The NET-PAY method predicts pay thickness away from wells using seismic elastic impedance data created by SIP Reservoir Services. SIP offers three approaches: De-Tuning (Connolly), Threshold, and Gaussian. Which method is used depends on the input data and the types of outputs required.
De-tuning prevents significant impedance values due to thin layers being erroneously interpreted as Net Pay. The example below shows Net Pay maps created from average band limited impedance data and using SIP Net. Notice how tuning results in brigth amplitudes giving a superficial Net Pay response. In contrast, SIP Net Pay removes the effect of tuning and shows pay is much thinner.
Fig 1: SIP Net Pay avoids erroneous pay estimates due to thinning.
De-tuning and Threshold methods give similar results. However, using an Elastic Impedance seismic volume (Fig 2) as input to the Threshold approach we are able to create a volume of Net Pay (Fig 3). This Net-Pay volume is useful for input to reservoir simulation and geo-visualisation.
Fig 2: Elastic Impedance volume over reservoir
Fig 3: Net Pay volume after application of Threshold method
The Gaussian method allows us to determine the uncertainty or risk associated with the pay prediction. So for example, you may want the probability of Net-Pay with 50% confidence of being between 50-120 feet thick. The Gaussian method predicts most likely Net-Pay and probability of Net-Pay. These criteria are extremely valuable in understanding the drill risk analysis.