New Approach To Oil And Gas Potential Of Barents Sea And Timan-Pechora Basin
Authors: Nevskaya N.M. 
Published: October 2008

High temperatures at large depths of Barents shelf and Timan-Pechora basin cause the formation of homogeneous steam-liquid mixtures consisting of supercritical water and dissolved hydrocarbons. The analysis of themobaric conditions allowed to distinguish the zones of possiblehydrocarbon accumulation. The conclusions allow to make more precise future exploration.

INTRODUCTION

A new point of view on hydrocarbon search consists in an approach to this problem with the positions of fluid (in particular, water) physical state. At supercritical temperatures(&gt;+374º.C), the water represents a dense polar fluid with the unique properties. Considerable dissolving ability of this polar fluid favours the hydrocarbon dissolution in it; and a low viscosity provides its high migration properties. Areas of supercritical water distribution in the sedimentary strata may be considered as ones of probable hydrocarbon accumulation.

STATEMENT OF THEORY AND DEFINITIONS

Structure and physical state of water permit to define a number of hydro physical zones in earth crust. The first hydro physical zone is the solid water zone with ice structurewith negative (or zero) temperatures and normal (or low) pressures. The second hydro physical zone is represented by the free structurization waters with temperatures of O to +374º-450ºC and formation pressures of 1 to 25000 atm at depths several ten kilometers. The division of the hdrophysical zones is shown by the isotherms, corresponding o phase transition ice-water and water-steam for thenatural solutions. A great bulk of the free underground waters oceures in the upper ten kilometers of the geological section.

The fluid physical characteristics of the second hydrophysical zone are of interest for petroleum exploration. A character of formation pressure distribution in this zone permits to determine the hydrodynamic subzones of hydrostatic, ransitional and geostatic (Iithostatic) pressures. In the ydrostatic pressure subzone. the formation pressures 'are enerated by water exchange in the recharge or discharge rea. In the geostatic (Iithostatic) pressure subzone, the ormation pressures are primarily genereted by the extension nd compression tectonic factors; and here the pressuregradients reach 2.3-2.5. There is a wide range of formation pressure values in the transitional zone (from hydrostatic to gcostatic ones); and the gradients range from 1.25 to 2.3. The formation energy in the transitional subzone primarily formsenergy transmission from the geostatic pressure subzone. Within the limits of a studied part of Timan-Pechora province (VP) section and Barents shelf two upper subzones (subzones of hydrostatic and transitional pressures) can be determined. In both cases, zones of tectonic disturbances are he bases of fluid discharge.

Therefore, the second hydrophysical zone is characterized by ide range of the thermodynamic parameters (temperature and pressure) that determine the fluid properties, in articular, water.

The water physical properties and structure at high mperatures and pressures at great depths are of most interest. In these conditions water properties can be determined on parameter changes. It is known that water tructure change, i.e. transition from fluid to vaporous state ith forming of water steam and water occures at critical emperature (+374º.C).