Method of Predicting Soil Mechanical Parameters in Shallow Formation While Jetting Process in Deepwater Drilling

The mechanical properties of shallow soils in deep water play an important role in drilling design and construction as well as later oil and gas development. Since it is difficult to collect soil samples from layers deeper than 10 meters below the sea floor, the acquisition of shallow soil mechanics, based on the variation of drilling parameters in the deepwater drilling process, is not only economical but also reliable. In this paper, we analyze the variation of subsea soil properties based on the variation of deepwater jet-drilling construction parameters, calculate the lateral friction resistance of conductor by use of WOB and displacement parameters in the jetting process, and determine the drilled formation's shear strength and internal friction angle in consideration of restored friction resistance. In order to verify the accuracy of the prediction-while-drilling model on seabed shallow soil mechanics, indoor unit and field simulation experiments were separately conducted. Moreover, the calculations from field application examples indicate that the prediction-while-drilling of deepwater seabed shallow soil mechanics achieves high conformity with the local practice results, which also indicates that this method could effectively guide field construction operations.