Feasibility Study And Project Design Of Heavy Oil Foam Flooding In Block Lu2

The Lu 2 test site is located on the Lükqün tectonic belt in the northern part of the Tainan Sag,Tuha Basin with its tectonic trend high in the east and low in the west.It is a reservoir with a buried depth of 2284m~2437.0m,moderate and high temperature(65?),high salinity(degree of mineralization 28913mg/L~174314mg/L)and heavy oil(viscosity of crude 500mPa·s).Block of Lu2 has two point two one square kilometer of an oil-bearing area,and oil in place of 1131×10~4t.During Water drive development,the total water cut increased by up to 12%per year,a rapid increase,and the injected water use rate was low,which resulted in a poor water-flooding development effect.In April 2016,serious injected water breakthrough(finger advance)occurred.Though the total water cut was as high as 84.93%,the recovery was only 5.81%OOIP.This study that the site still has greater development potential.For potential EOR methods suitable for such heavy oil reservoirs,foam flooding is attracting more and more attention due to its unique seepage characteristics and perfect oil displacement efficiency.The Yudong site of Lükqün oil reservoir(viscosity of crude 286 mPa·s)has implemented the program of foam displacement since April 2015.After 16 months of injecting the foaming agent into the Yudong test site,main groups of production wells saw greatly reduced water cut,and enormously increased daily output of oil.This indicated that a remarkable result of increasing oil and decreasing water was achieved.Of that,Yudong well 2-48 had rising daily output of oil from 3.03t to 12.62t,and a greatest decrease in water cut by 60%.To this end,the present paper screened the XHY-6D foam-flooding system applicable to the Lu 2 test site(viscosity of crude 500 mPa·s)through laboratory experiments,used the Waring-Blender method to evaluate the performance of the foaming agent at different concentrations,and adopted the double-tube parallel core displacement experiment to evaluate the influence of different slug size and permeability ratio on the oil displacement effect of the system.Results showed that under the condition of slug injection 0.3PV,foam flooding brought an enhanced oil recovery,10.82%,13.52%,11.52%,10.29%higher than water flooding when the permeability ratio was 2.1,4.2,7.3,10.3,respectively,which suggested that the XHY-6D foam system had a perfect oil displacement effect.Based on the laboratory experiments,the CMG numerical simulation software was used to design the foam flooding program for the test site(including optimization of main foam slug,concentration of prepad foaming agent,slug size,gas/liquid ratio,gas/liquid alternate cycle,speed of injection and recovery)and predict the effect of oil displacement;in addition,tracking simulation study was carried out and the optimized foam flooding system was obtained after further adjustment:(1)Foaming agent XHY-6D with effective concentration of 0.10%;main slug0.05PV×0.1%+0.1PV×0.05%;prepad slug 0.2%(effective)×0.007PV;the gas/liquid ratio 1.0/1.0,the alternate cycle 30d,and the injection speed being double current actual working system.The optimal program increased the recovery ratio by 9.61%OOIP,that is,oil increment 112×104t with an increase of 374t by the foaming agent.The total water cut dropped to a minimum of 65.84%.(2)Air foam flooding:foaming agent XHY-6D with effective concentration of 0.10%;main slug0.13PV×0.1%+0.27PV×0.05%;prepad slug 0.2%(effective)×0.007PV;the gas/liquid ratio 1.0/1.0 and the alternate cycle 30d.The optimized program had a higher oil recovery rate than that of water flooding by 15.39%OOIP,that is,oil increment of179×104t,with an increase of 227t by foaming agent,and the total water cut dropped to a minimum of 60.8%.