Estimating change in position of production tubing in a well

A method of characterizing a parameter relating to at least one fluid in a formation intersected by a borehole, the method comprising:

• taking a first gravity measurement in the borehole using a first gravimeter, the borehole containing a first reference feature;
• after taking the first gravity measurement, removing the first gravimeter and the first reference feature from the borehole;
• after removing the first gravimeter and the first reference feature from the borehole, positioning a second reference feature and a second gravimeter in the borehole;
• taking a second gravity measurement using the second gravimeter;
• estimating a difference in position between a position of the first reference feature during the first gravity measurement and a position of the second reference feature during the second gravity measurement using the first gravity measurement and the second gravity measurement;
• adjusting at least one additional gravimeter measurement in the borehole using to compensate for the estimated difference;
• and
• using the adjusted at least one additional gravimeter measurement to characterize the parameter.