AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain
Mississippi Valley Type (MVT) Mineralization in the Khuff C Reservoirs, Saudi Arabia
(1) Saudi Aramco, Dhahran, Saudi Arabia.
Mississippi Valley Type (MVT) mineralization emplaced pyrite, sphalerite, galena, and gangue minerals, such as saddle (baroque) dolomite into the C carbonate of the Khuff Formation, of Upper Permian age. In most cases small percentages of MVT mineralization had been identified in several Khuff reservoirs, both onshore and offshore. In one particular case MVT mineralization was represented by complete replacement of carbonate beds and consisted of multiple, thick layers of mineral deposits that contained moldic porosity. X-ray diffractometry confirmed the presence of pyrite, sphalerite, and galena.
In all cases, when MVT mineralization was identified it was located within the Khuff C carbonate immediately above the Khuff D evaporite. Major faults are thought to have delivered iron, zinc, and lead-rich fluids up-section from the basement or red beds that overlie the basement. Metal-rich fluids are considered to have derived sulfur by dissolution of the Khuff D evaporite and precipitated MVT minerals above the evaporite. This process essentially created a mixing zone to mix metals with sulfur as fluids moved up the fault zone in pulses, “squirt up a fault,” during Late Mesozoic and/or Tertiary deformation.