Cost-effective vertical and fast drilling technology has been of great interest to drilling contractors of most oilfields, but it’s difficult to implement. Conventional anti-deviation drilling methods are of limited use when confronted with high-tilt angle geologic structure. Systems such as VDS, Power V and VertiTrak can be used to control the deviation angle of a vertical hole, but the rental costs associated with them are high, and sometimes, prohibitive. Therefore, there is great potential for developing a new anti-deviation technology that is cost-effective.

Slide steering BHA with two stabilizers and a bent PDM shows good anti-deviation effect when it is in rotary driven on the surface of low-dip wells. This working mode can be termed as coupled mode because the bit is driven by both PDM and rotary table/top drive equipment. The whirl feature of this kind of BHA can helps to eliminate the deviation force caused by the asymmetry point direction of bit axis. At the same time the lateral vibration of BHA introduces a large amount of anti-deviation force on the bit. Simulation results show that this kind of anti-deviation force 1)is much larger than that of the pendulum BHA in the same tilt angle hole, and 2) decreases with tilt angle of hole. The calculation model involved is illustrated later in the paper.

The method above has been validated through experiments and applications in Tuha oilfield. 12 vertical wells in easily deviated geological structures have been successfully drilled applying this technology. As a result, not only the deviation angle is controlled effectively, but also penetration rate improves significantly. In particular, drilling period is reduced by 9.26 days, a 25% reduction as compared to the whole working time needed when conventional method was used.

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