High Resistive Anomalies Beneath Permafrost Layer as New Hydrocarbon Prospecting Indicator

Detailed geophysical survey was carried out in 2014–2015 in Novotaymyr block located in Yenisey-Khayanga trough. One of main percularituy of the survey area is presence of sevral proven hydrocarbon deposits: Ozernote gas deposit, Payakhskoe oil deposit and baikalovskoe gas codensate deposit.

A specific patter was detected according to the electrical prospecting data interpretation: high resistive anomalies are presented above the hydrocarbon reservours at depth of about 300–800 m below permafrost layer.

Despite the lack of definitive conclusions about the nature of the revealed high resistive anomalies identified anomalies in the upper part of the section, the mere presence of these anomalies can be treated as hydrocarbon prospecting indicator that can be used in solving the following tasks:

1. Prediction of oil and gas occurrence. Near-surface high resistive anomalies in the upper part of the section are directly linked with the industrial accumulation of hydrocarbons in the deep productive layers.
2. Defining the boundaries of the deposits. In areas characterized by subhorizontal bedding and absence of non-permeable layers and/or subvertical permeable faults, the migration of hydrocarbons occurs mainly in the vertical direction. Therefore, based on the concept of nature, related to gas hydrates and free gas, it is possible to make an assumption about the similarity of dimensions and outlines of near-surface anomalies with hydrocarbon reservoirs at depth.
3. Identification of zones of geological and drilling hazards. It is obvious that the accumulation of gas or/and gas hydrates beneath permafrost layer could cause destruction of engineering infrastructure structures and drilling sites on the surface.