Quantitative Characterization Of Shale Oil Content Of The Second Member Of Kongdian Formation In Cangdong Sag,Huanghua Depression

Shale spreads widely in the eastern continental basin of our country,and the exploration and development of unconventional oil and gas resources has become a hot spot.Quantitative characterization of shale oil has been one of the essential scientific questions.This paper takes the second member of Kongdian formation in Cangdong sag for example,makes an intensive study of oiliness and characteristics of shale oil based on the property of crude oil,the separation of group component,saturated hydrocarbon and aromatic hydrocarbon gas chromatography-mass spectrometry(GC-MS),isotopic of crude oil and various components,rock pyrolysis,toal organic carbon content,chloroform bitumen ?A?,gold tube experiments,geochemical analysis and logging evaluation.And make a analysis of the factors influencing the oil content of the second member of Kongdian formation.Carry on analysis to the geochemical characteristics of crude oil in the second member of Kongdian formation.Crude oil is a of medium with high viscosity and high wax content,The content of saturated hydrocarbon is over 50%,the number of carbon of N-alkanes ranges between C23 and C31,and the main peak are mainly carbon C23,part of which are C31.And it appeared single peak type.The pristine to phytane ratio ranges from 0.68 to 1.The sterane C27 and C28 is about the same and the C28 is a little lower.The abundance of Gammacerane is low generally.The hopanes parameterr appears to be ?V? type on mass-chromatograph chart of saturated hydrocarbon.Most of the values of crude oil carbon isotopes are below-31‰.The marurity of organic matter of Ek2 is low,the source rock formed in reducing environment of fresh or brackish water,the parent material mostly come from algae and a little part is from higher plants.We use pyrolysis-chromatography experiments to mend up the loss of light hydrocarbons,and get the light hydrocarbons recovery coefficient under different thermal evolution,the range of recovery coefficient is between 0.2 and 1.7.Then carry on light and heavy hydrocarbons compensation correction for S1.The results show that there is a big differcenc in the content of S1 before and after correction.,the average value of compensation for light hydrocarbon is 0.5743mg/g and the tested S1 is 1.0125mg/g,the value of compensation for light hydrocarbon is 0.56 times than the tested S1.Use oil crossover effect to characterize shale oil content of G995 well,G998 well and so on and confirm the depth range with good oil content.The depth of G996 with good oil content is 4750m~4850m,and the G998 is about 4150 m.By establishing well-logging model of total organic carbon,we get the formula calculating TOC.Use the formula to calculate the samples of G995.Compare the calculated TOC and tested TOC,showing that they have a good correlation.Use the relationship between oiliness and TOC to grade the shale of Ek2.The type of organic matter determines the amout and property of hydrocarbons.The typeof organic matter of shale in Ek2 is mainly type ? and type ?1,which possess good oiliness.The oiliness has a close relationship with the thermal mature of organic matter and the oiliness presents the trend of increase first and then decrease with Ro.Inorganic pore of Cangdong sag includes mainly develop high angle tectonic fissure and substrate pore and so on,oiliness of shale has positive correlation of effective pores.Effective shale beds of Cangdong sag doesn't develop fracture,and it's conductive to the preservation of shale oil.Cangdong sag has a certain natural pore,which forms nettd conductive system with high angle tectonic fissure,and the content of brittle mineral of shale in Ek2 is above 50%,and it's favorable for reservoir to fracture.