Question

Petroleum Engineering:
How can the knowledge of grain size distribution aid in the evaluation of a petroleum reservoir?

Answer 1

Grain size distribution tells us the about the pore sizes and pore throat size. So, basically it tells us about porosity( pore size) and and permeability (pore throat size). Suppose all the grains are well sorted, pore sizes will be homogeneous and porosity will be high. This will be due to higher number of pores. {Porosity= (Pore volume/bulk volume)}. Permeability will also be high in this case as pore connectivity will be high. Now, if the grain size distribution is not well sorted, there will be smaller padticles in the intergranular space reducing the pore size, thus reducing the porosity and permeability. These two are the two extremes and the general grain size distribution gives us idea about the reservoir porosity and permebility.