Wellbore Fill Up
Definition - What does Wellbore Fill Up mean?
Wellbore Fill Up refers to the flow of fluids into a wellbore due to their compressibility; this occurs as a result of the well being shut at the surface rather than at the downhole. The flow into the wellbore takes place mainly because of the compression of gases. Due to the Wellbore Fill Up, the sandface flow-rate is never zero and thus, it is never stable or constant.
Petropedia explains Wellbore Fill Up
When the surface of a well is shut, it leads to compressibility of the fluids present in the borehole. This state of compression is a result of the corresponding change in the volume of the fluid related to the unit change of pressure. The compressibility of the fluids leads to the uncertain flow of these fluids into the well. The compression of gases present in the wellbore also adds into the situation and results in the heavy flow of fluids into the well. This unexpected flow of fluids into the well is known as Wellbore Fill Up. This unexpected flow of fluids can also lead to a situation known as wellbore storage effect.