Changes

The stratigraphy of the Barmer Basin is relatively simple as illustrated in [[:file:M114CH03FG04.jpg|Figure 4]] (modified and updated from Dolson et al., 2015<ref name=Dolsonetal2015 />) and represents alternating cycles of deposition from [[fluvial]] and coaly swamps to deep water lakes into which fan [[delta]]s shed organic matter-rich debris flows and [[turbidite]]s. Very minor marine influence at times of sea level [[highstand]] is indicated by the presence of short-lived communities of marine [[foraminifera]] ([[Nummulites]]), [[dinocysts]], and [[ostracods]] (Sahni and Choudhary, 1972<ref name=Sahniandchoudhary1972>Sahni, A., and N. K. Choudhary, 1972, Lower Eocene fishes from Barmer, Southwestern Rajasthan, India: Proceedings of the Indian National Science Academy, v. 38, p. 97–102.</ref>; Tripathi et al., 2009<ref name=Tripathietal2009>Tripathi, S. K. M., M. Kumar, and D. Srivastava, 2009, Palynology of Lower Paleogene (Thanetian-Ypresian) coastal deposits from the Barmer Basin (Akli Formation), Western Rajasthan, India: Palaeoenvironmental and palaeoclimatic implications: Geologica Acta, v. 7, p. 147–160.</ref>). The [[sediment]]ary sequence is dominantly [[Paleocene]] to [[Eocene]] in age and the basin fill overlies [[basement]] rocks of the [[Precambrian]] [[Malani Igneous Suite]] as well as [[prerift]] sediments of the [[Mesozoic]] [[fluvial]] [[Lathi formation|Lathi]] and [[Ghaggar-Hakra formation]]s (Compton, 2009<ref name=Compton2009 />; Beaumont et al., 2015<ref name=Beaumontetal2015>Beaumont, H., S. M. Clarke, S. D. Burley, A. Taylor, T. Gould, and P. Mohapatra, 2015, Deciphering tectonic controls on fluvial sedimentation within the Barmer Basin, India: The Lower Cretaceous Ghaggar-Hakra Formation: [http://www.searchanddiscovery.com/pdfz/documents/2015/51100beaumont/ndx_beaumont.pdf.html AAPG Search and Discovery Article #51100], accessed November 9, 2016.</ref>; Bladon et al., 2015b<ref name=Bladonetal2015b />). The [[Jurassic]] Lathi and [[Cretaceous]] Ghaggar-Hakra formations are sand-dominated, prerift reservoirs that are well exposed around the margins of the basin and occur along the northern uplifted outcrop limit. The Ghaggar-Hakra Formation is also encountered in wells in the main fields where they host significant [[hydrocarbon]] reserves. These sand-dominated sequences, together with the [[synrift]] [[Fatehgarh Formation]], are extensive sheet-like [[alluvial]] [[deposit]]s that form well-connected carrier beds and [[reservoirs]] ([[:file:M114CH03FG04.jpg|Figure 4]]). Lake margin fan [[delta]]s and deep water [[turbidite]] systems enclosed in the [[Barmer Hill Formation]] are more restricted in their extent and less well connected, but were deposited adjacent to [[source rock]]s and so are easily charged. Although there are multiple, thick, [[shale]] sequences within the [[Cenozoic]] basin fill that form regional [[seal]]s, the most significant are those of the [[Sarovar Member]] of the Barmer Hill Formation, the [[Mandai Member]] of the [[Dharvi Dungar Formation]], and the [[Juni Bali Member]] of the [[Akli Formation]] ([[:file:M114CH03FG04.jpg|Figure 4]]). All potential source rocks younger than the Dharvi Dungar Formation are thermally immature everywhere in the basin. The shallowest oil reservoirs are, however, younger than these source rocks and are encountered in the [[Thumbli Formation]]. These reservoirs require significant fault-assisted vertical migration to receive hydrocarbon charge. There are no accumulations above the Thumbli Formation anywhere in the basin, indicating that the overlying late [[Eocene]] Akli Formation is the topmost regional seal to the petroleum system across the basin that is only breached by a few deep-seated faults, many of which extend to the surface. A major depositional hiatus of late [[Oligocene]] to early [[Miocene]] age and subsequent [[tilt]]ing and [[uplift]] of the northern part of the basin in the Miocene completes the basin history.

The stratigraphy of the Barmer Basin is relatively simple as illustrated in [[:file:M114CH03FG04.jpg|Figure 4]] (modified and updated from Dolson et al., 2015<ref name=Dolsonetal2015 />) and represents alternating cycles of deposition from [[fluvial]] and coaly swamps to deep water lakes into which fan [[delta]]s shed organic matter-rich debris flows and [[turbidite]]s. Very minor marine influence at times of sea level [[highstand]] is indicated by the presence of short-lived communities of marine [[foraminifera]] ([[Nummulites]]), [[dinocysts]], and [[ostracods]] (Sahni and Choudhary, 1972<ref name=Sahniandchoudhary1972>Sahni, A., and N. K. Choudhary, 1972, Lower Eocene fishes from Barmer, Southwestern Rajasthan, India: Proceedings of the Indian National Science Academy, v. 38, p. 97–102.</ref>; Tripathi et al., 2009<ref name=Tripathietal2009>Tripathi, S. K. M., M. Kumar, and D. Srivastava, 2009, Palynology of Lower Paleogene (Thanetian-Ypresian) coastal deposits from the Barmer Basin (Akli Formation), Western Rajasthan, India: Palaeoenvironmental and palaeoclimatic implications: Geologica Acta, v. 7, p. 147–160.</ref>). The [[sediment]]ary sequence is dominantly [[Paleocene]] to [[Eocene]] in age and the basin fill overlies [[basement]] rocks of the [[Precambrian]] [[Malani Igneous Suite]] as well as [[prerift]] sediments of the [[Mesozoic]] [[fluvial]] [[Lathi formation|Lathi]] and [[Ghaggar-Hakra formation]]s (Compton, 2009<ref name=Compton2009 />; Beaumont et al., 2015<ref name=Beaumontetal2015>Beaumont, H., S. M. Clarke, S. D. Burley, A. Taylor, T. Gould, and P. Mohapatra, 2015, Deciphering tectonic controls on fluvial sedimentation within the Barmer Basin, India: The Lower Cretaceous Ghaggar-Hakra Formation: [http://www.searchanddiscovery.com/pdfz/documents/2015/51100beaumont/ndx_beaumont.pdf.html AAPG Search and Discovery Article #51100], accessed November 9, 2016.</ref>; Bladon et al., 2015b<ref name=Bladonetal2015b />). The [[Jurassic]] Lathi and [[Cretaceous]] Ghaggar-Hakra formations are sand-dominated, prerift reservoirs that are well exposed around the margins of the basin and occur along the northern uplifted outcrop limit. The Ghaggar-Hakra Formation is also encountered in wells in the main fields where they host significant [[hydrocarbon]] reserves. These sand-dominated sequences, together with the [[synrift]] [[Fatehgarh Formation]], are extensive sheet-like [[alluvial]] [[deposit]]s that form well-connected carrier beds and [[reservoirs]] ([[:file:M114CH03FG04.jpg|Figure 4]]). Lake margin fan [[delta]]s and deep water [[turbidite]] systems enclosed in the [[Barmer Hill Formation]] are more restricted in their extent and less well connected, but were deposited adjacent to [[source rock]]s and so are easily charged. Although there are multiple, thick, [[shale]] sequences within the [[Cenozoic]] basin fill that form regional [[seal]]s, the most significant are those of the [[Sarovar Member]] of the Barmer Hill Formation, the [[Mandai Member]] of the [[Dharvi Dungar Formation]], and the [[Juni Bali Member]] of the [[Akli Formation]] ([[:file:M114CH03FG04.jpg|Figure 4]]). All potential source rocks younger than the Dharvi Dungar Formation are thermally immature everywhere in the basin. The shallowest oil reservoirs are, however, younger than these source rocks and are encountered in the [[Thumbli Formation]]. These reservoirs require significant fault-assisted vertical migration to receive hydrocarbon charge. There are no accumulations above the Thumbli Formation anywhere in the basin, indicating that the overlying late [[Eocene]] Akli Formation is the topmost regional seal to the petroleum system across the basin that is only breached by a few deep-seated faults, many of which extend to the surface. A major depositional hiatus of late [[Oligocene]] to early [[Miocene]] age and subsequent [[tilt]]ing and [[uplift]] of the northern part of the basin in the Miocene completes the basin history.

[[file:M114CH03FG05.jpg|300px|thumb|{{figure number|5}}Paleogeographic maps of the (A) main carrier horizon, lowermost [[Fatehgarh Formation]], (B) main [[source rock]] unit, the [[Sarovar Member]] of the [[Barmer Hill Formation]], and (C) [[Giral Member]] of the [[Dharvi Dungar Formation]]. Dotted line indicates the approximate location of the deep-seated structural [[hinge]] that separates the inverted northern and deeply buried southern provinces.

[[file:M114CH03FG05.jpg|300px|thumb|{{figure number|5}}Paleogeographic maps of the (A) main carrier horizon, lowermost [[Fatehgarh Formation]], (B) main [[source rock]] unit, the [[Sarovar Member]] of the [[Barmer Hill Formation]], and (C) [[Giral Member]] of the [[Dharvi Dungar Formation]]. Dotted line indicates the approximate location of the deep-seated structural [[hinge]] that separates the inverted northern and deeply buried southern provinces.]]

Paleogeographic maps of the most important [[reservoir]]s and [[source rock]]s are shown in [[:file:M114CH03FG05.jpg|Figure 5]]). The most prolific reservoir is the late [[Cretaceous]] to early [[Paleocene]] [[synrift]] [[Fatehgarh Formation]]. The Fatehgarh Formation forms thick, sheet-like [[fluvial]] [[reservoir]]s that are best developed in the northern part of the basin (see [[:file:M114CH03FG05.jpg|Figure 5A]]). Fatehgarh Formation fluvial facies inter-digitate with basin margin [[alluvial]] [[fan]]s of the [[Jogmaya Mandir Formation]] in the north and the [[Dhandlawas Formation]] in the center and south of the basin, where they are composed of lower-quality [[volcaniclastic]] sands particularly well developed around the Central Basin High. These Fatehgarh Formation reservoirs are directly overlain by the main source rock in the basin, the [[lacustrine]] [[shales]] of the [[Sarovar Member]] of the [[Barmer Hill Formation]] ([[:file:M114CH03FG05.jpg|Figure 5B]]). [[Migration]] from these source rocks into the Fatehgarh Formation reservoirs is therefore either downward or across [[fault]] juxtapositions and highly efficient. The fan [[delta]] and lacustrine [[turbidite]] sands of the Barmer Hill Formation are easily charged with [[hydrocarbon]]s as they interdigitate with and are enclosed within the source rock. The Barmer Hill Formation also contains widespread [[diatomite]] deposits of the [[Bariyada Member]] (see [[:file:M114CH03FG05.jpg|Figure 4]]) that are intimately interbedded with the source rocks, forming a significant, laterally extensive but low permeability reservoir (Chowdhury et al., 2011<ref name=Chowdhuryetal2011>Chowdhury, M., M. Singhal, V. Sunder, T. O’Sullivan, P. A. Hansen, and S. D. Burley, 2011, Reservoir characterization of the low permeability siliceous Barmer Hill Formation, Barmer Basin, India: Society of Petroleum Engineers, v. SPE-146474-PP, p. 11–18.</ref>).

Paleogeographic maps of the most important [[reservoir]]s and [[source rock]]s are shown in [[:file:M114CH03FG05.jpg|Figure 5]]). The most prolific reservoir is the late [[Cretaceous]] to early [[Paleocene]] [[synrift]] [[Fatehgarh Formation]]. The Fatehgarh Formation forms thick, sheet-like [[fluvial]] [[reservoir]]s that are best developed in the northern part of the basin (see [[:file:M114CH03FG05.jpg|Figure 5A]]). Fatehgarh Formation fluvial facies inter-digitate with basin margin [[alluvial]] [[fan]]s of the [[Jogmaya Mandir Formation]] in the north and the [[Dhandlawas Formation]] in the center and south of the basin, where they are composed of lower-quality [[volcaniclastic]] sands particularly well developed around the Central Basin High. These Fatehgarh Formation reservoirs are directly overlain by the main source rock in the basin, the [[lacustrine]] [[shales]] of the [[Sarovar Member]] of the [[Barmer Hill Formation]] ([[:file:M114CH03FG05.jpg|Figure 5B]]). [[Migration]] from these source rocks into the Fatehgarh Formation reservoirs is therefore either downward or across [[fault]] juxtapositions and highly efficient. The fan [[delta]] and lacustrine [[turbidite]] sands of the Barmer Hill Formation are easily charged with [[hydrocarbon]]s as they interdigitate with and are enclosed within the source rock. The Barmer Hill Formation also contains widespread [[diatomite]] deposits of the [[Bariyada Member]] (see [[:file:M114CH03FG05.jpg|Figure 4]]) that are intimately interbedded with the source rocks, forming a significant, laterally extensive but low permeability reservoir (Chowdhury et al., 2011<ref name=Chowdhuryetal2011>Chowdhury, M., M. Singhal, V. Sunder, T. O’Sullivan, P. A. Hansen, and S. D. Burley, 2011, Reservoir characterization of the low permeability siliceous Barmer Hill Formation, Barmer Basin, India: Society of Petroleum Engineers, v. SPE-146474-PP, p. 11–18.</ref>).