Publications

Pressure Build-up Interpretation in a giant gasfield in S.E. Asia has been difficult and ambiguous because no semilog straight line developed in many tests. Problem wells are those which are only partially perforated. The pressure derivative of these wells does not show the characteristic levelling off for infinite acting radial flow, but keeps declining at a slope of about minus half. It is shown that this behaviour is characteristic of spherical flow. The data should be analysed using a spherical and not the common radial flow model: Long measureable afterflow lasting for up to five hours complicated the interpretation. It is shown that the measureable afterflow from about 15 minutes after shut in is due to shrinkage of gas in the wellbore as it cools down.