Secondary Hydrocarbon Research Articles

Methyl radical chemical reactions on a tungsten surface

In this paper an interaction of the inner dome surfaces of the International Thermonuclear Experimental Reactor with a gas mixture containing hydrocarbon radicals has been modelled. To study the processes of transport and deposition of methyl radicals in a C x H y –H2–H (x=1−3, y=1−6) flow, a stream technique has been used. A radiofrequency inductive discharge initiated in methane at the inlet of a quartz tube was a source of methyl and hydrogen atoms. Methyl radicals were transported by a gas flow that passed through cylindrical tungsten inserts and were deposited on the tube wall, on silicon samples and on tungsten samples, forming polymer-like hydrogenated amorphous carbon films. It has been shown that at the tungsten insert temperature increases to 420 K, and carbon deposition rate decreased significantly. However, in the gaseous phase the secondary hydrocarbon species accumulated and condensed on the tungsten surface at a temperature lower than 340 K.

GIS-based modeling of secondary hydrocarbon migration pathways and its application in the northern Songliao Basin, northeast China

Hydrocarbon migration pathways are the linkage between hydrocarbon source areas and accumulation sites. Modeling accurately the pathways of hydrocarbon migration is of important significance in determining the location of favorable petroleum exploration targets. In this paper, GIS-based modeling algorithms are presented for searching the pathways of secondary hydrocarbon migration by considering the geologic mechanisms. These algorithms are constructed on a raster digital elevation model (DEM) of the top boundary of a carrier bed, in which secondary migration occurred. On the DEM, a 3×3 pixel sized window is used for searching. The center of the search window is initially assumed at a point on the boundary of a hydrocarbon source area, from which the secondary hydrocarbon migration starts. The altitude values in the eight adjoining pixels enclosing the central pixel of the search window are compared, and the pixel with an altitude value not only larger than the central pixel but also the largest of the eight surrounding pixels is the next target pixel where the search window will move to. Each searched path will terminate at either a convex point, which indicates the existence of a trap for hydrocarbon accumulation, or a point on the boundary of the DEM, which suggests that the pathway of hydrocarbon migration extends outside the DEM. In addition, a concourse point of two paths is also considered as a termination point of either path. The algorithms were successfully applied in the modeling of the secondary migration pathways in the northern Songliao Basin, northeast China. The modeled results matched well with drilling data, suggesting the robustness of the algorithms.

Thermal Evolution of Organic Matter and Secondary Hydrocarbon Generation from Upper Paleozoic Coal Deposits in Northern China

Abstract The metamorphism and hydrocarbon generation from the Upper Paleozoic coal-bearing strata in Northern China have been widely studied by Chinese geologists since the 1990s. Based on a large amount of data of R o values, combined with geological background, we have systematically analyzed the thermal evolutionary characteristics of organic matter and the stages of hydrocarbon generation from the Permo-Carboniferous coal deposits and discussed the condition of secondary hydrocarbon generation. The distribution range of secondary hydrocarbon generation in Northern China is thus determined. It is shown that the coal ranks of the Upper Paleozoic coal deposits are higher in the southern and western belts than those in the northern and eastern belts. Really significant secondary hydrocarbon generation is mainly related to the thermal evolution of organic matter during the Himalayan Period. Profitable areas for secondary hydrocarbon generation should be buried at 3000–4000 m up to the present. Maturity of the Permo-Carboniferous source rocks is not very high. It is suggested that the Bohai Bay depression is favourable for secondary hydrocarbon generation and has good oil and gas prospects.

Exploration Potential of Marine Source Rocks Oil‐Gas Reservoirs in China

Abstract: So far, more than 150 marine oil‐gas fields have been found onshore and offshore about 350. The marine source rocks are mainly Paleozoic and Mesozoic onshore whereas Tertiary offshore. Three genetic categories of oil‐gas reservoirs have been defined for the marine reservoirs in China: primary reservoirs, secondary reservoirs and hydrocarbon‐regeneration reservoirs. And three exploration prospects have also been suggested: (1) Primary reservoirs prospects, which are chiefly distributed in many Tertiary basins of the South China Sea (SCS), the Tertiary shelf basins of the East China Sea (ECS) and the Paleozoic of Tarim basin, Sichuan basin and Ordos basin. To explore large‐middle‐scale even giant oil‐gas fields should chiefly be considered in this category reservoirs. These basins are the most hopeful areas to explore marine oil‐gas fields in China, among which especially many Tertiary basins of the SCS should be strengthened to explore. (2) Secondary reservoirs prospects, which are mainly distributed in the Paleozoic and Mesozoic of the Tarim basin, Sichuan basin, Qiangtang basin and Chuxiong basin in western China, of which exploration potential is less than that of the primary reservoirs. (3) Hydrocarbon‐regeneration reservoirs prospects, which are chiefly distributed in the Bohai Bay basin, North Jiangsu‐South Yellow Sea basin, southern North China basin, Jianghan basin, South Poyang basin in eastern China and the Tarim basin in western China, of which source rocks are generally the Paleozoic. And the reservoirs formed by late‐stage (always Cenozoic) secondary hydrocarbon generation of the Paleozoic source rocks should mainly be considered to explore, among which middle‐small and small oil‐gas fields are the chief exploration targets. As a result of higher thermal evolution of Paleozoic and Mesozoic source rocks, the marine reservoirs onshore are mainly gas fields, and so far marine oil fields have only been found in the Tarim basin. No other than establishing corresponding marine oil‐gas exploration and development strategy and policy, sufficiently enhancing cognition to the particularity and complexity of China's marine petroleum geology, and applying new thoughts, new theories and new technologies, at the same time tackling some key technologies, it is possible to fast and effectually exploit and utilize the potential huge marine oil‐gas resources of China.

Secondary hydrocarbon generation potential from heavy oil, oil sand and solid bitumen during the artificial maturation

Secondary hydrocarbon generation potentials from natural bitumen, oil sand and heavy oil, representing different residual oil accumulations, were determined by artificial maturation in a closed pyrolysis system. Simulated results indicate that their thermal behavior and reactivity are similar to those of kerogen, and that they can generate hydrocarbons once subjected to suitable geological processes. Overall differences in oil and gas generation potentials among the samples result from differences in the chemical structure of precursor components, physical compaction status, and mineral matrices. Hydrogen rich precursors, such as oil sand and heavy oil, have greater potential to generate hydrocarbons than hydrogen poor ones. Naturally compacted oil sand has slightly higher conversion efficiency than artificially compacted heavy oil as indicated by lower residual bitumen content. However, total gas and liquid oil recovery from oil sand is lower than from heavy oil due to the poor release of pyrolytic products from well compacted and cemented networks in the experiments. Mineral matrices of previous oil deposits also affect further hydrocarbon generation potential. Carbonate matrices inhibit total oil and gas generation, which consequently retains high gas potential at the postmature stage. Traditional oil generation models mainly consider the thermal alteration of kerogen; this study provides supplemental information for superimposed basins where previous oil accumulations may have been destroyed and reburied to serve as secondary sources of oil and gas. Consideration of previous oil residues as potential source rock allows better estimates of available oil resources and the risks associated with their exploration.

EFFECTS OF HYBRID REBURNING/SNCR STRATEGY ON NOX/CO REDUCTION AND THERMAL CHARACTERISTICS IN OXYGEN-ENRICHED LPG FLAME

From the view of the environmental protection against the usage of fossil fuels, a great amount of effort has been exerted to find an effective method that is not only for pollutant reduction, but also for higher thermal efficiency. In order to enhance combustion efficiency, oxygen-enriched combustion is used by increasing the oxygen ratio in the oxidizer. However, since the flame temperature increases, NOx formation in the furnace seriously increases for low oxygen enrichment ratio. In this case reburning is a useful technology for reducing nitric oxide through injection of a secondary hydrocarbon fuel. In this article, an experimental study has been conducted to evaluate the hybrid effects of reburning and selective non-catalytic reaction (SNCR) on NOx/CO formation and also to examine heat transfer characteristics in an oxygen-enriched LPG flame. Experiments were performed in flames stabilized by a co-flow swirl burner, which was mounted at the bottom of the furnace. Tests were conducted using LPG gas as the reburn fuel as well as the main fuel. The effects of reburn fuel fraction and injection location of the reburn fuel as well as SNCR agent were studied. The paper reports data on flue gas emissions, temperature distribution in the furnace and various heat fluxes at the wall for a wide range of experimental conditions. At steady state, the total heat flux from the flame to the wall of the furnace has been measured using a heat flux sensor. Temperature distribution and emission formation in the furnace have also been measured and compared. Overall temperature in the furnace, heat fluxes to the wall and NOx generation were observed to increase with low level oxygen-enriched combustion, but due to its hybrid effects of reburning and SNCR, NOx and CO concentrations in the exhaust have decreased considerably

Types, Evolution and Pool-Controlling Significance of Pool Fluid Sources in Superimposed Basins: A Case Study from Paleozoic and Mesozoic in South China

ABSTRACT Having multiple tectonic evolution stages, South China belongs to a superimposed basin in nature. Most marine gas pools became secondary pools. The pool fluid sources serve as the principal pool-controlling factors. On the basis of eight typical petroleum pools, the type, evolution in time-space, and the controlling of petroleum distribution of pool fluid sources are comprehensively analyzed. The main types of pool fluid sources include hydrocarbon, generated primarily and secondly from source rocks, gas cracked from crude oil, gas dissolved in water, inorganic gas, and mixed gases. In terms of evolution, the primary hydrocarbon was predominant prior to Indosinian; during Indosinian to Yen-shanian the secondary gas includes gas cracked from crude oil, gas generated secondarily, gas dissolved in water, and inorganic gas dominated; during Yenshanian to Himalayan the most fluid sources were mixed gases. Controlled by pool fluid sources, the pools with mixed gas sources distributed mainly in Upper Yangtze block, especially Sichuan ( ) basin; the pools with primary hydrocarbon sources distributed in paleo-uplifts such as Jiangnan ( ), but most of these pools became fossil pools; the pools with secondary hydrocarbon source distributed in the areas covered by Cretaceous and Eogene in Middle-Lower Yangtze blocks, and Chuxiong ( ), Shiwandashan ( ), and Nanpanjiang ( ) basins; the pools with inorganic gas source mainly formed and distributed in tensional structure areas.

Hydrocarbon migration characteristics of the Lower Cretaceous in the Erlian Basin

The paper systematically analyzes the hydrocarbon migration characteristics of the Lower Cretaceous in the Erlian Basin, based on the geochemical data of mudstone and sandstone in the main hydrocarbon-generating sags. (1) The source rocks in K1ba and K1bt1 are estimated to be the mature ones, their hydrocarbon expulsion ratio can reach 32%–72%. The Type-I sags in oil windows possess good hydrocarbon generation and expulsion conditions, where commercial reservoirs can be formed. (2) According to the curves of the mudstone compaction and evolution of clay minerals, the rapid compaction stage of mudstones is the right time of hydrocarbon expulsion, i.e., primary migration. (3) The timing between hydrocarbon generation and expulsion is mainly related to the accordance of the oil window and the rapid compaction stage of mudstones in the hydrocarbon generation sags of Type-I. That forms the most matching relation between hydrocarbon generation and migration. (4) The faults and unconformities are the important paths for the secondary hydrocarbon migration. Especially, the unconformity between K1ba and K1bt1 has a favorable condition for oil accumulation, where the traps of all types are the main exploration targets. (5) Hydrocarbon migration effect, in the Uliastai sag, is most significant; that in the Saihan Tal and Anan sags comes next, and that in the Bayandanan and Jargalangt sags is worst.

무촉매 환원법이 적용된 응용 재연소 방법에 의한 NOx와 CO의 저감 효과

From the view of the environmental protection against the use of fossil fuels, the great of efforts have been exerted to find an effective method which is not only pollutant reduction but also high thermal efficiency. Reburning is a useful technology in reducing nitric oxide through injection of a secondary hydrocarbon fuel. In this paper, an experimental study has been conducted to evaluate the hybrid effects of reburning and selective non-catalytic reaction (SNCR) on NOSUBx/SUB/CO reduction from oxygen-enriched LPG flame. Experiments were performed in flames stabilized by a co-flow swirl burner, which was mounted at the bottom of the furnace. Tests were conducted using LPG gas as main fuel and also as reburn fuel. The paper reported data on flue gas emissions, temperature distribution in furnace and various heat fluxes at the wall for a wide range of experimental conditions. Overall temperature in the furnace, heat fluxes to the wall and NOSUBx/SUB generation were observed to increase by oxygen-enriched combustion, but due to its hybrid effects of reburning and SNCR, NOSUBx/SUB/CO concentration in the downstream has considerably decreased.

Influence of fault map resolution on pore pressure distribution and secondary hydrocarbon migration; Tune area, North Sea

AbstractPressure and hydrocarbon migration modelling was carried out in the Tune Field area, Viking Graben, offshore Norway. The pressures are considered to be controlled by compartments bounded by mapped faults. Two different interpreted fault maps at the top reservoir level (Brent Group) are used as input to the modelling. First, a low‐resolution fault map is used, with only the large faults interpreted, and next, both large and small faults are included. The simulations show high overpressures generated in the western area, in the deeper part of the Viking Graben, and hydrostatic in the eastern areas. A sharp transition zone results from using the low‐resolution fault map in the simulations. Small N–S striking faults situated in between the wells have to have higher sealing capacity than expected from juxtaposition analysis alone, to be able to match the overpressures measured in well 30/5‐2 and 30/8‐1S in the Tune Field, and well 30/8‐3 east of Tune. The intermediate pressure in the western part is probably related to flow in the deeper parts of the sedimentary column in the compartment, where well 30/8‐3 is situated. The secondary oil migration models show that overpressures have major effects on the migration pathways of hydrocarbons. The level of detail in the fault interpretation is important for simulation results, both for pressure distribution and for hydrocarbon migration.

Petrological changes occurring in organic matter from Recent lacustrine sediments during thermal alteration by Rock-Eval pyrolysis

This study characterizes the petrological changes occurring in an organic matter assemblage of Recent lacustrine sediments from Alberta, Canada, during the various steps of Rock-Eval 6 ® pyrolysis. The results indicate that the organic compounds released during pyrolysis at low temperatures of up to 300 °C (mainly S1-compounds) are most likely derived from a ‘stain-like’ amorphous organic matter, including pigments and oils/lipid products with strong, multicolored VIS fluorescence. The fluid characteristics of the thermally labile S1-compounds possibly account for the significant grain surface coating by the organic matter. Thermal alteration of sediments at 300 °C results in the transformation of some alginite and other macerals into a secondary product of blue–green fluorescing bitumen, which migrates into available free spaces. The release of S2-compounds during high temperature pyrolysis (from 300 to 650 °C) causes severe alterations in the morphology of the liptinitic organic matter. A bright yellow fluorescence that appeared at this stage is likely due to thermal transformation of bitumen produced in S1 pyrolysis and other liptinitic macerals into an “oily-material”, which fills cell lumens and becomes incorporated into the mineral matter. Neither the rapid rate of heating nor the sample residence time during Rock-Eval pyrolysis are sufficient for complete thermal destruction of the secondary hydrocarbon and bitumen products produced in the sample.

3-D seismic geomorphology: Insights into fluvial reservoir deposition and performance, Widuri field, Java Sea

Three-dimensional seismic geomorphology provides an indication of a reservoir's internal and external architecture. This furthers an understanding of depositional processes and allows a prediction of fluid flow during hydrocarbon production. Seismic images of four fluvial reservoirs from Widuri oil field show a range of features related to point-bar accretion and stacking pattern. Lateral variations in reservoir quality and thickness follow scroll-bar patterns associated with lateral migration of a moderate- to high-sinuosity meandering river. These variations control fluid flow during primary and secondary hydrocarbon recovery. Interpreted bar and abandoned channel dimensions, compared with meander map form and wavelength, are consistent with observations of modern-day examples, which provides confidence in the depositional model. The high seismic resolution of the Widuri reservoirs provides useful analogs for other subsurface reservoirs from similar depositional environments.

Kinetic study of the hydrocarbon generation from Upper Paleozoic coals in Ordos Basin

Kinetic parameters were characterized for the formation of the C1—C5 hydrocarbons generating from Taiyuan and Shanxi coal in the Upper Paleozoic of the Ordos Basin, through pressurized simulation experiment designed for the kinetic study of hydrocarbon generation. Based on the palaeogeothermal evolution of the Upper Paleozoic strata in the Ordos Basin, the formation and evolution of gas from Taiyuan and Shanxi coal in the eastern and central regions of the Ordos Basin were reproduced, and it is suggested that large scale secondary hydrocarbon generation does not exist during the uplifting and cooling process of the basin at the end of Early Cretaceous. Some of the factors affecting the behavior of the coal-generated gas were also discussed, and it is emphasized that the most fundamental element determining the hydrocarbon generation behavior is the characteristic of the precursor hydrocarbon-source rock.

A modified alternating‐direction finite volume method for modeling secondary hydrocarbon migration and accumulation processes

AbstractWe present a finite volume method for the coupled systems of nonlinear partial differential equations arising in secondary hydrocarbon migration and accumulation processes in basin modeling. We propose a modified alternating direction implicit splitting acceleration technique to solve the scheme in an effective and robust manner. We apply the scheme to simulate model problems with clear physical features and to secondary migration and accumulation problems in real petroleum reservoirs. The numerical experiments show that the scheme is very robust and generates stable and physically reasonable numerical results, even in the extremely long time period that ranges from millions of years to tens of millions of years. This clearly shows the strong potential of the method developed. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 254–270, 2003

Kinetic simulating experiment on the secondary hydrocarbon generation of kerogen

Kinetic simulating experiment on the secondary hydrocarbon generation of kerogen

Deposition of Diamond-Like Carbon Film in a Closed-Space CH4 RF Plasma

Deposition of diamond-like carbon (DLC) film and mass spectrometry measurements were carried out in a closed-space CH4 rf (13.56 MHz) plasma (without both gas injection and vacuum pumping during the process). At pressures less than 0.6 Torr, the thickness of the DLC film deposited increased with increasing elapsed deposition time, and reached a maximum value, but after this the film thickness started to decrease, which was considered to be caused predominantly by ion-induced sputter etching. The maximum film thickness appeared at larger elapsed time for higher deposition pressure. The mass concentrations of hydrocarbon ions indicated anomalous behavior at early deposition times, but those of higher hydrocarbon ions are clearly increased at the point where the film thickness started to decrease. These results suggested that the ratio of precursor CH3al density to the total hydrocarbon ion density (ΦCH3/Φion in the CH4a was an important factor for the carbon film formation, and when this ratio reduced to a certain critical value with increasing elapsed deposition time, the deposited film was then re-etched predominately by the secondary higher hydrocarbon ions. At 1.0 Torr where a polymer-like soft carbon film was deposited, such re-etching of the deposited film was not observed.

Kinetic simulating experiment on the secondary hydrocarbon generation of kerogen

The kinetic parameters of generation have been obtained for different hydrocarbon classes, including methane, C2-C5 gas hydrocarbons, C6-C13 light hydrocarbons and C13+ heavy hydrocarbons, and vitrinite reflectance (R°) by the kinetic simulating experiment of kerogen cracking. Then, combined with the detailed geology of Sichuan Basin, the effective gas-generating intensity of the Lower Cambrian source rock is approximately estimated by applying these parameters.

NEW DEVELOPMENTS IN THE PRE‐RIFT PROSPECTIVITY OF THE ERITREAN RED SEA

Northern, central and southern Africa is covered by great thicknesses of Upper Palaeozoic and Mesozoic fluvio‐deltaic and marine siliciclastics, which include important source rocks, reservoirs and seals. In the Eritrean Red Sea, the importance of these rocks has not yet been properly recognised.The Red Sea initially formed by rifting of the Afro‐Arabian continent in Oligo‐Miocene times. Palaeozoic and Mesozoic rocks were downthrown into the resultant Gulf of Suez/ Red Sea Graben and were rapidly buried by syn‐ and post‐rift sediments. In the Eritrean Red Sea area, pre‐rift rocks are now only exposed in the Danakil Alps at the Straits of Bab el Mandab, on the Eritrean Plateau, in the coastal lowlands north of Massawa, and in isolated outcrops in Ethiopia.The authors believe that an as‐yet untested pre‐rift “play” is to be found in the Eritrean Red Sea contiguous with the Danakil Alps. In addition, syn‐ and post‐rift “plays” cannot be ruled out in this area. The combination of newly‐mappedpre‐salt structures, containing Jurassic source rocks and Jurassic and Cretaceous reservoir sandstones and carbonates overlain by Tertiary elastics and/or salt, embodies the primary hydrocarbon entrapment model in the area. Secondary hydrocarbon “plays” centre on deformed Miocene siliciclastic seauences in proximity to salt diapirs.

Exhumed Hydrocarbon Traps in East Greenland: Analogs for the Lower-Middle Jurassic Play of Northwest Europe

Four exhumed hydrocarbon traps crop out in the Traill O region of East Greenland, each at the footwall crest of a fault-block formed during Early Cretaceous rifting. Former oil accumulations are indicated by a pore fill or pore lining of solid bitumen within the Jurassic sandstone-dominated Vardekloft and Olympen formations. The Vardekloft Formation is divided into an undated fluvial-dominated lower unit (0-520 m) and a Bajocian-Callovian upper unit (65-1020 m) deposited in a shallow-marine environment. The Oxfordian Olympen Formation (0-250 m) contains shallow-marine and fluviodeltaic deposits. The sandstones are dominantly quartzarenites, and petrographic fabrics, such as dissolved feldspar, late quartz cement, and stylolites, are consistent with burial depths in excess of 2.5 km. Porosities ranged from 7 to 27% (generally about 20%, about one-half of which was primary), and permeabilities ranged from 1 to 622 md, prior to the formation of solid bitumen. The distribution of solid bitumen in each trap can be mapped out, allowing sealing elements and original oil-water contacts to be defined. Three of the four exhumed traps (Mols Bjerge, Laplace Bjerg, and Bjornedal) were simple one-seal structural traps. Conformable Upper Jurassic mudstone, unconformable Albian-Cenomanian mudstone, and normal faults are the three top-sealing elements. The fourth (Svinhufvuds Bjerge) was a poly-seal trap with a combined top-seal and a low-side fault closure. Preliminary estimates of the volume of original oil in place within these structures range from 0.2-1.1 billion bbl for the Mols Bjerge trap to 5.3-11.9 billion bbl for the Bjornedal trap. These estimates are prone to large errors, due to uncertainties in estimating original trap geometry, hydrocarbon saturation, and net/gross ratio, and in the understanding of volume changes of hydrocarbon in each trap during thermal degradation of the oil. The Upper Jurassic Bernbjerg Formation is the only known potential source rock in the region, which would require a drainage distance of less than the fault-block spacing to fill the largest of the traps. Secondary hydrocarbon migration into these traps occurred between the Cenomanian (age of the youngest sealing element) and early Eocene to late Oligocene (when widespread volcanism and sill intrusion resulted in thermal degradation of the oil). Each of these structures is relatively well exposed and accessible; we believe that they will provide excellent analogs for studies of enhanced recovery from the mature Lower-Middle Jurassic oil fields of Northwest Europe.

HYDRODYNAMICS AND FAULT SEAL ASSESSMENT IN THE VULCAN SUB-BASIN, TIMOR SEA

The study of hydrodynamics sheds light on the current day fluid flow regime of traps of different integrity and on the mechanisms leading to seal breach. It also provides insights into potential migration pathways and zones of secondary hydrocarbon accumulation. This is a preliminary hydrodynamic investigation carried out on a few selected wells in the Vulcan Sub-basin from high, moderate and low integrity traps, referred to here as HIT, MIT and LIT respectively (after O'Brien et al, 1996). The fields sampled include East Swan (LIT), Skua and Jabiru (MIT) and Montara and Oliver (HIT). The findings of this study suggest a trend between trap type and current day fluid flow. The best result was obtained for Skua-2, where pressure testing was conducted over the bounding fault for the field, indicating high integrity. Some wells showed upward head gradients, such as East Swan-2; others showed a low or no vertical gradient, such as Jabiru-1 A,−2, −3, −10 and Oliver-1. There was general agreement between the flow direction and the conductivity of the faults, as indicated by mud loss data. Preliminary potentiometric surface mapping of Jabiru indicated lateral flow, controlled by production, and hydraulic communication within the faulted reservoir. Wellbore hydrodynamics and potentiometric surface mapping of the reservoir heads on a regional scale promise to give indications of major structural controls on flow as well as secondary migration pathways.