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Geology/Confusion !


Respected Sir
How are you? Honorable Sir I am student of geology and working in Mud logging. Sir few days ago we drilled a well in which we drilled the reservoir 3000 feet horizontally. Sir in this Zone we were getting the same Wackstone to packstone samples but the ROP and gasses were varrying on one moment it wents to 7% and some time 0.36% of gasses .. we were getting the variation of gasses with same ROP also. I need to ask that what are the factors on which the amount of gasses depend and can you answer that why it was happening in that well! ? thanks


As I understand you are drilling through a carbonate reservoir, which is fractured. The fracture development in a sedimentary rock is generally of oblique to vertical orientation, wherein a horizontal well has a chance to penetrate maximum number of fractures, either open or closed. Depending upon the petrophysical properties and varying brittleness of the carbonates, the concentration of fractures may vary. You may find cluster of fractures and then a poorly fractured zone, may be a solid rock mass, or a softer facies while drilling.

It is not necessary that all fractures may be connected in a virgin reservoir. The connected fractures may increase the gas shows and vice versa, while the ROP may not show significant change.

To me the reason for behavior of the well is because of the above.


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Nusrat Kamal Siddiqui (Mr)


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.


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

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.

-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.

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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