Oil and gas leakage mechanisms at offshore fields of the Caspian sea

This article presents a comprehensive analysis of oil and gas leakage mechanisms at offshore fields in the Caspian Sea, considering engineering, geological, and physicochemical factors affecting the integrity of wellbore and subsea infrastructure. Particular attention is paid to the northern Caspian, where shallow waters, high salinity, seasonal ice loads, and the presence of aggressive reservoir fluids significantly increase the risk of failure in casing strings, cement sheaths, and pipelines. Both macro-scale causes of leakage — including tectonic and geomechanical faults, seismic activity, and degradation of cement barriers — and micro-scale processes are examined. These include reduced interfacial tension, capillary effects, phase transitions, and chemical interactions with construction materials. Special focus is placed on phenomena accompanying hidden leakages in annular spaces: foaming during decompression, capillary seepage of hydrocarbons, and upward migration of oil. Mechanisms of vertical leak channel formation in poorly cemented zones and the long-term degradation of cement under the influence of CO2 and H2S are described. The paper analyzes typical engineering failures contributing to leakage, such as corrosion, erosion, cementing defects, blowout preventer (BOP) malfunctions, and aging of materials. Modern technologies for early leakage detection and prevention are discussed, including SCADA systems, remotely operated vehicles (ROVs), satellite monitoring, and geochemical analysis of water and seabed samples. A comparative review of accidents in the Gulf of Mexico and the North Sea identifies technical and organizational vulnerabilities relevant to the Caspian region. The study emphasizes the need to adapt international design, cementing, and safety standards to the specific environmental and operational conditions of the Caspian shelf.

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