| Due to the complex geological conditions and strong heterogeneity of shale oil reservoir of the lower Es3 of the Shahejie Formation of the Paleogene System in Zhanhua sag, Jiyang depression, Bohai Bay Basin, a comprehensive study on shale oil reservoir microscopic reservoir space characteristics and occurrence characteristics of liquid hydrocarbon has important significance for the following choice of development mode and design of development plan.According to X-ray diffraction data, minerals of shale oil reservoir of the lower Es3 in Zhanhua sag are mainly clay minerals, carbonate minerals and terrigenous clastic, with a small amount of pyrite. Lithology are mainly for the calcareous mudstone, argillaceous limestone and mud bearing limestone, with a small amount of limestone and limy dolomite and so on.Through field emission scanning electron microscopy?SEM? and argon ion polishing-scanning electron microscopy observation, the microscopic reservoir space of shale oil reservoir of the lower Es3 is identified in Zhanhua sag. The microscopic reservoir space is divided into two major categories of micro pore and micro fracture.The micropores can be further subdivided into intergranular pore, intercrystal pore,dissolution pore and intracrystalline pore. Intergranular pore mainly includes the pore between argillaceous debris, and the pore between argillaceous debris and terrigenous clastic, and pore diameter mainly distributed in 60?800 nm. Intercrystal pore is mainly for intercrystal pore of calcite, dolomite and pyrite, and pore diameter mainly distributed in 200?1200 nm. Dissolution pore mainly consists of intergranular dissolution pore, dissolution pore inside granule and dissolution micro-pore, and aperture distribution is more scattered. Intracrystalline pore refers to intracrystalline pore of calcite and clay minerals, and most of the intracrystalline pores are smaller than 80 nm. The micro fracture includes abnormal pressure fracture, interlaminar micro fracture and shrinkage fracture of rock. Micro fracture mainly distributed in100?800 nm, and some micro fractures are greater than 1 ?m.Based on qualitative observation and quantitative analysis of argon ion polishing-scanning electron microscopy, the study was made on the characteristics ofshale oil microscopic reservoir space. The main reservoir space types of calcareous mudstone are intergranular pore, dissolution pore and micro fracture. Reservoir space types of argillaceous limestone are mainly intergranular pore, micro fracture and intracrystalline pore. Mud bearing limestone reservoir space types are mainly dissolution pore, intergranular pore and intercrystal pore. Limestone reservoir space types are mainly intracrystalline pore and dissolution pore. The main reservoir space types of limy dolomite are intercrystal pore and dissolution pore. The storage capacity of limy dolomite is best, followed by calcareous mudstone, argillaceous limestone and mud bearing limestone. The storage capacity of limestone is the least.Based on the nitrogen adsorption experiments, a study was made on the microscopic reservoir space characteristics of the shale oil in the range of the mesopore?2?50nm?. The microscopic pore of shale oil reservoir is more development.When the aperture in the mesoporous range, the rock with high shale content has good storage capacity. Pore diameter mainly distributed in 3?8 nm, and the 2?10 nm pore is the main reservoir space. By fractal dimension analysis, shale oil reservoir has higher pore complexity, strong heterogeneity and rough surface.Through the stress sensitivity experiments, the shale oil reservoir of the lower Es3 has strong stress sensitivity. Pore compression coefficient is?0.07?2.44? × 10-2MPa-1. The stress sensitive coefficient is?64.65?148.62? × 10-2 MPa-1. With the increase of the net overburden pressure, the rock deformation occurred, which leads to a significant reduction of reservoir and permeability.Based on field emission scanning electron microscopy?SEM?, argon ion polishing-scanning electron microscopy and X-ray energy spectrum analysis, liquid hydrocarbon of shale oil reservoir occurred in intergranular pore, intercrystal pore,dissolution pore and micro fracture. Oil-containing pore types of argillaceous limestone are mainly intergranular pore and micro fracture. Oil-containing pore type of mud bearing limestone is mainly dissolution pore. Oil-containing pore types of limestone are mainly dissolution pore and micro fracture. Oil-containing pore types of limy dolomite are dissolution pore and intercrystal pore. The oily containing of limy dolomite is best. The mud bearing limestone and argillaceous limestone are worse in turn. The limestone is the worst. |
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