Well testing of low permeability gas formations generally concerns itself with acquiring quantitative information of a number of reservoir parameters including:

  • initial reservoir pressure

  • reservoir permeability

  • skin effects or damage

  • reservoir boundaries

  • propped fracture length

  • fracture conductivity

  • deliverability

These and other parameters are obtained from essentially the following three distinct types of pressure transient well tests:

  • drill stem tests

  • pre-frac tests

  • post-frac tests

These well tests involve both drawdown and buildup periods and the subsequent analysis is generally based on measured or derived bottomhole pressure data and surface flow rates. A great deal of literature has been written describing gas well testing and the various analytic techniques15 . Although the basic assumptions and limitations for each type of technique are described, the fact is that most of these assumptions or limitations are difficult, if not impossible, to adhere to, particularly in a field environment. Numerous authors68  have fixed upon certain of these fundamental assumptions and proceeded to suggest alternative methods or variations in the analytic technique that would tend to compensate for the discrepancies and thus decrease the induced error.

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