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Evaluation method of environmental protection performance of drilling mud

2022-05-28

Drilling fluid testing is an extremely complex underground oil well detection technology, which is composed of a mixed multiphase system composed of a variety of inorganic and organic substances. In the past, people did not pay enough attention to environmental protection, so that in the process of mixing mud, they often only focus on drilling. process performance, while ignoring or seldom considering the potential pollution and toxicity hazards of drilling fluid raw materials and additives to the environment, making drilling operations a major source of pollution in the process of oilfield and geological exploration and development. Due to people's increasing attention to environmental protection issues, and The environmental protection and safety issues related to drilling fluids make the research and development of high-efficiency, low-cost and non-toxic drilling fluids an important direction of development. And the question of how to evaluate the environmental protection performance of drilling mud is raised. This paper combines the environmental protection of drilling fluids at home and abroad. A brief introduction to the evaluation method of performance, i.e. toxicity, is given.

 

Drilling fluid testing

 

1. 96h biological identification test of drilling fluid

 

To evaluate the environmental performance of drilling fluids and their wastes, the American Petroleum Institute (API) developed a 96-hour biological identification test for drilling fluids. In this method, mysid shrimp seedlings were used as the standard test organisms in liquid and suspension phases, and hard-shelled mussels and chrysanthemums were used as solid-phase test organisms. The procedure is as follows: add 9 parts of seawater to 1 part of drilling fluid or additives to dilute, then vigorously stir for 30 min and settle for 60 min. The liquid phase was filtered through a 0.45 um membrane, and the suspension phase was directly cultured for 96 h. The hard-shelled mussels and oysters were put into the solid phase and stored for 10 days to observe their growth and death. Among them, the 96 h LC50 test is to dilute the liquid phase and the suspension phase to different concentrations and put them in several plates, and then put 20 robust mysids in each plate at the age of 4 to 6 days, and observe the mysids in each plate after 96 hours. The LC50 value of this chemical agent is the concentration at which half of the deaths occur, and its unit is ppm (parts per million). The LC50 value indicates the degree of harm of the chemical agent to the environment, that is, the smaller the LC50 value, the greater the toxicity of the drilling fluid. However, some foreign experts believe that this method is not accurate, and it is not convenient to use in practice. Its disadvantages are specifically:

 

(1) The detection time during contact culture has been as long as 96 hours. In addition, professional laboratories are often far away from the drilling operation site, and the detection preparation process and methods are very cumbersome and time-consuming, resulting in the actual test period often as long as 2 to 3 weeks;

 

(2) The test process is quite complicated and requires experienced biological experts to complete;

 

(3) Due to the influence of various factors such as the source, variety, seawater quality and suspension phase preparation method of mys shrimp, the toxicity test results of different laboratories will vary greatly.

 

Combining with the actual biological population, based on the relevant test procedures of API, the 2-3 age larvae of Chinese prawns were selected as the test organisms, and then the test organisms were developed to use Mystis nirvana as the test organisms. Daqing Oilfield used juvenile carp and Chinese rice shrimp for acute toxicity test of drilling fluid.

 

2. Microtoxicity test

 

This method is also called luminescent bacteria method, using luminescent bacteria as the test species (standard strain). The principle is to judge the intensity of bioluminescence emitted by luminescent elements such as ATP, luciferin and luciferase in living cells of luminescent bacteria. This luminescence process is a metabolic process in the bacteria and a sign of the bacteria's health. If the bacterial activity is high and the cells are actively dividing, the intracellular ATP content is high, and the bacterial luminescence is strong; if the bacterial activity is inhibited or dormant, the intracellular ATP content decreases significantly, and the luminescence is weak; when the bacteria die, ATP will immediately Disappear. Glow stops. When different types and concentrations of chemical agents are added, the light intensity of the bioluminescent bioluminescent light changes due to bacterial health damage. It weakens or even disappears - thus reducing the degree of harm of chemical agents to the environment.

 

The method is as follows: add 9 parts of seawater to 1 part of cobalt well fluid or additive, and after 30 min of intensive cooling, the ingot is sunk for 60 min, and then it is divided into three layers of liquid phase, floating phase and interphase. Dilute to different concentrations, and insert a certain amount of random bacteria respectively. After 15 min, the effect of chemical agents on the light intensity of luminescent bacteria was determined by using the Lingai Xianximeter (Biotoxicity Tester). When there is no strong weakening of 50 ? (relative to 3.NaC solution), the concentration is the ECO value (PEM) of the drilling fluid s-series or additive. The detection time of this method (about 2h) is shorter than that of the mys shrimp test, and the method and steps are relatively simple, which can be easily carried. It can be activated by filtration, and it is not necessary to temporarily cultivate the two before detection. Although this method has many advantages, the correlation between the detection results and the mysis method is not very good. The detection data are often: too small. .

 

The detection time of this method (about 2h) is shorter than that of the mys shrimp test, and the method and steps are relatively simple, which can be carried on the palm. It can be activated by filtration, and it is not necessary to temporarily cultivate the two before detection. Although this method has many advantages, the correlation between the detection results and the mysis method is not very good. The detection data are often: too small . 3 The Illumination Method

 

3. Niuwuji Li luminescence method

 

The principle of this method is the same as that of the bacteria method. It is based on the effect of bamboo substances on the natural luminescent bamboo of Xianshi bio-luminescence, but the types and test methods of the tested organisms are different. The test organisms of this Wan method are from Shenying. One. Because the algae is a nanite, it is very easy to grow, and the road maintenance and use are fast. It is beneficial to on-site application. This kind of algae only has the characteristics of light when the water environment in which the algae lives is stirred and luminous. . This luminescence phenomenon is called "bioluminescence". Commonly known as "phosphorescence". When toxic substances exist, the normal physiological and biochemical reactions of luminous algae will be disturbed or destroyed, and the luminous emblem will decrease or even disappear completely. The greater the cumulative flux of algae, the less toxic the drilling fluid is: on the contrary, the greater the toxicity of the drilling fluid. This species of algae is added to artificially prepared seawater and mixed with certain vitamins, minerals and PH aids. In the resulting medium - at 2 plus 0 °C, light for 12 days per day (another 12h, put it in the most dry room), and cultivate it to make its concentration in the culture medium reach 200D/mL. . Dilute 3 mml. of the culture solution to 100/ml and divide it into 3 parts, put them into 3 20 mL transparent glass bottles, and add 10.25 and 50 pL of the test sample respectively. The glass plate is placed in a dark room, and the toxic substances interact with the fine country at this time. After 4h, the culture medium was vigorously stirred for 1 min in the dark room. The shearing action would stimulate the algae luminescence, and the cumulative luminescence curve could be measured by the bioluminescence test.

 

The method has high sensitivity and strong anti-interference ability, and is manifested in the following aspects;

 

(1) The detection can be performed without interference in the case of high turbidity and chromaticity, which is an advantage that the mys shrimp method and the luminescent bacteria method cannot prepare.

 

(2) The method is not disturbed by KO. (3) Toxic substances with a concentration of less than a few milligrams per opening can be accurately detected with high sensitivity. In addition, it also has a short detection time

 

(4) h. The advantages of low detection cost and easy counting.

 

(3) It can also accurately detect toxic substances with a concentration of less than a few milligrams per opening, and the sensitivity is high. In addition, it also has a short detection time (4h). It has the advantages of low detection cost and easy counting.

 

4. Leaching toxicity test

 

The leaching toxicity test is a representative sample of solid waste. The specified leaching procedures and test methods are used to determine the concentration of leaching pollutants. If the concentration of leaching pollutants is equal to or exceeds the national pollution control standards, the solid waste is That is, it has leaching toxicity. Reference [12] used this method to determine the toxicity of chromium in waste drilling fluids. In the experiment, distilled water (pH value 5.8 ~ 6.3) was used as the extracting agent, the liquid-solid ratio was 20:1, and the extraction time was 18 h, 0.45 μm by vertical oscillation (110 ± 10 times-min-') at room temperature. The microporous membrane separates the solid-liquid two phases. The leaching toxicity test method is also applicable to the identification of migratory inorganic pollutants in the drilling waste mud.

 

5. Genotoxicity test

 

For drilling fluid, only evaluating its impact on the environment from the results of the acute toxicity test cannot fully and correctly reflect its toxicity. There may be genotoxic substances discharged into the environment with the drilling fluid, which may be indirectly affected by the environmental medium. Population health. Genotoxicity causes pollutants to cause mutations in the genetic information of biological cells. This changed genetic information or genetic material can be passed on to daughter cells during cell division and reproduction, making it new hereditary. Through the genotoxicity test It can predict the potential degree of carcinogenicity. Micronucleus is one of the manifestations of chromosomal aberrations, which is the result of DNA damage to the genetic material. Exogenous contaminants at the peak of cell division in the root tip of faba bean block the healing of chromosomal breaks, and micronuclei The percentage per thousand (mcn%o) increased significantly. The correlation between micronucleus percentage and chromosomal aberrations is very significant. Therefore, micronucleus testing technology can replace the analysis of chromosomal aberrations to detect the intensity of genotoxicity of a substance, that is, the degree of influence of the substance on biological heredity.

 

6. Conclusion

 

To sum up, the vegetable gum flushing fluid can also meet the performance requirements of modern drilling fluid testing, and it is a new drilling flushing fluid system that can meet the needs of high-quality coring in loose and broken formations. If it can be used in geotechnical engineering The promotion and application in the survey will definitely bring better social and economic benefits.