**Kansas Geological Survey, Open-file Report 88-28**

# Thermal Basin Modeling and Analysis using the Time-Temperature Index

### An Improved General Basin Model Incorporating Compaction, Fluid Flow and Heat Flow

by

J. J. Woods, G. C. Bohling, C. D. McElwee, and K. D. Newell

KGS Open File Report 88-28

## I. Introduction

Thermal basin modeling has been a widely-used technique for estimating the maturity of sedimentary basins. Many of the existing thermal basin models compute the time-temperature index (TTI) as a numerical estimate of the maturity of the source beds. The majority of these models are very simple and involve the solution of the heat flow equation with varying thermal gradient and thermal conductivity of the sediments.(refs. 1 2 3).

In the following four sections we present the details of a much more general model. This model involves solution of heat flow, compaction and water flow equations and allows the density, thermal conductivity, compressibility, specific heat, and permeability of sediments to vary with temperature and pressure. Different options are also allowed for modeling the flux changes throughout time. Pertinent equations are presented in section II along with a brief description of the model and the algorithm for the simulation. Section III consists of information regarding choice of model and physical parameters, analysis of results for four different basins,, and conclusions. The fourth and final section is a complete description of the use of the computer program. our purpose is to examine the effect of various phenomena and changes in properties on the iso TTI contours and on the TTI of a given sediment point in a geologic formation. The principal phenomena of interest are:

- sedimentation rate changes.
- changes in heat flux and/or thermal conductivity (with discussion of effects of heat flux, thermal conductivity, and specific heat changes on thermal gradient)

To illustrate the effects of sedimentation rate changes and changes in the thermal properties, a Gulf Coast model will be presented at various degrees of complexity. Using the information gained from this analysis, a more detailed Salina basin model will then be analyzed. The Salina basin model will be then used to further study the effects of compaction and water flow. Finally, to demonstrate the affects of realistic changes in heat flux (with time), the results of an Ardmore basin model will be presented.

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Kansas Geological Survey

Placed online March 5, 2010

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