Comprehensive assessment of the mineral resource potential of oil and gas basins, taking into account the distribution of gas hydrates and the prospects for developing deep-water fields

Abstract

In the context of the transformation of the global energy structure associated with the depletion of available hydrocarbon reserves in traditional provinces, a comprehensive assessment of the mineral resource potential of the World Ocean's oil and gas basins is becoming particularly important through the integration of regional geological and geophysical data, basin modeling, petrophysical analysis, geomechanical calculations and engineering and construction approaches to the development of deep-sea facilities where gas hydrates form an essential component of the resource base is in the form of crystalline water compounds with low molecular weight gases that are stable under certain thermobaric conditions and contain volumes of methane that are ten times higher than the reserves of free gas according to various estimates. The distribution of forecast resources demonstrates a pronounced differentiation depending on the tectonic regime, sedimentation history and thermobaric gradient: basins of passive margins are characterized by high specific indicators of traditional oil and gas content up to 45-60 thousand tons of conventional fuel per square kilometer, while zones of active margins and back-arc deflections are characterized by an increased potential of the gas hydrate component due to intensive fluid discharge, with accumulation localization mainly on on the continental slope in the sea depth range of 500-2500 meters, where the position of the base of the hydrate stability zone is recorded by seismic reflectors, and the thickness of the hydrate-bearing intervals varies from 50-80 to 400-600 meters in high-latitude regions. The geomechanical properties of hydrated sediments, including the Young's modulus ranging from 0,84 to 7,42 GPa, the Poisson's ratio, the compressive strength, and the velocities of elastic waves, are highly dependent on the lithological composition and degree of saturation, which determines the risks of soil liquefaction, landslide processes, and loss of load-bearing capacity during technogenic dissociation. This requires the use of differentiated computational models for interaction with bottom structures. A comparison of the technical and economic parameters of various architectural solutions of the marine infrastructure – semi-submersible platforms, FPSO, SPAR, TLP and fully underwater complexes – at depths over 1,500 meters reveals an increase in capital expenditures from 174,8 to 247,9 million dollars per well and operating costs with varying specific productivity and service life, while gas extraction technologies from hydrates, including depression, thermal, inhibitory, carbon dioxide substitution, and combined methods, show differences in energy efficiency of up to 73,8%, unit costs, extraction coefficients of up to 67,3%, and risk levels of uncontrolled destabilization. An integral quantitative assessment for 28 basins, performed using the probabilistic method with the calculation of P10-P90 based on the lognormal distribution of parameters, shows the total energy equivalent of the resource base of 2,873×10¹⁴ tons of conventional fuel, where the share of the gas hydrate component exceeds 47%, while the realized part of the potential at the modern technological level is limited to 12-15%, which emphasizes the need for improvement methodological approaches, adaptation of design solutions to the geotechnical features of hydrate-bearing strata, elimination of gaps in the regulatory framework and development of specialized technical requirements to ensure sustainable development of deep-water provinces in the context of the growing role of unconventional sources of hydrocarbons.