Play and Prospect Assessment

The structural and stratigraphic framework, derived gross depositional environment maps and petroleum systems analysis and modelling feed into play assessment. Play assessment is static and reservoir-centric whereas petroleum systems analysis is process-based and source rock centric. Play assessment is an economically driven approach where the chance of success or failure is estimated at a regional scale and can be performed for both conventional and shale plays.

A full play assessment consists of the following steps:

• Synthesis of dry holes (well failure analysis)
• Mapping of shows (and absence of shows)
• Discoveries (economic and uneconomic)
• Fields (developed and producing, or appraised but undeveloped)

• Outline of the play fairway using GDE maps and petroleum systems analysis and modelling

• Creation of risk segments with a chance of success

• In convectional play analysis, mapping traps within the play fairway for future maturation into prospects

• Estimation of recoverable resources for an assessment unit (a play segment, an entire play or an entire basin)

Companies have different types of play chance matrix and associated terminology for the estimation of the risk, and the individual risk components depend on the play type (conventional or shale play) but generally includes reservoir (presence and deliverability), charge (source rock presence and effectiveness; charge access; hydrocarbon type) and seal (presence and effectiveness). It may include trap adequacy, preservation or other parameters for which economic failure can occur.

A play fairway assessment is a fundamental tool in exploration decision making as it helps in: (1) Detection of regional trends and sweet spot delineation; (2) Estimation of undiscovered overall play oil and gas volumes; (3) Ranking of basins and blocks; (4) Identification of uncertainty, value of new information, and attribution of work plan budget