Thermal Transient Testing using TDS Technique.
ABSTRACT
In the estimation of most reservoir parameters in well test, the reservoir is assumed to be isothermal which is practically not true due to the fact that there are heat sources due to friction in the wellbore, works done by the drill bit and in thermal recovery. Although, this temperature change is small, it can serve other beneficial purposes in the reservoir and wellbore. The research work used the temperature change to estimate permeability, skin factor and initial temperature of the reservoir.
This work brought out equations to be used in the estimation these reservoir parameters and the applied to field data. These results obtained compared with the true reservoir parameters of field data were almost the same especially the permeability and initial reservoir temperature although the same could not be said about the skin factor since that of the estimated and true value were quite different.
This research work brought out the idea that thermal transient testing can be used as a tool for estimating some reservoir parameters or as verification for estimated parameters using other well test methods. This research work also generated type curve for dimensionless temperature derivative versus shut-in time for different skin factors as well as type curve for dimensionless temperature derivatives versus shut-in time for different dimensionless radii with their respective behaviors.
TABLE OF CONTENT
Signature Page . . . . . . . . . i
Title Page . . . . . . . . . ii
Abstract . . . . . . . . . iii
Dedication . . . . . . . . . iv
Acknowledgements . . . . . . . . . v
Table of Contents . . . . . . . . . vi
List of Figures . . . . . . . . . ix
List of Tables . . . . . . . . . x
Chapter One – Introduction . . . . . . . . . 1
1.1 Introduction. . . . . . . . . . 1
1.2 Statement of Problem. . . . . . . . 1
1.3 Objectives. . . . . . . . . . 2
1.4 Scope of Work. . . . . . . . . 2
Chapter Two – Literature Survey 3
2.1 Introduction. . . . . . . . . . 3
2.2 Pressure transient testing. . . . . . . . 3
2.3 Pressure Drawdown Test. . . . . . . . 5
2.4 Pressure Build-up Test. . . . . . . . 5
2.5 Pressure Derivative. . . . . . . . . 6
2.6 TDS Technique. . . . . . . . . 8
2.6.1 The Mathematical Model. . . . . . . 8
2.6.2 A step-by-step procedure for the basic case (Tiab, 1995). . 11
2.7 Temperature disturbance in a Well.. . . . . . 12
2.8 Thermal Effect on gas wells.. . . . . . . 13
Chapter Three – Derivation of Relevant Equation . . . . . . . . . 15
3.1 Introduction. . . . . . . . . . 15
3.2 Mathematical Model.. . . . . . . . 15
3.2.1 Derivation of any expression for permeability. . . . 17
3.2.2 Derivation of any expression for skin. . . . . 19
3.3 Applying TDS technique to thermal transient. . . . . 20
3.4 Equations extended to real gases. . . . . . . 22
3.4.1 Considering the Van Der Waals forces. . . . . 23
3.4.2 Pseudo Reduced Temperature function. . . . . 24
3.5 Developing type curves from dimensionless temperature
and time functions for different rD.. . . . . . 25
3.6 Developing type curves from dimensionless temperature
and time functions for different skin factors. . . . . 27
CHAPTER FOUR – Application of Equations to Field Data . . . . . . . . . 28
4.1 Introduction. . . . . . . . . . 28
4.1.1 Estimating the Permeability using Semi-log thermal transient. . 32
4.1.2 Estimating the skin using Semi-log thermal transient. . . 33
4.2 Applying the TDS technique to the temperature data. . . . 33
4.2.1 Estimating the permeability using TDS thermal transient. . 36
4.2.2 Estimating the skin using TDS thermal transient. . . . 37
4.3 By applying this Pseudo Reduced Temperature function. . . 37
CHAPTER FIVE – Discussions of Results . . . . . . . . . 42
5.1 Discussion of results conventional thermal transient and
thermal transient using TDS technique. . . . . . 42
5.2 Benefits of thermal transient test over Pressure transient test. . . 45
5.2 Discussion of results of the real pseudo reduced temperature functions. 46
5.3 Discussion of type curves generated for the dimensionless
Temperature derivative for different dimensionless radii. . . 47
5.4 Discussion of type curves generated for the dimensionless
temperature derivative for different skin factors. . .. . . 49
CHAPTER SIX – Conclusion and Recommendations . . . . . . . . . 51
6.1 Conclusion. . . . . . . . . . 51
6.2 Recommendations. . . . . . . . . 51
REFERENCES . . . . . . . . . 53
INTRODUCTION
The effects of pressure transient in fluids at near-wellbore, homogenous and reservoir boundary regions have been studied extensively. Important reservoir parameters like permeability, skin factor, porosity, reserves, pressure drop, pressure drop due to skin, wellbore radius, productivity index, flow efficiency, damage ratio, wellbore storage, pore volume and drainage area have all been estimated using pressure transient testing.
These reservoir parameters have been estimated with the assumption that change in temperature is relatively small and hence considered to be negligible in fluid flow. This isothermal assumption used in the estimation of these reservoir parameters, is not entirely true. This is due to the fact that there are heat sources due to friction in the wellbore as well as works done by the drill bit (Marshall et al 1992).
The understanding of thermal transient effect will help in better analysis of the reservoir or well to effectively maximize production rates. It will also help in the management and optimization of the reservoir. This will also help in planning the type of drilling methods, drive mechanism and production schemes to effectively maximum production.
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StudentsandScholarship Team.