Geological characteristics of the southern segment of the Late Sinian–Early Cambrian Deyang-Anyue rift trough in Sichuan Basin, SW China

Based on the latest drilling, seismic and field outcrop data, the geological characteristics(e.g. strata, development and sedimentary evolution) of the southern segment of the Late Sinian–Early Cambrian Deyang–Anyue rift trough in the Sichuan Basin are analyzed. First, the strata in the southern segment are complete. The first to second members of Dengying Formation(Deng 1 + Deng 2) are found with relatively stable thickness(400–550 m), and the third to fourth members(Deng 3+ Deng 4) show great thickness difference between the marginal trough and the inner trough, which is up to 250 m. The Cambrian Maidiping Formation and Qiongzhusi Formation in southern Sichuan Basin are relatively thin, with the thickness changing greatly and frequently. Second, the Deyang–Anyue rift trough extended southward during the Deng 4 period, affecting southern Sichuan Basin. Compared to the middle and northern segments of the rift trough, the southern segment is generally wide, gentle and shallow, with multiple steps, and alternating uplifts and sags, which are distributed in finger shape. Third, the Deng 1 + Deng 2 in southern Sichuan Basin records the dominance of carbonate platform and unobvious sedimentary differentiation, and the Deng 4 exhibits obvious sedimentary differentiation, namely, basin–slope–secondary slope–slope–secondary slope–platform margin–restricted platform, from the inner trough to the marginal trough. Fourth, the rift trough in southern Sichuan Basin has evolved in four stages: stabilization of Deng 1–Deng 2, initialization of Deng 3–Deng 4, filling of Maidiping–Qiongzhusi, and extinction of Canglangpu Formation.

Prediction of geological characteristics from shield operational parameters by integrating grid search and K-fold cross validation into stacking classification algorithm

This study presents a framework for predicting geological characteristics based on integrating a stacking classification algorithm(SCA) with a grid search(GS) and K-fold cross validation(K-CV). The SCA includes two learner layers: a primary learner’s layer and meta-classifier layer. The accuracy of the SCA can be improved by using the GS and K-CV. The GS was developed to match the hyper-parameters and optimise complicated problems. The K-CV is commonly applied to changing the validation set in a training set. In general, a GS is usually combined with K-CV to produce a corresponding evaluation index and select the best hyper-parameters. The torque penetration index(TPI) and field penetration index(FPI) are proposed based on shield parameters to express the geological characteristics. The elbow method(EM) and silhouette coefficient(Si) are employed to determine the types of geological characteristics(K) in a Kmeans++ algorithm. A case study on mixed ground in Guangzhou is adopted to validate the applicability of the developed model. The results show that with the developed framework, the four selected parameters, i.e. thrust, advance rate, cutterhead rotation speed and cutterhead torque, can be used to effectively predict the corresponding geological characteristics.

Geological characteristics and the origin of ore-forming materials of(Laozhaiwan gold deposit, Yunnan Province

"Golden triangle"area bordered on Yunnan-Guizhou-Guangxi was one of the most important Carlin-type gold deposits concentration areas.Deep understanding of Carlin-type gold deposits in Guizhou and Guangxi Province had reached through several decades studies,but geological environment was very complex in the southeastern Yunnan,and Carlin-type gold deposits produced in the southeastern Yunnan were different from that of America,few studies were taken there.Based on a large number of field work,studies on the geological characteristics combining with geochemistry characteristics were taken,and analysis the genesis of Laozhaiwan gold deposit.The types of alteration in Laozhaiwan gold deposit were mainly silicification and pyritization,and Gold grade was high when silicification and pyritization were both occurred.It could be caculated that fluid density(g/cm3)varied from 0.7 to 4.9,salinity varied from 0.76%to 0.95%and ore-forming pressure(Pa)varied from 1.81×105 to 49.96×105 according to fluid inclusion test results,showed that Laozhaiwan gold deposit was hypabyssal hydrothermal deposit in low temperature and low salinity.According to composition of fluid inclusion analysis,combining with H-O isotope,made theδD-δ18O figure,showed that the fluid of the deposit rooted in formation water and mixed with meteoric waters later.

Geological Characteristics and Its Metallogenesis of Daolundaba Copper Polymetallic Deposits,Inner Mongolia

1 Geology Daolundaba copper polymetallic deposit occurs in West Ujimqin Banner,the Xilin Gol League of Inner Mongolia,along the west side of South part of Daxinganling ore belt,whose tectonic position just lies at the junction of Siberian Block in the south part,North China Block in the north and Songliao block in the east.The Daolundaba copper polymetallic deposit is hosted by the Lower Proterozoic Baoyintu group of biotite-plagioclase gneiss(Pt1by),upper Permian Linxi formation of sandy slate(P2l),and the Hercynian Qianjinchang pluton of biotite granite.

Geological and geochemical characteristics of Middle Jurassic granites in Bengbu uplift, Southeast of North China craton

1 Introduction The early formation and evolution of the North China craton has been widely concerned by scientists.The Bengbu uplift belt is located in the southeast of the craton,theresearch degree of the belt is relatively low and received increasing attention from many scholars in recent years.Through the author’s practical work and combined

Geochemical characteristics and geological significance of picritic rocks in Permian Tiaohu Formation from Santanghu Basin, Xinjiang, NW China

1 Introduction Santanghu Basin is located between the Armantai and Karamaili suture zone,at the junction of the Siberia,Kazakhstan and Tarim plates(Chen and Jahn,2004;Xiao et al.,2008).As an important part of the Central

Heterogeneous geological conditions and differential enrichment of medium and high maturity continental shale oil in China

Based on the comparison of basic geological conditions and enrichment characteristics of shale oil plays, the heterogeneity of source and reservoir conditions and differential enrichment of medium-high maturity continental shale oil plays in China have been confirmed.(1) Compared with the homogeneous geological settings and wide distribution of marine shale oil strata in North America, the continental medium and high maturity shale oil plays in China are significantly different in geological conditions generally;continental multi-cyclic tectonic evolution forms multiple types of lake basins in multi-stages, providing sites for large-scale development of continental shale oil, and giving rise to large scale high-quality source rocks, multiple types of reservoirs, and diverse source-reservoir combinations with significant heterogeneity.(2) The differences in sedimentary water environments lead to the heterogeneity in lithology, lithofacies, and organic material types of source rocks;the differences in material source supply and sedimentary facies belt result in reservoirs of different lithologies, including argillaceous and transition rocks, and tight siltstone, and complex source-reservoir combination types.(3) The heterogeneity of the source rock controls the differentiation of hydrocarbon generation and expulsion, the diverse reservoir types make reservoir performance different and the source-reservoir configurations complex, and these two factors ultimately make the shale oil enrichment patterns different. Among them, the hydrocarbon generation and expulsion capacity of high-quality source rocks affect the degree of shale oil enrichment. Freshwater hydrocarbon source rocks with TOC larger than 2.5% and saline hydrocarbon source rocks with TOC of 2% to 10% have a high content of retained hydrocarbons and are favorable.(4) High-abundance organic shale is the basis for the enrichment of shale oil inside the source. In addition to being retained in shale, liquid hydrocarbons migrate along laminae, diagenetic fractures, and thin sandy layers, and then accumulate in laminae of argillaceous siltstone, siltstone, and argillaceous dolomite, and dolomitic siltstone suites, etc. with low organic matter abundance in the shale strata, resulting in differences in enrichment pattern.

Evaluation technology and practice of continental shale oil development in China

This paper analyzes the differences in geological and development characteristics between continental shale oil in China and marine shale oil in North America, reviews the evaluation methods and technological progress of the continental shale oil development in China, and points out the existing problems and development directions of the continental shale oil development. The research progress of development evaluation technologies such as favorable lithofacies identification, reservoir characterization, mobility evaluation, fracability evaluation, productivity evaluation and geological-mathematical modeling integration are introduced. The efficient exploration and development of continental shale oil in China are faced with many problems, such as weak basic theoretical research, imperfect exploration and development technology system, big gap in engineering technology between China and other countries, and high development cost. Three key research issues must be studied in the future:(1) forming differentiated development technologies of continental shale oil through geological and engineering integrated research;(2) strengthening the application of big data and artificial intelligence to improve the accuracy of development evaluation;(3) tackling enhanced shale oil recovery technology and research effective development method, so as to improve the development effect and benefit.

A synthesis of iron deposits in the eastern Tianshan,NW China

The northern Xinjiang region is one of the most significant iron metallogenic provinces in China.Iron deposits are found mainly within three regions:the Altay,western Tianshan,and eastern Tianshan orogenic belts.Previous studies have elaborated on the genesis of Fe deposits in the Altay orogenic belt and western Tianshan.However,the geological characteristics and mineralization history of iron deposits in the eastern Tianshan are still poorly understood.In this paper I describe the geological characteristics of iron deposits in the eastern Tianshan,and discuss their genetic types as well as metallogenic-tectonic settings,Iron deposits are preferentially distributed in central and southern parts of the eastern Tianshan.The known iron deposits in the eastern Tianshan show characteristics of magmatic Fe-Ti-V(e.g.,Weiya and Niumaoquan),sedimentary-metamorphic type(e.g.,Tianhu),and iron skarn(e.g.,Hongyuntan).In addition to the abovementioned iron deposits,many iron deposits in the eastern Tianshan are hosted in submarine volcanic rocks with well-developed skarn mineral assemblages.Their geological characteristics and magnetite compositions suggest that they may belong to distal skarns.SIMS zircon U-Pb analyses suggest that the Fe-Ti oxide ores from Niumaoquan and Weiya deposits were formed at 307.7±1.3 Ma and 242.7±1.9 Ma,respectively.Combined with available isotopic age data,the timing of Fe mineralization in the eastern Tianshan can be divided into four broad intervals:Early Ordovician-Early Silurian(476-438 Ma),Carboniferous(335-303 Ma),Early Permian(295-282 Ma),and Triassic(ca.243 Ma).Each of these episodes corresponds to a period of subduction,post-collision,and intraplate tectonics during the Paleozoic and Mesozoic time.

Geology and mineralization of the Dayin’gezhuang supergiant gold deposit(180 t)in the Jiaodong Peninsula,China:A review

The Dayin’gezhuang gold deposit is located in the central part of the Zhaoping Fault metallogenic belt in the Jiaodong gold province-the world’s third-largest gold metallogenic area.It is a typical successful case of prospecting at a depth of 500-2000 m in recent years,with cumulative proven gold resources exceeding 180 t.The main orebodies(No.1 and No.2 orebody)generally have a pitch direction of NNE and a plunge direction of NEE.As the ore-controlling fault,the Zhaoping Fault is a shovel-shaped stepped fault,with its dip angle presenting stepped high-to-low transitions at the elevation of -2000-0 m.The gold mineralization enrichment area is mainly distributed in the step parts where the fault plane changes from steeply to gently,forming a stepped metallogenic pattern from shallow to deep.It can be concluded from previous studies that the gold mineralization of the Dayin’gezhuang gold deposit occurred at about 120 Ma.The ore-forming fluids were H_(2)O-CO_(2)-NaCl-type hydrothermal solutions with a medium-low temperature and medium-low salinity.The H-O isotopic characteristics indicate that the fluids in the early ore-forming stage were possibly magmatic water or mantle water and that meteoric water gradually entered the ore-forming fluids in the late ore-forming stage.The S and Pb isotopes indicate that the ore-forming materials mainly originate from the lower crust and contain a small quantity of mantle-derived components.The comprehensive analysis shows that the Dayin’gezhuang gold deposit was formed by thermal uplifting-extensional tectonism.The strong crust-mantle interactions,large-scale magmatism,and the material exchange arising from the transformation from adakitic granites to arc granites and from the ancient lower crust to the juvenile lower crust during the Early Cretaceous provided abundant fluids and material sources for mineralization.Moreover,the detachment faults formed by the rapid magmatic uplift and the extensional tectonism created favorable temperature and pressure conditions and space for fluid accumulation and gold precipitation and mineralization.

Natural gas geology and exploration direction of the Cambrian Lower Canglangpu Member in central Sichuan paleo-uplift,Sichuan Basin,SW China

Based on drilling data of JT1 and CS1,outcrop profiles and seismic data,the sedimentary pattern,space configuration of source-reservoir-cap combinations and paleouplift evolution characteristics of the Cambrian Lower Canglangpu Member in the central Sichuan paleouplift have been investigated to determine the favorable exploration zones.Controlled by Deyang-Anyue rift,the Lower Canglangpu Member features differential characteristics from east to west in sedimentary framework.In the west side of the Deyang-Anyue rift,this member is composed of clastic sediments,while in the east side of the Deyang-Anyue rift,it is fresh water shelf sediments,with grain beaches occurring along edges of the depressions,shelf and lagoon.Among the beaches,the dolomitic ones are mainly distributed around the depression edge and in the north of the lagoon.The beach sediments could become high quality reservoirs under the effect of karstification.Underlying the Lower Canglangpu Member is the widespread source rock of the Qiongzhusi Formation,so oil and gas generated by the Qiongzhusi Formation source rock can directly charge into the beach reservoirs.The sandy mudstone of the Upper Canglangpu Member can serve as the caprock of the Lower Canglangpu Member reservoir.The dolomitic beaches are located at the higher part of the paleo-uplift during the main accumulation period,with good hydrocarbon accumulation elements.Blocks PT1-CS1,HT1-GT2 and east GT2 are favorable exploration zones.

Development of unconventional gas and technologies adopted in China

This study analyses the geological characteristics and development progress of unconventional gas in China,summarizes the development theories and technologies,discusses the prospects and challenges of unconventional gas development,and puts forward the future trends of development technologies.Various technologies of unconventional gas development are available in China.Shale gas development technologies include comprehensive geological evaluation,volume fracturing of cluster horizontal wells under complex stress conditions,and factory-like operation of horizontal wells in complex mountainous area et al.Tight gas development technologies include fluid identification and quantitative prediction,optimization of well patterns,multi-layer fracturing in vertical well,staged fracturing in horizontal well,and drainage gas recovery.Coalbed methane(CBM)development technologies include the prediction of medium-high-and medium-low-rank CBM enrichment areas,rate-variable hydraulic fracturing,and quantitative drainage recovery with five stages,three pressures,and four controls.For economic and effective development of unconventional gas,further efforts should be made.First,intensified studies should be conducted on high-precision prediction and fine characterization technologies of high-quality shale reservoirs in deep marine,continental,and transitional facies.Second,key theories and technologies such as fast drilling and completion of wells with long laterals as well as large-scale volume fracturing should be developed to improve well productivity.Third,new technologies such as multiple well-type development,fluid injection,and nano-flooding should be developed to enhance the recovery.Fourth,effort should be made to identify the accumulation mechanism and large-scale effective development technologies for CBM.Fifth,the application of large amounts of data and artificial intelligence in the entire process of unconventional gas development should be considered to reduce the development cost.

An overview of the geology and production of the Fuling shale gas field,Sichuan Basin,China

The Fuling shale gas field in China is the largest shale gas field as well as the largest of its type discovered in any Lower Paleozoic formation.In this study,the geology and production of the upper and lower gas layers in the Fuling shale gas field are evaluated in terms of structure,shale quality,fault,initial production,and estimated ultimate recovery(EUR).The shale in the lower gas layer of the Jiaoshiba anticline is a high-quality reservoir,where the space is dominated by organic pores in kerogen,and the gas content is high.The shale gas wells reveal relatively high initial production and EUR.However,the shale in the upper gas layer of the Jiaoshiba anticline has reservoir space mainly composed of clay mineral pores and organic pores within bitumen,and the gas content is low.In terms of structure,primary gas migration may occur in the upper gas layer,resulting in free gas accumulation in the structural high,where the development effects are generally better than those in the structural low.The lower gas layer in the Pingqiao anticline,is the main interval for shale gas accumulation and development due to the high-quality shale.Under the influence of faults,the efficiency of exploration wells emplaced on top of the anticline is much lower a compared with those in the flanks.The residual synclines close to the Sichuan Basin,including the Baima and Baitao anticlines,are characterized by more recent uplifts,larger area,greater distance from the deep and large faults,and early fracture closure.Therefore,we recommend that the shale gas exploration and development should be carried out preferentially in areas close to the center of the residual synclines,featuring relatively high-pressure coefficient and moderate burial depth.

Formation Applicability Analysis of Stimulated Reservoir Volume Fracturing and Case Analysis

Stimulated Reservoir Volume(SRV)fracturing is a key technology of unconventional oil and gas exploration and development.To gain a deeper understanding of tight sandstone reservoirs and draw on the development experience of hydraulic fracturing,the authors conduct a large number of detailed investigations of geological characteristics in the regions that have implemented SRV fracturing.Based on the data of rock mechanics parameters,insitu stress characteristics,brittleness characteristics and natural fractures,the influencing factors of SRV fracturing in tight oil reservoirs were analyzed.The results show that the SRV fracturing is suitable for geological reservoirs with the characteristics of medium to high elastic modulus,low to medium Poisson’s ratio,low stress difference,medium to high brittleness and naturally fractured reservoirs,where natural fractures have a significant impact.Region A,a tight sandstone region,has moderate elastic modulus,low Poisson’s ratio,low ground stress difference and medium brittleness,and has the feasibility of volume fracturing.The field case of the Y325 well shows that SRV fracturing technology has obvious effect on increasing production.This technology is applicable to the Region A.