Simultaneous Experimental Analysis of Oil Content And Molecular Composition of Shale Fractions

doi:10.21203/rs.3.rs-1218547/v1

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Simultaneous Experimental Analysis of Oil Content And Molecular Composition of Shale Fractions

https://doi.org/10.21203/rs.3.rs-1218547/v1

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The important research content and basis of exploration and development is to evaluate the reservoir property, oil bearing property, fluidity and compressibility of shale reservoir.The key of exploration and development is to evaluate the oil-bearing and fluidity of shale reservoir.In this paper, the "shale oil content and fine components synchronous experimental analysis device" is used. Five temperature ranges of 30 ℃-90 ℃, 90 ℃-150 ℃, 100 ℃- 200 ℃, 150 ℃-250 ℃ and 250 ℃-300 ℃ were adopted. The heating rate of each temperature segment was 25 ℃ / min, and the final temperature was kept constant for 5 min. The oil content of shale (pyrolysis S1) was cut into five fractions.Simultaneous determination of oil content and molecular composition of shale fractions,and the external standard method was used to evaluate the oil content and fluidity.The results show that the five fractions of shale are mainly composed of nC₁-nC₉ gas, nC₁₀-nC₁₅ gasoline, nC₁₂-nC₂₀ kerosene, nC₁₅-nC₂₂ diesel oil and nC₁₈-nC₂₆ heavy oil of the first member of Qingshangkou formation in Songliao basin.There are differences in the fractionation and oil content characteristics of samples with different maturity in different wells.The parent material, properties and quality of crude oil are reflected in shale. The higher the maturity of shale oil is, the more light components are, the larger the light / heavy ratio parameter value of (gasoline + kerosene + diesel) and heavy oil is, the better the fluidity is, and the easier to exploit effectively.

Songliao Basin

shale oil

fraction

molecular composition

simultaneous analysis

oiliness

mobility

A new round of technological revolution in the global oil and gas industry has been brought about by the breakthrough of shale oil in North America, and a worldwide upsurge of shale oil exploration has been set off(EIA,2012;Sonnenberg S A and Pramudito A,2009;ZOU Caineng et al,2013;NIE Haikuan et al,2016;NING Fangxing ,2015;ZHU Deshun,2016;LIU Bo et al,2012).The recoverable reserves of shale oil in the world can reach 4.86×10¹⁰t(Energy Information Administration,2011).Exploration and practice of shale oil exploration has been carried out in several basins in China(ZOU Caineng et al,2014; LI M W et al,2015).Industrial oil flow was obtained in Songliao Basin, Ordos Basin(YANG Hua et al,2013,2016;GAO Gang et al,2013;CUI Jingwei et al,2015), Bohai Bay Basin(BAO Youshu et al,2016;WANG Yong et al,2016;WANG Xuefei et al,2013;SHAN Yansheng et al,2016), Nanxiang basin(ZHU Jingxiu et al,2015;ZHANG Xinwen et al,2014) and Junggar basin(QIU Zhen et al,2016;ZHI Dongminga et al,2019), these positive developments show good prospects in shale oil exploration and development in China(ZOU Caineng et al,2014;LI M W et al,2015).

The important research content and basis of exploration and development is to evaluate the reservoir property, oil bearing property, fluidity and compressibility of shale reservoir.The key in exploration and development is to evaluate oil bearing property and fluidity.It is of great significance to select "desserts" in shale oil, evaluation of reserves, resources.The oil content (pyrolysis S1)(Wu Liyan et al,2012) of shale is mainly detected by Rock-Eval 6 instrument, or fine hydrocarbon components(Xiao tingrong et al,2008) are detected by gas chromatograph in mudstone, which is the main experimental method in China and abroad.However, it is difficult to realize the oil content and hydrocarbon molecular composition of shale fraction by synchronous experimental analysis.Fine evaluation is restricted in oil bearing and fluidity in shale reservoirs.

The simultaneous analysis method for shale fraction oil content and its molecular composition was kicked out in this paper.The synchronous experimental analysis device was developed and used in shale oil content and fine components.Five temperature ranges of 30 ℃-90 ℃, 90 ℃-150 ℃, 100 ℃- 200 ℃, 150 ℃-250 ℃ and 250 ℃-300 ℃ were adopted. The heating rate of each temperature segment was 25 ℃ / min, and the final temperature was kept constant for 5 min. The oil content of shale (pyrolysis S1) was cut into five fractions.Simultaneous determination of oil content and molecular composition of shale fractions,and the external standard method was used to evaluate the oil content and fluidity.In order to meet the needs of Geological Experiment Technology for shale oil exploration, and to evaluate the oil content and fluidity in shale, we use the oil content, molecular composition and light weight ratio of fractions to analyze the parameter indexes.

1.1 Experimental instruments and samples

Testing instrument:Simultaneous experimental analysis device for oil content and fine components in shale.It consists of oil content detection unit, capture and thermal release unit, fine component detection unit and synchronous analysis control unit.

Test sample:The particle size of shale is 1-3mm, and the sample weight is 50mg.

1.2 Oil content analysis conditions of shale fraction

Main analysis conditions of shale oil content : The pyrolysis furnace is set with five temperature ranges of 30℃-90℃(S_1-0), 90℃-150℃(S_1-1), 150℃-200℃(S_1-2), 200℃-250℃(S_1-3), 250℃-300℃(S_1-4),The temperature programmed rate of each temperature segment was 25 ℃ / min, and the final temperature was kept constant for 5 min.The purity of carrier gas helium is 99.999%, and the working pressure is 0.90 ~ 1.00mpa. The purity of hydrogen gas is 99.999%, and the working pressure is 0.20 ~ 0.30mpa. The working pressure of auxiliary gas air is 0.50 ~ 0.60mpa.

1.3 Hydrocarbon enrichment and thermal release conditions of shale oil fractions

Main enrichment conditions : Liquid nitrogen was used for freezing enrichment.Liquid nitrogen completely submerged the trap.The freeze concentration time was 7.4 min for S_1-0, 7.4 min for s_1-1, 7 min for S_1-2, 7 min for S_1-3 and 7 min for s_1-4.

Main conditions of heat release: The pyrolytic temperature is 300 ℃, the temperature control accuracy is 0.1 ℃, the thermal release time was 10 min.The temperature of pipelines and valves of capture and heat release unit is 300 ℃.

1.4 Conditions for molecular analysis of shale oil fractions

Main analytical conditions for molecular components of fractions : Analysis column 50m × 0.20mm × 0.5 μM.The temperature of FID detector is 320 ℃.

Gas : Hydrogen, the flow rate was 45 ml / min.

Oxidant gas: Atmosphere, the flow rate was 450 ml / min.

S_1-0: The column temperature was 35 ℃ and kept constant for 5 min. the temperature was raised to 90 ℃ at 5 ℃ / min until the components were discharged.

S_1-1: The column temperature was 35 ℃ and kept constant for 5 min. the temperature was raised to 150 ℃ at 5 ℃ / min until the components were discharged.

S_1-2: The column temperature was 35 ℃ and kept constant for 5 min. the temperature was raised to 200 ℃ at 5 ℃ / min until the components were discharged.

S_1-3:The column temperature was 35 ℃ and kept constant for 5 min. the temperature was raised to 250 ℃ at 5 ℃ / min until the components were discharged.

S_1-4: The column temperature was 35 ℃ and kept constant for 5 min. the temperature was raised to 300 ℃ at 5 ℃ / min until the components were discharged.

1.5 Qualitative and quantitative analysis of oil fraction and hydrocarbon molecular composition in shale

Qualitative analysis was carried out by standard sample, retention time and literature. Standard sample appearance method was used for quantitative analysis. The data parameters of oil content (mg / g) and hydrocarbon molecular composition of five fractions in shale can be obtained.

The oil content and molecular composition of fractions in shale were analyzed according to the following process and steps:

Fresh core samples were collected at shale oil drilling site, cryopreservation with liquid nitrogen .Or conventional shale samples were collected on site.
Turn on the carrier gas of "Synchronous experimental analysis device in oil content and fine components in shale", turn on the power switch of chemical workstation, connect air and hydrogen,setting the condition parameters of synchronous analysis.
When the experimental device reaches the set value of analysis condition parameters, weigh the reference material of mudstone for experimental analysis. Get the synchronous analysis data.
The samples weighed in step 1 were analyzed with the same experimental parameters in step 2. Get the synchronous analysis data.
Using the analysis data of step 3, the analysis data of step 4 were quantified by external method, the oil content and molecular composition analysis parameters of shale fraction were obtained.
The analysis parameters obtained in step 5 are used to evaluate the oil-bearing property and fluidity in shale.

3.1 Oil content and molecular composition of shale fractions

3.1.1 Characteristics of oil content and molecular composition of fractions from frozen shale samples in situ

Characteristics of oil content and molecular composition of frozen (liquid nitrogen) shale samples collected by coring in drilling site(Fig. 1).The oil contents of S_1-0, S_1-1, S_1-2, S_1-3 and S_1-4 fractions of 1620.43m deep shale samples from well cha21 are 1.25 mg / g, 0.44 mg / g, 0.33 mg / g, 0.31 mg / g and 0.38 mg / g, respectively.The main molecular compositions of the samples are nC₁-nC₉,nC₁-nC₁₅,nC₁₂-nC₂₀,nC₁₅-nC₂₂,nC₁₈-nC₂₆. It can be seen that the five temperature fractions are mainly gas, gasoline, kerosene, diesel oil and heavy oil(Department of organic chemistry,1984),the content of the samples was 46%, 16%, 12%, 11%, 15%,the main components are gas and gasoline.The parent material type is II₁, and the maturity Ro is 0.80%,it is in the early stage of maturity.It can be seen that this kind of sample has the highest content of gas fraction.

3.1.2 Characteristics of oil content and molecular composition of fractions from conventional shale samples

Simultaneous analysis of oil content and molecular composition of shale fractions collected by core library show that(Fig.2),the oil contents of S_1-0, S_1-1, S_1-2, S_1-3 and S_1-4 fractions of 1625.3m shale samples from well Pu53 are 0 mg / g, 0.04 mg / g, 0.17 mg / g, 0.44 mg / g and 1.42 mg / g.The main distribution of its molecular composition was not detected,nC₁₁-nC₁₅ (n-alkane degradation), nC₁₃-nC₁₇ (n-alkane degradation), nC₁₅-nC₂₀ (n-alkane degradation) and nC₁₈-nC₂₅ (n-alkane degradation) accounted for 0%, 2%, 8%, 21% and 69%.The n-alkanes of gasoline, kerosene and diesel oil were biodegraded,it is mainly composed of heavy oil and no biodegradation occurs.The type of hydrocarbon parent material is II1 and the maturity Ro is 0.83%,it is in the early mature stage of hydrocarbon expulsion.The oil contentof S_1-0, S_1-1, S_1-2, S_1-3 and S_1-4 fractions of 2135.78m shale sample in well syy2 are 0 mg / g, 0.83 mg / g, 1.19 mg / g, 0.93 mg / g and 0.66 mg / g.The main distribution of its molecular composition was not detected.The contents of nC₁₃-nC₂₀, nC₁₇-nC₂₃, nC₂₀-nC₂₆ and nC₂₃-nC₂₉ accounted for 0%, 23%, 33%, 26% and 18%.It is mainly composed of kerosene, diesel oil and gasoline.The type of hydrocarbon parent material is II1 and the maturity Ro is 1.19%,in the mature stage.The oil content of S_1-0, S_1-1, S_1-2, S_1-3 and S_1-4 fractions of 2557.36m shale samples from well Gy1 are 0.06mg/g, 0.63mg/g, 1.17mg/g, 1.27mg/g and 0.16mg/g.Its molecular composition is mainly distributed in nC₁₀-nC₁₃, nC₁₁-nC₁₆, nC₁₂-nC₁₈, nC₁₃-nC₂₁, nC₁₅-nC₂₀, and the contents were 2%, 19%, 35%, 39% and 5% respectively.It is mainly composed of diesel oil,the type of hydrocarbon parent material is type I,the maturity Ro is 1.67%, which is in the high maturity stage.It is seen that,the oil content and molecular composition of the fractions are different in different well shale samples of the first member of Qingshankou formation.It reflects the differences of shale with different parent material types and maturity.

3.2 Evaluation of oil bearing and fluidity of shale reservoir

3.2.1 Evaluation of oil bearing property of shale reservoir

The larger the oil content of shale fraction and its value, the better the oil-bearing property of reservoir,under the same analytical conditions.The oil content of shale in well cha21, Pu53, Gy 1 and syy2 is 1.33 mg / g, 2.09 mg / g, 3.29 mg / g and 3.61 mg / g.In terms of oil content, syy2 and Gy 1 are the best, Pu53 is the second, cha21 is the last (Table 1).But it should be noted that,although the oil content of well Pu53 is higher than that of well cha21, the components of gasoline, kerosene and diesel oil in the first member of Qingshankou formation in well Pu53 are biodegraded,the degradation of n-alkanes is serious, the crude oil becomes thicker and the oil quality is obviously worse.

3.2.2 Fluidity evaluation of shale reservoir

Under the same or similar reservoir physical properties, the larger the light component proportion and the smaller the heavy component proportion of shale oil, the better the reservoir crude oil fluidity.The gas fraction in the conventional shale sample is very easy to lose,therefore, we adopt (s1-1 + S1-2 + S1-3) / s1-4, that is (steam + coal + diesel) / heavy oil ratio (light weight ratio parameter),this parameter is relatively less affected by light hydrocarbon loss.We use this parameter to evaluate crude oil fluidity in shale reservoirs (Table 1).The light weight ratio of well cha21, Pu53, syy2 and Gy1 is 3.76, 0.45, 4.56 and 18.6,the order of liquidity was Gy1 > syy2 > cha21 > Pu53,their maturity Ro were 0.80%, 0.83%, 1.19% and 1.67%.Therefore, the higher the maturity, the better the fluidity of shale oil.However, the crude oil maturity RO of well Pu53 is slightly higher than that of well cha21, because of the degradation of crude oil in well Pu53, the fluidity of well Pu53 becomes worse. According to the results of exploration and test, the fracturing of cha21, syy2 and Gy1 shale can obtain industrial oil flow, so (steam + coal + diesel) / heavy oil ≥ 3 is taken as the evaluation boundary value of liquidity desserts.

The oil content S1 of the first member of Qingshankou Formation in Songliao basin is cut into 5 fractions at temperature.S_1-0 fraction is mainly nC₁-nC₉ gas component, S_1-1 fraction is mainly nC₁₀-nC₁₅ gasoline component,S_1-2 fraction is mainly nC₁₂-nC₂₀ kerosene component, S_1-3 fraction is mainly nC₁₅-nC₂₂ diesel component, S_1-4 fraction is mainly nC₁₈-nC₂₆ heavy oil component.The differences in fractionation and oil content characteristics of different wells and maturity samples reflect the parent material, property and quality of shale oil. Generally, the higher the maturity of shale oil, the more light components, the better the fluidity, and the easier to be effectively exploited, (steam + coal + diesel) / heavy oil ≥ 3 is taken as the evaluation boundary value of shale oil liquidity desserts.
There are obvious differences in oil content and molecular composition between liquid nitrogen freezing and conventional core library sampling in shale drilling of the first member of Qingshankou Formation in Songliao basin.The former has high oil content and is mainly composed of gas and gasoline. The oil content of the latter fraction is relatively low, mainly composed of gasoline, kerosene and diesel oil, while the fraction of biodegradation shale sample has low oil content and is dominated by heavy oil component.The gas components of mature and highly mature samples collected and analyzed by conventional methods were almost lost,it is more accurate to evaluate the mobility of shale oil by the parameters of diesel oil (steam + coal + diesel) / heavy oil, and the analysis and evaluation of liquid nitrogen frozen or pressure maintaining sealed coring samples in drilling site is more accurate.

Authors' information: Zhang Bowei, College of Earth Science, Northeast Petroleum University, Daqing 163318, China, Email： [email protected]

Availability of data and materials: The datasets used or analysed during the current study are available from the corresponding author on reasonable request.

Competing interests: No competing interest.

Funding: 1. National Natural Science Foundation of China Youth Science Fund Project 42002140;

2.Youth Fund Project of Northeast Petroleum University 2018QNL-23.

Authors' contributions: Zhang Bowei and Zhang Juhe wrote the main manuscript text,and Zhang Bowei prepared figures 1-2 and table 1.

Acknowledgements: First of all, I would like to extend my sincere gratitude to my supervisor, Fu Guang, for his instructive advice and useful suggestions on my thesis. I am deeply grateful of his help in the completion of this thesis.I am also deeply indebted to all the other tutors and teachers in Translation Studies for their direct and indirect help to me.Special thanks should go to my friends who have put considerable time and effort into their comments on the draft.Finally, I am indebted to my parents for their continuous support and encouragement.

Authors' information (optional): Zhang Bowei, male, born in May 1989, received a bachelor's degree from Changjiang University in 2011, a master's degree from Southwest Petroleum University in 2014 and a doctor's degree from Northeast Petroleum University in 2017. He is now a teacher of the school of Earth Sciences of Northeast Petroleum University, mainly engaged in the research of geological resources and geological engineering. Email： [email protected]

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Table 1 Characteristics of fraction content and molecular composition of shale with different maturity

Well name	Deep (m)	TOC (%)	Ro (%)	S_1-0(%, mg/g, Carbon number range )	S_1-1(%, mg/g, Carbon number range )	S_1-2(%, mg/g, Carbon number range )	S_1-3(%, mg/g, Carbon number range )	S_1-4(%, mg/g, Carbon number range )	Oil content(%, mg/g, Carbon number range )	(S_1-1+ S_1-2+ S_1-3)/ S_1-4
Cha21 (frozen)	1620.43	2.62	0.80	46,1.25, nC₁~nC₁₁	16,0.44, nC₁₀~nC₁₅	12,0.33, nC₁₂~nC₂₀	11,0.31, nC₁₅~nC₂₂	15,0.38 nC₁₈~nC₂₆	100,2.71, nC₁~nC₂₆	2.60
Cha21	1620.43	2.62	0.80	/	29,0.39, nC₁₀~nC₁₅	26,0.34, nC₁₂~nC₂₀	24,0.32, nC₁₅~nC₂₂	21,0.28, nC₁₈~nC₂₆	100,1.33, nC₁₀~nC₂₆	3.76
Pu53	1625.30	2.86	0.83	/	2,0.04, nC₁₁~nC₁₅	8,0.17, nC₁₃~nC₁₇	21,0.44, nC₁₅~nC₂₀	69,1.42, nC₁₈~nC₂₅	100,2.09, nC₁₁~nC₂₅	0.45
Syy2	2135.78	2.39	1.19	/	23,0.83, nC₁₄~nC₂₁	33,1.19, nC₁₆~nC₂₄	26,0.93, nC₁₉~nC₂₆	18,0.66, nC₂₂~nC₂₉	100,3.61, nC₁₄~nC₂₉	4.56
Gy1	2557.36	4.30	1.67	2,0.06, nC₁₀~nC₁₃	19,0.63, nC₁₁~nC₁₆	35,1.17, nC₁₂~nC₁₈	39,1.27, nC₁₃~nC₂₁	5,0.16, nC₁₅~nC₂₀	100,3.29, nC₁₀~nC₂₁	18.60
Gy1 (frozen)	2570.65	2.33	1.67	31,1.46, nC₇~nC₁₂	33,1.53, nC₁₀~nC₁₆	18,0.85, nC₁₁~nC₁₈	11,0.50, nC₁₄~nC₂₀	7,0.31, nC₁₇~nC₂₃	100,4.65, nC₇~nC₂₃	8.86

No competing interests reported.

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Simultaneous Experimental Analysis of Oil Content And Molecular Composition of Shale Fractions

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Abstract

Figures

Introduction

1. Experimental Methods

2. Experimental Process And Steps

3. Experimental Results And Discussion

4. Conclusion

Declarations

Reference

Table

Additional Declarations

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