Forecasting Methods Of Pore Pressure While Drilling Formation

Drilling is that down hole drilling parameters are measured and tracked in underground. MWD has the advantage of being timely access to the most primitive strata drill. The drilled firsthand information that can help technicians to adjust construction program, and is also an important foundation for the development of oil and gas fields.Formation pressure is that pressure acting on the fluid within the pore space of the rock, also known as the pore fluid pressure. Under normal circumstances, the pore fluid pressure of a depth in the underground is equal to the hydrostatic pressure in the formation fluid, and this pressure is the pressure exerted by a hydrostatic column of formation fluid than the depth of the formation. Gradient pressure is that increased pressure with per unit increase of height. Under normal conditions of compaction, the pore fluid pressure is the hydrostatic pressure. However, due to many factors, the role of pore fluid pressure is rarely equal to the hydrostatic pressure. Usually the pore fluid pressure that deviated from the hydrostatic pressure is called abnormal formation pressure, or pressure abnormalities. However, Pore fluid pressure that is higher than normal formation pressure is called abnormally high pressure, and it that is lower than pressure below normal is called abnormally formation pressure. Formation pressure is abnormal formation pressure or abnormal formation pressure, often divided by formation pressure gradient. So higher than normal hydrostatic pressure gradient is high pressure abnormality, and lower than normal hydrostatic pressure gradient is low pressure anomaly.We do not expect that some abnormal pressure will produce down hole safety issues in the well, such as kick, blowout, wall collapse, stuck pipe and other issues. In drilling process we should understand the changes of pore pressure, and help prevent the occurrence of these problems and occurrence of complex situations to achieve safe drilling, which also contributes to the rationally used drilling fluid density, achieves balanced drilling, optimizes drilling parameters, and protects reservoir. Continuous formation pressure data can not only study distribution area of the formation pressure, and provide an important basis for the study of oil migration and oil-gas distribution.There are three conventional quantitative evaluation methods for MWD formation pressure prediction, such as dc index, dcp index, and index. This paper elaborated the three conventional methods systematically. From the point of practical engineering conditions of the three methods and their advantages and disadvantages, and then aiming at the limitations of dc index method, This paper discussed a new method of formation pore pressure prediction while drilling the rock strength method. Finally, from the perspective of practical application site, the paper combined with the current logging Liaohe actual hardware and software environment, and summarized the qualitative method of the logging data interpretation abnormal pore pressure, which instructed the engineers to systematically understand and explain LWD formation pressure prediction.