Estimating velocities with uncertainty

Abstract

A method and apparatus for estimating velocity in a subsurface region. Seismic data for a subsurface region may be received. One or more attributes for the seismic data may be calculated. A posterior distribution may be generated. The posterior distribution may represent one or more probabilities of one or more velocities for the attributes. A velocity with uncertainty may be determined for the subsurface region based on the posterior distribution. A pore pressure with uncertainty may be determined based on the velocity with uncertainty.

What is claimed is: 
     
         1 . A computer system, comprising:
 a processor; and   a non-transitory memory including program instructions, which when executed by the processor, cause the computer system to:
 receive seismic data for a subsurface region; 
 perform a seismic waveform inversion for the seismic data; 
 generate a posterior distribution representing one or more probabilities of one or more velocities for the waveform inversion; 
 determine a velocity with uncertainty for the subsurface region based at least in part on the posterior distribution; 
 generate a dataset by combining the velocity with uncertainty with well log data; 
 determine a pore pressure with uncertainty based at least in part on the dataset; and 
 determine a minimum stress with uncertainty based at least in part on the dataset. 
   
     
     
         2 . The computer system of  claim 1 , wherein the program instructions executable by the processor to generate the posterior distribution comprises program instructions executable by the processor to:
 determine an uncertainty of the waveform inversion;   determine one or more parameters with uncertainty that describe the seismic waveform inversion;   receive modeling data for the subsurface region;   determine prior interval parameters distribution based on the modeling data;   determine a likelihood distribution representing one or more probabilities of one or more waveform inversions for each of the one or more velocities; and   multiply the prior interval parameters distribution by the likelihood distribution to generate the posterior distribution.   
     
     
         3 . The computer system of  claim 1 , wherein the program instructions executable by the processor to generate the posterior distribution further comprise program instructions executable by the processor to design a well based on the pore pressure with uncertainty and the minimum stress with uncertainty. 
     
     
         4 . The computer system of  claim 1 , wherein the program instructions executable by the processor to generate the posterior distribution further comprise program instructions executable by the processor to update the pore pressure with uncertainty and the minimum stress with uncertainty based at least in part on modeling data from a well. 
     
     
         5 . The computer system of  claim 4 , wherein the modeling data is obtained from an offset well. 
     
     
         6 . The computer system of  claim 4 , wherein the modeling data is obtained from a well while being drilled. 
     
     
         7 . A method, comprising:
 receiving seismic data for a subsurface region;   generating a pore pressure with uncertainty for at least part of the subsurface region, wherein the pore pressure with uncertainty is based at least in part from the seismic data;   generating a minimum stress with uncertainty for at least part of the subsurface region, wherein the minimum stress with uncertainty is based at least in part from the seismic data; and   updating at least one of the pore pressure with uncertainty and the minimum stress with uncertainty based at least in part on a set of well data.   
     
     
         8 . The method of  claim 7 , wherein the well data is obtained with a measuring while drilling tool. 
     
     
         9 . The method of  claim 7 , wherein the well data is obtained with a logging while drilling tool. 
     
     
         10 . The method of  claim 7 , further comprising designing a well based on the updated pore pressure with uncertainty or the updated minimum stress with uncertainty.