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Plate Collision and the Earth Quakes

Plate Collision and the Earth Quakes

The collision between the Eurasian and Indian plates is one of the most significant geological events shaping our planet’s landscape. This monumental collision, offers profound insights into the shape, size, and dynamics of tectonic plates. Understanding how India slides beneath Eurasia, the formation of critical faults, and the resulting seismic activity provides a window into the intricate processes that shape our mountains and drive earthquakes.

The Mechanics of Plate Collision

Approximately 50 million years ago, the Indian plate began its northward journey towards the Eurasian plate at a rapid pace of several centimeters per year. The convergence of these two massive plates led to the subduction of the Indian plate beneath the Eurasian plate. This subduction process involves the Indian plate being thrust underneath Eurasia, causing the overlying sediments to scrape off and accumulate, forming a wedge-shaped zone of deformed material known as an accretionary wedge.

Fault Systems and Shortening Accommodation

The Indian-Eurasian collision is characterized by a series of major thrust faults that accommodate the shortening of the Earth’s crust. Among these, the Main Frontal Thrust (MFT) is particularly significant. The MFT accommodates most of the shortening between the colliding plates, with a rate of approximately 21 mm/year. This significant rate indicates that the MFT is responsible for nearly all the crustal shortening in the region.

One might wonder why the MFT accommodates such a large portion of the shortening. The answer lies in its geological position and mechanics. The MFT, located at the southern edge of the Himalayan range, is a youngest and relatively shallow fault that can slip more easily compared to deeper, more northerly faults. This ease of slip allows the MFT to bear the brunt of the compressional forces generated by the collision.

Sequential Fault Formation and Earthquakes

Plate Collision and the Earth Quakes

As the Indian plate continues to push northward, the increasing overburden pressure results in the sequential formation of additional thrust faults. Starting with the Tibetan Detachment, which houses the earliest sediments from the collision, subsequent faults form progressively to the south: The Main Karakoram Thrust (MKT), Main Mantle Thrust (MMT), the Main Boundary Thrust (MBT), and finally the Main Frontal Thrust (MFT) (Figure-01). These faults develop in a sequence as the accumulating stress and pressure exceed the structural limits of each preceding fault.

Out-of-Sequence Thrusting and Northern Faults

Sequential Fault Formation and Earthquakes

Figure 2 The MFT accommodates shortening with a rate of approximately 21 mm/year. Figure courtesy: Will Amidon

Despite the dominance of the MFT in accommodating shortening, the northern faults, such as the MCT and MBT, also play a crucial role. These faults sometimes experience out-of-sequence thrusting, a phenomenon where faults not typically active in the current tectonic regime are reactivated. This reactivation can occur due to changes in the stress regime, often influenced by erosion (Figure-02).

Erosion plays a critical role in altering the stress dynamics of faults. In the Himalayas, significant erosion has removed vast amounts of sediment, which reduces the overlying pressure (normal stress) on the faults. When normal stress decreases, the shear stress—responsible for fault movement—can exceed it, leading to the reactivation of these northern faults and triggering earthquakes.

Plate Collision and the Earth Quakesq

Figure 3 When normal stress decreases, the shear stress—responsible for fault movement—can exceed it. Figure courtesy: Will Amidon


The collision between the Eurasian and Indian plates is a dynamic and complex process, driven by the interplay of tectonic forces, fault mechanics, and erosion. The Critical Wedge Theory provides a framework for understanding how these forces shape our planet, from the towering peaks of the Himalayas to the devastating earthquakes that periodically shake the region. By studying these processes, geologists can better predict seismic hazards and understand the ever-changing nature of our Earth’s crust.


The Elephant in the Room Seal Rock

The Elephant in the Room: Seal Rock

The Prevailing Suspect: Migration Issues?

My recent work in an area dominated by the belief that source rock and migration pathways are the primary culprits for exploration failures intrigued my curiosity. A quick burial history analysis revealed that even on regional highs, potential and effective source rocks were within the oil window. A 2D regional transect from the recent literature indicated that the source rock is well within the gas window, corroborated by the abundant adjacent seeps. Given that the structure is valid, the reservoirs possess adequate porosity and permeability, and the source rock is in the maturity window with evidence of migration (seepages), what could go wrong in the area?

petroleum system elements

Figure 1 Petroleum System Elements

Timing: Not Always the Villain

Timing is often cited as the main culprit in such scenarios. However, the recent concept of migration lag challenges this notion. Here, timing didn’t seem to be the issue (Figure 1). While examining the petroleum system further, the only remaining element, the “SEAL,” came to the spotlight.

regional high

Figure 2X-Section showing a regional high

The Seal Under Scrutiny

Well logs and mud log painted a concerning picture. The main top seal lacked the typical characteristics of an effective seal (not clay-rich or even shale-rich). Instead, it comprised roughly 300 meters of loose sand, friable sandstone with some shale beds, indicating a low shale gouge ratio and poorly compacted beds with larger pore throats. The overburden pressure was simply not enough to adequately compact the seal rocks. William C. Dawson’s work on the influence of depositional conditions on shale properties and seal character resonated here. It made me question how established regional high (Figure 2) could be explored twice without proper assessment of the top seal’s ability to hold hydrocarbons. Does that mean that shallow reservoir targets are riskier regarding SEAL integrity? Not necessarily.

Why Seal Effectiveness is Often Ignored

Seal effectiveness is often the most challenging element to predict in exploration, hence its frequently neglected. In his LinkedIn blog, Alan Foum mentioned that a significant amount of technical work is done on reservoir prediction using sequence stratigraphy, sedimentology, and reservoir geology. Basin modeling or petroleum systems modeling (and geochemistry) examines the source and migration, reducing the risk on hydrocarbon charge and helping predict the hydrocarbon phase. Seismic interpretation defines the trap, and advanced seismic attributes further aid in reservoir characterization. Yet, seal prediction remains largely ignored. Let’s peg deeper into this issue and find out why it has entrenched in the exploration.

What makes the Seal Conundrum

A study titled “Central North Sea Post Well Analysis” revealed a concerning distribution of exploration failures: Seal (38%), Trap (28%), Reservoir (17%), and Charge (14%). Despite this significantly high number, seal prediction is often ignored due to the industry-wide dogma that seal effectiveness depends solely on facies, thickness, and lithology, ignoring that in all cases, sealing capability depends upon the radius of the pore throat, densities, and interfacial tension. As Zhiyong He explains, the inability to measure seal capacity from seismic data forces explorationists to rely on depositional environment-based ranges and probabilistic migration models. This explains why many geologists, particularly when dealing with thick shale-rich systems, take seals for granted, assuming even a few meters can hold a significant hydrocarbon column. However, thickness alone doesn’t determine seal capacity and column height.

Seal Failure: Friend or Foe? Rethinking a Contentious Concept

Alan Foum references J. Karlo’s video outlining various causes of seal failure (micro-porosity, brittle fractures, hydraulic fracturing, fault displacement, and fault rock composition). While these mechanisms are well-established, recent research has challenged the blanket application of some aspects of the ‘contentious seal failure concept.’ In light of this, let’s scrutinize more closely why seal integrity remains a neglected factor in the oil and gas industry.

Beyond Misconceptions: Rethinking Seal Capacity

Zhiyong He dispels two common misconceptions:

  1. Shales are not impermeable: All shales have some permeability, allowing migration when the capillary displacement pressure is exceeded. Over geological timescales, even very tight shales can accommodate migration.
  2. Leaking seals don’t necessarily mean no hydrocarbons: A seal exceeding its capacity by buoyancy will still trap the maximum column it can hold, just not more. This capacity is typically around 200-400 meters for good marine shale and much less for poor deltaic mudstone.

Conclusion: Seals Deserve Attention

  • Seal rock integrity is a critical yet often overlooked factor in oil and gas exploration.
  • The complexity and difficulty in predicting seal effectiveness is the main reason it is sidelined, despite its significant impact on exploration success.
  • By understanding and examining the data related to seal rocks, explorationists can better evaluate the column a seal can retain.
  • This requires additional data acquisition, which might seem trivial but is highly effective.
  • Would you take SEALS for granted anymore?
  1. Dawson, W. C., Almon, W. R., Dempster, K., & Sutton, S. J. Shale Variability in Deep-Marine Depositional Systems: Implications for Seal Character – Subsurface and Outcrop Examples. (https://www.searchanddiscovery.com/pdfz/documents/2008/08144dawson/ndx_dawson.pdf.html)
  2. Foum, A. (2018). Keeping the hydrocarbons in the trap, effective seals in petroleum exploration. LinkedIn. (https://www.linkedin.com/pulse/keeping-hydrocarbons-trap-effective-seals-petroleum-exploration-foum)
  3. He, Z. (2023). Capillary Seals and Petroleum Migration Observations, Modeling and Risking. (https://www.sodir.no/globalassets/2-force/2023/dokumenter/he-zhiyong-capillary-seals-and-petroleum-migration-force-webinar-nov-2023_final-with-notes.pdf)
  4. Karlo, J. (2018). [Video]. YouTube. (https://www.youtube.com/watch?v=F_YyEpfoj0s)
  5. Moray Firth – Central North Sea Post Well Analysis. (https://www.nstauthority.co.uk/media/1578/cnsmf_post_well_analysis_report.pdf)
Exploring the Offshore Indus Basin Opportuintites

Exploring the Offshore Indus Basin: Opportunities and Challenges

Exploring The Offshore Indus Basin: Opportunities And Challenges

The Offshore Indus Pak G2-1, the deepest well drilled in the Offshore Indus in terms of water depth, offers interesting insights into the region’s hydrocarbon potential. Despite its depth, the 1D burial history graph (Figure 1) indicates that the well did not achieve the required burial to crack any hydrocarbons. This well, drilled near the Saurashtra Volcanic Arch, encountered a reef, yet remained dry, and the play couldn’t be established.

Reservoir Insights:

Drilling data reveals two sets of proven reservoirs in the Offshore Indus Basin

  • Widely Distributed Miocene Channel Sandstones
  • Locally Distributed Paleocene–Eocene Reef Limestone

Analogies with the adjacent Kutch Basin and the onshore Indus Basin suggest the possible existence of Cretaceous sandstone reservoirs in the Offshore Indus Basin.

Challenges and Historical Context:

The well stopped in the reef limestone after drilling over 200 meters, and unfortunately, it was dry. It was believed that the adjoining synclines would have generated hydrocarbons that would have migrated to the highs (the reefs) but the concept failed. Since the well was stopped early in the reef, remodeling of data in the context of basin is quite difficult. Had the well penetrated the basement, it would have been quite interesting. It was also believed that the reef would be riding all over the basement rocks.  The only proven reservoir is Middle Miocene deltaics that have produced gas in Pak Can-01, but the gas column was too small to justify infrastructure development.

It seems that volcanic activity plays a significant role in the evolution of the offshore part of the Indus Basin and its implications have far-reaching consequences on the hydrocarbon potential.

There have been two major volcanic events in the sea area of Pakistan:

Basalt Eruption of Somnath Ridge (~70 Ma)

Basalt Eruption of Deccan-Reunion (Reunion Mantle Plume, ~65 Ma)

According to Calvès et al. (2010), the basalt eruption of Somnath Ridge contributed to the formation of the volcanic basement in the southeastern Offshore Indus Basin, particularly around Somnath Ridge and Saurashtra High. This area covers approximately 45,000 km².

Geological Insights:

Seismic data interpretation indicates (Figure 2) (that in the southeastern part of the basin adjacent to Somnath Ridge and Saurashtra High, Deccan basalts are distributed in the marine-facies strata of the Upper Cretaceous–Paleocene in a laminated form (Khurram et al., 2019). The northwestern part, far from the Reunion mantle plume, has minimal basalt impact but is close to the strike-slip fault zone of Murray Ridge, making it a potential focus for future oil and gas exploration.

Geothermal Gradients:

Somnath Ridge: Low geothermal gradient of 33℃/km.

Sedimentary Center: High geothermal gradient of 37℃/km – 55℃/km, aiding source rock maturity (Calvès et al., 2010).

The northwestern part, with its developed faults near Murray Ridge, presents an interesting area for future exploration. There are chances that the established Cretaceous plays would be found there (Figure-02).

In most of the wells drilled, the source rocks are in oil window but Pak Can-01 produced gas suggesting that the gas would have been migrated from the deeper part of the basin. Modeling suggests that the Paleocene source rocks (effective in the adjoining onshore) may have become post mature at the end of Oligocene suggesting a charge to the Miocene and younger reservoirs by shallower source rocks.

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Exploring the Offshore Indus Basin

Figure 2 . After Shahzad et. al.


Calves G, Schwab AM, Huuse M, Peter DC, Asif I.  2010.  Thermal regime of the northwest Indian rifted margin Comparison with Predictions. Marine and Petroleum Geology, 27, 1133–1147.  doi: 10.1016/j.marpetgeo.2010.02.010.

Chatterjee S, Goswami A, Scotese. 2013. The longest voyage: Tectonic, magmatic, and paleoclimatic evolution of the Indian plate during its northward flight from Gondwana to Asia. Gondwana Research, 23, 238–267. doi: 10.1016/j.gr.2012.07.001.

Jian-ming Gonga, b, c, Jing Liaoa, b, *, Jie Lianga, b, Bao-hua Leia, b, Jian-wen Chena, b, Muhammad Khalid, Syed Waseem Haidere, Ming Meng. Exploration prospects of oil and gas in the Northwestern part of the Offshore Indus Basin, Pakistan

Shahzad K, Betzler C, Ahmed N, Qayyum F, Spezzaferri S, Qadir A. 2018. Growth and demise of a Paleogene isolated carbonate platform of the Offshore Indus Basin, Pakistan: Effects of regional and local controlling factors. International Journal of Earth Sciences, 107, 481–504. doi: 10.1007/s00531-017-1504-7.

OGDCL and Saif Energy Discover New Hydrocarbon Reserves in Kohat Block

OGDCL and Saif Energy Discover New Hydrocarbon Reserves in Kohat Block

OGDCL and Saif Energy Discover New Hydrocarbon Reserves in Kohat Block

In a significant development for Pakistan’s energy sector, OGDCL (Oil and Gas Development Company Limited) and Saif Energy Ltd (SEL) have announced the discovery of new hydrocarbon reserves in the Kohat Block through a joint venture partnership.

The exploration endeavor, undertaken on a sole risk basis, marks a milestone achievement for both public and private sector entities. The drilling operation commenced on August 28, 2023, and reached its target depth of 2414 meters in the Chichali-l Formation on November 18, 2023. Subsequently, the decision was made to deepen the well to test the hydrocarbon potential of the thrust sheet (Lumshiwal-Il), culminating in the successful achievement of TD 2600m MD (Chichali-Il) on December 07, 2023.

The exploratory efforts yielded promising results, with the testing conducted in the Lumshiwal-ll Formation revealing a Gas/Condensate discovery. The well exhibited a flow rate of 2.842 million standard cubic feet per day (MMSCFD) of gas and 28 barrels per day condensate (BPDC), accompanied by a wellhead flowing pressure of 540 pounds per square inch (PSI) at a 32/64” choke size.

Jehangir Saifullah Khan, CEO of SAIF ENERGY, emphasized the significance of collaboration between private and national companies for the betterment of Pakistan. He underscored the unique nature of the joint venture’s endeavor and highlighted the importance of such initiatives in advancing the country’s energy security and economic growth.

Stay updated on the latest developments in Pakistan’s energy landscape as OGDCL and Saif Energy pave the way for a brighter, more resilient future for the nation.

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