Research On Detection And Control Technology Of Characteristic Pollutants In Shale Gas Field

The impact of shale gas field mining on atmospheric environment and climate change cannot be ignored.The production stage is mostly accompanied by the escape of methane.The high-strength greenhouse gas methane has a heating capacity 25 times that of carbon dioxide;this paper uses LDAR and bag detection methods to detect the sealing points(flanges,connectors,open pipelines,valves,etc.)After testing,it is concluded that the leakage is the most serious in flanges,open pipelines,etc.;the discharge rate of LDAR is 3-5 orders of magnitude higher than the discharge rate calculated by the bag method.Extensive use of oil-based mud has caused serious environmental pollution problems,and it is difficult to dispose of oil-based cuttings.Shale gas fields are mostly located in remote mountainous areas,with large environmental capacity,relatively scattered,and less pollution during the exploration process,which is not the focus of this thesis.During the drilling stage,oil-based mud was used for all three-way drilling.The oil-based cuttings emissions were155.14m3,and the oil-based mud emissions were 310.21m3.Generally,the oil-base cuttings of a shale gas well does not exceed 500 cubic meters,about 1,300 tons per well.After the oil-base cuttings reach the ground,it is more difficult to deal with,and it is also prone to surface seepage,polluting groundwater,and bringing environmental risks.In this paper,oil-based cuttings and mud from two shale gas fields are collected to analyze their ion concentration.As a reference and comparison,water-based mud and cuttings are also collected.The water content and oil content of oil-based mud are higher than those of water-based mud.The p H value of oil-based mud is alkaline.There is no significant change in mercury and arsenic concentration,indicating that the formation does not contribute mercury and arsenic.The high water consumption has caused particularly serious problems of water resources and water environment pollution.In the production stage,horizontal well staged fracturing technology is often used to increase natural gas production.The water consumption of each well is about30,000 m3,and the flowback fluid can reach 16%-38%.The composition of the fracturing flowback fluid is complex and the treatment is extremely difficult.;To seize the local fresh water resources,have a great impact on agriculture and industry.Because of its fracturing fluid composition and formation composition,the detection factors of this paper are determined as COD,anionic surfactants,chloride ions and other heavy metals,etc.23 items,measured by standard detection methods;high COD value,high salinity,high acidity characteristics;Chloride ions are on the rise as a whole.The fracturing fluid contains hydrochloric acid,which opens the formation oil and gas channels,and the salt concentration continues to increase;the total dissolved solids in the fracturing fluid shows an upward trend in the first six months,and then begins to decline.The liquid gradually decreased after six months,and continued to flow back to the ground,and the concentration value decreased.With the increase of years,the content of COD in the flowback fluid is continuously decreasing,and the content of fracturing fluid thickener(guar gum)is more,and the guar gum will be degraded due to formation microorganisms or high temperature conditions;the main component of the crosslinking agent is boron The acid salt,mainly present in guar gum,will flow back continuously with the residue of guar gum,and the concentration value will continue to decrease.