International Journal of Engineering, Management & Sciences (IJEMS) ISSN-2348 –3733, Volume-3, Issue-9, September 2016 Mossbauer Studies on The Test Well P#1 Located in Phulasar Structure of Bikaner-Nagaur Basin of Rajasthan, India

Samay Singh Meena, Sahi Ram, Beena Bhatia ,R.P.Tripathi

 oil and gases, while those containing type III can generate dry Abstract— The study of chemical state of iron in deep surface gases (CH4, CO2, N2 ). Therefore, the nature of the kerogen sedimentary samples provide crucial information about the present in the sediments is one of the principle factors during redox environment which was present during their burial. For the process of maturation [1]. A source rocks in is said to be the characterization of iron-bearing minerals and to study their mature when hydrocarbon generation takes places, and post relative distribution with depth, 57Fe Mössbauer spectroscopy mature when the hydrocarbon are burnt out. has been regarded as the most suitable technique due to its extreme sensitivity to the chemical environment of iron nuclei . The sedimentary source rocks comprises of both organic and It is a non destructive technique so the sample either in powder inorganic solid phase. The factors which determine the form or thin slice does not gets altered and in a single run it can variation of the composition of inorganic solid phase also provide information about all the iron phases present in the controls the physicochemical transformation of organic sample. matter. In the phase of evolution of inorganic solid phases Sedimentary samples collected from different depth in well the biological activity in early stage and redox environment P#1 drilled in Phulasar structure of Bikaner-Nagaur basin of also decides the evolution of organic matter in sediments. Rajasthan, India has been studied to understand the relative Furthermore, organic-inorganic interaction can occur at distribution of iron bearing minerals with depth and to see if different stages of the sedimentary evolution . Thus, the the iron mineralogy of Bikaner-Nagaur basin can provide some mineralogical analysis of sediments is considered important. information which can be useful in hydrocarbon prospecting in this basin. In present study, The mineral ankerite is observed Iron-bearing minerals form an important component of all only in those lower depth sequences which contains source rocks sediments including organic rich sediments (source rocks). in this basin is quite significant in context to the hydrocarbon Composition of individual minerals, impurity inclusions, prospecting in this basin. relative abundance etc gives useful information about the Index Terms— iron-bearing minerals, Mössbauer geochemical history of the sediments and plays an important spectroscopy, source rock. role in determination of redox environment in the sediments. 57Fe Mössbauer spectroscopy is particularly useful for the characterization of iron-bearing minerals in sedimentary I. INTRODUCTION samples as it probes the local environment of iron nuclei quite sensitively. This method offers certain advantages, over other The Rajasthan petroliferous region is a part of Thar desert conventional techniques such as chemical, optical or electron covering 1,20,000 sq. km area to the west of Arawali and is microscopic analysis techniques. Indeed each technique has divided into four sub basins (i) Jaisalmer basin (ii) its own strength, but Mössbauer spectroscopy can give results Bikaner-Nagaur basin (iii) Shahgarh-Miajlar basin and (iv) by a quick, reliable and simple method. It is a non-destructive Barmer-Sanchor basin. The sedimentary sequences deposited technique in the sense that the nature of sample, kept in the in Mesozoic, late Proterozoic and Permian era are believed to form of power or thin slice is not altered during the contain source rocks and hence are the main target for experiment. Also, in a single run, we can get information exploration of oil/gas in this basin. about all the iron minerals, by proper deconvolution of Sediments rich in organic matter are known as source rocks. spectrum [2]. The organic matter deposited in sediments is mainly is Humic On the basis of Mössbauer spectroscopic studies earlier (derived from terrestrial plants ) or Sapropelic (derived from reported by our group [3-7] on Jaisalmer basin and those algae and marine life). Most of this organic matter in reported by Mөrup et. al. [8,9] on Danish North sea oil field, sediments ultimately changes into insoluble organic matter, Mössbauer spectroscopy has potential to provide information termed „Kerogen‟. It can be divided into three types ; Type I, about (a) redox conditions of organic rich sediments and, (b) II and III. Rocks containing Type I & II kerogen can generate paleo-environment of deposition of the organic sediments.

In present work, sedimentary samples collected from Samay Singh Meena, Department of Physics, Jai Narain Vyas o University, Jodhpur, Rajasthan, India different depths of well P # 1 located at latitude 26 41‟ And Sahi Ram, , Department of Physics, Jai Narain Vyas University, Jodhpur, longitude 71o85' drilled in Phulasar structure of Rajasthan, India Bikaner-Nagaur basin of Rajasthan, India has been Beena Bhatia , Department of Physics, Jai Narain Vyas University, Jodhpur, Rajasthan, India investigated using Mössbauer spectroscopy. Starting from the R.P.Tripathi, Department of Physics, Jai Narain Vyas University, top, well P #1 penetrates through the following rock Jodhpur, Rajasthan, India formations viz., Nagaur formation, HEG formation, Bilara formation, Jodhpur formation and Malani formation. The .

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Bilara formation deposited in early Paleozoic era and Jodhpur values for components AA/ and BB/ is very little while the formation deposited in Neoproterozoic era are believed to parameters for clay minerals show remarkable variation. This contain the source rocks in this basin. The aim of present is because the variation in the composition of pyrite and study is to (i) understand the distribution of iron-bearing siderite due to impurities affects less towards QS and IS minerals with depths and (ii) to see if a correlation exist values while clay forming minerals may have a variety of between the iron-mineralogy and hydrocarbon prospecting in iron-bearing minerals with varying structure and composition this basin. resulting into large variation in QS and IS values various clay forming minerals[11]. The relative amounts of various II. EXPERIMENTAL iron-bearing minerals as a function of depths in well P#1 are Mössbauer absorbers were prepared by sandwiching finely displayed in figure 2. ground sediment samples between two paper discs in a Nagaur Formation : (1126-1248 m) sample holder (25 mm in diameter). The thickness of In this formation, all analyzed samples have shown presence of iron in clay minerals, Sulphide along with remarkable absorbers was always kept constant. Mössbauer spectra were 3+ amount of α- Fe2O3 .Iron in Fe state is found present in large recorded at room temperature (300K) with a conventional 2+ constant acceleration spectrometer using a 10 m Ci source in amount in comparison to iron in Fe state in all samples. Sample studied from depth 1190-92 m showed the presence a Pd-matrix. Detailed of the experimental set-up are similar 2+ 3+ as reported earlier by Nigam at al [3]. The isomer shift (IS) of pyrite in small amount along with Fe and Fe clay. has been reported with respect to the centroid of a 25 µm Interestingly at this depth mineral siderite was absent. More thick α-iron foil spectrum. Each spectrum was fitted using a ever, in all samples, the combined amount of siderite and computer program written by Meerwall [10]. This pyrite was nearly constant indicating some mutual correlation programme assume the spectrum to be sum of Lorrentzians. between the presence/absence of pyrite and siderite in these In most of cases, width and intensity of two halves of a sedimentary samples. The simultaneous presence of α-Fe2O3 quadrupole doublet were constrained to be equal. Solid lines in all samples is an indicator of rigorous oxidizing condition in the spectra reported here represent computer fitted curves [12]. and dots represent the experimental points. For the fit to be statistically acceptance, it is required that the value of HEG Formation: (1296-1388 m) parameter χ2 should lie between υ + 2.2 - 3.3√υ and υ + 2.2 + Five samples collected from different depths in this formation 2 have been studied. All the samples have shown large presence 3.3√υ. In the present study, the χ values are generally 3+ 2+ obtained in this range. However, a little deviation in the χ2 has of Fe in clay in comparison to Fe in clay. Two samples been accepted on few occasions when the iterations do not from depths 1314-16 m and 1386-88 m have shown the yield to further improvements in χ.2. Such situation arises presence of α- Fe2O3 along with carbonates and clay. This when weak lines are present. formation is identical to the Nagaur formation in context to the presence/absence of various iron-bearing minerals. III. RESULT AND DISCUSSION Bilara Formation: (1389-1449 m) This formation comprises of very small thickness zone of Mössbauer spectra of samples collected from well P#1 are around 60 m. The source rock palynological and shown in the Figure 1. The depths from whose the sample is geochemical studies reported by OIL, India, indicates the collected is mentioned in the figure itself. The Mössbauer presence of source rocks in this formation [13]. One sample spectra of all the samples were resolved into several collected from depth 1426-28 m is studied. In this sample quadrupole doublets corresponding to different minerals. The mineral ankerite is found present in appreciable amount ranges of Mössbauer parameters (quadrupole splitting and along with relatively large amount by Fe2+ in clay and small isomer shift or QS And IS values) obtained in present work amount of Fe3+ in clay in this sample, siderite is not found and their assignments on the basis of Mössbauer present. This absence of siderite and simultaneous presence spectroscopic studies reported by Nigam et. al. [3-5], Sahi of ankerite indicates late digenesis of siderite resulting into ram et. al. [6,7] and Mørup et. al. [8,9] are shown in Table 1. deposition of ankerite [14]. This precipitation of ankerite at doublets marked AA/, BB/, CC/, DD/ and EE/ are typical of 3+ certain lower depths and above 100°C is an indicator of pyrite, siderite, clay in high spin Fe state, clay in high spin reducing environment of deposition in sediments. Since Fe2+ state and [Ca, Mg, Fe] carbonates respectively. In some 3+ 2+ Bilara formation is believed to certain source rock in this samples the doublet corresponding to Fe and Fe in clay basin, the presence of ankerite in this formation can be minerals in octahedral cis and trans site in the 2:1 layer attributed to favorable redox environment for transformation silicates were also simultaneously resolved. In the case of 3+ / 3+ of organic matter into oil/gas in this basin. Fe , C1C 1 (outer ferric doublet) is attributed to Fe in more / 3+ Jodhpur Formation: (1429-1503m) distorted site and C2C 2 (inner ferric doublet) to Fe in less This formation is a thin zone of around 80 m thickness ,like as distorted site. In some samples an additional peak of Fe3+ in / 2+ Bilara formation. This formation is also believed to contain clay is also resolved and is assigned C3C3 . In the case of Fe , / 2+ / source rocks in this basin sample collected from depths 1450 D1D 1 (outer ferrous doublet) to Fe in cis site and D2D 2 2+ m has been studied. The iron-mineralogy in this formation is (outer ferrous doublet) to Fe in trans site. In some samples, identical to Bilara formation showing presence of ankerite magnetic hyperfine patters of the order of Bhelf = 520 kOe is and Fe2+ in clay and Fe3+ in clay minerals, comparing the also obtained. Those patterns are attributed to α- Fe2O3 i.e. present study with earlier reported results obtained in Danish hematite. In one sample from depth 1386-88 m a doublet North sea oil wells [8], the presence of ankerite in Bilara corresponding to very small QS value whereas IS value is / Formation present study it can be attributed that the Bilara larger, this doublet is marked as NN (Not identified). From formation and Jodhpur formation in Bikaner-Nagaur basin Table 1, it can be seen that the variation in the QS and IS

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International Journal of Engineering, Management & Sciences (IJEMS) ISSN-2348 –3733, Volume-3, Issue-9, September 2016 are deposited in good reducing environment which is [7] Sahi Ram, K.R. Patel, S.K. Sharma and R.P. Tripathi, „ Distribution favorable for transformation of organic matter into oil/gas. of Fe2+ in clay minerals in sub-surface sediments of the Jaisalmer basin(India) using Mössbauer spectroscopy, Fuel,1997,Vol. Malani Formation: (1453-1506 m) 76,No.14/15 1369 Below the Jodhpur formation, The Malani formation is [8] MØrup, S. and Lindgreen H.B., Application of Mössbauer effect, present as a thin zone of around 60 m. One sample studied ICAME, Jaipur, India, 1981; Indian National Science Academy, from depth 1504-06 m has shown presence of iron in Fe2+ New Delhi, p. 290 (1982) 3+ [9] MØrup, S., Franck, J., Wonterghem, J., Poulsen, R. and Larsen, L. and Fe in relatively equal amount along with small amount Mössbauer spectroscopy study of the chemical state of iron in of siderite. The well terminates at this depths. The geological Danish Mesozoic sediments. Fuel, 64, 539 (1985) studies have also predicated volcanic activity in this [10] Meerwall, E.V., „A least-square spectral curve fitting routine for strongly overlapping Lorentzians or Gaussians. Computer formation [13]. If we compare the distribution of iron-bearing physics communications , 1975, 9,117-128 minerals in sedimentary sequences of Bikaner-Nagaur basin [11] R.P. Tripathi, Indian journal of pure and Applied Physics, 1987, obtained in present study with the distribution of iron-bearing Vol. 25, p. 34. minerals in sedimentary sequence of Jaisalmer basin reported [12] K.R. Patel, S Ram, A. Tripathi, R. Sharm and R.P. Tripathi, „ Study of geo-chemical environment in organic rich sub-surface by [3-7], though both these investigation show presence of sediments of Jaisalmer petroliferous basin of Rajasthan, India, only four kind of iron-bearing minerals ; sulphide, using Mössbauer spectroscopy. ICAME 2009 doi: 2010, carbonates, clay minerals and oxides, but their distribution 1088/1742-6596/217/1/012061 patterns shows a distinct difference. While wells in Jaisalmer [13] S. V. Raju, N. Mathur and M. K. Sarmah; Geochemical characterization of Neoproterozoic heavy oil from Rajasthan, basin showed presence of lots of siderite with small amount India : Implications for future explorations of hydrocarbons, of pyrite in only some samples, but the relative presence of Current Science, Vol. 107, No. 8 (2014) siderite in Bikaner-Nagaur basin is very small. In Jaisalmer [14] Boles, J. R. , Contrib. Mineral. Petrol., 1978, vol. 68, p. 1978. [15] R. P. Tripathi, S. K. Sharma, K.R. Patel, K. L. Shrivastava and basin, minerals ankerite was not observed in those formation Sahi Ram; A Mössbauer approach to hydrocarbon prospecting in [15] which contains source rocks while the source rock prone Jaisalmer basin of Rajasthan, India, July 1998, Ind. J. Petrol. Formation in Bikaner-Nagaur basin showed presence of Geol., vol. 7, No. 1, pp. 47-58 (July 1998). ankerite. [16] R.P. Tripathi,Beena Bhatia, R.Sharma, K.R. Patel, S.S. Meena Et In an early work, Tripathi et.. al [16] has also shown a Al. Geoscience Frontiers xxx (2015) 1-6 correlation of iron-bearing minerals and redox environment [17] Beena Bhatia, Amita Tripathi, Ragini Sharma,R.P.Tripathi, in Jaisalmer basin and predicted poor reducing environment „Mössbauer spectroscopy study of sediments collected from test which is not favorable for generation of hydrocarbons. Thus, wells drilled in the Bikaner-Nagaur Basin, Fuel Vol.98 (2012) P.140-148 the prediction of redox environment in different basin irrespective of lithology and lithography are quit consistent with the presence/absence of iron-bearing minerals in a basin.

An extensive Mössbauer spectroscopy study on other wells drilled in Bikaner-Nagaur basin is needed to strengthen the prediction of present work.

IV. ACKNOWLEDGEMENT The authors are thankful to university grant commission,

New Delhi and Department of Science & Technology, Delhi for providing financial grants to procure radioactive source under UGC-DRS scheme. Authors are also thankful to Oil India Limited, India for providing the samples.

.

REFERENCES [1] Tissot, B. and Welte, D.H., in „Petroleum Formation and Occurrence‟, Springer-Verlag, IIn Ed., Berlin, West German P.699(1984) [2] Bancroft, G.M., in „Mössbauer spectroscopy: An Introduction for Inorganic Chemists and Geochemists, McGraw Hill Book Co., Lodon (1973) [3] A.N. Nigam, R.P. Tripathi, M.L. Jangid and M.P. Chacharkar; “Studies on corrosion of mild steel by water using Mössbauer spectroscopy”, J. RADIOANAL. Nucl. Chem. letters, Vol. 117(4), pp. 243-254, 1987. [4] Nigam, A.N., Triphati, R.P., Singh, H.S., Gambhir, R.S. and Lukose, N.G., „Mössbauer studies on Ghotaru Well No.1 of Jaisalmer Basin‟ Fuel, 68, 209 (1989) [5] Nigam, A.N., Triphati, R.P., Singh, H.S., Gambhir, R.S., „Source Rock evaluation of some wells in Jaisalmer Basin (India) using Mössbauer spectroscopy.‟ Fuel, 70, 262-266 (1989) [6] Sahi Ram, K.R. Patel, S.K. Sharma and R.P. Tripathi, „ Ditribution of iron in siderite in sub-surface sediments of Jaisalmer Basin (India)using Mössbauer spectroscopy,Fuel vol. 77, No 13,PP.1507-1512,1998

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APPENDIX Table -1 : Mössbauer parameters observed in sediments of well P#1. Depths (m) I S (mms-1) Q S (mms-1) Doublet Assignment / 3+ 0.490 0.665 C1C 1 Fe 1126-28 0.945 1.575 EE/ ankerite / 3+ -0.525 1.295 C2C 2 Fe (Low spin) 1.1025 2.450 DD/ Fe2+

0.5157 -.0260 α-Fe2O3 hematite 1190-92 0.5388 0.5014 AA/ pyrite 0.2720 0.2880 CC/ Fe3+ 1.2697 2.3687 DD/ Fe2+

0.4623 -0.65 α-Fe2O3 hematite / 3+ 1212-14 0.5708 0.7575 C1C1 Fe / 3+ ( 0.4854 0.1173 C2C2 Fe Low spin) / 1.4777 1.9099 BB siderite / 3+ 0.0175 0.420 C2C2 Fe (Low spin) / 3+ 1246-48 0.6037 0.3675 C1C1 Fe / 2+ 1.0342 2.1385 D1D1 Fe / 2+ 1.1725 2.5515 D2D2 Fe / 3+ 0.1695 0.0385 C1C1 Fe (Low spin) / 3+ 0.4112 0.3255 C2C2 Fe / 3+ 1296-98 0.2152 0.5285 C3C3 Fe 1.232 2.359 DD/ Fe2+

0.5263 -1.025 α-Fe2O3 hematite 0.4908 0.4908 AA/ pyrite 1314-16 0.6402 0.7682 CC/ Fe 3+ 1.440 2.6248 BB/ siderite / 3+ 0.1697 0.4865 C1C1 Fe (Low spin) / 3+ 0.4655 0.8050 C2C2 Fe 1334-36 1.2897 2.3695 DD/ Fe2+ 1.337 1.6240 EE/ siderite / 3+ -0.0322 0.2415 C1C1 Fe (Low spin) / 3+ 1384-86 0.3885 0.322 C2C2 Fe / 3+ 0.560 0.770 C3C3 Fe 0.5126 -.04912 α-Fe2O3 hematite / 3+ 1386-88 0.4054 0.2987 C1C1 Fe (Low spin) 1.0936 0.4161 NN/ Not identified 1.2430 2.4861 DD/ Fe2+ / 3+ 0.1522 0.8085 C1C1 Fe / 3+ 0.3815 0.2800 C2C2 Fe / 3+ 1426-28 0.6055 0.1330 C3C3 Fe 1.3352 1.5085 EE/ ankerite 1.0062 2.0335 DD/ Fe2+ 0.1697 0.4865 CC/ Fe 3+ (Low spin) 0.4655 0.8050 BB/ siderite 1450-52 1.2897 2.3695 DD/ Fe2+ 1.337 1.6240 EE/ ankerite -0.0455 0.476 CC/ Fe 3+ (Low spin) 1504-06 0.2345 1.2497 EE/ ankerite 0.6090 2.2225 BB/ siderite 1.2897 2.6530 DD/ Fe2+

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International Journal of Engineering, Management & Sciences (IJEMS) ISSN-2348 –3733, Volume-3, Issue-9, September 2016 Figure 1 : Room temperature Mössbauer spectra of sediment samples from well P#1. Depth at which the samples were collected are indicated.

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Figure 2 : Relative amount of iron in different minerals as a function of depth in well P#1

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International Journal of Engineering, Management & Sciences (IJEMS) ISSN-2348 –3733, Volume-3, Issue-9, September 2016

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