A Novel Method of In-situ Drilling Well Caliper Prediction

In oil and gas drilling engineering, well caliper can reflect the state of downhole drilling operation, and even affect tool measurement and well trajectory control. Well caliper measurement is an essential link in drilling engineering. It is found that most of the existing well caliper measurement techniques are post-drilling measurement, so it is necessary to study in-situ drilling well caliper measurement method. In this paper, a new well caliper prediction model based on monitoring drilling mud density change is established. Taking the 215.9 mm borehole as an example, the simulation analysis shows that the model can be used to predict the hole size of ≥5% expansion rate of In-situ drilling when the drilling mud density is 1.0–2.5 g/cm3 and the drilling mud density monitor is equipped with the measurement accuracy of 0.001 g/cm3, and can even predict the hole size of 2% expansion rate in low drilling mud density conditions. Combined with the existing high precision drilling mud density monitor with measuring accuracy of 0.001 g/cm3, the new model can meet the requirements of In-situ drilling well caliper prediction, and has the advantages of low computational complexity and convenient application. It provides a reference for downhole drilling operation status monitoring and drilling tool steering control, and helps improve drilling quality and efficiency.