The Guijarral field was discovered relatively late (1948) because of the depth and relative inaccessibility of the oil-producing formations. While the enormous Coalinga field is but a few miles away, in a similar anticlinal structure, it is richly productive at under below ground surface, and hence was easier to exploit. Drillers attempted to find oil at the Guijarral Hills in the 1920s, but the maximum depth of their boreholes was only a little over , and while these boreholes were in good locations had they been drilled sufficiently deep, they were abandoned. The discovery well was put in by Barnsdall Oil Company in 1948 to a depth of and flowed over ; by the end of 1948, seven more wells had been drilled to follow on this success.