Technical and technological solutions and calculations of the process of separation of mechanical impurities at the inlet oil separation unit

Background. With an increased removal of mechanical impurities (sand, proppant, etc.) from production wells, the largest amount of these impurities accumulates (precipitates) in the inlet separator, as in the first capacitive apparatus in the direction of well production. Typical oil and gas separators do not provide for the possibility of accumulation and removal of mechanical impurities. This leads to the ingress of mechanical impurities into the apparatus of the oil treatment plant and disruption of the operation of these apparatuses.          

Aim. To trap the settling solid particles of impurities, it is proposed to create a stationary water zone in the lower part of the separator by placing the inlet of the liquid outlet fitting at a certain height from the bottom of the apparatus and remove the mechanical impurities accumulating in it from the apparatus together with water through special outlet pipes.

Materials and methods. Mechanical impurities are removed from the separator along with part of the water through the drain fittings and sent to the drainage tank, which consists of two compartments. The sludge settles and accumulates in the first compartment of the tank, from where it is pumped out for disposal by a special submersible pump. After the first compartment is filled, the top layer of desludge-free water flows through the partition between the compartments and fills the second compartment. From the second compartment, the water purified from sludge is recirculated by a submersible pump into the water zone of the apparatus to the inlet of the sludge-washing nozzles.

Results. The technological calculation of an apparatus of design size for the ability to separate and trap mechanical impurities consists in determining the time of sedimentation of mechanical impurities from a moving liquid layer into a stationary (underlying) layer of water (τ_os), and comparing this time with the potential residence time of the liquid in the apparatus (τ_lw). To ensure the precipitation of mechanical impurities, it is necessary that the residence time of the liquid in the apparatus be longer than the time for the particle to reach the surface of the water layer, i.e. τ_lw > τ_os.

Conclusions. Calculated dependences are given to determine the rate and time of sedimentation of mechanical impurities in the modified inlet separator, depending on the modes of its operation and the physical and chemical properties of well products.

The results of calculations of the settling time of mechanical impurities (true density ρ³, depending on the size of the deposited particles _pr = 2500 kg/m³) in oil separated from gas in the inlet separator with a volume of 100 m at various flow rates of the liquid, are presented.

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