Total Hydrocarbon Gas Research Articles

Effective reservoir identification and sweet spot prediction in Chang 8 Member tight oil reservoirs in Huanjiang area, Ordos Basin

Abstract The Chang 8 reservoir of the Huanjiang Oilfield in the Ordos Basin is a tight sandstone reservoir with poor reservoir physical properties and uneven oil distribution. In this study, the effective reservoirs developed on a large scale under the condition of horizontal well volume fracturing technology of the Chang 8 Member was identified based on the data of core observation, experimental analysis, logging, oil test, and production dynamics, and the identification standard of effective reservoirs in terms of reservoir physical properties, oil content, and comprehensive logging characteristics of gas logging was established. This scheme allows for a thorough identification of the effective reservoirs for horizontal well development in tight sandstone reservoirs. The findings indicate that the study area’s tight oil resources can be successfully produced. The well logging results show that the oil-bearing property of sand bodies with oil stains is better than that of oil spots. The bottom limit of the acoustic wave time difference is 210 μs/m, the permeability is 0.03 mD, the porosity is 6.0%, the rock resistivity is 30 Ω m, and the total hydrocarbon gas measurement value exceeds five times the baseline. At the same time, the total oil thickness is greater than 6 m, and the thickness of a single sand body is above 4 m. We have defined the lower limit standard of high-efficiency reservoir of Chang 8 tight oil in L289 block of Huanjiang oilfield. According to the analysis of oil-bearing property, comprehensive logging display, and reservoir thickness, the geological “sweet spots” is optimized to provide reference for subsequent mining. Through comparative analysis, the rules and trends are found to provide a basis for selecting mining strategies. With the help of technical means such as numerical simulation and geological modeling, the prediction accuracy and decision-making effect are improved. By clarifying the lower limit standard of reservoir, optimizing geological “sweet spots” and avoiding risk areas, the mining efficiency is improved and the cost is reduced, which provides reference for similar oilfield development.

Effects of Adsorption and Desorption of Low-Boiling-Point Total Hydrocarbon Gases on Activated Carbon.

In this study, we selected materials that efficiently adsorb total hydrocarbons (THCs) from petrochemical storage facilities and applied four types of activated carbons to adsorb THCs to evaluate their properties. Four gases with low boiling points, namely, ethylene, ethane, propylene, and propane, generated via petrochemical storage facilities, were selected and mixed to a constant concentration with four types of materials and used to investigate the adsorption capacities and desorption properties. The adsorbents comprised two raw materials and two chemically activated materials. The specific surface areas of activated palm (2085 m2/g) and coal (1752 m2/g), which are chemically activated carbons, exhibited a twofold increase compared to those of raw palm (1232 m2/g) and coal (946 m2/g). Thus, we identified the correlations between the physical properties of the activated carbon adsorption materials and their adsorption capacities for four low-boiling-point THCs generated by petrochemical storage facilities.

Pyrolysis of an organic-rich shale containing type II kerogen before and after oil generation and expulsion: Implications for the generation of late hydrocarbon and hydrogen gases

Thermal simulation of late gas generation of source rock is critical for evaluating the potential of deep gas and shale gas. Retained oil and its interactions with thermally mature kerogen can have a significant impact on late gas generation from source rocks; however, previous studies commonly used expelled oil or total oil, which have different compositions from retained oil. In addition, molecular hydrogen (H2 gas) is not only a pyrolysis product but may also have significant effects on hydrocarbon formation. The effects of oil generation and expulsion, as well as retained oil, on H2 generation from source rocks are currently poorly understood. Our study involved two-stage pyrolysis under high-pressure conditions: main oil generation and expulsion, followed by late gas generation. The yields of both hydrocarbon gas and H2 gas were determined and examined deeply in order to investigate the influence of key factors on late gas generation, such as oil generation and expulsion and the interactions between retained oil and mature kerogen. Furthermore, the influence of kerogen type and thermal maturity on late hydrocarbon gas potential was discussed with a literature review. Firstly, oil generation and expulsion could significantly reduce the yields of methane, C2–5 and H2 gases from the pyrolysis of shale. After oil expulsion, the mature shale produced both CH4 and H2, the majority of which came from the kerogen cracking. The interactions between mature kerogen and retained oil may have slightly promoted the generation of methane and inhibited the generation of H2, but they had little influence on the potential for total hydrocarbon gas. Secondly, the H2 generation process could be sub-divided into four stages, which correspond to early hydrocarbon gas generation (stage I), main C2–5 gas generation (stage II), main C2–5 gas cracking (stage III) and the latest methane generation (stage IV), respectively. More than 80% of the total H2 yields were produced in stages III and IV, suggesting that most of the H2 gas was generated through the demethylation, aromatization and condensation processes. Finally, this study concluded that the late hydrocarbon gas potential of different types of kerogen is mostly related to thermal maturity and can be represented by a simple power function.

Impact of oxygenated fuels on atmospheric emissions in major Colombian cities

The use of oxygenated gasolines has increased in Latin America over the past several years with the goal to reduce oil dependence, improve gasoline combustion and emit fewer pollutants to the atmosphere. Countries such as Brazil, Colombia, Mexico, Argentina, and Peru blend their gasoline with ethanol in different proportions. In Colombia, the regulation establishes a 10% vol of ethanol in gasoline (E10). Ethers are also used to oxygenate gasolines. MTBE (methyl tert-butyl ether) is blended in gasoline primarily in Mexico, Venezuela, and Chile, while ETBE (ethyl tertiary-butyl ether) is used in Argentina. The U.S. EPA Motor Vehicle Emissions Simulator (MOVES) model was adapted to Colombia to evaluate gasoline blends with two renewable oxygenates (ethanol and ETBE) on the emission of criteria pollutants (PM2.5, CO, NOx, SO2), Total Gaseous Hydrocarbons (TGH), Volatile Organic Compounds (VOCs), and toxic compounds. We followed the same approach used to build MOVES-Mexico and assess fuel specifications changes on vehicle emissions.The MOVES-Colombia model finds that E10 increases fuel volatility, VOCs, NOx, PM2.5, and SO2 emissions, and decreases CO relative to the unoxygenated base gasoline (E0). The impact of E10 consumption on air quality is due not only to primary pollutants, but also to the emission of ozone and PM2.5 precursors. Compared to E10 and E0, the ETBE blends reduce fuel volatility and emissions of VOCs, TGH, CO, NOx, PM2.5, and SO2. The introduction of ETBE could help major urban areas to meet air quality standards even with their current vehicle fleets. This work highlights that the effect of new fuel specifications needs to be properly assessed in terms of air quality before they are put in place. The development of modeling tools, such as MOVES-Colombia, facilitates the study of fuel quality and vehicle technology on pollutant emissions.

Slow pyrolysis of cork granules under nitrogen atmosphere: by-products characterization and their potential valorization

Cork granules (Quercus suber L.) were slowly pyrolyzed at temperatures between 400-700 °C and under N2 flow. While preserving its structure, some cells of the cork biochar became interconnected, allowing such carbon residue to be used as templates for manufacturing ceria redox materials. The pyrolytic char morphology was similar to that of the natural precursor. The produced cork biochar belonged to Class 1 (C > 60%) and possessed a high heating value of 32 MJ kg−1. Other pyrolysis-derived compounds were identified and quantified through GC-FID and GC-MS analyses. The yield of gases released during cork pyrolysis was strongly dependent on the temperature used due to the thermal decomposition reactions involved in the degradation of cork. In particular, rising pyrolysis temperature from 500 to 700 ºC resulted in reducing the total hydrocarbon gases from 74 to 24 vol%. On the other hand, the yield of H2 increased from 0 to 58% by increasing the pyrolysis temperature from 400 to 700 ºC. Due to the presence of suberin in cork, the composition and yield of bio-oil could be regulated by the pyrolysis temperature. Cork bio-oil was found to consist of long-chain hydrocarbons (from C11 to C24). The bio-oil resulting from the slow pyrolysis of cork residues is suitable as an appropriate feedstock for producing aliphatic-rich pyrolytic biofuels or as a source of olefins. Overall, the findings of this study suggest that Quercus suber L. could be a promising feedstock for biochar and biofuel production through the pyrolytic route and could contribute to the environmental and economic sustainability of the cork production industry.

Hydrocarbon Generation Potential of Microbial Carbonate in the Western Qaidam Basin, China: Implication From Thermocompression Experiment

The potential of microbial carbonate rocks as hydrocarbon source rocks still remains uncertain. To evaluate the hydrocarbon generation and expulsion capability of microbial carbonate rocks, stromatolite obtained from the Xiaganchaigou formation of the western Qaidam Basin has been used for thermocompression experiments to simulate hydrocarbon generation and expulsion at temperature of 280 to 380°C. The results show that the generation potentials of total oil, residual oil, expelled oil, and hydrocarbon gases for stromatolite are 143.39 to 379.99 mg/g total organic carbon (TOC), 47.08 to 223.92 mg/gTOC, 71.12 to 170.81 mg/gTOC, and 6.60 to 101.74 mg/gTOC, respectively. A three-stage model of hydrocarbon generation and expulsion evolution has been constructed for stromatolite. The results show that the first stage is characterized by relatively slow oil generation with associated hydrocarbon gases, having limited capability of oil expulsion in the temperature range of 280 to 360°C (0.50% ≤ Ro ≤ 0.70%). The second stage is characterized by rapid oil generation with associated hydrocarbon gases, having incremental capability of oil expulsion in the temperature range of 320 to 360°C (0.70% ≤ Ro ≤ 1.15%). The third stage is characterized by hydrocarbon gas generation with associated oil, having efficient oil expulsion capability in the temperature range of 360 to 380°C (1.15% ≤ Ro ≤ 1.45%). The experimental data of argillaceous dolostone, gray mudstone, and marlstone, which were reported with the same hydrocarbon generation experimental method, was compared with the data for stromatolite. Compared with traditional source rocks, the oil generation potential of stromatolite is less than that of argillaceous dolostone and gray mudstone but greater than that that of marlstone in the same amount of organic carbon. Especially, the hydrocarbon gas generation potential of stromatolite is approximately double than that of traditional source rocks. Therefore, the experiments indicate that the microbial carbonate rocks in the western Qaidam Basin could be effective source rocks.

Detection and Identification Method of Drilling Total Hydrocarbon Gas Based on Infrared Spectroscopy and KL+BP-RBF Algorithm

In the process of deep oil and gas exploration, it is more and more difficult to identify hydrocarbon gas in the reservoir bed. Conventional methods cannot overcome the difficulties of precision and strong real-time performance, resulting in misjudgments and missed judgments of oil and gas reservoir beds. Infrared spectroscopy detection technology can realize the qualitative and quantitative analyses of substances quickly and without contact and provide a new method to solve the above problems. Therefore, based on the above, this article proposes an infrared spectroscopy detection method of total hydrocarbons while drilling. Combining the Karhunen–Loeve (KL) feature extraction method, using the backpropagation (BP) algorithm to optimize the radial basis function (RBF) neural network, a KL+BP-RBF analysis model of infrared spectroscopy is established to realize the identification and prediction of the total hydrocarbon gas in drilling. In order to verify the accuracy of the detection method, based on the selection of the suitable number of hidden layer nodes, through the comparative analysis of the two-classification experiments, the results show that the accuracy of the KL+BP-RBF method reaches 97.73%. The KL+BP-RBF multiclassification method is established based on the one-versus-one theory. Through simulation experiment analysis, the accuracy of the method reaches 97.93%. The infrared spectroscopy detection method of total hydrocarbon gas components while drilling is established, which can quickly and accurately identify hydrocarbon gases. It provides new technical support for discovering oil and gas reservoirs early.

Photo-driven heterogeneous microbial consortium reducing CO2 to hydrocarbons fuel

Carbon dioxide as feedstock for hydrocarbon synthesis attracts numerous efforts via the biological or chemical approaches. With the purpose of constructing a robust and highly-efficient platform for CO2 bioconversion to fuel, we investigated a photo-driven bioprocess of directing CO2 reduction to C1–C6 alkanes/alkenes discovered from the enriched microbial consortia. GC-MS analysis revealed that the maximum yield of total gaseous hydrocarbons was 169.66 μM with the average CO2 reduction rate of 100.87 μM/day decreasing from 11573.39 μM to 5905.73 μM during 50 days culturing. The pathway of CO2 bioconversion was proposed according to the 16S rRNA and metagenomic sequencing that rTCA and Wood-Ljungdahl were mainly contributed to CO2 fixation, and nitrogenase was responsible for the hydrocarbon syntheses. Following these results, a versatile consortium-based platform was developed via the neural network method with the selected Pseudomonas sp., Serratia sp., Candidatus sp., Clostridium sp., Enterococcus sp., Salmonella sp., Rhodospirillum sp., Thalassospira sp., Thioclava sp., Stenotrophomonas sp. and Desulfovibrio sp., which showed the improved CO2 reduction rate of 107.54 μM/day and the higher selectivity of C1–C4 alkanes than the original consortia. This study demonstrated that this artificially constructed consortium could be a promising platform for converting CO2 to the diverse gaseous alkanes and alkenes.

Rhizoremediation of hydrocarbon contaminated soil using Luffa aegyptiaca (Mill) and associated fungi

The potentials of Luffa aegyptiaca and its rhizospheric, non-mycorrhizal fungi in biodegrading and bio-remediating hydrocarbon contaminated soil were investigated in-vitro and in-situ. Biodegradation study was done in two stages: preliminary study using hydrocarbon treated filter paper and in-vitro with Mineral Salt Media (MSM) read on Spectrophotometer at two photo synthetically active wavelengths (530 nm and 620 nm) while rhizoremediation study was done in-situ in contaminated plot of land. Hydrocarbon utilization ability of the fungi and plant were confirmed using total petroleum hydrocarbon (TPH) analysis and gas chromatography mass spectroscopy (GC-MS). Results show differing rates of hydrocarbon utilization by isolated fungi. In-vitro biodegradation study showed that Aspergillus niger, Fusarium solani, Curvularia lunata and Trichoderma harzianum were best in degrading kerosene (78%), diesel (70%), spent engine oil (83%) and crude oil (77%) respectively. Rhizoremediation study using L. aegyptiaca and C. lunata show that remediation was enhanced to 72.15% as against 32.32% and 14% when only the plant or fungus is used respectively. Hydrocarbon accumulation by L. aegyptiaca also decreased in the presence of the fungus. Curvularia lunata is shown in this study to enhance the germination, survival, growth and bioremediation efficiency of L. aegyptiaca in polluted environment. Novelty statement The potentials of Curvularia lunata, a non-mycorrhizal fungi associated with L. aegyptiaca in survival, growth and phytoremediation of petroleum hydrocarbon polluted soil by L. aegyptiaca is highlighted in this study. Luffa aegyptiaca and its associated fungi is shown to bio-remediate petroleum hydrocarbon through phyto-accumulation and rhizosphere effect.

Study on Chromatographic Condition Assessment of Transformer Oil Based on Random Forest Model

In order to solve the problem that the accuracy of transformer condition assessment based on oil chromatographic data is not high, this paper adopts random forest to evaluate transformer state. In order to prevent the attribute values carried by the decision tree of the basic unit in the evaluation model from being too few and thus affecting the evaluation accuracy. The ratio of H2, CH4, C2H6, C2H4, C2H2, total hydrocarbon and various characteristic gases is used as the characteristic quantity, a stochastic forest optimization model for oil chromatography state assessment was constructedimmediately following the heading. It is compared with BP neural network and SVM, the test results of field oil chromatogram data show that the accuracy of random forest state assessment is 88.5%, which is better than BP and SVM, and the random forest assessment model has faster assessment speed, This paper provides technical support for the fast and accurate condition assessment of transformer.

Overheating and discharge fault identification for novel three-element mixed oil–paper insulation system based on new characteristic gas combination parameters

To support the safe operation of the novel three-element mixed insulation oil (TEMO) transformer, gas generation behaviors of the TEMO oil–paper insulation system under overheating faults and discharge faults were investigated. Results show that that the content of H2 and C2H6 generated by TEMO–paper insulation system is much higher than that in conventional mineral oil (MO)–paper insulation system under different overheating temperatures. Under partial discharge fault, the content of H2 dissolved in oil changes distinctly, while the content of C2H2 also increases with the discharge time. Under surface flashover breakdown, AC breakdown and lightning impulse breakdown fault, the content of H2 and C2H2 changes greatly compared to other gases, while the concentration of total hydrocarbon gases in TEMO–paper insulation system is smaller than that in MO–paper insulating system after the same breakdown times. The diagnosis model of overheating and discharge faults for the TEMO–paper insulation system was proposed based on the oil dissolved gas analysis, while H2, C2H2 and C2H4 were chosen as the characteristic gases and the boundary settings were determined. The verified result for the low-temperature overheating, lightning impulse and surface flashover fault for the TEMO–paper insulation system presents that the new diagnosis model is effective.

Productivity evaluation method of tight sandstone reservoir based on the logging curve

Strong heterogeneity, poor pay reservoir connectivity, and complex micro-pore structure are the reasons behind the high difficulty and low accuracy in the productivity evaluation of tight sandstone gas reservoirs. This paper utilized various well logging and mud logging curve data, summarizes the typical curve type, and made use of a mathematical method to form quantitative characterization. Additionally, a logging curve evaluation method is proposed based on the test of production capacity. The total hydrocarbon curve can be divided into six types as shown by the results: box shape, half box shape, upright triangle, inverted triangle, sawtooth shape, single peak, etc. The above is closely related to the level of oil and gas in the reservoir layer. Six types of total hydrocarbon curve can be quantified by amplitude, relative centroid, relative sawtooth, variance, and the parameter value of the autocorrelation function. The box-shaped total hydrocarbon gas logging curve is full and has a large scale. The half box-shaped total hydrocarbon gas logging curve peak scale is significantly smaller than that of the reservoir thickness. The triangularly-shaped total hydrocarbon gas logging curve may either be an upright or inverted triangle. The sawtooth-shaped total hydrocarbon gas logging curve has high and low tendencies that show a number of spikes. Single peak-shaped total hydrocarbon gas logging curve is small with a single peak. There is a good relationship between the six kinds of total hydrocarbon gas logging curve and the tight sandstone gas reservoir production capacity. The high and middle gas pay layers are mainly box-shaped and triangular, whereas the lower production layer is half box-shaped, triangular, and has a zigzag pattern. However, the low gas pay layers mainly possess a sawtooth pattern, while the non-production layer is mainly single peak in shape. The comprehensive interpretation of the total hydrocarbon gas logging curve and log resistivity curve can more accurately distinguish the production capacity of tight sandstone gas reservoirs. Finally, the quantitative model is used for automatic interpretation. Through data verification and analysis, it is found that the coincidence rate of the production gas pay layer is 80.95%, whereas the coincidence rate of production capacity is 78.05%. It is proven by practice that the gas formation capacity of tight sandstone gas reservoirs can be predicted based on the logging and mud logging well curve shapes.

AC Surface Flashover and Gas Generation Difference of the Cellulose Insulation Pressboard Immersed in Novel 3-Element Mixed Oil and Mineral Oil

Surface flashover fault is one of the most challenge issues in oil-cellulose insulation pressboard system used in power transformer. In this study, a comparative study of the AC surface flashover properties of the novel 3-element mixed oil-cellulose insulation pressboard (3EMO-IP) and mineral oil-cellulose insulation pressboard (MO-IP) was performed under needle-plate and finger-finger electrode, respectively, measurement including dielectric property, surface flashover voltage, damage of cellulose pressboard surface and the gas generation behaviors after multiple surface flashover. Results show that the cellulose insulation pressboard immersed in the novel 3-element mixed insulation oil (3EMO) has higher relative permittivity and dielectric loss factor at 50 Hz, and also has slightly lower surface resistivity. The AC surface flashover voltage of the 3EMO-IP is higher than that of MO-IP under needle-plate and finger-finger electrode (electrode distance 5 mm, 10 mm, 15 mm and 20 mm). Compared to MO-IP, the lower electric field intensity at the oil-pressboard interface, as well as more difficult for surface charge accumulation of 3EMO-IP and the higher breakdown voltage of 3EMO lead to the higher AC surface flashover voltage of 3EMO-IP. Moreover, the carbonization of fibers in 3EMO-IP is slightly less. After multiple surface flashover, C2H2 and total hydrocarbon gases are the main differences between 3EMO-IP and MO-IP, which is more marked with the increase of flashover times. This study offers a reference for improving the surface flashover property of oil-pressboard insulation system by using 3EMO.

Gas generation potential and processes of Athabasca oil sand bitumen from gold tube pyrolysis experiments

Gold-tube pyrolysis experiments were conducted on two oil sand bitumens (OSBs) from the top and bottom of the McMurray Formation in the Athabasca oil sand region of Alberta, Canada. Temperatures ranging from 300 °C to 650 °C and a pressure of 50 MPa with heating rates of 2 °C/h were used to investigate the gas generation behavior of OSB. The extractable residual bitumen content decreased systematically with increasing heating temperatures resulting in a continuous increase in total hydrocarbon gas yields with the highest value of about 480 mg/g bitumen at 650 °C. Among hydrocarbon gases, the yields of methane (C1) increased consistently with experimental temperatures, while the yields of ethane (C2), propane (C3), butanes (i + n-C4) and pentanes (i + n-C5) increased initially to a critical pyrolysis temperature and then decreased at higher temperatures. Molecular indices (C1/C2, C2/C3, C2/i-C4, C3/C4, i-C4/n-C4, i-C5/n-C5 and C1/ΣC1-5) obtained in this work are different from typical primary thermogenic gases generated from kerogen or secondary thermogenic gases derived from thermal cracking of oil. Three stages of OSB thermal evolution were identified over a wide range of heating temperatures. The first stage (300–425 °C) reflects initial decomposition of thermally unstable moieties in resins and asphaltenes. Gas generated at this stage was dominated by carbon dioxide and hydrogen sulfide with minor amounts of hydrocarbon. Hydrocarbon gases were enriched in wet gas components with increasing heating temperatures. The second stage (425–525 °C) corresponds to liquid oil cracking and wet gas generation. While the yields of methane and ethane still increased with heating temperatures, yield of propane reached a maximum and yields of butane and pentane started to decline. The third stage (525–650 °C) reflects wet gas cracking and dry gas generation as indicated by the dramatic decrease of wet gas components and increase in gas dryness. Variations of gas yields and chemical compositions from two OSBs were partially caused by different levels of biodegradation. The top OSB has experienced less biodegradation influence than the bottom one as indicated by higher saturated and aromatic hydrocarbon contents and intact alkylphenanthrene distribution. Increased biodegradation of OSB yielded a higher concentration of polar compounds and an overall lower hydrogen content, which reduced the hydrocarbon gas generation potential. Slightly higher amounts of wet gas components were generated from the top OSB because of the relatively higher content of reactive moieties (mainly alkyl groups) at a lower biodegradation level, while a higher proportion of methane was observed from the bottom, severely biodegraded OSB that was enriched in cross linked ring structures.

Gas evolution and isotopic fractionations during pyrolysis on coals of different ranks

The study was performed on 4 different coals of varied rank. Pyrolysis was conducted on coals of different ranks in gold capsules, with the yield and stable carbon isotopic values of selected gas components and liquid hydrocarbons separately measured to investigate the hydrocarbon generation chemistry, isotopic compositions, and kinetic parameters in coal. With increasing heating temperature, the methane concentrations and total gaseous hydrocarbons increase consistently with temperature. The liquid hydrocarbon concentrations first increase to maximum values and then decrease with temperature. Coals of higher ranks are more likely to primarily produce methane, while coal with low maturity is more likely to produce wet gases. The compositional differences of the four coals become similar at the late stage of the pyrolysis experiment, with a methane content >95%. All of the experiments show a similar isotope trend δ13C1 < δ13C2 < δ13C3 at the same temperature. The δ13C values of ethane and propane became less negative with increasing temperature for all four experiments. The gap between δ13C1 and δ13C2 is greater than that between δ13C2 and δ13C3. There is a linear relationship between ln(C1/C2) versus ln(C2/C3). When ln(C2/C3) increases sharply as ln(C1/C2) increases, the decomposition rates exceed the generation rates for C4 +5, C3, and C2 as secondary oil cracking occurs. At high temperatures, both parameters are larger. The activation energy distribution of 48–72 kcal/mol for Yilan coal is slightly higher than 55–66 kcal/mol for Xinjing coal, but significantly higher than the distribution of 46–61 kcal/mol for Qinan coal and 51–67 kcal/mol for Shitai coal.

Anomalies of natural gas compositions and carbon isotope ratios caused by gas diffusion – A case from the Donghe Sandstone reservoir in the Hadexun Oilfield, Tarim Basin, northwest China

Natural gases in the Carboniferous Donghe Sandstone reservoir within the Block HD4 of the Hadexun Oilfield, Tarim Basin are characterized by abnormally low total hydrocarbon gas contents (<65%), low methane contents (<10%) and low dryness coefficients (<0.5), and a reversal of the normal trend of carbon isotope ratios, showing δ13C methane (C1) > δ13C ethane (C2) < δ13C propane (C3) < δ13C butane (C4). Specifically, methane is enriched in 13C with the variations in δ13C1 values between gases from Block HD4 and gases from its neighboring blocks reaching 10‰. This type of abnormal gas has never been reported previously in the Tarim Basin and such large variations in δ13C have rarely been observed in other basins globally. Based on a comprehensive analysis of gas geochemical data and the geological setting of the Carboniferous reservoirs in the Hadexun Oilfield, we reveal that the anomalies of the gas compositions and carbon isotope ratios in the Donghe Sandstone reservoir are caused by gas diffusion through the poorly-sealed caprock rather than by pathways such as gas mixing, microorganism degradation, different kerogen types or thermal maturity degrees of source rocks. The documentation of an in-reservoir gas diffusion during the post entrapment process as a major cause for gas geochemical anomalies may offer important insight into exploring natural gas resources in deeply buried sedimentary basins.

THE EFFECT OF JOJOBA OIL–DIESEL FUEL BLENDS ON COMBUSTION AND EXHAUST GASES EMISSIONS FOR TRACTOR DIESEL ENGINES

Experiments were designed to study the effect of blends of jojoba oil with diesel fuel on tractor emission characters. Exhaust gases emission tests were conducted for agricultural tractor running on the 0, 20, 40, 60 and 80% jojoba-diesel fuels as compared to pure petroleum diesel fuel under typical field tillage operation at different forward speeds (1.75 , 2.60 and 4.85 km/h). The chemical analysis of Jojoba oil revealed that it contains law carbon atoms and oxygen atoms in its chemical structure, so it produced complete combustion and decreased the emitted toxic gases which lower environmental pollution because it is an oxidizing agent. The increase in jojoba oil blended ratio more than 20% leads to increase fuel viscosity which decreases the engine power and incomplete combustion which leads to increase environmental pollution. The utilization of jojoba-diesel blend 20% (J20) gave significant reduction in total hydrocarbon (THC), carbon dioxide (CO2), carbon monoxide (CO), Sulfur dioxide (SO2) and nitrogenous oxides (NOx) gases emissions, which have positive effect on environment. Using jojoba oil blend 20% (J20) improved the combustion efficiency to 80% at tractor forward speeds, which gave better performance of the tractor engine and decreased emission of toxic gases.

The experimental study on H2S generation during thermal recovery process for heavy oil from the Eastern Venezuela Basin

Hydrogen sulfide (H2S) is toxic, corrosive and environmentally damaging. It is not only found in oil and gas development, but is also often found in heavy oil exploitation. In this study, three heavy oils were selected from the Orinoco Heavy Oil Belt in the southern part of the Eastern Venezuela Basin. Thermal cracking experiments in gold sealed tubes were then conducted using the heavy oils. The objective of the experiment is to unravel the H2S generation mechanism and utility in establishing a development program for heavy oil thermal recovery. The results of the oil isothermal cracking experiments show that the H2S yield increases with the increasing cracking temperature and holding time at 150 °C and 250 °C. Carbon dioxide (CO2) is the main component in gaseous products and its concentration is more than 80% in our experiments. The yields of CO2, H2S and total hydrocarbon gas present similar varying trend that increases with increasing isothermal time. The sulfur contents in group compositions of the original oil from the CJS-48 well and that of the residual oils with different cracking time at 250 °C were then measured. The analytical results show that most sulfur (>75%) exists in aromatics both in original oil and in the residual oils cracked at 250 °C, not to mention, no sulfur was measured in saturates. Although the decrease of sulfur in aromatics with the increased cracking time is low, it has great significance to the H2S generation during thermal recovery of heavy oil for more than 75% sulfur existed in aromatics. The decrease of sulfur content in resin and asphaltene of cracking residues with increased cracking time indicates that the sulfur existed in resin and asphaltene has some contribution to H2S generation during the thermal recovery process of heavy oil.

Formulation of stable water-in-diesel emulsion fuel and investigation of its properties

ABSTRACTThe use of water-in-diesel emulsion fuel has the potential to significantly reduce the formation of oxides of nitrogen (NOX), particulate matter (PM), and total gaseous hydrocarbons (THC) in diesel engines without engine modification. The preparation of stable water-in-diesel emulsion fuel and its variation in properties is critical for the successful development of diesel engines. The present study was carried out to create a stable water-in-diesel emulsion fuel by analyzing the effects of different process variables on emulsion preparation, including surfactant hydrophilic–lipophilic balance (HLB), water concentration in diesel, and stirrer speed. The stability was analyzed by emulsion fuel density variation as a function of time using a photonic system on the emulsion surface. From the results obtained, it was found that sorbitan monolanrate mixed at maximum stirring speed gave optimal emulsion stability for all concentrations of water. The critical fuel properties (density, viscosity, heating value, flashpoint, and corrosiveness) were measured for stable emulsion fuel and compared to the European Standard of automotive fuel requirements. The results indicate that a concentration of water in excess of 10% failed to meet fuel requirements.

Petroleum generation kinetics for Permian lacustrine source rocks in the Junggar Basin, NW China

The Junggar Basin is a major oil producing province in China. Most of the oil originated from Permian lacustrine oil-prone source rocks in the basin. Kinetic parameters for oil and gas generation were obtained from confined pyrolysis experiments using gold capsules at heating rates of 20°C/h and 2°C/h on kerogen samples from two Permian lacustrine oil-prone source rocks (J23S3 and SS1S3) having hydrogen indices of 663 and 698mgHC/g TOC, respectively. The kinetic properties for oil and gas generation vary substantially between these two source rocks. Assuming a burial heating rate of 5°C/My, the temperature for 50% transformation ratio to oil is 132°C for J23S3 and 168°C for SS1S3. The maximum oil yields are about 604 and 770mg/g TOC, while the maximum yields of total gaseous hydrocarbons are about 306 and 348mg/g TOC for J23S3 and SS1S3, respectively. Gaseous hydrocarbons from the confined pyrolysis experiments include primary cracking components from kerogen and secondary cracking components from the generated oil. The secondary cracking gaseous hydrocarbons comprise up to 84.9% and 95.1% of the total, respectively, for the two source rocks in the highest temperature experiments. A practical method estimates the amount of gaseous hydrocarbons generated from these source rocks under geological conditions based on: (1) kinetic parameters for gas generation obtained from kerogen confined pyrolysis experiments in the present study, (2) the maximum yield of gaseous hydrocarbons from oil confined pyrolysis experiments from previous studies, and (3) the maximum amount of expelled oil. The maximum amounts of expelled oil range from 509–588 and 724–750mg/g TOC with oil expulsion efficiencies in the ranges 84.3–97.4% and 94.0–97.4% for J23S3 and SS1S3, respectively, assuming that the amounts of retained oil range from 30–160 and 50–110mg/g TOC for the two source rocks after oil expulsion based on the amounts of extracted bitumen. Consequently, the maximum yields of total gaseous hydrocarbons could be in the ranges 53.1–87.0 and 25.5–36.8mg/g TOC, respectively, for J23S3 and SS1S3 in nature. Using the kinetic parameters for these two source rocks determined from pyrolysis experiments, oil and gas generation and expulsion were modeled for source rocks within the Lower Permian Fengcheng (P1f) and Middle Permian Lower Wuerhe formations (P2w) in the central area of the Mahu Depression, the source kitchen for most oilfields in the basin.