Analysis of slug and drillstem tests

This work presents new procedures for the analysis of slug and drillstem tests. The proposed methods account for the flow rate variation, however, no direct measurement of the sandface rate or its determination from the liquid recovery are needed.;A new general method for determining the formation flow capacity and the skin factor from slug test data is presented. It is shown that the slug test response can be converted to the response for an equivalent constant surface rate, wellbore storage and skin problem. The equivalent constant rate pressure data is obtained by integrating the measured slug test pressure over producing time, whereas, multiplication of the slug test pressure data by the producing time yields the equivalent constant surface rate pressure derivative data. After the constant surface rate pressure data and its derivative are generated by our procedure, the converted data can be analyzed by using existent wellbore storage and skin type curves for the particular reservoir model represented by the data. Therefore, slug test type curves are no longer needed. It is also shown that the well known rate normalization procedure and the traditional superposition method can also be applied to the converted pressure data to greatly improve the reliability of the analysis.;Two new straight-line methods for analyzing pressure buildup data obtained from drillstem tests are presented. The new methods apply for cases where the produced fluid does not reach the surface during the flowing period. From the slope of the straight line obtained by either method, it is shown that the flow capacity, the skin factor and the initial reservoir pressure can be determined. If the beginning of the straight-line is delayed by wellbore storage and skin effects, it is shown that a multi-rate equivalent time can be constructed so that standard type-curve matching can be performed to obtain estimates of the flow capacity and the skin factor.;New deconvolution schemes for the analysis of slug and drillstem test pressure data are also proposed. The new algorithms do not require the measurement or direct computation of the sandface flow rate during the flow and buildup periods.