The long-term development of hydrocarbon reservoirs (HCR) in the geological environment, complex deformation processes occur. Gravity monitoring is carried out to evaluate the possible geodynamic risk and negative consequences from HCR. As a result, the interrelationships of the continuously changing field-geological situation (changes in production volumes, changes in reservoir pressure, processes of fluid injection into productive formations) are investigated. The main tool for solving the gravity inversion when determining areas of increased industrial hazard is the solution of the gravity direct problem. In these studies, proceeding from a given initial approximation of the environment, the problem is realized through successive approximations. To assess such distributions, the authors of the article recommend using the simulated annealing technique within the framework of stochastic optimization. It is aimed at fitting the optimal parameters of the medium provided that a minimal residual of the gravity field values occurs. The approach is implemented using three simple mathematical models of the geological medium such as horizontal prism, homogeneous sphere, and vertical ledge. This technique allows fitting the media values simultaneously by a pair of its parameters. The operation of the algorithm is described and the simulation results are provided. The results showed acceptable accuracy of the algorithm for solving the direct gravity problem by the proposed method. The simulated annealing technique made it possible to increase the reliability of the HCR model while reduce the time for the analysis of the gravity field.

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We analyze the basic techniques for the investigation of the deep structure of the mantle and the shortcomings of the models of mantle structures derived from them. Thus, we reveal that there is no analysis of the velocity field by means of analytical transformants. Therefore, we developed and tested a new approach to define the mantle boundaries based on the calculations of the sequence of P-waves velocity derivatives. As a result, we obtain some new set of velocity gradient distributions for the principal tectonic structures of the Ukrainian Shield along the composite profile. The boundaries of the mantle discontinuities according to the velocity gradient we define in a special manner to eliminate the false anomalies and the fluctuations of the velocity curves that occur due to the conversion of the hodograph into the mean velocities. The smoothing of the velocity curve we perform with a previously defined wavelength step being equal to 50 km. We treat the calculated velocity gradient anomalies as the useful signal response above the appropriate sections, which have different velocity accelerations levels inside the upper mantle. We assume that the mantle anomalies have the same physical background (density/viscosity distributions, temperature gradients etc.) within each range with the equal acceleration value. However, the singular points determined by the inflections of the gradient curve could be the possible boundaries of additional inhomogeneities within the mantle. We calculate both the 1st and the 2nd derivatives for the velocity curves obtained. The excesses 2.5-D model of the 1-th and 2-th gradient curves (the acceleration of the gradvp itself) determine the position of the max / min anomalies of gradvp at the consolidated seismic profile within the Ukrainian Shield. Finally, we analyze in detail the distribution of velocity gradients of P-waves within the upper mantle in the depth range of 50–750 km. It results in the identification of a series of additional gradient velocity boundaries within three principal structural horizons of the upper mantle (under ~ 200–300 km, ~ 410–500 km, and ~ 600–650 km respectively).

Узагальнено і доповнено матеріали геологічної будови і геофізичної вивченості Іллінецької кільцевої структури на південно-західному схилі Українського щита. Здійснено моделювання будови центральної частини кратера за даними спільного аналізу 2D і 3D моделей поля сили тяжіння та його трансформант – модулів горизонтального градієнта сили тяжіння. У результаті моделювання виявлено періодичний хвиле подібний характер деструкції вмісних порід у центрі структури. Фронт деструк ції окреслено за даними аналітичного продовження вверх на 1 км спостереженого поля сили тяжіння над центром кратера. Ці результати можна трактувати на користь додаткового підтвердження імпактної гіпотези щодо генезису Іллінецької структури. З позицій хвильового процесу оцінено наближені параметри імпактної події – масу метеороїда, глибину проникнення і енергію вибуху. Ці оцінки на понад 5 % відхиляються від відомих з літератури даних. Оцінка 2, 57 · 10 25 ерг вкладається в діапазон енергії для імпактних подій середнього масштабу.