Method and device for stabilizing well wall in fine managed pressure drilling

Abstract

The invention discloses a method and a device for stabilizing a well wall in fine managed pressure drilling. The method comprises the following steps: analyzing the collapse pressure and the leakage pressure of an easily-collapsing and easily-leaking stratum based on double-porosity elastic hypothesis; designing a proper bottom hole pressure value by comparing the porosity pressure, the collapse pressure and the leakage pressure of the stratum; monitoring an annulus pressure value in real time by using PWD (Pressure While Drilling) in the drilling and pump stopping processes and the processes of pulling out of a hole and running in the hole by combining a drilling fluid density value for circulating pressure loss design so as to ensure that the bottom hole pressure is basically consistent with the designed bottom hole pressure. In the drilling and pump stopping process and the processes of pulling out of a hole and running in the hole, the annulus pressure value is monitored in real time by using the PWD so as to ensure that the bottom hole pressure is basically consistent with the designed bottom hole pressure and no great fluctuation is generated and ensure the stability of the well wall in the drilling operation process. The method and the device disclosed by the invention can be used for keeping the well wall stable in the drilling process of an oil-gas well.

Description

technical field [0001] The present invention relates to a method for calculating the density of drilling fluid and a method for controlling the constant pressure at the bottom of a well to ensure the stability of the well wall in oil and natural gas drilling operations in complex formations that are prone to collapse and leakage, and in particular to a method for stabilizing the well wall in fine controlled pressure drilling And system, establish a system of precise control method of bottom hole pressure for safe drilling in easily collapsed and leaky formations, to ensure safe and fast drilling operations under the condition of narrow drilling fluid density window in complex formations. Background technique [0002] In petroleum engineering, elastic, poroelastic, plastic, and viscoelastic mechanics methods combined with strength criterion methods are widely used to explain wellbore collapse and fracture pressure. According to the rock constitutive relationship, the total st...

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Problems solved by technology

Therefore, when drilling in complex formations that are prone to collapse and leakage, wellbore loss may occur within a small range when the bottom hole pressure exceeds the formation pore pressure, and due to the high permeability and conductivity of formation fractures and the weakening of rock strength, Collapse pressure may also occur in a higher range, possibly even higher than the formation pore pressure, a phenomenon that narrows the permissible safe drilling fluid density window

However, in the conventional drilling process, the bottom hole pressure fluctuates in a large range, and it is very easy to cause drilling complications such as blowout, leakage, collapse, and sticking when drilling in such a narrow window formation.

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