Cracking Of Bitumen Research Articles

Complex electrical conductivity changes associated with hydrous pyrolysis maturation of the Woodford Shale

Hydrous closed-system pyrolysis experiments were performed on five pairs of chert cubes from the Woodford Shale aliquots under uniaxial confinement at various prescribed thermal maturities. These thermal maturities represent each of the phases of organic-matter (OM) catagenesis under hydrous conditions: immature kerogen at low thermal stress (125°C for 72 h), low and peak bitumen generation with increasing thermal stress (300°C and 330°C for 72 h), cracking of bitumen to oil and gas at higher thermal stresses (330°C and 360°C for 72 h), and cracking of some oil at the highest experimental conditions (400°C for 72 h). We measured the spectra of the complex electrical conductivity tensor (in the frequency range 10 mHz to 45 kHz) of these 10 aliquots to capture the effects of thermal maturation by hydrous pyrolysis. Results indicate that surface conduction of polar-rich bitumens has a significant effect on their complex electrical conductivity. The OM of a source rock is considered a negligible cause of cation-exchange capacity (CEC), whose parameters influence surface and quadrature conductivity components of the complex electrical conductivity tensor. Part of this CEC was reactivated during the hydrous closed-system pyrolysis experiments. The conspicuous absence of a decrease in electrical conductivity with bitumen and oil generation in the chert cubes recovered from the hydrous-pyrolysis experiments does not agree with the observed increases of well-log resistivity in the natural maturation of some source rocks. Contraction of OM at the contacts with mineral grains is considered a partial cause of this discrepancy, which occurs during the cooling of the experiments to room temperature when no mechanical compaction is applied. Mineral-grain supported rocks such as the chert we studied appear to be especially prone to such a phenomenon.

Evolution of organic matter and nanometer-scale pores in an artificially matured shale undergoing two distinct types of pyrolysis: A study of the Yanchang Shale with Type II kerogen

Two distinct pyrolysis experiments were performed to investigate variations in the content and composition of organic matter (OM) and their relation with the growth of nanometer-scale pores during the thermal maturation of shale. One was conducted in glass tubes under vacuum (closed system), and the other was performed in a semi-closed system in which generated oil can flow out of the system under an 80MPa pressure compressing the sample. The maturation of OM, especially the secondary cracking of residual bitumen, occurs much slower in a semi-closed than in a closed system. However, greater carbon loss (up to 6%) was shown by pyrolyzed samples in the semi-closed system relative to those in the closed system (< 3%), which is related to differences in hydrocarbon expulsion and consolidation of retained bitumen. During the main oil generation stage, declining pore volume in both systems is mainly attributed to bitumen infilling that masked some primary and secondary pores. A significant increase in total pore volume by 2.5cm3/100g was observed in pyrolyzed samples from the semi-closed system after the oil peak. In contrast, a much smaller pore growth of 1.1cm3/100g was detected in samples within the closed system. A relatively high pore pressure in a block of compressed shale, resulting from a large amount of retained bitumen, can generate, in addition to a large carbon loss, substantial pore growth in pyrolyzed samples within the semi-closed system. Current results suggest a close, but not straightforward, relationship between the transformations of OM and pore development.

Aquathermolysis of Natural Bitumen under Supercritical Conditions in the Presence of Ferrospheres

The influence of a catalytic additive – magnetic ferrospheres – on the product composition of cracking of natural bitumen from Ashal'chinskoe oilfield (4.6 wt % of fractions with IBP 200 °C) was studied. The reaction was achieved in an autoclave in the presence of a hydrogen donor (water). The addition of 10 wt % of ferrospheres was shown to favor the tar destruction and to increase the yield of light boiling fractions. The coke formation was decelerated during bitumen aquathermolysis under supercritical conditions. In aquathermolysis with ferrospheres at 500 °C, the yield of fractions IBP 360 °C increase by 12.5 %, while gas and coke yields decreased by 14.4 and 3.9 wt %, respectively, against the yields during bitumen cracking. The data on structure and group analysis of tars and asphaltenes indicate considerable destruction of the alkyl and naphthene species during aquathermolysis. Application of aquathermolysis allows heavy hydrocarbon feedstock to be processed using inexpensive and effective additives to improve considerably the conversion ratio.

Thermal cracking of Athabasca VR and bitumen and their maltene fraction in a closed reactor system

Thermal cracking of Athabasca vacuum residue (AVR) and Athabasca bitumen (AB) and their maltene fraction was investigated at 400°C in a closed system, i.e. autoclave. The effect of the following variables on the product yield and the properties of the liquid fraction and its maltene extract was evaluated: residence time, pressure of the reactor unit, stirring, temperature and asphaltenes content of the feedstock. The yield of the different fractions, the total energy consumption, the pressure buildup in the batch reactor and the °API gravity and viscosity of the liquid fraction and its maltene extract were used to evaluate the impact of a given parameter. In addition, high-temperature simulated distillation (HTSD) analysis of the liquid product and gas chromatography (GC) analysis for gas product were performed. The effect of reaction time, mixing and pressure on the yield of toluene insolubles (TI) depended on the presence of asphaltenes in the feedstock. TI yield increased at the expense of the asphaltenic fraction when reaction time, mixing and pressure increased. There is an inverse relationship between the initial asphaltenes content in the feedstock and the overall asphaltenes yield base on the parent feedstock. Moreover, increasing asphaltenes content of the feedstock did not introduce significant changes in the total energy input to the reactor.

Gas Generation during Electrical Heating of Oil Sands

Electrical heating of oil sand formations involves high temperatures, which can lead to in-situ gas generation as a result of aquathermolysis and thermal cracking of bitumen. The thermal cracking of bitumen can also lead to formation of coke at higher temperatures. Prediction of the volume of the produced gas and coke is very important in design and implementation of thermal processes dealing with high temperatures such as electrical heating and steam assisted gravity drainage with addition of oxygen. In this work a reaction kinetics model has been developed based on the experimental data of in-situ gas generation from an Athabasca bitumen sample. The kinetic parameters were estimated using the experimental data in the temperature range 360–420 °C. The results show that coke formation can be significant at higher temperatures. An important observation was that a plateau to H2S production is not expected at higher temperatures. In addition, the results show that operation at 370 °C produces a gaseous compo...

Sedimentary and residual gas geochemical characteristics of the Lower Cambrian organic-rich shales in Southeastern Chongqing, China

To study the sedimentary environment of the Lower Cambrian organic-rich shales and isotopic geochemical characteristics of the residual shale gas, 20 black shale samples from the Niutitang Formation were collected from the Youyang section, located in southeastern Chongqing, China. A combination of geochemical, mineralogical, and trace element studies has been performed on the shale samples from the Lower Cambrian Niutitang Formation, and the results were used to determine the paleoceanic sedimentary environment of this organic-rich shale. The relationships between total organic carbon (TOC) and total sulfur (TS) content, carbon isotope value (δ13Corg), trace element enrichment, and mineral composition suggest that the high-TOC Niutitang shale was deposited in an anoxic environment and that the organic matter was well preserved after burial. Stable carbon isotopes and biomarkers both indicate that the organic matter in the Niutitang black shales was mainly derived from both lower aquatic organisms and algaes and belong to type I kerogen. The oil-prone Niutitang black shales have limited residual hydrocarbons, with low values of S2, IH, and bitumen A. The carbon isotopic distribution of the residual gas indicate that the shale gas stored in the Niutitang black shale was mostly generated from the cracking of residual bitumen and wet gas during a stage of significantly high maturity. One of the more significant observations in this work involves the carbon isotope compositions of the residual gas (C1, C2, and C3) released by rock crushing. A conventional δ13C1–δ13C2 trend was observed, and most δ13C2 values of the residual gases are heavier than those of the organic matter (OM) in the corresponding samples, indicating the splitting of ethane bonds and the release of smaller molecules, leading to 13C enrichment in the residual ethane.

The origin and evolution of thermogenic gases in organic-rich marine shales

Abstract In order to better understand the generation and primary source of mature thermogenic gas in shale, and to evaluate the residual gas generation potential of the shale at different maturity levels, we performed pyrolysis experiments on an organic-rich marine shale and its kerogens prepared by artificial maturation. The results indicate that the thermal maturation of organic matter in the shale can be divided into four stages: oil generation ( 2+ hydrocarbon gases are produced during condensate and wet gas generation. The kerogen at a thermal maturity of >3.0% EasyRo still has methane generation potential. Whether or not gas generation potential of a highly mature kerogen has a commercial significance depends on its organic matter richness, thermal maturity internal and some other geological factors, such as caprock sealing property, reservoir physical property, and tectonic movement. In addition to the gas produced from kerogen cracking, gas is also generated from the secondary cracking of residual bitumen as maturation progresses. Early hydrocarbon expulsion during oil generation likely has a considerable effect on the amount and δ 13 C values of the late-generated shale gas. The lower the oil expulsion efficiency of a shale, i.e., the more retained bitumen, then the higher the productivity of post-mature shale gas and comparative enrichment of the latter in 1 2 C.

Organic matter properties and shale gas potential of Paleozoic shales in Sichuan Basin, China

In this study, Lower Paleozoic shale samples collected from Lower Cambrian Niutitang Formation, Upper Ordovician Wufeng Formation, and Lower Silurian Longmaxi Formation in different regions in the Sichuan Basin were analyzed using geochemical and petrophysical methods to characterize the difference in organic matter properties (including abundance, type and thermal maturity), pore development, mineralogy to shale gas resources potential. The studied marine shales all displayed excellent, high-quality organic matter richness and could be the strata for shale gas generation over geological time. There are four systematic geochemical and petrophysical variation trends that indicate that the overmature source rocks of the Sichuan Basin constitute a special shale gas reservoir system: (1) The measured δ13C values for sedimentary organic carbon (TOC) presents a distinct trend indicative of 13C enrichment, which indicates that the TOC may be related to the diversity of preserved phytoplankton in the different shale strata in the Sichuan Basin. This biont diversity and organism replacement process were confirmed by the biomarker distribution patterns in the sediments. (2) The bitumen “A” contents display negative correlation with sedimentary age and TOC, suggesting that most of the residual liquid hydrocarbons in those shales have been transformed into shale gas due to higher thermal maturity during the diagenetic transformation of the organic matter burial process, and the shale gas in reservoirs in those types of shales were mostly generated from the cracking of residual bitumen during a stage of relatively high thermal evolution. (3) The quartz and TOC present strongly positive relationship, suggesting that the increased quartz in most of the marine shales is a biogenic silica signal. (4) Total porosity displays a negative relationship with TOC and the quartz contents in the three Paleozoic marine shales, suggesting that re-precipitated pyrobitumen created by oil cracked to gas in overmature source rocks could be the reason leading to the lowest porosity and smaller pores in the most aged but most TOC-abundant shales. Skewing toward smaller pores will reduce the pore volume and result in larger internal surface areas and greater sorption energies, which should reduce the productive capacity of shale gas.

Catalytic bitumen cracking in sub- and supercritical water

The bitumen cracking reaction under sub- and supercritical water environments in H2 or N2 atmosphere using activated carbon (AC) supported nickel catalyst was studied. The sub- or supercritical water provided a unique homogeneous, acidic reaction system for the bitumen cracking reaction, which obviously promoted the bitumen conversion and selectivity of the middle distillates (kerosene and gasoline), and restrained the formation of carbon deposition, if compared with the conventional pyrolysis reaction without water addition. Moreover, the active in-situ H2 source was provided by the water–gas shift reaction in the sub- and supercritical water environment, thereby enhancing the catalytic activity of bitumen cracking.

Role of water and fine solids in onset of coke formation during bitumen cracking

The aim of this study was to examine the effect of water and fine solids on coke formation during thermal cracking of a residue fraction from vacuum distillation (Athabasca vacuum tower bottoms) and Athabasca bitumen froth. Experiments were conducted in a batch reactor with 0–33.3wt.% water at 410°C for up to 80min to measure the time of onset of coke formation, total coke yield as a function of time, and conversion of vacuum residue. Removal of fine solids significantly shortened the onset time of coke formation, but the addition of water had no significant impact on onset time. The yield of cracked products, as determined by simulated distillation, was insensitive to the presence of water and fine solids. Based on the findings from this study, it was concluded that residual fine solids have a beneficial effect on thermal upgrading as they delayed the onset of coke formation, while water has little impact within the tested concentration range of 0–33wt.% water.

Experimental study on the gas generation processes of lacustrine and marine shales in North China: Source implications for shale gas

Using a high pressure, semi-closed thermal simulation system, two organic-rich lacustrine and marine immature shales from North China were investigated to probe the dynamic processes and potential for the gas generation throughout the oil-gas window. The results identified at least two processes during gas generation, as revealed by changes of the gas dry coefficient (C1/ΣC1-5%) and carbon isotopic composition of methane (δ13Cmethane). The first process is associated with kerogen thermal degradation and occurs during the main phase of oil generation, showing an increasing trend of the dry coefficient and δ13Cmethane. The second process begins during the late phase of oil generation, accompanied by increasing yields of wet gas components and 13C depleted methane. Due to the lack of aliphatic carbon in kerogen in the highly to over mature stage, as demonstrated by FTIR analyses, the second process is mainly related to the cracking of kerogen-generated bitumen which is retained in the shale.The hydrogen content, a key parameter for petroleum generation, is then used to quantitatively evaluate the gas generation potential from kerogen thermal degradation and retained-bitumen cracking. Mass balance calculations show that kerogen-generated bitumen that is retained in lacustrine and marine shales is estimated to contribute 30% of the total gas yields at the stage of 1.5–2.0% Ro. This result is consistent with the theoretical calculations from Xia et al. (2013) and has important implications for the shale gas sources, and further the shale gas resource assessments before exploration in shale-gas petroleum systems.

Contribution of insoluble organic matters to late gas generation from mature Salgan Shale

We used bulk rock (BR), solvent extracted BR, isolated kerogen, and bitumen from a mature Salgan Shale as reactants during gold-tube simulation experiments to investigate the contribution of insoluble kerogen to late-stage gas generation at high thermal stress. We measured the gas yields and stable carbon isotopic compositions of methane, ethane, and propane. The high methane yield ([Formula: see text] methane yield at 600°C) in BR series demonstrated the huge potential for late methane generation. The maximum methane yield (normalized to total organic compound) in the bitumen series is twice more than that in the BR series. This phenomenon is interpreted by the high availabilities of hydrogen. However, bitumen only takes up a very small proportion of the overall BR, and generated gas from bitumen cracking is limited. Thus, in mature Salgan Shale, kerogen cracking contributes more hydrocarbon gases than that from bitumen cracking. Meanwhile, generated gas from kerogen cracking is very dry and enriched in the [Formula: see text] isotope, whereas gas cracked from retained oil is much wetter and associated with much lighter [Formula: see text] values. Mature kerogen cracking is also helpful to enlarge the shale gas reserve at high maturities especially when the retained oil is limited.

Composition of Pre-ozonated High-Sulfur Natural Bitumen Cracking Products

The results analysis of fractional and material composition of the cracking products of Ashalchinskoye and Karmalskoye bitumen deposits was presented in this work. The effect of bitumen ozone-oxygen mixture pretreatment followed by cracking on thermolysis processes was investigated. It was shown that molecules of resins and asphaltenes containing large amounts of aliphatic fragments in its structure readily undergo thermal decomposition to form additional distillate fractions. Low content of aliphatic fragments leads to aromatization of the naphthenic cycles in the molecule of resins and asphaltenes, the thermal degradation reactions proceed in high yields of gas and coke.

Response of the microstructure of bitumen upon stress–damage initiation and recovery

The occurrence of discrete cracking of bitumen and asphalt is difficult to observe/analyse mainly because of the viscous nature of the bitumen binder. Many techniques simply do not have the required resolution or analysis techniques do not get a good response from the highly dissipative bitumen. In this study, an attempt is made to visualise failure development under straining conditions in bitumen with the use of an in situ tensile tester combined with atomic force microscopy. From the experiments, it was observed that cracks or strain localisations occur in the perpetua phase though only significantly for aged binder (i.e. more than six months at room temperature). Furthermore, the locations of these cracks or strain localisations occur on the edges of the more rigid peri phase and were oriented in the direction of tension. This is a clear indication that the bitumen's microstructure does affect homogeneity of the internal stress and strain fields and effectively causes non-homogeneous straining and even localisation in regions where stress concentrations are present. Furthermore, the recovery of the strain localised zones was studied. The strain localised zones completely recovered in the course of several hours.

On the Role of Water in Natural-Zeolite-Catalyzed Cracking of Athabasca Oilsands Bitumen

Water addition to natural-zeolite-catalyzed reactions significantly improves cracking of oilsands bitumen compared to analogous reactions in the absence of water. We report that the addition of 3% water to the catalyzed cracking reactions results in samples with lower viscosities and average molecular weights, less residue, olefin, and coke formation, and higher C2+ gas production compared to analogous reactions in the absence of water. Our study suggests that untreated natural zeolites undergo self-acidification by hydrolysis reactions in the presence of water. Fourier transform infrared spectroscopy and solid-state NMR analyses detected the presence of acid −OH groups on the raw untreated chabazite and clinoptilolite surfaces that are capable of supplying protons to initiate carbocation reactions. Stable isotopic mass spectrophotometric analyses on bitumen on D2O-doped catalytic reactions confirm up to ∼56% hydrogen incorporation from added water to the liquid products. Aromaticity and proton and deuter...

In Situ Upgrading of Athabasca Bitumen Using Multimetallic Ultradispersed Nanocatalysts in an Oil Sands Packed-Bed Column: Part 2. Solid Analysis and Gaseous Product Distribution

Thermal cracking of Athabasca bitumen was carried out in an oilsand packed-bed column, in the presence and absence of in situ prepared trimetallic nanocatalysts at a pressure of 3.5 MPa, residence time of 36 h, and temperatures of 320 and 340 °C. In this part of the study, the effects of reaction severity (time and temperature) as well as the presence of nanocatalysts in packed media on solid and gaseous products were investigated. Results showed that the presence of trimetallic nanocatalysts enhanced the hydrogenation reactions and, consequently, led to significant reduction of coke formation (51.3%) and CO2 emission reduction. Further, the analysis of the gaseous products and deposited solids confirmed the previous findings reported in part 1 (10.1021/ef401716h) of this study. The accumulative volume of coke precursor gases, such as ethylene and propylene, increased with the reaction severity. However, reaction severity has no significant effect on the atomic metallic ratios (metal/total metal) of the e...

Bitumen Cracking in Supercritical Water Upflow

Bitumen was cracked in a high-pressurized water upflow at 440 °C and 10, 25, and 30 MPa using continuous stirred tank reactor. At 30 MPa, which was the optimal dispersion condition, the highest liquid yield, lowest coke, highest conversion, and heaviest liquid products were obtained. Even at optimal conditions, all the asphaltene (AS) could not be entrained with the supercritical water (SCW) upflow; thus, the product oil contained <0.5% of AS. This means that bitumen cracking in the SCW upflow was a combined process of thermal upgrading and deasphalting.

Composition of Initiated Cracking Products of High-sulfur Natural Bitumen

The analysis of the cracking products of bitumen Karmalskoye deposits (the content of fractions boiling up to 200°C 6,7% wt.) has been performed. The influence of power plant coal ash microspheres on orientation of cracking bitumen components is stated. Bitumen cracking leads to significant yields of gas and coke for more than 20% wt. and destructions of all components. The initiated bitumen cracking in the presence of 10% microspheres at cracking temperature 450°C leads to reduction of gas and coke yields and increase in fractions of ibp (initial boiling point) –360°C at 10% wt. in comparison with products of the thermal bitumen cracking. The analysis of composition and amount of sulfur compounds in initial bitumen and the cracking products in the various conditions has shown that the thermal cracking leads to increased homologues benzothiophene contents due to partial destruction of resins, and to decrease in the content of homologues dibenzothiophene.

Interaction of coal and oil in confined pyrolysis experiments: Insight from the yield and composition of gas hydrocarbons

Isothermal pyrolysis experiments were performed for coal alone, oil alone and coal plus oil with oil/coal ratios ranging from 0.0065 to 0.1995 at 305 °C and 50 MPa for 72 h in confined systems (gold capsules). The results of these experiments reveal the interaction between coal and oil, demonstrating that oil retards the generation of gas hydrocarbons from coal cracking while coal accelerates oil cracking into gas hydrocarbons. The yields of gas hydrocarbons vary greater with oil/coal ratio in the experiments of coal B plus oil than coal A plus oil because coal A has a higher HI value than does coal B. Oil cracking rate could increase by up to 10 or even higher times in the experiments of coal plus oil compared with oil alone, deduced from the yields and chemical compositions of gas hydrocarbons. This result suggests that gas hydrocarbons, especially wet gases were largely generated from the cracking of oil or extractable bitumen in the experiments of coal plus oil with oil/coal ratio higher than 0.1.

Catalytic Cracking Reaction of Heavy Oil in the Presence of Cerium Oxide Nanoparticles in Supercritical Water

Catalytic cracking of Canadian oil sand bitumen in supercritical water was performed to clarify the effect of CeO2 nanoparticles. The cracking was performed at 723 K to promote a redox reaction between the water, bitumen, and catalyst for the production of hydrogen and oxygen. As the catalyst, CeO2 with two different morphologies was employed because the redox reaction of CeO2 with water and organics is expected and its activity can be controlled by its structure. In this study, two roles of water were considered as well. Water is attractive as a high potential medium with low dielectric constant and density at near the critical point (374 °C, 22.1 MPa) that allows formation of highly crystalline smaller metal oxides particles. However, the chemical effects of water are investigated with heavy oil catalytic cracking. Transmission electron microscopy images indicated that CeO2 nanoparticles with cubic and octahedral shape were synthesized using a plug-flow reactor under hydrothermal conditions. The particles sizes were 8 and 50 nm for cubic and octahedral CeO2, respectively. At 773 K, it was found that the oxygen storage capacity (OSC) of the cerium oxide nanoparticles with cubic {100} facets was nearly 3.4 times higher than that of the cerium oxide nanoparticles with octahedral {111} facets. Heavy oil fractions of bitumen were cracked in a batch-type reactor at 723 K in order to produce as much light oil as possible, and the effect of the catalyst loading and reaction conditions on the conversion rate and coke formation were investigated. As a result, it was demonstrated that it is possible to obtain a high conversion rate by increasing the exposed surface area and reducing the particle size of the catalyst. The highest conversion was obtained in the presence of 20 mg loading of cubic CeO2 nanoparticles (8 nm) with reaction time of 1 h.