| Popis: |
In the quest to develop shale gas reservoirs, horizontal wells have emerged as the most prolific producers with lateral sections ranging from 3,000 ft to more than 10,000 ft in length in some plays. Even with substantial experience in planning and drilling in shale, borehole stability problems while drilling continue to occur, resulting in increased operating time and costs. Adding logging-while-drilling (LWD) tools to the drilling program can assist with identifying and mitigating such problems by providing valuable information on the condition of the wellbore. These measurements include ultrasonic and azimuthal calipers computed from density and photoelectric factor measurements. In this case study, time-lapse evaluation of these logs by logging on a trip out of the well revealed the presence of breakouts within the borehole and evidence of deterioration of borehole quality with time. Caliper measurements were integrated with other logs and regional tectonic information to construct a Mechanical Earth Model (MEM). The MEM consisted of estimates of rock mechanical properties, formation pressure, and in situ stresses. Using this data, a wellbore stability model was developed. The model provided insights into the stress regime and the mechanism of borehole failure. Drilling procedures to mitigate borehole breakout were consequently developed, thereby improving the efficiency of subsequent drilling in the same area. |
