Microscopic pore structure and seepage characteristics of Chang 3 reservoir in Chenghua area of Ordos Basin
In order to develop the low permeability reservoir in Chang 3 member in Chenghua area of Ordos Basin,by using experimental analysis such as casting thin section observation,physical property analysis,high-pressure mercury injection,and relative permeability of oil and water,the differences in micro pore structure and their impact on seepage characteristics were studied.The results show that:the reservoir in Chang 3 is dominated by feldspar sandstone,followed by lithic feldspar sandstone,and the interstitial mate-rial is dominated by iron-bearing carbonate rock and chlorite.The main development of intergranular pores and feldspar pores,face rate is low;the contact relations between particles are mainly point-line contact and line-convex contact,and the main types of larynx were lamellar and curved.According to the parame-ters of porosity,permeability,discharge-drive pressure and maximum incoming mercury saturation,the pore throat types in the study area are classified as Ⅰ,Ⅱ and Ⅲ from excellent to poor.The oil-water phase seepage characteristics of the study area are also divided into 3 types,among which type Ⅰ has a higher intersection of relative permeability curves,a higher relative permeability of the oil phase and a strong reservoir percolation capacity;typeⅢhas a lower intersection of relative permeability curves,a lower permeability of the oil phase and a relatively weak oil phase percolation capacity;and type Ⅱ is in be-tween.By integrating the wettability experiment of the self-absorption method and the seepage curves of oil and water phases,it is concluded that the reservoirs in Chenghua area are generally between weakly oleo-philic and hydrophilic.The pore structure and wettability are the main factors affecting the phase seepage characteristics,and they are positively correlated with the phase seepage characteristics.
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