Study On ASP Flooding Method In Fissured Sandstone Reservoir Of Block Zhong 38 Of Fuyu Oilfield

Fuyu oilfield is a typical heterogeneous sandstone reservoir in China,which has the characteristics of shallow buried depth,low formation temperature,presence of artificial and natural fractures,as well as preferential flow channels and so on.After more than 40 years' development by water flooding,the water cut has reached more than 94%.Relying on conventional water flooding technology,the EOR potential is limited.Therefore,the study of tertiary EOR technology is imperative.Block Zhong 38 is located at the high structural point of the Bajiazi in Fuyu oilfield.There is a near north-south fault on both sides of the East and West,and the block is relatively independent.It is a typical block of Fuyu oilfield.This thesis takes abovementioned block as the research object,and carries out research on ASP flooding methods.The results can be popularized in similar reservoirs,and therefore has important theoretical significance for achieving long-term and stable production in Fuyu oilfield.By combining indoor physical simulation,numerical simulation and theoretical analysis,the thesis carries out a further understanding of reservoir,fractures and remaining oil.In this way,a profile control system and ASP flooding system suitable for shallow,low temperature and fractured heterogeneous sandstone reservoirs are developed and selected.Further more,the injection mode of ASP flooding system is optimized.The following results and recognitions have been achieved.1.By means of core observation and casting section analysis,the shape and distribution of fractures in the early and recent water flooding stages in Fuyu oilfield are described.The fracture of sand group?,?and ? is obvious.After a long-term water injection and stimulation treatments,the fracture density increased from 0.55 meters/strip to 1.04 meters/strip,and the maximum fracture width reaches 2.5 mm from 0.8mm.2.By using methods such as reservoir description,water flooded layer recognition and numerical simulation,the distribution rules of macroscopic remaining oil in Zhong 38 is analyzed,and three types of macroscopic remaining oil were characterized.Among them,the remaining geologic reserves controlled by the rhythm,by the microfacies and by the interface layer are accounting for 15.8%,27.0% and 23.1% of the total reserves respectively.The microscopic remaining oil was studied by using cast sheet and pore characteristics graphing,and it is found that at present,there are mainly four types of residual oil such as throat,cant,cluster and particle adsorption.3.The well pattern for Fuyu and Yangdachengzi reservoirs has bee optimized and designed.The formation of Fuyu and Yangdachengzi wells subdivision of the three sets of well patterns,namely water injection wells in Fuyu reservoir are divided into two sets of well patterns,production wells is still using one well pattern developed,in which I and II Group sand injection wells is divided into a set of wells,and water injection wells in Division III IV sand group is another set of wells,two sets of wells is 200 m * 200 m five spotpatterns.For Fuyu reservoir,the well pattern is 200m×200m five-point;For Yang Dachengzi reservoir the well pattern is five-point where the well spacing is 100 m,the row spacing is 80 m.The water injection section has been optimized for 53 injection wells,the constraint K-means clustering method is used for water injection section division.After adjustment of water flooding pattern and injection,the recovery rate of water flooding is increased by 1.53 percentage points.4.A new type of retarded crosslinking interpenetrating network gel was developed by adding inhibitors in the interpenetrating network crosslinking agent.The gelling time can be extended for 3 hours and meet the demand of low viscosity injection and deep migration.Based on the selection of the profile control system of slow-expansion particle,a tailored profile control system is designed according to different types of preferential flow path: the crack-type reservoir adopts slow-expansion particle + medium strength gel system;the fracture-highly permeable reservoir adopts strong gel system with slow-expansion particle;the highly permeable type adopts gel system.The total amount of profile control agent is 11.85×104m3,and the average amount for single well is 4937m3.The EOR increment is predicted to be 3.1% compared to that of water flooding.5.Through indoor experiments the nonionic surfactant X-01 suitable for the low temperature environment in Block Zhong 38 has been selected.Its anti-dilution ability,salt tolerance,divalet ion tolerance and ageing stability are quite good.The maximum static adsorptive capacity is smaller than 1.0 mg/g,and the dynamic one is 0.044 mg/g.The interfacial tension of X-01 weak alkaline ASP system can reach a minimum value when the concentration of surfactant is between 0.05% and 0.3%,and the concentration of weak alkali is between 0 and 1.2%.6.The physical and numerical simulation shows the best composition of the ASP main slug is that the polymer concentration is 2000mg/L,the surfactant concentration is 0.4%,the alkali concentration is 1.0%,and the slug size is 0.40 PV.Since the Block Zhong 38 is fissured sand reservoir,a special injection mode is proposed with a combination of ASP cyclic injection and gel system.The proposed best scenario is: 4 cycles(0.1 PV main slug+0.05 PV gel)+ 0.2 PV secondary slug+0.1 PV subsequent protection slug + water flooding.The interim cumulative oil production of this scenario is 67.08×104t,the interim degree of recovery is 22.74%,and the EOR has an increasement of 17.84% with that of water flooding and 4.84 with that of pure ASP flooding.