RU2179533C2 - Process for treating oil-field waste waters and plant for implementation thereof - Google Patents

Abstract

FIELD: crude oil production. SUBSTANCE: process includes feeding initial waste water into settler as ascending flow, withdrawal of oil, gas, and purified water. According to invention, prior to be fed into settler, waste water is subjected to vacuum treatment in destabilizer following the conditions: P_in≥ 1,05(ρ/2)(α+ε_in)V $\genfrac{}{}{0ex}{}{\text{2}}{\text{W}}$ and P_out≤ 0,95(ρ/2)(1-ε_out-d $\genfrac{}{}{0ex}{}{\text{4}}{\text{m}}$ /D_out)V $\genfrac{}{}{0ex}{}{\text{2}}{\text{m}}$ , where P_in is inlet pressure in destabilizer, P_out outlet pressure in destabilizer P_in inlet pressure in destabilizer; ρ density of water, α Coriolis coefficient, ε_in coefficient of hydraulic resistance in outlet section V_m water speed in destabilizer mouth; ε_out coefficient of hydraulic resistance inlet section; d_m diameter of mouth, and D_out destabilizer outlet diameter, whereas pressure in settler does not exceed pressure saturation of water with gas before being fed into treatment zone. Waste water treatment plant comprises horizontal settler, destabilizer containing convergent tube conjugated with mouth and having length equal to at least two diameters, diffuser with variable obliquity between 5 and 5 deg. Destabilizer is also provided with driven adjusting needle with variable obliquity between 20 and 8 deg. Settler is provided with interior wall having inclined gutter in its upper part to let liquid overflow. Interior wall separates settler into preliminary and major chambers. The former includes transversal greed. EFFECT: enhanced efficiency of degassing due to vacuum treatment of initial water and use of destabilizer in plant. 2 cl, 1 dwg

Description

 The invention relates to the field of oil industry, in particular to the treatment of oil wastewater.

 Known methods for the purification of oil wastewater, including the supply of source water to the sump upstream [ed. testimonial. USSR 1346182, class B 01 D 17/028, 1985].

 Known installation of oilfield wastewater treatment, containing a sump with a pipe for water input [ed. testimonial. USSR 1346182, class B 01 D 17/028, 1985].

 But in known solutions, the need to maintain a differential pressure in the input-output section requires additional energy consumption, while the entire cleaning process is complicated.

 The closest method of the same purpose to the claimed method in the group of inventions according to the totality of features is a method of purification of oilfield wastewater, including the supply of source water in the sumps upstream, the removal of oil and purified water [ed. testimonial. USSR 1502047, 1989] - adopted as a prototype.

 For reasons that impede the achievement of the following technical result when using the known method adopted for the prototype, is the fact that in the known method does not provide effective degassing of the liquid.

 The closest device of the same purpose to the claimed device in the group of inventions according to the totality of features is an installation for treating oilfield, wastewater, including a horizontal sump, pipelines for the input of wastewater and the outlet of oil, gas and purified water [ed. testimonial. USSR 1502047, 1989] - adopted as a prototype.

 For reasons that impede the achievement of the following technical result when using the known installation, adopted as a prototype, is that the installation does not provide effective degassing of the liquid.

 The technical result is an increase in the efficiency of liquid degassing due to the vacuum treatment of the source water and supplying the installation with a destabilizer.

The specified single technical result in the implementation of groups of inventions according to the object-method is achieved by the fact that in the known method of purification of oilfield wastewater, including the supply of source water to the sump upstream, the removal of oil, gas and purified water, the peculiarity is that the source water before feeding into the sump is subjected to vacuum treatment in a destabilizer in the mode:
P _in ≥1.05 (ρ / 2) (α + ε _in ) V $\genfrac{}{}{0ex}{}{\text{2}}{\text{g}}$ ;
P _out ≤0.95 (ρ / 2) (1-ε _out -d $\genfrac{}{}{0ex}{}{\text{4}}{\text{g}}$ / D $\genfrac{}{}{0ex}{}{\text{4}}{\text{out}}$ ) V $\genfrac{}{}{0ex}{}{\text{2}}{\text{g}}$ ;
where R _I - pressure at the inlet to the destabilizer;
P _o - pressure at the outlet of the destabilizer;
ρ is the density of water;
α is the Coriolis coefficient;
ε _I - the coefficient of hydraulic resistance of the input section;
V _g - the water velocity in the neck of the destabilizer;
ε _o - coefficient of hydraulic resistance of the output section;
d _g - neck diameter;
D _o - the diameter of the exit from the destabilizer;
and in the sump, a pressure is maintained that does not exceed the pressure of saturation of the water with gas before being sent for cleaning.

 This embodiment of the method, namely the vacuum treatment of the source water in the above mode before being fed to the sump, contributes to the efficient release of dissolved gas from the water, which leads to an increase in the degree of purification of oilfield wastewater, while maintaining the pressure in the sumps lower than the initial pressure of saturation of the water with water before cleaning , promotes a more complete separation of gas and oil from water and increases the degree of water purification.

The specified single technical result in the implementation of groups of inventions for the object device is achieved by the fact that in the known installation for treating oilfield wastewater, including a horizontal settler, sewage and oil, gas and water pipelines, the feature is that the plant is equipped with a destabilizer with a confuser, a neck, a length of at least two diameters, a diffuser, an adjustment needle with a drive, and the confuser is associated with a neck, with a radius of at least a diameter of the neck, the diffuser is nen in the form of a cone with an expanding end with variable conicity between 5 and 15 ^o, and the adjusting needle with variable conicity of 20 to 8 ^o, a settler provided with a partition formed with an inclined tray in its upper portion for the overflow liquid and separating the sump into two chambers - preliminary and main, and a transverse wall is installed in the preliminary chamber.

 Providing the installation with a destabilizer made in the above manner creates the conditions for preliminary vacuum treatment of the source water and efficient gas evolution from it, and a sump made with a partition and a transverse wall provides flotation treatment of water, while the inclined tray provides additional degassing during smooth overflow of liquid.

The performance of the diffuser expanded, the taper is less than 5 ^o , can lead to cavern formation, and more than 15 ^o can slow down the growth of bubbles, which worsens the process. The implementation of the adjusting needle, the taper of more than 20 ^o and less than 8 ^o complicates the regulation process.

 The claimed group of inventions meets the requirement of unity of inventions, since the group of diverse inventions forms a single inventive concept, moreover, one of the declared objects of the group — an installation for treating oilfield wastewater — is designed to implement another declared object of the group — a method for treating oilfield wastewater, both objects of the group inventions are aimed at solving the same problem with obtaining a single technical result.

 The drawing shows a device in the claimed group of inventions, which shows the installation for the purification of oil field wastewater.

 The claimed method of purification of oil wastewater is as follows.

Wastewater enters the destabilizer, operating in the following mode:
P _in ≥1.05 (ρ / 2) (α + ε _in ) V $\genfrac{}{}{0ex}{}{\text{2}}{\text{g}}$ ;
P _out ≤0.95 (ρ / 2) (1-ε _out -d $\genfrac{}{}{0ex}{}{\text{4}}{\text{g}}$ / D $\genfrac{}{}{0ex}{}{\text{4}}{\text{out}}$ ) V $\genfrac{}{}{0ex}{}{\text{2}}{\text{g}}$ ;
where R _I - pressure at the inlet to the destabilizer;
P _o - pressure at the outlet of the destabilizer;
ρ is the density of water;
α is the Coriolis coefficient;
ε _I - the coefficient of hydraulic resistance of the input section;
V _g - the water velocity in the neck of the destabilizer;
ε _o - coefficient of hydraulic resistance of the output section;
d _g - neck diameter;
D _o - the diameter of the exit from the destabilizer.

Namely, in the confuser 3, coupled with the neck 4 with a radius of at least the diameter of the neck, the water flow rate increases. Next, the water enters the neck 4, made at least two diameters long for pre-asymptotic growth of the embryos, where a vacuum is created (at the outlet), and into the diffuser 5, made with a taper of 5-15 ^° to increase the pressure when the flow is inhibited. At the exit of the neck 4 and the inlet to the diffuser 5, the pressure decreases below the saturation pressure (a vacuum is created). The resulting excess energy is sufficient for the mass emergence of bubbles of dissolved gas. Due to the formation of gas bubbles, there is a general decrease in the passage area, the growth of bubbles is accelerated, and almost all of the gas goes into the bubbles. Microdroplets of oil also contain dissolved gas and oil, and emit gas with the formation of microgerms. Since the gas content of oil microdroplets is much larger than the water surrounding them, they will grow in volume in proportion to the gas content, facilitating the emergence of microdrops. From the diffuser 5, the entire flow enters the sump 1, namely, into the preliminary chamber with the transverse wall 9, due to which large gas bubbles go up and small ones bend around it below and slowly float up, bringing oil drops to the surface of the water. The partition 7 is made with an inclined tray 8 in the upper part, which serves to drain the water and additional degassing, that is, it is possible to float the smallest bubbles that did not have time to emerge earlier.

Adjusting needle 6 with a drive and taper from 20 to 8 ^{o is} designed for additional pressure control. At the end of the process, gas, oil and purified water are discharged from the installation.

The installation for oilfield wastewater treatment includes a horizontal sump 1, a destabilizer 2, containing a confuser 3, conjugated with a neck 4 made with a length of at least two diameters, a radius of at least a diameter of the neck, a diffuser 5 made with a variable taper from 5 to 15 ^o , adjusting a needle 6 with a variable taper from 20 to 8 ^o , a partition 7 with an inclined tray 8, a transverse wall 9, located in the preliminary chamber of the sump.

Installation works as follows. Oil field water enters the destabilizer, namely, the tapering confuser 3, and the neck 4, while the confuser 3 is associated with a neck with a radius of at least the diameter of the neck, thereby increasing the flow rate of water in the confuser. In the neck 4, made with a length of at least two diameters, a vacuum is created. Then the liquid enters the diffuser 5, made expanding with a taper of 5 to 15 ^o , due to which at the entrance to it there is a gap of the liquid with the formation of bubbles of dissolved gas. Then, water with gas bubbles enters the sump 1, divided by a partition 7 into the main and preliminary chambers, while the transverse wall 9 is installed in the preliminary chamber, due to which large gas bubbles go up, while small ones go around it and also rise up, carrying oil drops. The partition 7 is made with an inclined tray 8, through which water is drained.

 The released gas, purified water and oil are discharged from the unit. Such an installation provides high-quality treatment of oilfield wastewater.

Claims (2)

1. The method of purification of oil field wastewater, including the supply of source water to the sump upstream, the removal of oil, gas and purified water, characterized in that the source water before being fed to the sump is subjected to vacuum treatment in a destabilizer in the mode:
P _inx ≥ 1.05 (ρ / 2) (α + ε _inx ) V $\genfrac{}{}{0ex}{}{\text{2}}{\text{g}}$ ;
P _outx ≤ 0.95 (ρ / 2) (1-ε _outx -d $\genfrac{}{}{0ex}{}{\text{4}}{\text{g}}$ / D $\genfrac{}{}{0ex}{}{\text{4}}{\text{out}}$ ) V $\genfrac{}{}{0ex}{}{\text{2}}{\text{g}}$ ,
where R _I - pressure at the inlet to the destabilizer;
P _o - pressure at the outlet of the destabilizer;
ρ is the density of water;
α is the Coriolis coefficient;
ε _in - the coefficient of hydraulic resistance of the input section;
V _g - the water velocity in the neck of the destabilizer;
ε _ox - coefficient of hydraulic resistance of the output section;
d _g - neck diameter;
D _o - the diameter of the exit from the destabilizer,
and in the sump, a pressure is maintained that does not exceed the pressure of saturation of the water with gas before being sent for cleaning. 2. Installation for oilfield wastewater treatment, including a horizontal sump, sewage and oil, gas and purified water pipelines, characterized in that the installation is equipped with a destabilizer containing a confuser, a neck, a length of at least two diameters, a diffuser, an adjustment needle with the drive, and the confuser is connected with a neck with a radius of at least the diameter of the neck, the diffuser is made with a variable taper from 5 to 15 ^o , and the adjusting needle with a variable taper from 20 to 8 ^o , while the sump is equipped a partition made with an inclined tray in the upper part and dividing the sump into two chambers - the preliminary and the main, and a transverse wall is installed in the preliminary chamber.