| Dolomite plays an important role in oil and gas reservoirs all over the world.Therefore,in-depth understanding of the genesis of dolomite is of great significance for the study of stratigraphy,minerals and oil and gas exploration.In the past research,there have been a variety of explanation modes about the genesis of dolomite,such as Sabha evaporation mode,osmotic reflux mode,burial regulation mode,mixed water mode,and tidal pump mode.However,the research of dolomiteminerals has always been a research hotspot and difficulty at home and abroad,especially in the synthesis of dolomite minerals at low temperature,there are still many obstacles,such as the high hydration energy of magnesium ions and the influence of sulfate ions.In recent decades,the research on the synthesis of low-temperature dolomiteminerals abroad has been continuously deepened,and the formation pattern of microbial origin dolomiteminerals has become more and more perfect.Some domestic scholars have also done a series of experimental studies on microbial synthesis of dolomite,and also achieved some achievements.However,the existing research objects are more anaerobic bacteria,and there is less research on aerobic bacteria.Combined with the above description,this article selected heterotrophic aerobic cladobacillus as the inducing bacterium,and the bacteria with the number ACCC 02632 was selected as the experimental bacteria.Select the temperature,magnesium-calcium ratio and other influencing factors that have an important effect on the formation of carbonate minerals,indoor experiments of microbial induced precipitation of dolomite under simulated normal temperature conditions.And explore the effects of different temperatureand magnesium-calcium ratio on the mechanism,precipitation rate,mineral type and other aspects of Bacillus bacilli induced precipitation of dolomite.Nutrient gravy agar medium powder was used to prepare culture solutions with different magnesium-calcium ratios.The effects of different temperatures on virgibacillus marismortui,different p H values on virgibacillus marismortui,and different ratios of magnesium and calcium on virgibacillus marismortui indica-induced dolomite precipitation were evaluated by setting different temperature experimental groups and controlling p H in the experiment.In the experiment,five sets of precipitation systems with magnesium-calcium ratios of 3,5,7,8,and 10 were set up.After an incubation period of about 15 days,the p H value,magnesium ion concentration,calcium ion concentration,and strontium ion concentration of the culture solution were measured,and collect the precipitate,optical microscope observation,XRD diffraction,scanning electron microscope observation and energy spectrum analysis were performed on the precipitate.In this way,the effects of different temperatures on virgibacillus marismortuiand different magnesium to calcium ratios onvirgibacillus marismortui induced dolomite precipitation were analyzed.After experiments and data processing analysis,the following conclusions are mainly drawn:At 25°C,the stable p H value of the control solution was about 4,and at 30°C,the stable p H value of the control solution was about 3.This is caused by the difference in the amount of metabolites of virgibacillus marismortui and its ability to precipitate carbonate minerals.Therefore,in the 30? experimental system,virgibacillus marismortui can promote the precipitation of carbonate minerals stronger.In the experimental system at the same temperature,compare the consumption of calcium ion,magnesium ion and strontium ion in the solution under different magnesium-calcium ratio conditions.When the ratio of magnesium to calcium is 3,the total ion consumption is about 200mg/L,when the ratio of magnesium to calcium is 5,the total ion consumption is about 300mg/L,andwhen the ratio of magnesium to calcium is 7,the total ion consumption is about 360mg/L.When the ratio of magnesium to calcium is 8,the total ion consumption is about 340 mg/L,and when the ratio of magnesium to calcium is 10,the total ion consumption is about 300 mg/L.It can be found that the precipitation ability of virgibacillus marismortui on carbonate minerals will first increase and then decrease with the increase of the magnesium to calcium ratio.compare the consumption rate of magnesium ion,calcium ion and strontium ion under different magnesium-calcium ratio conditions in the experimental system at the same temperature.When the ratio of magnesium to calcium is 3,the ion consumption rate is about 15mg/L/day,when the ratio of magnesium to calcium is 5,the ion consumption rate is about 20mg/L/day,and when the ratio of magnesium to calcium is 7,the ion consumption rate is about 25mg/L/day.When the calcium ratio is 8,the ion consumption rate is about 22 mg/L/day,and when the magnesium to calcium ratio is 10,the ion consumption rate is about 20 mg/L/day.It can be found that the rate of promoting the precipitation of carbonate minerals by virgibacillus marismortui will increase first and then decrease with the increase of the ratio of magnesium to calcium.Finally,it can be seen by X-ray diffraction,electron microscopy scanning and energy spectrum analysis of the experimental precipitate,under the condition of low magnesium to calcium ratio,carbonate minerals are mostly spherical and hemispherical in shape,and smaller minerals are in the form of bacteria;under the condition of high magnesium to calcium ratio,the minerals are mostly irregular blocks or regular mineral shapes cannot be observed.under the condition of low magnesium to calcium ratio,the magnesium to calcium ratio in minerals is closer to 1:1,and the mineral structure is also closer to dolomite;under the condition of high magnesium-to-calcium ratio,carbonate minerals are mostly calcium carbonate monohydrate,and the magnesium-to-calcium ratio in mineral precipitation is closer to 2:1.Among them,dolomite minerals are most likely to be generated under the conditions of 30°C and a ratio of magnesium to calcium of 3. |
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