Secondary Hydrocarbon Research Articles

The Synergistic Effect of a Bimetallic Catalyst for the Synthesis of Carbon Nanotube Aerogels and their Predominant Chirality.

Synthesis of continuous spinnable carbon nanotube (CNT) fibers is the most promising method for producing CNT fibers for commercial applications. The floating-catalyst chemical vapor deposition (FC-CVD) method is a rapid process that achieves catalyst formation, CNT nucleation and growth, and aerogel-like sock formation within a few seconds. However, the formation mechanism is unknown. Herein, the progress of CNT fiber formation with bimetallic catalysts was studied, and the effect of catalyst composition to CNT fiber synthesis and their structural properties was investigated. In the case of bimetallic catalysts, the carbon source rapidly decomposes and generates various secondary hydrocarbon species, such as CH4 , C2 H4 , C2 H2 , C3 H6 , and C4 H10 whereas monometallic catalysts generate only CH4 and C2 H4 on decomposition. CNT fiber formation with Fe1 Ni0 begins about 400 mm from the reactor entrance, whereas CNT formation with Fe0.8 Ni0.2 and Fe0.5 Ni0.5 begins at about 500 and 300 mm, respectively. The formed CNT bundles and individual CNTs are oriented along the gas flow at these locations. The enhanced rate of fiber formation and lowering of growth temperature associated with bimetallic catalysts is explained by the synergistic effects between the two metals. The synthesized CNTs become predominantly semiconducting with increasing Ni contents.

Mechanisms for the accumulation of deep gas in the southern Songliao Basin, China

The Lower Cretaceous Yingcheng Formation in the southern Songliao Basin contains inorganic CO2, hydrocarbon, and mixed-gas reservoirs and is overlain by Denglouku Formation sandstone hosting secondary hydrocarbon gas reservoirs. We measured the diffusion coefficients of CH4 and CO2 in volcanic rock samples collected from five wells in the Yingcheng Formation. Our results show that the diffusion coefficient of CH4 is greater than that of CO2. Following the accumulation of hydrocarbon gas in the Yingcheng Formation, the region was affected by movement along deep-seated faults, resulting in the upward migration of mantle-derived inorganic CO2 into hydrocarbon gas reservoirs in volcanic rocks of the Yingcheng Formation, displacing pre-existing hydrocarbon gas. The hydrocarbon gas was transported upward into Denglouku Formation sandstone (which has favorable physical properties for gas storage) and was then enriched to form secondary gas reservoirs.

Estimation of prospects of oil and gas production of Barents Sea shelf by results of seismic measurement by 3D common dept point method

The article shows the tectonic confinement of the research area and its position from the point of view of petroleum geological classification, and the main oil and gas bearing complexes are identified. According to the Triassic, Jurassic-Barremian and Aptian-Albian-Cenomanian oil and gas bearing complexes, a seismic-geological model was given, the conditions for the formation of deposits were considered, prospective objects were identified, and the optimal volume of exploratory drilling was planned. The complex of features indicates the presence of vertical migration of hydrocarbons, which contribute to the formation of secondary hydrocarbon deposits in the Cretaceous section.

A method for evaluating paleo hydrocarbon pools and predicting secondary reservoirs: a case study of the Sangonghe Formation in the Mosuowan area, Junggar Basin

Taking the Jurassic Sangonghe Formation in the Mosuowan-Mobei area of the Junggar Basin as an example, this paper provides a method that evaluates paleo hydrocarbon pools and predicts secondary reservoirs. Through Quantitative Grain Fluorescence (QGF) experiments, well-tie seismic correlation, and paleo structure analysis, the scale and distribution of paleo hydrocarbon pools in the study area are outlined. Combining current structural features and fault characteristics, the re-migration pathways of paleo oil and gas are depicted. Based on barrier conditions on the oil re-migration pathways and current reservoir distribution, we recognize three types of secondary reservoirs. By analyzing structural evolution and sand body-fault distribution, the major control factors of secondary reservoirs are specified and, consequently, favorable zones for secondary reservoirs are predicted. The results are mainly as follows. (1) In the primary accumulation period in the Cretaceous, paleo hydrocarbon pools were formed in the Sangonghe Formation of the Mosuowan uplift and their size and distribution were extensive and the exploration potential for secondary reservoirs should not be ignored. Besides, paleo reservoirs were also formed in the Mobei uplift, but just small scale. (2) In the adjustment period in the Neogene, traps were reshaped or destroyed and so were the paleo reservoirs, resulting in oil release. The released oil migrated linearly northward along the structural highs of the Mobei uplift and the Qianshao low-relief uplift and then formed secondary reservoirs when it met new traps. In this process, a structural ridge cooperated with sand bodies and faults, applying unobstructed pathways for oil and gas re-migration. (3) The secondary hydrocarbon pools are classified into three types: low-relief anticlinal type, lithologic pinch-out type and fault block type. The distribution of the first type is controlled by a residual low uplift in the north flank of the paleo-anticline. The second type is distributed in the lithologic pinch-out zones on the periphery of the inherited paleo uplift. The third type is controlled by fault zones of which the strikes are perpendicular to the hydrocarbon re-migration pathways. (4) Four favorable zones for secondary reservoirs are predicted: the low-relief structural zone of the north flank of the Mosuowan paleo-anticline, the fault barrier zone on the western flank of the Mobei uplift, the Qianshao low-relief uplift and the north area of the Mobei uplift that parallels the fault zone. The study above effectively supports the exploration of the Qianshao low-relief uplift, with commercial oil discovered in the Qianshao1 well. Besides, the research process in this paper can also be applied to other basins to explore for secondary reservoirs.

Fuzzy optimization of the automotive ammonia fuel cycle

Abstract Ammonia has favorable properties for use in automotive fuel applications, such as good storage properties and mature production and distribution infrastructure. However, the sustainability of ammonia as an alternative automotive fuel remains in question, due to the significant environmental impact of conventional production technology and the need for a secondary hydrocarbon fuel to promote combustion when used in internal combustion engines. The two commercially implemented processes for ammonia: steam reforming and partial oxidation, a wood-based syngas process and a cyanobacterial process combined are considered in the life cycle optimization of the ammonia-based fuel system. It is assumed that the functional unit is 1 km travelled by a representative light-duty internal combustion engine vehicle. Two conventional fuels are also considered as secondary fuel in this study, namely, gasoline and diesel. Fuzzy linear programming is applied using carbon and nitrogen footprint as environmental objectives. The cyanobacteria-based process combined with gasoline as the secondary fuel was identified as the optimal solution. The most significant parameter was the end-user vehicle fuel economy. Hence, more attention must be given to the improvement of vehicle technology to enable the sustainable use of ammonia for transportation.

Identification of Carbon loss in the production of pilot-scale Carbon nanotube using gauze reactor

Carbon loss more than 65% was the major obstacles in the Carbon Nanotube (CNT) production using gauze pilot scale reactor. The results showed that the initial carbon loss calculation is 27.64%. The calculation of carbon loss, then, takes place with various corrections parameters of: product flow rate error measurement, feed flow rate changes, gas product composition by Gas Chromatography Flame Ionization Detector (GC FID), and the carbon particulate by glass fiber filters. Error of product flow rate due to the measurement with bubble soap gives calculation error of carbon loss for about ± 4.14%. Changes in the feed flow rate due to CNT growth in the reactor reduce carbon loss by 4.97%. The detection of secondary hydrocarbon with GC FID during CNT production process reduces carbon loss by 5.14%. Particulates carried by product stream are very few and merely correct the carbon loss about 0.05%. Taking all the factors into account, the amount of carbon loss within this study is (17.21 ± 4.14)%. Assuming that 4.14% of carbon loss is due to the error measurement of product flow rate, the amount of carbon loss is 13.07%. It means that more than 57% of carbon loss within this study is identified.

Geochemistry and charge history of oils from the Yuqi area of Tarim Basin, NW China

The geochemistry, origin and charge history of oils from the Yuqi area of Tarim Basin have been investigated, through GC, GC-MS and fluid inclusion microthermometry analysis. The Yuqi oils accumulated mainly in three intervals: (1) in the Lower-Middle Ordovician Yingshan Formation (O1-2y) carbonate reservoirs; (2) in the overlying Upper Triassic Halahatang Formation (T3h); and (3) in the Lower Cretaceous Yageliemu Formation (K1y) sandstones. Oils from different reservoirs have distinct physical properties, varying from extra-heavy (O1-2y), heavy (T3h), to light oils (T3h and K1y). However, their geochemical compositions show a high degree of similarity, which indicates that they derive from the same source rock. Abundant tricyclic terpanes, gammacerane, dibenzothiophene and C21C22steranes, together with a low level of diasteranes, indicate an anoxic marine source rock for oils in the Yuqi area. Oil-oil correlation shows that Yuqi oils derive from the same source bed as Tahe oils. The co-occurrence of intact n-alkanes and 25-norhopanes in all the samples supports the proposition that there is a mixture of an early filled severely biodegraded oil and a late filled fresh oil.In this study, charge history is examined on the basis of integration of fluid inclusion homogenization temperature data with 1D burial-thermal history models. Two episodes of oil charging are identified in the O1-2y reservoir (well YQX1-1) at around 436-420 Ma (Middle-Late Silurian) and 10-3 Ma (Miocene to Pliocene), respectively. For the samples from the T3h and K1y intervals, only one episode of oil charge is indicated by the homogenization temperatures of coexisting aqueous inclusions with an inferred timing around 10-3 Ma. The T3h heavy oil reservoir is assumed to be a secondary hydrocarbon pool, which accumulated by re-migration and re-distribution of hydrocarbons from O1-2y hydrocarbon pools. The few early biodegraded oils in the K1y light oils were probably picked up along the migration pathway during the late fresh oil charging.

Hydrocarbon gas generation from pyrolysis of extracts and residues of low maturity solid bitumens from the Sichuan Basin, China

Two sets of pyrolysis experiments were performed on bitumen “A” (BA) and extracted organic matter (ER) from low-maturity solid bitumen at heating rates of 2°C/h and 20°C/h in confined systems (gold capsules). The main observations can be listed as follows: (1) BA and ER have high generation potential of hydrocarbons and were a significant secondary hydrocarbon source. (2) Both have similar evolutionary characteristics of hydrocarbon gas generation, and have high C1/C1–5 values than those from an Ordovician normal oil. Ea distributions of the methane generated from pyrolysis of BA and ER is far lower than that of Ordovician normal oil. (3) The evolution of stable carbon isotope values of individual hydrocarbon gases can be divided into three stages. Plots of lnC1/C2 versus lnC2/C3, δ13C1–δ13C2 versus ln(C1/C2) and δ13C2–δ13C3 versus ln(C2/C3) clearly illustrate the characteristics of hydrocarbon gases generated from BA and ER at different thermal maturity stages. (4) Basin modelling reconstructions of the hydrocarbon generation history of BA and ER in Sinian and Cambrian strata respectively indicate: Hydrocarbon gases generation from ER started in the Middle Jurassic, and ended in the Early Cretaceous with a maturity equivalent to Easy%Ro≈2.2%. The final conversion rate of C1–5 and C1 are 0.71 and 0.48, respectively. Hydrocarbon gas generation from BA started in the Early Jurassic, and ended in the Early Cretaceous with an Easy%Ro≈3.0%. The final conversion rate of C1–5 and C1 are 0.90 and 0.81, respectively.

Numerical simulation of hydrocarbon migration in tight reservoir based on Artificial Immune Ant Colony Algorithm: A case of the Chang 81 reservoir of the Triassic Yanchang Formation in the Huaqing area, Ordos Basin, China

The hydrocarbon migration in tight reservoirs is a complex process, the fluid flow patterns of which are notably different from those of conventional reservoirs. Therefore, specific mathematical models are needed to simulate the secondary hydrocarbon migrations. This study presents a numerical simulation method based on Artificial Immune Ant Colony Algorithm (AIACA) to simulate the secondary hydrocarbon migrations in tight reservoirs. It consists of three core parts: (1) the release modes of artificial ants based on the intensity of hydrocarbon generation; (2) the wandering patterns of artificial ants under the control of the dynamic field and the distribution of pheromones; (3) the updating modes of pheromones based on the changes in reservoir wettability. The simulation of secondary migration can be realized by the observing the dynamic movements and accumulations of the artificial ants. The method has been tested in the Chang 81 tight sandstone reservoir, which is part of the Triassic Yanchang Formation in the Huaqing Area, Ordos Basin in China, and proved to be successful in matching the current data in exploration and development.

MESOZOIC THERMAL EVENTS IN CENTRAL LOWER YANGTZE AREA AND IMPACTS ON HYDROCARBON GENERATION OF MARINE SOURCE ROCKS

AbstractTemperature is a key parameter of controlling hydrocarbon generation of source rocks. Elevated temperature resulted from tectonothermal events may significantly affect hydrocarbon generation. Based on geology, fission track analysis, apatite U‐Th/He and volcanic rock isotopic age data, it is found that there existed Indosinian (T3‐J2) and Yanshanian (J3‐K1) tectonothermal events in Lower Yangtze area and the sedimentary basins reached their peak heat flow at about 130∼110 Ma. The maximum heat flows obtained from thermal history reconstruction based on vitrinite reflectance are ∼94 mW·m–2 and ∼78 mW·m–2 in Jurong and Taixing areas respectively, with an increasing trend from east to west. Hydrocarbon generation history reconstruction based on the EASY%Ro model shows that the dominating gas generation periods of the Cambrian source rock are the Early Permian‐Late Triassic and the Late Triassic‐Early Cretaceous in Changzhou and Jurong areas respectively. Because of the dual effects from the foreland sediments deposited in T3‐J1–2 and the magmatism thermal event in the Early Cretaceous, the marine source rocks reached their maximum temperature at the end of Early Cretaceous. The temperature of the marine source rocks was no longer elevated owing to the decreased heat flow since the Late Cretaceous, though, in some parts of the Jurong, Taixing and Changzhou areas, subsidence occurred and burial depth increased during the K2‐E period. Therefore, the secondary hydrocarbon generation of the marine source rocks is not a widespread process in central Lower Yangtze area.

Secondary migration of hydrocarbons in the Zhujiang Formation in the Huixi half-graben, Pearl River Mouth Basin, South China Sea

The process and mechanisms of secondary hydrocarbon migration in the Huixi half-graben, Pearl River Mouth Basin, were investigated on the basis of geological analysis of the strata and study of the porosity and permeability of the reservoir rocks, fluid potential, oil properties, and geochemistry of oil–source correlation. The results suggest that the hydrocarbons of the Zhujiang Formation in the Huixi half-graben were derived from source rocks of the Eocene Wenchang Formation and the Eocene–Oligocene Enping Formation in the Huizhou Sag. The hydrocarbons migrated laterally from northeast to southwest. The sandstone in the upper member of the Zhujiang Formation exhibited superior physical properties (porosity and permeability) and connectivity than the lower member. Thin sandstone beds with good physical properties and stable distribution in the upper member of the Zhujiang Formation were the main carrier beds for lateral hydrocarbon migration.

The evolution of Devonian hydrocarbon gases in shallow aquifers of the northern Appalachian Basin: Insights from integrating noble gas and hydrocarbon geochemistry

The last decade has seen a dramatic increase in domestic energy production from unconventional reservoirs. This energy boom has generated marked economic benefits, but simultaneously evoked significant concerns regarding the potential for drinking-water contamination in shallow aquifers. Presently, efforts to evaluate the environmental impacts of shale gas development in the northern Appalachian Basin (NAB), located in the northeastern US, are limited by: (1) a lack of comprehensive “pre-drill” data for groundwater composition (water and gas); (2) uncertainty in the hydrogeological factors that control the occurrence of naturally present CH4 and brines in shallow Upper Devonian (UD) aquifers; and (3) limited geochemical techniques to quantify the sources and migration of crustal fluids (specifically methane) at various time scales. To address these questions, we analyzed the noble gas, dissolved ion, and hydrocarbon gas geochemistry of 72 drinking-water wells and one natural methane seep all located ≫1km from shale gas drill sites in the NAB. In the present study, we consciously avoided groundwater wells from areas near active or recent drilling to ensure shale gas development would not bias the results. We also intentionally targeted areas with naturally occurring CH4 to characterize the geochemical signature and geological context of gas-phase hydrocarbons in shallow aquifers of the NAB. Our data display a positive relationship between elevated [CH4], [C2H6], [Cl], and [Ba] that co-occur with high [4He]. Although four groundwater samples show mantle contributions ranging from 1.2% to 11.6%, the majority of samples have [He] ranging from solubility levels (∼45×10−6cm3 STP/L) with below-detectable [CH4] and minor amounts of tritiogenic 3He in low [Cl] and [Ba] waters, up to high [4He]=0.4cm3 STP/L with a purely crustal helium isotopic end-member (3He/4He=∼0.02 times the atmospheric ratio (R/Ra)) in samples with CH4 near saturation for shallow groundwater (P(CH4)=∼1 atmosphere) and elevated [Cl] and [Ba]. These data suggest that 4He is dominated by an exogenous (i.e., migrated) crustal source for these hydrocarbon gas- and salt-rich fluids. In combination with published inorganic geochemistry (e.g., 87Sr/86Sr, Sr/Ba, Br−/Cl−), new noble gas and hydrocarbon isotopic data (e.g., 20Ne/36Ar, C2+/C1, δ13C-CH4) suggest that a hydrocarbon-rich brine likely migrated from the Marcellus Formation (via primary hydrocarbon migration) as a dual-phase fluid (gas+liquid) and was fractionated by solubility partitioning during fluid migration and emplacement into conventional UD traps (via secondary hydrocarbon migration). Based on the highly fractionated 4He/CH4 data relative to Marcellus and UD production gases, we propose an additional phase of hydrocarbon gas migration where natural gas previously emplaced in UD hydrocarbon traps actively diffuses out into and equilibrates with modern shallow groundwater (via tertiary hydrocarbon migration) following uplift, denudation, and neotectonic fracturing. These data suggest that by integrating noble gas geochemistry with hydrocarbon and dissolved ion chemistry, one can better determine the source and migration processes of natural gas in the Earth’s crust, which are two critical factors for understanding the presence of hydrocarbon gases in shallow aquifers.

Seismic characteristics of fluid escape pipes in sedimentary basins: Implications for pipe genesis

Fluid escape pipes were first documented from 3D seismic data over a decade ago, and have subsequently been identified in many petroliferous basins worldwide. They are characterized on seismic data by vertical to sub-vertical zones of reduced reflection continuity that have a columnar geometry in three-dimensions. The upper terminations of these pipes commonly coincide with pockmarks or palaeo-pockmarks, signifying a close connection of pipe formation with a high flux fluid expulsion process. Dimensions range from tens to hundreds of metres in diameter, and hundreds to over a thousand metres in height, and the slenderness ratio, defined as height/diameter (Ω), ranges from 0.8 to over 20. Pipes are frequently associated with sub-vertical clustering of amplitude anomalies on seismic data, related either to the presence of free gas, or to cementation linked to the passage of hydrocarbons.Three mechanisms have been suggested to explain pipe genesis: (1) hydraulic fracturing, (2) erosional fluidisation, and (3) capillary invasion. We suggest a further two possible mechanisms in the form of localised collapse by volume loss and synsedimentary flow localisation. We review all five mechanisms and conclude that it is unlikely that a single mechanism applies but that combinations of these processes may all occur in particular contexts. Fluid escape pipes may be far more widespread that currently appreciated, and they may play a critical role in secondary hydrocarbon migration and in providing leakage pathways for trapped hydrocarbons through overlying seals.

Controls by organic geochemistry trackers of secondary hydrocarbon accumulation during Neotectonic central uplift of the Tarim basin

Abstract Because of the Himalayan Neotectonic uplift, the Tarim Tectonic Block, a cratonic terrane which contain cover rocks of the Lower Paleozoic marine succession (a marginal basin containing huge petroleum paleo-reservoirs) experienced strong extrusion tendency. This extrusion was one of the most important factors to control the migration or accumulation of petroleum, and impact the pattern of paleo-reservoirs. In the Tarim basin, the Neotectonic activity tilted the Carboniferous and younger formation and activated old fractures. The inherited active faults of Tazhong area are mainly distributed in two big groups, respectively around the central uplift and the Tazhong-I faults. Tazhong-4 structure is combined with the two major fault zones, and is strongly affected by Neotectonics. According to the distribution characteristics of triaromatic dinosterane, 4-methyl-cholestanes and other special biomarkers in the oil samples of Tazhong-4 area, it was showed that oils in the different reservoirs were from the same source. And the vertical Pressure–Volume–Temperature (PVT) characteristics of the petroleum reservoirs changed from unsaturated oils into the unsaturated condensates. It was shown that the Tazhong-4 reservoirs had experienced a complicated accumulation process of multi-period charge, mixture and adjustment, which related closely with the multi-stage compressive Neotectonics affecting the Cenozoic sequences of the Tarim Basin and its lower paleozoic source rocks and paleo-reservoirs. The transport parameters of nitrogen compounds indicated the vertical migration of petroleum in the Tazhong-4 reservoirs. The paleozoic and current oil–water contacts (POWC & OWC) could be clearly separated by the analysis of the grains with oil inclusion (GOI). Based on the gas chromatography of oil–sand between POWC and OWC, biodegradation was not obvious. That reflects the formation of OWC and migration of POWC occurred much later. Recent activity of fault led to vertical migration of hydrocarbons and the OWC of paleo-reservoir ascended. In the central uplift of basin platform area, the multi-stratum hydrocarbons migrated and accumulated along the active faults, opening during Neotectonic activity.

Multi-stage primary and secondary hydrocarbon migration and accumulation in lacustrine Jurassic petroleum systems in the northern Qaidam Basin, NW China

To improve the understanding on lacustrine Jurassic petroleum migration and accumulation in the northern Qaidam Basin (NW China), we conduct an integrated analysis of the petrography and geochemistry of oil-bearing fluid inclusion, including inclusion petrography, homogenization temperature combined with reservoir burial and thermal history, and reservoir sequential extraction. Results show that during the first stage of late Oligocene to early Miocene, the deep Paleogene reservoir was first charged by oils sourced from Middle Jurassic rocks (petroleum inclusion). This charge was accompanied by some oil alteration. During the second stage of early to middle Miocene, the deep Paleogene reservoir was charged by Lower-Jurassic-sourced oils (intergranular free oil) and this charging event is different from the first one in that it witnessed little hydrocarbon alteration. During the third stage in the Pliocene, widespread gas sourced from Lower and Middle Jurassic rocks occurred in both the deep Paleogene and shallow Neogene reservoirs and primary oil accumulations in deep Paleogene reservoirs migrated vertically to shallow Neogene reservoirs along faults, and formed secondary accumulations. Little alteration took place, favorable for the remigration. Thus, the lacustrine Lower and Middle Jurassic petroleum systems in the northern Qaidam Basin represent multi-stage primary and secondary hydrocarbon accumulations and mixing of hydrocarbons was very common.

Geochemical Characteristics and Hydrocarbon Generation Processes of Cretaceous Source Rocks in the Songliao Basin

The Fulongquan Depression is a major production area for natural gas in the Songliao Basin. This study was based on geochemical analysis of source rocks. Our results indicate that the kerogen types are primarily type III. These rocks represent a source of gas in a highly mature stage. The basin was formed during two major events of tectonic subsidence and uplift between 144 and 95 Ma before present. These periods were followed by a stable sedimentary burial phase. In the Cretaceous fault period, processes of secondary hydrocarbon generation were present. Corresponding to the two major tectonic subsidence movements, there were two key hydrocarbon generation processes. Contingent on research on sedimentary facies, source rock thicknesses, and the distribution and intensity of hydrocarbon generation, the northern and southern parts of this depression represent favorable areas for the exploration and development of hydrocarbon extraction.

Hydrocarbon Accumulation Process in the Marine Strata in Jianghan Plain Area, Middle China

Marine strata in the Jianghan Plain area are widely distributed with a total depth of more than 8,000 m from the Upper Sinian to the Middle Triassic. Six reservoir caprock units, named Z–€2, €2–O, S, D–C, P and T1, can be identified with each epoch. The geology, stratigraphy, drilling, oil testing and other basic data as well as the measured inclusion and strontium isotope data in the study area are used in the analysis of the formation and evolution process of marine petroliferous reservoirs in the Jianghan Plain area. This study aims to provide a scientific basis for the further exploration of hydrocarbons in the Jianghan Plain and reduce the risks by analyzing the key factors for hydrocarbon accumulation in the marine strata. Our findings show that in the Lower Palaeozoic hydrocarbon reservoir, oil/gas migration and accumulation chiefly occurred in the early period of the Early Yanshanian, and the hydrocarbon reservoir was destroyed in the middle–late period of the Early Yanshanian. In the Lower Triassic–Carboniferous hydrocarbon reservoir, oil/gas migration and accumulation chiefly occurred in the Early Yanshanian, and the hydrocarbon reservoir suffered destruction from the Late Yanshanian to the Early Himalayanian. The preservation conditions of the marine strata in the Jianghan Plain area have been improved since the Late Himalayanian. However, because all source beds have missed the oil/gas generation fastigium and lost the capacity to generate secondary hydrocarbon, no reaccumulation of hydrocarbons can be detected in the study area's marine strata. No industrially exploitable oil/gas reservoir has been discovered in the marine strata of Jianghan Plain area since exploration began in 1958. This study confirms that petroliferous reservoirs in the marine strata have been completely destroyed, and that poor preservation conditions are the primary factor leading to unsuccessful hydrocarbon exploration. It is safely concluded that hydrocarbon exploration in the marine strata of the study area is quite risky.

Hydrocarbon migration and accumulation in the Upper Cretaceous Qingshankou Formation, Changling Sag, southern Songliao Basin: Insights from integrated analyses of fluid inclusion, oil source correlation and basin modelling

The Upper Cretaceous Qingshankou Formation acts as both the source and reservoir sequence in the Changling Sag, situated in the southern end of the Songliao Basin, northeast China. An integrated approach involving determination of hydrocarbon charging history, oil source correlation and hydrocarbon generation dynamic modeling was used to investigate hydrocarbon migration processes and further predict the favorable targets of hydrocarbon accumulations in the Qingshankou Formation. The hydrocarbon generation and charge history was investigated using fluid inclusion analysis, in combination with stratigraphic burial and thermal modeling. The source rocks began to generate hydrocarbons at around 82Ma and the hydrocarbon charge event occurred from approximately 78Ma to the end of Cretaceous (65.5Ma) when a large tectonic uplift took place. Correlation of stable carbon isotopes of oils and extracts of source rocks indicates that oil was generated mainly from the first member of Qingshankou Formation (K2qn1), suggesting that hydrocarbon may have migrated vertically. Three dimensional (3D) petroleum system modeling was used to evaluate the processes of secondary hydrocarbon migration in the Qingshankou Formation since the latest Cretaceous. During the Late Cretaceous, hydrocarbon, mainly originated from the Qianan depression, migrated laterally to adjacent structural highs. Subsequent tectonic inversion, defined as the late Yanshan Orogeny, significantly changed hydrocarbon migration patterns, probably causing redistribution of primary hydrocarbon reservoirs. In the Tertiary, the Heidimiao depression was buried much deeper than the Qianan depression and became the main source kitchen. Hydrocarbon migration was primarily controlled by fluid potential and generally migrated from relatively high potential areas to low potential areas. Structural highs and lithologic transitions are potential traps for current oil and gas exploration. Finally, several preferred hydrocarbon accumulation sites have been identified by this work, like Western Slope, Southern uplift, and Eastern Slope, helping reduce the risk on targeting hydrocarbon potential reservoirs in Changling Sag.

Thermal effects of magmatic sills on coal seam metamorphism and gas occurrence

Igneous intrusions in coal seams are found in 80 % of coal mines in the Huaibei coalfield, China, and coal and gas outburst accidents have occurred 11 times under a 120-m-thick sill in the Haizi mining field. The magma’s heat had a significant controlling effect on coal seam gas occurrence. Based on theoretical analysis, experimental tests and site validation, we analyzed the temperature distribution following magma intrusion into coal measure strata and the variations in multiple physical parameters and adsorption/desorption characteristics between the underlying coal seams beneath the sill in the Haizi mining field and coal seams uninfluenced by magma intrusion in the adjacent Linhuan mining field. The research results show that the main factors controlling the temperature distribution of the magma and surrounding rocks in the cooling process include the cooling time and the thickness and initial temperature of the magmatic rock. As the distance from sill increases, the critical effective temperature and the duration of sustained high temperatures decrease. The sill in the Haizi mining field significantly promoted coal seam secondary hydrocarbon generation in the thermally affected area, which generated approximately 340 m3/t of hydrocarbon. In the magma-affected area, the metamorphic grade, micropore volume, amount of gas adsorption, initial speed of gas desorption, and amount of desorption all increase. Fluid entrapment by sills usually causes the gas pressure and gas content of the underlying coal seams to increase. As a result, the outburst risks from coal seams increases as well.

Analysis of secondary migration of hydrocarbons in the Ordovician carbonate reservoirs in the Tazhong uplift, Tarim Basin, China

The process and mechanisms of secondary hydrocarbon migration in the Tazhong uplift, Tarim Basin, were investigated based on the analysis of the regional structure and by integrating geologic, hydrodynamic, and geochemical parameters. Parameters successfully analyzed included the fluid potential, fluid properties, production outputs, and diamantane index. The results indicated that hydrocarbons migrated into the Tazhong uplift from the northern part of the Manjiaer depression through a series of injection points (IPs) during four orogenies, that is, the early Caledonian (510 Ma), the late Caledonian (439 Ma), the late Hercynian–Indosinian (290 Ma), and the Yanshanian–Himalayan (208 Ma). A total of six IPs were identified at the intersections of the northeast-trending faults and the northwest-trending flower strike faults. The hydrocarbons migrated from the IPs into traps along regional trends from northwest to southeast and from northeast to southwest. The hydrocarbon migration process and patterns determined the distribution of hydrocarbon properties and production rates in the Tazhong uplift. With increasing distance from the IPs, daily hydrocarbon production decreases, and the hydrocarbons become progressively heavier and display lower gas:oil ratios.