Changes

==Accuracy levels in geotechnical predictions==

==Accuracy levels in geotechnical predictions==

Geologists, geophysicists, and engineers think they are much more accurate than they really are. In exploration forecasting, a goal of 0.5× to 2× for area of accumulation, net pay, and hydrocarbon recovery factor is about as accurate as nature will allow us to estimate. In other words, 80% of our predictions should be within an envelope of one-half to twice that of reality. Reserves predictions may vary more because of the multiplicity effect; perhaps 0.2× to 5× is a more reasonable range to expect here. Such variances can be portrayed on log probability paper.

Geologists, geophysicists, and engineers think they are much more accurate than they really are. In exploration forecasting, a goal of 0.5× to 2× for area of [[accumulation]], net pay, and hydrocarbon recovery factor is about as accurate as nature will allow us to estimate. In other words, 80% of our predictions should be within an envelope of one-half to twice that of reality. Reserves predictions may vary more because of the multiplicity effect; perhaps 0.2× to 5× is a more reasonable range to expect here. Such variances can be portrayed on log probability paper.

Geologists working on development projects should do somewhat better than this, however, and perhaps a general range of 0.8× to 1.25× of actuality is expectable for predictions based on geological parameters and reservoir performance. Correspondingly, reserves predictions should fall within the 0.67× to 1.5× envelope for development wells, at the 80% confidence level.

Geologists working on development projects should do somewhat better than this, however, and perhaps a general range of 0.8× to 1.25× of actuality is expectable for predictions based on geological parameters and reservoir performance. Correspondingly, reserves predictions should fall within the 0.67× to 1.5× envelope for development wells, at the 80% confidence level.