Abstract
<jats:title>Abstract</jats:title> <jats:p>I was drawn to investigate early oil and gas exploration wells drilled in San Diego as part of a study on the Late Paleocene to Early Eocene Mount Soledad Conglomerate, a lightly studied and poorly described Formation. Due to the paucity of surface exposures, I hoped that subsurface records from exploration wells in the California Department of Conservation's on-line database could bring to light structural and stratigraphic details that surface exposures along could not provide. To my surprise there are records of 52 oil and gas exploratory wells drilled in San Diego County from 1910 to 1963. Although the records are sometimes incomplete or ambiguous there was enough geologic information to allow new insight into some important details of the Mount Soledad Conglomerate. The locations of these wells and index is shown in Plates 1 and 2.</jats:p> <jats:p>While several stories reference the so-called "San Diego Oil Boom"—often focusing on Mayor Wilde's 1920's infamous investment scam—(Mike Bryant 2009- https://www.sohosandiego.org/reflections/2009-1/preserving.htm) these accounts rarely capture the full scope of events or highlight the valuable geological information revealed by these early boreholes. The data from these wells offer deeper insights into the region's geology, including parts of the geologic section not exposed in outcrops, especially between rocks deposited in the Paleocene and Early Eocene. This work presented here not only documents the geologic value of subsurface data from old oil and gas wells in San Diego but also integrates the human experiences of that era.</jats:p> <jats:p>Understanding how to use the information from these wells requires an appreciation for early 20th-century drilling life and the terminology used by wellsite geologists and engineers, much of which is now largely forgotten. As an example "shell" refers to a limestone bed or interval while "shells" records the presence of fossil shell debris. Another common usage includes gumbo (for bentonitic shales) and "adobe" or "dobe" for laterite.</jats:p> <jats:p>Each of the 52 oil and gas exploration wells that were drilled have a back story regarding the visionaries, entrepreneurs and yes, even the con men who were the force behind getting these wells drilled. Typically, most of these wildcatters used the familiar term OPM "Other People's Money" when it came to the task of financing their ventures. What shouldn't be lost about the San Diego oil boom in the first part of the 20th century is that it came about because of the huge success and unimaginable wealth generated by oil discoveries to the North in Los Angeles. The refrain often was "if there, why not in San Diego". The fact that San Diego had a number of geologic structures outwardly identical to oil fields in Los Angles made the argument that much more compelling. Reading through the records it also becomes apparent that the efforts in San Diego were also twinged with a bit of competitiveness with the city to the North. A competition that perhaps started in the early 20th century but still remains today.</jats:p>