GEOLOGY OF KAROO SHALE GAS AND HOW THIS CAN INFLUENCE ECONOMIC GAS RECOVERY DR. DOUG COLE by
LAYOUT OF PRESENTATION
ONLY THE LOWER ECCA GROUP SHALES ARE SUFFICIENTLY
CARBONACEOUS TO HAVE A GAS-BEARING POTENTIAL
OVER-MATURITY DUE TO DEEP BURIAL AND THE CAPE OROGENY
DESTRUCTION OF GAS POTENTIAL DUE TO DOLERITE INTRUSION
DEPTH RESTRICTION OF 1500 METRES FOR SHALE TARGETS
GEOLOGY OF KAROO GAS-BEARING SHALES AND THEPARAMETERS INFLUENCING ECONOMIC GAS RECOVERY
HYDROCARBON GENERATION THERMAL MATURATION INDICES ANDMATURATION STAGES PLOTTED AGAINST DEPTH OF BURIAL. (From Tissot and Welte, 1984).
ASSESSMENT OF SHALE GAS POTENTIAL OF ECCA GROUP FORMATIONS
TOTAL ORGANIC CARBON: 3 TO 12 %
Marcellus Shale 0.3 – 20 % Whitehill Formation 0.5 – 14.7 %Barnett Shale 0.5 – 13 % Prince Albert Formation 0.35 – 12.4 %
Pietermaritzburg Fm 0.3 – 11.6 %Tierberg Formation 0.3 – 5.2 %Volksrust Formation 0.3 – 5.9 %
THICKNESS: > 10 metres
Marcellus Shale 12 – 270 m Whitehill Formation 0.4 – 72 mBarnett Shale 15 – 300 m Prince Albert Formation 30 – 500 m
Pietermaritzburg Fm 0.8 – 420 mTierberg Formation 400 – 1300 mVolksrust Formation 250 – 415 m
DISTRIBUTION IN TIME AND SPACE OF PENNSYLVANIAN TO LATEST PERMIANSTRATIGRAPHIC UNITS INCLUDING LITHOLOGY AND ENVIRONMENT IN THE KAROO BASIN
(Chronostratigraphic scale from International Commission on Stratigraphy, 2013)
HYDROCARBON POTENTIAL OF ECCA GROUP SHALES IN THE MAIN KAROO BASIN (From Rowsell and De Swardt, 1976)
WHITEHILL FORMATION IN ARID SOUTHWESTERN PART OF THE KAROO BASIN
White weathering due to gypsum, which formed as a result of aerobic bacteria oxidising pyrite to sulphate with the metabolic waste, sulphuric acid, dissolving calcium carbonate followed by the precipitation of gypsum.
Karoo breccia pipes located on hill. They were probably vents for the escape of methane to the atmosphere during dolerite sill intrusion at 183 Ma (Aarnes et al., 2011).
The pipe contains brecciated host rock, which can be molten and recrystallised in places.