Stavropol Region is one of the oldest petroleum provinces on South of Russian Federation. Today, most of its fields are depleted and prospects for the discovery of new large hydrocarbon deposits considered exhausted. However, our studies allow us to talk about the possibility of the existence of previously undiscovered oil reservoirs, clamped in the source rocks associated with North-Stavropol tectonic element. In the middle of the last century, similar deposits have been identified within Prikumsk-Tyulenevskiy (Praskoveyskoe, Achikulakskoye, Ozek-Suat and a number of other fields) and Chernolesskiy (Zhuravskoye, Vorobyevskoye) tectonic elements. However, these findings were largely spontaneous due to lack of approved and unified approach to the petrophysical evaluation of dedicated reservoirs from well logs. At the same time the experience of shale reservoirs studies, as well as the results of its implementation to evaluation of deposits of Zhuravsky-Vorobyevsky petroleum accumulation zone, allows to revise existing well log materials for deep wells of explorational and depleted structures, and to identify promising intervals for further re-exploration and testing. In this work, Paleocene sediments of Blagodarnenskaya explorational structure of the Stavropol Region were studied. Despite the approval of the oil bearing of these deposits within the Prikumsk-Tyulenevskiy tectonic element and the positive signs of hydrocarbon saturation from initial well logs data, its evaluation and testing within Blagodarnenskaya structure associated with North-Stavropol tectonic element, were not conducted. However, the results of well logs analysis performed by us with the use of interpretation technique approved on reservoirs of Zhuravsky-Vorobyevsky petroleum accumulation zone, as well as the core tests indicate the presence of oil-saturated reservoirs in the Paleocene sediments of Blagodarnenskaya structure.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
The article demonstrates the technology of testing reservoir layers represented by fractured clay-carbonate rocks in the Eastern Ciscaucasia. Practice shows that if the saturation of permeable rocks is uniform, the reliability of the tests can be ensured if the tested interval does not exceed 25 m. The probability of obtaining an inflow during tests significantly decreases with the increase in the amount of repression of the washing liquid and the duration of its impact on the reservoir. This is caused by clogging of the near-well zone of the reservoir, which results in the hydrodynamic connection of the reservoir with the well deteriorates. Test results are the most reliable if they are performed no later than 3-5 days after opening the reservoir, however, even in this case, the reservoir may be contaminated. For high-quality testing of reservoir layers represented by fractured clay-carbonate rocks, the following processes are required: to make an individual selection of the depression on the formation, to have a priori accurate information about the strength characteristics of the well walls.
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