SMOOTH-DRILL: Elimination of Stick-Slip to Optimize Well Drilling Economics
Physical Sciences : Petroleum
Available for licensing
- Matthew Harris , Aerospace Engineering and Engineering Mechanics
- Behcet Acikmese , University of Washington
- Eric van Oort , Petroleum and Geosystems Engineering
In current drilling operations, the drill bit rotates in the hole to cut into the formation so that a reservoir can be reached and hydrocarbons produced. The bit is most effective when it rotates smoothly at a fixed rate. However, the heterogeneity of the subsurface formation and subsequent interactions with the bit make it difficult to control the drilling operation so that the drill bit always rotates smoothly.
A common effect of such interactions is stick-slip: the drill bit gets stuck, torques build in the pipe structure until the bit breaks free, the bit slips forward at a high rate releasing all of its rotational energy, shocks travel up the pipe harming the top drive system, the bit gets stuck again, and the process repeats itself. Consequences of the stick-slip phenomenon include bit damage, hole damage, damaged top drives, lost drilling time, and increased cost.
Researchers at The University of Texas at Austin have created a novel solution to the problem of stick-slip by enabling the drill bit to be actively controlled by the top drive system. With this control, the drill bit will rotate smoothly, eliminating the sticking, the resulting over-torque of the drill string, and the subsequent release and waste of energy, and thereby saving time and money. The control system allows for the top drive to stabilize the system, respects practical bounds on control torque magnitude, is robust, and does not require a human in the loop to modify gains. It can be implemented in real-time with guaranteed convergence whenever a model update is required.
- Does not require a human in the loop
- Solves the problem of stick-slip oscillations in drilling
- Systematic method for updating control gains
- Control bounds
- Strong numerical properties following from the linear matrix inequality formulation and interior point methods
Stick-slip vibrations can cause significant damage to the tools necessary for drilling procedures. Unmitigated vibrations give rise to large costs, constituting up to 10% of total well costs due to hindered efficiency, reduced wellbore quality, and increased need for maintenance. This invention could be critical to companies such as oil and gas service providers, as its implementation could significantly enable stick-slip vibration reduction and prolong the lifespan of drilling equipment.
Proof of concept
- 1 U.S. patent application filed