Study On The Internal Structure And Stability Simulation Of Eastern Faults In The North Of Saertu Oilfield Of Daqing

The north Saertu developing area of pure oil in Daqing oilfield,which is located in the middle of the central depression area of the Songliao Basin,has now entered the developing stage of particularly high-water substance after several decades of potential tapping.As the remaining oil is highly dispersed,there are still more than half of the oil reservoirs staying underground and have not been effectively utilized.Many water-injection developing reservoirs have a high degree of recovery,a high integrated content of moisture and a low degree of recovery factor,while the new and the remaining reserviors have poor usability.The determination of the remaining oil's spatial distribution has an important guiding significance for the remaining oi tapping in the later period.To this end,we proposed this research project to finely characterize large fault spatial configurations at the depositional unit level;Using the special logging data to conduct research on the internal structure of the fault zone;Determining the width of the fault fracture zone and defining the configuraton relationships between the development well and the fault;Quantitatively evaluating the stability of fault,based on which the residual oil at the edge of the fault is analyzed and reasonable development conditons are given to explore the fine tapping potential of fault zone.In this paper,the fault stress field characteristics and influencing factors of No.87 fault of east pure oil region in the northern part of the Saertu oil field in Daqing,and the following results and understandings have been achieved.Through SEM observation and sample testing in the fracture core of the fault zone,the lithology,structure,physical properties,mechanical properties and stress distribution characteristics of the fault fracture zone were studied,and the formation mechanism of the formation fracture zone was discussed.According to the internal structure of the fault zone and its stress description,the internal strctural characteristicsof the fault zone were identified;The structural composition and permeability of the fault zone are determined by a combination of comprehensive logging,seismic,outcrop,and core observations.Features such as mechanical properties are meticulously characterized.The regional stress field of No.87 fault in the eastern part of the north Saertu pure oil field was simulated.The results indicated that the change of the water injection pressure had obvious disturbance through the rock pore pressure.Despite that the water injection pressure may rusult in the expansion or contraction of the frramework volume and the disturbance of the stress field(changes in size and direction),it may also cause local stress concentration within and near the fault zone,inducing fault activity or producing microcracks to release the stress.The internal pore pressure of No.87 fault in the eastern part of the north Saertu pure oil field was simulated.The pressure in fault zone and its internal are large,which is mainly because that the fault zone is treated as a closed state during the fluid flow which cannot go through the fault.The pressure of the fluid carried by the fluid changes in the direction of migration in the presence of fault,which results in the direction of migration changes because of the fault,and the driving pressure which is originally passing through the fault cannot be released due to the flowing fluid,then the pressure accumulates to the edge of the fault zone.The fluid will exert pressure on the interior of fault zone to increase the value.The maximum principal stress and the minimum principal stress increase with the increase of the stratum depth.In order to extact oil in the well,the water injection pressure may increase as the vertical pressure risingThe variation characteristics of flow field under fault control was studied.In the water flooding process,the fault layer interrupted the fluid flow and changed the distribution of the entire flow field.When the injection well is close to the fault zone,the fluid pressure and flow velocity at the lower part of the formation are close to the fault zone and flow along the fault zone,while the upper zone of the fault zone has a small flow velocity or the fluid is difficult to reach.The water injection volume of the water injection well increases or the water injection intensity increases.The pore pressure around the injection well increases and the flow velocity increases.The increase in production well production volume also results in a decrease in the pore pressure around the production well and an increase in the flow velocity.That is to say,the enhanced injection and production intensity directly affects the distribution of fluid pore pressure,so that the range of pore pressure amplitude changesThe residual oil distribution characteristics along the edge of the fault zone were studied.Due to the high granularity of the fault and the high heterogeneity of the pore throat,the surrounding flow is likely to form at the large channel,islands are easilyformed at the small channel,and the fluid is weak or difficult to effectively spread,making the flooding effect worse and the formation of weak washing leave more residual oil.The relationship between the fault and the sand body shows that the fault tends to be consistent with the stratum tendency,and the configuration pattern is a stretching forward fault,and the low velocity area on the upper part of the fault or the area where the fluid cannot reach is the macroscopic part of the remaining oil enrichment.