The technical presentation “A New Micro-Resistivity Imaging LWD Sensor for Large Boreholes and Oil-Based Mud Is Instrumental in Formation Evaluation of Thinly Bedded Reservoirs” will be given by Jennifer Market from Well ID.
Abstract:
Thin beds often represent significant potential in oil and gas reservoirs but can be difficult to accurately analyse, particularly when the geology is complex, and thus reservoir calculations can overlook oil in place (OIP). Resistivity-based anisotropy methods are typically used to evaluate thin beds in regularly spaced fine laminations. However, for complex thin bed reservoirs, deconvolution based on borehole imaging is generally used in place of, or in conjunction with, resistivity methods due to the challenges of interpreting the complex resistivity log responses. Ideally, when economics allows, integrating electrical images with electrical anisotropy can improve the accuracy of the results.
In large boreholes (12¼” and above) with oil-based mud, there are wireline tool options but for operators that depend upon LWD solutions, there have been limited tools available. A recently introduced 9.5” LWD radar imager offers the possibility of borehole image-based thin bed analysis in large holes with oil-based mud.
The tool was used in a recent Norwegian offshore well drilled with oil-base mud and a 12 1/4” hole. A full suite of open-hole wireline logs was acquired along with the LWD radar imager. An in-depth analysis of the micro-electrical imaging data shows a strong correlation between the synthetic micro-resistivity measurement from the LWD radar image and the open-hole resistivity curves. The radar-based micro-resistivity curve was calibrated to account for mud effects and agrees well with the induction measurements. Due to the 1 cm vertical resolution and absence of polarization effects, the radar-based micro-resistivity can clearly identify thin beds hosting oil in place which are difficult to resolve with the resistivity logs.
By applying the Indonesia saturation equation, the image-aided processing yielded a several-fold increase in the volume of the oil-in-place as compared to the standard resistivity analysis.
Bio:
Jennifer Market is Chief Scientist for Well ID AS in Stavanger, Norway. She was the 65th president of the SPWLA and has served the society in many roles. Her expertise is in borehole acoustics, LWD imaging, MWD, geomechanics, pulsed neutron, and mining petrophysics. She has served as SPE & SPWLA distinguished speakers.