The microbial activity in development of hydrocarbon microseepage: an indicator for oil and gas exploration

Mohammed A. Rasheed,M. Lakshmi,M.S. Kalpana,A.M. Dayal,D.J. Patil 한국지질과학협의회 2013 Geosciences Journal Vol.17 No.3

Geomicrobial prospecting for hydrocarbons is an exploration method based on the seepage of lighter hydrocarbons from oil/gas reservoirs to the surface and their utilization by hydrocarbon oxidizing bacteria. These bacteria utilize the hydrocarbons as their sole source of food and are found to be enriched in the near surface soils/sediments above the oil and gas reservoirs. The detection of anomalous populations of hydrocarbon utilizing bacteria in the surface soils can help to evaluate the prospects for hydrocarbon exploration. Geomicrobial prospecting studies have been carried out to test the efficacy of surface geochemical methods as regional evaluation tools in the petroliferous region of Mehsana Block, North Cambay Basin, Gujarat and to investigate whether the geomicrobial anomalies can establish an upward migration of hydrocarbons from the deep subsurface. In the present study, bacterial counts for n-pentane utilizing bacteria range between 1.0×102 and 9.80×105 cfu/g and and n-hexane utilizing bacteria range between 1.0×102 and 9.20×105 cfu/g. The bacterial concentration distribution maps show four distinct anomalies in the study area. The possibility of discovering oil or gas reservoirs using the microbiological method is emphasized by the fact that the hydrocarbon oxidizing bacteria range between 103 and 106 cfu/g in soil/sediment receiving hydrocarbon microseepages. In the present study area of the Mehsana Block of Cambay Basin, n-pentane and n-hexane utilizing bacteria show 105 cfu/g of soil sample, which is significant and thereby substantiates the seepage of lighter hydrocarbons from oil and gas reservoirs. Geomicrobial prospecting method has shown good correlation with existing oil/ gas fields of Mehsana, Gujarat.

Vegetation stress as chief indicator for detection of hydrocarbon microseepage in regions of north-eastern India

Rahul Kashyap 대한공간정보학회 2022 Spatial Information Research Vol.30 No.5

Hydrocarbons are of significance for economic and environmental standpoints. Hydrocarbon microseepage alters the surface properties of land. Here, the detection of potential hydrocarbon microoseepage zone based on vegetation stress is carried out in the north-eastern Indian states of Assam and Meghalaya. A weighted overlay model, fed by 11 spectral wide and narrow band vegetation indices (VIs), is used to determine the effective VIs for detecting vegetation stress. Mineral alteration indices are also employed as proxies to detect potential hydrocarbon microseepage sites. Mineral alteration zones exhibiting vegetation stress are speculated to be potential hydrocarbon microseepage sites. VIs such as Red Edge Normalized Difference Vegetation Index (RENDVI), Normalized Difference Vegetation Index (NDVI), Lichtenthaler Index 1 (LIC1) and Simple Ratio Index (SRI) are more effective in detecting vegetation stress as they are sensitive to minor variations in chlorophyll content. The predominant vegetation stress is detected in south-east region of the study area in Jowai around Jaintia hills. The mineral alteration indices confirms that it is a potential hydrocarbon microseepage zone. Thus, remote sensing data can serve the dual purpose of fuel resource exploration and pollution source detection at once being cost effective, hazard free and convenient.

Universal Indicators for Oil and Gas Prospecting Based on Bacterial Communities Shaped by Light-Hydrocarbon Microseepage in China

( Chunping Deng ),( Xuejian Yu ),( Jinshui Yang ),( Baozhen Li ),( Weilin Sun ),( Hongli Yuan ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.6

Light hydrocarbons accumulated in subsurface soil by long-term microseepage could favor the anomalous growth of indigenous hydrocarbon-oxidizing microorganisms, which could be crucial indicators of underlying petroleum reservoirs. Here, Illumina MiSeq sequencing of the 16S rRNA gene was conducted to determine the bacterial community structures in soil samples collected from three typical oil and gas fields at different locations in China. Incubation with n-butane at the laboratory scale was performed to confirm the presence of "universal microbes" in light-hydrocarbon microseepage ecosystems. The results indicated significantly higher bacterial diversity in next-to-well samples compared with background samples at two of the three sites, which were notably different to oil-contaminated environments. Variation partitioning analysis showed that the bacterial community structures above the oil and gas fields at the scale of the present study were shaped mainly by environmental parameters, and geographic location was able to explain only 7.05% of the variation independently. The linear discriminant analysis effect size method revealed that the oil and gas fields significantly favored the growth of Mycobacterium, Flavobacterium, and Pseudomonas, as well as other related bacteria. The relative abundance of Mycobacterium and Pseudomonas increased notably after n-butane cultivation, which highlighted their potential as biomarkers of underlying oil deposits. This work contributes to a broader perspective on the bacterial community structures shaped by long-term light-hydrocarbon microseepage and proposes relatively universal indicators, providing an additional resource for the improvement of microbial prospecting of oil and gas.

Evidence for a relationship between hydrocarbon microseepage and trace metal anomalies: an implication for petroleum exploration

Todupunuri Madhavi,Munnuru S. Kalpana,Dattatray J. Patil,Anurodh M. Dayal 한국지질과학협의회 2011 Geosciences Journal Vol.15 No.2

The paper reports the role of hydrocarbon microseepage in surface alterations of trace metal concentrations. In this study trace metal alterations were mapped that appear to be associated with hydrocarbon microseepages in the oil/gas fields of Mehsana block, North Cambay basin, India. The ranges of adsorbed soil gas concentrations of Methane, Ethane, Propane, i-Butane and n-Butane are found to vary from 1–402 ppb, 1–135 ppb, 1–70 ppb, 1–9 ppb, 1–18 ppb respectively, suggesting the presence of hydrocarbons and microseepage associated with the study area. The carbon isotopic signature of methane ranged from –29.5 to –43.0‰ (PDB) and ethane from –19.1 to –20.9‰ (PDB), indicating a thermogenic source of hydrocarbons. The absence of any significant correlation of Total Organic Carbon (TOC) and Total Inorganic Carbon (TIC) (r = 0.1 and 0.5 respectively) content with hydrocarbons in soil samples demonstrates the catagenetic origin of the desorbed gases. The Trace metal concentrations varied in the following manner: Ni: 49–155 ppm, V: 67–158 ppm, Cu: 29–82 ppm, Zn: 64–327 ppm, Ba: 241–554 ppm and Sr: 118–892 ppm. These high concentrations of trace metals which are more than their respective average concentrations generally found in soils are indicative of hydrocarbon induced alterations in the area. The low Eh values observed in anomalous hydrocarbon bearing soil samples compared to non anomalous samples in the area, could be attributed to the reducing conditions created by the hydrocarbon seepage from subsurface and might have influenced the trace metal solubilities which is reflected in their increased concentrations. Trace metal anomalies are seen haloed to adsorbed soil gas anomalies (∑C_(2+)) indicating that the major generative depressions of oil and /or gas fields of Sobhasan / Linch in the study area promoted vertical migration of hydrocarbon microbubbles which in turn facilitated trace metal deposition in the surface soils. By using integrated method approach, the weak signal of oil and gas reservoirs could be amplified in the frontier areas and the uncertainity of the vertical correlation of surface anomalies could be reduced

Universal Indicators for Oil and Gas Prospecting Based on Bacterial Communities Shaped by Light-Hydrocarbon Microseepage in China

Deng, Chunping,Yu, Xuejian,Yang, Jinshui,Li, Baozhen,Sun, Weilin,Yuan, Hongli The Korean Society for Microbiology and Biotechnol 2016 Journal of microbiology and biotechnology Vol.26 No.7

Light hydrocarbons accumulated in subsurface soil by long-term microseepage could favor the anomalous growth of indigenous hydrocarbon-oxidizing microorganisms, which could be crucial indicators of underlying petroleum reservoirs. Here, Illumina MiSeq sequencing of the 16S rRNA gene was conducted to determine the bacterial community structures in soil samples collected from three typical oil and gas fields at different locations in China. Incubation with n-butane at the laboratory scale was performed to confirm the presence of "universal microbes" in light-hydrocarbon microseepage ecosystems. The results indicated significantly higher bacterial diversity in next-to-well samples compared with background samples at two of the three sites, which were notably different to oil-contaminated environments. Variation partitioning analysis showed that the bacterial community structures above the oil and gas fields at the scale of the present study were shaped mainly by environmental parameters, and geographic location was able to explain only 7.05% of the variation independently. The linear discriminant analysis effect size method revealed that the oil and gas fields significantly favored the growth of Mycobacterium, Flavobacterium, and Pseudomonas, as well as other related bacteria. The relative abundance of Mycobacterium and Pseudomonas increased notably after n-butane cultivation, which highlighted their potential as biomarkers of underlying oil deposits. This work contributes to a broader perspective on the bacterial community structures shaped by long-term light-hydrocarbon microseepage and proposes relatively universal indicators, providing an additional resource for the improvement of microbial prospecting of oil and gas.