Gas generation and accumulation in the West Siberian basin (Discussion & Reply)

Abstract

Littke et al. (1999) present a novel hypothesis for the genesis of the supergiant gas accumulations in the northern West Siberian basin through exsolution of gas from formation water. Some problems are attached to their interpretation, the principal of which are discussed in the following paragraphs. 1. Littke et al. (1999) discard supply of thermal gas from the Jurassic because of the pressure differential between that section and the overlying Cretaceous (their figure 4). Most unlikely, however, is that the high pressure in the deeper section is caused by undercompaction, given the slow to moderate rate of deposition during the Jurassic-Cretaceous and the long time span since deposition coupled to the abundance of permeable sands providing drains for the compaction water, even in the more shaly sections (Achimov-type sands). Much more likely is that the overpressure is generated by kerogen-to-oil/gas conversion …