Oil exploration Petroleum geologists need to know the geological structures and

Question

Oil exploration

Petroleum geologists need to know the geological structures and formations that are most likely to yield oil and gas. Most of the data that they use comes from wells, which give an indication of rock types present below the surface, and from seismic sections, that give an indicator of sub-surface structure. These data can be combined to produce geological sections, which are used to assess the probability of the presence of gas and oil fields.

1. Interpret the geological shown in figure two by indicating:   

The source rock

The reservoir rock

An oil trap

The best location for an oil well (show well extending into subsurface)

Figure two: geological section as a potential oil source

2. The fold axis of an anticline can form a good oil trap. Explain how you would recognize an anticline in outcrop on the ground surface.

Explanation / Answer

1. a.The source rock for petroleum generation is the marine shale which lies at the bottom of the succession in the given figure. As the shale is rich in organic material, so it acts as a good source rock.

b. A reservoir rock is a porous or fractured zone which contains the hydrocarbon. The reservoir rock must be the sandstone which has good porosity and permeability, so helps in primary and secondary migration of petroleum.

c. Oil trap is the acumulation of hydrocarbon. Here the oil trap is the structural trap specifically the compressional anticline formed by the rock gropus.

d. The best location for an oil well is the vertical from the surface into subsurface cutting across the fault plane and upto the reservoir formation.

2. An anticline can be recognized by observing the younger direction of rock groups. The older rocks lie at the core of an anticline and the young rocks lie away from the core indicates the younging direction is away from the core of the fold.

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