Impulse tests, Perforation Inflow Diagnostic (PID) tests and Closed Chamber tests are all similar in methodology. By whatever name, they provide simple, quick, cost-effective snapshots of maximum reservoir inflow characteristics. In a matter of minutes a field Engineer can provide estimates of the maximum AOF or IPR capability, the skin effect and flow capacity of a zone. Liquid influx can also be quantified.
Applications include pre-frac reservoir assessments, multiple-layer perforation inflow distribution diagnostics (PIDD), establishing initial reservoir pressures, evaluating moveable gas in shaley zones or very low permeability horizons (reserves additions), flowing or pumping oil well tests, closed chamber drillstem tests (CCDST), and surface casing vent tests. With some conventional flow &buildup tests and production history as background, PID response can be correlated to stabilized gas rates for instantaneous tie-in or frac decisions, a benefit to expedient shallow gas exploitation.
For all of these tests, data has been recorded in realtime at surface. Rigorous testing utilizes modern electronic surface data acquisition equipment and various software. A proprietary hardware &software system is also available. In it's simplest, most cost-effective and exploitive form, measurements with a hand-held pressure gauge are known to be 'good enough'.
Analytical theory for these tests is well documented. While the tests have been around for some time, the techniques are under-utilized in Western Canada.
The primary purpose of this paper is to illustrate various applications and usefulness of impulse testing with working field examples. Over the past several years the authors have experienced growth in the number of requests for these tests and success in their application in Western Canadian Sedimentary Basin gas fields.
Surging interest in impulse testing is due to technological advancements, present-day economics, modern business interests and changing strategies where exploitation has become a new Petroleum Engineering discipline.
Impulse testing has been around for some time and analytical theory is well documented. A comprehensive analytical process, however, does not presently exist. Hence, a secondary purpose of this paper is to bring together the various test types and references to illustrate the practicality of developing impulse analysis software. Better analytical tools are required to fully appreciate and maximize benefits of these quick, simple cost-effective techniques.
Over the past several years impulse testing applications have been expanding, concurrent with ever increasing gas development and primarily for by-passed pay evaluation.
Technological advancements with electronic surface data acquisition equipment (surface pressure recorders) has made impulse testing more practical. Surface recorders are now becoming commonplace tools for companies to access.
Advanced completion strategies and underbalanced perforating technology means that accurate and viable impulse data can be collected at surface.
Introduction of coiled tubing frac's has allowed companies to specifically target very thin low permeability streaks where an impulse test may provide the only feasible pre-frac assessment tool.
Lower and lower stabilized flow rates are a reality of present-day and future economics. As well, ultimate recoverable reserves are more important then ever to a companies net present value. Hence, companies are pursuing by-passed pay in very low permeability horizons.
