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Geology/porosities difference

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Question
AOA Sir,

Sir , Kindly tell me what are the differences between the porosities of fine grained and coarse grained clastic sedimentay rocks on the basis of grain size and why ?

Answer
Maham,

You may be aware that finer the grain size higher the porosity. That is the reason why shale has the highest porosity. Having said that, it is not just the porosity but the ability of the rock to allow the fluids to flow, which is described as the permeability. And coarser the grain size higher the permeability will be, depending on how well-sorted are the grains. The porosity when gets connected through fractures or the linear micro-openings the pores get connected and the liquids move upwards towards a trap.

So, the main difference is that fine-grained clastics have relatively higher porosity and lower permeability, while the coarse-grained clastics have relatively lower porosity and higher permeability.

Hope it answers your query.

Geology

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Nusrat Kamal Siddiqui (Mr)

Expertise

I am a petroleum exploration geologist with about 40+ years of diversified experience. I can answer questions on stratigraphy, log interpretation, field studies based on set of logs and core results, general geology etc. Can provide guidance for career planning in earth sciences. Can not help in questions about hard rocks, igneous petrology & mineralogy, sequence stratigraphy and seismic.

Experience

Petroleum Exploration - field geology, stratigraphy, prospect generation, interpretation of satellite imagery (visual), log interpretation.

Organizations
Retired in May, 2006 as Senior Manager Exploration from Pakistan Petroleum Limited after serving 26 years. Since then continuing in active service with petroleum exploration companies.A cumulative experience of about 40 years covers 30 years in petroleum exploration, 5 years hydrogeology experience in Libya, and about 5 years of dam geology in Pakistan.

Publications
-AAPG Bulletin (Vol.88, July, 2004); paper on Sui Main Limestone (Eocene), a prolific gas reservoir in Pakistan. -Have presented papers on diversified topics ranging from spirituality, flood control, remote sensing and off course geology in France, Nepal, Bangladesh, Sri Lanka, UAE, Kashmir, India and Pakistan that have been published in respective Special Proceedings. -ONGC Bulletin(India) Vol. 44, Number 2, December, 2009; Chapter 19.A & 19.B on basin architecture and stratigraphy of Pakistan, p.402-474.

Education/Credentials
BSc Honours in Geology and Master of Science in Petroleum and Structural Geology. PGD from ITC, The Netherlands.

Awards and Honors
-Remained Active Member of AAPG from 1990-2006; founding member of PAPG (a local affiliate of AAPG). -Life member of SEGMITE & AGID, and Senior Editor of SEGMITE magazine. -Member of the Board of Studies, i. Department of Petroleum & Gas Engineering (BUITMS, Quetta), and ii. Geology Department, Sindh University, Jamshoro. -Member of Stratigraphic Committee of Pakistan. -Represented Mining Journal, UK in Pakistan till 2007. -Chairman of Annual Technical Conference (ATC)& Oil Show, an SPE/PAPG annual event, in 2003. -Chairman Technical Committee (ATC, 2002).

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