A safe casing operation method suitable for leaky formations

Abstract

The present invention provides a safe casing operation method suitable for leakage-prone formations. The operation method includes: selecting a suitable well depth range, running the casing, and reducing the drilling fluid density and density within the suitable well depth range through drilling fluid circulation. Viscosity and shear force; after the density and performance of the drilling fluid at the inlet and outlet within the appropriate well depth range are the same, continue to run the casing, calculate the maximum equivalent drilling fluid density of the easy leakage zone and the equivalent drilling fluid density of the easy leakage zone, and control the leakage The maximum equivalent drilling fluid density of the layer is not greater than the leakage equivalent drilling fluid density of the easy-to-lose layer, and the casing operation is carried out under fine pressure control in the annulus; the casing lowering speed is controlled, the drilling fluid density in the wellbore is adjusted to the actual required value, and the casing is lowered. pipe to the depth of the cementing well. The operation method of the present invention solves the technical problem of casing running under the condition of coexistence of blowout and leakage, accurately controls the pressure-bearing equivalent drilling fluid density of leaky formations, and lays a foundation for ensuring well control safety and cementing quality under complex geological conditions.

Description

technical field [0001] The invention belongs to the technical field of well cementing engineering in oil and gas fields, and more specifically relates to a safe casing operation method suitable for leakage-prone formations. Background technique [0002] High-pressure gas areas such as the Sichuan-Chongqing Basin and the Tarim piedmont structure have complex geological structures, large lateral differences in strata, many vertical oil and gas water leaks, and many pressure layers. The safe density window is only between 0.02 and 0.10g / cm3, which is a typical example. The narrow density window is easy to leak formation. In the process of cementing downhole casing, lost circulation is a common downhole complex situation under complex geological conditions. The consequences will not only prolong the drilling cycle, lose a lot of manpower and material resources, cause reservoir damage, but also directly lead to the failure of normal cementing operations. Seriously affect the qua...

AI Technical Summary

Problems solved by technology

However, under complex geological conditions, in deep wells that are prone to leakage and ultra-deep downhole casing operations, faced with special contradictions such as high well temperature and small annular space, the movement speed of the single control string in the original drilling fluid in the wellbore is not enough to meet the narrow safe density window. Job Requirements and Balanced Stress Guidelines

The BURKHARDT formula uses a graph in the calculation, but it is not enough for complex oil fields, and it may also cause human error in the mapping process

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