Enrichment characteristics and exploration directions of deep shale gas of Ordovician-Silurian in the Sichuan Basin and its surrounding areas,China

The enrichment characteristics of deep shale gas in the Ordovician Wufeng-Silurian Longmaxi formations in the Sichuan Basin and its surrounding areas are investigated through experiments under high temperature and high pressure,including petrophysical properties analyses,triaxial stress test and isothermal adsorption of methane experiment.(1)The deep shale reservoirs drop significantly in porosity and permeability compared with shallower shale reservoirs,and contain mainly free gas.(2)With higher deviatoric stress and axial strain,the deep shale reservoirs have higher difficulty fracturing.(3)Affected by structural location and morphology,fracture characteristics,geofluid activity stages and intensity,deep shale gas reservoirs have more complicated preservation conditions.(4)To achieve the commercial development of deep shale gas reservoirs,deepening geological understanding is the basis,and exploring reservoir simulation technology befitting the geological features is the key.(5)The siliceous shale and limestone-bearing siliceous shale in the Metabolograptus persculptus-Parakidograptus acuminatus zones(LM1-LM3 graptolite zones)are the high-production intervals for deep shale gas and the most favorable landing targets for horizontal drilling.Deeps water areas such as Jiaoshiba,Wulong,Luzhou and Changning with deep shale reservoirs over 10 m thickness are the most favorable areas for deep shale gas enrichment.It is recommended to carry out exploration and development practice in deep-water shale gas areas deposited deep with burial depth no more than 5000 m where the geological structure is simple and the shale thickness in the LM1-LM3 graptolite zone is greater than 10 m.It is better to increase the lateral length of horizontal wells,and apply techniques including high intensity of perforations,large volume of proppant,far-field and near-wellbore diversions to maximize the stimulated deep reservoir volume.

New prospecting progress using information and big data of coal and oil exploration holes on sandstone-type uranium deposit in North China

1.Objective A series of Mesozoic-Cenozoic continental sedimentary basins exist in North China,coexisting with coal,oil/gas,and salt resources.Many previous drilling projects have been conducted within these basins to explore coal,petroleum,and mineral resources,however,these data have not been integrated due to different industries owners.In order to efficiently explore the large-sized,easily extracted,and environmentally friendly,sandstone-type uranium deposits,previous coal and oil exploration drilling-hole data are systematically collected, processed,and analyzed to improve the sandstone-type uranium prospecting exploitation.At the same time,we also discussed the uranium source,ore-forming process and model for the sandstone-type uranium deposits.

Upper Paleozoic Marine Shale Characteristics and Exploration Prospects in the Northwestern Guizhong Depression,South China

Multiple sets of organic-rich shales developed in the Upper Paleozoic of the northwestern Guizhong Depression in South China. However, the exploration of these shales is presently at a relatively immature stage. The Upper Paleozoic shales in the northwestern Guizhong Depression, including the Middle Devonian Luofu shale, the Nabiao shale, and the Lower Carboniferous Yanguan shale, were investigated in this study. Mineral composition analysis, organic matter analysis(including total organic carbon(TOC) content, maceral of kerogen and the vitrinite reflection(Ro)), pore characteristic analysis(including porosity and permeability, pore type identification by SEM, and pore size distribution by nitrogen sorption), methane isothermal sorption test were conducted, and the distribution and thickness of the shales were determined, Then the characteristics of the two target shales were illustrated and compared. The results show that the Upper Paleozoic shales have favorable organic matter conditions(mainly moderate to high TOC content, type Ⅰ and Ⅱ_1 kerogen and high to over maturity), good fracability potential(brittleness index(BI) > 40%), multiple pore types, stable distribution and effective thickness, and good methane sorption capacity. Therefore, the Upper Paleozoic shales in the northern Guizhong Depression have good shale gas potential and exploration prospects. Moreover, the average TOC content, average BI, thickness of the organic-rich shale(TOC > 2.0 wt%) and the shale gas resources of the Middle Devonian shales are better than those of the Lower Carboniferous shale. The Middle Devonian shales have better shale gas potential and exploration prospects than the Lower Carboniferous shales.

Prospective prediction and exploration situation of marine Mesozoic-Paleozoic oil and gas in the South Yellow Sea

The South Yellow Sea Basin is a large sedimentary basin superimposed by the Mesozoic-Paleozoic marine sedimentary basin and the Mesozoic-Cenozoic terrestrial sedimentary basin, where no oil and gas fields have been discovered after exploration for 58 years. After the failure of oil and gas exploration in terrestrial basins, the exploration target of the South Yellow Sea Basin turned to the marine Mesozoic- Paleozoic strata. After more than ten years' investigation and research, a lot of achievements have been obtained. The latest exploration obtained effective seismic reflection data of deep marine facies by the application of seismic exploration technology characterized by high coverage, abundant low-frequency components and strong energy source for the deep South Yellow Sea Basin. In addition, some wells drilled the Middle-Upper Paleozoic strata, with obvious oil and gas shows discovered in some horizons. The recent petroleum geological research on the South Yellow Sea Basin shows that the structure zoning of the marine residual basin has been redetermined, the basin structure has been defined, and 3 seismic reflection marker layers are traceable and correlatable in the residual thick Middle-Paleozoic strata below the continental Meso-Cenozoic strata in the South Yellow Sea Basin. Based on these, the seismic sequence of the marine sedimentary strata was established. According to the avaliable oil and gas exploration and research, the marine Mesozoic-Paleozoic oil and gas prospects of the South Yellow Sea were predicted as follows.(1) The South Yellow Sea Basin has the same sedimentary formation and evolution history during the sedimentary period of the Middle-Paleozoic marine basin with the Sichuan Basin.(2) There are 3 regional high-quality source rocks.(3) The carbonate and clastic reservoirs are developed in the Mesozoic- Paleozoic strata.(4) The three source-reservoir-cap assemblages are relatively intact.(5) The Laoshan Uplift is a prospect area for the Lower Paleozoic oil and gas, and the Wunansha Uplift is one for the marine Upper Paleozoic oil and gas.(6) The Gaoshi stable zone in the Laoshan Uplift is a favorable zone.(7) The marine Mesozoic-Paleozoic strata in the South Yellow Sea Basin has the geological conditions required to form large oil and gas fields, with remarkable oil and gas resources prospect. An urgent problem to be addressed now within the South Yellow Sea Basin is to drill parametric wells for the Lower Paleozoic strata as the target, to establish the complete stratigraphic sequence since the Paleozoic period, to obtain resource evaluation parameters, and to realize the strategic discovery and achieve breakthrough in oil and gas exploration understanding.

Hydrocarbon accumulation and exploration prospect of mound-shoal complexes on the platform margin of the fourth member of Sinian Dengying Formation in the east of Mianzhu-Changning intracratonic rift, Sichuan Basin, SW China

Drilling,seismic and logging data were used to evaluate the hydrocarbon accumulation conditions of the mound-shoal complexes in the platform margin of the fourth member of Sinian Dengying Formation in the east side of the Mianzhu-Changning intracratonic rift in the Sichuan Basin.The four understandings are:(1)The platform margin belt of the Deng 4 Member can be divided into three sections,northern,middle and southern;the middle section is at the core of the Gaoshiti-Moxi paleouplift and the structural high now,while the southern and northern sections are at the slope of the paleouplift and the structural lows now;the three sections have similar development characteristics and reservoir features of platform margin mound-shoal complex.(2)In the margin of the east side of the rift,there are several faults nearly perpendicular to the platform margin belt,the faults divide the platform margin belt into rugged paleo-landform,and the high part developed platform margin mound-shoal complexes and the reservoirs are good in physical properties,while the low part developed inter-beach depression and no mound-shoal complexes,where the reservoirs are poor in physical properties.(3)The six groups of faults nearly perpendicular to the platform margin belt divide the platform margin belt into seven large mound-shoal complexes which have similar hydrocarbon accumulation conditions and accumulation evolution process and are rich in petroleum.(4)The inter shoal depressions between the mound-shoal complexes are characterized by tighter lithology,which can block the updip direction of the mounds and shoals at the lower part of the slope of the paleouplift and are favorable for the later preservation of mound-shoal gas reservoirs.This has been proved by Well Jiaotan 1 and Heshen 2 drilled successfully.The mound-shoal complexes on the platform margin of the structural slope area have a good exploration prospect.

Situation and Prospectfor Petroleum Exploration of the Central Gasfield in Shaan－Gan－Ning Basin

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Situation and Development Prospect of Uranium Resources Exploration in China

History of uranium exploration and the general situation of identified uranium resources in China are introduced briefly in the paper,and the feature of uranium resources is summarized as "a large number of deposits,good ore processing properties and centralized occurrence" which should be considered as the advantages.In accordance with the fact that the exploration level of uranium resources is quite low in China,it is pointed out that exploration investment must be intensified from now on to identify more uranium concentrated bases which occurring of middle to large size uranium deposit in order to meet the demand of natural uranium from nuclear power sector.Besides,major scientific and technological achievements on uranium exploration during the past fifty years are elaborated in the paper.According to the exploration ability and uranium resources potential in China,it is believed that uranium exploration can realize the goal of "getting break through both at home and abroad" and meet the requirement of nuclear industry to uranium resources in China by carrying out the uranium resources exploration strategy of "rooted in domestic and opening up abroad".

Progress and Prospects of Oil and Gas Exploration and Development in the World

2017 has seen the recovery in the global oil and gas market.Both Brent and WTI were priced at over USD 50 per barrel.Oil companies have basically adapted to the relatively low oil price environment through a series of cost-cutting and efficiency measures,and the number of projects making final investment decisions (FID) has increased for the second consecutive year.Global annual new conventional oil and gas reserves hit new lows in 2016 and 2017.However,gratifying progress has been made in the area of unconventional oil and gas.Shale oil and gas in the US has become the biggest bright spot in the oil and gas industry in the past two years.There have also been new developments in the extraction of natural gas hydrates,which may lead to a greater role for natural gas in energy consumption.Recovery will be the main tone of the oil and gas market in 2018.

Initial Exploration of the Prospects for China's Tourist Market in 1998

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Exploration and research progress of shale gas in China

There are three types of shale gas resources in China.The resources are present in large amounts and are widely distributed.Marine facies,transitional facies and continental facies resources each account for a third.Based on resource distributions,there are many wells penetrated into the Sinian,Cambrian, Ordovieian,Silurian,Devonian,Carboniferous and Permian strata of the Yangtze plate and its periphery, the North China Craton and the Tarim Basin.Many years of exploration have indicated that the marine Silurian Longmaxi shale gas is widely distributed in south China and has been industrialized in its production in the Siehuan basin.The shale gas from the Cambrian Niutitang Formation and the Sinian Doushantuo Formation are important discoveries in Yichang,Hub ei and Zhenba,Shanxi.There are also shale gas resources found within transitional facies and continental facies in different areas in China.The "two element enrichment theory"has been summarized during the exploration process of Silurian marine shale gas in the Sichuan Basin.In addition,horizontal drilling and fracturing technologies up to 3500 m in depth have been developed.Based on the understanding of shale gas accumulation in a complex tectonic zone outside the Sichnan basin,a preliminary summary of the formation of the "converse fault syneline control reservoir"and "paleo uplift control reservoir"model has been constructed.The dominant theory of "Trinity"shale gas enrichment and the high yield of the "deep water Lu Pengxiang sedimentary facies belt, structural preservation conditions and overpressure"is summarized.Guided by the above theories.Anyel well in Guizhou and Eyangyel well in Hubei were drilled."Four storey"oil and shale "gas is found in the Permian Qixia group,the Silurian Shiniulan Formation,the Longmaxi Formation and the Ordovician Baota Formation in Anyel well.Good shale gas has been gound in the Cambrian Niutitang formation inian Doushantuo formation in Eyangye lwell.This paper aims to summarize and review the main progress,theoretical technology and problems of shale gas exploration and development in recent years in China,and predicts the future exploration and development direction for shale gas and possible exploration areas.

"Source-Diagenesis-Accumulation" enrichment and accumulation regularity of marine shale gas in southern China

After the breakthrough of shale gas exploration and development in the Ordovician Wufeng Formation (Fm.) and Silurian Longmaxi Fm. of Chongqing Jiaoshiba area,Changning-Weiyuan area,etc. in Sichuan basin,a series of discovery and breakthrough were obtained by China Geological Survey in the Cambrian Niutitang Fm. and Sinian Doushantuo Fm. shale of the areas with complicated structure outside Sichuan basin. Based on the understanding of the law of shale gas enrichment in Longmaxi Fm. in the basin,this paper puts forward three elements of the formation and enrichment of shale gas,which are the “Source”,the “Diagenesis ” and the “Accumulation ”,after deeply studying the law shale gas enrichment and accumulation in Sinian-Cambrian reservoir of the complex structure area outside the basin. The “Source”means the sedimentary environment and petrological characteristics of organic shale.The “Diagenesis ”means the basin tectonic subsidence and hydrocarbon generation and expulsion process of organic matter.The “Accumulation” means the tectonic uplift and shale gas preservation. It is proposed that the Sinian-Cambrian and Ordovician-Silurian black shale series in the middle and upper Yangtze region of southern China were both formed in the deep-water shelf environment of rift trough and foreland basin respectively.The dessert intervals were formed in the strong reduction environment under transgressive system tract.The shale lithology belongs to calcium-siliceous and charcoal-siliceous respectively. Based on the summary of structural evolution in Yangtze area,the correlation of structural burial depth with shale diagenesis and the coupling evolution of organic matter with pore structure are discussed. Combining with structural styles,the preservation conditions of shale gas are discussed. Five types of shale gas reservoir control models are further described. Two types of future exploration directions,which are reverse fault syncline and paleo-uplift margin in complex structural area outside the basin,are proposed.

Ore-forming and Exploration Models of the Baguamiao Gold Deposit,Shaanxi Province

The Baguamiao superlarge gold deposit in Shaanxi Province is one of the typical cases in China that are hosted by sedimentary rocks. Explorers and researchers have discussed the gold mineralization enrichment conditions by studying sulphur, oxygen, carbon, silicon stable isotopes and mineralizing fluid features of the Baguamiao gold deposit and proposed a hydrothermal sedimentation-magmatic reconstructing gold mineralization model featuring multi-sources of ore-forming materials and multistage mineralizations. In addition, prospecting for “Baguamiao-type” gold deposits was started in the Fengtai Basin and a great number of important prospecting targets such as Tonglinggou, Simaoling, Guoansi and Dachaigou were discovered.

Sedimentary facies characteristics and organic matter enrichment mechanism of lower Cambrian Niutitang Formation in South China

The purpose of this study was to examine the sedimentary facies characteristics of lower Cambrian Niutitang Formation(∈1n)in South China,to reveal the mechanism of organic matter enrichment,and to guide exploration of shale gas.Macro investigation and experimental analyses were used to assess the lithology in detail,total organic matter mass fraction w(TOC),mineral composition,and trace element characteristics of∈1n.The influencing factors of organic matter enrichment were discussed extensively,and a sedimentary facies mode was suggested.In the early stage of∈1n,the locations of Well E’yangye 1,Well Ciye 1,Well Changye 1,and Well Anye 1 respectively develop,platform inner sag,outer shelf,Jiangnan slope belt,and South China detention basin.In the late stage of∈1n,the sedimentary facies evolve with decreasing sea level.The study area presents a complete three-step basin in the Early Cambrian.In the early stage of∈1n,the first step is the Yangtze carbonate platform,the second step is the outer shelf and slope,and the third step is the deep-water basin.From the Yangtze carbonate platform to the deep-water basin,w(TOC)and the mass fraction of quartz gradually increase,the mass fraction of carbonate mineral decreases,and the mass fraction of clay mineral is higher in the second step.The sea level fluctuation results in a higher w(TOC)vertically in the lower∈1n shale,and the paleogeographic(provenance)conditions lead to better horizontal development of organic matter in the outer shelf,slope and detention basin.Trace elements are abundant in the lower∈1n,and w(TOC)is correlated positively with many trace elements.In the outer shelf,slope,and adjacent areas,hydrothermal activity and upwelling current bring nutrient-rich material and promote organic matter enrichment under a strong reducing condition.Deep-shelf,slope and deep-water basin are the best facies for the formation and preservation of organic matter,especially deep-water basin facies.It remains necessary to strengthen the exploration of shale gas in the deep-water basin of∈1n in central Hunan,China.

Preliminary Study of Groundwater Quality Using Hierarchical Classification Approaches for Contaminated Sites in Indigenous Communities Associated with Crude Oil Exploration Facilities in Rivers State, Nigeria

Background: Groundwater is an important source of water. Since the control and removal of pollution are expensive, it is essential to identify the possible sources of contamination and to correctly classify groundwater on the basis of its intrinsic and integrated vulnerability. Objectives: To group ground water chemical ions and heavy metals parameters into similar groups. Method: The investigation made use of standard analytical procedures. All sampling, conservation, transportation and analysis followed standard procedures described in APHA (2012). To prevent degradation of the organic substances, all obtained samples were transferred to the laboratory, while kept in an icebox. Results: Sampling records from the same area are generally assigned to the same cluster during hierarchical cluster analysis (HCA). The cluster diagram shows the grouping of the heavy metal in the study area during wet and dry seasons. It reveals that 5 distinct clusters were identified for wet season and 4 clusters were identified during dry season. Also, it reveals that 5 distinct clusters were identified for wet season and for dry season, 4 distinct clusters were identified. Conclusion: The findings of this study are significant for policymakers and agencies in terms of dealing with the issues identified to enhance sustainable livelihood practices in the oil rich Niger Delta region of Nigeria. Therefore, decision-makers should take proper initiatives to get local people aware of the endangered zones before use, as drinking water is key to good health. Similarly, multinational oil companies will find it useful in their quest for viable social corporate responsibility and remediation plans in their respective host communities. The method proved to be a useful and objective tool for environmental planning.

Natural Gas Exploration and Development in China

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Classification,metallogenesis and exploration of silver deposits in Daxing’anling of Inner Mongolia and its adjacent areas

By the end of 2020,83 silver deposits(or ore occurrences),including four super-large-scale deposits,nine large-scale deposits,33 medium-scale deposits and 37 small-scale deposits or ore occurrences,have been proved.The amount of silver metal exceeds 86000 t with average grade of 100 g/t,which makes Daxing’anling region one of the the most important silver ore belt in China.However,the metallogenic characteristics and metallogenesis need to be clarified.The silver deposits in the study area are classified into three main types,which are magmatic hydrothermal vein type,continental volcano-subvolcanic type and skarn type,respectively.The supergiant deposits include the Shuangjianzishan deposit(silver metal amount of 15214 t with average grade of 138 g/t),the Baiyinchagandongshan deposit(silver metal amount of 9446 t with average grade of 187 g/t),the Huaobaote deposit(silver metal amount of 6852 t with average grade of 170 g/t),and the Fuxingtun deposit(silver metal amount of 5240 t with average grade of 196 g/t).The silver deposits are mainly distributed in the central and south of the Daxing’anling area,and mainly formed in the Yanshanian period.The silver polymetallic deposits in the Daxinganling area are significantly controlled by regional faults and the junction zone of volcanic rock basins and their margins.The north-east trending deep faults are the most important ore-controlling structures in this area.The distribution of silver polymetallic deposits along the main faults is obvious,and the intersection area of multiple groups of faults often form important mine catchments.The Permian is the most important ore-bearing formation in this area,but some important silver polymetallic deposits occur in Mesozoic volcanic basins or pre-Mesozoic strata.The magmatic rocks related to mineralization are mainly intermediate acidic or acidic intrusions,intermediate acidic lavas,pyroclastic rocks,and small intrusions of ultra-shallow or shallow facies of the Yanshanian Period.The mineralization element combination is mainly determined by the elemental geochemical background of surrounding rocks or source layers.In addition,the type of deposit,the distance from the mineralization center,and the degree of differentiation of ore-forming rock mass are also important influence factors.The article analyzes the prospecting prospects of each silver deposit type in the study area,discusses the relationship between mineralization center and deep prospecting,and proposes that porphyry silver deposits should be paid attention to.In the prospecting and exploration of silver deposits,comprehensive evaluation and multi-target prospecting need to be strengthened because silver can coexist or be associated with a variety of metals.

东昆仑大格勒地区碱性岩-碳酸岩型铌矿勘查进展及找矿前景

铌广泛应用在冶金工业、原子能工业、航空航天工业、军事工业、电子工业、超导材料及医疗仪器等方面,是全球高度关注的关键矿产。碱性岩-碳酸岩型矿床赋存了世界上大部分的铌资源,而我国铌资源禀赋差,对外依存度大于90%。2021年青海省地质调查院在东昆仑大格勒地区发现了碱性岩-碳酸岩型铌矿,通过三年的勘查工作,圈定5条铌矿体,矿体延伸长160~1280 m,控制最大斜深800 m,矿体厚度4.3~115.7 m,Nb_(2)O_(5)平均品位0.092%~0.156%,伴生P_(2)O_(5)平均品位3.8%~5.6%。通过资源量估算,Nb_(2)O_(5)推断资源量超过10万吨,已达大型矿床规模。目前铌矿体在走向和倾向上延伸稳定,显示出良好的找矿前景。

四川盆地下寒武统筇竹寺组海相页岩气高产井突破与富集模式

多年来下寒武统筇竹寺组页岩气勘探开发进展缓慢,资201井获高产气流大大增加了该套页岩气规模商业化开发的信心,不同区域及层段富集规律差异及下一步勘探开发方向是筇竹寺组页岩开发面临的首要问题。以四川盆地57口钻井资料为基础,对多口重点井的古生物、沉积、储层等特征进行分析,详细剖析资201井的部署理论依据、筇竹寺组页岩气富集条件及下一步勘探开发方向。从地层研究入手,建立了筇竹寺组地层划分标准,明确筇竹寺组主体发育4套深水陆棚相的富有机质页岩(①至④号层段),其分布受裂陷槽发育控制,裂陷槽内厚度最大。分析了页岩储层发育特征,指出储层压力、孔隙度、含气饱和度从下向上、从裂陷槽外到内呈现增大趋势,储层超压对页岩孔隙保存起到重要作用;基于此结合保存条件等建立了“多层异相、超压保孔”的页岩气超压差异富集模式,指出远离散失通道的超压孔隙发育区(层段)是页岩气富集有利区(层段)。文章指出资201井及周边是未来筇竹寺组页岩气增储上产的主要区域,资源量为8.06×10^(12)m^(3);川西地区具有相当的开发潜力,资源量为0.72×10^(12)m^(3);川南长宁及黔北一带受石墨化及构造活动影响,以寻找远离风化壳及地表露头的超压孔隙发育区为主。