Hydrocarbon well test method
First Claim
1. A well test method for determining the physical characteristics of a system consisting of a well and of a subsurface formation a system consisting of a well and of a subsurface formation containing a fluid such as a hydrocarbon and communicating with said well, wherein the formation is homogeneous or heterogeneous and exhibits the skin effect and/or the wellbore storage effect, comprising changing the flow rate of said fluid and measuring a characteristic parameter of the pressure P of the fluid at successive time intervals Δ
- t, the change of flow rate being carried out in a short period so as to obtain a flow pulse resembling a Dirac pulse, with the amplitude of said flow pulse being sufficiently high to allow the measurement of said characteristic parameter of the pressure P of the fluid at said successive time intervals Δ
t, and being characterized in that one also measures the variations in the pressure P of the fluid during said short period, then during the subsequent period of return to the initial state of the well-formation system, and one compares the experimental pressure curve thus obtained with the curves of a double network of type curves representing, as a function of a common parameter, the pressure P and its derivative P'"'"' with respect to time, by matching the branch of the experimental curve corresponding to the short period with a curve P and the branch of this curve corresponding to the subsequent period with the curve P'"'"' of the same parameter.
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Abstract
The invention relates to a well test method for determining the physical characteristics of a system made up of a well and a subsurface formation containing a fluid such as a hydrocarbon. A change in the flow rate of said fluid is produced for a short period (duration tP of the order of a few minutes) so as to obtain a flow pulse resembling a Dirac pulse; the variations ΔP of the down-hole fluid pressure is measured during said short period and then during the subsequent period of return to the initial state of the well-formation system, and the experimental pressure curve thus obtained is compared with the curves of a double network of type curves representing, as a function of a common parameter, the pressure PD and its derivative P'"'"'D with respect to time, by matching the branch of the experimental curve corresponding to the short period with a curve PD and the branch of this curve corresponding to the subsequent period with the curve P'"'"'D of the same parameter.
16 Citations
8 Claims
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1. A well test method for determining the physical characteristics of a system consisting of a well and of a subsurface formation a system consisting of a well and of a subsurface formation containing a fluid such as a hydrocarbon and communicating with said well, wherein the formation is homogeneous or heterogeneous and exhibits the skin effect and/or the wellbore storage effect, comprising changing the flow rate of said fluid and measuring a characteristic parameter of the pressure P of the fluid at successive time intervals Δ
- t, the change of flow rate being carried out in a short period so as to obtain a flow pulse resembling a Dirac pulse, with the amplitude of said flow pulse being sufficiently high to allow the measurement of said characteristic parameter of the pressure P of the fluid at said successive time intervals Δ
t, and being characterized in that one also measures the variations in the pressure P of the fluid during said short period, then during the subsequent period of return to the initial state of the well-formation system, and one compares the experimental pressure curve thus obtained with the curves of a double network of type curves representing, as a function of a common parameter, the pressure P and its derivative P'"'"' with respect to time, by matching the branch of the experimental curve corresponding to the short period with a curve P and the branch of this curve corresponding to the subsequent period with the curve P'"'"' of the same parameter. - View Dependent Claims (2, 8)
- t, the change of flow rate being carried out in a short period so as to obtain a flow pulse resembling a Dirac pulse, with the amplitude of said flow pulse being sufficiently high to allow the measurement of said characteristic parameter of the pressure P of the fluid at said successive time intervals Δ
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3. a network of curves representing the evolution of the dimensionless pressure PD,
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4. and a network of curves representing the evolution of the product of tD /CD multiplied by the derivative P'"'"'D of the pressure PD in relation to tD /CD, while the experimental pressure curve is also plotted in logarithmic coordinates, after having undergone the following operations:
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5. the values of the pressure variations Δ
- P of the branch corresponding to the short period are multiplied by the duration tp of this period,
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6. and the values of the pressure variations Δ
- P of the branch corresponding to the subsequent period are multiplied by the time Δ
t elapsing since the beginning of the short period,
- P of the branch corresponding to the subsequent period are multiplied by the time Δ
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7. the amplitude of the vertical and horizontal shifts necessary for matching as well as the value determined for the parameter then making it possible to determine characteristics of the well-formation system, based upon the measured value of the total amount of fluid produced or injected during the short period.
Specification