Organic geochemistry and source rock potential assessment of Late Paleocene Patala Formation in Margalla Hill Range,North Pakistan

Black shales of the Paleocene Patala Formation are proven source rocks for conventional hydrocarbons in southern Potwar Basin of Pakistan and are assumed to be effective source rocks towards north in the Margalla Hill Range of Pakistan.In this regard,the current study focuses on source rock geochemistry of the Paleocene Patala Formation to assess its source rock potential,organic matter types and thermal maturity levels in the Margalla Hill Range of North Pakistan.Source rock generative potential,kerogen types and thermal maturation of the analysed rock samples were unraveled by using Rock-Eval pyrolysis T_(max),TOC(total organic carbon)and vitrinite reflectance(R_(0))analyses.TOC analysis coupled with S_(2) yield revealed poor to fair source rock quality encountered within the formation.The pyrolysis T_(max) vs Hydrogen Index(HI),showed mostly Type Ⅲ kerogen dominated by thermally immature to mature organic matter.The HI and genetic potential is low and revealed poor hydrocarbon generation potential of the formation.The S_(1) vs TOC plots confirm the indigenous nature of the hydrocarbons hosted by Patala Formation.The vitrinite reflectance outcomes indicated immature to mature source rock beds lying in dry gas zone.The HI and OI signatures and abundance of Type Ⅲ kerogen are indicating dominance of terrestrial organic matter within the formation.Overall,the investigated Patala Formation exposed at the studied section of Margalla Hill Range,Pakistan acts as a poor source rock unit for liquid hydrocarbon generation but holds prospects for dry gas generation in the study area.

Organic geochemical,petrographic and palynological characterization of claystones of the Palaeogene Toraja Formation,and oil seeps in the Enrekang Sub-basin,south Sulawesi,Indonesia:Implications for hydrocarbon source rock potential

An organic geochemical,petrographical,and palynological evaluation was conducted on 30 claystone outcrop samples of the Toraja Formation,along with a geochemical analysis of an oil seep in the Enrekang Sub-basin.The aim of the study was to determine the correlation between oil and source rock in terms of age,depositional environment,organic material sources,and maturity level.The total organic carbon content of the claystone samples varies from 0.03 to 4.52 wt%,which are classified as poor to excellent.The claystones are immature to post-mature with a mixture of TypeⅡandⅢkerogen.Their vitrinite reflectance values range from 0.47 to 4.52%Ro.The samples of Toraja Formation rock and the oil seep source rock might have a similar depositional environment,a deltaic marine depositional setting with high oxidizing conditions.Organic material sources for rock and oil samples are dominated by terrestrial input.The oil is inferred to have originated from the Paleogene source rocks,which correlates in age with the Toraja Formation.The recovered palynomorphs from the studied rock samples suggest a late Eocene to Oligocene age with a strong terrestrial influence of shallow marine depositional setting.The biomarker analysis shows that the rock samples have a more substantial contribution from the terrigenous higher plants,while the oil sample indicates a higher degree of marine influence.The maturity levels are also different between the oil(peak mature)and the analyzed rock samples(immature).It is inferred that the oil seep source rock is equivalent to the analyzed rock sample but more mature,having been deposited under more marine conditions.The oil seep source rock is not exposed and is located in the deeper part of the basin.A deeper marine facies(i.e.distal delta front and prodelta facies)in front of the distributary mouth bar within a delta is interpreted as the source rock of the oil seep sample.

Source Rock Potential and Organic Geochemistry of Carboniferous Source Rocks in Santanghu Basin, NW China

Carboniferous source rocks identified by drilling in Santanghu （三塘湖） Basin were evaluated for their source potential, employing organic geochemistry and RockEval pyrolysis. The organic matter origin and depositional environment of these samples were also determined through biomarker analysis. Most of the Carboniferous source rocks in Santanghu Basin are characterised by high values of total organic carbon （TOC） content and high extractable organic matter content and hydrocarbon yields, indicating that they are organicrich source rocks with high oil generative potential. The organic matter is predominantly Type I and Type II kerogen with a minor contribution of Type III kerogen, as demonstrated by its pyrolysis parameters and carbon isotope values. According to Ro （%） and T max values, most of the studied samples are at earlyto middle-thermal mature stage; only a few of the samples are at a highly mature stage （past peak oil generation）. The biomarker analysis reveals a dominance of algal/bacterial organic matter input, with a minor contribution of land plant material. Pr/Ph ratio supports a suboxic depositional condition, consistent with a neritic or marine-continental alternating environment proposed by predecessor.

Geochemical identification of a source rock affected by migrated hydrocarbons and its geological significance:Fengcheng Formation,southern Mahu Sag,Junggar Basin,NW China

The Fengcheng Formation is a crucial source rock and the primary reservoir for oil accumulation in the Mahu Sag.Crude oils are distributed throughout the Fengcheng Formation,ranging from the edge to the interior of the sag in the southern Mahu Sag.These crude oils originate from in-situ source rocks in shallowly buried areas and the inner deep sag.During migration,the crude oil from the inner deep sag affects the source rocks close to carrier beds,leading to changes in the organic geochemical characteristics of the source rocks.These changes might alter source rock evaluations and oil-source correlation.Based on data such as total organic carbon(TOC),Rock-Eval pyrolysis of source rocks,and gas chromatography-mass spectrometry(GC-MS)of the saturated fraction,and considering the geological characteristics of the study area,we define the identification characteristics of source rock affected by migrated hydrocarbons and establish the various patterns of influence that migrated hydrocarbons have on the source rock of the Fengcheng Formation in the southern Mahu Sag.The source rocks of the Fengcheng Formation are mostly fair to good,containing mainly Type II organic matter and being thermally mature enough to generate oil.Source rocks affected by migrated hydrocarbons exhibit relatively high hydrocarbon contents(S1/TOC>110 mg HC/g TOC,Extract/TOC>30%,HC:hydrocarbon),relatively low Rock-Eval Tmax values,and relatively high tricyclic terpane contents with a descending and mountain-shaped distribution.Furthermore,biomarker composition parameters indicate a higher thermal maturity than in-situ source rocks.Through a comparison of the extract biomarker fingerprints of adjacent reservoirs and mudstones in different boreholes,three types of influence patterns of migrated hydrocarbons are identified:the edge-influence of thin sandstone-thick mudstone,the mixed-influence of sandstone-mudstone interbedded,and the full-influence of thick sandstone-thin mudstone.This finding reminds us that the influence of migrated hydrocarbons must be considered when evaluating source rocks and conducting oil-source correlation.

Intelligent geochemical interpretation of mass chromatograms:Based on convolution neural network

Gas chromatography-mass spectrometry(GC-MS)is an extremely important analytical technique that is widely used in organic geochemistry.It is the only approach to capture biomarker features of organic matter and provides the key evidence for oil-source correlation and thermal maturity determination.However,the conventional way of processing and interpreting the mass chromatogram is both timeconsuming and labor-intensive,which increases the research cost and restrains extensive applications of this method.To overcome this limitation,a correlation model is developed based on the convolution neural network(CNN)to link the mass chromatogram and biomarker features of samples from the Triassic Yanchang Formation,Ordos Basin,China.In this way,the mass chromatogram can be automatically interpreted.This research first performs dimensionality reduction for 15 biomarker parameters via the factor analysis and then quantifies the biomarker features using two indexes(i.e.MI and PMI)that represent the organic matter thermal maturity and parent material type,respectively.Subsequently,training,interpretation,and validation are performed multiple times using different CNN models to optimize the model structure and hyper-parameter setting,with the mass chromatogram used as the input and the obtained MI and PMI values for supervision(label).The optimized model presents high accuracy in automatically interpreting the mass chromatogram,with R2values typically above 0.85 and0.80 for the thermal maturity and parent material interpretation results,respectively.The significance of this research is twofold:(i)developing an efficient technique for geochemical research;(ii)more importantly,demonstrating the potential of artificial intelligence in organic geochemistry and providing vital references for future related studies.

Interactions of Copper, Evaporite, and Organic Matter and Genesis of Sandstone-Hosted Copper Deposits in the Chuxiong Basin, Yunnan Province

Studies on organic geochemistry indicate that the origin, type and maturity of organic matter are different among coal-bearing, copper-bearing and evaporite formations in the Mesozoic continental Chuxiong Basin, Yunnan, China. A mechanism has been proposed that (1) during the diagenetic mineralization stage the short-chain organic acids dervied from kerogen played an important role in remobilizing copper from source beds, while oils acted as important carrier of copper, and that (2) during the transformation or remolding mineralization stage, meteoric water leached the evaporite layers and formed downward-percolating oxidizing SO42-rich fluids; meanwhile, the copper-bearing fluids migrating upwards along growth faults from the basement was contaminated by the coal-bearing series on the way and formed reducing organic-rich fluids; oxidation-reduction occurred and sulfides formed when the two kinds of fluids met within sandstones.

Organic geochemical characteristics of bark coal in Changguang area: evidence from aromatic hydrocarbons

Seven coal samples were collected from Changguang area,a typical bark coal field in Zhejiang Province,China.The organic geochemical characteristics and depositional environment of bark coal were studied by Rock–Eval pyrolysis,gas chromatography(GC),and gas chromatography–mass spectrometry(GC–MS)analysis.The results show that all samples are type II kerogen.The values of total organic carbon(TOC),potential yield(S1+S2),and hydrogen index of these samples ranged from 65.80 wt%–87.00 wt%,170.43–232.89 mg HC/g,and 234–295 mg HC/g TOC,respectively.In aromatic hydrocarbons compounds of bark coal samples,the phenanthrene series occupy the largest proportion(43.48%–53.74%),followed by the dibenzothiophens(7.33%–16.53%).The distributions of naphthalenes,diphenyls,and chrysene of the samples indicate the source inputs are mainly derived from terrestrial higher plants.Furthermore,the ratios of naphthalene and phenanthrene series compounds reveal the samples are in the mature stage.Some biomarkers(Pr/Ph and C35/C31–35 homohopane),aromatic hydrocarbons(fluorene,dibenzofuran and dibenzothiophene),and high inertinite contents(14.7%–41.8%)suggest that bark coal was formed under relatively oxic conditions and was influenced by marine or brackish lakes environment.

Geochemistry of borehole cutting shale and natural gas accumulation in the deepwater area of the Zhujiang River Mouth-Qiongdongnan Basin in the northern South China Sea

The Qiongdongnan Basin and Zhujiang River（Pearl River） Mouth Basin, important petroliferous basins in the northern South China Sea, contain abundant oil and gas resource. In this study, on basis of discussing impact of oil-base mud on TOC content and Rock-Eval parameters of cutting shale samples, the authors did comprehensive analysis of source rock quality, thermal evolution and control effect of source rock in gas accumulation of the Qiongdongnan and the Zhujiang River Mouth Basins. The contrast analysis of TOC contents and Rock-Eval parameters before and after extraction for cutting shale samples indicates that except for a weaker impact on Rock-Eval parameter S2, oil-base mud has certain impact on Rock-Eval S1, Tmax and TOC contents. When concerning oil-base mud influence on source rock geochemistry parameters, the shales in the Yacheng/Enping,Lingshui/Zhuhai and Sanya/Zhuhai Formations have mainly Type Ⅱ and Ⅲ organic matter with better gas potential and oil potential. The thermal evolution analysis suggests that the depth interval of the oil window is between 3 000 m and 5 000 m. Source rocks in the deepwater area have generated abundant gas mainly due to the late stage of the oil window and the high-supper mature stage. Gas reservoir formation condition analysis made clear that the source rock is the primary factor and fault is a necessary condition for gas accumulation. Spatial coupling of source, fault and reservoir is essential for gas accumulation and the inside of hydrocarbon-generating sag is future potential gas exploration area.

Use of petrological and organic geochemical data in determining hydrocarbon generation potential of coals:miocene coals of Malatya Basin(Eastern Anatolia-Turkey)

With this study,the hydrocarbon generation potential of Miocene aged coals around Arguvan-Parçikan in the northern district of Malatya province was evaluated with the aid of petrological and organic geochemical data.According to organic petrography,coal quality data,and low thermal maturity,the Arguvan-Parçikan coals are of high-ash,high-sulfur subbituminous B/C rank.The organic fraction of the coals is mostly comprised of humic group macerals,with small percentages derived from the inertinite and liptinite groups.The mineral matter of the coals is comprised mainly of calcite and clay minerals.The total organic carbon(TOC,wt%)values of the shale and coal samples are between 2.61 wt%and 43.02 wt%,and the hydrogen index values are between 73 and 229 mg HC/g TOC.Pyrolysis(T_(max),PI),huminite/vitrinite reflectance(R_(o),%),and biomarker ratios CPI,Pr/Ph ratio,Ts/(Ts+Tm)ratio,C_(32) homohopane ratio(22S/22S+22R)and C_(29)ββ/(ββ+ααsterane ratio)indicate that the organic matter of the studied coals is thermally immature.When all these data are taken together,Miocene aged coals around Arguvan are suitable for hydrocarbon generation,especially gas,in terms of organic matter type(Type III and Type II/III mixed),organic matter amount(>10 wt%TOC),however,low liptinitic macerals(<15%–20%),low hydrogen index(<200 mg HC/g TOC)and low thermal maturity values inhibit the hyrocarbon generation.

Bio-organic Geochemical Characteristics of Gold Deposits in Northwestern Guangxi and Their Metallogenetic Significance

The gold deposits of Triassic period in the northwestern Guangxi are all located in the marine, fine -grained ,fragmental rock series containing organic matter ,i.e .the distribution districts of black rock series . The fine-grained gold deposits occur in organic matter -bearing C, D,E,or D,E divisions of the classical Bouma sequences. The evolution degree of organic matters through oil window stage reached the over -mature degree. Both the bio-sources of the organic matters and the distribution of gold in the organic matters disclose the close association between gold , living beings and organic matters . The thermal evolution of organic matters led to the gold to be activized . migrated and enriched , and finally formed gold deposits in the fault belt and crushed zone of black rock series .

Effects of Volcanic Activity on Organic Matter Sources and the Paleoenvironment:Geochemical Evidence from Upper Carboniferous Source Rocks(Batamayineishan Formation)in Eastern Junggar,NW China

The mudstone,gray tuffite and carbonaceous shale in the Upper Carboniferous Batamayineishan Formation(Bashan Formation)are essential source rocks for the volcanic reservoir in eastern Junggar,northwestern China.The kerogen components,vitrinite reflectance,Rock-Eval pyrolysis,lipid biomarkers and isotope compositions were measured to understand the provenance and depositional environment of Bashan Formation under the background of volcanic activities.There were 10 and 4 periods of volcanic eruptions identified in the wells CS and DZ,respectively.The source rocks developed in the late or intermittent phase of volcanic activity.The original island arcs of the Early Carboniferous evolved into the Wucaiwan sag and the Dishuiquan sag in the Bashan Formation.The Wucaiwan sag inherited the restricted,closed residual sea,which had a slightly anoxic and hypersaline environment.The Dishuiquan sag was generally an oxidizing lacustrine environment,influenced by a marine transgression that may have occurred at the end of the DZ_(Ⅲ)period during the Late Carboniferous.Although the total organic matter decreased due to the volcanic eruption,ash could cause an increase of aquatic organisms,coinciding with increases in salinity and reducibility in the Dishuiquan sag.

用GC-MS、GC-MS-MS方法检测某些有机质成熟度参数的比较

Tm/Ts,C29甾烷ααα20S/(20S+20R)是判断原油成熟度的重要参数.所以能否准确地检测这些化合物就显得尤为关键和重要.以往我们通常采用GC-MS单极质谱来检测原油和烃原岩抽提物中饱和烃里的萜烷和甾烷成分.……

色谱-质谱分析在有机地球化学研究中的应用

色谱-质谱分析在有机地球化学领域主要用来检测地质体中的生物标志物和分子化合物.生物标志物(biomarkers)指存在地壳和大气圈中,分子结构与特定天然产物之间具有明确联系,或与特定生物类别的分子结构之间具有相关性的天然有机化合物.……

Prospects of Carboniferous Shale Gas Exploitation in the Eastern Qaidam Basin

Shale gas is a resource of emerging importance in the energy field.Many countries in the world have been making big financial investments in this area.Carboniferous shale in the eastern Qaidam Basin shows good exploration prospects,but limited research and exploration work for shale oil and gas resources has been undertaken.Geochemical analyses were performed on shale derived from the Upper Carboniferous Hurleg Formation in the eastern Qaidam Basin,Qinghai Province,and secondary electron imaging capability of a Field Emission scanning electron microscope （FE-SEM） was used to characterize the microstructure of the shale.The reservoir and exploitation potential of the studied shale was assessed by comparison with research results obtained from the Barnett Formation shale in Fort Worth Basin,North America and the Basin shale of Sichuan province.The results indicate that the eastern Qaidam Basin Carboniferous shale is high-quality source rock.There are four major microstructural types in the study area：matrix intergranular pores,dissolution pores,intergranular pores,and micro-fractures.The size of the micropores varies from 6-633 nm,the majority of which is between 39-200 nm,with a relatively small number of micro-scale pores ranging from 0.13-1 μtm.The pore characteristics of the studied shales are similar to the North American and Sichuanese shales,indicating that they have good reservoir potential.No micropores are present in the organic matter,which is induced by its composition; instead we found an important lamellar structure in the organic matter.These micropores and microfractures are abundant,and are connected to natural visible cracks that form the network pore system,which controls the storage and migration of shale gas.This connectivity is favorable for shale gas exploitation,providing great scientific potential and practical value.

原油与沉积物中的二苯并噻吩系列化合物的GC-MS分析及其在有机地球化学中的应用

This paper introduced the GC-MS analysis method of the dibenzothiophene series compound in the crude oil and the deposit and the thiophene series compound application in the organic geochemistry.The ratios of dibenzothiophene to phenanthrene and pristine to phytane as indicators of depositional environment of petroleum and source rocks.2,4/1,4 dimethyl-dibenzothiophene can be the valid index of the mature degree of the crude oil and source rocks.

Reservoir Characteristics of Fine-grained Sedimentary Rocks in Saline Lakes in the Cenozoic Upper Ganchaigou Formation,Southwestern Qaidam Basin,NW China

Cenozoic fine-grained sedimentary rocks in the southwestern Qaidam Basin,as typical salinized lacustrine sediments,are significantly different from those in other freshwater lakes under the impact of the high salinity in the lake.Many fine-grained sedimentary rock samples were selected from the lower member of Neogene(N_(1))in the Gaskule Oilfield,Qaidam Basin,northwest China,with the aim to analyze and test their petrology,pore structure,and organic geochemical characteristics and determine its genesis and geological significance.Based on previous results,a new genesis of mixed sedimentary rocks is proposed.The Cenozoic lacustrine fine-grained sedimentary rocks in SW Qaidam Basin belong to mixed sedimentary rocks,which can be divided into three types,including carbonate and terrigenous clastic-bearing mudstone,carbonate-bearing to terrigenous clastic mixed sedimentary rocks,and carbonate-terrigenous clastic mixed sedimentary rocks.The geneses of mixing are quite different from that of mixed marine rocks.According to the sedimentary characteristics of the salinized lakes,three new geneses of mixed deposits are proposed:syn-sedimentary mixing,varve interbedded mixing,and biogenic mixing.The reservoir spaces of the Cenozoic lacustrine fine-grained sedimentary rocks in SW Qaidam Basin include residual intergranular pores,intercrystalline pores,microfractures,and minor dissolved pores.The reservoirs have super-low porosity and ultra-low permeability,with a porosity of 1.82%-21.04%,averaging 7.71%,and permeability of(0.0028-254.86)×10^(−3)μm^(2),averaging 2.82×10^(−3)μm^(2).The test results of total organic carbon(TOC)content show that the highest content of organic carbon reached 1.41%,and those of vitrinite reflectance show that Ro ranges from 0.525%-0.824%,with an average of 0.806%.The organic geochemical characteristics show that the fine-grained mixed sedimentary rocks of SW Qaidam Basin have the potential for self-generation and self-storage.As an unconventional reservoir,it has potential industrial value.This is the first study of fine-grained sedimentary rocks in the Qaidam Basin,which offers certain theoretical and practical values.

Geochemical characteristics of Early Cretaceous source rocks in Boli Basin

The Early Cretaceous deposits are composed of important source rocks in Boli Basin. The types of the source rocks include black mudstones and coal (with carbonaceous mudstone). By the organic geochemical analysis methods, the authors discussed the organic petrological characters, abundance of organic matter, degree of maturity and the type of source rocks. The main micro-component of black mudstone is exinite or vitrinite, and the content of vitrinite is high in coal. The weathering of the outcrop is very serious. The abundance of organic matter in source rock reaches the poor to better rank. The major kerogens in mudstone are type-Ⅲ, type-Ⅱ 2 and some type-Ⅱ 1; the organic type of coal is type-Ⅲ. The thermal evolution of the source rocks in every structural unit is very different, from low-maturity to over-maturity. The depositional environment is reductive, which is good for the preservation of organic matter. The organic matter in source rocks is mainly from aquatic organisms and terrigenous input.

Characteristics of source rocks and paleoenvironment of Lower Silurian Longmaxi Formation in western Hubei

Based on feild outcrop survey,lithology observation and systematic sampling,and with the scanning electron microscope,rock pyrolysis,biomarker compound test and analysis,this paper discussed source rock characteristics and paleoenvironment in western Hubei.The lithology at the bottom of Lower Silurian Longmaxi Formationn in this study area is mainly dark carbonaceous shale,the mineral composition is mostly clay minerals,quartz and feldspar,the content of illite and kaolinite is high,but also contains a minor amount of strawberry pyrite and graptolite fossils.The test and analysishow that the total organic carbon content(TOC)of the source rock is 0.8-6.32%,the average value is 3.42%,and the vitrinite reflectance(Ro)is 1.57-2.95%.The type of organic matter is mainly typeⅡ2.The overall abundance of organic matter is high,and the degree of thermal evolution has reached the stage of high maturity and over maturity.All these have become the good material basis and conditions for the formation of shale gas.The paleoenvironment of the source rocks indicates that the organic matter is a mixed source of planktonic algae and bacteria material.The large amount of hopane also indicates that the bacterial activity is strong during the deposition of organic matter;The water of the ancient lake is almost freshwater and brackishwater in some parts;The redox property of the water is in a strong reduction environment and with a stable stratification,which is also conducive to the preservation of organic matter.The above research results will provide the application of shale gas exploration in western Hubei.

Utilization of Pyrrolic Compounds as Indicators of Secondary Migration for Woodford Oils in the Anadarko Basin,Oklahoma,USA

Migration pathways and distances of the oils in reservoir are thought to affect the distribution of pyrrolic compounds such as carbazole,its alkyl derivatives(alkylated carbazoles)and benzocarbazoles,although other factors,including maturity and depositional environments may also affect the distribution of these organic nitrogen compounds.In this study,14 oil samples produced from conventional reservoirs in Pauls Valley,south Oklahoma were investigated using organic geochemical techniques.The sterane and hopane fingerprints suggest that most of the oils were sourced from the Devonian Woodford shale.Maturity parameters consistently indicate that the maturity level of the studied samples are all of similar maturity(Rc=~0.7%),suggesting the distribution of the organic nitrogen organic compounds is possibly reflecting variations in relative migration distances.The distribution of alkylcarbazoles revealed a preferential enrichment during migration,with the nitrogen-shielded alkylcarbazole tending to be enriched relative to the nitrogen-semi-shielded alkylcarbozoles particularly in oils produced close to the Arbuckle uplift to the east.Correspondingly,another family of pyrrolic compounds,benzocarbazoles,whose distributions also indicated that the Pauls Valley Woodford oils came from deeper part of the Anadarko Basin as the benzo-[a]/([a]+[c])-carbazole ratios decrease eastwards.In more specific migration systems,although the pyrrolic compound indicators are potentially disturbed by the structural complexes,the general migration directions suggest that the studied oils in Pauls Valley Hunton uplift were sourced from the deep basin area,and migrate upwards in porous sediments due to the buoyancy.This study investigates the feasibility of using pyrrolic compounds to estimate relative migration distances and will aid in the interpretation of migration history by using the distribution of carbazole,alkylated carbazoles,benzocarbazoles isomers in the Anadarko and Ardmore Basin petroleum systems.

Geochemistry and possible origin of the hydrocarbons from Wells Zhongshen1 and Zhongshen1C, Tazhong Uplift

In 2013, a great breakthrough of deep petroleum exploration was achieved in the Cambrian pre-salt intervals of Wells Zhongshen1(ZS1) and Zhongshen1C(ZS1C), Tazhong Uplift. However, the hydrocarbon discovery in the Cambrian pre-salt intervals has triggered extensive controversy regarding the source of marine oils in the Tarim Basin. The geochemistry and origin of the Cambrian pre-salt hydrocarbons in Wells ZS1 and ZS1 C were investigated using GC, GC-MS and stable carbon isotope technique. These hydrocarbons can be easily distinguished into two genetic families based on their geochemical and carbon isotopic compositions. The oil and natural gases from the Awatage Formation of Well ZS1 are derived from Middle-Upper Ordovician source rocks. In contrast, the condensate and gases from the Xiaoerbulake Formation of Wells ZS1 and ZS1 C probably originate from Cambrian source rocks. The recent discovery of these hydrocarbons with two different sources in Wells ZS1 and ZS1 C suggests that both Middle-Upper Ordovician-sourced hydrocarbons and Cambrian-sourced petroleums are accumulated in the Tazhong Uplift, presenting a great exploration potential.