DEEP DIRECTIONAL ELECTROMAGNETIC MEASUREMENTS FOR OPTIMAL WELL PLACEMENT

The introduction of directional electromagnetic (EM) measurement technology while drilling is allowing well placement to be optimized by mapping distances to geological boundaries in real time. The field tests have shown that the technology can optimize well placement in reservoirs that would be challenging to develop with existing technology. In addition, the directional EM tool also enables improved characterization of resistivity and resistivity anisotropy in horizontal wells.

Existing technologies are often unable to meet measurement requirements for geosteering in thin, dipping, and curving targets with lateral resistivity variations. When it is critical to avoid excursions from these structures, interpretations that clearly indicate a steering direction and provide early warning are required. Field test results from Oman and the North Sea illustrate how the directional EM measurements fulfill these needs.

The directional EM measurements are more sensitive to approaching resistivity boundaries than existing propagation resistivity tools. Combining measurements from symmetrically arranged pairs of antennae further amplify this boundary effect while minimizing undesirable sensitivity to dip and anisotropy. This simplification of the tool response facilitates simultaneous interpretation of geometry and resistivity for application to both geosteering and formation evaluation. Novel data processing and structure visualization software was developed to aid the decision making and planning process.

In favorable conditions, in thick resistive beds, measurements are able to detect boundaries up to 15 ft away. In typical geosteering scenarios, sensing boundaries when they are still 10 ft away allows tens or hundreds of drilling feet to take a proactive steering decision to avoid unwanted structures.