CN117164075A - Evaluation method of oilfield produced water treatment system - Google Patents

Abstract

The invention relates to an evaluation method of an oilfield produced water treatment system in oilfield produced water treatment technology. Water samples from each unit of the produced water treatment system are regularly extracted on site, the transmittance and potential values are detected, and an evaluation model and evaluation method are designed. , to achieve the evaluation of the overall treatment efficiency and stability of each treatment unit and the treatment system of the produced water treatment system, and to solve the problem of difficult to quickly quantify on-site evaluation of chemical agents such as destabilization treatment during the produced water treatment process.

Description

An evaluation method for oilfield produced water treatment systems

Technical field

The present invention relates to an evaluation method of an oilfield produced water treatment system suitable for rapid sampling, detection and evaluation of each treatment unit at the produced water treatment site during the oilfield produced water treatment process.

Background technique

After an oil field is put into development, as the exploitation time increases, the energy of the oil layer itself will continue to be consumed, the pressure of the exploited oil layer will continue to decrease, and the output of the oil well will drop significantly, resulting in the remaining oil being unable to be extracted. In order to make up for the underground deficit caused by the extraction of crude oil, maintain or increase reservoir pressure, and obtain higher recovery rates, underground reservoirs must be developed by increasing formation pressure. Oilfield water injection is still one of the most important means to replenish energy to the formation and improve oil field recovery during the oilfield development process. The object of water injection is an oil layer composed of dense rocks with different permeabilities. Therefore, the quality of water injection is required to meet certain index requirements. The quality of injected water is an important factor that determines the effectiveness of oil field water injection development. It also determines the overall development of the oil field. The length of life.

The evaluation standards for water quality are usually determined by the reservoir category and permeability physical properties of the corresponding developed strata. The industry often uses the testing methods in the corresponding industry technical standards for testing and analysis; the recommended indicators in the industry standards are used to evaluate water quality. , such as "Clastic Rock Reservoir Water Injection Water Quality Indicators and Analysis Methods" SY/T5329-2012, which is applicable to clastic rock reservoirs. The main control indicators of water quality in this standard include suspended solids, median particle diameter, oil content, SRB, TGB , IB and other 7 testing items, and the auxiliary control indicators include 5 testing items such as dissolved oxygen, hydrogen sulfide, corrosive carbon dioxide, iron, and pH value. The basic requirements for water injection water quality are generally that the water quality is stable and does not cause obvious precipitation when mixed with the oil layer water. At the same time, the water must not carry a large amount of suspended solids to prevent clogging of the formation, causing the water well to fail to inject water or the water injection pressure of the water injection well to continue to rise. Bad consequences. From the perspective of the core requirements for oilfield produced water treatment, among the 12 indicators of water quality, the most important and core indicator is suspended solids content, and its changing factors are highly correlated with the other 11 control indicators. At the same time, produced water treatment in the upstream industry In production management, the single indicator with the lowest compliance rate and the most difficult control is also the suspended solids content. However, in actual production, there is still a lack of targeted evaluation devices suitable for on-site use and corresponding to the suspended solids content and with relatively high repeatability. High quantitative evaluation and analysis methods.

In the existing technology, water quality evaluation and management in the oilfield produced water treatment process currently mainly rely on the following two tasks.

The first is water quality monitoring, analysis and management of the produced water treatment system. That is, through on-site testing of some data and indoor testing after on-site sampling of some data, water quality testing data for 12 items were obtained. Based on this, an objective assessment was made of the operating status of each unit of the surface produced water treatment system. Specifically, the current method commonly used in the oilfield industry is to rely on professional testing units within the oilfield to carry out quarterly water quality monitoring to evaluate the operation status of each unit and the overall system of produced water treatment. Generally, after on-site sampling and testing, Within 1-2 months, based on the testing data, conduct an overall system operation status assessment and water quality compliance rate analysis on the actual operation of each water quality monitoring station this quarter, compile a water quality monitoring bulletin, and propose measures, which will be issued after review by the superior department. The water quality monitoring bulletin will be sent to the oil production plant management department and the oil production plant technical management department 1-2 months after the water quality monitoring. The latter will make production parameter adjustments or adjustments to the produced water treatment system based on the water quality conditions and measure suggestions in the bulletin. Problem rectification. This monitoring, evaluation and management method has the following three problems. ① The test cycle is too long, the test data is difficult to apply quickly, and on-site problems are difficult to quickly feedback and rectify. Water quality monitoring includes 12 indicators, and each monitoring point at a site is from It usually takes 7-15 days to get the test results from the beginning (the SRB culture cycle is generally 7-15 days), and the interval between repeated tests at the same site is generally 90 days; ② The cost of testing is relatively high, and some test projects have long cycles and high costs High. For example, the secondary dilution method or the triple dilution method in the three bacterial monitoring methods requires a large amount of test bottles, the cost increases year by year, and the test cycle takes 7 days; ③ During the benchmark sampling and testing process in accordance with SY/T5329, there will be A large amount of oily hazardous waste and solid waste not only affects environmental safety, but also increases enterprise production costs.

The second is the daily management of the dosage of produced water treatment chemicals. Due to the common problems such as corrosion and scaling in the oilfield produced water treatment process and the purpose of reducing or effectively controlling 12 water quality indicators during the treatment process, it is necessary to add and dynamically adjust different types of water at different locations during the oilfield produced water treatment process. Chemical agents, so the effective addition of daily produced water treatment agents to ensure quality and quantity is another important part of on-site produced water treatment work. Due to changes in produced water formations or changes in the mixing of different produced waters during oilfield production, oilfield produced water treatment chemicals need to be periodically evaluated and the effectiveness of chemicals in treating produced water needs to be monitored. This is in line with the quality standards of produced water treatment. The level of the rate is highly correlated. At present, for the evaluation of chemicals used in produced water treatment, we often use simulation devices to collect water samples on site and evaluate them indoors to conduct periodic evaluations.

Oilfield produced water treatment systems generally have the following characteristics. First, the treatment sites are widely spread and scattered. The sites are often more than 100 kilometers apart. The high cost of producing water transportation and the actual demand for actual water injection and pressurization make the oil field industry generally use production water treatment systems. The process method of treating the effluent nearby and reinjecting it on site; secondly, the produced water treatment volume varies greatly, and the daily produced water treatment volume ranges from dozens to tens of thousands of cubic meters (site water inlet volume fluctuates by more than 30%); thirdly, the produced water treatment volume varies by more than 30%. The amount and quality of the incoming liquid water at the treatment site changes greatly (a single test parameter changes by more than 50%). Overall, there is still a lack of simple, effective, low-cost on-site rapid evaluation devices and methods for the operating status of the oilfield produced water treatment system and the overall and unit dynamic evaluation.

Through literature search and patent inquiry, there is a lack of effective water quality evaluation and management encountered in the oilfield produced water treatment process, the operating status of the produced water treatment system and unit, and the effect of chemicals used in the settlement unit in the produced water treatment system. The main solutions to the problem of assessment methods and means, both inside and outside the industry, mainly include the following aspects:

In the field of on-site production management technology based on water quality evaluation, the operation mode of most oilfield produced water stations at home and abroad still mainly relies on periodic water quality testing and evaluation carried out in accordance with industry standards to realize the production of oilfield produced water treatment systems. Maintenance management; there are problems such as too long test and feedback cycles, too high test costs, lagging on-site adjustment responses, and the lack of simple, fast, and low-cost evaluation methods. After searching for relevant information, we found that in the technical field of wastewater treatment including petrochemical, refining, chemical and other wastewater similar to oilfield produced water, there are patented technologies for online produced water monitoring and evaluation alarms, especially the use of produced water quality evaluation and analysis methods. Online turbidity testing methods, such as the sewage online turbidity detection system with patent number ZL2018206300840, use photoelectric systems to establish photoelectric balance, and install them on the water inlet of the pretreatment system and the output pipe of the subsequent pipeline mixer outlet to collect turbidity changes Data to achieve the effect of early warning and diversion of exceeded standards. The water sample collection position of the detection system is at the back end of pretreatment, and it is impossible to realize the entire process of the produced water treatment system, especially the produced water quality testing and evaluation analysis at the front end of the produced water treatment; at the same time, due to the amount of water entering the oilfield produced water treatment system , The extremely unstable water quality makes the sensors of the online test system susceptible to contamination, and the test often cannot run stably. The overall work procedure is complex and maintenance is difficult. The patent number is ZL2017800838595, which discloses a turbidimeter device, a sludge concentration device and a method for determining the turbidity of a liquid sample using a turbidimeter device. A vacuum pump is used to fill the turbidimeter test chamber container while generating low pressure to realize the liquid sample. Degas. The patent realizes automatic liquid inlet, exhaust, and liquid discharge, but the device is complex and is mainly used for sludge turbidity testing in activated sludge systems. However, this system is only suitable for activated sludge treatment processes in sewage treatment systems. Currently, most oilfield produced water treatment systems use conventional flocculation, sedimentation and filtration physical and chemical processes, and more than 90% of the remaining biological produced water treatment technologies use Contact oxidation treatment. This patent uses a vacuum pump to fill the turbidimeter test chamber container while creating a low pressure to degas the liquid sample. However, the device is complex and is mainly used for sludge turbidity testing in activated sludge systems. It is not suitable for use in oilfield produced water systems. It is expensive and difficult to maintain. In the patent with publication number CN114690700 A, an intelligent sewage treatment decision-making optimization method and system based on PLC: collects sewage quality evaluation index data, preprocesses the evaluation index data, builds a mixed sewage treatment decision-making optimization model, and combines the preprocessed The sewage quality evaluation index data is input into the mixed sewage treatment decision optimization model to obtain the PLC parameter configuration of the mixed sewage treatment decision. The final PLC parameter configuration is fed back to the PLC console. The PLC console determines the produced water treatment parameters based on the PLC parameter configuration. Modifications were made to ultimately control the sewage treatment system for optimized treatment of produced water. It is necessary to install a large number of sensors at various nodes along the route, and optimize wastewater treatment through PLV system decision-making and parameter configuration. The anti-pollution, reproducibility and adaptability of water quality sensors related to this technology are still difficult to achieve in oilfield wastewater. Overcome technical difficulties. In the patent with publication number CN109853704 A: a method for diagnosing urban sewage system problems uses the sewage lifting pump station as a node to diagnose sewage treatment water volume, water quality, compliance rate and other data, and combines the produced water treatment water volume and the water quality data indicators of the inlet and outlet water for diagnosis. , providing an effective technical support and data support for municipal drainage system management. Diagnosis and evaluation depend on a large amount of basic data from on-site produced water treatment system water volume and water quality sensor test units. The design parameters of this diagnostic method are all relevant indicators in the field of conventional external drainage treatment technology. The diagnostic calculation method is too cumbersome and is not suitable for conventional municipal water treatment. It is difficult to adapt to the oilfield produced water treatment system. The simple and fast solution technology route required under the multi-faceted characteristics of the oilfield produced water cannot solve the problem of sensor failure and test errors caused by the impact pollution of oil field produced water. Patent 5: Chinese invention patent for a comprehensive water quality evaluation method (application publication number is CN108470234A), which uses a method that integrates multiple pollution factors to evaluate water quality, and calculates by assigning weights to the proportions of different pollution factors. its overall pollution level. Similar to many similar patents, this application mainly conducts a comprehensive evaluation of the water quality of external drainage in a certain area, rather than focusing on oilfield produced water treatment systems. The inspection objects and control standards are hugely different, and the water quality evaluation method proposed is suitable for According to the overall assessment, there is no intuitive data and no quantitative standards on the influencing factors of the unit operation status and treatment effect of the produced water treatment system. It is impossible to achieve direct production management and continuous improvement of water quality of the oilfield produced water treatment system.

For the technical field of chemical effect evaluation based on field application, the chemical treatment effect evaluation method at most sites of oilfield produced water is still evaluated indoors by using relevant simulation devices. There are only new components and compositions inside the simulation device. Innovation, such as patent number ZL202122957359: a dynamic evaluation simulation device for chemicals in offshore oilfield produced water treatment systems, which consists of a chemical dosing system, a preparation tank, an oil skimmer, an air flotation device, a sloping plate oil remover, and a filtering device The small-displacement indoor produced water treatment system test device, including other main components, collects on-site water and simulates the indoor device to realize the dynamic evaluation of chemicals in the offshore oilfield produced water treatment system, and realizes the simulation of on-site temperature and flow, and the dynamic simulation of chemicals. processing effect. However, we still collect on-site water samples and use a small indoor simulation device composed of each processing unit component to simulate and evaluate the on-site chemical treatment effect. This requires transporting a large number of on-site water samples to the laboratory, which results in a long test cycle and high test costs. , and at the same time, it is impossible to achieve actual effect evaluation based on on-site process conditions after on-site chemical addition.

As stated in the review, there is currently a lack of on-site rapid evaluation methods for oilfield produced water treatment systems. In the actual production field, especially the most important water inlet position of the produced water treatment system, there is no continuous and stable application of corresponding detection and evaluation technology in oilfield produced water treatment sites. At the same time, due to the actual demand for safe and explosion-proof oilfield production systems, procurement and maintenance costs are too high, which objectively limits the use of contact sensor-type produced water testing and decision-making systems in oilfield produced water treatment systems; chemical agents for produced water treatment However, there is still a lack of simple, efficient and convenient on-site assessment technology methods.

Contents of the invention

The present invention is aimed at the problem that there are many evaluation parameters for oilfield produced water treatment systems in the prior art and there is a lack of fast, instant and effective evaluation means for on-site evaluation. It provides an evaluation method for oilfield produced water treatment systems that mainly solves the following aspects: Technical issues: First, based on the control of the main control indicators of oilfield produced water quality, multi-parameter correlation analysis, and the technical principles involved in the oilfield produced water treatment system, a method suitable for convenient on-site water quality detection of oilfield produced water treatment is proposed. An important parameter for rapid evaluation; second, it is suitable for rapid detection of on-site sampling. Based on actual test data, based on data classification and analysis under different treatment processes, an evaluation method is established to propose features for the overall and operating conditions of each unit of the oilfield produced water treatment system. An evaluation method that is operable and conducive to guiding on-site production; the third is to use evaluation methods to solve the problem that in the process of produced water treatment, chemical agents such as destabilization treatment are often encountered and it is difficult to quickly quantify on-site evaluation.

The object of the present invention is achieved in this way, an evaluation method of oilfield produced water treatment system, which is characterized in that water samples are regularly extracted for detection and evaluation through the following steps:

Step 1: Regularly release water samples from the water inlet of the oilfield produced water treatment system and the water outlet of each unit, seal them in different glass sampling barrels, and take samples according to unit marks;

Step 2: Detect the initial light transmittance of each water sample TInitial ₁ , _{TInitial 2... TInitial i} water, and the light transmittance of each water sample after standing for 30-60 minutes _{TEnd1, TEnd2... TEnd i} , detect the potential value E ₀ , E _1... E ₂ of each water sample. Step 3: Calculate the processing efficiency X _i of each unit of the produced water treatment system and the overall treatment based on the light transmittance and potential value detected in step 2. Efficiency η

Among them, the unit processing efficiency is _Xi , _Xi = unit purification rate D _i + unit stability rate K _i + unit auxiliary purification rate F _i

D _i =( _{TInitial i -TInitial i-1} )*100/TTInitial _i-1 Formula (1)

K _i ==(T _{the end i} -T _{the beginning i} )*100/T _{the beginning i} Equation (2)

F _i =(E _i-1 -E _i )*100/E _i-1 /50 Formula (3)

Among them, 50 in formula (4) is a normalized adjustment constant, and its data is based on the difference between the water sample potential and the original water sample potential of adding destabilizing agents to achieve obvious flocculation effect; Q _i is the overall system processing of each unit The contribution weight of efficiency, according to the current classification of produced water treatment processes in oil fields, is 30%, 60%, and 10% according to the settlement unit, filtration unit, and water injection unit;

Step 4: Calculate the processing efficiency Y _i of the destabilizing agent in the existing settling unit treatment system,

Y _i =(E _i-1 - E _i )*100/ E _i-1 Formula (5);

Step 5: Based on the eta value in step 3, evaluate the overall operating effect of the oilfield produced water treatment system and formulate treatment measures;

Step 6: Based on the Y _i value of the settlement unit in Step 4, formulate dosing measures.

The evaluation method of the oilfield produced water treatment system of the present invention introduces two detection items of transmittance and potential as key control evaluation indicators, forming a method suitable for rapid on-site detection of the operation of each unit along the oilfield produced water treatment system. The status evaluation method can realize the detection of key parameters such as light transmittance data that is highly related to the suspended solids content in water samples, and potential data related to sulfide, carbon dioxide content, destabilization and other chemicals. Through data processing, various calculations can be made. The processing efficiency of the unit and the effect of the overall system will be comprehensively and quickly evaluated for each functional unit and the overall system respectively, and rapid operation decisions will be made based on the evaluation structure to ensure stable operation of the treatment system and continuous and steady improvement of water quality.

Further, the oilfield produced water treatment system includes a produced water inlet, a settling unit, a filtering unit and a water injection unit connected in sequence, and a sampling port is provided at the outlet of each unit.

Further, in step 1, the periodic sampling period is 48 hours.

Furthermore, when the same functional unit includes multiple levels of units connected in series, the water outlets of each level of units are sampled separately.

Further, in step 4, the weight of each unit level is the weight of such unit divided by the number of unit levels.

Furthermore, in step 5, the overall operating effect evaluation standard of the produced water treatment system is: set the intervention thresholds for the following unit and system efficiency changes based on empirical values. When the operating efficiency of the test unit or system is lower than the intervention threshold, intervention is adopted. measure.

Further, in step 5, the intervention measure is to shorten the period of regular water sample testing to half of the original period. When the following conditions occur in two consecutive tests

η≥5 indicates that the overall system is running well and the unit is running well;

X _i ≥5, indicating that the unit system is running well and sampling is normal and regular;

When -10＜X _i ＜5, encrypted sampling, and _the result of

When the X _i index is <-10, measures are taken directly against the unit where it is located.

Further, in step 6, the evaluation standard for determining the current on-site dosing effect of the settlement unit based on the Y _i value is: Y _i ≤ 10, it is necessary to carry out drug evaluation, screening and replacement, and again determine whether the existing drugs match the water body; Y _i ≥ At 30 hours, the agent matches the on-site process conditions. When 10 < Y _i < 30, increase the dosage of settlement agent by 5% to 10%.

Furthermore, in the second step, each water sample is separately packaged in different glass test tubes before testing, and nitrogen or inert gas is introduced into the water samples in the glass test tubes to eliminate air in the tubes.

The evaluation method of the above-mentioned oilfield produced water treatment system of the present invention is based on the correlation analysis of the suspended solids content. When evaluating the oilfield produced water treatment efficiency, two parameters, light transmittance and potential value, are introduced, and converted into The calculation of the overall system efficiency enables on-site rapid evaluation of related categories of chemicals such as destabilization for oilfield produced water treatment, and enables quantitative evaluation of the operating status of produced water treatment system units and the overall system. Based on changes in treatment efficiency, problem nodes can be identified and targeted solutions can be identified. implementation plan.

Detailed ways

Based on comparative testing of a large amount of data at the oilfield produced water treatment site, the correl function correlation between the suspended solids content and various parameters was analyzed, and it was concluded that the suspended solids content and light transmittance have a good correlation, as shown in the chart.

The main control indicators in oilfield produced water are suspended solids, which mainly include various types of particulate matter. The evaluation of the operation status of the oilfield produced water treatment system and each unit system is based on the fact that such substances can cause scattering and transmission of light entering the produced water. The amount of particulate matter in the produced water is related to the size of the transmitted light; the auxiliary control indicators such as sulfide content and carbon dioxide content are related to the electrical properties of the produced water. Before the oil field produced water is treated, the potential is generally -100 to -200mv. The addition of destabilizing flocculation and sedimentation agents changes the electrical properties of the water body, and the changes in the potential data of the test unit can be used to determine the effect of the added agents in the existing process, and thereby determine its applicability on site. Based on the significant correlation between the above-mentioned light transmittance and potential value, that is, the light transmittance has a significant positive correlation with the suspended matter content, and the potential value has a significant negative correlation with the suspended matter content, it is concluded that the evaluation method of the effluent treatment system used in the oil field of the present invention is .

Example 1

In this example, the produced water treatment system of an oilfield sequentially includes produced water inlet (that is, water extracted from the formation), flocculation and sedimentation unit, buffer tank, primary filtration, secondary filtration, and water injection tank outlet water sample. , carry glass sampling buckets to sample and package at each water outlet, and then use a light transmittance meter and a potentiometer to test the electrical value of the light transmittance at the processing site. Before testing, put each water sample into a glass test tube. And pass nitrogen gas above the liquid level in the tube for at least five minutes, and evacuate the liquid level to ensure the stability of the test. The initial transmittance of each water sample tested is 73.39, 74.97, 77.41, 92.71, 98.52. , 97.35; after standing for 30 minutes, the light transmittance of each water sample was 75.67, 79.17, 92.75, 98.79, 98.19%; the potential value of each water sample was -108, -50, -56, -48, -45. , -51mv. From this data, the purification rates D _i of the flocculation and sedimentation unit, buffer tank, primary filtration, secondary filtration, and water injection tank units along the process are calculated respectively according to formulas (1) to (5), which are 2.15, 3.25, 19.76, 6.27, and - 1.19; the stability rate K _i of the unit along the way is -1.53, -0.93, -2.27, -0.04, -0.27, -0.86; the auxiliary purification rate F _i of the unit along the way is 1.07, -0.24, 0.29, 0.13, -0.27 . From this, the processing efficiency index of each unit along the process is calculated to be 2.29, 0.74, 20.01, 6.12, -2.32; the processing efficiency Y _i of the sedimentation unit (referring to the flocculation sedimentation unit and buffer tank) is 53.7; the processing efficiency of the overall system η is 8.06. Evaluate that the site unit and system are in good operating condition.

Example 2

In this embodiment, sampling, testing, evaluation and analysis are carried out on-site in another oil field's produced water treatment system. The water treatment system includes produced water, flocculation and sedimentation unit, buffer tank, primary filtration, secondary filtration, water injection tank, and its outlets. Water samples were extracted through glass sampling buckets, and then each water sample was sealed in a glass test tube. Nitrogen gas was passed above the liquid level of each test tube for 5 minutes for evacuation, and then the light transmittance of each water sample was tested through a light transmittance meter. _{The initial i} of T are 73.27, 74.74, 75.91, 85.83, 91.01, 78.32; the light transmittance of each water sample _after standing for 30 minutes is 75.89, 76.08, 85.98, 91.12, 92.17%; the incoming water, flocculation sedimentation unit, buffer The potential values E _i of the water samples at the outlet of the tank, primary filtration, secondary filtration, and water injection tank are -122, -126, -116, -105, -102, and -184mv in order. From this data, the purification rates D _i of the flocculation and sedimentation unit, buffer tank, primary filtration, secondary filtration, and water injection tank units along the process are calculated respectively according to the above formulas (1) to (5), which are 2.01, 1.57, 13.07, 6.04, respectively. -13.94; the stability rate K _i of the unit along the way is -1.54, -0.22, -0.17, -0.12, -17.68; the auxiliary purification rate F _i of the unit along the way is -0.07, 0.16, 0.19, 0.06, -1.61. From this, the processing efficiency X _i of each unit along the route is calculated to be 0.40, 1.50, 13.08, 5.97, and -33.24; the chemical processing efficiency Y _i is -3.28; and the overall system processing efficiency η is 2.68.

According to the preset evaluation criteria for each parameter according to the method of the present invention, the station unit and system are in poor operating condition. After analysis, the main problems are low efficiency of the flocculation and sedimentation unit, secondary pollution in the water injection tank, and deterioration of the pharmaceutical effect.

After discovering this problem, we conducted an evaluation based on conventional evaluation methods and conducted 12 index tests including solid content. After verification, we reached the same conclusion. At the same time, one month before the site was evaluated using the method of this embodiment, no on-site abnormalities were found in routine quarterly water quality monitoring; on-site problems were not discovered in time.

Based on the problems found in the on-site evaluation, the agents were screened and replaced within 1 week, a quick response was made, and the new agent system was replaced. The following follow-up evaluation was performed 4 days after the new agent was applied, and the oil field produced water, flocculation and sedimentation unit, and buffer tank were collected again. , primary filtration, secondary filtration, and the water sample from the water injection tank outlet were packaged into a glass test tube and then subjected to nitrogen evacuation treatment. The initial light transmittance was then measured in order of 73.83, 83.43, 82.48, 92.37, _and 98.59. , 81.25; _after standing for 30 minutes, the light transmittance T of each water sample was 83.52, 84.67, 92.67, 98.73, 93.57%; the potential value E _i of each water sample was -115, -65, -61, -63 , -67, -68mv. From this test data, the purification rates D _{i of} the flocculation and sedimentation unit, buffer tank, primary filtration, secondary filtration, and water injection tank units along the process are calculated respectively according to the above formulas (1) to (5), which are 13.00, -1.14, 11.99, and 6.73, -17.59; the stability rate of the unit along the way K _i is -0.11, -2.66, -0.32, -0.14, -17.68; the auxiliary purification rate F _i of the unit along the way is 0.87, 0.12, -0.07, -0.13, -0.03. The processing efficiencies X _i of each unit along the process are 13.76, -3.67, 11.60, 6.46, and -35.30 respectively; the pharmaceutical action efficiency Y _i is 43.48; the overall system processing efficiency η is 3.40. From this evaluation result, it can be determined that the agent efficiency has been significantly improved, but the overall system still needs to be improved, focusing on improving the efficiency of the water injection unit.

To this end, the second step of adjustment was carried out. Two water injection tanks were used in parallel. The desilting and cleaning work was carried out sequentially within two weeks. After 4 days, the following follow-up evaluation was carried out. Water samples from the water outlets of each unit system were collected again to detect the initial light transmittance. The rate T _{at the beginning i} was 68.95, 82.69, 82.57, 93.56, 98.19, 98.51; after standing for 30 minutes, the transmittance T of each water sample _{at the end i} was 83.76, 85.12, 93.69, 98.35, 98.39%; the potential of each water sample The values are -105, -58, -61, -59, -65, -62mv. From this, the purification rate D _i of each unit is further calculated according to the aforementioned formula to be 19.93, -0.15, 13.31, 4.95, and 0.33 respectively; the stability rate K _i of each unit along the process is 1.29, 3.09, 0.14, 0.16, and -0.12 respectively; The auxiliary purification rates F _i are 0.90, -0.10, 0.07, -0.20, and 0.09 in sequence. From this, the processing efficiency X _i of each unit along the process is calculated to be 22.12, 2.84, 13.51, 4.91, and 0.3; the processing efficiency _Yi of the settlement unit processing system is 44.76; and the overall system processing efficiency η is 9.30. According to this evaluation, the drug efficiency has been significantly improved, the overall system efficiency index has been improved, and on-site evaluation and response have been rapid.

In this embodiment, through the above-mentioned on-site sampling, detection, evaluation, and analysis, and gradually taking corresponding targeted improvement measures for low-efficiency unit systems, rapid detection, evaluation, rapid response, and improvement after on-site sampling are achieved to ensure that the oil field produces water Handles the stable motion of the system.

Claims (9)

1. An evaluation method for oilfield produced water treatment systems, which is characterized by regularly extracting water samples for testing and evaluation through the following steps: Step 1: Regularly release water samples from the water inlet of the oilfield produced water treatment system and the water outlet of each unit, seal them in different glass sampling barrels, and take samples according to unit marks; Step 2: Detect the initial light transmittance of each water sample TInitial ₁ , _{TInitial 2... TInitial i} water, and the light transmittance of each water sample after standing for 30-60 minutes _{TEnd1, TEnd2... TEnd i} , detect the potential value E ₀ , E _1... E ₂ of each water sample Step 3: Calculate the treatment efficiency _Xi of each unit of the produced water treatment system and the overall treatment efficiency η based on the light transmittance and potential values detected in Step 2 Among them, the unit processing efficiency is X _i , X _i = unit purification rate D _i + unit stability rate K _i + unit auxiliary purification rate F _i D _i = ( _{TInitial i} - TInitial _i-1 )*100/TTInitial _i-1 Formula (1) K _i == (i _{at the end of} T - _{i at the beginning of} T)*100/ i _{at the beginning of} T Equation (2) F _i = (E _i-1 - E _i )*100/ E _i-1 /50 Formula (3) Formula (4) Among them, 50 in formula (4) is a normalized adjustment constant, and its data is based on the difference between the water sample potential and the original water sample potential of adding destabilizing agents to achieve obvious flocculation effect; Q _i is the overall system processing of each unit The contribution weight of efficiency, according to the current classification of produced water treatment processes in oil fields, is 30%, 60%, and 10% according to the settlement unit, filtration unit, and water injection unit; Step 4: Calculate the processing efficiency Y _i of the destabilizing agent in the existing settling unit treatment system, Y _i =(E _i-1 - E _i )*100/ E _i-1 Formula (5); Step 5: Based on the eta value in step 3, evaluate the overall operating effect of the oilfield produced water treatment system and formulate treatment measures; Step 6: Based on the Y _i value of the settlement unit in Step 4, formulate dosing measures. 2. The evaluation method of the oilfield produced water treatment system according to claim 1, characterized in that the produced water treatment system includes a produced water inlet, a settling unit, a filtration unit and a water injection unit connected in sequence, and each unit has There are sampling ports at the exits. 3. The evaluation method of oilfield produced water treatment system according to claim 1, characterized in that, in the first step, the periodic sampling period is 48 hours. 4. The evaluation method of oilfield produced water treatment system according to claim 2, characterized in that when the same functional unit includes multiple levels of units connected in series, the water outlet of each level of unit is sampled separately. 5. The evaluation method of oilfield produced water treatment system according to claim 4, characterized in that in step 4, the weight of each level of the unit is the weight of such unit divided by the number of unit levels. 6. The evaluation method of the oilfield produced water treatment system according to claim 1, characterized in that, in step 5, the overall operating effect evaluation standard of the produced water treatment system is: setting the following unit and system efficiency changes based on empirical values Intervention threshold. When the operating efficiency of the test unit or system is lower than the intervention threshold, intervention measures will be taken. 7. The evaluation method of oilfield produced water treatment system according to claim 6, characterized in that, in step 5, the intervention measure is to shorten the period of regular water sample testing to half of the original period. When two consecutive tests are performed, When the following situations occur η≥5 indicates that the overall system is running well and the unit is running well; X _i ≥5, indicating that the unit system is running well and sampling is normal and regular; When -10＜X _i ＜5, encrypted sampling, and _the result of When the X _i index is <-10, measures are taken directly against the unit where it is located. 8. The evaluation method of oilfield produced water treatment system according to claim 2, characterized in that in step 6, the evaluation standard for determining the current on-site dosing effect of the settlement unit according to the value of Y _i is: Y _i ≤ 10, if Carry out agent evaluation, screening and replacement, and once again determine whether the existing agent matches the water body; when Y _i ≥ 30, the agent matches the on-site process conditions. When 10 < Y _i < 30, increase the dosage of settlement agent by 5% to 10%. 9. The evaluation method of oilfield produced water treatment system according to claim 2, characterized in that, in the second step, each water sample is separately packaged in a different glass test tube before testing, and the water sample in the glass test tube is Introduce nitrogen or inert gas respectively to eliminate the air in the tube.