3D Analysis of Temperature and Heat flow in Steady State Approximation in the Halten Terrace

Abstract

Thermal effects and heat flow distribution are of major interest as they affect the petroleum system in a sedimentary basin. Heat controls the maturation and generation of hydrocarbons as well as the reservoir quality. Porosity loss due to quartz cementation is directly related to the thermal history of the area.

The Åsgard Field is located in Halten Terrace in the Norwegian Sea. It is general accepted that two Triassic salt layers separated by clastic sediments are present in the region. The presence of salt deposit impacts the thermal regime in the sedimentary basin, due to its high conductivity and complex structure.

Based on the interpretation of the seismic cube, HVG13, performed in the previously specialization project \citep{Hovda}, in addition to wire-line data from eight wells in the Smørbukk and Smørbukk Sør Fields, the thermal effects and heat flow distribution on the reservoir quality have been studied. This dissertation estimates the present-day heat flow and discusses the effects of salt thickness and geometry related to the heat flow distribution. Heat flow maps over the area were estimated from well logs using Bullard's plot and from ray tracing. Isotherms were calculated using an internal Statoil Petrel plug-in, providing the present-day temperature of the area. The isotherms indicate that Åsgard field consists of high pressure, high temperature reservoirs.

A weak correlation between the Triassic salt thickness and the vertical heat flow distribution using Bullard's plot was observed. The lack of assessment of 3D geometrical effects in the subsurface contributed in only a weak correlation.

The present-day heat flow distribution was also analyzed based on the ray path and the geometry of the Triassic salt. The result of this showed that a syncline shape of the Triassic Salt provides focusing of rays and an anticline shape of the Triassic Salt provides de-focusing of rays in the above sediments.