Analysis Of Safe Mud Density Window In Deepwater Drilling

Drilling risks like borehole collapse,mud losses are frequently encountered if the drilling mud density is inappropriate in the process of deep water drilling,confirming the safety window of drilling mud density reasonably is greatly significant for ensuring safe drilling.The pore pressure,collapse pressure,leakage pressure and fracture pressure in deep water formations are the principal factors that affecting the safety window of drilling mud density.For the shallow strata of deep water formations,due to its poor lithology and loose soil,risks such as borehole collapse and mud losses are easily encountered,meanwhile in the deep strata of deep water formations,the fracture pressure is comparatively low,causing that the safety window of drilling mud density between the collapse pressure and fracture pressure is very small.This paper which is based on a deep water gas field in the south china sea,combining indoor rock mechanics experiments with logging data from the neighboring wells,establishes rock mechanics parameters and vertical profiles of formations strength.According to characteristics of the deep strata,the paper optimizes calculation methods of deep water collapse pressure and fracture pressure,and separately analyzes the pore pressure,collapse pressure,leakage pressure and fracture pressure in the shallow strata and deep strata of deep water formations,and confirms safety window of drilling mud density in the deep water drilling of target blocks with the principle of pressure constraint,which provides theory evidence for making sure the safety window of drilling mud density in the deep water drilling and designing the drilling projects.