Well bore structure for out-of-round oversized hole

Abstract

The invention discloses a well bore structure for an out-of-round oversized hole. The well bore structure comprises N well opening layer sections, wherein a first well opening casing pipe to an Nth well opening casing pipe are arranged in the first well opening layer section to the Nth well opening layer section in a lowered mode respectively, the Mth well opening layer section is provided with anout-of-round oversized complex layer section, N is a positive integer larger than or equal to two, and M is a positive integer larger than or equal to two and smaller than or equal to the N; a section of first hole reaming well wall is arranged below the out-of-round oversized complex layer section, one expansion pipe is arranged at the position of the out-of-round oversized complex layer sectionin a sleeved mode, and the inner drift diameter of the expanded expansion pipe is larger than the hole diameter of the Mth well opening layer section and smaller than the inner diameter of the M-1thwell opening casing pipe; and the upper end of the expansion pipe is located above the out-of-round oversized complex layer section, and the lower end of the expansion pipe is located below the out-of-round oversized complex layer section. According to the well bore structure, under the condition that the well bore structure on the upper portion is fixed, the out-of-round oversized complex layer section can be effectively packed under the principle that the hole size is not lost, and therefore continuous safe drilling is achieved.

Description

technical field [0001] The invention relates to the technical field of processing downhole collapsed complex formations, in particular to a wellbore structure for a wellbore with a belly. Background technique [0002] With the continuous vigorous development of oil and gas resources, the center of gravity of drilling has gradually shifted to deep reservoirs with large burial depth, complex formation pressure and unclear geological conditions. Especially in the process of exploring new blocks, it is particularly difficult to drill risky wells. Relatively low, difficult to meet the reasonable determination of drilling fluid density in engineering, improper use of drilling fluid density, very prone to complex downhole accidents such as well wall collapse. [0003] Slight downhole collapse is very common. In general, the usual way to deal with minor downhole collapse is to optimize the drilling fluid system, increase the drilling fluid density and shear force, and add anti-slump...

AI Technical Summary

Problems solved by technology

[0010] For the above-mentioned situation where the well wall collapse is very serious and there is a partial belly, it is impossible to predict and know before the actual drilling. At this time, the well diameter may reach 2 to 3 times the designed drill bit size, or even larger, which often causes The accumulation of collapsed objects and cuttings, among which the fallen pieces are relatively large, cannot continue to drill safely, resulting in frequent occurrence of pump and top drive suffocation

If the above-mentioned increase in drilling fluid displacement is still adopted, and heavy mud is used to lift sand to send the bottom block to the wellhead, due to the large friction with the rotating drill string during the return process of the large block, it is easy to cause drill string damage. Partial damage leads to stress concentration. In this suffocating situation, forcibly lifting up and down, the damaged drill string is prone to accidents such as broken drilling tools, which will greatly affect the drilling operation in terms of time, economy, risk, Or there is a heavy blow to the efficiency

[0011] In view of the above situation, in the prior art, casings of different sizes are also used to seal the formation layer by layer to permanently seal the complex section 04 of the big belly, but this will temporarily increase the casing layers and change the original wellbore. Structural design, going to other sites to call new casings and changing the casing layer requires a complicated approval process, which will delay more time, affect work efficiency, and increase cost budget; on the other hand, with the increase of drilling depth, With the increase of casing layers, if the opening size (that is, the diameter of the first wellbore) in the wellbore structure is fixed, the final wellbore diameter will be smaller, which may lead to failure to drill to the target layer, even if the target layer is drilled , but the wellbore size is too small to meet the wellbore size requirements of the fracturing stimulation tools in the subsequent well completion operations

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