Oil and gas production in Turkmenistan has traditionally been linked to the Middle Pliocene sedimentary complex, known as the red-bed sequence. In recent years, however, Mesozoic deposits have grown increasingly significant, seen as a promising direction for expanding the country's resource base.
This is based primarily on oil inflows recorded in Upper Cretaceous deposits of the Kura Depression and the North Absheron fold zone, as well as in Cretaceous and Jurassic deposits at the Oymasha field in Kazakhstan. In addition, deep drilling at a number of sites in South-Western Turkmenistan has revealed significant oil and gas indications within Mesozoic deposits.
On the onshore part of South-Western Turkmenistan, more than 70 percent of initial total oil reserves have been explored in Pliocene deposits, while Mesozoic deposits currently account for about 60 percent of predicted hydrocarbon reserves. These figures point to the need to expand geological exploration in the near term — a significant reserve for increasing the country's resource base.
According to geophysical surveys, the thickness of Mesozoic deposits within the West Turkmen Depression is at least 10-12 kilometers, indicating a high rate of sediment accumulation. A direct link has been established between the distribution of deposit thickness and the location of oil-bearing facies: oil-bearing areas of the basin coincide with zones of thick sediment accumulation and areas of prolonged, rapid crustal subsidence. Rapid subsidence of deposits raises pressure and temperature — one of the key conditions for oil formation.
This depression remains Turkmenistan's largest and only oil and gas producing region, hosting numerous oil and gas fields in Cenozoic deposits. Scientists believe hydrocarbons formed mainly in the deeper-lying Mesozoic deposits, migrating to upper horizons through faults, fractures and mud volcano channels.
Mesozoic deposits accumulated amid prolonged, steady basin subsidence under reducing or weakly reducing geochemical conditions, as indicated by the lithofacies characteristics of the section and the substantial thickness of the deposits. Similar geostructural and facies conditions have been noted in Azerbaijan, Kazakhstan, Iran and other nearby oil and gas regions, where major oil fields are associated with internal geosynclinal and foothill depressions.
Further evidence of the promise of Mesozoic deposits comes from tests at well No. 23 at the Garadepe field, which showed signs of oil and gas presence. Thick reservoir layers have also been noted in Lower Cretaceous and Jurassic deposits, overlain by clay rock sequences of Upper Cretaceous, Paleogene and Miocene deposits. In terms of lithological composition and reservoir properties, carbonate rocks predominate in Neocomian and Upper Jurassic deposits, allowing them to be classified as a single Neocomian-Upper Jurassic lithologic-stratigraphic complex promising for hydrocarbon exploration.
