World Geothermal Congress 2020+1
March - October, 2021

Subsurface Radiogenic Heat Production Modeling in the Upper Indus Basin, Pakistan; A Geothermal Perspective of Sedimentary Basins

Mukhtiar GHANI, Irfan U. JAN, Sajjad AHMAD, Irfan U. HASHMI,

[Geological Survey Of Pakistan, Pakistan]

Heat production and thermal conductivity evaluation are important for assessing a sedimentary basin in terms of geothermal energy, petroleum source rock maturation, and mineral potential estimation. There are two main sources of earth’s subsurface temperature; internal heat engine represented in the form of geothermal gradient and the decay of radiogenic elements in subsurface formations. The geothermal gradient is usually very stable, but the radiogenic heat has a profound impact on the subsurface heating system. In this study, the radiogenic heat production (HP) is calculated in the Upper Indus Basin, using spectral gamma-ray (SGR) log data of thirty-three (33) exploratory wells. 1-D steady-state temperature model for each well is generated and juxtaposed over each other to represent 3-dimensionally throughout the basin targeting surface to 5000m depth. The data distribution categorized the Upper Indus Basin into six (6) different domains, i.e. the Punjab Plain, the eastern Potwar Basin, the central Potwar Basin, the western Potwar Basin, Karak and Kohat basins. Geostatistical analysis revealed that subsurface Heat Production (HP) ranges from 0-8 µW/m3 with an average value of 0.01-2.41 µW/m3. The eastern, western Potwar basins, and the Karak sub-basin showed higher values, while Punjab plain, Kohat sub-basin, and the central Potwar Basin showed lower (HP) values. The heat production (HP) values in Punjab Plain, eastern, central, and western Potwar Basin, Karak and Kohat sub-basin are 0.005-7.75, 0.005-5.25, 0.005-3.8, 0.03-3.7, 0.12-5.9, and 0.04-3.14 µW/m3 respectively with an average of 1.03, 0.72, 0.42, 0.71, 1.12 and 0.69 µW/m3 respectively. The Standard Deviation (σ) and Variance (σ2) ranged from 0.05-0.75 and 0-.52 respectively and showed higher values in Punjab Plain (0.505, 0.3254), western (i.e. 0.4777, 0.2755) and eastern Potwar Basin (i.e. 0.367,0.154). The data support a widespread heat production distribution in the subsurface of the Upper Indus Basin. The lower σ and σ2 values in Karak (i.e. 0.33, 0.24), Middle Potwar (i.e. 0.22, 0.06) and Kohat (i.e. 0. 22, 0.06) sub-basins demonstrated some data clustering representing a heat anomalous zones in the subsurface. Skewness and Kurtosis (K) ranged from 0.04-3.4 and 0-14 respectively, with higher values in eastern Potwar (i.e. 1.41, 4.2), Karak (i.e. 1.13, 4.46), western Potwar (i.e. 1.16, 1.09) and lower values in Central Potwar (i.e. 1.06, 1.6), Punjab Plain (i.e. 0.83,1.8) and Kohat (i.e. 0.56, 1.8) sub-basins. This illustrates that most of the data is skewed positively and higher Kurtosis shows some smooth distribution of data set while lower values of Kurtosis represent a clustering in data sets. The result suggests that radiogenic heat generation is too small (i.e. 8 µW/m3 maximum) and highly dispersed to have any significant effect on the geothermal parameters and source rock maturation. On the mineral prospecting side, there are few zones, which show some prospects of mineralization associated with radioactive elements.

        Topic: Resource Assessment Paper Number: 16017

         Session 8P: Poster 2 [Tuesday 11th May 2021, 11:00 pm] (UTC-8)
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