Quantitative assessment of the petroleum generation potential of early Cretaceous source rock in the northern part of Mari-Kandhkot High, north Sindh and southern Punjab, Pakistan
A source rock study and thorough petroleum system modelling have been performed as part of an exploration evaluation programme in one of the blocks in the northern part of the Mari-Kandhkot High (northern Sindh and southern Punjab) to determine the potential of Early Cretaceous sources and evaluate petroleum generated volumes in cubic feet gas per sq. km. The primary source rock in this region are the shales of the Early Cretaceous Sembar Formation (BerriasianValanginian, 145-132 Ma), while the Lower Goru Formation (Albian-Aptian, 125-113 Ma) shales can be considered the second most efficient source due to their high organic content.
Our study database involved 10 wells in the study area, where detailed source rock analyses were carried out on 106 samples in the Maluk -1, POGC Sabzal X-1, and Sara -1 wells, and the Total Organic Carbon (TOC) on seven additional wells was calculated through the Δlog R method. Study has determined, the mixed Type-II and Type-III kerogen, the TOC in the Sembar Formation ranges from 0.06% to 2.15%, with an average of 1.0%, and vitrinite reflectance (Ro) ranges from 0.7% to 1.95%. As a secondary source rock in the region, the Lower Goru Formation primarily contains Type-III organic matter, with TOC averaging 0.9% and Ro ranging from 0.80% to 1.45%. Depending on the quantity and quality of organic matter, oil generation depth ranges from 2200 to 2700 metres at temperatures between 100⁰ and 125⁰ C, whereas the minimum depth at which gas generation begins is 3000 metres at a temperature of approximately 125⁰C.
According to the results of the petroleum system modelling, the first hydrocarbon generation reached maturity at 53 Ma and peaked at 25 Ma, with a potential to generate 60–80 bcf/sq km of gas.
In our paper, we discussed the results of the organic geochemical analysis of the Lower Goru and Sembar formations from the Early Cretaceous, and we presented maps of the thickness of the organically rich layers, the distribution of thermally mature areas, and the intensity of hydrocarbon expulsion. These maps may offer future operators interested in exploring the area substantial data by supporting them understand the geological history of a source rock.
Ahmad, N., Fink, P., Sturrock, S., Mahmood, T., and Ibrahim, M., 2012, Sequence stratigraphy as predictive tool in Lower Goru Fairway, Lower and Middle Indus Platform, Pakistan. American Association of Petroleum Geologists Search and Discovery Article # 10404.
Andrew S. Pepper and Peter J. Corvit, 1995, Simple kinetic models of petroleum formation. Part I: Oil and Gas generation from kerogene, Marine and Petroleum Geology, Vol. 12, No. 3, pp. 291 – 319, 1995.
Andrew S. Pepper and Peter J. Corvit, 1995, Simple kinetic models of petroleum formation. Part III: Modeling an Open System, Marine and Petroleum Geology, Vol. 12, No. 4, pp. 417 – 452, 1995.
Andrew S. Pepper and Timothy A. Dodd, 1995, Simple kinetic models of petroleum formation. Part II: Oil-Gas cracking, Marine and Petroleum Geology, Vol. 12, No. 3, pp. 321 – 340, 1995.
Nazir et.al, 2011; Shale Gas Potential of Lower Cretaceous Sembar Formation in Middle and Lower Indus Basin, Pakistan.
Pakistan Journal of Hydrocarbon Research, Vol. 22 & 23, (June 2012 & 2013), p.51-62.
Pakistan Energy Year Book, 2018. Ministry of Energy (Petroleum Division), Hydrocarbon Development Institute of Pakistan.
Passey, Q. R., Creaney, S., Kulla, J. B., Moretti, F. J., and Stroud, J. D., 1990, A Practical Model for Organic Richness from Porosity and Resistivity Logs, AAPG Bulletin, 74, p. 1777-1794.
Qayyum, Faisal; Hanif, Muhammad; Mujtaba, Muhammad; Wahid, Sohail; and Ali, Fahad, 2016, Evaluation of source rocks using one dimensional maturity modeling in Lower Indus Basin, Pakistan: Arabian Journal of Geoscience, v. 9, no. 252, 22 p.
Quadri, V. N. and S.M. Shuaib, 1986; Hydrocarbon Prospect of Southern Indus Basin, Pakistan. AAPG V. 70, No. 6 (June 1986), P. 730-747.
Siddiqui, F.I.; Adhami, Asad; Asghar, Afnan; Hussain, Atif; and Khan, M.W.U., 2014, Shale gas potential of the Lower Goru Formation over the Lakhra High in Lower Indus Basin, Pakistan: American Association of Petroleum Geologists, Search and Discovery Article No. 80373, May 12, 2014, 28 p.