Study On Imbibition Oil Recovery In Tight Oil Reservoir In Daqing Oilfield Periphery Area And Analysis Of Practical Application Effect

Tight oil reserve is very rich in periphery area of Daqing Oilfield,but these oil resources can't be develop effectively.Because the permeability and porosity of reserve is too low,the reservoir entry fluid volume and production fluid volume can't meet the need of normal development.In recent years,the development degree of tight oil reserve has got improved for the application of ‘fractured network' fracturing technology.However,with the lengthening of production time in fractured well,the reserve energy consumption can not be supplied timely,thus leading to production decrease and lower recovery.The rock of tight oil reserve is often water-wet,so how to keep the reserve pressure and combine the imbibition oil recovery and ‘fractured network' fracturing technology has received much attention from petroleum technology works.In order to confirm the feasibility of above technical route,this paper conducted researches on water-wet artificial core making,selection of imbibition agent,evaluation of imbibition agent reservoir applicability,influencing factors of imbibition effect,optimization of injection parameter and analysis of field practice.All the works has done by means of chemical analysis,physical simulation and numerical simulation,guided by colloidal surface chemistry,physical chemistry and reservoir engineering,taking the interfacial tension(IFT),wettability and recovery as the index,based on the reservoir characteristics of Daqing tight oil reservoir(M8 area and P333 area).The study results show that,(1)changing the characteristics of epoxy resin can change the wettability of artificial core,the wettability of artificial core changes with the change of ratio of modified epoxy resin and common epoxy resin.(2)Compared with pure water,surfactant solution can improve effectively the imbibition recovery.As for M8 area,the imbibition effect of ‘ZWB' surfactant solution(3000mg/L)prepared by sewage is well,and the imbibition effect of ‘DWS' surfactant solution(2000mg/L)prepared by clean water is well.As for P333 area,the imbibition effect of ‘DWS' surfactant solution(3000mg/L)is well,and the imbibition recovery is higher.(3)Surfactant solution can not only alter the wettability of rock surface,but also can reduce the IFT at the same time.When we choose surfactant for imbibition oil recovery,we should think about the influence of IFT on capillary and displacement efficiency at the same time instead of pursuing ultra-low IFT.(4)Compared with the common surfactant imbibition solution,composition of ‘surfactant +cleanup additive' has the function of reducing oil viscosity,supplying reserve energy,and imbibition displacement and so on,which can insure good imbibition recovery and lifting effect.(5)Crack parameters can affect imbibition recovery in fracture-network crack core.With the increase of length of main crack and branch crack,imbibition area increases,the oil-water percolation between imbibition solution and matrix get strengthen,imbibition recovery increases,but the increase amplification decreases.(6)Imbibition effect and related influencing factors was studied through CMG software,the order of injection parameters affecting imbibition effect was also confirmed:(1)M38-S64 well,injection volume > cycle of huff and puff > soaking time > injection velocity;(2)MJ36-S631 well,injection volume > injection velocity> cycle of huff and puff > soaking time;(3)150-392 well,injection volume > injection velocity > production velocity > soaking time;(4)PF154-372 well,injection volume > soaking time > injection velocity > production velocity;(5)PF156-372 well,soaking time > injection volume > production velocity > injection velocity;(6)PF158-372 well,injection volume > injection velocity > soaking time > production velocity.On above base,injection parameters was optimized.When the oil price is 2800 yuan /t,the predicted ratio of ‘output/input' of imbibition construction is more than 3.(7)The water well can be converted into an imbibition oil well if these condition exist,such as perforated oil layer is larger,reservoir characteristics is well and bad connectivity with surrounding wells.As for the water well has above features,such as Zhao 166-38 well and Zhao 170-38 well in Zhao 166-38 area,constructing side drilling technology through high pressure water jet before injecting water is helpful to increase the seepage area,thus improving the imbibition oil recovery.The reasons of bad effect in three wells using imbibition construction in M8 area as follows,effective pressure holding is not be established after well shut down,mobility of fluid in reservoir rock pore gets weaker,production differential pressure can not meet the actual requirement,and oil saturation in pore is lower.(8)Imbibition oil recovery is an effective technology to develop tight oil reservoir,but there are some differences between field effect and predicted effect influenced by reservoir rock characteristics,‘fractured network' fracturing technology,imbibition solution reservoir applicability and injection parameters.So,there are still some works to do about mechanism of ‘fractured network' fracturing technology and imbibition oil recovery.