What is caused by movement, expansion, and/or compression of wellbore fluids in response to a pressure change?

What is caused by movement, expansion, and/or compression of wellbore fluids in response to a pressure change?

• A. Wellbore Storage
• B. Skin Effect
• C. Diffusion Lag
• D. Reservoir Compressibility

Answer: (A)

Movement, expansion, and compression of fluids inside the wellbore when a pressure change occurs is the wellbore storage effect. When pressure is altered, the fluid column in the tubing and annulus must adjust its volume, so the wellbore temporarily stores or releases fluid. This creates an early-time pressure response that is controlled by how much fluid can be moved in or out of the wellbore, not by the surrounding rock formation. As a result, the initial part of the pressure response reflects the storage capacity of the wellbore rather than formation properties. Skin, diffusion lag, and reservoir compressibility describe near-well damage, delayed formation response, and rock volume changes with pressure, respectively, and do not capture the fluid movement inside the wellbore itself.

Movement, expansion, and compression of fluids inside the wellbore when a pressure change occurs is the wellbore storage effect. When pressure is altered, the fluid column in the tubing and annulus must adjust its volume, so the wellbore temporarily stores or releases fluid. This creates an early-time pressure response that is controlled by how much fluid can be moved in or out of the wellbore, not by the surrounding rock formation. As a result, the initial part of the pressure response reflects the storage capacity of the wellbore rather than formation properties. Skin, diffusion lag, and reservoir compressibility describe near-well damage, delayed formation response, and rock volume changes with pressure, respectively, and do not capture the fluid movement inside the wellbore itself.