Study On Oil And Water Movement And Potential Exploration Of Remaining Oil In Chang2 Reservoir In M Area Of Xifeng Oilfield In Ordos Basin

The Chang 2₃ reservoir in the M area of Xifeng Oilfield in the Ordos Basin is currently in the middle and late stages of development.There are several problems in the development of the reservoir:the oil-water relationship is complicated due to the development of edge and bottom water in the eastern and northern parts of the study area,which results in the rapid increase of the water cut of the new producing wells in the east.The uneven longitudinal water absorption of the injection well and low degree of water driving are the results of the strong heterogeneity of the reservoir,causing a large quantity of remaining oil left in this area.Therefore,a three-dimensional geological model was built based on logging data,core analysis data,dynamic monitoring data,production history data,etc.On the basis of the three-dimensional geological model,the geological characteristics of the reservoir and the theory of seepage mechanism,the horizontal and vertical oil-water movement laws and its influencing factors were studied using dynamic analysis method and reservoir engineering numerical simulation,with production dynamic data as constraint and numerical simulation technology as the means.To proposing the remaining oil potential tapping measures,the qualitative-quantitative research on the remaining oil in the plane and longitudinal direction were studied combined with the development process by researching on the comprehensive oil-water movement laws and reservoir engineering numerical simulation.Through the study,it can be concluded M area is in the middle and high water-cut period?30%⁴0%?with an uneven ascend rate of water-cut on the plane.The ascend rate of water-cut on the plane is mainly affected by the development degree of the edge water,the distribution direction of the sedimentary sand body and the injection-production well pattern.The ascend speed of water-cut of M area in eastern and northern plane water are obviously affected by edge water,and the edge water flows into the reservoir,resulting in a gradual increase in the central part.The ascend speed of water-cut in other area is controlled by the direction of river sedimentary sand body distribution and well pattern.The speed of water is promoted to be faster following the direction of sedimentary sand body distribution.In the same well group,the speed of water of diagonal wells advances the speed of water line of the edge well.Due to poor reservoir physical properties,thin sand bodies,strong heterogeneity,and high kaolinite clay content in the pores in the southern and southeastern areas of the M area,the development wells in the southern and southeastern areas of the M area have lower longitudinal water absorption.The water absorption profile is multi-finger-shaped or spike-shaped water absorption.The middle region has better reservoir physical properties,thicker sand bodies,weaker reservoir heterogeneity,and less clay mineral content.The water absorption profile is mostly uniform water absorption.On the plane,the remaining oil in area M is mainly distributed in various forms such as flakes and strips in the southeastern,southwestern,middle and northern areas of M area.Among these areas,Chang 2₃¹ layer has a relatively thinner sand body and poorer physical properties in southeast.A large quantity of remaining oil remained in the southeast and southwest due to few edge water is developed in the southwestern area.Due to the development of the flood plain facies in the middle of the Chang 2₃² layer,the permeability heterogeneity of the reservoir is relatively strong which results in the formation of a large quantity of residual oil in its middle part.The uneven advancement of the edge water leads to differences in the waterflooding effect beyond the main line,resulting in the formation of a large quantity of remaining oil in the middle,northern and northeastern part.In the vertical direction,the remaining oil in zone M is mainly distributed at the bottom of the Chang 2₃¹ layer?Chang 2₃¹-K₃^Chang 2₃¹-K₅?,the top of Chang 2₃³ layer(Chang 2₃³-K₁₃^Chang 2₃¹-K₁₆).The factors affecting the distribution of remaining oil in M area mainly include:tectonic structure,sedimentary microfacies,injection-production well pattern,heterogeneity,edge-bottom water,reservoir physical properties,sand body thickness;Chang 2₃¹ layers?59.54%of remaining oil?and Chang 2₃³layers?35.76%of remaining oil?are the main layers potentially tap the remaining oil in M area.It is predicted that the final production will increase by 6.2×10⁴t,and the recovery factor will increase by 0.95%by using reasonable adjustment of development parameters,reasonable adjustment of well pattern,and technological means to tap the potential of remaining oil in M area.