The influence of adsorbed polar components on the change in the wettability of terrigenous and carbonate reservoirs of oil and gas condensate fields was studied. The regularities of hydrophobization of the internal space of the reservoir in two cases are established: the effect of only the asphaltene component and the effect of the asphaltene component together with the oil-resinous components. The role of associations of polar components in the change of wettability is shown.

The physicochemical mechanism of the development of microstructural wettability in oil and gas reservoirs is experimentally justified. It is shown that this mechanism is associated with the formation of mosaic hydrophobic areas on the interstitial surface of the reservoir rocks. It was revealed that hydrophobic areas are formed due to the competition of adsorption processes between aromatic and aliphatic structures. For example, the relationships between the hydrophobization index (the ratio of the hydrophobic interstitial surface to the total pore surface) and adsorbed oil composition were identified by studying core samples of carbonate rocks from the Karachaganak oil and gas condensate field (Kazakhstan) and the Astrakhan gas condensate field (southwestern part of the pre-Caspian Basin, Russia). The spectral coefficients characterizing the relative contribution of certain hydrocarbons to the adsorbed oil composition were determined using infrared spectroscopy. The dependences of microstructural wettability on the spectral coefficients are experimentally established. It is shown that the composition of adsorbed oil has a multidirectional effect on microstructural wettability. The presence of aromatic, oxidized, and sulfurized structures increases the hydrophobization index, whereas the presence of aliphatic and branched structures leads to its reduction. The closest relationship was noted between the microstructural wettability and the spectral coefficient that characterizes the presence of aromatic structures in the adsorbed oil.

A new type of capillary end effect in oil and gas reservoirs due to heterogeneous wettability has been justified. This type of capillary end effect is not related to the contrast of reservoir rock permeability or porosity. Nonlinear fliud flow in the layers with heterogeneous wettability has been established experimentally. The mechanism of this phenomenon is due to the new type of capillary end effect.

Особенности адсорбционно-связанной нефти газоконденсатных месторождений Н.Н.Михайлов 1,3* , О.М.Ермилов 2 , Л.С.Сечина 3 1 -Российский государственный университет нефти и газа (НИУ) им.И.М.Губкина, г.Москва; 2 -ОАО «Надымгазпром», г

The wettability by asphaltenes of siliciclastic and carbonate drill–cores from oil and gas condensate fields extracted with n -hexane and chloroform was studied. The values obtained for the drill–cores of wetting by asphaltenes indicate the effect of asphaltenes on the wettability change for various rocks.

Изучена смачиваемость асфальтенами кернов терригенных и карбонатных пород нефтяных и газоконденсатных месторождений, экстрагированных н-гексаном и хлороформом. Полученные значения смачиваемости кернов асфальтенами указывают на их определённый вклад в изменение смачиваемости различных пород.

The problem of the composition of absorption hydrocarbons and liquid condensate arises in the study of gas condensate reservoirs. From the examples of the gas condensate part of the Karachaganak, Astrakhan, and Yamburg deposits, it is shown that absorption hydrocarbons (absorption oil) contain polar components with S and O atoms in molecules. The differences in the physicochemical properties of absorbed oil and precipitated liquid condensate are revealed, as are the regularities in the composition and properties of the absorbed oil and condensate. The criteria for division of absorption oil and liquid condensate are given.

The pore space of reservoir rocks has a lot of active centers capable to form different types of bonds (from hydrogen to chemical). Therefore, almost any hydrocarbon can be adsorbed to a particular extent on the internal pore surface and form an adsorbed layer, which has a definite spatial configuration and makes contact with a certain part of the rock surface. Study of gas condensate reservoirs brings up the question of the composition of adsorbed hydrocarbons. The properties of such hydrocarbons in many giant gas condensate fields are of special interest as these compounds can serve as an additional source of resources after production of mobile-gas reserves. The performed study of gas condensate reservoirs of the Karachaganak, Astrakhan, and Yamburg fields has shown that their adsorbed hydrocarbons (adsorbed oil) have polar components with sulfur and oxygen atoms.

Experimental data on residual oil mobilization in laboratory simulation of oil displacement by water demonstrate the impact of the scale effect on this process reflected in the value of residual oil mobilization and displacement thresholds. It is established that residual oil saturation decreases with an increase in the model size used. It is shown that the sizes of clusters of the trapped oil phase correlate with the size of the laboratory model.