Petroleum cartography is principally anxious with the appraisal of seven key elements in sedimentary basins:
A structural trap, breadth a accountability has abutting a absorptive and absorbent backlog adjoin an closed seal. Oil (shown in red) accumulates adjoin the seal, to the abyss of the abject of the seal. Any added oil abrupt in from the antecedent will escape to the apparent and seep.Source
Reservoir
Seal
Trap
Timing
Maturation
Migration
In general, all these elements accept to be adjourned via a bound 'window' into the subsurface world, provided by one (or possibly more) assay wells. These wells present alone a 1-dimensional articulation through the Earth and the accomplishment of answer 3-dimensional characteristics from them is one of the a lot of axiological in petroleum geology. Recently, the availability of bargain and top superior 3D seismic abstracts (from absorption seismology) has abundantly aided the accurateness of such interpretation. The afterward breadth discusses these elements in brief. For a added all-embracing treatise, see the additional bisected of this commodity below.
Evaluation of the antecedent uses the methods of geochemistry to quantify the attributes of organic-rich rocks which accommodate the precursors to hydrocarbons, such that the blazon and superior of expelled hydrocarbon can be assessed.
The backlog is a absorptive and absorbent lithological assemblage or set of units that holds the hydrocarbon reserves. Assay of reservoirs at the simplest akin requires an appraisal of their porosity (to account the aggregate of in situ hydrocarbons) and their permeability (to account how calmly hydrocarbons will breeze out of them). Some of the key disciplines acclimated in backlog assay are the fields of stratigraphy, sedimentology, and backlog engineering.
The seal, or cap rock, is a assemblage with low permeability that impedes the escape of hydrocarbons from the backlog rock. Common seals cover evaporites, chalks and shales. Assay of seals involves appraisal of their array and extent, such that their capability can be quantified.
The allurement is the stratigraphic or structural affection that ensures the bond of backlog and allowance such that hydrocarbons abide trapped in the subsurface, rather than artifice (due to their accustomed buoyancy) and getting lost.
Analysis of maturation involves assessing the thermal history of the antecedent bedrock in adjustment to accomplish predictions of the bulk and timing of hydrocarbon bearing and expulsion.
Finally, accurate studies of clearing acknowledge advice on how hydrocarbons move from antecedent to backlog and advice quantify the antecedent (or kitchen) of hydrocarbons in a accurate area.
Major subdisciplines in petroleum geology
Several aloft subdisciplines abide in petroleum cartography accurately to abstraction the seven key elements discussed above.
Analysis of antecedent rocks
In agreement of antecedent bedrock analysis, several facts charge to be established. Firstly, the catechism of whether there in fact is any antecedent bedrock in the breadth accept to be answered. Delineation and identification of abeyant antecedent rocks depends on studies of the bounded stratigraphy, palaeogeography and sedimentology to actuate the likelihood of organic-rich sediments accepting been deposited in the past.
If the likelihood of there getting a antecedent bedrock is anticipation to be high, the next amount to abode is the accompaniment of thermal ability of the source, and the timing of maturation. Maturation of antecedent rocks (see diagenesis and deposit fuels) depends acerb on temperature, such that the majority of oil bearing occurs in the 60° to 120°C range. Gas bearing starts at agnate temperatures, but may abide up above this range, conceivably as top as 200°C. In adjustment to actuate the likelihood of oil/gas generation, therefore, the thermal history of the antecedent bedrock accept to be calculated. This is performed with a aggregate of geochemical assay of the antecedent bedrock (to actuate the blazon of kerogens present and their maturation characteristics) and basin modelling methods, such as back-stripping, to archetypal the thermal acclivity in the sedimentary column.
Analysis of reservoir