Introduction to Petroleum Geoscience

Introduction to Petroleum Geoscience
An Overview

Petroleum geology refers to the specific set of geological disciplines that are applied to the search for hydrocarbons during oil exploration. Petroleum geology is principally concerned with the evaluation of seven key elements in a sedimentary basin to obtain an idea of the subsurface and overall petroleum system.
  * Source
  * Reservoir
  * Seal
  * Trap
  * Timing
  * Maturation and
  * Migration
We shall now consider these seven sources in a step by step manner.
  1. Evaluation of the Source
This involves quantification and evaluation of the nature of organic-rich rocks so that the type
analysis.  
Steps in Source Rock Analysis
  * First establish likelihood of presence of organic-rich sediments deposited in the past on the basis of studies of local stratigraphy, paleogeography and sedimentology of the area.
  * Identification and delineation of area of potential source rock.
  * Determine the type of KEROGEN and state of its maturation.
  * Calculation of thermal maturity and timing of maturation.  
  * Finally determine the likelihood of oil / gas generation in the area and calculate the depth of oil window.
(Majority of oil generation occurs in the 60° to 120°C range. Gas generation starts at similar temperatures, but may continue up beyond this range, perhaps as high as 200°C.)
Geochemical Log

  2. The Reservoir
It is a porous and permeable lithological unit or set of units that holds the hydrocarbon reserves. The common types include sandstone and limestone.  
Steps in Analysis of Reservoirs
  * First determine the type of lithofacies of the reservoir.
  * Assessment of their porosity (to calculate the volume of in situ hydrocarbons) and permeability (to calculate how easily hydrocarbons will flow out of them).
  * Study the Post depositional Diagenetic changes in reservoir.
  * Establish depositional environment and geometry of the reservoirs.
Some...