This paper elaborates the situation of development and application of high-density drilling fluids,analyze the technology and performance,discusses the reasons of downhole complications and reservoir protection technology,and points out the existing problems of current high-density drilling fluids and the development trend.

Application of numerical simulation of complex well based on hybrid PEBI grid;

A productivity prediction model for the complex well with formation damage;

On the complex drilling conditions,the cutting sample got in real time is hard to reflect the true formation,it is possible to make mistakes in establishing the formation lithology profile only by the cutting description.

Reliability analysis and risk assessment of casing in complex well status are the important research of applied theory and technology used for evaluating reliability, safety and prospective life of casing in complex well status including many risk factors, furthermore, preventing effectively casing failure, increasing casing reliability, lengthening casing life.