Navigating and Imaging in Complex Geology with Azimuthal Propagation Resistivity while Drilling

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractReservoir navigation with LWD resistivity has traditionally relied on matching real time measurements with ideal logs. Reservoir navigation engineers initially build one or more resistivity models including all expected resistivity boundaries such as oil-water contact, reservoir to cap rock interface, faults and unconformities. Then, during drilling, they direct the well and update the earth model by matching actual measurements with forward response model data.Because common LWD resistivity sensors cannot differentiate between an oil-water contact approaching from below and a shale lens approaching from above or from the side, the reservoir navigation engineer fills in the missing information through expertise and local knowledge. In case of complex geology however, such as reservoirs with tilted or rotated fault blocks, multiple fluid contact levels, cross-stratification and shale intrusions, navigation becomes much more challenging and the risk of getting geologically lost is high. In recent years imaging LWD tools were introduced to help reduce the azimuthal uncertainty but they were limited to a few inches in lateral investigation.A new azimuthally sensitive propagation resistivity tool was recently tested for reservoir navigation and formation imaging in some of the more complex reservoirs of the North Sea. In cases where standard omni directional tool responses would lead to ambiguous interpretations, the azimuthally sensitive tool provided the basis for clear geosteering advice. A new imaging algorithm helped visualize approaching beds much like modern imaging devices, but with a depth of investigation reaching several feet into the formation. At fault crossings, the azimuthally sensitive signal helped recognize the relative movement of the formations on either side of the fault. In other instances where the well was run immediately below the cap rock, deep looking azimuthal propagation anticipated the intersection by several hundred feet. Also, analysis of the detailed deep electrical images brought a more complete understanding of the subsurface.

Boundary detection capability and influencing factors of electromagnetic resistivity while using drilling tools in a horizontal well

“…The axial transmitting and orthogonal receiving antenna is the basic antenna unit, which is used in instruments, such as AziTrak and VisiTrak (Bell et al, 2006;Rabinovich et al, 2011), as shown in Figure 1D. Using this antenna structure, the crosscoupled component signal V zx can be measured and the interface information can be directly reflected.…”

“…One type of electromagnetic boundary detection logging tool, Schlumberger's Periscope and Geosphere, uses a tilted antenna (Li et al, 2005;Omeragic et al, 2006;Antonsen et al, 2014;Seydoux et al, 2014;Zhu et al, 2021;Wu et al, 2022). The other type, by AziTrak and ViziTrak of Baker Hughes, uses an orthogonal antenna (Bell et al, 2006;Wang et al, 2007;Fang et al, 2008;Rabinovich et al, 2011). According to the detection range, EM boundary detection LWD tools can be divided into the azimuthal electromagnetic resistivity LWD tool (Hawkins et al, 2015) and the ultra-deep azimuthal electromagnetic resistivity LWD detection logging tool (Wu et al, 2019;Nemushchenko et al, 2022;Zhu et al, 2022).…”

The Importance of Extra-Deep Azimuthal Resistivity in Reservoir Development: An Update on Recent Field Experiences

“…A remote boundary introduces asymmetry in the Eddy currents and therefore a measurable signal in the receiver (e.g. Bell et al, 2006). Because of its geometry, this measurement is azimuthally sensitive.…”

Using Deep-Azimuthal Resistivity and 3D Seismic for Optimal Horizontal Well Placement: An Integrated Approach, Nipisi Field, Western Canada

“…For example, a 10 ohmm reservoir with a 1 ohmm shale boundary or underlain by a 1ohmm water zone, have the same contrast in resistivity with a 1000 ohmm reservoir with a 100 ohmm shale boundary. The tool's principle of operation is described in detail in [Bell et al, 2006]. During the well planning stage, it was thus necessary to determine if azimuthal resistivity would be effective in achieving the well objective.…”