--> ABSTRACT: Risk-Qualified Prediction of Gas Initial Potential and Production from Devonian Black Shales, West Virginia, by Michael Ed. Hohn; #91030 (2010)

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Risk-Qualified Prediction of Gas Initial Potential and Production from Devonian Black Shales, West Virginia

Michael Ed. Hohn

Initial potential and cumulative production figures from existing wells in a field are important for predicting production from a prospective gas well, particularly when geologic factors controlling production are poorly understood.

Evaluating probable success of a well involves more than simply drawing a contour map of initial potentials or cumulative production. Such data are subject to error and considerable variation over small distances. Estimates commonly deviate markedly from volumes observed after a well is drilled. A proper assessment of risk in drilling a well considers the range of likely outcomes. Nonparametric kriging estimates local frequency distributions from observed volumes, thus predicting the probability of a well coming in at a given volume, and the volume expected for a specific percentile such as the median.

Unfortunately, kriging smooths estimates such that the variance is less than that of observed values. To offset this smoothing, conditional simulation was used to obtain volumes that exhibit the same histogram and semivariogram as observed data. Simulation was carried out on Devonian shale production figures to generate possible outcomes at a number of sites. Most sites had about the same histogram of possible volumes, but the most favorable areas included rare, high-volume wells. The probability of offsetting a very good well with a second one of similar volume is much lower than suggested by conventional contour maps of gas volumes.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.