Eccentric split type PDC bit

Abstract

The invention provides an eccentric split type PDC bit. The geometrical shape of the eccentric split type PDC bit is determined by four parameters including the drilled well hole diameter D being 2Lad, the to-be-drilled well hole diameter N being equal to 2Lbd and 2Lbc, the guide eye diameter P being equal to 2Lav and the half angle corresponding to the reaming curvature, and the half angle is thehalf angle phi of a wing angle, wherein the Lad represents the drilled well hole radius, the Lbd represents the to-be-drilled well hole radius, the Lbc represents another form of the to-be-drilled well hole radius, and the Lav represents the guide hole radius; and the eccentric split type PDC bit adopts a double-core structure, the drill has two central axes including the reaming central axis andthe to-be-reamed central axis, and the distance between the two centers is the eccentricity. According to the design method of the double-core bit, the relevant dimensions are characterized in that the nominal size of the bit is phi215. 9, and the deviation value between the rotation axis of the bit and the axis of a drill column is 4 mm; a cutting part of the eccentric split PDC bit is made intotwo concentric unequal-radius sections, the small radius is 105.9 mm, the large radius is 110 mm, and when the bit rotates, the unequal-radius sections can form a well hole larger than phi220 in thebit rotating process.

Description

technical field [0001] The invention relates to the technical field of a PDC drill bit, in particular to an eccentric split-type PDC drill bit. Background technique [0002] Since the PDC bit was used in the 1980s, due to its unique shearing and rock-breaking method, it has high mechanical penetration rate and long service life in drilling soft to medium-hard homogeneous sand and mudstone formations, and has become the main drill bit for oil and gas drilling. At the same time, with the continuous development of drill design technology, diamond superhard material technology and manufacturing and processing technology, the application range of PDC drill bits is becoming wider and wider. [0003] In some specially developed rock formations, there are large sections of salt rock, oil-soaked mudstone, and short rhythmic layers composed of mudstone. When drilling into such formations with roller cone bits or conventional PDC bits, diameter shrinkage and pipe sticking accidents wil...

AI Technical Summary

Problems solved by technology

This method has a long drilling cycle and does not fundamentally solve the problem of rock sticking; (2) increasing the density of the drilling fluid will increase the hydrostatic pressure of the drilling fluid on the formation. The pressure difference can prevent salt creep, but it needs to be drilled Longer casing strings to isolate leaky formations above salt formations and increased drilling costs due to limited drilling fluid density increases due to drilling pump capabilities

(3) Double-core drill bits are used to cope with the shrinkage of salt layers. This technology is effective in overcoming the problems of diameter shrinkage and drill sticking in migrating salt formations. widely used

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