Bit and bottomhole assembly (BHA) dynamics are a challenge when drilling in hard and interbedded formations. Dynamic conditions such as stick-slip and whirl can limit performance or in the worst case destroy downhole components. A new percussive mud hammer motor is being implemented in China to improve drilling performance by imparting a controlled impact to the bit while drilling.
Conventional technologies to address these challenges may have limited improvement significant added costs:
Conventional motors can generate large amounts of torque to the bit but can be difficult to control tool face and depth of cut as the bit transitions through various formations. This can result in stick-slip and bit bounce that can quickly damage or destroy the bit and BHA.
Rotary steerable systems can control downhole dynamics with complex electronic, hydraulic and mechanical components but are very expensive, require higher system pressures and on-site supervision.
Turbines with impregnated diamond bits can provide smooth drilling but can have limited rates of penetration in the softer portions of interbedded formations. In operation they also require higher pressure drops, have limited build rates and require on-site supervision by a turbine technician.
These conventional system limitations created an opportunity for a new technology that is simpler and brings greater value to the drilling operation. The hammer motor is a conventional power section and drivetrain with the patent pending hammer mechanism fitted in place of the lower bearing. This assembly has the same geometry of a bent housing motor with all of its capability plus the impact of a rotary hammer.
A series of field trials in China have recently been performed to validate the performance increases created by the hammer motor. These trials demonstrated significant cost savings, improved drilling performance, and simplicity of operation.