RIASSUNTO
Abstract
A major concern in the process of drilling is the high incidence and economic impact of lost time problems. In one study, it was shown that 75% of lost time incidents were associated with drilling mechanics problems. Obvious costs of poor drilling mechanics include lost rig time and damaged equipment. However hidden costs can add to this with low rate-of- penetration, more trips, lost-in-hole charges and increased service company charges.
Numerous technical papers in the past have documented specific drilling mechanics techniques. This paper summarizes the latest proven drilling mechanics techniques which have been applied to drilling operations to reduce these costs. The three major areas discussed are the following:
Stuck Pipe Prevention - Prevention of stuck pipe starts in the planning process where formation drillability is evaluated and borehole tortuosity is minimized. The operational phase of stuck pipe prevention involves continuous real time monitoring of drilling events, both for early detection of incipient sticking and to identify potential trouble spots while tripping.
Drillstring Failure Prevention - Shock and vibration often lead to extreme damage to drillstring and bit, broken downhole tools, and reduced rate-of-penetration. Mathematical models and surface measurements for failure prediction and detection have severe limitations. Downhole measurements of shock and vibration, in combination with surface measurements, can be used to determine which changes to drilling operational parameters can lead to the greatest reduction in downhole shock and vibrations.
Rate-of-Penetration Optimization - Using downhole drilling mechanics measurements, it is possible to increase weight transfer efficiency, reduce bit wear, optimize PDC bit performance. and improve PDM efficiency all leading to improved penetration rates and more favorable economics.
Each of these broad areas is illustrated with field examples.
DRILLING MECHANICS WORKSHOP
In February 1994, the first Drilling Mechanics Workshop was held by Anadrill for a group of oil company drilling superintendents. drilling engineers and petrophysicists with whom Anadrill had been working in an alliance type contract for MWD/LWD services. The emphasis of the contract was on continuous improvement. Drilling efficiency had improved on a number of rigs through application of practical solutions based on real-time measurements of drilling mechanics. What distinguished these rigs was good communication arid' teamwork between the drilling crew and the Anadrill field engineers who were trained in the principles of drilling mechanics. Management has observed these improvements and saw that it would be beneficial to document the process so that other crews could be trained to implement the ideas. The result was the Drilling Mechanics Workshop. Since then, workshops have been held around the world and have become part of the training program of Anadrill MWD engineers.
The training was not designed to replace conventional BHA design procedures such as BSR analysis, neutral point prediction, jar placement, or directional drilling considerations.
P. 855