Study On Calculation Method Of Underground Pressure Based On Temperature And Pressure

With the increasing demand for oil and gas resources, exploration and development has been rapid development in deep formation, thus deep well, ultra deep well drilling quantity soaring year by year. However, deep well and ultra deep well complex downhole accidents occurs frequently in the drilling process, especially in deep formation, such as drilling fluid out of control, severe leakage, gas invasion, and etc. And the relevant research shows that the inaccurate prediction of downhole pressure are the main causes of these complex downhole accidents. Therefore, based on the wellbore temperature field and stress field, drilling fluid rheology and density experiment of temperature and pressure is carried out. Then super deep well bottom-hole pressure calculation model is derived with consideration of high temperature and high pressure. This paper has carried out the following research work:(1) According to the law of thermodynamics and the principle of conservation of energy, drill string and annulus temperature field model during drilling fluid circulation is deduced. Combined with the western Sichuan region A well parameters, and annular drilling fluid temperature inside the drill string with well depth distribution are calculated with related calculation program.(2) Experimental research for polysulfide water-based drilling fluid system was carried out by drilling fluid rheological property of temperature and pressure, and regression analysis concluded that the drilling fluid system is in conformity with the Herschel-Bulkley model. Then the temperature and pressure drilling fluid rheological parameter model is obtained with the multivariate nonlinear regression method.(3) According to concentric annulus fluid laminar flow theory of fluctuating pressure, the Herschel-Bulkley concentric annulus laminar fluid circulation pressure new model is obtained. And field case calculation shows that the annular cyclic pressure drop is reduced with the increase of well depth.(4) Drilling fluid rheology, pump displacement, the annulus diameter ratio and the factors influencing the drilling speed and other circulating pressure loss was analyzed with the new model of annular cyclic pressure, and the results show that the drilling fluid rheological property, pump discharge and annulus diameter will have obvious effect on circulating pressure loss, and the penetration rate has little effect on circulating pressure.(5) According to the temperature and pressure experiment results of drilling fluid density, the prediction precision of drilling fluid density model is obtained considering of the influence of the temperature and pressure. Then computer program is used to the super deep well bottom-hole pressure calculation.Through the study of this article, super deep well bottom-hole pressure accurate calculation method of temperature and pressure is developed, which could creates a safe, rapid, efficient and economic conditions for the super deep well drilling, and will has important guiding significance and practical significance for the deep oil and gas exploration and development.