Status of Drill-Stem Testing Techniques and Analysis

This paper is a compilation of the latest drill-stem testing techniques. New tools are described, together with present-day interpretation techniques, and their limitations are given. The importance of proper times for shut-in and flow periods are stressed. A number of suggestions for the future are given, and a rather complete list of references in the field of drill-stem testing has been supplied for use by interested readers. Introduction A drill-stem test (DST) is a temporary completion. It consists of a combination of a packer arrangement and drill pipe or tubing. Valves are present in this arrangement to open and close the tool, and pressure and temperature recording devices are employed. Upon completion of the test, the entire arrangement is withdrawn from the well. The purpose of a DST isto determine whether or not to complete the well andto obtain reservoir or aquifer information for exploration applications. The DST will render a wealth of information - e.g., a sample of the fluid itself, the actual productivity index, the reservoir pressure, the theoretical productivity index and the amount of wellbore damage. The fluid will show whether the well can be completed as an oil well, a condensate well or a gas well; or, it will show if the formation should be abandoned (for being a water producer or for being dry). Tests can be run on the sample to determine the hydrocarbons present, viscosity of the mixture, API gravity, paraffin content, pour point or gas-oil ratio. The water produced can be analyzed for salinity and electrolytes present to aid in stratigraphic correlation, and the resistivity of the water will aid the logging engineer in his evaluation of the electric logs. The DST further aids in determining gas-oil or oil-water contacts, and the proximity of pinchouts or faults.