Method for predicting drillstring sticking

A method for predicting onset of drillstring sticking while drilling a borehole, comprising:

• (1) drilling a borehole from a first measured bit depth D.sub.1 to a second measured bit depth D.sub.2 ;
• (2) calculating a first borehole severity value, BHS.sub.1 for the drillstring at the first measured bit depth D.sub.1 ;
• (3) calculating a second borehole severity value, BHS.sub.2 for the drillstring at the second measured bit depth, D.sub.2 ;
• (4) calculating a first borehole severity slope value, BHSS.sub.1 for the difference in borehole severity relative to the difference in measured bit depth between D.sub.1 and D.sub.2, where:
• ##EQU5## (5) drilling the borehole from D.sub.2 to a third measured bit depth D.sub.3 ;
• (6) calculating a third borehole severity value, BHS.sub.3, for the drillstring at the third measured bit depth, D.sub.3 ;
• (7) calculating a second borehole severity slope value, BHSS.sub.2, for the difference in borehole severity relative to the difference in measured bit depth between D.sub.2 and D.sub.3, where;
• ##EQU6## (8) predicting onset of drillstring sticking based on the magnitude of the difference between BHSS.sub.2 and BHSS.sub.1 ;
• and
• (9taking remedial action to avoid sticking of the drillstring in the borehole, if drillstring sticking is predicted from step (8).

A method for predicting onset of drillstring sticking while drilling a borehole, consisting essentially of:

• (1) drilling a borehole from a first measured bit depth D.sub.1 to a second measured bit depth D.sub.2 ;
• (2) calculating a first borehole severity, BHS.sub.1 for the drillstring at the first measured bit depth D.sub.1 ;
• (3) calculating a second borehole severity value, BHS.sub.2 for the drillstring at the second measured bit depth, D.sub.2 ;
• (4) calculating a first borehole severity slope value, BHSS.sub.1 for the difference in borehole severity relative to the difference in measured bit depth between D.sub.1 and D.sub.2, where:
• ##EQU7## (5) comparing BHSS.sub.1 to a reference borehole severity slope value, BHSS.sub.0 ;
• (6) predicting onset of drillstring sticking based on the magnitude of the difference between BHSS.sub.1 and BHSS.sub.0 ;
• and
• (7) taking remedial action to avoid sticking of the drillstring in the borehole, if drillstring sticking is predicted from step (6).

A method for predicting onset of drillstring sticking while drilling a borehole, consisting essentially of:

• (1) drilling a borehole from a first measured bit depth D.sub.1 to a second measured bit depth D.sub.2 ;
• (2) calculating a first borehole severity value, BHS.sub.1 for the drillstring at a first measured bit depth D.sub.1 ;
• (3) calculating a second borehole severity value, BHS.sub.2 for the drillstring at a second measured bit depth, D.sub.2 ;
• (4) calculating a first borehole severity slope value, BHSS.sub.1 for the difference in borehole severity relative to the difference in measured bit depth between D.sub.1 and D.sub.2, where:
• ##EQU8## (5) drilling the borehole D.sub.2 to a third measured bit depth D.sub.3 ;
• (6calculating a third borehole severity value, BHS.sub.3, for the drillstring at a third measured bit depth, D.sub.3 ;
• (7calculating a second borehole severity slope value, BHSS.sub.2, for the difference in borehole severity relative to the difference in measured bit depth between D.sub.2 and D.sub.3, where;
• ##EQU9## (8predicting onset of drillstring sticking based on the magnitude of the difference between BHSS.sub.2 and BHSS.sub.1 ;
• and
• (9taking remedial action to avoid sticking of the drillstring in the borehole, if the drillstring sticking is predicted from step (8).