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Global Geology

	2023 Vol.26 Issue.1 Published 2023-02-25

	1	Recent advance on study of Pleuromeia
		ZHANG Yi and SUN Ge
		Pleuromeia is an Early-Middle Triassic index lycopod plant, very significant for study of floral age, paleoecology and paleogeography. In recent years, the progresses in the study of Pleuromeia include the new taxon Pleuromeia shaolinii Zhang et Wang found from the Middle Triassic Lianjia flora in Benxi, China; and a new strobilus of Pleuromeia found from the Lower Triassic of Nevada, USA. Four species of Pleuromeia were selected by Mendelin et al. (2022) as the iconic taxa for four ages from the Lower to Middle Triassic in the world (including the Chinese species P. shaolinii), which is more significant for paleogeographic and evolutionary studies of Pleuromeia.
		Guide:
		2023 Vol. 26 (1): 1-8 [Abstract] ( 409 ) [HTML 1KB] [ PDF 2503KB] ( 4223 )

	9	Formation of South Tianshan suture and its geological significance
		LI Haodong and ZHOU Jianbo
		South Tianshan–Solonker suture, is the largest and southernmost suture within the Central Asian orogenic belt (CAOB). It records the ultimate collision between Tarim–North China cratons and Siberia craton, and is commonly interpreted as marking the eventual closure of Paleo-Asian Ocean. South Tianshan suture belongs to the western segment of the suture zone, and its evolutionary features are important for defining the formation age of the South Tianshan–Solonker suture. In this paper, the authors review the geochronological, geochemical, petrographic, and paleontological evidence within South Tianshan suture to delineate its formation era and closure characteristics, and thus further revealing the ultimate evolutionary pattern of the western segment of Paleo-Asian Ocean. This suture records strong plate collision before Late Carboniferous, forming a series of high-pressure metamorphic rocks, characterized by the presence of blue schist, eclogite and mica schist. In Permian, the whole area was under a relatively stable post-orogenic setting, with the formation of bimodal volcanic rocks, post-collisional granites, and terrestrial molasses. Sedimentary facies gradually changed from marine to either lacustrine or fluvial during this period. An Early Permian granite dike crosscuts the HP metamorphic belt, and the HP metamorphic rocks also underwent retrograde metamorphism at this time, indicating the formation of the South Tianshan suture was earlier than Permian. Hence, the western section of Paleo-Asian Ocean closed during Late Carboniferous, and Tarim Craton moved northward to collide with Kazakhstan–Yili Block, leading to the formation of the South Tianshan suture
		Guide:
		2023 Vol. 26 (1): 9-20 [Abstract] ( 440 ) [HTML 1KB] [ PDF 1742KB] ( 4415 )

	21	Research on Fe-based impregnated diamond drill bits strengthened by Nano-NbC and Nano-WC
		Ekene Matthew Egwuonwu, Uzodigwe Emmanuel Nnanwuba, CHANG Si, DUAN Longchen, NING Fulong and LIU Baochang
		In order to improve the matrix performance of impregnated diamond drill bit to better meet the drilling needs, the effects of the addition of nano-WC and nano-NbC particles on the matrix material together with the mechanical properties and microstructure of the diamond-matrix composite material of the Fe-based diamond drill bit were studied by using the method of uniform formula design, regression analysis and solution finding. An indoor drilling test was also carried out using the fabricated impregnated diamond drill bit. The results showed that after the addition of nano-NbC and nano-WC, the hardness and flexural strength of the matrix material got improved, as the flexural strength of the diamond composite material increased to 4.29%, the wear-resistance ratio increased to 8.75%, and the tighter the chemical bonding between the diamond and the matrix. This, indicates that the addition of nanoparticles has a positive significance in improving the performance of the diamond composite. The results of the drilling test showed that the mechanical drilling speed of the impregnated diamond drill bit after nanoparticle strengthening is 25.85% higher than that of the conventional drill bit, and the matrix wear was increased by 17.5%. It proves that nanoparticles can improve the drilling performance and efficiency of drill bit.
		Guide:
		2023 Vol. 26 (1): 21-30 [Abstract] ( 391 ) [HTML 1KB] [ PDF 1183KB] ( 4261 )

	31	Study on leakage recharge mechanism of confined fresh water aquifer with semi-permeable membrane in Tianjin plain area
		ZHANG Ye and WANG Hong
		The Group II fresh groundwater bearing aquifers in the eastern plain of Tianjin underwent long term exploitation. This study shows that the area with greater water-level declining is associated with more rapid stratigraphic compaction and consolidation. In the study area, the salty groundwater in the un-exploited overlying aquifers have the same dynamic characteristic of synchronization but different amplitude with the Group II aquifers, showing that they have a close relationship. Cross-sectional study indicated that surface water, salty groundwater and underlying fresh groundwater belong to an integral water resources system. The compacted clay layers have the feature of semi-permeable membrane under alkaline condition. The infiltration of surface water is driven by the differences of osmotic pressure of salty water in each layer. When the water level difference between the Group II aquifers and overlying salty aquifers is greater than osmotic water pressure difference, the salt water layer will desalinate downward and eventually, decreasing the water level of the upper aquifers, turning phreatic water amount supposed to evaporate to leakage recharge. Therefore, stopping mining groundwater in the Group II aquifer will lead to other new environmental geology disaster.
		Guide:
		2023 Vol. 26 (1): 31-39 [Abstract] ( 387 ) [HTML 1KB] [ PDF 877KB] ( 4174 )

	40	Tooth arrangement design of retractable DTH hammer bit used for drilling while casing
		ZHANG Boyao, CHEN Baoyi,YANG Da, BO Kun and CAO Pinlu
		Down-the-hole (DTH) hammer with casing while drilling (CWD) is a technology that has been proven to be able to alleviate many of the problems faced by complex formations. However, the drill bit is suffered from rapid wear, low drilling efficiency, and high energy consumption due to the unreasonable tooth arrangement and impact energy selection in drilling process, which affect the application effect of this technology. ABAQUS software was used for numerical simulation of rock breaking behavior under impact load with the single, three, and five teeth arrangement drill bit respectively, to improve the application effect and solve the aforementioned technical problems. Based on the calculated parameters of tooth arrangement, we designed a novel drill bit for hard rocks and provided a theoretical basis for the tooth arrangement of largediameter drill bits.
		Guide:
		2023 Vol. 26 (1): 40-46 [Abstract] ( 389 ) [HTML 1KB] [ PDF 946KB] ( 4273 )

	47	Reliability analysis of retractable drill bit with air reverse circulation used for drilling while casing
		WANG Minqi, YIN Qilei,CHEN Baoyi, QI Bo, BO Kun and CAO Pinlu
		Casing-while-drilling (CWD) with down the hole (DTH) hammer drilling technology has been widely used in unconsolidated formations, due to its advantages in protecting the borehole wall, excellent rock cuttings capacity, and fast penetration rate in hard rock. As an important component of the CWD system, the structure of the retractable drill bit needs not only to ensure to form stronger reverse circulation, but also to be expandable or retractable as needed, otherwise the drill bit cannot be lift and put down smoothly in the casing, and may lead to drilling accidents. This paper developed a new type of reverse circulation DTH hammer drill bit used for CWD drilling technology. The retractable performance of this type of drill bit is studied using ADAMS software. The results show that it is smoothly expandable and retractable as designed under the conditions of the weight of the bit (WOB) of 0.5–2.0 t and the rotation speed of 30–60 r/min. To investigate the reverse circulation effect of the drill bit, Fluent software was used to simulate the flow characteristic inside it. The simulation results indicated that it can form strong reverse circulation, and the entrainment ratio h can reach 9.5%.
		Guide:
		2023 Vol. 26 (1): 47-56 [Abstract] ( 364 ) [HTML 1KB] [ PDF 1126KB] ( 4279 )

	57	Parameters of new three-water model based on nuclear magnetic experiment and optimization algorithm
		KANG Nan, HONG Xin,ZHANG Lihua,PAN Baozhi,TANG Lei and ZHANG Pengji
		Clastic rock reservoir is the main reservoir type in the oil and gas field. Archie formula or various conductive models developed on the basis of Archie’s formula are usually used to interpret this kind of reservoir, and the three-water model is widely used as well. However, there are many parameters in the threewater model, and some of them are difficult to determine. Most of the determination methods are based on the statistics of large amount of experimental data. In this study, the authors determine the value of the parameters of the new three-water model based on the nuclear magnetic data and the genetic optimization algorithm. The relative error between the resistivity calculated based on these parameters and the resistivity measured experimentally at 100% water content is 0.902 4. The method studied in this paper can be easily applied without much experimental data. It can provide reference for other regions to determine the parameters of the new three-water model.
		Guide:
		2023 Vol. 26 (1): 57-62 [Abstract] ( 398 ) [HTML 1KB] [ PDF 727KB] ( 4101 )

　

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