Latest Developments In Inflatable Packer Drill-stem Testing

Abstract

Abstract An inflatable packer drill-stem testing system, featuring the latest equipment available, was introduced to the field in March of1979. The system"s technological advances (noted below) and a review of the system"s development are described in detail. CONTROLLED PUMPING CAPABILITY- continuous control of the inflating pump"s output pressure, even during extended pumping time, is provided by incorporating a variable-angle, swash-plate-type plunger drive mechanism. INCREASED TEST ASSURANCE - unique back-up systems for swash-plate control and pump suction and discharge valves are provided by a combination pressure relief/check valve. SIMPLIFIED OPERATION-a telescoping sequence Valve controls inflation, venting, equalization and deflation, and synchronizes these functions with each other and with the operation of the hydraulic main valve. DECREASED JARRING AND FISHING- a special emergency deflate tool, operated by pulling a predetermined amount of tension on the drill pipe to break a tension sleeve, ensures deflation if the normal deflate mechanism does not operate. INTRODUCTION More than a quarter century of conventional drill-stem testing experience in the Alberta oil fields has enabled the Canadian well service industry to develop well testing into a modern technology. The introduction of inflatable packers in open hole drill-stem testing has made it possible and practical to test wells successfully under conditions where conventional drill-stem testing is impossible. Washed-out holes and soft formations present difficulties in obtaining packer seats with the weight-expanded packers used in conventional work. Inflatable packers, being capable of expanding to a significantly larger diameter than conventional packers of the same unexpanded diameter, have proved effective in those applications where difficulties are experienced with conventional packers. Also, with the advent of the inflatable packer has come the capability of testing several zones during a single trip into the hole, because tail pipe to set weight on is not required for seating the packers. With the inflatable packer being a relatively new development (compared with conventional systems), several different approaches to tool systems have been pursued in recent years, and their development is continuing. The latest equipment available was introduced to the field in March 1979 after an extensive test-well program. This equipment and its history and subsequent development are described. The Tool System Various configurations of the inflatable packer tool string are shown in Figures 1,2 and 3. Several tools, such as jars, safety joints and reverse circulating subs, have been omitted from the drawings for simplicity. These different arrangements provide the capability of conducting:long-interval straddle tests (Fig. I);short-interval straddle tests (Fig. 2);bottom-hole tests (Fig. 3). Straddle testing an interval of more than 5musually involves the use of blank-anchor or drill-collar spacing between the packers, as shown in Figure 1. Intervals of 5mand less can be tested without the spacing (Fig. 2), and the minimum interval possible with this tool string is 2.3 m. The bottom-hole configuration (Fig. 3) normally uses two packers to resist skidding down the hole when the hydraulic main valve is opened and the tools have to support the weight of the mud column.