%0 Journal Article
%T Leak-Off Mechanism and Pressure Prediction for Shallow Sediments in Deepwater Drilling Leak-Off Mechanism and Pressure Prediction for Shallow Sediments in Deepwater Drilling
%A TAN Qiang
%A DENG Jingen
%A SUN Jin
%A LIU Wei
%A YU Baohua
%J 中国海洋大学学报（英文版）
%D 2018
%X Deepwater sediments are prone to loss circulation in drilling due to a low overburden gradient. How to predict the magnitude of leak-off pressure more accurately is an important issue in the protection of drilling safety and the reduction of drilling cost in deep water. Starting from the mechanical properties of a shallow formation and based on the basic theory of rock-soil mechanics, the stress distribution around a borehole was analyzed. It was found that the rock or soil on a borehole is in the plastic yield state before the effective tensile stress is generated, and the effective tangential and vertical stresses increase as the drilling fluid density increases; thus, tensile failure will not occur on the borehole wall. Based on the results of stress calculation, two mechanisms and leak-off pressure prediction models for shallow sediments in deepwater drilling were put forward, and the calculated values of these models were compared with the measured value of shallow leak-off pressure in actual drilling. The results show that the MHPS(minimum horizontal principle stress) model and the FIF(fracturing in formation) model can predict the lower and upper limits of leak-off pressure. The PLC(permeable lost circulation) model can comprehensively analyze the factors influencing permeable leakage and provide a theoretical basis for leak-off prevention and plugging in deepwater drilling
%U http://qdhb.cbpt.cnki.net/WKD/WebPublication/paperDigest.aspx?paperID=c7eecbca-7b1b-4a5f-a451-312da89e768a