The development of bituminous oil fields associated with the solution of serious technological and economic challenges. The technology of steam assisted gravity drainage (SAGD), which is successfully used at the Ashalchinskoye field in the Republic of Tatarstan, is used to develop deposits of ultra-viscous oil. However, in the development of the boundary zones of the field, where significant oil reserves are concentrated, this technology cannot be used due to the small thickness of the formation and the inability to place paired production and injection wells to realize steam-gravity effects on the formation. The wells located in the boundary zones of the formation are subjected to steam cycling, alternating with the selection of heated oil, and are characterized by marginal economic efficiency. The solvent injection is considered method to be promising for increasing the production of reserves of the boundary zones formation, for additional washing off of oil, for increasing the drainage zone of wells and for developing reserves not affected by steam.
Therefore, the actual problem is to choose the optimal composition of chemical reagents for various solvent compositions based on a multipurpose method developed and presented in this work by specialists of the Almetyevsk State Oil Institute. An integrated approach is that the selection of the solvent composition is carried out by a high degree of viscosity reduction in a solution with bituminous oil, by a high degree of oil washing from the rock, by the ability to reduce surface tension, by a high degree of diffusion. The multipurpose approach consists of choosing a solvent composition of the highest degree of reduction in the viscosity of bituminous oil, the highest degree of washout of oil from the core, the ability to reduce surface tension and a high degree of diffusion. In addition, the solvent composition must be thermostable in a wide temperature range and must not contribute to the precipitation of asphaltenes in the sediment and the formation of persistent emulsions. Optical and rheological research methods were used to test various solvent compositions, but the final choice of the solvent composition was made taking into account the results of filtration experiments on formation models with bituminous oil. The developed solvent composition will be tested at the pilot site of the Ashalchinskoye field.
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