[Estimating Methane Fugitive Emissions from Oil and Natural Gas Systems in China].

To achieve its carbon peaking and carbon neutrality objectives, China is committed to promoting a decarbonized energy transition, which has strengthened the shift from coal to oil and gas resources. As a result, methane (CH4) fugitive emissions from China's oil and gas systems are of increasing concern. Fugitive emissions include equipment leaks, venting, and flaring and involve exploration, production, transportation, storage, and distribution of oil and gas resources. However, there is no uniform accounting method for methane fugitive emissions from oil and gas systems, and fugitive emissions have not been included in the national greenhouse gas inventory statistics. Using the relevant methods, methane fugitive emissions from China's oil and gas systems were estimated for the period from 1980-2020. The results showed that CH4 fugitive emissions from oil and gas systems increased rapidly with the growth of production and consumption of oil and gas resources, from less than 0.6 million tons in 1980 to more than 2.6 million tons in 2020. CH4 fugitive emissions from oil and gas systems reached approximately 0.6 million tons and 2.0 million tons, which were 1.38 and 16.6 times larger than those in 1980, respectively. Fugitive emissions from oil and gas systems originated primarily from gas production, oil production, gas transportation, and storage, accounting for 41%, 20%, 18%, and 13% of total emissions, respectively. Gas pipelines were the main fugitive facilities. The emission intensity of unconventional oil and gas resource exploration was higher compared to conventional resource exploration. This study improved the CH4 fugitive emission inventory, which could provide solid scientific data for CH4 reduction.

Hydrocarbon Tracers Suggest Methane Emissions from Fossil Sources Occur Predominately Before Gas Processing and That Petroleum Plays Are a Significant Source.

We use global airborne observations of propane (C3H8) and ethane (C2H6) from the Atmospheric Tomography (ATom) and HIAPER Pole-to-Pole Observations (HIPPO), as well as U.S.-based aircraft and tower observations by NOAA and from the NCAR FRAPPE campaign as tracers for emissions from oil and gas operations. To simulate global mole fraction fields for these gases, we update the default emissions' configuration of C3H8 used by the global chemical transport model, GEOS-Chem v13.0.0, using a scaled C2H6 spatial proxy. With the updated emissions, simulations of both C3H8 and C2H6 using GEOS-Chem are in reasonable agreement with ATom and HIPPO observations, though the updated emission fields underestimate C3H8 accumulation in the arctic wintertime, pointing to additional sources of this gas in the high latitudes (e.g., Europe). Using a Bayesian hierarchical model, we estimate global emissions of C2H6 and C3H8 from fossil fuel production in 2016-2018 to be 13.3 ± 0.7 (95% CI) and 14.7 ± 0.8 (95% CI) Tg/year, respectively. We calculate bottom-up hydrocarbon emission ratios using basin composition measurements weighted by gas production and find their magnitude is higher than expected and is similar to ratios informed by our revised alkane emissions. This suggests that emissions are dominated by pre-processing activities in oil-producing basins.

Satellites Detect Abatable Super-Emissions in One of the World's Largest Methane Hotspot Regions.

Reduction of fossil fuel-related methane emissions has been identified as an essential means for climate change mitigation, but emission source identification remains elusive for most oil and gas production basins in the world. We combine three complementary satellite data sets to survey single methane emission sources on the west coast of Turkmenistan, one of the largest methane hotspots in the world. We found 29 different emitters, with emission rates >1800 kg/h, active in the 2017-2020 time period, although older satellite data show that this type of emission has been occurring for decades. We find that all sources are linked to extraction fields mainly dedicated to crude oil production, where 24 of them are inactive flares venting gas. The analysis of time series suggests a causal relationship between the decrease in flaring and the increase in venting. At the regional level, 2020 shows a substantial increase in the number of methane plume detections concerning previous years. Our results suggest that these large venting point sources represent a key mitigation opportunity as they emanate from human-controlled facilities, and that new satellite methods promise a revolution in the detection and monitoring of methane point emissions worldwide.

Shale oil production and groundwater: What can we learn from produced water data?

As oil production in the Permian Basin surges, the impact of shale production on groundwater resources has become a growing concern. Most existing studies focus on the impact of shale production on shallow freshwater aquifers. There is little understanding of the shale development's impact on other groundwater resources (e.g., deep carbonate aquifers and deep basin meteoric aquifers). The possible natural hydraulic connections between shallow aquifers and formation water suggest such an impact can be consequential. This study explores the relationship between shale production and groundwater using produced water (PW) samples from active unconventional oil wells. Focusing on the most productive portion of the Permian Basin-the four-county region in Southeast New Mexico between 2007 and 2016, a large produced water dataset allows us to analyze the conditional correlations between shale oil production and PW constituents. The results suggest that (1) expanding from primarily conventional wells to unconventional wells during the recent shale boom has led to dramatic increases of the TDS, chloride, sodium, and calcium levels in groundwater (i.e., producing formation). (2) Nearby oil well density positively correlates with the TDS, chloride, and sodium levels in the PW samples.

In situ transformation of ethoxylate and glycol surfactants by shale-colonizing microorganisms during hydraulic fracturing.

In the last decade, extensive application of hydraulic fracturing technologies to unconventional low-permeability hydrocarbon-rich formations has significantly increased natural-gas production in the United States and abroad. The injection of surface-sourced fluids to generate fractures in the deep subsurface introduces microbial cells and substrates to low-permeability rock. A subset of injected organic additives has been investigated for their ability to support biological growth in shale microbial community members; however, to date, little is known on how complex xenobiotic organic compounds undergo biotransformations in this deep rock ecosystem. Here, high-resolution chemical, metagenomic, and proteomic analyses reveal that widely-used surfactants are degraded by the shale-associated taxa Halanaerobium, both in situ and under laboratory conditions. These halotolerant bacteria exhibit surfactant substrate specificities, preferring polymeric propoxylated glycols (PPGs) and longer alkyl polyethoxylates (AEOs) over polyethylene glycols (PEGs) and shorter AEOs. Enzymatic transformation occurs through repeated terminal-end polyglycol chain shortening during co-metabolic growth through the methylglyoxal bypass. This work provides the first evidence that shale microorganisms can transform xenobiotic surfactants in fracture fluid formulations, potentially affecting the efficiency of hydrocarbon recovery, and demonstrating an important association between injected substrates and microbial growth in an engineered subsurface ecosystem.

Combined releases of oil and gas under pressure; the influence of live oil and natural gas on initial oil droplet formation.

Both oil droplets and gas bubbles have simultaneously been quantified in laboratory experiments that simulate deep-water subsea releases of both live oil (saturated with gas) and additional natural gas under high pressure. These data have been used to calculate particle size distributions (50-5000 µm) for both oil and gas. The experiments showed no significant difference in oil droplet sizes versus pressure (from 5 m to 1750 m) for experiments with live oil. For combined releases of live oil and natural gas, oil droplet sizes showed a clear reduction as a function of increased gas void fraction (increased release velocity) and a weak reduction with increased depth (increased gas density/momentum). Oil droplets were reduced by a factor of 3 to 4 during simulated subsea dispersant injection (SSDI) and no significant effect of pressure was observed. This indicates that SSDI effectiveness is not dependent on water depth or pressure.

Club convergence of per capita carbon emission: global insight from disaggregated level data.

This study aims to examine the convergence hypothesis of per capita carbon dioxide emission and its component such as coal, oil, and gas in the case of 53 countries covering the period of 1980 to 2016. In particular, we study whether countries are moving toward a common steady-state equilibrium condition in the per capita carbon emission or converging into different groups. To do so, this study used Phillips and Sul (Econometrica 75(6): 1771-1855, 2007, J Appl Econ 24(7): 1153-1185, 2009) technique. Our results show no evidence of convergence for full sample. However, our results support the evidence of two club convergence of total emission, emission from gas and petroleum consumption, while three clubs are noticed in case of per capita carbon dioxide emission from coal use. This invalidates the equality rule of participation of each country in climate change policy. Further, similar results emerge in case of total emission and petroleum where club 1 consists of mostly developed countries while club 2 has a large number of developing countries. Interestingly, we do not find any divergence behavior across all countries in the sample. We find that natural gas is the major component to drive the total carbon emission convergence in case of our sample countries.

Assessing changes in groundwater chemistry in landscapes with more than 100 years of oil and gas development.

With recent improvements in high-volume hydraulic fracturing (HVHF, known to the public as fracking), vast new reservoirs of natural gas and oil are now being tapped. As HVHF has expanded into the populous northeastern USA, some residents have become concerned about impacts on water quality. Scientists have addressed this concern by investigating individual case studies or by statistically assessing the rate of problems. In general, however, lack of access to new or historical water quality data hinders the latter assessments. We introduce a new statistical approach to assess water quality datasets - especially sets that differ in data volume and variance - and apply the technique to one region of intense shale gas development in northeastern Pennsylvania (PA) and one with fewer shale gas wells in northwestern PA. The new analysis for the intensely developed region corroborates an earlier analysis based on a different statistical test: in that area, changes in groundwater chemistry show no degradation despite that area's dense development of shale gas. In contrast, in the region with fewer shale gas wells, we observe slight but statistically significant increases in concentrations in some solutes in groundwaters. One potential explanation for the slight changes in groundwater chemistry in that area (northwestern PA) is that it is the regional focus of the earliest commercial development of conventional oil and gas (O&G) in the USA. Alternate explanations include the use of brines from conventional O&G wells as well as other salt mixtures on roads in that area for dust abatement or de-icing, respectively.

Performance and emission characteristics of CNG-fueled compression ignition engine with Ricinus communis methyl ester as pilot fuel.

Surge in petroleum prices, its drying sources and degradation in air quality focused interest on renewable energy sources as substitute for existing fuels for internal combustion engines. This study highlights the combustion, performance, and emission characteristics of diesel engines fueled with compressed natural gas (CNG) as primary fuel and castor (Ricinus communis) oil methyl ester (COME) as pilot fuel. COME was produced from non-edible grade Ricinus communis oil. The biodiesel fuel properties and characterization was done as per ASTM D6751 specifications. The CNG was inducted through inlet manifold fumigation at a consistent flow rate of 15 l/min under dual-fuel mode. It is evident from the test results that B20-CNG yields brake thermal efficiency of 23.6% when compared to 25 and 27% for D-CNG and diesel fuel, respectively. The peak cylinder gas pressure was lower in dual-fuel mode when compared to conventional diesel. The emission results show increase in NOx emission by 24.5 and 28.4% for D-CNG and B20-CNG, respectively when compared to baseline diesel fuel at full engine load. There was increase in HC emission by 6.7 and 11% whereas CO emissions decreased by 31.6 and 37.4% for B20-CNG and D-CNG, respectively at similar operating conditions. Reduction in smoke opacity by 49.4 and 59.6% was achieved respectively for D-CNG and B20-CNG under dual-fuel mode. On the whole, COME exhibits a better pilot fuel choice for dual-fuel combustion mode in comparison to conventional fossil petroleum diesel in terms of combustion, performance, and emissions characteristics.

Total life cycle emissions of post-Panamax containerships powered by conventional fuel or natural gas.

This study proposes an easy-to-apply method, the Total Life Cycle Emission Model (TLCEM), to calculate the total emissions from shipping and help ship management groups assess the impact on emissions caused by their capital investment or operation decisions. Using TLCEM, we present the total emissions of air pollutants and greenhouse gases (GHGs) during the 25-yr life cycle of 10 post-Panamax containerships under slow steaming conditions. The life cycle consists of steel production, shipbuilding, crude oil extraction and transportation, fuel refining, bunkering, and ship operation. We calculate total emissions from containerships and compare the effect of emission reduction by using various fuels. The results can be used to differentiate the emissions from various processes and to assess the effectiveness of various reduction approaches. Critical pollutants and GHGs emitted from each process are calculated. If the containerships use heavy fuel oil (HFO), emissions of CO2 total 2.79 million tonnes (Mt), accounting for 95.37% of total emissions, followed by NOx and SOx emissions,which account for 2.25% and 1.30%, respectively.The most significant emissions are from the operation of the ship and originate from the main engine (ME).When fuel is switched to 100% natural gas (NG), SOx, PM10, and CO2 emissions show remarkable reductions of 98.60%, 99.06%, and 21.70%, respectively. Determining the emission factor of each process is critical for estimating the total emissions. The estimated emission factors were compared with the values adopted by the International Maritime Organization (IMO).The proposed TLCEM may contribute to more accurate estimates of total life cycle emissions from global shipping. Implications: We propose a total life cycle emissions model for 10 post-Panamax container ships. Using heavy fuel oil, emissions of CO2 total 2.79 Mt, accounting for approximately 95% of emissions, followed by NOx and SOx emissions. Using 100% natural gas, SOx, PM10, and CO2 emissions reduce by 98.6%, 99.1%, and 21.7%, respectively. NOx emissions increase by 1.14% when running a dual fuel engine at low load in natural gas mode.

Coal-derived compounds and their potential impact on groundwater quality during coalbed methane production.

Coalbed methane (CBM) is an important unconventional energy source and accounts for a substantial portion of the overall natural gas production in the USA. The extraction of CBM generates significant amounts of produced water, where the withdrawal of groundwater may disturb the subsurface environment and aquifers. The release of toxic recalcitrant compounds from the coal seam is of great concern for those who use groundwater for irrigation and potable water sources. Experiments were conducted that determined a small fraction of coal carbon can be extracted and solubilized in water during the CBM formation and production. These soluble components included long-chain alkanes, aromatic hydrocarbons, and humic compounds. Biometer flask assays demonstrated that these compounds are bioamenable and can be potentially degraded by microorganisms to produce methane and carbon dioxide, where these biodegradation processes may further impact groundwater quality in the coal seam.

Naphthenic acids in groundwater overlying undeveloped shale gas and tight oil reservoirs.

The acid extractable organics (AEOs) containing naphthenic acids (NAs) in groundwater overlying undeveloped shale gas (Saint-Édouard region) and tight oil (Haldimand sector, Gaspé) reservoirs in Québec, Canada, were analysed using high resolution Orbitrap mass spectrometry and thermal conversion/elemental analysis - isotope ratio mass spectrometry. As classically defined by CnH2n+ZO2, the most abundant NAs detected in the majority of groundwater samples were straight-chain (Z = 0) or monounsaturated (Z = -2) C16 and C18 fatty acids. Several groundwater samples from both study areas, however, contained significant proportions of presumably alicyclic bicyclic NAs (i.e., Z = -4) in the C10-C18 range. These compounds may have originated from migrated waters containing a different distribution of NAs, or are the product of in situ microbial alteration of shale organic matter and petroleum. In most groundwater samples, intramolecular carbon isotope values generated by pyrolysis (δ13Cpyr) of AEOs were on average around 2-3‰ heavier than those generated by bulk combustion (δ13C) of AEOs, providing further support for microbial reworking of subsurface organic carbon. Although concentrations of AEOs were very low (<2.0 mg/L), the detection of potentially toxic bicyclic acids in groundwater overlying unconventional hydrocarbon reservoirs points to a natural background source of organic contaminants prior to any large-scale commercial hydrocarbon development.

Cooking fuel and risk of under-five mortality in 23 Sub-Saharan African countries: a population-based study.

Relationship between cooking fuel and under-five mortality has not been adequately established in Sub-Saharan Africa (SSA). We therefore investigated the association between cooking fuel and risk of under-five mortality in SSA, and further investigated its interaction with smoking. Using the most recent Demographic Health Survey data of 23 SSA countries (n = 783,691), Cox proportional hazard was employed to determine the association between cooking fuel and risk of under-five deaths. The adjusted hazard ratios were 1.21 (95 % CI, 1.10-1.34) and 1.20 (95 % CI, 1.08-1.32) for charcoal and biomass cooking fuel, respectively, compared to clean fuels. There was no positive interaction between biomass cooking fuel and smoking. Use of charcoal and biomass were associated with the risk of under-five mortality in SSA. Disseminating public health information on health risks of cooking fuel and development of relevant public health policies are likely to have a positive impact on a child's survival.

The impact of three recent coal-fired power plant closings on Pittsburgh air quality: A natural experiment.

Relative to the rest of the United States, the region of southwestern Pennsylvania, including metropolitan Pittsburgh, experiences high ambient concentrations of fine particulate matter (PM2.5), which is known to be associated with adverse respiratory and cardiovascular health impacts. This study evaluates whether the closing of three coal-fired power plants within the southwestern Pennsylvania region resulted in a significant decrease in PM2.5 concentration. Both PM2.5 data obtained from EPA ground stations in the study region and aerosol optical depth (AOD) data retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments onboard the Terra and Aqua satellites were used to investigate regional air quality from January 2011 through December 2014. The impact of the plant closings on PM2.5 concentration and AOD was evaluated using a series of generalized additive models. The model results show that monthly fuel consumption of the Elrama plant, which closed in October of 2012, and monthly fuel consumption of both the Mitchell and Hatfield's Ferry plants, which closed in October of 2013, were significant predictors of both PM2.5 concentration and AOD at EPA ground stations in the study region, after controlling for multiple meteorological factors and long-term, region-wide air quality improvements. The model's power to predict PM2.5 concentration increased from an adjusted R2 of 0.61 to 0.68 after excluding data from ground stations with higher uncertainty due to recent increases in unconventional natural gas extraction activities. After preliminary analyses of mean PM2.5 concentration and AOD showed a downward trend following each power plant shutdown, results from a series of generalized additive models confirmed that the activity of the three plants that closed, measured by monthly fuel consumption, was highly significant in predicting both AOD and PM2.5 at 12 EPA ground stations; further research on PM2.5 emissions from unconventional natural gas extraction is needed. IMPLICATIONS: With many coal-fired power plants scheduled to close across the United States in the coming years, there is interest in the potential impact on regional PM2.5 concentrations. In southwestern Pennsylvania, recent coal-fired power plant closings were coupled with a boom in unconventional natural gas extraction. Natural gas is currently seen as an economically viable bridge fuel between coal and renewable energy. This study provides policymakers with more information on the potential ambient concentration changes associated with coal-fired power plant closings as the nation's energy reliance shifts toward natural gas.

Complex Fluids and Hydraulic Fracturing.

Nearly 70 years old, hydraulic fracturing is a core technique for stimulating hydrocarbon production in a majority of oil and gas reservoirs. Complex fluids are implemented in nearly every step of the fracturing process, most significantly to generate and sustain fractures and transport and distribute proppant particles during and following fluid injection. An extremely wide range of complex fluids are used: naturally occurring polysaccharide and synthetic polymer solutions, aqueous physical and chemical gels, organic gels, micellar surfactant solutions, emulsions, and foams. These fluids are loaded over a wide range of concentrations with particles of varying sizes and aspect ratios and are subjected to extreme mechanical and environmental conditions. We describe the settings of hydraulic fracturing (framed by geology), fracturing mechanics and physics, and the critical role that non-Newtonian fluid dynamics and complex fluids play in the hydraulic fracturing process.

Water Availability for Shale Gas Development in Sichuan Basin, China.

Unconventional shale gas development holds promise for reducing the predominant consumption of coal and increasing the utilization of natural gas in China. While China possesses some of the most abundant technically recoverable shale gas resources in the world, water availability could still be a limiting factor for hydraulic fracturing operations, in addition to geological, infrastructural, and technological barriers. Here, we project the baseline water availability for the next 15 years in Sichuan Basin, one of the most promising shale gas basins in China. Our projection shows that continued water demand for the domestic sector in Sichuan Basin could result in high to extremely high water stress in certain areas. By simulating shale gas development and using information from current water use for hydraulic fracturing in Sichuan Basin (20,000-30,000 m(3) per well), we project that during the next decade water use for shale gas development could reach 20-30 million m(3)/year, when shale gas well development is projected to be most active. While this volume is negligible relative to the projected overall domestic water use of ∼36 billion m(3)/year, we posit that intensification of hydraulic fracturing and water use might compete with other water utilization in local water-stress areas in Sichuan Basin.

Aquatic hazard and biodegradability of light and middle atmospheric distillate petroleum streams.

Light and middle atmospheric distillate petroleum substances are blended to produce fuels used in transportation and heating. These substances represent the majority by volume of crude oil refined products in the United States. The goal of this research was to develop biodegradability and aquatic toxicity data for four substances; heavy, straight-run naphtha (HSRN), hydro-desulfurized kerosene (HDK), hydro-cracked gas oil (HCGO), and catalytic-cracked gas oil (CCGO). Ready biodegradability tests demonstrated rapid and extensive microbial oxidation of these test substances, indicating a lack of persistence in the aquatic environment. Differences in biodegradation patterns reflected compositional differences in the constituent hydrocarbons. Results of aquatic toxicity tests on alga, cladocera, and fish demonstrated that toxicity was greatest for catalytic-cracked gas oil, which contained a high proportion of aromatic hydrocarbons. Aromatic hydrocarbons are more soluble, and hence more bioavailable, resulting in higher toxicity. When expressed on the basis of loading rates, acute toxicity values (LL/EL50) ranged between 0.3 and 5.5 mg L(-1) for all three species, while chronic no-observed-effect loading rates (NOELR) ranged between 0.05 and 0.64 mg L(-1). PETROTOX estimates for acute and chronic toxicity ranged from 0.18 to 2.3 mg L(-1) and 0.06 to 0.14 mg L(-1), respectively, which were generally more conservative than experimental data.

Unconventional oil and gas extraction and animal health.

The extraction of hydrocarbons from shale formations using horizontal drilling with high volume hydraulic fracturing (unconventional shale gas and tight oil extraction), while derived from methods that have been used for decades, is a relatively new innovation that was introduced first in the United States and has more recently spread worldwide. Although this has led to the availability of new sources of fossil fuels for domestic consumption and export, important issues have been raised concerning the safety of the process relative to public health, animal health, and our food supply. Because of the multiple toxicants used and generated, and because of the complexity of the drilling, hydraulic fracturing, and completion processes including associated infrastructure such as pipelines, compressor stations and processing plants, impacts on the health of humans and animals are difficult to assess definitively. We discuss here findings concerning the safety of unconventional oil and gas extraction from the perspectives of public health, veterinary medicine, and food safety.

Spatially explicit methane emissions from petroleum production and the natural gas system in California.

We present a new, spatially resolved inventory of methane (CH4) emissions based on US-EPA emission factors and publically available activity data for 2010 California petroleum production and natural gas production, processing, transmission, and distribution. Compared to official California bottom-up inventories, our initial estimates are 3 to 7 times higher for the petroleum and natural gas production sectors but similar for the natural gas transmission and distribution sectors. Evidence from published "top-down" atmospheric measurement campaigns within Southern California supports our initial emission estimates from production and processing but indicates emission estimates from transmission and distribution are low by a factor of approximately 2. To provide emission maps with more accurate total emissions we scale the spatially resolved inventory by sector-specific results from a Southern California aircraft measurement campaign to all of California. Assuming uncertainties are determined by the uncertainties estimated in the top-down study, our estimated state total CH4 emissions are 541 ± 144 Gg yr(-1) (as compared with 210.7 Gg yr(-1) in California's current official inventory), where the majority of our reported uncertainty is derived from transmission and distribution. We note uncertainties relative to the mean for a given region are likely larger than that for the State total, emphasizing the need for additional measurements in undersampled regions.

Relevant aspects of radiation protection in oil and gas well logging.

Radiation sources have being widely used in industrial applications, but their inappropriate use presents a large potential for hazards to human health and the environment. These hazards can be minimised by development of specific radiation protection rules and adequate procedures for the handling, use and storage of radiation sources, which should be established in a national normative framework. Recently, due to discovery of new oil and gas reservoirs on the Brazilian continental shelf, especially in deep water and the pre-salt layer, there has been a large and rapid increase in the use of radiation sources for well logging. Generic radiation protection regulations have been used for licensing the use of radiation sources for well logging, but these are not comprehensive or technically suitable for this purpose. Therefore it is necessary to establish specific Brazilian safety regulations for this purpose. In this work, an assessment is presented of the relevant radiation protection aspects of nuclear well logging not covered by generic regulations, with the aim of contributing to the future development of specific safety regulations for the licensing of radioactive facilities for oil and gas well logging in Brazil. The conclusions of this work relate to four areas, which include the specific requirements to control (1) radiation sources, (2) radiation survey meters and (3) access to radiation workplaces and (4) to control and identify the workers who are occupationally exposed.