Question

An Ideal Pressure Buildup Test yields a single straight line for all times, when shut-in Bottom-Hole Pressure (\(P_{ws}\)) is plotted against \(\log_{10} \left( \frac{t_p + \Delta t}{\Delta t} \right)\). Here \( t_p \) is the well production time and \(\Delta t\) is the time elapsed since shut-in. However, in an actual Pressure Buildup Test, a non-linear curve is obtained which can be logically divided into distinct regions. Choose the INCOMPLETE option from the following.

• A. A late-time region, in which the radius of investigation has reached the well's drainage boundaries.
• B. A middle-time region during which the pressure transient has moved away from the wellbore and into the bulk formation.
• C. An early-time region during which a pressure transient is moving through the formation nearest the wellbore.
• D. An early-time region during which a pressure transient is moving away from the drainage boundary.

Hint:

In a pressure buildup test, the early-time region is characterized by pressure changes occurring near the wellbore as the pressure transient moves outward to the surrounding formation.

Answer 1

The Correct Option is D

In a typical Pressure Buildup Test, the relationship between bottom-hole pressure and elapsed time after shut-in is analyzed. The pressure buildup curve is divided into distinct time regions, each corresponding to different behaviors in the pressure response. - Late-time region (A): At this stage, the radius of investigation has reached the drainage boundaries of the well, and the pressure response reflects the interaction between the wellbore and the formation at large distances. - Middle-time region (B): During this phase, the pressure transient has moved away from the wellbore into the bulk formation, and the pressure changes are more influenced by the reservoir properties. - Early-time region (C): This phase is dominated by the behavior near the wellbore, where the pressure transient is moving through the formation closest to the well. - Incorrect option (D): In the early-time region, the pressure transient is moving toward the drainage boundary, not away from it. This makes option (D) incorrect. In the initial phase, the pressure disturbance spreads outward from the wellbore to the surrounding formation, not the other way around. Thus, the correct answer is (D) An early-time region during which a pressure transient is moving away from the drainage boundary.