Integrated service companies have recently developed multi-component LWD resistivity logging tools. These new tools have multiple-component transmitters and receivers, and thus can provide directionality information useful in detecting physical parameters such as anisotropy, bed boundaries, formation dip, and formation azimuth. These new tools have found important applications in geosteering, and well placement operations. In this paper the authors will first review recent hardware and software progress of LWD directional resistivity tools, and then examine business impacts from using these directional LWD resistivity tools. We use synthetic and field data examples to illustrate the data processing flow and deliverables from each of these LWD tools. Topics to be discussed include a) the added value of these new tools, b) the effect of these tools on operational decisions, c) the challenges and issues encountered in applying these tools, and d) the way forward. Real data sets and feedback from well engineers, drilling engineers, geologists, petrophysicists, and reservoir engineers have been used to address the above questions.
Conventional wireline induction and LWD propagation resistivity tools measure formation resistivity using coaxial antennas, with their magnetic moments aligned along the borehole axis. These measurements are insensitive to azimuthal formation resistivity variations. In addition, the investigation depths from those conventional LWD resistivity tools are usually quite shallow, normally no more than a few feet. Due to this limitation, conventional LWD resistivity tools cannot provide effective formation evaluation and geosteering support because they are unable to detect anisotropy at low apparent dip angles or distinguish between bed boundaries approaching from above or below.
New generation LWD resistivity logging tools are equipped with tilted or transverse transmitters and/or receivers, and can thus provide information about directionality. The use of tilted antenna for formation evaluation started in the former Soviet Union (Korolev, Mechetin, 1990). Sato et al. (1994, 1996) have discussed a conceptual design of a tilted-coil resistivity logging tool. In their disclosure, they proposed to use three co-located tilted coils separated by 120º in the azimuthal direction to form three component transmitters and receivers. They discussed a possible application in induction logging using these tilted coils. Bittar (2000) filed a patent about a directional LWD resistivity tool with tilted antenna to detect anisotropy and formation dip. Clark et al. (2001) have documented a method of directional logging with a shield sloped slots. Hagiwara and Song proposed to use tilted coils in LWD resistivity logging in their patent filed in 2001 to detect bed boundaries and determine distance to bed boundaries in geosteering and well placement operations. Bittar also filed a patent on 2002 about a directional resistivity tool for geosteering applications. Hagiwara et al. (2003) have discussed mandrel effects on tilt-coil antennas. Fanini and Forgang (2004) patented an orthogonal coil design for induction and LWD tools. Gupta et al. (2005) filed a disclosure about time domain resistivity tool that may be used in geosteering operations.
The first directional LWD resistivity tool, PeriScope, was introduced into the market in 2005 by Schlumberger (Li et al., 2005).