Conditions for generation, accumulation, and preservation of Oil and gas in permian strata, northwestern anabar-khatanga Oil and gas region
A.I. Larichev, O.I. Bostrikov, A.N. Khabarov
A.P. Karpinsky Russian Geological Research Institute, St. Petersburg, Russia
Keywords: Petroleum generation potential of Permian sediments, catagenesis, late Permian-Early Triassic trap magmatism, petroleum potential, Anabar-Khatanga saddle
Abstract
Integrated seismic, drilling, and other exploration works in the southeastern Anabar-Khatanga petroleum province since the early 1930s led to discoveries of small oil and gas occurrences and one large filed of Central Olgino. However, the petroleum potential of the northwestern part of the province remains poorly investigated and evaluated. The reservoir potential appraisal is attempted in this study using all available seismic, geological, and geochemical data, including evidence from four new wells drilled in the Sopochnoe uplift and the Zhuravliny swell. The obtained data provide constraints on the extent of oil and gas generation, accumulation, and losses from degraded traps in Permian strata that have the highest potential as source rocks. The source rocks of the Upper Kozhevnikovo, Lower Kozhevnikovo, and Tustakh formations have been characterized in terms of thickness, contents of organic carbon and chloroform bitumen, maturity (catagenesis) of organic matter, and density of oil migration and gas generation. The maximum possible estimates of oil and gas resources that can potentially accumulate in structural traps, without migration losses, are obtained for each of the three reservoir formations by basin modeling. Judging by geological and geochemical criteria, the Upper Kozhevnikovo Formation can preserve only a minor portion of initially accumulated hydrocarbons, while the oil and gas accumulations, as well as the petroleum generation potential of organic matter in the Lower Kozhevnikovo and Tustakh formations, were destroyed by late Permian-Early Triassic trap magmatism and Mesozoic-Cenozoic tectonic activity.
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