Biomonitoring Studies and Preventing the Formation of Biogenic H2S in the Wierzchowice Underground Gas Storage Facility

The article discusses the results of biomonitoring research at the Underground Gas Storage (UGS). Hydrogen sulphide, as one of the products of microbiological reaction and transformation, as well as a product of chemical reactions in rocks, is a subject of interest for global petroleum companies. The materials used in this research work were formation waters and stored natural gas. The biomonitoring of reservoir waters and cyclical analyses of the composition of gas stored at UGS Wierzchowice enabled the assessment of the microbiological condition of the reservoir environment and individual storage wells in subsequent years of operation. Investigations of the formation water from individual wells of the UGS Wierzchowice showed the presence of sulphate reducing bacteria bacteria (SRB), such as Desulfovibrio and Desulfotomaculum genera and bacteria that oxidize sulphur compounds. In the last cycles of UGS Wierzchowice, the content of hydrogen sulphide and sulphides in the reservoir waters ranged from 1.22 to 15.5 mg/dm3. The monitoring of natural gas received from UGS production wells and observation wells, which was carried out in terms of the determination of hydrogen sulphide and organic sulphur compounds, made it possible to observe changes in their content in natural gas in individual storage cycles. In the last cycles of UGS Wierzchowice, the content of hydrogen sulphide in natural gas from production wells ranged from 0.69 to 2.89 mg/dm3, and the content of organic sulphur compounds converted to elemental sulphur ranged from 0.055 to 0.130 mg Sel./Nm3. A higher hydrogen sulphide content was recorded in natural gas from observation wells in the range of 2.02–25.15 mg/Nm3. In order to explain the causes of hydrogen sulphide formation at UGS Wierzchowice, isotopic analyses were performed to determine the isotope composition of δ34SH2S, δ34SSO4, δ18OSO4 in natural gas samples (production and observation wells) and in the deep sample of reservoir water. The results of isotope tests in connection with microbiological tests, chromatographic analyses of sulphur compounds in natural gas collected from UGS Wierzchowice and an analysis of the geological structure of the Wierzchowice deposit allow us to conclude that the dominant processes responsible for the formation of hydrogen sulphide at UGS Wierzchowice are microbiological, consisting of microbial sulphate reduction (MSR). The presented tests allow for the control and maintenance of hydrogen sulphide at a low level in the natural gas received from the Wierzchowice Underground Gas Storage facility.

Depth-wise fractionation of sulphur in cultivated soils of low and mid hills of Himachal Pradesh

The current investigation was conducted to study the fractions of sulphur in nine districts of low and mid hills of Himachal Pradesh. For this purpose 31 representative soil sampling sites were selected from nine districts and the soil samples were analyzed for physicochemical properties and different fractions of sulphur (water soluble sulphur, exchangeable sulphur, available sulphur, non-sulphate sulphur, organic sulphur and total sulphur). The results indicated that the total sulphur in soils varied from 98.2 to 470.1 mg kg-1 in surface soil (0-15 cm) and 67.2 to 370.7 mg kg-1 in sub-surface layer (15-60 cm). The organic sulphur varied from 80.5 to 401.1 mg kg-1 in surface and 44 to 306.1 mg kg-1 in sub-surface layer. The water soluble sulphur, exchangeable sulphur, available sulphur and non-sulphate sulphur varied from 1.7 to 9.2, 2.7 to 18.4, 4.5 to 27.6 and 10.2 to 58.9 mg kg-1 respectively in surface soil and 0.5 to 5.4, 1 to 17.7, 3.7 to 23.5 and 12.5 to 50.2 mg kg-1, respectively in sub-surface soil. It was observed during course of study that with increase in the soil depth the content of different fractions of sulphur decreased. These soils had the major part of their total sulphur content in organic form followed by non-sulphate sulphur, available sulphur, exchangeable sulphur and water soluble sulphur. It can be concluded that the soil texture and organic carbon content played a major role in determining the quantity of different fractions of sulphur in these soils.

Analysis of Organic Sulphur Compounds in Coal Tar by Using Comprehensive Two-Dimensional Gas Chromatography-High Resolution Time-of-Flight Mass Spectrometry

Coal tar is a complex mixture of organic compounds obtained from the thermal treatment of coal; it contains several different chemical classes of compounds, such as polycyclic aromatic hydrocarbons, phenols and different heterocyclic compounds including sulphur derivatives. In the present research, a target analysis was carried out for the characterisation of fourteen different classes of organic sulphur compounds in coal tar by using cryogenically-modulated (CM) comprehensive two-dimensional gas chromatography-high resolution time-of-flight mass spectrometry (GC×GC-HR ToFMS) with the support of target analyte finding, a specific software function. Furthermore, absolute quantification data were obtained by using eight pure standard sulphur compounds, and 1-fluoronaphthalene as internal standard. Several figures-of-merit of the proposed method were measured (linearity, intra-day precision, limits of detection and quantification). Finally, the overall analytical performance of CM GC×GC-HR ToFMS was evaluated, in relation to MS similarities, mass accuracies, second-dimension peak widths, peak capacity and tailing factors. The approach proved itself as being a powerful analytical platform, benefiting from the high sensitivity, selectivity and resolving power, of both the GC and MS sides.