MAGNETIC AND GRAVITY-ANOMALY PATTERNS RELATED TO HYDROCARBON FIELDS IN NORTHERN WEST SIBERIA

A study of the features of gravity and magnetic fields in the vicinity of oil and gas reservoirs in West Siberia demonstrated a spatial rela tionship with the hydrocarbon deposits. The relevant magnetic and grav ity anomalies cover approximately 900 000 km(2) in northern West Siber ia. Amplitude and frequency were investigated initially using double F ourier spectrum (DFS) analysis. This was followed by (1) application o f transformations, filtering, and ''moving windows'' analysis; (2) com pilation of maps of regional and local anomalies, and potential field derivatives; and (3) investigation of the distribution of parameters i n areas of known deposits. Hydrocarbon deposits are located mostly at the slopes of positive regional gravity and magnetic anomalies which a re interpreted as relating to deep riftogenic structures. At the same time, it is established that the location of hydrocarbon depositions c oincides commonly with local gravity and magnetic minima generated by lows in basement density and magnetization. All known hydrocarbon depo sits in northern West Siberia are in areas characterized by comparativ ely high gradients of constituent of gravity anomalies with a waveleng th of about 90-100 km. These newly revealed links between reservoirs a nd potential field parameters may be a means to predict new discoverie s in poorly explored territories and seas, primarily in Russia's Arcti c shelf.