Permneftegeophysika Explores Hard-to-Reach Areas of the Western Urals

With respect to orohydrographic, geological and landscape characteristics, the Perm Territory is a unique region where seismic investigation of oil and gas presents many difficulties. 

Current application of 3D seismic is mostly to refine the geological structure of oil fields. Microspread source-receiver configurations are used, with 200-300 m distance between lines and 25-50 m spacing between source and receiver points. Seismic vibrators assembled on Kraz and Ural trucks are usually used for excitation.

When the area of interest is 60 percent covered by forest, surveying 100 sq. kilometers  with traditional seismic techniques would require deforesting more than 100 hectares for routes of source lines, involving large expenditures and, moreover, environmental disturbance. Under these conditions, forested areas are inaccessible for seismic surveys. A similar situation occurs in open marshes where woodlands are less prevalent, but due to water salinity the marshes freeze only shallowly, prohibiting heavy vehicles with vibrators from passing; the platforms of vibrators usually break through the thin layer of ice.

To solve geological problems under these orohydrographic conditions, the traditional method of survey performance was rejected and seismic crews were provided with small portable equipment and vehicles that can navigate the forest without felling trees.

The smaller equipment complex consists of light drilling rigs up to 300 kg and 1 m wide, assembled on sledges and towed by Buran snowmobiles (for winter operations). For the summer, self-propelled tool carriers were designed with the Kurgan plant Avtoremont. The drilling rigs are rated for holes 60 mm in diameter and of the necessary depth (usually to 10 meters); the charge (up to 0.1 kg) is run to the set depth through hollow screws.

Seismic cables and receivers are carried and uncoiled manually or on self-propelled tool carriers and “Buran” snowmobiles. The lines of source points and geophones are up to 1 meter wide instead of the usual 4-5 meters, and the environmental impact of the technology is minimal. Moreover, the 3D survey was obtained with no deviations from the orthogonal net and with the complete absence of SP skips in the environment of the sub-mountain relief (slopes up to 30 degrees, ravines, steep river banks), in forests of the 1st category, and in forest and landscape preserves (Fig. 1). The figure shows that the mismatch between the planned and actual grids was only 2 percent.

This seismic survey technology was initially designed for forested areas and open marshes.

Application of this seismic technology in hard-to-reach areas of the Perm Territory over the last four years enabled the study of 16 areas: 14 by the 3D version and two by the 2D version.

High geological efficiency of operations was achieved in all cases.
An ecological highlight of the technology is its elimination of the need for deforestation for seismic line routes.  In 2006, specialists from Permneftegeophysika received a patent for 3D seismic surveys in hard-to-reach areas: Useful model patent No. 61894.

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