Print this pagePreliminary Geochemical Study of Afghanistan and Tajikistan Petroleum and Source Rocks
Ronald J. Hill1, Paul G. Lillis1, J. David King1, Tim Klett1, Gregory Ulmishek1,
Craig Wandrey1, Amir Zada Abdul2, Amir Mohammad Selab2, K. Khalikov3,
and Khayot Z. Latyfov3
1 U.S. Geological Survey, Denver, CO
2 Afghanistan Ministry of Mines and Industry, Kabul, Afghanistan
3 Tajikistan Ministry of Energy, Dushanbe, Tajikistan
Petroleum, natural gas, and potential source rock samples were collected from Afghanistan and Tajikistan as part of a study to assess the petroleum resource potential of Afghanistan. Samples from Tajikistan are important for developing a regional petroleum system framework for evaluating resource potential. Three potential Paleogene source rock horizons were identified from core and outcrop analysis, with total organic carbon values of 2.8%, 13.9%, and 19.7% and Rock Eval hydrogen indices (mgHC/gTOC) of 800, 569 and 519, respectively. Biomarker and stable carbon isotope analysis of rock extracts demonstrate the presence of three distinct organic geochemical facies, indicating the possibility that three individual petroleum systems are represented.
Oils were collected from the Angot and Akhmadabad fields, Afghanistan, and from the Bishtentyak and the Shaambari fields, Tajikistan. Geochemical analyses of the Angot oils indicate generation from a possible Jurassic carbonate source rock, whereas Akhmadabad oil is biodegraded and derived from a marine shale. Oils from Tajikistan are from marine shale and marl and are geochemical distinct from the Afghan oils. None of the oils, however, correlate with the sampled Paleogene source rocks, indicating that as many as seven source rocks may have contributed petroleum to the petroleum systems in the region.
Gases, obtained from the Khaja Gagerdak and the Jarquduk fields in Afghanistan, are thermogenic and the Khaja Gagerdak samples (wetness ~ 0.03%; methane δ13C1 = -27.6‰) are interpreted to be higher maturity than the Jarquduk samples (wetness ~ 1.5%; methane δ13C1 = -31.1‰), based on molecular and isotopic compositions.