A build-up test is characterized by production at constant rate over time $t_p$, followed by shut-in period of $\Delta t$. A plot of shut-in bottom hole pressure ($P_{ws}$) with $\log \left(\dfrac{t_p+\Delta t}{\Delta t}\right)$ for pressure build-up test data is shown in the figure. Which of the following statement(s) is/are TRUE?
A build-up test is characterized by production at constant rate over time $t_p$, followed by shut-in period of $\Delta t$. A plot of shut-in bottom hole pressure ($P_{ws}$) with $\log \left(\dfrac{t_p+\Delta t}{\Delta t}\right)$ for pressure build-up test data is shown in the figure. Which of the following statement(s) is/are TRUE?
Show Hint
- Early Time Region (ETR): Pressure build-up data is affected by reservoir boundaries and other reservoir heterogeneities such as sealing faults
- Middle Time Region (MTR): Pressure build-up data is reached after end of the wellbore storage and the pressure transient has entered the virgin reservoir
- Late Time Region (LTR): Pressure build-up data is affected by reservoir boundaries and other reservoir heterogeneities such as sealing faults
- Middle Time Region (MTR): Pressure build-up data is affected by reservoir boundaries and other reservoir heterogeneities such as sealing faults
The Correct Option is B
Solution and Explanation
- ETR (Early Time Region): Dominated by wellbore storage effects. Reservoir boundary effects are not yet visible.
- MTR (Middle Time Region): After wellbore storage dissipates, the transient penetrates the virgin reservoir. Pressure data reflects actual reservoir properties like permeability.
- LTR (Late Time Region): At very late times, pressure transient reaches reservoir boundaries and heterogeneities (like sealing faults), causing deviations from linearity.
Step 2: Match with options.
- (A) Wrong — ETR is wellbore storage dominated, not boundaries.
- (B) Correct — MTR corresponds to virgin reservoir entry, valid.
- (C) Correct — LTR corresponds to boundary effects, valid.
- (D) Wrong — boundaries affect LTR, not MTR.
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