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CN-121994650-A - Method for detecting concentration of surfactant in oilfield on-site produced water

CN121994650ACN 121994650 ACN121994650 ACN 121994650ACN-121994650-A

Abstract

The invention relates to a method for detecting surfactant concentration in oilfield on-site produced water, which comprises the following steps of preparing standard aqueous solutions of surfactants with different concentrations and testing interfacial tension between each standard aqueous solution and oil to obtain a relation curve between the interfacial tension and the surfactant concentration, sucking produced water from oilfield on-site produced water, filtering and impurity-removing the produced water to obtain a produced water sample to be detected, testing the interfacial tension between the produced water sample to be detected and the oil, and obtaining the surfactant concentration in the produced water sample based on the relation curve between the interfacial tension and the surfactant concentration and the interfacial tension between the produced water sample to be detected and the oil. The method of the invention does not need to determine the specific molecular structure of the surfactant, adopts an interfacial tension method to determine the concentration of the surfactant, has high efficiency, simple method and convenient operation, and is easy to use in the oilfield site or the laboratory.

Inventors

  • LI QI
  • CHENG LIJING
  • WANG XIAOYAN
  • GE HONGJIANG
  • ZHANG NAN
  • WANG HAIFENG
  • CUI DANDAN
  • ZHANG ZUFENG
  • ZHANG YANG
  • HE PIXIANG

Assignees

  • 中国石油天然气股份有限公司

Dates

Publication Date
20260508
Application Date
20241104

Claims (15)

  1. 1. The method for detecting the concentration of the surfactant in the water produced in the oilfield on-site is characterized by comprising the following steps of: 1) Preparing standard aqueous solutions of surfactants with different concentrations, and testing the interfacial tension of each standard aqueous solution and oil to obtain a relation curve between the interfacial tension and the concentration of the surfactant; 2) Sucking produced water from the oilfield on-site produced liquid, and filtering and impurity removing the produced water to obtain a produced water sample to be detected; 3) Testing the interfacial tension of the produced water sample to be tested and oil; 4) And obtaining the concentration of the surfactant in the produced water sample based on the relation curve between the interfacial tension and the surfactant concentration and the interfacial tension of the produced water sample to be detected and the oil.
  2. 2. The method for detecting surfactant concentration in oilfield produced water according to claim 1, wherein in step 1), the relationship between interfacial tension and surfactant concentration is obtained by: Preparing standard aqueous solutions of surfactants with different concentrations, testing the interfacial tension of each standard aqueous solution and oil, and drawing a change curve of the interfacial tension along with the concentration of the surfactant; And fitting to obtain a relation curve between the interfacial tension and the surfactant concentration based on the change curve of the interfacial tension along with the surfactant concentration.
  3. 3. The method for detecting the concentration of the surfactant in the oilfield produced water according to claim 2, wherein the relationship between the interfacial tension and the concentration of the surfactant is obtained by linear fitting.
  4. 4. The method for detecting the concentration of the surfactant in the oilfield produced water according to claim 3, wherein the linear fitting formula is lg (gamma) =alg (c) +B, wherein gamma is interfacial tension, mN/m, c is the concentration of the surfactant, mg/L, and A and B are constants.
  5. 5. The method for detecting the concentration of the surfactant in the oilfield produced water according to claim 1, wherein in the step 1), the standard aqueous solutions of the surfactants with different concentrations are prepared by using in-situ water injection and/or in-situ surfactant mother liquor.
  6. 6. The method for detecting the concentration of the surfactant in the oilfield produced water according to claim 5, wherein in the step 1), the standard aqueous solutions of 9 to 15 different concentrations of the surfactant are prepared.
  7. 7. The method for detecting the concentration of a surfactant in oilfield produced water according to claim 1, wherein in the step 1), the concentration of the surfactant in the standard aqueous solution is in the range of 1 to 1000mg/L.
  8. 8. The method for detecting surfactant concentration in oilfield produced water of claim 1, wherein the oil comprises white oil.
  9. 9. The method for detecting surfactant concentration in oilfield produced water of claim 1, wherein in step 2), the produced water is extracted from the produced fluid using a syringe, the syringe taking 10mL and extracting 5mL of the produced water from the produced fluid.
  10. 10. The method for detecting surfactant concentration in oilfield produced water of claim 1, wherein in step 2), the produced water is filtered and decontaminated using a needle filter.
  11. 11. The method for detecting surfactant concentration in oilfield produced water of claim 1, wherein in step 2), the produced water sample to be detected is stored for at most three days.
  12. 12. The method for detecting surfactant concentration in produced water in an oilfield on-site according to claim 1, wherein the testing device and the testing conditions for testing the interfacial tension of each standard aqueous solution and oil in step 1) are the same as the testing device and the testing conditions for testing the interfacial tension of the produced water sample and oil to be detected in step 3).
  13. 13. The method for detecting the concentration of the surfactant in the oilfield produced water in situ according to claim 12, wherein the interfacial tension is tested by using a rotary drop interfacial tensiometer at a temperature of 30-90 ℃ and a rotational speed of 5000-5500 r/min.
  14. 14. The method for detecting surfactant concentration in oilfield produced water according to claim 1, wherein in step 3), the interfacial tension between the produced water sample to be detected and the oil is repeatedly tested a plurality of times, and the interfacial tension between the produced water sample to be detected and the oil is obtained by taking an average value.
  15. 15. The method of claim 1, wherein the surfactant concentration in the produced water sample is the surfactant concentration in the produced water after shale oil surfactant huff and puff or the surfactant concentration in the produced water after reservoir surfactant flood.

Description

Method for detecting concentration of surfactant in oilfield on-site produced water Technical Field The invention relates to an oilfield chemical detection technology, belongs to the technical field of petrochemical industry, and particularly relates to a method and a system for detecting surfactant concentration in oilfield field produced water. Background Currently, many oil fields have entered the middle and late stages of exploitation, surfactant flooding/huff and puff as an enhanced oil recovery technology, and by injecting surfactant solutions into the ground, the interfacial tension of oil and water is reduced, and the wettability of a reservoir is changed, so that the oil washing efficiency and the crude oil recovery efficiency are improved. In recent years, conventional oil reservoir and heavy oil reservoir surfactant flooding/huff-and-puff tests are carried out, and shale oil surfactant huff-and-puff pilot tests are also carried out, so that a good effect is achieved. In the field test process of oil fields, surfactant concentration detection in produced water is an important means for monitoring drainage cycles. However, as most surfactants used in oil fields have complex formulas, unknown structures and components, difficult standard curve establishment during chromatographic detection, complex operation and long time consumption, and the ultraviolet spectrum rule requires the surfactants to have strong ultraviolet absorption peaks, so that the method has poor adaptability to field environments. In particular shale oil surfactant throughput is under exploration, and many detection methods and means are in industry blank. Patent document CN202111012183.5 discloses a rapid detection kit and a detection method for surfactant in edible oil, and the patent is only suitable for detecting surfactant in edible oil, and is difficult to be suitable for detecting concentration of surfactant in produced water in an oilfield site. The patent application No. cn202410046425.X discloses a method for detecting the content of a surfactant, which measures the absorbance at the maximum wavelength by using a spectrophotometer, and further obtains the concentration of the surfactant according to a standard curve, and the method has poor applicability and is difficult to be applied to a surfactant with low absorption intensity. The patent document with the patent application number of CN201510796231.2 discloses a method for detecting the concentration of components of a poly-surface binary compound oil displacement system, which is based on chemical oxygen consumption to detect the concentration of the components of a polymer and surfactant oil displacement system, and can be completed only by seven steps, has complex operation and is not suitable for detecting the concentration of an active agent in produced water in an oilfield site. Therefore, the existing detection method is difficult to meet the detection requirements of the field test of the oil field, and a detection method for accurately and rapidly detecting the concentration of the surfactant in the produced water of the oil field is urgently needed to be established so as to meet the field requirements and practical application of the oil field. Disclosure of Invention Aiming at the problems of difficult detection and poor universality of surfactant concentration in oilfield field produced water, the invention aims to provide a method for detecting the surfactant concentration in oilfield field produced water, the method can rapidly and accurately judge the concentration of the surfactant in the produced water by measuring the interfacial tension between the produced water and the oil (e.g., white oil). In order to solve the technical problems, the invention adopts the following technical scheme: according to the scheme of the invention, the method for detecting the concentration of the surfactant in the oilfield produced water comprises the following steps: 1) Preparing standard aqueous solutions of surfactants with different concentrations, and testing the interfacial tension of each standard aqueous solution and oil to obtain a relation curve between the interfacial tension and the concentration of the surfactant; 2) Sucking produced water from the oilfield on-site produced liquid, and filtering and impurity removing the produced water to obtain a produced water sample to be detected; 3) Testing the interfacial tension of the produced water sample to be tested and the oil; 4) And obtaining the concentration of the surfactant in the produced water sample based on the relation curve between the interfacial tension and the surfactant concentration and the interfacial tension of the produced water sample to be detected and the oil. In one embodiment of the invention, in step 1), the relationship between interfacial tension and surfactant concentration is obtained by: Preparing standard aqueous solutions of surfactants with different concentrations, testing t