First Discovery and Significance of Liquid Mercury in a Thermal

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The first discovery and significance of liquid mercury in a thermal simulation experiment on humic kerogen Weilong Peng, Quanyou Liu, Ziqi Feng, Chenchen Fang, Deyu Gong, Peng Li, Yue Lyu, and Pengwei Wang Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b03294 • Publication Date (Web): 02 Jan 2019 Downloaded from http://pubs.acs.org on January 12, 2019

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The first discovery and significance of liquid mercury in a thermal

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simulation experiment on humic kerogen

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Weilong Peng†, ‡, §, Quanyou Liu*, †, ‡, Ziqi Feng*, #,&, Chenchen Fang§, Deyu Gong§, Peng Li†, Yue

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Lyu§, Pengwei Wang‡

5

†

6

Beijing 100083, China

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‡

Petroleum Exploration and Production Research Institute, SINOPEC, Beijing 100083, China;

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§

Research Institute of Petroleum Exploration and Development, PetroChina, Beijing, 100083, China

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# School

State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, SINOPEC,

of Geosciences, China University of Petroleum, Qingdao, 266580, China

10

&

11

Qingdao, 266071, China

Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology,

12 13

Abstract: We firstly found enriched liquid mercury beads in a thermal simulation

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experiment on humic kerogen extracted from coal, which provided some kind of direct

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evidence that mercury can be released from coal measure during maturation. In the

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simulation experiment, mass distribution of liquid mercury beads is between 0.0083 g

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and 0.2242 g; their content in simulated gas range from 372.5 ng/m3 to 2776.3 ng/m3;

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and their yields was from 0.3102 ×10−3 g/g to 7.4312 ×10−3 g/g sample. Along with this

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thermal simulation experiment and previous studies, three genetic models of mercury

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in gas reservoirs are summarized: source-rock controlling type, fault-controlling type,

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and source-rock/fault joint controlling type. Mercury in source-rock-controlling gas

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reservoirs is mainly derived from source rocks, which are generally coal measures. 1

ACS Paragon Plus Environment

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Mercury in fault-controlling gas reservoirs is mainly derived from deep geologic fluids,

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with relatively small contribution from source rocks. The transitional source-rock/fault

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joint controlling type mainly develops in tectonic activity zones where source rocks can

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be either sapropelic or humic. Liquid mercury collected for the first time in simulation

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experiment has important theoretical significance for the exploration and development

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of natural gas, as well as important practical significance for the prevention of mercury

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accidents in natural gas exploration and production.

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Keywords: Mercury; Thermal simulation experiment; Humic kerogen; Natural gas;

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Thermal maturation

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1. Introduction

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Natural gas as widely distributed huge reserves of emerging green energy, has

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gained widespread attention in recent years;1 all three fossil fuels (natural gas, oil and

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coal) primary originate from organic matters, with similar origins and locations.2 The

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organic matters, under the influence of heat, pressure and time, form coal, oil and

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natural gas.3 The mineral matter and solids partition to the oil and coal, leaving the

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majority of volatile contaminants such as mercury, sulfur and moisture remaining in

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the natural gas.2 The trace levels of mercury presented in natural gas are of important

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scientific research significance because they have caused failures of the aluminum heat

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exchangers in gas processing plants.4, 5 Mercury amalgamates with aluminum, resulting

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in a mechanical failure and gas leakage.6 Mercury is a volatile liquid metal under

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normal temperature and pressure, and it does not react easily with other substances.6−10

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In the 1960s, Japanese residents in the Kumamoto Prefecture experienced heavy 2


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casualties due to industrial mercury poisoning.11−15 As an important strategic material

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for energy, natural gas has attracted increasing attention. However, the mercury in

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natural gas not only pollutes the environment, but also endangers human health.16−21

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The corrosion of mercury in natural gas production equipment causes huge direct

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economic losses.6

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There are still two primary opinions on the source of mercury in natural gas.21, 22

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Han et al. (2010)23and Li et al. (2012)24 analyzed the relationship between mercury

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content in Chinese natural gas, source rocks and concluded that mercury in natural gas

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mainly came from source rocks, especially coal measures. Tu. (1985)25, Zettlitzer et al.

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(1997)26 and Hou et al. (2005)21believed that mercury in natural gas primarily came

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from the deep crust. Although many scholars have detected the presence of mercury in

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natural gas,27−30 a consensus has not yet reached whether the mercury in natural gas can

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be directly derived from the maturation process of organic matter.21, 25, 26 Furthermore,

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there is no public literature on studying mercury from the perspective of a thermal

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simulation experiment on organic matter. Being able to confirm that mercury can be

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released from the maturation of organic matter via thermal simulation would be the

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most direct evidence that mercury in natural gas can derived from the source rock.

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Understanding the source of mercury in natural gas and whether the maturation process

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of source rock can release mercury has great scientific significance for preventing

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mercury poisoning and gas-production accidents, and for reducing mercury pollution

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in the environment.

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To date, there are few papers on about the formation mechanism of mercury in gas 3


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reservoirs. Previous studies merely focused on mercury content in petroleum and coal.23,

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25, 31

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maturation of humic organic matter and mercury with a thermal simulation experiment

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to further understand the source of mercury in natural gas and the genetic model of

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mercury in gas reservoirs.

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2. Sample and experimental method

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2.1. Sample

This paper, however, for the first time investigated the relationship between the

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The sample was collected from the Shaping Coal Mine in the northeastern margin

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of the Ordos Basin, China (Fig. 1), which is located in Hequ County, Shanxi Province.

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Before the thermal simulation experiment, we carried out the grinding and extraction

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of kerogen for the coal sample. Low-maturity source rocks can better reflect the

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maturation process of organic matter in the thermal simulation experiment. Therefore,

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the vitrinite Ro of the sample was 0.55%. The maceral group analysis of the kerogen

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showed that the contents of vitrinite, exinite, and inertinite were 85%, 5%, and 10%,

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respectively. The maceral group contained no sapropelite, and organic matter was

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typical humic kerogen (Fig. 2). Rapid pyrolysis was carried out to obtain the

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geochemical parameters of the sample. Total organic carbon (TOC) content of the

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sample was 58.30%. Maximum pyrolysis temperature (Tmax) was 424ºC. The quantity

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of free hydrocarbons (S1 peak) and the amount of hydrocarbons generated during the

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thermal cracking of kerogen in the rock (S2 peak) were 0.66 mg/g and 97.18 mg/g,

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respectively (Table 1).

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2.2. Experimental method 4


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All analysis (including extraction of kerogen in coal, thermal simulation

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experiment, gas components, mercury content in gas, carbon and hydrogen isotopic

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compositions) were completed in the Key Laboratory of Petroleum Geochemistry of

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the Research Institute of Petroleum Exploration and Development, PetroChina. We will

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briefly describe the major experimental methods and steps below.

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2.2.1 Thermal simulation experiment

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The schematic diagram of the thermal-simulation experimental device is shown in

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Figure 3. The experimental apparatus mainly consists of a reaction device, a control

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device, and a collection device. The thermal simulation experiment required lithostatic

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pressure, and we placed the sample (kerogen) in the autoclave. Before the experiment,

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the whole system was vacuum-pumped and then was sealed off. Twelve temperature

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points were designated in the experiment (Table 2). The temperature control procedure

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of the autoclave was programmed: the autoclave temperature was raised from 18ºC

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(room temperature) to 232ºC in 10 min and then maintained at 232ºC for 10 min; then,

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the autoclave temperature was raised from 232ºC to the target temperature of 5ºC/min,

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which was maintained for 3 days (4320 min). Finally, the temperature of the autoclave

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was quickly decreased to 232ºC and maintained at that temperature until the

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experimental product was collected.

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It is worth noting that the cold trap was transferred to −4ºC before the collection

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of the products. The gas–liquid separation device was used to collect the liquid products

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and let the gaseous products pass through it into a glass bottle. The gas product was

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collected by drainage method. After the gas collection, dichloromethane was added to 5


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the gas–liquid separator for the protection of liquid hydrocarbons and mercury. Gas

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products were collected and sealed in two glass bottles. One bottle was used to analyze

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gas components and isotopic compositions; the other was used to analyze the content

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of mercury in gas. The remaining gas was used for quantification and then treated to

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prevent pollution. After the collection of gas products, liquid mercury would gather in

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the gas–liquid separator and then could be collected through filtration and weighed.

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2.2.2 Chemical components analysis

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The components of natural gas were measured by HP7890A gas chromatograph

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(GC) equipped with a flame ionization detector. Every single component was separated

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by a capillary column (PLOT Al2O3 50 m × 0.53 mm). The GC oven temperature was

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set at 33 ºC for 10 min at the beginning, then increased to 180 ºC at the rate of 10 ºC/min

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and finally maintained at the maximum temperature for 20−30 min.

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2.2.3 Stable carbon and hydrogen isotope analysis

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Stable carbon isotope analysis of gas was carried out by isotope mass spectrometer.

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Gas components were first separated by GC, then converted into carbon dioxide and

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injected into mass spectrometer, and individual component is separated by

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chromatographic column. The GC oven temperature was raised up from 33ºC to 80ºC

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at 8ºC/min, then from 80ºC to 250 ºC at 5ºC/min. The final temperature was maintained

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for 10 min. Every sample was measured 3 times then averaged with the standard of

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VPDB and precision of ±0.3‰. Natural gas hydrogen isotope analysis was conducted

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on a MAT253 isotopic mass spectrometer with the method of GC/TC/IRMS. Helium

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was the carrier gas. Components separation of natural gas were conducted within a HP6


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PLOT Q column (30 m × 0.32 mm × 20 μm). The initial oven temperature was started

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with 33ºC, and raised to 80ºC at the rate of 8 ºC/min, then ramped up to 250ºC at the

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rate of 5ºC/min. Every sample was measured 3 times and averaged, with the standard

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of VSMOW and the precision of ±5‰. Detailed descriptions of analyses method and

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process can be found in works by Dai et al. (2012)32 and Huang et al. (2015)33.

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3. Results

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In this paper, we analyzed the composition of simulated gas and the isotopic

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composition of methane. Specific experimental data are shown in Table 2. The amount

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of mercury in coal varies greatly but, generally, is higher than other sedimentary rocks.6,

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21, 22

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of the simulation experiment of the hydrocarbon generation from humic kerogen. The

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mercury collected and the yield of mercury was quantitatively calculated; and finally

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the mercury content in natural gas was analyzed.

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3.1. Chemical and isotopic composition of natural gas

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Enrichment state of liquid mercury beads were found for the first time as a result

Gas generated in the simulated experiment can be divided into hydrocarbon gas

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and nonhydrocarbon gas. Hydrocarbon gas mainly includes methane and its homologue;

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nonhydrocarbon gas mainly includes N2, H2, CO, and CO2 (Table 2). Hydrocarbon gas

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is dominated by CH4; nonhydrocarbon gas is dominated by CO2.

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At 320ºC, the content of CH4 is 10.65%; at 550ºC, CH4 content increases to

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90.24%, and the corresponding dryness coefficient (C1/C1−5) increases from 0.601 to

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0.994, when the natural gas transformed from wet gas to dry gas. The content of CH4 7


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increases gradually with increasing temperature (gas leakage exists at 440ºC, so the gas

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component at 440ºC is merely a reference). At 320ºC, the content of CO2 is 74.90%; at

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550ºC, CO2 content decreases to 4.71%. The δ13C1 value first decreases, and then

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increases and gradually stabilizes. The δ13C1 value distribution ranges from the initial

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−33.0‰ to −24.1‰ (Fig. 4a). The δD1 value increases gradually with increasing

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temperature, and the δD1 value ranges from −300‰ to −134‰ (Fig. 4b).

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3.2. Mercury in thermal simulation experiment

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The chemical properties of mercury are relatively stable and does not easily react

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with other substances. Mercury, which is highly toxic and volatile, is difficult to collect

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in simulated experiments. We designed 12 temperature points in the simulation

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experiment and collected liquid mercury beads at 7 temperature points. In the

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experiment, the mass distribution of liquid mercury beads ranges from 0.0083 g to

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0.2242 g (Fig. 5), and the corresponding yield of liquid mercury ranges from

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0.3102×10−3 g/g to 7.4312×10−3 g/g kerogen (Fig. 6, Table 2). The maximum diameter

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of a liquid mercury bead is over 2 mm. Content of mercury in the gas is distributed

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between 372.5 ng/m3 and 2776.3 ng/m3 (Table 2).

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4. Discussion

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Previous studies on mercury content in coal have been carried out. The mercury

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content of coals are typically around 0.1 ppm.12, 20 In this paper, we discovered mercury

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in enriched state through simulation experiment for the first time.

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4.1. Significance of alkane characteristics for liquid mercury

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A lot of thermal simulation experiments on organic matter have been done by

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previous studies.34−40 The thermal simulation experiment can be divided into open,

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semi-open, and closed systems, according to experimental conditions.41 Samples of

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thermal simulation experiment include dark mudstone,42 coal,37,

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kerogen,40 and humic kerogen.44,

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simulation experiment and analyzed the simulated gas components together with

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carbon and hydrogen isotopic composition of methane. In accordance with previous

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experimental results,34−39,

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experimental temperature. However, in our simulation experiment, gas leakage existed

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at 440ºC, rendering the methane component abnormal (Fig. 7, Table 2). Gas leakage at

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440ºC is the cause of malfunction of the experiment. There is only one temperature

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point (440ºC) where the failure occurs. Because it does not affect the integrity of the

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experiment, the temperature point has not been redone. The other groups of methane

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content collected at the varying temperature points are in accordance with the dynamic

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model of thermal maturation of organic matter.43, 47−50

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39, 43

sapropelic

We collected the gas products of the thermal

alkane content should increase with increasing

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With the increasing temperature, alkane gas shows obvious isotopic fractionation

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(Fig. 4). The carbon isotopic value of methane first decreases and then increases with

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increasing temperature (Fig. 4a). Hydrogen isotopic value of methane tend to increase

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with increasing temperature (Fig. 4b). Geochemical characteristics of the collected gas

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in our thermal stimulation experiment generally conform to the organic-matter

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maturation-dynamics model established by previous studies,49, 51 which indicates that

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our thermal stimulation experiment is generally appropriate and that studying mercury 9


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in natural gas using an organic-matter thermal-simulation experiment is feasible.

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Unfortunately, the evolution rule of mercury yield during the thermal maturation

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of organic matter has not been found in this study. There are abrupt changes in mercury

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yield at several temperature points, which may be due to the high volatility of mercury

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and the difficulty in collecting it. Subsequent research on mercury is still under way.

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Mercury can cause great pollution to the environment, 11−14 so it is very important to

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carry out the geochemical investigation of mercury.

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4.2. Discovery and significance of liquid mercury beads

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The three existing states of mercury in coal are (1) adsorption state of the monomer;

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(2) inorganic compounds, such as HgS and HgO;52−54 and (3) organic compounds, such

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as a long chain compound of mercury.55−58 Our experimental samples are kerogen

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extracted from coal, so there is no mercury in the form of inorganic compounds. The

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source of liquid mercury can only be the adsorption of mercury in the monomer state

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or the mercury element transformed from organic compound. Since the mass of liquid

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mercury collected in our study is relatively heavy, we believe that a considerable

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amount of mercury may be derived from organic compounds of mercury. The content

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of organic mercury compounds in source rocks may be much larger than we thought.

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Source rocks can indeed provide important sources for mercury in natural gas, but it is

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undeniable that deep geologic fluids may also provide material basis for mercury

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enrichment in natural gas.

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Groningen Gas Field is a typical example of high mercury content in natural gas,

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the field’s development in the Late Jurassic–Early Cretaceous was frequently 10


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accompanied by magmatic activity that continued until the end of the Neogene.59

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Magmatic activity may be an important reason for the high mercury content in the gas

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field, that is, the mercury content in the gas field may have originated from deep fluids.

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The investigation of Huang et al. (2015)60 into mercury content in magma-altered coal

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measures in southern China showed that mercury content of the coal measures near the

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alteration increased obviously, which further illustrated that magmatic hydrothermal

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fluids can be potentially rich in mercury and the deep fluids may also be a source for

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mercury in natural gas. The mercury content in coal may be quite high. On the one

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hand, the combustion of coal directly pollutes the environment, on the other hand, coal

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as a source rock of natural gas, enriches mercury in natural gas and causes potential

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environmental pollution.

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On the basis of our thermal simulation experiment and the findings of previous

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studies59, 60, 61, we propose three basic genetic models of mercury gas reservoirs (Fig.

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8):

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(1) Source-rock controlling type (Fig. 8a). The mercury in this gas reservoir is

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mainly derived from maturation process of source rocks. Mercury is transported with

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natural gas to trap. This type of gas reservoir may be developed mainly in the craton

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basin. The basin is relatively stable, with little development of deep faulting system and

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a lack of magmatic activity. The source rock is usually of humic organic matter. The

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Ordos Basin in China belongs to a stable craton basin. There are no deep faults in the

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basin and coal measures are well developed. Therefore, the mercury content in gas

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reservoirs in the basin may be mainly affected by source rocks. 11


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(2) Fault-controlling type (Fig. 8b). Mercury in this type of gas reservoir may be

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derived mainly from deep fluids (including magmatic activity). The mercury in the deep

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fluids is transported to gas reservoirs through faults and other migration systems. This

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type of gas reservoir is developed mainly in foreland basins and rift basins which have

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relatively intense tectonic activities and magmatic activities. The content of organic

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matter in the source rocks are mostly sapropelic. In the Liaohe Basin of China, the

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deeper the gas reservoir is buried, the higher the mercury content is.23 The basin belongs

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to a rift basin with well-developed faults, so the mercury content in the gas reservoirs

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in the basin may be more affected by deep fluids.

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(3) Source-rock/fault joint controlling type (Fig. 8c). This type of gas reservoir is

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a transition between the previous two types. The mercury in this gas reservoir is derived

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from source rock and deep fluids. Source rocks can be both sapropelic and humic. Since

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the fault is relatively developed, this type of gas reservoir is also developed mainly in

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a foreland basin or rift basin where strong tectonic activities are present.

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Because fluids may contain a large amount of mercury or mercury-containing

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compounds, they can have a great impact on the mercury content in gas reservoirs.

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Therefore, compared with source rocks, fluids may have a greater impact on the

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mercury content in gas reservoirs.62 Mercury concentrations in the natural gases of

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different structural units vary a lot. For example, the highest mercury concentration

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Southwest Depression of the Tarim Basin China was found in the zone of strong

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structural activities, with an average of mercury content in the natural gas of 156095.57

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ng/m3.63 The genetic model of mercury in the three kinds of gas reservoirs is of great 12


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significance in understanding the source of mercury in natural gas and preventing

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mercury-poisoning accidents in natural gas exploration and development.

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5. Conclusion

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In the thermal simulation experiment of hydrocarbon generation from kerogen,

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liquid mercury beads in an enriched state are discovered for the first time, providing

6

some kind of direct evidence that mercury can be released from coal-derived source

7

rocks during maturation. Contents of mercury in simulated gas range from 372.5 ng/m3

8

to 2776.3 ng/m3. The simulation experiment shows mass distribution of liquid mercury

9

beads between 0.0083 g and 0.2242 g; and yields of liquid mercury distributes from

10

0.3102 ×10−3 g/g to 7.4312 ×10−3 g/g kerogen. Combined with simulation experiments

11

and previous studies, we proposes three basic genetic models of mercury in gas

12

reservoirs: source-rock controlling type, fault-controlling type, and source-rock/fault

13

joint controlling type. Mercury in the source-rock-controlling type of gas reservoir is

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derived mainly from source rocks, which are primarily coal measures. Mercury in fault-

15

controlled gas reservoirs is derived mainly from deep fluids. Mercury in source rocks

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contributes relatively less to gas reservoirs and generally develops in tectonic active

17

zones. The source-rock/fault joint controlling type is the transition between the previous

18

two types, and sources rock can be both sapropelic type and humic type.

19 20

Corresponding Authors

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*E-mail: [email protected]

22

*E-mail: [email protected] 13


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1 2

Notes

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The authors declare no competing financial interest.

4 5

ORCID

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Weilong Peng: 0000-0003-3608-3170

7 8

Acknowledgements

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We would like to thank Prof. Jinxing Dai, academician of the Chinese Academy

10

of Sciences, for his generous guidance and supervision, and Prof. Jingkui Mi for his

11

providing sample. Thanks to Academician Yongsheng Ma from Chinese Academy of

12

Engineering for his concern and help to the authors.We also appreciate the guidance of

13

the laboratory staff from the National Key Laboratory of petroleum geochemistry of

14

Research Institute of Petroleum Exploration and Development of PetroChina in the

15

process of experiment. This work is financially supported by the China National

16

Science & Technology Special Project (Grant No. 2016ZX05007-01), the Strategic

17

Priority Research Program of Chinese Academy of Sciences (Grant No.

18

XDA14010404), and the National Natural Science Foundation of China (Grant No:

19

41625009, 41802161).

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References

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Page 24 of 33

Table 1. Geochemical parameters of coal sample. RO (%)

TOC (%)

Tmax (ºC)

S1 (mg/g)

S2 (mg/g)

0.55

58.3

424

0.66

97.18

Maceral group (%) Exinite

Vitrinite

Sapropelinite

Inertinite

5

85

0

10

24


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Energy & Fuels

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Table 2. Main geochemical parameters obtained by thermal simulation experiment on humic kerogen.

Sample weight (g)

3 4

Gas component (%)

Temperature

Dryness

δ13C (VPDB, ‰)

δD (‰, VSMOW)

Mercury

Liquid

Mercury yield

mercury (g)

10−3(g/g)

/

0.1015

2.0107

−299

467.6

0.0253

0.8453

−35.7

−288

1575.3

0.1018

3.4839

0.716

−36.0

−284

888.4

/

/

31.61

0.752

−31.2

−274

2776.3

/

/

0.47

31.62

0.796

−30.6

−257

1634.0

/

/

2.89

0.95

15.83

0.913

−28.0

−229

2149.3

0.1570

5.1324

1.58

3.17

0.84

23.16

0.914

−26.4

−193

372.5

0.2242

7.4312

0.09

3.40

2.99

0.87

17.51

0.922

−26.5

−165

2741.2

0.0933

3.1235

0.05

0.08

2.30

2.49

0.88

14.32

0.952

−26.4

−147

2044.4

0.0083

0.3102

0.02

0.09

1.37

2.93

0.90

11.12

0.963

−26.2

−136

557.9

/

/

0.00

0.03

1.11

2.64

0.75

4.71

0.994

−24.1

−134

1316.4

/

/

(ºC)

CO2

coefficient

CH4

C2H6

C3H8

C4H10

C5H12

C6+

N2

H2

CO

CH4

CH4

50.48

320

10.65

3.87

2.16

0.82

0.23

0.08

6.40

n.d.

0.90

74.90

0.601

−33.0

−300

29.93

340

17.54

7.04

3.31

1.10

0.33

0.18

2.47

n.d.

1.00

67.03

0.598

−34.8

29.22

360

25.89

9.93

4.48

1.51

0.44

0.16

4.02

n.d.

0.70

52.87

0.613

50.15

380

31.01

8.26

2.92

0.89

0.25

0.16

2.02

7.14

1.14

46.19

40.5

400

47.87

10.78

3.52

1.13

0.34

0.14

1.43

2.67

0.51

34.69

420

50.64

8.34

3.16

1.18

0.31

0.11

1.28

2.89

30.59

440

70.48

4.79

1.32

0.45

0.15

0.08

3.07

30.17

460

65.07

4.38

1.23

0.36

0.13

0.08

29.87

480

69.30

4.53

1.06

0.18

0.06

26.76 20.4

500

76.09

3.11

0.54

0.14

525

80.51

2.87

0.15

0.05

19.6

550

90.24

0.43

0.07

0.01

Note: "/" indicates no data."n.d." means not detected.

25


content in gas ng /m3

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1 2

Fig 1. Location map of sampling point.

26


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Fig 2. Organic maceral characteristics of coal sample from Shaping Mine, Ordos Basin, China.

27


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1 2

Fig 3. Schematic diagram of thermal-simulation experimental device.

28


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1 2

Fig 4. δ13C1 versus temperature (a), and δD1 versus temperature (b).

29


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1 2

Fig 5. Liquid mercury collected in thermal simulation experiment.

30


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Energy & Fuels

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Fig 6. Yield of liquid mercury in thermal simulation experiment.

31


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1 2

Fig 7. Relationship between methane content and temperature in thermal simulation experiment.

32


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3 4 5

Fig 8. Genetic model of mercury in gas reservoirs; (a) source-rock controlling type; (b) fault controlling type; and (c) source rock/fault joint controlling type

33


First Discovery and Significance of Liquid Mercury in a Thermal

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