Study On Viscosity Reduction Of Heavy Oil By Endogenous Microorganisms In Reservoir

Nowadays,the output of light crude oil is declining,and the proportion of heavy crude oil in oil and gas resources is gradually increasing.Due to the high viscosity and poor fluidity,heavy oil recovery is difficult and the development cost is high,so effectively reducing the viscosity of heavy oil and improving the development efficiency of heavy oil resources is a key problem in the field of petroleum development.At present,heavy oil viscosity reduction technologies used in domestic and foreign oilfields include physical viscosity reduction,chemical viscosity reduction and microbial viscosity reduction.Due to the high energy consumption and high equipment cost of the physical viscosity reduction method,the chemical viscosity reduction method has low efficiency and easily pollutes the formation.Therefore,economical and environmentally friendly microbial viscosity reduction technology has been a hot spot in recent years.In this paper,the endogenous microbial nutrition activation system which can promote heavy oil emulsification and hydrocarbon component degradation was selected,and the nutrient metabolic pathway of bacteria in the process of heavy oil emulsification was analyzed.In this paper,five different nutrient systems were set up,and the optimal nutrient system OCN was determined by the emulsification performance of crude oil and the degradation performance of petroleum hydrocarbons:corn steep dry powder 0.15%,NaNO₃ 0.6%,NH₄Cl 0.25%,NaH₂PO₄ 0.1%,Na₂HPO₄ 0.1%.Macro-transcriptome analysis further confirmed that OCN nutrient system can promote five important basic metabolisms of microorganisms,and make the endogenous microorganisms in the reservoir produce surfactant while degrading alkanes.Therefore,this nutrition system can directionally activate oil recovery functional bacteria with both crude oil emulsification and alkane degradation.Furthermore,under the nutritional stimulation of OCN,the community structure changes of endogenous microorganisms in different reservoirs within 28 days were explored.High-throughput sequencing analysis was used to determine that Geobacillus was the dominant bacteria in the four high-temperature reservoirs,and the emulsified viscosity of heavy oil in four reservoir culture systems could be significantly reduced by emulsifying heavy oil(61.03?85.23%).Through the degradation of n-alkanes(26.307?39.58%)and aromatic hydrocarbons(28.73?67.12%),the dehydration viscosity of heavy oil is significantly reduced(23.96?43.56%).Therefore,Geobacillus in the reservoir environment can be used as oil recovery functional bacteria to improve heavy oil recovery.On this basis,Geobacillus thermodenitrificans NG80-2 isolated from the reservoir environment was studied for viscosity reduction of heavy oil and extra-heavy oil.During the cultivation of OCN nutrition system for 28 days,NG80-2 produced effective emulsifiers for emulsifying two kinds of heavy oils and heteroatomic compounds of N₁O₁,N₁O₂,N₁O₃ and N₁S₁ with strong polarity,which effectively increased the stability of emulsion and increased the contact area between strain and heavy oil.The emulsified viscosity of Liaohe heavy oil and Lukeqin heavy oil was reduced by 81.03%and 55.27%,respectively.At the same time,NG80-2 uses heavy oil as the sole carbon source to degrade 73.41%and 57.89%of n-alkanes and 58.18%and 48.96%of aromatic hydrocarbons in Liaohe heavy oil and Lukeqin heavy oil respectively,reducing the dehydration viscosity of the two kinds of heavy oil by 47.08%and 35.09%,and the molecular weight of heavy oil is effectively reduced.The two viscosity reduction methods supplement each other,common play a role to enhance heavy oil recovery.