Research On Shale Reservior Characteristics And Sweet Spot Prediction Of Jurassic Lianggaoshan Formation In Yilong-Pingchang Area, Sichuan Basin

Through core observation,organic geochemical analysis,logging data interpretation and other means,combined with argon ion polishing scanning electron microscope observation,X-ray diffraction,nitrogen adsorption,nuclear magnetic resonance and other unconventional reservoir testing techniques,the shale oil and gas reservoir characteristics of Jurassic Lianggaoshan Formation in Yilong-Pingchang area,northeastern Sichuan Basin were analyzed,and then the shale accumulation conditions and oil and gas enrichment rules were studied,and finally the evaluation and prediction of plane favorable areas were completed.Yilong-Pingchang area is located in the east of the center of the northern Sichuan low belt.The Lianggaoshan Formation in the study area has developed a complete set of lake transgression-lake regression sedimentary cycles,and the main stratum is semi-deep lake-deep lake sedimentary black shale.Combined with the previous stratigraphic division scheme and based on the cyclic characteristics,the Lianggaoshan Formation in the study area is divided from bottom to top into the fifth,fourth,third,second and first members of the Lianggaoshan Formation.The lithology of the Lianggaoshan Formation in the study area is comple:X mostly fine sandstone and shale interbeds.The sedimentary facies transition from the shore lake subfacies to the deep lake subfacies from the west to the east of the study area;the northeast accepts the source supply,and the proportion of stratigraphic sandstone is higher than that of other regions.Lianggaoshan Formation has a high abundance of organic matter,mainly ofⅡ₁andⅡ₂types.The average R_Oof 1.28%belongs to the shale of medium-high maturity and is in the peak stage of oil generation.Lianggaoshan Formation has a good exploration potential.The micro-pore structure of shale is mainly mesoporous（2nm-50nm）,and the pore types are mainly inorganic pore,intergranular pore and intergranular pore.Shale pore development is mainly controlled by mineral composition,burial depth and organic matter,which is mostly enriched in inorganic pores and bedding fractures.The Liangshan Formation shale in the study area has a high content of brittle minerals.Through rock mechanics and brittle mineral analysis,it is found that the regional shale has a good brittleness condition and has a good mining potential.According to the measured data,the logging interpretation model is established,and the shale content,porosity,total organic carbon,free hydrocarbon content and rock mechanics parameters（Poisson’s ratio,Young’s modulus,brittleness index）and other sweet spots evaluation calculation models of Lianggaoshan Formation in Yilong-Pingchang area are established.The plane distribution characteristics of each parameter of Lianggaoshan Formation are described in detail,and the evaluation criteria of shale oil and gas favorable areas are formulated.Finally,three favorable areas of Class I are selected,among which the Longgang area in the middle of the study area and the Yingshan area in the south are the preferred areas for exploration and development,and the fourth member of Liangshi is the optimal layer in the whole region.