Geologia

Assignment

1. Describe three rock types that can be petroleum reservoirs, and for each rock type, describe the processes that can destroy and enhance reservoir quality.


Three rock typesthat can be petroleum reservoir are:

• Sandstone: Most important reservoir rock type. These rocks are the product of lithification of sand. The grain diameter varies from 1/16 to 2 mm. the mostcommon mineral in this rocks is the quartz.


• Limestone: Form organically and is composed of calcite. It is usual to find lots of fossils in it. There are two common types: Coquina and Chalk.• Dolomite: originate in the same way as limestone rocks but by the process of dolomitization the Calcium is changed by Magnesium

The types described are all sedimentary rocks and theprocesses that can affect the reservoir are:

• Dolomitization: Is the process to change Calcium by Magnesium. Improve reservoir quality because reduces the rock volume increasing the porosity ofthe rock.


• Lithification: Reduces reservoir quality because the sediment can be compacted or cemented obstructing the flow of fluids.

• Dissolution: Enhances the reservoir qualitybecause increases the pore space dissolving certain components of the rock.



2. Describe the characteristics required for a rock to be a source for petroleum and give an example.


A rock to bea source of petroleum needs to have the capacity to hold fluids and allow these fluids to move through them.


There are three main characteristics:
• Grain size: Larger size betterreservoir because fluids will flow easily.
• Sorting: Well-sorted sediment will hold larger volumes of fluids than Poorly-sorted sediment.
• Clay content: Clays impede fluids to flow through therock and it presence reduces the fluid volume.

The most important reservoir rock is the sandstone.

3. Describe the characteristics required for a rock to be a seal or cap rock and give an...