Increasingly crowded field, platforms and pads combined with tighter well spacing have led to an increase in the need for gyroscopic measurement systems that are not affected by the mass of steel surrounding them. Gyroscopic surveying tools have evolved from photomechanical to while drilling spinning mass technologies. This paper will highlight a new sophisticated but rugged type of gyro surveying system derived from solid state sensing technology. It will provide case studies as to the novel gyro systems accuracy when compared to other survey technologies such as conventional gyro or magnetic surveys.
Magnetic surveys accurately measure magnetism, they cannot however differentiate between the Earth's magnetic field and offset casing or other external magnetic sources. This means gyro technology is sometimes essential to safely and efficiently drill congested fields. The new gyro technology has been run in a large number of wells where it can be directly compared to either other gyro systems or magnetic surveys. All inclination and azimuth attitudes have been covered, with latitudes varying from the North Sea to central Asia. The solid state gyro system has been compared to all survey measurements in each of these wells. These comparisons will include analytics of positioning difference between surveying systems in both discreet and cumulative well placement terms.
The breadth and number of runs conducted with this new solid state gyro have shown that its accuracy is at least comparable if not superior to most current gyro technologies, while offering some considerable advantages. The gyro tools short survey cycle means multiple surveys are taken during one connection. This allows for trapped torque or pipe movement issues with the concurrent potential to reduce surveying time on a rig. This solid state gyro is non mechanical and robust requiring minimal calibration allowing for tools to be run from one job to the next without the need for tool returning to a calibration facility.
Rotating mass gyros have been the industry backbone for the last fifty years with important but evolutionary steps in terms of accuracy and robustness. Solid state gyros are far more robust while offering at least the same level of accuracy which is a step change for an industry that requires continuing increases in survey accuracy and wellbore positional assurance. The accuracy of other solid state systems which have been developed for mass market non-oil industry applications like smart phones has been limited. This solid state gyro system's unique gyro compassing methods have solved that problem, producing industry leading accuracy with the ruggedness required to last in the downhole environment.