A heavy oil dirty oil treatment process based on SAGD residual heat utilization

Abstract

The present application relates to the technical field of thick oil and dirty oil treatment, and particularly relates to a thick oil and dirty oil treatment process based on SAGD waste heat utilization. The treatment process comprises the following steps: (1) after the thick oil and dirty oil is lifted in pressure, the thick oil and dirty oil is mixed and heated with SAGD waste heat to obtain a mixture A; (2) a demulsifier is added to the mixture A, and oil-water separation is carried out in a thermochemical dewatering separator to obtain dirty oil B and dirty water B, the dirty water B enters a water treatment system; (3) the dirty oil B is subjected to oil-water flash evaporation separation after pressure reduction to obtain dirty oil C and steam C, the steam C enters a Roots blower; (4) the dirty oil C enters a boiling evaporation separator, and meanwhile, the SAGD waste heat pipeline is delivered to the boiling evaporation separator to heat the dirty oil C, steam D generated by boiling evaporation enters an upper flash evaporation separator, and dirty oil D generated is just up to the requirements. The present application has the advantages of less dosing amount, short treatment time, high sealing rate and low water content of the dirty oil after treatment.

Description

Technical Field

[0001] This invention relates to the field of heavy oil sludge treatment technology, specifically to a heavy oil sludge treatment process based on SAGD waste heat utilization. Background Technology

[0002] Crude oil with a relative density greater than 0.92 (20℃) and a subsurface viscosity greater than 50 centipoise is generally called heavy oil. Heavy oil has a low content of light fractions, but a high content of gums and asphaltenes, as well as high levels of elements such as sulfur, oxygen, nitrogen, and metals such as nickel and vanadium. Asphaltenes and gums are high-molecular-weight surfactants, acting as natural, high-performance oil-water emulsifiers. Heavy oil produced fluids exhibit a high degree of emulsification. However, due to the high density of heavy oil and the small density difference between oil and water in the produced fluid, dehydration of heavy oil produced fluids is challenging. As the extraction volume of heavy oil increases, the amount of heavy oil sludge also increases.

[0003] Heavy oil sludge mainly originates from emulsified oil in the transition zone of the settling tank within the joint station, floating oil on top of the oil removal tank, and sludge generated by the large tank sludge removal system. It also includes oil produced during the SAGD circulation preheating stage and sludge recovered during oilfield maintenance. Heavy oil sludge is characterized by a long recovery cycle, thorough emulsification, and high impurity content. Furthermore, the viscosity, gum, asphaltenes, and mud content of heavy oil sludge are all higher than those of wellhead crude oil. Maintaining sufficient temperature during the treatment process makes it more difficult to treat than light oil sludge.

[0004] Currently, the treatment of heavy oil sludge faces challenges such as high treatment temperature, large amount of chemicals used, long treatment time, the need for external heat sources, high energy consumption, and high treatment costs, which urgently need to be addressed.

[0005] Currently, commonly used oily wastewater treatment processes both domestically and internationally mainly include thermochemical sedimentation, centrifugation, and extraction, as well as combinations of these methods, such as:

[0006] Chinese patent application CN 102399577 A discloses a thermochemical sedimentation dehydration method for aged oil in the transition zone of heavy oil. The method improves the demulsifier, synthesizes a new type of demulsifier, and employs gravity sedimentation dehydration in a large thermochemical tank. The specific steps are as follows: (1) Preparation of the new demulsifier; (2) Preparation of additives; (3) Sedimentation dehydration: The aged oil is preheated to 75℃~85℃, and 300mg / L~400mg / L of the new demulsifier and 0.5%~1.2% of the additives are added. The mixture is thoroughly mixed, and sedimentation is carried out for 8hr~12hr. A sample of the dehydrated oil from the upper and middle parts is extracted, and the water content of the purified oil is measured. The water content of the treated crude oil is ≤5%, which does not meet the technical requirements for commercial crude oil in the "Technical Conditions for Crude Oil from Mines" SY7513, and the processing time is relatively long.

[0007] Chinese patent CN 204589088 U discloses a dehydration treatment device for aged heavy oil, employing a two-stage cyclone method to increase demulsification and dehydration efficiency. Chinese patent application CN 102041038 A discloses a method for treating aged heavy oil, which also provides a demulsifier for aged heavy oil. By weight, this demulsifier comprises the following raw materials: 0.5-1% phenol, 1.5-2% styrene, 0.5-1% polyethylene polyamine, 0.5-1% formaldehyde, 0.5-1% catalyst, 40-50% ethylene oxide, and 40-50% propylene oxide. After demulsification using the high-efficiency demulsifier, the oil is separated in a horizontal three-stage screw centrifuge. Both methods involve thermochemical and mechanical centrifugal dehydration. However, due to the complex structure and poor impurity tolerance of the high-efficiency centrifuge, frequent disassembly and cleaning are required, resulting in low actual processing efficiency. The water content of the treated crude oil is 5%–8%, which also fails to meet the technical requirements for commercial crude oil in the "Technical Conditions for Crude Oil from Mines" SY7513.

[0008] Chinese patent application CN 111996033 A discloses a process for purifying oily waste. This method involves first oxidizing the oily waste to remove impurities such as ferrous sulfide and simultaneously breaking the oil-water emulsion, followed by oil-water separation. The oxidation process is achieved by adding an oxidant or by simultaneous air aeration. Oil-water separation is achieved through static sedimentation. The separated oily waste after demulsification and sedimentation is then further dehydrated and deslag-removed in a disc three-phase centrifuge to obtain purified oil. However, the oxidation and aeration processes require relatively low temperatures; therefore, this invention's process is mainly suitable for treating oily waste with low viscosity.

[0009] Chinese patent application CN 112899024 A discloses a method for dehydrating aged oil. After adding a high-efficiency demulsifier to the aged oil and centrifuging it, the oil is heated to 60°C. Salt is then added to increase the density difference between the oil and water. Finally, a disc centrifuge is used to separate the oil and water. The salt in the wastewater is recycled through a recovery process. However, this invention also adds a desalination process, which is more complex. The heating temperature is too low to meet the need to reduce the viscosity of heavy oil. Furthermore, the addition of salt at high temperatures will accelerate equipment corrosion.

[0010] With increasing demands for production safety and cost management, the treatment of heavy oil sludge is energy-intensive and difficult, and conventional chemical and physical methods are no longer sufficient to meet the treatment requirements.

[0011] Steam Assisted Gravity Drainage (SAGD) is an oil production method that injects steam from a vertical or horizontal well above a horizontal production well located near the bottom of the reservoir. The heated crude oil and steam condensate are then produced from the horizontal well at the bottom of the reservoir. It has the advantages of high oil production capacity, high oil-steam ratio, high final recovery rate, reduced inter-well interference, and avoidance of premature inter-well crosstalk.

[0012] SAGD technology generates a large amount of waste heat, including the waste heat of high-temperature produced fluids, high-temperature brine and flue gas separated by the steam-water separator of the steam injection boiler, etc. Making full use of SAGD waste heat is beneficial to reducing mining costs.

[0013] Therefore, it is essential to develop a heavy oil sludge treatment process based on SAGD waste heat utilization that can solve the above-mentioned technical problems. Summary of the Invention

[0014] The purpose of this invention is to overcome the shortcomings of the prior art and provide a closed-loop treatment process for heavy oil sludge based on SAGD waste heat utilization. This process makes full use of SAGD waste heat to increase the treatment temperature of sludge, reduce the viscosity of sludge, and increase the density difference between oil and water. At the same time, it uses physical methods based on the principles of pressure reduction flash evaporation and boiling evaporation to perform deep oil-water separation of sludge. It requires less chemical dosage, has a short treatment time, a high sealing rate, and results in low water content in the treated sludge.

[0015] This invention is achieved through the following technical solutions:

[0016] A heavy oil sludge treatment process based on SAGD waste heat utilization includes the following steps:

[0017] (1) After increasing the pressure of the heavy oil sludge, it is mixed and heated with the residual heat of SAGD to obtain mixture A;

[0018] (2) Add a demulsifier to mixture A and separate oil and water in a thermochemical dehydration separator to obtain sludge oil B and wastewater B. Wastewater B enters the water treatment system.

[0019] (3) After the sludge B is depressurized, it undergoes oil-water flash evaporation separation to obtain sludge C and steam C. Steam C enters the Roots blower.

[0020] (4) The sludge oil C enters the boiling evaporator separator, and at the same time, the SAGD waste heat pipeline is transported to the boiling evaporator separator. The SAGD waste heat heats the sludge oil C through the heating coil in the boiling evaporator separator. The steam D generated by the boiling evaporation enters the upper flash separator, and the generated sludge oil D meets the requirements.

[0021] Preferably, steam C and steam D are pressurized to 0.03-0.06 MPa by a Roots blower before being sent to the heat exchange system.

[0022] The heat exchange system is a downstream process for recovering light components and condensate, avoiding environmental pollution and water loss.

[0023] Preferably, in step (1), the lifting pressure of the heavy oil sludge is 0.6 to 1.0 MPa, and the temperature of mixture A is 130 to 150°C.

[0024] Preferably, the waste heat from SAGD in steps (1) and (4) is steam at 150°C to 160°C.

[0025] More preferably, the SAGD waste heat in steps (1) and (4) is oil-carrying steam at 150°C to 160°C, which can be replaced by other steam at the same temperature.

[0026] More preferably, step (1) includes the following steps:

[0027] The pressure of the heavy oil sludge is increased to 0.6-1.0 MPa, and it is mixed and heated with the residual heat of SAGD to raise the temperature of the heavy oil sludge to 130℃-150℃, thus obtaining mixture A.

[0028] Preferably, the demulsifier in step (2) is a high-temperature resistant thick oil sludge demulsifier.

[0029] More preferably, the demulsifier comprises the following components: ethylene oxide, propylene oxide, catalyst, slow-release agent, sulfonate, acetic acid, methanol, and water.

[0030] More preferably, the demulsifier comprises, by weight, the following components: 10-20 parts ethylene oxide, 10-20 parts propylene oxide, 0.2-1 parts catalyst, 4-6 parts slow-release agent, 5-10 parts sulfonate, 20-30 parts acetic acid, 10-20 parts methanol and 10-20 parts water.

[0031] More preferably, the catalyst is an alkaline catalyst.

[0032] More preferably, the catalyst is potassium hydroxide.

[0033] More preferably, the slow-release agent is a mixture of copper sulfate and zinc sulfate.

[0034] More preferably, the sustained-release agent is a mixture of 60-80% copper sulfate and 20-40% zinc sulfate by mass percentage.

[0035] More preferably, the sulfonate includes at least one of sodium sulfonate and calcium sulfonate.

[0036] More preferably, the sulfonate is a mixture of 15-30% sodium sulfonate and 70-85% calcium sulfonate by mass percentage.

[0037] More preferably, the demulsifier comprises the following components by weight: 15 parts ethylene oxide, 15 parts propylene oxide, 0.5 parts catalyst, 4.5 parts slow-release agent, 5 parts sulfonate, 30 parts acetic acid, 15 parts methanol, and 15 parts water.

[0038] More preferably, the concentration of the demulsifier in step (2) is 300 mg / L to 500 mg / L. That is, the mass-to-volume ratio of the demulsifier to mixture A is 300 mg / L to 500 mg / L.

[0039] Preferably, in step (2), the residence time of mixture A in the thermochemical dehydration separator is 4 to 6 hours, the pressure is controlled at 0.5 MPa to 0.6 MPa, and the water content of sludge B is controlled below 12%.

[0040] More preferably, step (2) includes the following steps:

[0041] Add 300 mg / L to 500 mg / L of demulsifier to mixture A, and separate oil and water in a thermochemical dehydration separator for 4 to 6 hours at a controlled pressure of 0.5 MPa to 0.6 MPa to obtain sludge oil B and wastewater B. The water content of sludge oil B is controlled to be below 12%, and wastewater B enters the water treatment system.

[0042] Preferably, in step (3), the pressure of sludge B is reduced to 0.008-0.01 MPa.

[0043] Preferably, the pressure of flash separation in step (3) is 0.01 MPa to 0.1 MPa.

[0044] More preferably, the water content of the sludge C in step (3) is 5% to 8%.

[0045] More preferably, step (3) includes the following steps:

[0046] After the sludge B is depressurized to 0.008-0.01 MPa, it undergoes oil-water flash evaporation separation. The pressure is controlled at 0.01 MPa-0.1 MPa to obtain sludge C and steam C. The sludge C contains 5%-8% water, and the steam C enters the Roots blower.

[0047] Preferably, the pressure of the boiling evaporator separator in step (4) is 0.01 MPa to 0.1 MPa.

[0048] Preferably, the water content of the sludge D in step (4) is below 2%.

[0049] More preferably, step (4) includes the following steps:

[0050] Waste oil C enters the boiling evaporator separator, and at the same time, the waste heat from the SAGD is transported to the boiling evaporator separator through the waste heat pipeline. The boiling evaporator separator is equipped with a heating coil, and the waste heat from the SAGD is used to heat the waste oil C through the heating coil. The pressure of the boiling evaporator separator is controlled at 0.01MPa to 0.1MPa. The steam D generated by the boiling evaporation enters the upper flash separator, and the waste oil D produced meets the requirements.

[0051] More preferably, the flash separation in step (3) is carried out in a flash separator.

[0052] In another embodiment of the invention, the flash separator and the boiling evaporator are two independent devices.

[0053] The beneficial effects of this invention are:

[0054] This invention makes full use of the waste heat resources of SAGD, and uses a combination of chemical and physical methods and a pressure-sealed process to separate heavy oil sludge into oil and water under high temperature and sealed conditions. It has good heating effect (130℃~150℃), low demulsifier dosage (300mg / L~500mg / L), short treatment time (less than 6h), high sealing rate (100%), and low water content of sludge after treatment (<2%).

[0055] This invention recovers light components from waste oil through closed-loop processing, overcoming the VOCs emission problem in traditional open-process treatment.

[0056] In this invention, the flash separator and the boiling evaporator are integrated and connected by two straight pipes. The liquid separated in the flash separator falls directly into the boiling evaporator below, while the vapor evaporated in the boiling evaporator rises directly to the flash separator. This integrated design reduces pipe length and pressure drop, reduces temperature loss, and reduces the number of devices. At the same time, the rising structure of the two-stage flash separator can fully separate water and light components from heavy oil.

[0057] This invention optimizes the composition of the demulsifier by adding heat-resistant groups based on sulfonates, enabling the agent to withstand temperatures up to 220°C. Simultaneously, this invention improves the demulsifier's activity and demulsification efficiency through the synergistic modification effect of acetic acid and sulfonates, while reducing demulsification time and dosage. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of the closed-loop treatment process for heavy oil sludge according to the present invention.

[0059] Figure 2 This is a cross-sectional structural diagram of the boiling evaporator separator of the present invention.

[0060] The attached diagrams are labeled as follows: 1-Boost pump; 2-Waste heat mixer; 3-Thermochemical dehydration separator; 4-Pressure reducing valve; 5-Flash separator; 6-Boiling evaporator separator; 61-SAGD waste heat steam inlet; 62-Sludge oil inlet; 63-Evaporation steam outlet; 64-SAGD waste heat steam outlet; 65-Drain outlet; 66-Sludge oil outlet; 67-Waste heat steam tube bundle; 68-Evaporation chamber; 69-Oil chamber; 610-Baffle plate; 7-Roots blower. Detailed Implementation

[0061] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer as a result. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0062] Example 1

[0063] A closed-loop treatment process for heavy oil sludge based on SAGD waste heat utilization is illustrated in the following flowchart. Figure 1 As shown, it includes the following steps:

[0064] 1) The waste oil recovered by the No. 2 Heavy Oil Joint Station of Xinjiang Oilfield is boosted and pressurized by booster pump 1: the weight is 550t / d, the water content is 40%, the temperature is 67℃, and the pressure is 0.6MPa.

[0065] 2) The lifted sludge oil and SAGD waste heat are mixed and heated through waste heat mixer 2: SAGD waste heat temperature 160℃, sludge oil weight 550t / d, water content 40%, temperature 150℃, pressure 0.5MPa.

[0066] 3) Add demulsifier: The demulsifier concentration is 500 mg / L. By weight percentage, the demulsifier comprises the following components: 15% ethylene oxide, 15% propylene oxide, 0.5% catalyst (potassium hydroxide), 4.5% slow-release agent (a mixture of 70% copper sulfate and 30% zinc sulfate), 5% sulfonate (a mixture of 20% sodium sulfonate and 80% calcium sulfonate), 30% acetic acid, 15% methanol, and 15% water.

[0067] 4) After adding demulsifier, the high-temperature sludge enters the thermochemical dehydration separator 3 for oil-water separation. The sludge is separated in the separator and then goes to the pressure reducing valve 4. Sewage treatment system: The retention time is 4.6 hours. The weight of the remaining sludge after separation is 390t / d, the water content is 11%, the pressure is 0.5MPa, and the separated sewage is 160t / d.

[0068] 5) After the sludge is depressurized by the pressure reducing valve, it enters the flash separator 5 for oil-water flash separation. The separated sludge goes to the boiling evaporator separator 6 through the sludge inlet 62, and the flash steam goes to the Roots blower 7. The remaining sludge weight after separation is 374t / d, with a water content of 7% and a pressure of 0.01MPa. The separated water vapor is 16t / d.

[0069] 6) The sludge separated by the flash separator enters the evaporation chamber 68 of the boiling evaporator through the sludge inlet 62. Simultaneously, the SAGD waste heat pipeline is transported through the SAGD waste heat steam inlet 61 to the waste heat steam tube bundle 67 inside the boiling evaporator. The waste heat steam tube bundle heats the sludge separated by the flash separator, raising its temperature to above 110°C. The water in the sludge boils and evaporates at high temperature, changing phase to water vapor and separating from the sludge. The steam generated by boiling evaporation enters the upper flash separator through the evaporation steam outlet 63. After flash evaporation, the sludge is dehydrated and qualified for export. The SAGD waste heat steam, after completing heat exchange, flows out through the SAGD waste heat steam outlet 64. The low-water-content sludge obtained after boiling evaporation crosses the baffle 610 and enters the oil chamber 69. After buffering in the oil chamber, it flows out through the sludge outlet 6, and is exported as qualified sludge. The sludge and wastewater generated by the boiling evaporator are periodically discharged through the drain outlet 65. The waste heat temperature of SAGD is 160℃, the weight of the remaining sludge oil after separation is 353t / d, the water content is 1.4%, the pressure is 0.01MPa, and the separated water vapor is 21t / d.

[0070] 7) The steam separated by the flash separator and the boiling evaporator is pressurized by the Roots blower and then sent to the heat exchange system: 37t / d of steam, pressure 0.03MPa.

[0071] The water content of the heavy oil sludge treated in this embodiment decreased from the initial 40% to 1.8%, the treatment time was 4.6 hours, 40 t / d of SAGD waste heat was utilized, and 37 t / d of steam condensate was recovered.

[0072] The demulsifier of this invention comprises the following components by weight: 10-20 parts ethylene oxide, 10-20 parts propylene oxide, 0.2-1 parts catalyst (potassium hydroxide), 4-6 parts slow-release agent (a mixture of 70% copper sulfate and 30% zinc sulfate), 5-10 parts sulfonate (a mixture of 20% sodium sulfonate and 80% calcium sulfonate), 20-30 parts acetic acid, 10-20 parts methanol, and 10-20 parts water. Six demulsifiers, A, B, C, D, E, and F, are obtained by varying the proportions of their components. The proportions of each component are shown in Table 1. Demulsifier D is the agent used in Example 1 of this invention.

[0073] Table 1

[0074]

[0075] The above six agents were used to conduct an indoor dehydration evaluation test on heavy oil sludge with a water content of 40%: the dehydration temperature was 180℃, and the water content was required to be about 2% for the dehydrated sludge. The dosage of different agents and the dehydration time are shown in Table 2.

[0076] Table 2

[0077] Serial Number Demulsifier Name Concentration ppm Dehydration time h The removed sludge contains % water. 1 Demulsifier A 1000 20 2.1 2 Demulsifier B 800 15 1.8 3 Demulsifier C 500 10 2 4 Demulsifier D 500 8 1.5 5 Demulsifier E 800 15 2.5 6 Demulsifier F 1200 18 3.0

[0078] Table 2 shows that demulsifier D has the lowest concentration, shortest dehydration time, and best dehydration effect. The dosage ratios of demulsifiers A and B are not within the scope of this invention; however, even with higher dosages, their dehydration times are significantly longer than those of demulsifiers C and D. Compared to demulsifier D, demulsifiers E and F, by removing either the acetic acid or sulfonate component, respectively, resulted in significantly longer dehydration times, indicating that demulsifier D's demulsification effect is significantly superior to that of demulsifiers E and F.

[0079] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A heavy oil sludge treatment process based on SAGD waste heat utilization, characterized in that, Includes the following steps: (1) After increasing the pressure of the heavy oil sludge, it is mixed and heated with the residual heat of SAGD to obtain mixture A; (2) Add a demulsifier to mixture A and separate oil and water in a thermochemical dehydration separator to obtain sludge oil B and wastewater B. Wastewater B enters the water treatment system. (3) After the sludge B is depressurized, it enters the flash separator for oil-water flash separation to obtain sludge C and steam C. Steam C enters the Roots blower. (4) The sludge C enters the boiling evaporator separator, and at the same time, the SAGD waste heat pipeline is transported to the boiling evaporator separator to heat the sludge C. The steam D generated by the boiling evaporation enters the flash separator described in step (3). The sludge D generated by the boiling evaporator separator meets the requirements. In step (1), the pressure of the heavy oil sludge is increased to 0.6~1.0 MPa, and the temperature of mixture A is 130~150℃; The demulsifier in step (2) comprises the following components by weight: 10-20 parts ethylene oxide, 10-20 parts propylene oxide, 0.2-1 parts catalyst, 4-6 parts slow-release agent, 5-10 parts sulfonate, 20-30 parts acetic acid, 10-20 parts methanol, and 10-20 parts water; the catalyst is potassium hydroxide; the slow-release agent is a mixture of copper sulfate and zinc sulfate. The pressure for flash separation in step (3) is 0.01~0.1 MPa; In step (4), the heating temperature of the sludge oil C is above 110℃; The flash separator and the boiling evaporator are integrated and connected by two straight pipes. The liquid separated in the flash separator falls directly into the boiling evaporator below, and the steam evaporated in the boiling evaporator rises directly to the flash separator. The waste heat of SAGD in steps (1) and (4) is steam at 150°C to 160°C.

2. The processing technology according to claim 1, characterized in that, Steam C and steam D are pressurized to 0.03~0.06 MPa by a Roots blower before going to the heat exchange system.

3. The processing technology according to claim 1, characterized in that, In step (2), the concentration of the demulsifier is 300 mg / L to 500 mg / L.

4. The processing method according to any one of claims 1-2, characterized in that, In step (2), the residence time of mixture A in the thermochemical dehydration separator is 4 to 6 hours, the pressure is controlled at 0.5 MPa to 0.6 MPa, and the water content of sludge B is controlled below 12%.

5. The processing technology according to claim 1, characterized in that, In step (3), the pressure of sludge oil B is reduced to 0.008-0.01 MPa.

6. The processing technology according to claim 5, characterized in that, In step (3), the water content of the sludge oil C is 5%~8%.

7. The processing technology according to claim 1, characterized in that, In step (4), the pressure of the boiling evaporator separator is 0.01~0.1MPa.

8. The processing technology according to claim 1, characterized in that, In step (4), the water content of the sludge D is below 2%.

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