Abstract

In this work, a complex approach to studying a Paleozoic base structure of the East -Siberian plate is considered. The area of research is dated to the Nurol trough in the tectonical plane and despite a significant level of exploration maturity by various geophysical methods and drilling, there are many questions and unresolved problems.

Even a question as to correct mapping of pre-Jurassic surface remained opened until now as the roof of a Paleozoic section is changed by a paleodenudation so that the acoustic properties come nearer to the horizons of the bottom Jurassic complex. Also a seismic picture is complicated by a great number of various amplitude and extent tectonic deformations and the phenomenon of an interference connected with discordant bedding of the Jurassic sedimentary formation on the Paleozoic base.

To create an authentic geological model of reservoir structure, detailed interpretation of 3D seismic data combined with geophysical logging data was required. This interpretation includes structural, paleotectonical, seismic, and facial and dynamic analysis of the data being interpreted. The results of the analysis allowed to relate a certain regularity in forming a Paleozoic complex and reveal the most prospective areas of oil deposits.

Introduction

A study of Paleozoic formation of Eastern Siberia, where exploration interest is connected with carbon sediments, is connected with a number of difficulties. An oil and gas reservoir is characterized by a complex block structure complicated by zones of tectonic deformation, and the tectonic activity shown in Caledonian folding phase determined a peculiarity of oil accumulation.

To get a complete and authentic picture of a Paleozoic complex and to estimate a petroleum potential, detailed 3D seismic exploration was performed using a 25m × 25m survey network density. The processing was executed using the ProMax processing complex, and results obtained are suitable for further geological interpretation as a seismic dataset.

Seismic interpretation was made using the Landmark seismic application. Log data and test results of 38 exploration wells were also used. In general, geological interpretation was made on the basis of complex analysis of all available data. Besides structural imaging, the paleotectonical and seismic facial researches were conducted in combination with geophysical logging data and a seismic wave field.

A reconstruction of sediment history allowed resolution of such challenges as definition of a geometry formation, and forecasting of reservoir feature changes on the basis of litho-facial changes, a condition of trap formation. This in turn, enabled establishment of a certain regularity of a sedimentary magnitude development, as well as enabling forecasting of a near-real geological model.

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