Pore Structure Characteristics of Taiyuan Formation Coal Measures Shale in the Yangquan Block of the Qinshui Basin

doi:10.19657/j.geoscience.1000-8527.2021.044

Abstract

Abstract:

Pore structure of shale is one of the basic factors affecting shale gas occurrence and storage. In order to study the pore structure of highly evolved marine-continental transitional facies coal measures shale and to evaluate the storage capacity of shale gas, the scanning electron microscopy, high-pressure mercury intrusion, low-temperature N₂ and CO₂ gas adsorption experimental methods were mainly adopted in this paper. The microscopic characteristics of pores and pore structures of the marine-continental transitional facies shales from the Taiyuan Formation in the Yangquan Block of the Qinshui Basin were studied, and the factors affecting the pore development of the Taiyuan Formation shale were analyzed. The research results show that the porosity of the marine-continental transitional facies coal measures shale of the Taiyuan Formation in the Yangquan Block of the Qinshui Basin ranges from 2.54% to 12.03%, with an average of 6.61%. There are developed various types of pores. The inter-granular pore, intra-granular pore, and micro-crack are common. The organic pore is not developed. The total pore volume of the Taiyuan Formation coal measures shale is between 0.025,5 mL/g and 0.054,7 mL/g (average 0.040,1 mL/g), and the total specific surface area of pore is between 12.34 m²/g and 43.38 m²/g (average 28.74 m²/g). Micropore (<2 nm) and mesopore (2 nm to 50 nm) are the main carrier of shale gas storage. Organic carbon content, maturity R_o and clay mineral content all have a positive impact on the pore development of coal measures shale.

Key words: coal measures shale, microscopic characteristics of pores, pore structure, Taiyuan Formation, Yangquan Block, the Qinshui Basin

CLC Number:

TE132.2

LI Yangyang, LI Xianqing, ZHANG Xueqing, YANG Jingwei, ZHANG Boxiang, XIAO Xianming, YU Zhenfeng. Pore Structure Characteristics of Taiyuan Formation Coal Measures Shale in the Yangquan Block of the Qinshui Basin[J]. Geoscience, 2021, 35(04): 1033-1042.

Figures/Tables 11

Fig.1 Regional structure of the Qinshui Basin and well location map of the Yangquan Block

Table 1 Basic geochemical characteristics of the Taiyuan Formation coal measures shale samples of the Yangquan Block in the Qinshui Basin

样品号	深度/m	有机碳含量 TOC/%	石英含量/%	碳酸盐矿物含量/%	黏土矿物含量/%	其他矿物含量/%	镜质体反射率R_o/%	最高峰温 T_max/℃
YQ-01	471.5	1.98	27.0	0.8	71.4	0.8	-	558
YQ-02	485.5	2.11	29.6	2.5	63.9	4.0	-	554
YQ-03	501.6	2.11	33.5	1.4	61.2	3.9	2.48	574
YQ-04	508.3	2.20	50.2	2.5	47.3	0.0	-	580
YQ-05	517.3	2.48	60.0	1.3	28.8	9.9	2.41	564
YQ-06	544.2	1.03	38.3	1.5	57.3	2.9	-	573
YQ-07	557.2	0.98	34.8	4.5	56.4	4.3	2.09	574
YQ-08	576.6	1.16	50.1	1.7	46.3	1.9	-	572
YQ-09	584.7	2.50	37.3	3.5	57.1	2.1	2.58	592
YQ-10	603.0	1.98	36.4	21.6	23.9	18.1	2.46	576
YQ-11	615.0	0.92	40.2	1.9	48.5	9.4	-	582
YQ-12	624.5	0.73	35.2	8.9	44.4	11.5	-	581
YQ-13	477.3	1.75	28.6	3.9	65.5	2.0	-	546
YQ-14	466.5	3.63	41.2	2.2	54.0	2.6	2.56	541
YQ-15	469.6	21.21	54.3	8.8	23.9	13.0	-	541

Fig.2 Scanning electron microscope image of the Taiyuan Formation coal measures shale samples of the Yangquan Block in the Qinshui Basin

Fig.3 N2 adsorption-desorption curve and CO2 adsorption-desorption curve of the Taiyuan Formation coal measures shale samples of the Yangquan Block in the Qinshui Basin

Fig.4 Distribution of pore volume and specific surface area of the Taiyuan Formation coal measures shale of the Yangquan Block in the Qinshui Basin

Fig.5 Relationship between pore volume and specific surface area of the Taiyuan Formation coal measures shale of the Yangquan Block in the Qinshui Basin

Fig.6 Pore size distribution of the Taiyuan Formation coal measures shale of the Yangquan Block in the Qinshui Basin

Fig.7 Relationship between TOC and pore volume, specific surface area and porosity of the Taiyuan Formation coal measures shale of the Yangquan Block in the Qinshui Basin

Fig.8 Relationship between maturity Ro and pore volume, specific surface area of the Taiyuan Formation coal measures shale of the Yangquan Block in the Qinshui Basin

Fig.9 Relationship between mineral component content and pore volume of the Taiyuan Formation coal measures shale of the Yangquan Block in the Qinshui Basin

Fig.10 Relationship between mineral component content and pore specific surface area of the Taiyuan Formation coal measures shale of the Yangquan Block in the Qinshui Basin

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