Research On Swirling Pre-dehydration Technology Of Produced Fluid In Shengli Oilfield

With tertiary recovery period of oilfield exploitation,the water content of produced fluid increases,physical properties become more complex,and dehydration becomes more difficult.At present,the dewatering process of crude oil is characterized by high energy consumption,large dosage of reagents,poor effect and high environmental protection pressure(VOCs,oily sludge etc.).Dehydration technology development of low cost,high efficiency and closed production fluid has become an urgent technical problem and research hotspot in Oilfield Surface Engineering construction.Because of its simple structure,high separation efficiency and low operation and maintenance costs,cyclone separator is widely used in petroleum,chemical,coal,power and other industries.Aiming at the dewatering problem of produced fluid in Shengli Oilfield,this paper adopts the method of combining experimental research and numerical simulation to carry out the research of the sealing process and cyclone low temperature pre-dewatering technology.Firstly,physical parameters such as water cut,"density-temperature",rheological properties,surface tension and"viscosity-temperature"of produced fluid in Shengli Oilfield are measured and analyzed,and the initial conditions of the experimental medium are determined.Then,the four key components of the first-stage hydrocyclone are optimized by RSM+Euler coupling model based on separation efficiency.The four structures are as follows:the number of guide vanes>the angle of cone segment>the diameter of bottom pipe>the length of tail pipe>the diameter of the overflow pipe.The optimum parameters are:4 guide vanes,4 degree angles of the cone segment,10mm diameter of underflow pipe,300mm length of tail pipe and 10mm diameter of the overflow pipe.Furthermore,the pressure field,velocity field,phase volume distribution and separation performance of the optimized cyclone pre-dehydrator were studied,and the effect of operation parameters on the separation efficiency of the single-stage cyclone pre-dehydrator is investigated.Secondly,in order to maximize the dehydration rate of the cyclone pre-dewaterer and ensure that the low oil content of the cyclone pre-dewatering water can meet the need of directly entering the sewage treatment system,the optimized cyclone pre-dewaterer is designed in series with the existing sewage deoiling cyclone.Based on different working conditions,the flow field,phase holdup distribution and separation performance of the two-stage equipment are studied,and the overflow ratio and flow rate are analyzed.The optimum overflow ratio of two-stage series process are 0.31 and the optimum treatment capacity of single cyclone pre-dehydrator is 3-3.5m~3/h.Finally,a two-stage series pilot plant for pre-dehydration of produced fluid was drawn up and processed to carry out field test of pre-dehydration of produced fluid.The influence of inlet flow rate and overflow ratio on oil-water separation effect is investigated.The trend of the field test is similar to the indoor simulation results.Built on the long-term operation,the operation validation of the two-stage series process effect and the operation reliability of the device was carried out.The empirical mathematical model between operation parameters and separation efficiency is established through experimental data.The mathematical model can accurately predict the relationship between operation parameters and separation performance of two-stage series system.It provides a basis for subsequent large-scale industrial plant design and field operation.