High Resolution Visualization Of Near Wellbore Geology Using While-Drilling Electrical Images

Electrical borehole images offer a unique view of the subsurface to geologists and petrophysicists. Images from wireline electrical imaging tools are readily interpreted in terms of key geological characteristics such as structural and stratigraphical features of the formation. Today, advances in LWD technology allow high resolution electrical imaging to be successful in the water-based mud drilling environment. Key acquisition advantages for imaging whiledrilling include a better shaped borehole at the time of drilling and 100 % circumferential borehole coverage (unlike the pad coverage of wireline imagers). An important advantage in terms of application includes the opportunity for real-time decision making and related rig-time savings. Images sent to the surface - albeit optimized in definition given telemetry restrictions - give an early indication as to the angle of entry in to a given formation and allow for a more accurate/precise geosteering. We demonstrate field test results of a new high resolution while-drilling electrical borehole imaging tool and confirm its field worthiness as well as examples of the quality and accuracy of the images in conductive mud. In a series of controlled runs with its wireline counterpart and core, we have compared the response of the ?While-Drilling? tool. We show that the ?while-drilling? images are comparable to that of the wireline images. In addition, a greater understanding of the geological features is arguable because of the full circumferential coverage. Electrical images recorded while-drilling show clear occurrences of laminated and disturbed mud rock, cross-bedded and bioturbated sandstone, composite fractures as well as fracture swarms. This new LWD instrument is characterized through mathematical and experimental modeling. In a laboratory setup, we show the simulated logging of a set of artificial formations with known dipping interface, rugosity, fractures and different mud resistivities. Good agreement is obtained between the models and the electrical diameter for the LWD instrument is in-line with wireline electrical imaging tools. Electrical borehole images offer a unique view of the subsurface to geologists and petrophysicists. Images from wireline electrical imaging tools are readily interpreted in terms of key geological characteristics such as structural and stratigraphical features of the formation. Today, advances in LWD technology allow high resolution electrical imaging to be successful in the water-based mud drilling environment. Key acquisition advantages for imaging whiledrilling include a better shaped borehole at the time of drilling and 100 % circumferential borehole coverage (unlike the pad coverage of wireline imagers). An important advantage in terms of application includes the opportunity for real-time decision making and related rig-time savings. Images sent to the surface - albeit optimized in definition given telemetry restrictions - give an early indication as to the angle of entry in to a given formation and allow for a more accurate/precise geosteering. We demonstrate field test results of a new high resolution while-drilling electrical borehole imaging tool and confirm its field worthiness as well as examples of the quality and accuracy of the images in conductive mud. In a series of controlled runs with its wireline counterpart and core, we have compared the response of the ?While-Drilling? tool. We show that the ?while-drilling? images are comparable to that of the wireline images. In addition, a greater understanding of the geological features is arguable because of the full circumferential coverage. Electrical images recorded while-drilling show clear occurrences of laminated and disturbed mud rock, cross-bedded and bioturbated sandstone, composite fractures as well as fracture swarms. This new LWD instrument is characterized through mathematical and experimental modeli