Proper Core-Based Petrophysical Analysis Doubles Size of Ha'py Field

摘要

The Ha’py Field is located offshore Egypt and is part of thernPliocene producing trend north of the Nile Delta. The originalrninterpretation for the gas in place for the Ha’py Field byrnAmoco and others was 989 Bcf. Re-evaluation of the fieldrnincreased the gas in place to 2045 Bcf proven. Subsequentrnproduction in the field has substantiated the large increase ofrnthe gas in place as a result of the re-evaluation. The initialrnunderestimation of the gas in place was a result of the use ofrnan incorrect log-derived porosity model. This porosity modelrnis not compatible with the petrophysical water saturation relationshiprnused. The incompatibility stems from the fact thatrnpetroleum engineers and petrophysicists have different definitionsrnfor the terms effective porosity and total porosity. Therndifference in definitions may lead a petrophysicist to improperlyrnmodel the well logs to the available core analysis. In addition,rnthe engineer may mis-apply the petrophysicist’s resultsrnto the reservoir characterization. This improper applicationrnleads to a substantial underestimation of hydrocarbon porernvolume. The higher the clay and shale content in the reservoir,rnthe greater the error. Definitions will be clarified andrnexplained as they apply to core analysis, reservoir engineeringrnand petrophysics, along with examples using core analysis.rnCorrect modeling of porosity data in these shaly reservoirsrnlead to the increased estimation of the gas in place.