Effect Evaluation And Mechanism Analysis Of Imbibition In Extra-low-permeability And Tight Oil Reservoirs

At present,extra-low-permeability and tight oil reservoirs development mainly adopts horizontal well fracturing and water injection to increase energy to improve the development effect.However,due to the characteristics of low matrix permeability,small pore throat and poor connectivity of reservoir rocks,there are many problems in the process of development and production,such as large formation energy consumption,unable to be effectively supplemented,rapid production decline and low recovery degree,which seriously affect the development effect of oil field.In order to improve the development effect of extra-low-permeability and tight oil reservoirs,under the theoretical guidance of physical chemistry,polymer material science and reservoir engineering,taking chemical analysis,instrument detection and physical simulation as technical means,and taking the core and fluid of tight reservoir in Dagang Oilfield as the research object,this paper carried out the evaluation of energy enhanced imbibition oil recovery effect and action mechanism of tight reservoir.The main achievements and understandings:(1)based on the modification of epoxy resin,a hydrophilic core making method is established.The core wetting angle is 51.782°,which is close to 50.957°of the natural core of the target reservoir;(2)Among the primary 10 surfactants,BHS,DWS,SPQJ,CW-2 and PO-FASD have good solubility and stability,and PO-FASD has strong anti adsorption ability.After the rock core is soaked in surfactant PO-FASD solution(0.3%),the hydrophilicity is enhanced and the decrease of contact angle is more than 40°;(3)Static imbibition oil recovery data show that with the increase of surfactant concentration,the increase of po-fasd imbibition recovery rate shows a trend of"first increase and then decrease".When the concentration is 0.20%,the increase of recovery rate reaches the maximum value of17.65%.With the increase of core matrix length,the core imbibition rate decreases,the time for imbibition to reach equilibrium prolongs,and the static imbibition recovery decreases.With the increase of core permeability,the static imbibition recovery increases gradually,but the increase decreases gradually;(4)The dynamic imbibition oil recovery data show that with the increase of displacement rate,the imbibition oil recovery first increases and then decreases,and there is an optimal injection rate.Hydrophilic cores have higher oil recovery by imbibition,followed by neutral,followed by lipophilic.With the decrease of oil saturation in the core,the capillary force decreases gradually,the oil-water replacement ability between rock and fracture decreases,and the imbibition recovery decreases;(5)The data of enhanced energy imbibition production show that with the increase of enhanced energy injection pressure,the increase of imbibition liquid injection slug size,the extension of pressure holding time and the increase of huff and puff cycle times,the imbibition recovery rate increases,but the increase decreases gradually.Recommended process parameters of energy increasing imbibition:the size of injection slug is 0.1PV?0.3PV,the pressure holding time is more than 96h,the number of huff and puff rounds is about 3,and the injection pressure is close to the reservoir fracture pressure;(6)Compared with water,the signal amplitude of core T₂ spectrum curve is further reduced after the action of po-fasd surfactant,indicating that the oil production degree of core large and small pores has been significantly improved.Compared with macropores,the degree of oil production in small pores and its contribution to the total production are higher.Compared with water,po-fasd surfactant can not only change the wettability of rock and enhance the role of oil-water infiltration and displacement,but also reduce the interfacial tension between oil and water and reduce the adhesion resistance between crude oil and rock.The role of gravity and displacement force is enhanced,and the production degree of macroporous crude oil is significantly improved.