Asphalt, resin and paraffin deposits in the tubing string of oil producing wells can be identified by oilfield workers. The main symptoms are the depression of donwhole pumping equipment performance and the decreasing of well flow rate with a relative regularity of other key factors. Such estimations can give only a qualitative picture of sediment formation in the tubing and do not allow to determine the mass and volume of sediments. The latter parameters are important if one needs to determine the volume of organic solvent to be pumped in the tubing using one of the existing technologies. Operators have a practice of passive running of downhole pumping equipment (when in the course of time fluid production decreases). Such decrease id caused by the accumulation of sediments in the downhole pump and the tubing string. When the flow rate of well is significantly decreased or even stopped, the tubing string and the pump are pulled out of hole and revised. The sediments are removed by means of steam cleaning, while the old pump is replaced with the new one. Organic solvents can fully remove the sediments formed in the tubing. But they are rather expensive. That’s why in order to cut costs of such treatments, it’s necessary to precisely know the volume of sediments in the tubing string.

To address this issue, we can use the so-called “reference fluids”. These are the fluids with unvarying properties, which differ from the properties of well fluids. There are two categories of “reference fluids”. Such fluids can be delivered from the surface into the tubing string with the help of a special tube that runs through the annulus, from the wellhead down to the pump. Salt water can be used as a “reference fluid”. It’s volume in the tubing string can show the volume of asphalt, resin and paraffin deposits. It is more sensible to use organic solvent as a “reference fluid”. It can fulfill two functions: quantitatively indicate the presence of sediments and remove some part of them after a while.

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