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Global Geology

	2022 Vol.25 Issue.2 Published 2022-05-25

	69	Formation mechanism of high-quality reservoirs in intermediate volcanic rocks: A case study of Longfengshan area in Songliao Basin
		XING Jian, SHAN Xuanlong, REN Xianjun, YI Jian, LIU Chaoyang and NIU Penghui
		The basin margin slope area of Changling fault depression in Songliao Basin is dominated by intermediate-basic volcanic rocks of Huoshiling Formation, and there is still a lack of in-depth understanding of the development pattern and formation mechanism of high-quality reservoirs in intermediate-basic volcanic rocks in this area. Taking the intermediate volcanic rocks in Longfengshan area of Changling fault depression as an example, a comprehensive study was undertaken via core observations, thin section porosity analysis, rock physical property tests, scanning electron microscopy and X-ray diffraction analysis, combined with well log and seismic data. As a result, formation mechanism of a high quality reservoir was made clear based on dissolution modification effects of the volcanic rocks, and the development model of the high quality reservoir under the dual control of lithology and fluid was established. The research shows that the volcanic rocks in this area consist of six lithologies: andesitic hydrothermal breccia, andesite, andesitic volcanic breccia, andesitic tuff, dacitic tuff and sedimentary tuff, which are controlled by structure, eruptive source, eruptive action and palaeotopography. The proximal facies of the volcanic edifice were located on the basin margin, distributed along faults mainly consisting of overflow facies intermixed with eruptive facies, and gradually transformed into thick eruptive facies (middle-source facies) and volcanic sedimentary facies (distal facies). The reservoir space of volcanic rocks was dominated by dissolution pores, which were formed by weathering and dissolution by organic acidic fluids. The thermal debris flow subphase in the middle-source facies of the volcanic edifice had a large amount of easily dissolved volcanic ash, which was close to the source rock in the centre of the basin and was a favourable area for the development of dissolution pores. This study is providing a guide for oil and gas exploration in the intermediate-basic volcanic rocks in the slope of Changling fault depression in Songliao Basin.
		2022 Vol. 25 (2): 69-83 [Abstract] ( 138 ) [HTML 1KB] [ PDF 7366KB] ( 616 )

	84	Microscopic pore characteristics of andesite and implication from mineral content: A case study in Huoshiling Formation of Changling fault depression, Songliao Basin
		NIU Penghui, SHAN Xuanlong, REN Xianjun,YI Jian,LIU Chaoyang and XING Jian
		In order to study the microscopic pore characteristics of andesite reservoir and the effect of mineral content on the andesite pore, this study takes the andesite of the Huoshiling Formation in Longfengshan of Changling fault depression, Songliao Basin as a subject. The andesite reservoir space was discerned through the observation of cores and casting thin sections. Besides, the pore size distribution of andesites and their mineral contents were quantitatively characterized by high-pressure mercury injection, nitrogen adsorption and XRD, respectively. The results show that: (1) There are various types of reservoir space in andesites, including vesicles, amygdule, intergranular pores, matrix dissolution pores and dissolution pores of amygdala, and three types of fractures including dissolution, structural and explosion fractures. (2) The pore size distribution of andesite is complex. The main pore size of andesite is mid-pore (10-20 nm) with some large-pores (>50 nm). Mid-pore and large-pore provide the main specific surface area, which are the main space for gas storage. (3) The andesite reservoir space in the study area is mainly controlled by dissolution, as supported by the relationship between the change of mineral content and porosity evolution. The porosity of andesites decreases with the increase of quartz and chlorite content, but increases with the increase of soluble mineral, e.g., feldspar content.
		2022 Vol. 25 (2): 84-96 [Abstract] ( 182 ) [HTML 1KB] [ PDF 3306KB] ( 623 )

	97	Prospect for strategic minerals exploration and development, investment environment and cooperation in Mozambique
		YUAN Qiyu, LI Yangchun, SONG Chongyu,SUN Renbin and ZHANG Xingang
		: Mozambique is an essential country in the Belt and Road Initiative, and it is also to cooperation between China and with Africa in energy resources. It is located in the critical node of the “East Africa Channel” and close to the “African Twin Ocean Railway”, which is an important strategic position. Mozambique has abundant mineral resources and vast reserves of advantageous minerals. The natural gas reserves of Mozambique ranked second in Africa. It also has world-- class scale graphite and rich iron, gold, copper, niobium-tantalum and other resources. In recent years, the mining industry in this country has been rising and attracting many foreign companies to invest, including international mining giants such as Vale, Rio Tinto and large mining enterprises of China. This paper systematically studies the mineral resources endowment, exploration and development situations of natural gas, graphite, titanium-zircon placer deposits, niobium-tantalum, gold, iron and other strategic minerals in Mozambique, comprehensively analyzes the mining investment environment and the current situation of exploration and development of Chinese enterprises in Mozambique, and replans four safeguard areas of strategic mineral resources in critical short supply. Mozambique generally has good prospects of mining investment and a stable foundation for cooperation with China. Chinese enterprises can focus on oil and natural gas, graphite, titanium, zirconium, niobium, tantalum, and iron, which complement the needs of China, expand the mining capacity cooperation, and improve the ability to secure strategic mineral resources supply.
		2022 Vol. 25 (2): 97-108 [Abstract] ( 207 ) [HTML 1KB] [ PDF 1013KB] ( 809 )

	109	Prediction of surface subsidence in Changchun City based on LSTM network
		WANG He and WU Qiong
		Monitoring and predicting of urban surface subsidence are important for urban disaster prevention and mitigation. In this paper, the Long Short-Term Memory (LSTM) network was used to predict the surface subsidence process of Changchun City from 2018 to 2020 based on PS-InSAR monitoring data. The results show that the prediction error of 57.89% of PS points in the LSTM network was less than 1mm with the average error of 1.8 mm and the standard deviation of 2.8 mm. The accuracy and reliability of the prediction were better than regression analysis, time series analysis and grey model.
		2022 Vol. 25 (2): 109-115 [Abstract] ( 157 ) [HTML 1KB] [ PDF 1589KB] ( 529 )

	116	Characteristics of land use conversion in soda saline-alkali soil region of central Northeast China
		ZHANG Haobin, YANG Changbao,GUO Huali and HOU Guanglei
		Since the 1970s, the soda saline-alkali soil region, which is located in the semiarid-arid region of the central Northeast China, has experienced drastic climate variability. Meanwhile, human activities and socio-economic development have led to an increase in water consumption. These factors have brought out considerable land use change and a lot of soil salinize-alkalization. The land use types were obtained from remote sensing images interpretation based on Landsat MSS in 1970s, TM, ETM in 1990s and 2010s. The characteristics of land use conversion and its response to climate change and influence of human activities were explored in the study area during 1970-2010. The results include: (1) The land use types had changed significantly, especially farmland and grassland, with annual growth rates of 0.31% and 0.35%, respectively. In terms of the saline-alkali land, the area increased greatly during 1970-1990, and its increase was mainly from grassland. There was a decrease from 1990 to 2010, and the loss of saline-alkali was replaced by farmland and grassland. (2) Climate change in the study area is obvious, showing a trend of decreasing precipitation and increasing temperature. The change of saline-alkali land area is closely related to the precipitation, with R2 = 0.78, passed a passing the 0.01 significance test. (3) The correlation of land use degree index and human activity index with saline-alkali land was not obvious, and the changes in these indices only reflected the land use patterns. Under sufficient rainfall, the saline-alkali land was developed into farmland by humans, which caused the decrease of the saline-alkali land. Therefore, climate change is the main driving force of land salinization in the study area.
		2022 Vol. 25 (2): 116-125 [Abstract] ( 148 ) [HTML 1KB] [ PDF 3191KB] ( 763 )

	126	Insights from coastline survey in Shandong Province, China
		XIU Chun, HUO Suxia, WANG Guogang,DUAN Haiqin, CHEN Shengtao and YAO Haiyan
		The coastline, as the boundary between land and sea, is shaped by both natural factors and human activities. Based on concrete practice from coastline survey in Shandong Province, this study discusses the applicability of the local standard Specification for Coastline Survey (DB 37/T 3588-2019). The coastline classification system takes into account the coastline characteristics and marine management requirements in Shandong Province. To be specific, the coastline with natural beach morphology and ecological function is involved, and its delimitation method is innovated. The coastline delimitation of sandy beach, aquaculture pond and salt pan follows the trace line of the mean high water springs (MHWS), but the coastline location of sandy beach can also be at the base of cliffs or at the foot of seawalls and roads considering the dynamic changes of the beach in different seasons and the integrity of the beach topography. The delineation of estuarial coastline is to achieve the complete coastline, and should not be used for the statistics of natural coastline retention rate. At present, the review of survey results has been completed. With the promulgation of survey results next, the formulation of relevant mechanisms and policies should promptly be put on the agenda, including regular investigation and data updating, natural coastline assessment, natural coastline requisition-compensation, and coastline protection planning.
		2022 Vol. 25 (2): 126-132 [Abstract] ( 130 ) [HTML 1KB] [ PDF 558KB] ( 360 )

　

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