2017 Volume 82 Issue 3 Pages 189-203
The Amu Darya Basin is a proven hydrocarbon-bearing basin extending from Turkmenistan to northern Afghanistan. A number of fields have been discovered in the Afghan side of the basin: The Jangal-e-Kalan, Yatimtaq, Khwaja Gogerdak and Khwaja Bulan gas fields in the northwest, and Angot oil field in the southeast. There is however a limited number of researches on the petroleum system of the area, remaining it poorly understood.
One-dimensional basin modeling was conducted to reconstruct the burial and thermal history, and simulate hydrocarbon generation and expulsion in the Afghan side of the Amu Darya Basin. The principal objectives were to estimate the maturity of the Lower and Middle Jurassic source rocks, and to determine the kitchen areas and timing of hydrocarbon generation and expulsion.
This study was carried out along a published geological cross section which traverses the basin in NW-SE direction. The data obtained from actual wells were used to calibrate modeling parameters. Three pseudo wells were then created at synclines along the section for simulating hydrocarbon generation and expulsion in the potential kitchen areas.
The major finding of this study is that the maturity of Lower and Middle Jurassic source rocks varies in different parts of the basin. At the northwest syncline (pseudo well-1), the source has reached the gas window in Cretaceous, and has expelled gas since then. The area is therefore most likely the kitchen for the neighboring gas fields. On the other hand, the source in the southeastern syncline (pseudo well-3) is now at peak to late oil window, and is expelling oil. The Angot oil must be charged from this syncline. The source in the middle part (pseudo well-2) is also in its late oil window. The difference from pseudo well-3 is that it has undergone uplifting since Paleogene, indicating hydrocarbon expulsion has ceased before trap formation.
