Method for determining drilling fluid density in salt-gypsum layer deflection

Abstract

The invention relates to a drilling technology in the field of petroleum exploration and development, in particular to a method for determining drilling fluid density in salt-gypsum layer deflection. The method for determining drilling fluid density in salt-gypsum layer deflection comprises the following steps of: (1) establishing a salt-gypsum layer creep model under the variable-curvature and variable-azimuth conditions; (2) according to the salt-gypsum layer creep model, establishing a salt-gypsum layer borehole wall deformation model under the conditions of drilling fluid density, borehole curvature and borehole azimuth; (3) establishing a relationship chart of the drilling fluid density, borehole curvature and borehole azimuth; and (4) according to the relationship chart established in the step (3), determining the reasonable drilling fluid density. By using the method provided by the invention, the appropriate drilling fluid density, deflection azimuth and deflection curvature can be preferably selected, thereby reducing the drilling fluid density to satisfy the minimum burst pressure of the stratum, effectively preventing borehole undergauge and avoiding complex downhole circumstances.

Description

technical field [0001] The invention relates to drilling technology in the field of petroleum exploration and development, in particular to a method for determining the density of drilling fluid for deflection in salt-gypsum layers. Background technique [0002] The formation of deep oil and gas reservoirs in many petroleum-bearing basins in the world is related to gypsum-salt layers, and the number of oil and gas reservoirs developed under gypsum-salt layers is relatively large, which will be the focus of deep oil and gas exploration in the future. In the process of oil drilling, sub-salt horizontal wells drill deep salt layers and there are weak formations between the salts, the formation pressure bearing capacity is limited, and lost circulation is prone to occur; the performance of high-density drilling fluid in the deflection section seriously restricts the effectiveness of downhole directional tools At the same time, the wellbore trajectory also has a great influence o...

AI Technical Summary

Problems solved by technology

In the process of oil drilling, sub-salt horizontal wells drill deep salt layers and there are weak formations between the salts, the formation pressure bearing capacity is limited, and lost circulation is prone to occur; the performance of high-density drilling fluid in the deflection section seriously restricts the effectiveness of downhole directional tools At the same time, the wellbore trajectory also has a great influence on the drilling fluid density

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