Capabilities of Integrated Airborne Geophysical Surveys in Providing Geophysical Support for Regional Geological Studies and Predictive Exploration (Collected Papers)

Contents:

1. Kontarovich R. S., Babayants P. S. “Modern Advance Geophysical Support for Predictive Exploration: Problems and Prospects.”
2. Mogilevsky V. E. “Methods and Results of Airborne Gravity Surveys within the Area of Influence of New Oil and Gas Production Centers.”
3. Babayants P. S., Kertsman V. M., Levin F. D. “Capabilities of High-Altitude Airborne Gamma-Ray Spectrometry (up to 350 m and Higher) for Mapping and Exploration.”
4. Babayants P. S., Tararukhina N. M. “Specific Features of Integrated Airborne Geophysical Data Interpretation in Areas of Widespread Trap Rocks.”
5. Bush V. A. “New Data on the Structure of the Baikal–Taimyr Lineament and the Siberian Craton Basement Megablocks It Separates.”
6. Bush V. A. “Structure of the Irkineeva–Chadobets Aulacogen from Integrated Airborne Geophysical Survey Data.”
7. Levin F. D. “Capabilities of Integrated Airborne Geophysical Surveys for Predicting Hydrocarbon Reservoirs in the Southern Lena–Tunguska Petroleum Province.”
8. Levin F. D. “New Data on the Structure of Trap Fields in Southern Eastern Siberia from Airborne Geophysical Surveys.”
9. Levin F. D. “A Three-Dimensional Geological and Geophysical Model of the Verkhnechonskoye Hydrocarbon Field.”

This collection of scientific papers summarizes the most significant methodological and geological results of the integrated airborne geophysical survey conducted by CJSC GNPP Aerogeofizika in 2005–08 over 210,000 km² in the area served by the Eastern Siberia–Pacific Ocean (ESPO) oil pipeline. The survey area comprised parts of Krasnoyarsk Territory, the Sakha Republic (Yakutia) and Irkutsk Region adjoining the route of the pipeline under construction.

The survey area is a 200-km corridor along the initial section of the pipeline system, extending approximately along the 60th parallel from the Yurubcheno-Tokhomskoye field in the west to the Talakan–Verkhnechonsk cluster in the east. This corridor was prioritized for geological and geophysical investigation as the most promising area for increasing hydrocarbon resources and preparing them for commercial development. The airborne survey area crosses the Baykit and Nepa–Botuoba anteclises and the Katanga Saddle separating them. All previously discovered giant and large oil and oil–gas fields are concentrated within these tectonic elements. The area has the highest expected initial hydrocarbon reserve density in Eastern Siberia, yet its relatively limited geological and geophysical coverage suggests the potential for further reserve growth.

The integrated airborne geophysical survey conducted in this area by CJSC GNPP Aerogeofizika was unique in many respects. For the first time in the history of domestic and, to our knowledge, international airborne geophysical investigations, physical fields were measured at such high detail and resolution over so large an area (210,000 km²). This required solving exceptionally complex problems of coordinating flight operations and ground support. The survey operated from five base airports with 13 ground base stations. For the first time, detailed airborne gravity surveying was conducted on such a large scale using two types of measurement systems, requiring special data-processing procedures and methods for assessing survey quality. Finally, what we consider the first successful attempt was made to combine methods as different in their methodological requirements as airborne gravimetry and airborne gamma-ray spectrometry into a single survey system. This imposed certain limitations on the use of the gamma-ray spectrometric data, while also creating new opportunities to obtain geological information.

The interpretation methodology was shaped by the area’s geological structure, primarily the widespread trap rocks that substantially mask the effects of deeper geological targets, most conspicuously in the aeromagnetic data. This required developing and applying special techniques to suppress the effects of the traps. Failure to account adequately for this factor when using formal interpretation methods would inevitably have led to substantial errors in the geological interpretation of the results.

Processing and integrated interpretation of the airborne geophysical data using the latest algorithms and techniques, including those developed by the authors, yielded new geological information on the region’s structure and geological evolution. In our opinion, the following geological results deserve particular attention.

The internal structure of the pre-Riphean crystalline basement of the Tunguska and Magan megablocks of the Siberian Craton and the intervening Baikal–Taimyr Lineament zone was deciphered for the first time. A structural subdivision of the Magan megablock into relatively stable Archean blocks and mobile Early Proterozoic (?) tectonic zones is proposed.

The complex structure of the Riphean Irkineeva–Chadobets Aulacogen was identified, including a central zone of inversion uplifts containing the Chadobets Dome and peripheral subsidence zones that apparently contain the main volumes of oil and gas source rocks.

Analysis of aeromagnetic data identified normally and reversely magnetized units within the Lower Triassic trap complexes. This made it possible to distinguish four stages of their formation, differing in the nature of magmatic processes: the relative contributions of explosive activity, intrusion and subaerial effusion.

Combined analysis of gamma-ray spectrometric and gravity survey results revealed evidence of fluid flow through the regional salt-bearing seal. In many cases, these flows are associated with the formation and cementation of fracture–pore reservoirs in oil fields. The influence of neotectonic processes on the preservation of oil accumulations was identified.

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This collection presents the most important methodological and geological results of the airborne geophysical surveys. Its papers may be of interest both to specialists conducting airborne geophysical investigations and to geologists studying the structure of the Siberian Craton and assessing its oil and gas potential.

This collection of papers is CJSC GNPP Aerogeofizika’s first publication of this kind. Nevertheless, we hope it will establish a tradition of annual collections of papers by our specialists, summarizing the most interesting results of completed projects.