A Practical Approach to Gas Deliverability Predictions with the Use of an Electronic Digital Computer
- G.M. Chernoff (Alberta & Southern Gas Co. Ltd.)
- Document ID
- Petroleum Society of Canada
- Journal of Canadian Petroleum Technology
- Publication Date
- December 1963
- Document Type
- Journal Paper
- 178 - 181
- 1963. Petroleum Society of Canada
- 4.2 Pipelines, Flowlines and Risers, 5.6.4 Drillstem/Well Testing, 1.6 Drilling Operations, 4.6 Natural Gas, 4.1.2 Separation and Treating, 2.1.3 Sand/Solids Control, 4.1.5 Processing Equipment
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This paper presents a method of estimating the physical deliverability ofgas at the wellhead from depletion-type gas reservoirs, prior and subsequent tothe years of declining production. A prediction programme suitable for amedium-sized digital computer is given. It utilizes measured wellhead pressuredeliverability and absolute open flow potential curves for a field-averagewell. The predictions show the length of time a field is capable of deliveringa specified constant daily volume of gas. In addition, for each predictionperiod, the average reservoir and wellhead pressures, the average maximumproduction capacity, the QMax as determined by the Alberta Oil and GasConservation Board formula, and the cumulative gas volumes produced arecalculated. The programme also takes into account field compression and/or thedrilling of additional wells when required.
Reliable gas deliverability predictions are essential for economic forecastsof gas field performance. The calculation basically involves an adaption of thefamiliar equation in U.S.B.M. Monograph 7, relating flow rate toreservoir pressure. The equation only indicates a well's capacity to producegas at the reservoir sand-face. In actual practice, it is desirable to know thegas volumes a well is capable of delivering against a back pressure oftransmission lines, processing plants and field gathering lines. When the openflow equation is used for pipeline or wellhead deliverability calculations, itis necessary to calculate a relationship of Q versus flowing sand-facepressures for a constant-flowing wellhead pressure. As wellhead pressures areusually measured during back-pressure tests, these are used directly inplotting a wellhead deliverability curve, as described by Crawford (1).
For maximum reliability, the predictions for any field frequently must berevised as additional information and production history become available. Toperform the calculations by hand is an arduous task requiring considerable timespent on routine work. A medium-sized electronic computer is ideally suited forthis application, and, after the programme is written, long-rangedeliverability forecasts at various rates may be made in a matter ofminutes.
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