新型PDC钻头设计(英)

新型PDC钻头设计(英)

时间:2008-12-30 振威石油网关注度：24129

简介：最近推出的新型PDC钻头，在质量上有了很大提高。主要介绍了史密斯钻头公司，Diamant Drilling Services等知名钻头公司推出的新型PDC钻头。

While roller cone bit technology still continues to make advances in insert shape, carbide composition and hydraulics design.

Roller cone and PDC bit design has progressed from its fundamental foundation laid nearly fifty years ago. Factors such as depth of cut, cone offset angle, cone geometry, journal angle, tooth/insert count and spacing are still a part of this foundation. Modern design, as shown by the new products presented in this article, focus on details such as bearing configuration, bottomhole coverage and inter-insert (teeth) clearance relative to adjacent cones. Modern design focuses on modeling cone tracking as a measure of bottomhole clearance. Bit designers rely not only on bit run simulations in a particular formation, some simulate the effect of the BHA on the particular bit to get a complete picture of forces affecting bit performance. As new bits are introduced, they are also accompanied by ancillary services such as custom designing each bit to a particular application. The following new designs show that this will be the continuing trend.

NEW TECHNOLOGY OVERVIEW

The following companies have released new technology within the past year.

United Diamond and Ulterra Drilling Technologies. The TorkBuster torsional impact generator from United Diamond and Ulterra Drilling Technologies enables PDC bits to drill tough formations by supplying impact energy. “When a PDC b it enters high-compressive strength formations, there is a possibility for stick-slip to occur. If insufficient torque is available to fail the formation, the drill string will wind up and store energy,” Rick Dudman, Downhole Tool Manager at Ulterra/United Diamond, explains. “Once the energy required to shear the formation is accumulated, the rock shears and triggers a violent release of stored energy that causes higher-than-normal impact loads on the PDC cutters. This will cause chipping and de-lamination of the diamond surface, eventually leading to a damaged bit and a shortened run.”

The impact generator applies a high-frequency torsional impact to the bit which, when combined with steady-state drillstring torque, results in an increase in horsepower directly at the bit. Run directly above a PDC, the impact generator is a short tool, Fig. 1. It has been run in directional wells below the motor in sliding mode and in vertical wells with high-performance motors.

Diamant Drilling Services. Diamant Drilling Services has developed a fixed cutter bit, which leaves the center of the hole uncut, Fig. 2. The lack of bit center leads to the creation of a core, Fig 3. This core is broken by the bit itself and ejected at the side through a slightly enlarged junk slot. The core is then carried to the surface along with the other cuttings. This process leads to high quality cuttings for surface examination. The improvement is especially important where normal cuttings quality is poor due to the use of turbines or high speed motors together with impregnated diamond bits.