OGJ reported that the first reflection seismograph was carried out by the Vacuum Oil Co. (then a subsidiary of Magnolia) in September and October 1930.
Within 2 years of its discovery, Tomball field covered 13,000 acres of which 8,000 had proven commercially productive. According to Eby, the field had produced 2.75 million bbl of oil from 200 wells by Nov. 25, 1935.
The Cockfield formation would prove to be a prolific producer throughout the Gulf Coast region extending through South Texas and into Louisiana.
Prospecting today
Historically, the nature of Tomball field's origin was an anomaly. Analogous discoveries and new seismic methods led the way to opening a field that ultimately paid off. Science is ongoing, and exploration technology has advanced from its 1930s roots. Modern imaging provides assurance against most dry holes, and some recent studies have identified newer ways to indicate resources underground (OGJ Online, Dec. 7, 2015).
For many regions of the world, seismic exploration provides structural familiarity and a reasonable method of identifying drilling targets. Operators would rarely, if ever, declare a discovery as an oil field without further development. Most exploration wells drilled today would be considered development wells vs. wildcats.
For any frontier region, headlines are made with a discovery well as opposed to geophysical evidence. What was true for Tomball field in 1933 is true today. The only definitive proof for determining the nature of a play is further development.