There is a reason we studied historical geology as undergraduates. That class laid a firm foundation for our geoscience careers by stressing how important it is to look far back in time, before we move forward in any modern petroleum-related project, especially with an existing field. This is true, not just for deep time, but also for exploration and development projects on legacy salt domes which were explored and developed in the early 1900s on the Gulf Coastal Plain of Texas and Louisiana.
Spindletop
The impact that the huge initial oil production at Spindletop, Texas, had on oil exploration, beginning in 1901, cannot be ignored. There was very little scientific understanding of the subsurface at the time of Spindletop’s early development. Captain A. F. Lucas, who was hired originally by Pattillo Higgins and later drilled the giant discovery well, had an inkling that a salt dome might be the cause of the surface “bump,” based on his earlier experience in Louisiana.
Later drilling across the Gulf Coastal Plain focused on similar surface expressions that indicated the potential presence of hydrocarbons and targeted anticipated “cap rock” reservoirs as seen at Spindletop. Any identified oil or gas seep and/or surface “bump” was a target for the drillers, but the lack of any scientific basis to support the selection of a drilling location led to an extremely high proportion of economically marginal producers or dry holes. For example, at Barbers Hill between 1901 and 1924 (a prospect identified and successfully tested by Pattillo Higgins), 73 of the 119 wells drilled were junked or dry. The rest were non-commercial. Other illustrations of delayed exploration success, due to trying to emulate Spindletop, are found as well in the 1989 book, “Pattillo Higgins and the Search for Texas Oil,” by Robert W. McDaniel and Henry C. Dethloff.
During the period from 1901 to 1917, shallow drilling activity at Kiser Hill, located about 40 miles south-southwest of Houston (later renamed West Columbia field) was a lengthy process. It often took a year or more to drill to a few hundred or a thousand feet. Wells were often plagued by “heaving” shales and other technical problems, resulting in many junked and abandoned wells despite their oil shows or minor oil production. Many of these technical problems were not solved until the 1930s. Most of these “show wells” now appear as dry holes on more recent maps, complicating our recognition of the successes of the early drilling.
The Pioneers
So why are historical data, when combined with the more recent development of concepts and technology, so important? Our industry has always been led by a few pioneers, like the visionary Pattillo Higgins and others. Higgins is credited with involvement in 21 oil field discoveries between 1892 and 1908 on the Gulf Coast of Texas and Louisiana, and dozens of other discoveries later in his career. Many of these discoveries became major oil fields such as Barbers Hill, Sour Lake, Saratoga, Pierce Junction, North Dayton, Humble, Goose Creek and, of course, Spindletop itself. These pioneers were followed by a host of other investors, trying to gain an advantage or acquire land positions near the early discoveries. They used the pioneering theories of Higgins concerning the oil habitats around these surface “bumps” on the Gulf Coast of Texas.
In these early years of exploration on the Gulf Coastal Plain, there were few controls on well spacing, regardless of lease size, which could range from a few large acreage blocks to tracts less than a few acres. Even small, five-acre blocks might have had excessive drilling of five or ten wells on them in a matter of a year or two after a nearby discovery. In some fields, the drilling density was so tight the derricks nearly touched each other. The price of oil fluctuated radically depending on the magnitude of production from the giant discoveries which did occur.
Published Historical Data
While there were only a few detailed geological field studies of salt domes published between 1901 and 1942, weekly and monthly “scouting reports” covered drilling activities in the United States, Canada, Mexico, Colombia and Venezuela. Short, summary articles listed the results of drilling by well and operator in some fields, including initial production rates, depth of production and often rates of production, a year or so into the production history.
Initial production rates in the thousands to many tens of thousands of barrels per day from flowing wells inevitably led to very short production histories, often leading to very low total recovery factors, despite the excellent reservoir characteristics. One can assume that reservoir damage was extensive during this early period because of these excessive, uncontrolled production rates combined with the unconsolidated nature of the sands.
So, what can be learned from deep dives into the early drilling data of Gulf Coast salt domes?
Publicly available scouting reports (National Petroleum News, for example) from the early 20th century often identify the correct location and status for wells that have become mislocated or misclassified over time. The reports also document the drilling results of wells which encountered hydrocarbons, often listing initial production rates of successful completions, the longevity of production and related information.
These and other reports reveal the contemporary drilling and completion practices, the economic impact of rapidly growing oil production at a time of limited end uses for petroleum (lubrication, illumination, asphalt and coke), the impact of major weather events on infield derricks and the presence of heaving shales, which are common at West Columbia and other fields. The National Petroleum News, the Oil Trade Journal, the Oil Weekly, the Oil and Gas Journal (of course) and other sources of information found online can be utilized to reveal new drilling opportunities in these old fields.
Other composited information may reveal bypassed pay zones, or low volume producers, deemed “non-commercial” in those early days of giant flowing wells. These “show wells” are often designated as dry holes on more recent field maps. An example is the Producers’ Hogg well which was reported to have had gas and/or oil indications, but oil was not seen on a wash pipe pulled from the well. This well is now shown as a dry hole on recent maps, without noting that there were hydrocarbon shows.
Public Files
A second genre of information, useful for the current evaluation of Texas Gulf Coast salt domes, such as West Columbia, is found in the files of the Texas Railroad Commission, the Texas Bureau of Economic Geology and the Briscoe Center for American History, all of which are in Austin, Texas. These data for West Columbia field provided a few lease-cumulative production numbers for 13 wells over their early production history.
Also indicated there is the significant hydrocarbon production recovered from the Heterostegina reefal limestone (Het Reef) at Nash Dome and other Gulf Coast salt domes. This limestone zone could be a development target at West Columbia field, where the reef material is especially well developed, as well as at 10 other legacy salt dome fields where the Het Reef is present. The Het Reef has often been used as a water disposal reservoir, which must be considered if the Het is an oil target.
By comparing older field maps found in the above files with more current maps, underdeveloped areas for certain reservoirs can be recognized. Cross-sections from West Columbia field filed with the State of Texas show the gas/oil and oil/water contacts by reservoir as determined by the operator. These can be extremely useful in evaluating reservoirs which appear to be underdeveloped on more recent maps. Drillers’ logs found in the BEG files revealed the results of whole cores recovered in the 1920s, sections of which were described as containing oil sand.
Some of these wells with reported oil shows are now identified on the most recent West Columbia field maps as dry holes, with no indication of the hydrocarbon shows. By studying early maps found in these files, we found that symbols used in the past for an abandoned well location were later taken to mean a drilling well. This awareness can now open these areas for further prospecting, as they have not been condemned by those never-drilled wells.
Another West Columbia field file, submitted by an operator, discussed the nature of a group of thinly bedded, but highly productive reservoir sands, and stated that some were continuous while others were discontinuous, based on their reservoir drive mechanisms. Many of these reservoirs seem to be under-evaluated over a large area of the West Columbia field, and around other fields as well, for example, Anse La Butte in Louisiana.
Old Scientific Publications
A third source of useful information is the early scientific publications such as the AAPG Bulletins and Special Publications, Transactions of the GCAGS, US Geological Survey Bulletins and Professional Papers, and other sources. For example, one of the significant remaining questions at West Columbia field and others in the Texas Gulf Coast basin is the potential source rock for the Miocene and Oligocene reservoired oils. Literature of the last 20-30 years has focused on the Paleocene Wilcox formation as a possible source. However, an in-depth paper, “West Columbia salt dome and oil field, Brazoria County, Texas, by D.P. Carlton and published in the 1929 AAPG Special Publication “Structure of typical American oil Fields,” shows that the Eocene lower Jackson shale from 4,405 feet to 4,593 feet in a Humble well, exhibits a “dark brown calcareous unctious clay in places”; “unctious” meaning oily.
A 1927 article in The Oil Weekly reads “on the west side (of West Columbia) is a shale oil of around 28.5 API which differs from the regular heavy grade predominating the field. The shale oil is coming from around 3300 feet.” The shallow depth of this shale could confirm that the unnamed shale is likely the Eocene lower Jackson shale. R. Sassen, in his 1994 “Oligocene-Holocene hydrocarbon migration and salt-dome carbonates, northern Gulf of Mexico,” published in Marine Geology, suggested an Eocene source for Damon Mound oils, located 10 miles northwest of West Columbia field. Thus, information found in early twentieth-century literature supports the need to perform additional modern geochemical analyses, some of which are reported in what follows, to confirm the petroleum source unit for other subsurface structures in this portion of the Gulf Coast basin.
Data Integration
So how does the integration of all available, older data with more modern material help define new opportunities for the drilling of commercial targets in existing fields?
First, we now have a greater understanding of the unusual hydrocarbon distribution associated with the current salt piercement structure at West Columbia as well as other salt structures, such as Anse La Butte.
Second, we have learned that the presence of the Het Reef limestone, on or near a salt piercement, defines an earlier, pre-piercement structure which is much larger in area than the more recent piercement structure itself. This earlier structure often has a major angular unconformity underlying the more recent reef buildup which led to the redistribution of the eroded sandy material into local reservoirs that do not exist away from that early uplifted area. These thin reservoirs at West Columbia field exhibit high initial oil flow rates and cumulative production of greater than 150,000 barrels of oil per well over the first fifteen years of production history, as seen in reports filed with the Texas Railroad Commission.
Third, recent geochemical analyses of samples from six currently producing wells at West Columbia, indicate that the oils in Miocene and Oligocene reservoirs were identically sourced, implying a single, major generation-to-entrapment event. Combined with the oily (unctious) nature of the Eocene lower Jackson shale and its entry time into the oil window, these data suggest that it might be the source of the entrapped oil at West Columbia field. The lower Jackson shale may still be in the oil window in the Arco No. 1 Crews well (total depth 21,957 feet) located a few miles west of West Columbia field.
Lessons Learned
By extension, many of the lessons learned from our in-depth study of the West Columbia field area can be applied to other salt domes of the Gulf Coast. There are at least 10 other Texas Gulf Coast salt domes with identified Het Reef material present that have possible major sub-Het Reef unconformities and the redistributed sands resulting from that erosional episode. The Louisiana Gulf Coast also has salt domes, such as Anse La Butte, that have Het Reef material present and possibly have a similar structural history of episodic growth, and therefore could have undiscovered or under-evaluated development targets.
We should all be thankful to Pattillo Higgins, a self-taught geologist, for his curiosity and persistence in the face of nearly universal condemnation by the “experts” of the time for his radical ideas concerning the presence of commercial hydrocarbons under the Gulf Coastal plain. His recognition of the surface indications of the probable presence of subsurface hydrocarbons, a concept that he learned from a trip to Pennsylvania and from his own reading, led directly to the development of the Gulf Coast oil industry. Higgins died in 1955.
While the “present is the key to the past” is true, so is the past the key to present in identifying development opportunities in the Gulf Coastal Plain. The advancement of new ideas such as the ramifications of episodic uplift of salt domes and new technologies like the widespread use of 3-D seismic, has created many new opportunities. Utilizing old data and old publications should be combined with new ideas and new technologies in the exploration and development of major producing provinces.