Reservoir Evaluation Of Chang 6₃ Formation In Huaqing Oilfield

The Ordos Basin is one of the major basins for the development of tight oil in China.The Chang 63 formation in the Huaqing oilfield is an important development zone in this area.The following contradictions during the exploration and development period exist in recent years:The heterogeneity of tight standstone reservoirs is strong;the distribution relationship between oil and water is complicated;the regional distribution characteristics of the relatively high permeability of the reservoir are significantly different.Therefore,it is necessary to carry out reservoir evaluation studies in the study area.Based on the core physical property analysis,casting thin slice,X-ray,the SEM,3D CT scanning,high pressure mercury injection,onstant-speed mercury injection,nuclear magnetic resonance,oil-water relative permeability and real sandstone water-oil displacement and other experimental data,the reservoir logging evaluation studies were conducted,and qualitave and quantitative characterizations of the reservoir microscopic characteristics were carried out after clarified the characteristics of reservoir deposits,diagenesis,lithology and physical development in the study area.On the basis of the above studies,the macroscopic heterogeneity of reservoirs was comprehensively studied within the reservoirs,between layers,and in the plane.Finally,the typical sample water flooding experiments were conducted to analyze the seepage patterns of fluids in different microscopic reservoirs.And a new water drive curve suitable for the study area was deduced to provide a comprehensive reference for the final reservoir comprehensive evaluation.The main research results are as follows:(1)The lithology of Chang 63 reservoir in Huaqing oilfield is mainly feldspathic sandstone with an average porosity of 9.68 % and an average permeability of 0.33 m D.It is a typical tight sandstone reservoir.(2)The diagenesis of the reservoir of Chang 63 Formation in the Huaqing oilfield resulted in a decrease in the resolving power of the porosity logging curve to the reservoir.After the calibration of the established physical parameter regression model as a whole,the spatial quantitative description of the reservoir property was more reliable.The core analysis method determines that the lower limit of porosity of Chang 63 reservoir in Huaqing Oilfield is 5%,and the lower limit of permeability is 0.04×10-3?m2.The actual production capacity of theeasy-to-devlop reservoirs may not be as good as some of the relatively difficult reservoirs.The porosity is not the only factor controlling the oiliness.(3)The intergranular pores in Chang 63 reservoir of Huaqing oilfield accounted for 1.38%,the dissolved pores accounted for 0.92%,intergranular micropores accounted for 0.07%,and the development of micro-throat throat was one of the reasons why the target layer became dense.The size of the throat radius is one of the main factors affecting the reservoir seepage rate.The discrete evaluation must be based on the approximation of the throat radius interval.The percentage of the movable fluid porosity is mainly related to the pore size,throat radius and pore throat distribution characteristics.When the throat radius is small and the pore throat is relatively large,oil is prone to snapping.The development of inter-particle pores is an important indicator of the level of mobile fluid saturation.(4)The Chang 631 formation has the strongest heterogeneity within and between layers,and the stable development of a single interval interlayer causes the sand bodies to be disconnected in the longitudinal direction.The heterogeneity of the northeastern part of the study area is relatively weak,and the southwestern part is relatively strong.The differences in the northeast and southwestern source systems are also one of the causes of differences in planar heterogeneity.(5)The higher the reservoir quality in the study area,the more obvious the effect of water flooding,and the highest contribution to the total flooding efficiency at different stages of the water flooding efficiency.High-displacement oil efficiency in sections with low permeability is a product of rational water injection development.Microscopic pore throat structure is the most important microscopic factor that reduces the improvement of flooding efficiency.Permeability can only be used as a parameter to characterize the overall seepage capacity of the reservoir,and the new water flooding characteristic curve derived from the new relationship between oil-water phase infiltration and water saturation at high water-cut stage is fitted to the actual production data.