RU2164435C1 - Plant for treatment of heavy asphalt-resinous oil - Google Patents

Abstract

FIELD: oil producing industry. SUBSTANCE: plant has four stages of oil treatment. The first stage is for preliminary dewatering of oil; the second stage, for deep dehydration; the third stage, for deep desalting of oil; and the fourth stage, for filtering of dehydrated and desalted oil in flow-through pressure filtering unit. EFFECT: higher efficiency of plant due to production of commercial oil for heat-exchange devices and heaters. 4 cl, 1 dwg, 3 tbl

Description

The invention relates to the oil industry, in particular to installations for the preparation of heavy oil fields, a density of more than 900 kg / m ³ , asphalt-resinous oil with high foaming and stabilizing ability in relation to an emulsion of the type "water in oil".

 A well-known unified scheme for the collection and preparation of oil well products, including wells, an automatic metering unit, a demulsifier reagent dosing unit, a first stage separator, an oil pre-dewatering apparatus (or tank), a crude oil pump, a heat exchanger, and a crude oil heating unit (tubular) furnace), a block of deep oil dehydration, a mixer of dehydrated oil with fresh water, a block of deep desalination (electric dehydrator), a separator of the 2nd (hot) stage, a tank of salable oil, a pump for pumping t ovarian oil.

 The unified scheme provides for an additional supply of a demulsifier reagent to receive a crude oil pump after its preliminary dehydration, return (recirculation) of hot drainage water from a deep dehydration unit to a crude oil line in front of the 1st stage separator, and hot desalinated water from an electric dehydrator to a previously dehydrated line oil after the heat exchanger in front of the deep oil dehydration unit. Hot oil, after a deep desalination unit, having passed the heat exchanger, heats the crude oil and, when cooled, enters the commodity tank from which it is pumped to the consumer.

 The produced water that separated during the destruction of the crude oil emulsion and the flushing fresh water used to desalinate the dehydrated oil, after the above recycles, are mixed in the apparatus (tank) for the preliminary dehydration of oil, from where they are supplied to the water treatment and treatment plant for its subsequent use in the reservoir maintenance system pressure.

 Petroleum gases separated in the 1st stage (high pressure gas) and the 2nd - hot stage (low pressure gas) are sent to the gas processing plant for processing (Baykov N.M., Pozdnyshev G.N., Mansurov R.I. ., Collection and field preparation of oil, gas and water. M., Nedra, 1981, pp. 71-81).

 The disadvantage of standardized technological schemes for collecting, preparing oil, gas and water in oil-producing regions is that these technological schemes are designed to equip fields of low-viscosity light or medium density oils with high gas content (i.e., to equip oil fields in Western Siberia and the Urals Volga region and other regions that provide the bulk of oil production with the quality of marketable oil that meets the requirements of GOST 9965-76 "Oil. The degree of preparation for the oil refinery abatant enterprises. Technical conditions. "), proved to be hardly acceptable for the preparation of heavy, with a small gas factor, highly viscous, foamy oils, in which the content of asphalt-resinous components is an order of magnitude higher than in oils of Western Siberia.

So, for example, if for the oils of Western Siberia the high quality of marketable oil (group I according to GOST 9965-76) was achieved at oil treatment plants at temperatures: at the preliminary dehydration stage within 10-20 ^o C, at the deep dehydration stage 35-40 ^o C and desalination stages of 45-50 ^o C, then for the preparation of heavy asphalt-tar oils only up to quality group III according to GOST 9965-76 (water content of 1.0 wt.% And chloride salts of 1800 mg / l) it was required that the temperature at the stage preliminary dehydration of oil was no lower than 45 ^o C, n and the stages of deep dehydration of oil - not lower than 70 ^o C, and the degree of desalination - not lower than 80 ^o C.

To achieve such high temperature parameters, heavy asphalt resin oil is heated in heat exchangers or tube furnaces to temperatures exceeding 150-200 ^o C. The latter is inevitably accompanied by the deposition of coke and salts on the heat exchange surfaces, which, in turn, reduce heat transfer between the oil and these surfaces. In addition, salt and coke deposits reduce the throughput of heat exchanger tubes and furnaces, up to complete blockage, which leads to local overheating of individual sections of the flame tubes. Overheating of the surface of the flame tubes is the main cause of burnout and ignition of the tube furnaces.

 The formation of crystalline salts in the volume of highly viscous asphalt-resinous oil at a high temperature of its heating as a result of evaporation of microdrops of formation water subsequently sharply reduces the efficiency of the desalination process of such oil even with a significant (10% or more) flow rate of flushing fresh water.

 This, in particular, should explain the fact that in foreign practice the preparation of heavy asphalt-tar oils is carried out at relatively low temperatures in a mixture with crude, low-viscosity oils.

In cases where oil fields are represented only by heavy oils, for example, the Kansas West field (USA) or Muf KO (USA), the oil is prepared in these fields by the usual thermochemical method (early near-well processing of crude oil with a demulsifier reagent, heating to a temperature 50-70 ^o C and prolonged (for several days) sedimentation in the water separator tanks to obtain oil with a residual water content of 1-2% and chloride salts in the range of 1200 - 2000 mg / l).

 In the future, such oil in small volumes, by road or rail, is delivered to oil refineries (refineries), where before refining, mixed with low-viscosity oils, it is again subjected to deeper dehydration and desalination. (Tronov V.P. "Field oil preparation abroad", M., "Nedra", 1983, 224 pp.).

 The disadvantages of this technology for the preparation of heavy asphalt-resinous oils are the impossibility of supplying them to oil pipelines, which pump marketable oil to refineries or for export, with a small (not more than 100 mg / l) content of chloride salts, as well as high additional costs, associated with autonomous delivery and re-dehydration and desalination at a refinery of heavy asphalt-resinous oils mixed with low-viscosity light oils.

 The closest analogue to the proposed technical solution is an oil treatment unit, including a first stage of preparation with a preliminary water discharge tank having an oil pipeline, and a second and third stage of oil dehydration and desalination with an outlet pipe for low-mineralized produced water, characterized in that it is equipped with an additional intermediate stage of preparation containing a technological tank connected by an oil pipeline to a preliminary water discharge tank, and a pipeline outlet brackish water bottom with stages II and III treatment of oil coupled with the pipeline before the process vessel (RU 2104739 C1, B 01 D 19/00, publ. 20.02.98 Bulletin g. N 5).

 The main disadvantage of this installation is the use in the technological scheme for heating pre-dehydrated oil before it enters the stage of deep dehydration and desalting of heat exchangers and heaters, the reliability of which at high heating temperatures of heavy asphalt-tar oils is extremely low.

 In addition, it is advisable, as provided for in standardized schemes, to reuse practically fresh water separated at the stages of deep desalination of oil for processing (desalting) pre-dehydrated oil.

 After this, this water in a mixture with produced water, separated at the stage of deep oil dehydration, should be supplied to the oil pipeline in front of the technological tank - the tank for preliminary oil dehydration.

 The aim of the invention is the creation of a reliable and fireproof installation for the preparation of heavy asphalt-resinous oil, which ensures the production of marketable oil of at least quality group I according to GOST 9965-76, i.e. production of commercial oil with a water content of not more than 0.5% and chloride salts of not more than 100 mg / l.

The goal is achieved by the fact that the well-known oil treatment unit additionally includes the IV stage - the stage of hot filtration, and maintaining the required oil treatment temperature at I, II and III stages is carried out by mixing the processed products with part of the hot stream (80 ^o C) anhydrous oil, returned from the IV stage, and hot (95-100 ^o C) fresh water supplied to the dehydrated oil stream before the desalination stage.

In this case, hot (80 ^o C) weakly mineralized drainage water separated at the desalination stage is mixed with pre-dehydrated oil coming from the first stage of oil preparation, and hot (65-70 ^o C) drainage water separated at the second stage of oil preparation , return to the head of the process, i.e. fed to the separator in a stream of crude oil coming from the field, thereby ensuring the necessary (at least 40 ^o C) temperature of gas separation and preliminary water discharge at stage I of oil preparation.

Thus, along with the inclusion of an additional IV stage of oil preparation (the stage of oil refining by hot filtration) in the proposed installation, another significant feature that distinguishes the proposed installation from the known one is the provision of the required heating temperature of the processed products at each stage of preparation by the most effective method, namely by mixing with a certain volume of a hotter liquid coolant, to achieve the following parameters:
- temperature 40 - 45 ^o C at the stage of preliminary dehydration of oil, by mixing with hot (70 ^o C) weakly mineralized drainage water, separated at the stage of deep dehydration of oil;
- temperature 70 ^o C at the stage of deep oil dehydration, by mixing with hot (80 ^o C) weakly mineralized water, separated at the stage of desalination of oil, and hot (80-85 ^o C) unfiltered oil, returned from the additional IV stage of oil refining by hot filtering.

Thus, the proposed installation for the preparation of heavy asphalt-resinous oil does not contain any heat exchange equipment at all, and the heater available in the technological scheme is used only to heat the flushing fresh water to a temperature of at least 95-100 ^o C.

 The proposed installation (see drawing) works as follows.

 Watered gas-liquid oil products treated with a demulsifier, through a pipe 1 enters the block separator 2, where the gas is separated. Then, the oil-water emulsion enters the pre-discharge tank 3, where the bulk of the produced water is discharged, which through the pipe 4 enters the water treatment tank 5, and the pre-dehydrated oil is fed through the overflow pipe 6 from the tank 3 to the deep settler (or electrodehydrator) oil dehydration 8.

 Heating of the treated water-gas-liquid product to a predetermined temperature and intensification of the gas separation process in the separator 2 and produced water in the tank 3 are carried out by returning hot water with a residual content of demulsifier reagent separated from the sump (electric dehydrator) 8, through pipeline 9 to pipeline 1 in front of the separator 2.

 Heating of the processed products and intensification of the process of deep dehydration of oil in the sump 8 is carried out by supplying a pump 7 through the pipeline 10 with hot low-mineralized drainage water, separated from the sump (electric dehydrator) 11 stages of deep desalination of oil through the pipeline 12 of hot oil that has not been filtered in pressure flow filter 13 through the pipe 14 a certain amount of reagent demulsifier dosed from the reagent block 15.

Heating to a predetermined temperature and intensification of the process of oil desalination in the sump (electric dehydrator) 11 is carried out by mixing in the mixer 16 mounted on the pipeline, anhydrous oil 17 coming from the sump 8, with hot (95-100 ^o C) rinsing fresh water supplied through the pipe 18 with a pump 19 pumping fresh water from the fresh water tank 20 through the heater 21.

 The filtrate is a part of the dehydrated and desalted oil stream that has passed through stage IV — the stage of hot filtration in the pressure flow filter unit 13, as a marketable product with a residual water content of not more than 0.5% and salts of not more than 100 mg / l through the device 22 enters non-pressure tank 23, from where it is pumped to the tank of commodity oil 25 by a pump 24.

To maintain the specified mode of oil filtration in the filter unit 13 through the pipe 18a, a supply of hot (95-100 ^o C) fresh water to the device 22 for periodic countercurrent washing in the filter unit 13 of the filter elements is provided.

 Water purified by sedimentation in the reservoir 5 is pumped as necessary into the injection wells of the reservoir pressure maintenance system or the absorption wells.

 The oil separated in the water treatment tank 5, as it accumulates, is pumped through the overflow pipe 26 by a pump 27 through a pipe 28 to a pipe 9 and then to the beginning of the process, i.e. pipeline 1.

 As an example of the implementation of the proposed technical solution in table. 1 presents data on raw materials and heat flows for various sub-processes for the preparation of heavy high-viscosity oil of the Verkhozimskoye field (Penza region).

 General information on the composition, physico-chemical properties and volumes of prepared products of oil wells of the Verkhozimskoye field are given in table. 2.

 In the table. 3, for comparison, data are presented that characterize the achieved quality of commercial oil, and the main technological parameters of the existing oil treatment unit of the Verkhozimskoye field, operating according to the well-known technological scheme, and the installation for the preparation of the same oil using the proposed technical solutions.

From the presented data it follows that the proposed installation for the preparation of heavy high-viscosity asphalt resin oil has the following advantages:
- allows to obtain marketable oil of higher quality, in particular to reduce the residual water content in marketable oil by 2-3 times, chloride salts by almost 20 times, which allows the use of main pipeline transport for the supply of heavy asphalt resin to refineries or for export;
- there is no need for frequent stops and maintenance work on cleaning heat exchangers and heaters from deposits of salts and coke, which not only improves the general environmental situation at the oil treatment facility, but also increases its reliability and fire safety.

Claims (4)

 1. Oil treatment unit, including the first stage of oil preparation with a separator and a preliminary water discharge tank, a pump for pumping pre-dehydrated oil to the second stage (into the sump of deep oil dehydration) and to the third stage (into the sump or electrodehydrator of deep oil desalination), which has pipelines withdrawal of low-mineralized hot water and its return from the II stage to the first stage of oil preparation, and from the III stage to the second stage of oil preparation, the drainage water outlet pipeline from I s up (reservoir pre-discharge) into the water purification tank and the pipeline for returning oil trapped in the water purification tank to the first stage of oil preparation, characterized in that the installation further comprises an IV stage - a stage of filtered purification of dehydrated and desalted oil in a flowing, pressure head filtration unit connected by an oil pipeline to a sump (electric dehydrator) of the III stage of oil preparation.  2. The oil preparation unit according to claim 1, characterized in that the pressure head filtration unit of the IV stage of oil refining comprises a device for outputting refined oil (filtrate) to an intermediate pressureless tank for receiving and pumping commercial oil.  3. The oil treatment unit according to claim 1 or 2, characterized in that the pressure head filtering unit of the IV stage of oil refining is connected by an oil pipeline to a feed pump for pumping pre-dehydrated oil from the preliminary discharge tank to the II stage of oil preparation.  4. The installation of oil preparation according to claim 1, 2 or 3, characterized in that the device for outputting refined oil (filtrate) of the filtration unit is connected by a pipeline to the hot fresh water supply line to the III stage of oil preparation.

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