Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.
This paper presents a technique which combines the Rawling and Schellhardt steady state back pressure equation and the standard pressure decline relationship of a gas reservoir to form a graphical display of a well's ability to produce against any one of a multitude of back pressures. This graphical display is constructed on an individual well basis and summarized to form a graph which represents the producing ability of a reservoir or group of reservoirs. This procedure is performed through the use of procedure is performed through the use of a Burroughs 5500 computer and the results are shown on graphs drawn by a Calcomp plotter. In addition to graphical plotter. In addition to graphical presentations, this information is also stored on presentations, this information is also stored on magnetic tapes which can be used in automated studies. The curves are designed to show deliverability and effective producing time as a function of cumulative producing time as a function of cumulative production against three specified back production against three specified back pressures. An interpolation technique is pressures. An interpolation technique is then employed which will allow any back Pressure between a minimum and maximum Pressure between a minimum and maximum to be utilized. The effective use of these curves will allow an engineer to immediately answer for management such questions as how much gas could a well, field, etc., deliver, assuming certain system requirements such as horsepower, etc., in a specified time interval selected by the user? By generating curves for all wells in a reservoir or field and knowing the appropriate allocation formula, we have investigated the future producing capabilities in light of current or producing capabilities in light of current or future regulatory limitations. By summation of the individual well results into curves representing a reservoir or groups of reservoirs, we make up a composite curve representing a field gathering system attached to our mainline pipeline. Utilizing these gathering system composite curves and an allocation procedure for scheduling gas volumes from procedure for scheduling gas volumes from the individual gathering systems, a total pipeline system availability study against pipeline system availability study against varying market conditions can be made for a specified time period.
It is obviously important for the management of any gas transmission company to have the facility to very quickly review their gas supply situation to maintain continuity with a changing market.