High abundance of alkylated diamondoids, thiadiamondoids and thioaromatics in recently discovered sulfur-rich LS2 condensate in the Tarim Basin

Zhu, Guangyou; Zhang, Ying; Zhang, Zhiyao; Li, Tingting; He, Nianpeng; Grice, Kliti; Neng, Yuan; Greenwood, Paul F.

doi:10.1016/j.orggeochem.2018.07.003

Cited by 25 publications

(27 citation statements)

References 36 publications

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“…The total thiadiamondoid concentration in LS2 condensate is 300 μg/g, which is higher than that of other crude oils from the Tarim Basin except for ZS1C condensate. Combined with the elevated H 2 S (3.66%) content in the associated gas and 34 S enrichment of the H 2 S (20.16‰), it can be concluded that LS2 condensate experienced severe TSR alteration . The absence of sulfate minerals in the reservoir implies that the LS2 condensate migrated from TSR-impacted intervals in the Ordovician reservoirs.…”

Section: Resultsmentioning

confidence: 98%

“…It is interesting that thiols with 3 DBEs showed much higher relative abundance in the ZS1C oil than those in the LS2 oil. Thiols with 3 DBE in ZS1C and LS2 oils are speculated to be diamondoidthiols, for abundant diamondoids and thiadiamondoids were discovered in them. , However, FT-ICR MS results cannot provide structural information on these molecules.…”

Section: Resultsmentioning

confidence: 99%

“…The Penglaiba Formation is mainly comprised of thick-bedded grey dolomitic limestone, and some light grey limestone with thin beds of grey dolomitic conglomerates, which also occur in the middle and lower sections. The Carboniferous and Permian strata are typical marine–terrigenous units that serve as seals . The Bachu uplift is located adjacent to the Maigaiti slope in the southwest Tarim Basin.…”

Section: Geological Settingmentioning

confidence: 99%

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Occurrence and Origins of Thiols in Deep Strata Crude Oils, Tarim Basin, China

Zhu

Wang

et al. 2019

ACS Earth Space Chem.

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Thiols (or mercaptans) in crude oils have been considered to be associated with thermochemical sulfate reduction (TSR). However, the molecular composition and the formation mechanism of thiols in crude oils are not clear. This study provides the molecular composition of thiols in several deep strata condensate oils (condensates) from the Tarim Basin. Selective Michael addition products of thiols were characterized using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and comprehensive two-dimensional gas chromatography–MS (GC × GC MS). The carbon numbers and double bond equivalents of the thiols ranged between 4–20 and 0–10, respectively. Abundant diamondoidthiols found in two condensates were from high-temperature reservoirs. Various thiol compounds with multiple heteroatoms (S2, S3, S1O1, S1O2, and S2O1 class species) were detected in two other condensates, and low reservoir temperature made it possible to prevent the depletion of the multiple-heteroatom thiols. The pronounced 34S enrichment in H2S and high abundance of thiadiamondoids indicate that four condensates were originally sourced from Cambrian strata and suffered severe TSR alteration. The pathway of thiol formation was speculated as follows: TSR-generated H2S reacts with petroleum hydrocarbons. Deep Cambrian strata in the Tarim Basin has the potential of being a huge hydrocarbon resource, although the high maturity and TSR alteration may negatively impact the quantity and quality of reserves and lead to a high H2S content. The results presented here provide new insights into the TSR reaction, which may assist deep oil exploration and facilitate evaluation of the extent of TSR alteration.

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

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Occurrence and Origins of Thiols in Deep Strata Crude Oils, Tarim Basin, China

Zhu

Wang

et al. 2019

ACS Earth Space Chem.

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“…In fact, these caves are not empty; they are filled by various fillings, including breccias, sedimentary fillings, and chemical fillings [10,23,26,27,41]. In present, the formation depth is generally greater than 5500 m, with ultra-high temperature (>125 • C) and high pressure (>60 MPa) [49].…”

Section: Methodsmentioning

confidence: 98%

Three-Dimensional Geophysical Characterization of Deeply Buried Paleokarst System in the Tahe Oilfield, Tarim Basin, China

Tian

Wang

Fang

et al. 2019

Water

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Paleokarst reservoirs are the major type of the Ordovician carbonate reservoirs in the Tahe Oilfield. Due to the strong heterogeneity in distribution, it is a real challenge to detect the spatial distribution of paleokarst reservoirs, especially those deeply buried more than 5500 m in the Tahe area. Based on the abundant core samples, this paper first described the structure of paleocaves drilled by well. Second, after time–depth conversions, the results from drilled wells were tied to three-dimensional (3D) seismic datasets, and then the threshold of host rocks and caves in wave impedance were identified. Third, the seismic-scale mapping and visualization of the paleokarst reservoirs were achieved by tracing the distribution of paleocaves. This approach was applied in the well T403 area, and the structure of the paleokarst, especially the runoff zone, was interpreted. 3D structure and spatial distribution of the paleokarst system was demonstrated by plane, vertical, and 3D models. Additionally, according to the hydrology genetic relationships, the paleocaves in the runoff zone were divided into sinkholes, main channel, and branch channel. The approach of a 3D geophysical characterization of a deeply buried paleokarst system can be applicable to Tahe and other similar paleokarst oilfields, which will guide hydrocarbon exploration in paleokarst reservoirs.

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“…H 2 S formed by hydrocarbon oxidation and sulfate reduction can in turn act as a catalyst to react with the dissolved form of sulfate to form S 0 , so the production of H 2 S was less. The possible reactions are as follows [8,26,27…”

Section: Geofluidsmentioning

confidence: 99%

Simulation Experiment of TSR Promotes Cracking of Coal Generation H2S

Deng

Yan-jie

et al. 2021

Geofluids

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Thermochemical sulfate reduction (TSR) is one of the main contributors to the formation of hydrogen sulfide (H2S) in coal seam strata. Four reaction systems (coal, coal+water, coal+water and MgSO4, and coal+water and MgSO4 and AlCl3) were selected and simulated from 250°C to 600°C with eight temperature steps using a high-temperature and high-pressure reaction device, and the evolution characteristics of the gaseous products of hydrocarbons (methane, C2-5) and nonhydrocarbon gases (CO2, H2, and H2S) were studied. Thermal simulation experiments showed that the TSR led to the reduction of heavy hydrocarbons, and the presence of salts accelerated the evolution of hydrocarbons; SO42-, Al3+, and Mg2+ had a certain promoting effect on the TSR, which increased the total amount of alkane gas, H2S, and CO2 production. Improving the salinity of the reaction system can promote the occurrence of TSR, and water plays a key role in hydrocarbon generation evolution and the TSR.

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High abundance of alkylated diamondoids, thiadiamondoids and thioaromatics in recently discovered sulfur-rich LS2 condensate in the Tarim Basin

Cited by 25 publications

References 36 publications

Occurrence and Origins of Thiols in Deep Strata Crude Oils, Tarim Basin, China

Occurrence and Origins of Thiols in Deep Strata Crude Oils, Tarim Basin, China

Three-Dimensional Geophysical Characterization of Deeply Buried Paleokarst System in the Tahe Oilfield, Tarim Basin, China

Simulation Experiment of TSR Promotes Cracking of Coal Generation H2S

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