The fact that triaxial/multi-component induction logging tools can detect different components of the induced magnetic fields has resulted in several important applications. The first application is the detection of resistivity anisotropy of the formation, which may lead to a better quantification of hydrocarbon in place and hydrocarbon recovery. This capability is important, for instance, in evaluating thinly laminated sand-shale sequences encountered in deepwater turbidites. Another important application of these new tools is formation dip and azimuth angle detection. Pad based dip meter tools have higher vertical resolution but much shallower depths of investigation. Thus dipmeter data are sensitive to near hole variations such as borehole rugosity and eccentricity. On the other hand, triaxial induction logging tools have deeper depths of investigation, and are thus less affected by near borehole variations such as rugosity. This is especially important in wells where image logs are either unavailable or unreliable. Careful analysis of the structural formation dip and azimuth angle information derived from triaxial induction logging tools together with dip-meter data may provide a better understanding of the subsurface architecture. Because of their ability to determine directionality, triaxial induction logging tools may also provide vital information about fracture orientation and lengths. Effort is being made to retrieve fracture information from these new induction logging data.
In this paper we first examine the similarities and differences on the hardware design, processing software, and field procedures of the two commercially available triaxial induction tools. We will also offer our perspective as an operator about triaxial induction logging tools and share the learnings from our operating units. We will specifically describe an offshore case study where we have run both types of tools back to back. We examine the performance of these two tools compare the field and processed results, and make recommendations and suggestions as how to best utilize these tools.
The first patent about the concept of triaxial induction logging tool was from Shell (Hungerford and Fay, 1957). It was filed as a dipmeter rather than an induction logging tool. Moran and Gianzero (1979) then published a paper on Geophysics to explore the theoretical aspect of triaxial induction logging. They found that the bottleneck for the triaxial tool to become a practical and useful tool would be the severe borehole effects on the transverse transmitters and receivers. A group of Shell researchers has proposed an idea for better saturation determination in thinly laminated sandshale reservoirs using triaxial induction logging data (de Waal et al., 1992). In 1993, Shell had teamed up with Baker Atlas to develop the first generation of multi-component induction logging tools. The tool was field tested in 1998 and now is officially named as 3DEXA. Initially, the 3DEX tool only output 5 components of the measured magnetic field (Kriegshauser et al. 2000). In 2004, the tool has been upgraded to output all 9 components of the magnetic tensor field. Schlumberger started their own triaxial induction logging program around the beginning of the century, and has developed a full tensor field triaxial array induction logging tool (Rosthal et al. 2003, Barber et al., 2004).
