History of oil in Mexico is related closely to the development of a series of aligned discoveries located in the central part of the Tampico embayment from San Diego de la Mar to San Isidro. This series of aligned discoveries is known as the "old Golden Lane," whose cumulative production to December 1967 is near 1.25 billion bbl of oil. In 1908 the first

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productive well of the Golden Lane, San Diego de la Mar No. 1, was brought in with an estimated daily production of 2,500 bbl of oil. During the following years, production was found in other places by drilling near seepages and following a trend of productive fields about 50 mi long and more than 0.5 mi wide. Within the old Golden Lane is located the famous Cerro Azul No. 4 well, probably the world's largest well, which had an estimated daily production of 260,000 bbl of oil.

What is known as "the new Golden Lane" or as "the southern extension of the Golden Lane" was discovered in 1952 when the Ezequiel Ordonez No. 1 well came in as a producer; afterward, new-field discoveries were made between 1952 and 1962. This trend includes several fields, including the giant Poza Rica field. This southern continuation of the Golden Lane had been inferred geologically but it was not until both gravity and seismic surveys were carried out and interpretative techniques were improved that "the southern extension of the Golden Lane" was identified.

At the same time, an offshore extension of the Golden Lane was suspected, and the offshore seismic surveys carried on led to the discovery of the "marine Golden Lane;" in 1963 offshore well Isla de Lobos No. 1 was completed as a producer. The "Golden Lane," as it now is interpreted, consists of a closed oval-shaped huge "atoll"-type reef about 85 mi long and 40 mi wide, the eastern part extending in the subsurface under the Gulf of Mexico.

In the course of exploitation and the discovery of new fields along its perimeter, the geologic genesis of the "atoll" of the Golden Lane is still the object of controversy; nevertheless, the most accepted theory is that it consists of a biohermal reef that started its growth in Early Cretaceous (late Neocomian) time on a late Kimmeridgian (Late Jurassic) positive element referred to as the "Isla de Tuxpan." At some localities within its inner part, evaporite, calcarenite, and dolomite occur; at others however, rudistid and miliolid limestones occur. Its periphery consists of a prominent belt of structural culminations which are made up indistinctively of rudistid and/or miliolid limestones. The Jardin No. 35 well, drilled in 1930, is the only well that ever penetrated the reef core. ts information, however, is questionable and very scarce. Notwithstanding the depositional environment attributed to rudistids (the principal component of this great reef), its morphology--regarding whether it consists of a bioherm, a biostrome, or a combination of the two--will persist as a subject of conjecture.

Golden Lane fields have produced to December 1967 more than 1.420 billion bbl of oil.

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