System and method for bayesian geosteering

Abstract

In some aspects, a computing device may obtain information relating to a location of a bottom hole assembly (BHA) in a wellbore. The computing device may generate a probability matrix responsive to the information, wherein the probability matrix comprises a plurality of probabilities each of which corresponds to a probability of the BHA's location relative to a geological formation. The computing device may determine, responsive to the probability matrix, a BHA location that has a highest probability. Numerous other aspects are described.

What is claimed is: 
     
         1 . A system for drilling a well, the system comprising:
 a processor;   a memory coupled to the processor, wherein the memory comprises instructions executable by the processor for:
 receiving first information related to a location of a bottom hole assembly (BHA) in a wellbore being drilled; 
 receiving second information related to a geological formation associated with the wellbore; 
 receiving updated information related to an updated location of the BHA in the wellbore; 
 responsive to the first information, the second information, and the updated information, generating a probability matrix comprising a plurality of probabilities, each of the probabilities corresponding to a probability that the updated location corresponds to a location relative to a geological formation; 
 responsive to the probability matrix, determining a most likely probability of the updated location of the BHA; 
 responsive to the most likely probability, determining if one or more drilling parameters are to be adjusted; and 
 sending one or more control signals to adjust the one or more drilling parameters determined to be adjusted. 
   
     
     
         2 . The system of  claim 1 , wherein the first information comprises measured depth, true vertical depth, or measurement while drilling information. 
     
     
         3 . The system of  claim 1 , wherein the second information comprises gamma log, resistivity log, neutron density log, or mechanical specific energy information. 
     
     
         4 . The system of  claim 1 , wherein the updated information comprises measured depth, true vertical depth, measurement while drilling information, gamma log, resistivity log, neutron density log, or mechanical specific energy information. 
     
     
         5 . The system of  claim 4 , wherein the second information comprises information from an offset well or from a portion of the wellbore that has already been drilled. 
     
     
         6 . The system of  claim 1 , wherein the instructions for generating a probability matrix comprise instructions for:
 assigning a probability that the updated information corresponds to each of a plurality of states.   
     
     
         7 . The system of  claim 1 , wherein the instructions further comprise instructions for:
 applying a Viterbi algorithm to the probability matrix to determine a likelihood of each of a plurality of states; and   generating a state likelihood matrix that comprises a likelihood of each of the plurality of states; and wherein the step of determining the most likely probability of the updated location of the BHA comprises determining which of a plurality of states has a highest likelihood.   
     
     
         8 . The system of  claim 7 , wherein the updated information comprises information related to the location of the BHA and information related to a geological formation in which the BHA is located. 
     
     
         9 . The system of  claim 8 , wherein each of the plurality of states corresponds to a location of the BHA relative to the geological formation in which the BHA is located. 
     
     
         10 . The system of  claim 9 , wherein the probability matrix comprises a Bayesian state space matrix or an emission matrix. 
     
     
         11 . The system of  claim 10 , wherein the instructions for generating a state likelihood matrix further comprise instructions for applying a transition function to the probability matrix, and wherein the state likelihood matrix comprises a plurality of transition probabilities, each corresponding to a probability that the BHA has transitioned from one state to another. 
     
     
         12 . The system of  claim 1 , further comprising instructions for controlling drilling by a drilling rig in accordance with the one or more control signals. 
     
     
         13 . A method for geosteering a well, the method comprising:
 obtaining information relating to a location of a bottom hole assembly (BHA) in a wellbore;   generating a probability matrix responsive to the information, wherein the probability matrix comprises a plurality of probabilities each of which corresponds to a probability of the location of the BHA relative to a geological formation; and   determining, responsive to the probability matrix, a particular BHA location that has a highest probability.   
     
     
         14 . The method of  claim 13 , wherein the step of generating a probability matrix comprises assigning a probability to each of a plurality of possible states, wherein each of the plurality of possible states corresponds to a possible location of the BHA relative to the geological formation. 
     
     
         15 . The method of  claim 14 , wherein the probability matrix comprises probabilities that a given set of measurements would be observed in a given candidate state. 
     
     
         16 . The method of  claim 13 , further comprising:
 applying a Viterbi algorithm to the probability matrix to determine a likelihood of each of a plurality of states; and   generating a state likelihood matrix that comprises a likelihood of each of the plurality of states, wherein the step of determining a most likely probability of an updated location of the BHA comprises determining which of a plurality of states has a highest likelihood.   
     
     
         17 . The method of  claim 14 , wherein the probability matrix comprises a Bayesian state space matrix or an emission matrix. 
     
     
         18 . The method of  claim 17 , wherein generating a probability matrix further comprises assigning a probability to each of a plurality of possible states responsive to an obtained information relating to the location of the BHA and to information relating to the geological formation. 
     
     
         19 . The method of  claim 18 , further comprising advancing the wellbore by a drilling rig responsive to the determining of the BHA location having the highest probability. 
     
     
         20 . The method of  claim 19 , wherein advancing the wellbore further comprises adjusting a direction of drilling or one or more drilling parameters responsive to the particular BHA location.