Research On The Technology Of Improving Development Effect Of Ultra-low Permeability Reservoir At Medium-High Water-Cut Stage

The B102 block of Huaqing Oilfield is located in the south-central Ordos Basin,which is a developing area of ultra-low permeability reservoir.After 18 years' development,this block's main productive layer,Chang-3 Reservoir,has entered the medium-high water-cut stage,and the situation of stable production in the reservoir is very severe.Therefore,it is of great significance to explore the distribution law of crack development in this block,analyze the cause of water breakthrough in high water-cut wells,and find out the distribution law of the residual oil.According to the existing geological data in this area,through the core analysis experiment,this thesis studies and analyzes the geological characteristics of Chang-3 stratum in this area,and clarifies the following fact:in the middle and later development stages,the water-washed reservoir is hydrated by clay minerals,which causes clay minerals with strong water sensitivity in the reservoir to absorb water and expand during the water injection process,and then makes the original mineral structure destroyed,changes the reservoir's physical characteristics,and exacerbates the reservoir's heterogeneity.Moreover,by making full use of dynamic monitoring data,water absorption profile,and production dynamic data,it establishes a comprehensive crack identification method of "preliminary identification-comprehensive re-identification-crack correction" to identify 21 cracks in the study area.Through the study on the oil well's water breakthrough and flood response laws,the perfection of injection and production perfection,and the polymer's displacement effect,in combination with the analysis of typical high water-cut wells,it clarifies many contradictions such as many types of water breakthrough in the reservoir with great difficulties to govern,and put forward many targeted single-well measures such as hole refilling,transfer injection,and changing the displacement agent.Except that,in combination with the study on the remaining oil's distribution law,it fully considers the main current situation that the remaining oil in the study area is relatively enriched,the present flood response are poor,and the cracks are relatively clarified,determines the basic guiding principles of well pattern infill,and puts forward countermeasures of well pattern infill so as to improve the development effect of Chang-3 Reservoir in Bai 102 Block and increase the recovery ratio.