THE INFLUENCE OF THE TEMPERATURE GRADIENT UNDER STABLE GAS CONDENSATE COOLING ON THE COMPOSITION PARAFFIN DEPOSITS

The transportation of stable gas condensate, containing high-molecular paraffin hydrocarbons, through an onshore pipeline under low-temperature climatic conditions is complicated by the formation of paraffin deposits when the hydrocarbon feedstock contacts the cold inner wall of the pipeline. In the conditions of stable gas condensate transportation through the pipeline, the precipitated paraffins lead to a decrease of its throughput capacity, an increase of hydraulic resistance, as well as the change of the rheological properties of hydrocarbon raw materials up to the formation of a structure in the whole volume of stable gas condensate and loss of fluidity. As a result of the paraffin deposits formation process when the temperature regime of stable gas condensate transportation changes a significant layer of paraffin deposits may accumulate. The nature of paraffin deposits is determined by a variety of reasons, and the consequence of paraffin deposits can be the appearance of a paraffin layer in the pipeline or equipment as insignificant, practically imperceptible during operation for a long time, and significant, leading to substantial overlap of the cross-section on long sections of the pipeline. The wax deposited in pipelines can increase pressure drop by reducing the area open to flow, which would result in an increase of the transportation cost. The formation of wax deposits in stable gas condensate is possible if two conditions are met: the temperature of the transported liquid is below the temperature of the beginning of wax crystallization (Cloud Point / Paraffin Appearance Temperature) and the positive temperature gradient of the transported liquid and the inner surface of the pipeline wall.The process of formation of a solid paraffin precipitate in stable gas condensate at change of temperature gradient between the solution and the adsorbing surface is investigated in this work. The influence of the process temperature on the amount and the component composition of paraffin hydrocarbons precipitate are shown.