Organic geochemical evaluation of contamination tracers in deepwater well rock cuttings from the Mannar Basin, Sri Lanka

Ratnayake, Amila Sandaruwan; Sampei, Yoshikazu

doi:10.1007/s13202-018-0575-8

Cited by 19 publications

(4 citation statements)

References 30 publications

(43 reference statements)

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“…Manual stirring and ultrasonic vibration methods were used following the addition of dichloromethane and methanol (9:1 v/v) solvent mixture. Ratnayake and Sampei (2019) provide a detailed methodology for the cleaning of cutting samples.…”

Section: Methodsmentioning

confidence: 99%

Late Cretaceous to Miocene Paleoclimatic changes in the Indian Ocean: insights from the deepwater Mannar Basin, Sri Lanka

Ratnayake

2021

Geo-Mar Lett

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The geology of Sri Lanka captures one of the longest and most complete records of Jurassic to Miocene tectonic evolutions from the mid-latitudes of the southern hemisphere to the equatorial northern hemisphere. Sedimentary basins in Sri Lanka provide a natural laboratory with which to reconstruct paleoclimate during the island's northward voyage from Gondwana to Asia. Here, drill core cuttings were obtained from the Barracuda hydrocarbon exploration well in the offshore Mannar Basin, Sri Lanka. CHNS elemental analysis, gas chromatography-mass spectrometry, and stable C and N isotopic analyses were performed. The results suggest the deposition of organic carbon depleted (average total organic carbon (TOC) = 0.97%) sediments under the arid climate of the Early Campanian. Separation of the Laxmi Ridge-Seychelles and Seychelles from the Indian plate and sea-level regression may have enhanced the deposition of organic carbon-rich (average TOC = 1.34%) and terrestrial organic matter (OM)-rich (average C/N ratio = 20.36) sediments during the Late Campanian to Late Maastrichtian. CaCO 3 -rich (average = 32.5%) Upper Cretaceous sediments then show a period of high productivity under a warm climate. The Deccan-Reunion basalt likely acted as a major contributor to the mass extinction of coccolithophores/foraminifera at the Late Maastrichtian followed by a reduction of CaCO 3 and organic carbon content. The Early-Late Paleocene was characterized by the deposition of algal-derived OM with a terrestrial contribution (average C/N ratio = 15.75) under oxic depositional conditions (average C/S ratio = 16.21). However, the depositional environment changed drastically to one of oxygen-poor marine conditions (average C/S ratio = 6.83) during the Late Paleocene to the Early Oligocene due to weak oceanic circulation under a greenhouse climate. In contrast, the deposition of CaCO 3 -rich sediments since the Late Paleocene (average = 40.2%) is linked to the movement of the Indian plate into northern, warmer tropical latitudes. The Middle Oligocene to Miocene sedimentary succession was characterized by terrestrial OM-rich (average TOC = 2.51% and C/N = 23.45) sediments. The Middle-Upper Miocene sedimentary succession contains lamination and back carbon (charcoal fragments) suggesting the development of the present-day South Asian monsoon system. This record from Sri Lanka provides important new insights into Jurassic-Miocene geological and climatic evolution in this tropical part of the world for the first time.

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Section: Methodsmentioning

confidence: 99%

Late Cretaceous to Miocene Paleoclimatic changes in the Indian Ocean: insights from the deepwater Mannar Basin, Sri Lanka

Ratnayake

2021

Geo-Mar Lett

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“…The present study considered 20 representative calcareous argillaceous to arenaceous sediments from Late Cretaceous to Miocene. Samples were cleaned manually using 250 ml dichloromethane: methanol 9:1 v/v solution (Ratnayake and Sampei 2019). The cleaning efficiency was improved by washing samples twice with 50 ml aliquots of dichloromethane: methanol 9:1 solution.…”

Section: Sample Collection and Preparationmentioning

confidence: 99%

Qualitative mineralogical analysis of Barracuda exploration well in the offshore Mannar Basin (the Indian Ocean) using FTIR and XRD techniques

Gunathilake,

Jaywardana,

Ratnayake

et al. 2022

Ruhuna J. Sci.

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The Mannar Basin plays a vital role in petroleum exploration in Sri Lanka, and its Barracuda exploration well was drilled up to 4206 m in depth. The objective of the current study is to identify mineralogy using Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) analyses. The FTIR and XRD analyses confirm the presence of quartz, feldspar, clay minerals (e.g., kaolinite, montmorillonite), calcite, and hematite in all marlstone and mudstone samples. These sedimentary rocks can be identified as potential petroleum source rocks in the Mannar Basin. Quartz, carbonate, and hematite cementations are directly reduced porosity and permeability, and thus primary migration of hydrocarbons from potential source rocks. Clay minerals act as a seal for hydrocarbon migrations in the Mannar Basin. A variety of dominant clay mineral assemblages allows the reconstruction of several paleoclimatic chronozones in warm/wet and arid climates. In contrast, feldspar dissolution promotes the primary migration of hydrocarbon from potential petroleum source rocks. Consequently, this study concluded that common minerals such as quartz, carbonate, and hematite are associated with the trapping and binding processes of hydrocarbons.

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“…Previous studies have discussed the source rock potential in the Mannar Basin using geochemical results of drill-cuttings from Dorado, Dorado North, Wallago and Barracuda exploration wells and 1D basin modelling interpretations (e.g. Ratnayake et al 2018;Ratnayake and Sampei 2019). According to the literature, the Campanian-Maastrichtian, Albian and Late Jurassic source rocks can be considered as the best potential source rocks of the Mannar Basin.…”

Section: Source Rock Potentialmentioning

confidence: 99%

Play distribution and the hydrocarbon potential of the Mannar Basin, Sri Lanka

Kularathna

Pitawala

Senaratne

et al. 2020

J Petrol Explor Prod Technol

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The Mannar Basin is a frontier failed rift basin between India and Sri Lanka. The Sri Lankan part has an area exceeding 42,000 km2. Although the recent two gas discoveries have confirmed the existence of an active petroleum system in the Mannar Basin, a major portion of the basin is still poorly explored. This article summarized the progress of current exploration activities and the hydrocarbon potential of the Mannar Basin. This basin began to evolve since the Upper Jurassic and experienced two rifting events; an early Late Jurassic syn-rift phase associated with East–West Gondwana break up; and a later, earliest Cretaceous syn-rift phase associated with Antarctica separation from greater India around 142 Ma. Rifting was followed by a post-rift phase comprising a thermal sag period and an inversion period. Three potential source rocks intervals have been interpreted at Maastrichtian–Campanian, Albian–Aptian, and Late Jurassic stratigraphic levels. The basin modelling work has confirmed that (1) mature potential source rocks (mainly Type II) exist below the Maastrichtian–Campanian strata and (2) the best potential source rocks (mainly Type II) exist at Albian–Aptian stratigraphic levels. The Late Jurassic source rocks have more potential for gas, while other sources have potential for both oil and gas. According to basin modelling results, Maastrichtian–Campanian and Albian–Aptian source rocks reach the oil window in the present-day depocentre around 45 Ma and 80 Ma, respectively. The Late Jurassic source rocks (mainly Type III) reach the gas window around 112 Ma in the present-day depocentre. Five play levels were defined for the whole stratigraphic section of the Mannar Basin. Tertiary play level is dominated by submarine fans, mounds and rollover anticline like structures. The Upper Cretaceous play is dominated by forced-fold structures, intra-basalt turbidite sands, and sub-volcanic sand-rich systems. The Lower Cretaceous play is dominated by reefs and abrupt margin pinch outs. The Upper Jurassic play is dominated by abrupt margin pinch outs. The Basement play consists of weathered basement rocks. The main challenge of the Mannar Basin is imaging below the flood volcanic layer, which inhibits the penetration of seismic energy and results in low-quality seismic data. Therefore, hydrocarbon potential assessments have become a major challenge below the Upper Cretaceous. The interpretation shows that the basin has a low risk for the source and reservoir, and high risk for seal and traps. New exploration activity would unlock more potential areas for hydrocarbon accumulations. Finally, the findings of this study can help for better understanding of hydrocarbon potential areas and current progress of exploration activities in the Mannar Basin, Sri Lanka.

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Organic geochemical evaluation of contamination tracers in deepwater well rock cuttings from the Mannar Basin, Sri Lanka

Cited by 19 publications

References 30 publications

Late Cretaceous to Miocene Paleoclimatic changes in the Indian Ocean: insights from the deepwater Mannar Basin, Sri Lanka

Late Cretaceous to Miocene Paleoclimatic changes in the Indian Ocean: insights from the deepwater Mannar Basin, Sri Lanka

Qualitative mineralogical analysis of Barracuda exploration well in the offshore Mannar Basin (the Indian Ocean) using FTIR and XRD techniques

Play distribution and the hydrocarbon potential of the Mannar Basin, Sri Lanka

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