Geo-microbial Prospecting Method For Hydrocarbon Exploration


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Geo-microbial Prospecting Method For Hydrocarbon Exploration : 

Geo-microbial Prospecting Method For Hydrocarbon Exploration Presented by: Akhilesh Kumar Maury R040307003 APE- Upstream

Introduction : 

Introduction Geo-microbial prospecting for hydrocarbons is an exploration method based on the seepage of light gaseous hydrocarbons from oil/gas reservoirs towards the surface and their utilization by hydrocarbon-oxidizing bacteria1. The detection of anomalous populations of methane, ethane and propane-oxidizing bacteria in the surface soils or sediments, helps to evaluate the prospects for hydrocarbon exploration.

Theory : 

Theory It is an exploration method based on the premise that the light gaseous hydrocarbons, namely methane (C1), ethane (C2), propane (C3) and butane (C4) migrate upward from subsurface petroleum accumulations by diffusion and effusion, and are utilized by a variety of microorganisms present in the sub-soil ecosystem. These bacteria(methane- oxidizing bacteria, ethane- oxidizing bacteria and propane- oxidizing bacteria) are mostly found enriched in the shallow soils/sediments above hydrocarbon-bearing structures and can differentiate between hydrocarbon prospective and non-prospective areas.

Merits of MPOG : 

Merits of MPOG Success rate for Microbial Prospecting for Oil and Gas (MPOG) method has been reported to be 90%. This method can be integrated with geological, geochemical and geophysical methods to evaluate the hydrocarbon prospect of an area and to prioritize the drilling locations, thereby reducing drilling risks and achieving higher success in petroleum exploration.

Process : 

Process Sampling Soil samples about 100 g each are collected in pre-sterilized whirl-pack bags under aseptic conditions from a depth of about 1 m and stored at 2–4°C for microbial analysis. Isolation of hydrocarbon-oxidizing bacteria Isolation and enumeration of methane, ethane and propane-oxidizing bacteria for each sample are carried out by the Standard Plate Count (SPC) method. One gram of soil sample is suspended in 9 ml of pre-sterilized water for the preparation of decimal dilutions (10–1 to 10–5).

Slide 6: 

0.1 ml aliquot of each dilution is plated onto Mineral Salts Medium (MSM) containing Petri plates. These plates are placed in glass desiccators filled with desired hydrocarbon gas (methane/ethane/propane with 99.999% purity) and zero air (purified atmospheric gas devoid of hydrocarbons) in the ratio (1 : 1). Desiccators were kept in a bacteriological incubator at 35 ± 2°C for 10 days. After incubation, the developed bacterial colonies of methane, ethane and propane-oxidizing bacteria are manually counted using a colony counter and reported in colony forming units (cfu/g) of soil sample. [Note: For isolation of methane-oxidizing bacteria, the desiccators was filled with methane gas and zero air and similarly for EOB and POB.]

Process summary2 : 

Process summary2 Weight the soil sample Add sterile distilled water Fiillter organiic matter filtering pad and membrane Remove the pad and discard Remove the membrane Put on a plate containing agarized Mineral Salt Medium Put in the sealed container Incubate in atmosphere with air and butane at 35 °C for 10 days

Inferences : 

Inferences The soil samples collected are analyzed for the presence of methane, ethane and propane-oxidizing bacteria using SPC method. Bacteria which are able to utilize methane/ethane/propane gas as a sole carbon source, are merely developed as colonies on the MSM plates. Hydrocarbon gases are provided externally for the growth of bacteria. The positive growth in test samples after incubation, indicates that methane/ethane/propane-oxidizing bacterial colonies are developed utilizing the given hydrocarbon gases. Thus microbial prospecting study is based on the determination of bacterial cell concentration of hydrocarbon oxidizers in the soils.

Refrences : 

Refrences M. A. Rasheed, M. Veena Prasanna, T. Satish Kumar, D. J. Patil and A. M. Dayal, Geomicrobial prospecting method for hydrocarbon exploration in Vengannapalli Village, Cuddapah Basin, National Geophysical Research Institute , India p2-6. Fernando Larriestra, A Modified Method of Microbial Analysis for Oil Exploration and its Application on Five Basins of Southern and Western Argentina, December 31, 2010, p5-8.

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Vengannapalli Village,Potuluru Mandal, Anantapur District, Andhra Pradesh1 : 

Vengannapalli Village,Potuluru Mandal, Anantapur District, Andhra Pradesh1 In the present study, bacterial counts was reported as high as (5.4 × 105 cfu/g) for Methane, (5.5 × 105 cfu/g) for ethane and (4.6 × 104cfu/g) for propane-oxidizing bacteria .

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Methane-oxidizing bacterial concentration map Composite anomaly map of methane-oxidizing bacteria and adsorbed methane.

Slide 14: 

Ethane-oxidizing bacterial concentration map Composite anomaly map of ethane-oxidizing bacteria and adsorbed ethane

Slide 15: 

Propane-oxidizing bacterial concentration map. Composite anomaly map of propane-oxidizing bacteria and adsorbed propane

Conclusion : 

Conclusion The microbial results indicate the presence of high bacterial concentrations for methane, ethane and significant propane-oxidizing bacterial populations in Vengannapalli village. Added geological and geophysical studies reveal that Tadpatri shales (Chitravati Group) can be a potential source rocks for hydrocarbons, having the essential prerequisites such as their undisturbed nature favorable for the generation and accumulation of hydrocarbons