FIELD TEST RESULTS OF A NEW HIGH-RESOLUTION, DUALPHYSICS LOGGING-WHILE-DRILLING IMAGING TOOL IN OILBASE MUD
by Mathias Horstman, Schlumberger
was presented on Wednesday the 3 rd of October, 2018.
Borehole imaging while drilling is available since the first azimuthal tools were designed in the 1990s. In conductive muds, numerous image improvements (both in resolution and quality) have been made, particularly in micro-resistivity logging tools. The challenge to extend these capabilities to oil-base mud (OBM) has been addressed in a new tool designed to acquire high-resolution images logging-while-drilling (LWD). The data are maximized by a dual-physics technique using separate resistivity and ultrasonic imaging sensors.
The new tool introduces key design features that overcome the challenges associated with LWD imaging in oil-base mud. Sensors are positioned on the drill collar and high-resolution electromagnetic pulses are sent through the mud from the sensor to the formation at multiple frequencies (similar in principle to recently introduced wireline imaging tools for OBM). A novel processing algorithm combines the multiple individual frequencies to produce a robust image. A set of ultrasonic sensors is positioned close to the resistivity sensors on the tool collar. Focusing of the sensors and high-sampling rates deliver HD resolution comparable to wireline ultrasonic imaging tools. The multi-sensor design used for both measurement physics and their rapid firing and recording maximize full-borehole coverage in the majority of rotary drilling conditions.
An experimental version of the tool has been field tested in a broad variety of drilling and geological environments, also extensively in Norway. To date, over 45,000 ft of data have been acquired in wells ranging from vertical to horizontal. Data acquisition has been in clastics, carbonates, and evaporites having various formation properties. The field test data have confirmed the metrology of both physics types; i.e., resistivity and ultrasonic imaging. Examples are presented demonstrating the range of measurements under different borehole and geological conditions. Results to date have exceeded expectations in terms of imaging capabilities.
Mathias Horstman, CV
Mathias Horstman is principal domain petrophysicist with Schlumberger Norway, supporting both the reservoir characterization and drilling group in Scandinavia. After working for a period in the mining industry he joined Schlumberger in 2002 as a field engineer in Europe and Africa. He worked in management positions and held various petro-technical positions in log interpretation and geosteering in Europe and Asia. Mathias holds a master’s degree in geology from the University of Freiburg, Germany. He is currently president of the Norwegian Formation Evaluation Society (NFES), the Norwegian chapter of the Society of Petrophysicists and Well Log Analysts.