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SUMMARY:Borehole stratigraphy\, organic geochemistry and petrography of Pe
 rmo-Carboniferous Lower Ecca black shales: Implications for their shale ga
 s potential
DTSTART;VALUE=DATE-TIME:20141001T074000Z
DTEND;VALUE=DATE-TIME:20141001T075500Z
DTSTAMP;VALUE=DATE-TIME:20261006T162026Z
UID:indico-contribution-4006@events.saip.org.za
DESCRIPTION:Speakers: Naledi Chere (AEON - NMMU)\nIn the Main Karoo Basin\
 , Permo-Carboniferous black shales of the Lower Ecca Group\, especially th
 e Prince Albert and Whitehill Formations\, are considered to be a potentia
 l source of shale gas. Core samples of shale were collected from eight bor
 eholes predominantly drilled in the 1960’s\, and stored at the Council f
 or Geosciences’ core library in Pretoria. The carbonaceous black shale o
 f the Whitehill Formation attains a maximum thickness of 60m in the wester
 n portion basin\, whereas an average thickness of approximately 33m is rec
 orded in the south western region of the basin. Due to the occurrence of s
 uch thick successions of black shales\, the Karoo Basin is one of the targ
 eted regions for shale gas exploration. \nThe samples were analysed for th
 eir gas potential\, using standard shale gas exploration parameters\, whic
 h entails detailed source rock characterization. This has been accomplishe
 d mainly through organic petrology and organic geochemistry. Organic petro
 graphy included techniques such as optical microscopy and electron microsc
 opy (i.e. SEM\, FIB-SEM). These are important in identifying compositional
  and textural variability within the rock. Complementary geochemical analy
 sis such as Rock Eval and GC MS were crucial in determining factors like f
 raction of gas present as adsorbed gas\, organic matter type and TOC conte
 nt. \nThe mineralogical composition\, as observed through thin section mic
 roscopy\, is dominated by quartz\, feldspars\, clays and carbonates. Moreo
 ver\, the shale samples were shown to predominantly consist of alternating
  layers of silt-enriched and mud-enriched horizons through thin section st
 udies. Investigations with the XRF technique showed SiO2 to be the dominan
 t major element component. In addition\, XRD analyses reveal quartz to be 
 the dominant mineral phase in most of the samples. SEM further confirms th
 e dominance of quartz and clay minerals (illite). The enrichment in quartz
  indicates high brittleness of the shale which is crucial for controlled h
 ydraulic fracking and successful extraction of potentially tight gas. SEM 
 was used to further identify minerals that appear opaque under the optical
  microscope (e.g. pyrite) as well as to identify organic matter. FIB-SEM w
 as utilized to study rock specimen at a nanometer scale\, enabling the ide
 ntification of organic matter\, porosity within the organic matter as well
  as intragranular porosity. \nTotal organic carbon (TOC) content must be g
 reater than 0.5 wt % for the rock to be a potential source rock. The Karoo
  shale samples reach a maximum of 7.3 wt% TOC in the south western region 
 of the basin. The samples from borehole KI1/65 record the highest TOC valu
 es and adsorbed methane content\, as detected by thermovap-GC\, with up to
  10.2 µg/g CH4. Open pyrolysis analysis show the organic matter from samp
 les of well LA 1/68 to be of Type III type kerogen\, the QU 1/65 to be Typ
 e I/II and the samples of KI 1/65 to consists organic matter of both Type 
 I/II and Type III. The combination of the results from these geochemical t
 echniques and the understanding of the evolution of the Karoo basin (i.e. 
 thickness variation\, thermal history\, variation in depositional environm
 ents) have been used to characterize the shales from the Main Karoo Basin 
 for their gas potential.\n\nhttps://events.saip.org.za/event/40/contributi
 ons/4006/
LOCATION:Matjiesfontein's Lord Milner Hotel Conference Room\, Matjiesfonte
 in Station
URL:https://events.saip.org.za/event/40/contributions/4006/
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