| Popis: |
The Karachaganak field is giant oil and gas condensate reservoir. Data collected from numerous wells confirms it is very heterogeneous. Because conventional logs are not sufficient to fully characterize reservoir properties, new technologies and interpretation techniques are always considered worthy of a trial run when they become available in this remote region. In particular, the operator, KPO, is experiencing serious problems related to wellbore stability in deviated wells. Those problems occur mostly in the overburden and are related to uncertainty in stress direction and stress magnitudes. Excessive fluid losses while drilling are also a serious issue, and there is a need to identify fracture zones and understand fracture attributes. Finally, estimates of the extent of the formation damage zone (or radial extent of alteration in reservoir intervals) would provide useful information for the design of optimal well completions. Recently, a new advanced-technology, wireline acoustic scanning tool was run in a new well in the Karachaganak field to provide 3D formation acoustic properties from all borehole modes (monopole, dipole, and Stoneley) and measurements for near-wellbore and far-field slownesses. Drilling and completion engineers at KPO used the interpretation of this data to help make decisions and identify key geomechanical parameters required for successful operations. Mild stress-induced anisotropy zones were detected in the formation. Some zones of formation damage were identified by monopole and dipole radial variation profiling. Prominent open fractures were detected using shear dispersion analysis and Stoneley propagation – and confirmed by the electrical borehole images. KPO plans to use the acoustic anisotropy information to compute stress magnitude for new-well placement and mud-weight optimization, and for oriented perforation techniques to optimize hydraulic fracturing simulation. The estimation of radial formation alteration may help in designing optimal completions and identifying suitable depth intervals for fluid sampling. |
