Linking Geomechanics and Drilling Practices in Tight Carbonate Reservoir Using High-Resolution Caliper Data
Authors: Almasmoom Salahaldeen S. , Santoso Gagok I. , AlDaboos Mostafa H. 
Published: May 2023

The latest borehole ultrasonic and resistivity imaging technology in oil-based mud (OBM) environment enabled acquiring high-resolution image logs to ease identifying the several borehole breakouts and washed-out enlargements in a tight carbonate reservoir. However, the logs deliver limited information when correlating drilling practices to the resultant borehole shape and geomechanics stresses. This paper will link the different patterns which associate the tight carbonate rock geomechanics with the different drilling activities using both high-resolution ultrasonic image and caliper logs, and advanced drilling interpretation.

The recently developed logging-while-drilling (LWD) technology enables acquiring high-resolution borehole images for fracture interpretation. Furthermore, it also acquires high-resolution ultrasonic caliper log (180 sector resolution) of the drilled wellbore, painting a picture of the internal diameter of the drilled wellbore. When it comes to horizontal wells, the geomechanics evaluation of the drilled rock becomes more challenging; when correlating the lateral variations and laminations with the offset wells data evaluation. Therefore, the high-resolution ultrasonic caliper logs acquired while drilling the lateral sections through tight carbonate reservoir have been used to discern several wellbore enlargements. Those enlargements are linked with the several drilling activity patterns applied while drilling and tripping through the lateral section. Linking those drilling patterns with the resultant wellbore enlargements revealed several findings that can link the applied drilling practices with the rock geomechanics evaluation.

The real-time apparent resistivity images are used to pick formation dips and assist geo-steer through the target sweet spot while drilling the lateral section. Both ultrasonic and apparent resistivity images acquired in a recorded mode are used to interpret fractures, faults, cross-beddings, and secondary porosity intervals. The processed high-resolution caliper image logs (180 sectors) highlight the direct relationship among the drilling parameters applied while drilling, the resultant wellbore trajectory (the small changes in inclination and azimuth), and the resultant wellbore shapes (and in turn the tortuosity level in the wellbores). The processed logs are also used to estimate the effects of the different bottom-hole assembly (BHA) configurations on the wellbore shapes and tortuosity. The BHA configurations effects can be linked with the different applied drilling modes to also estimate the effects on the wellbore shape and tortuosity. Understanding the effects of the drilling processes allows differentiation between the drilling-induced shape artifacts and the geological causes for borehole tortuosity changes. Recommendations are gathered in an attempt to reduce wellbore damage associated with drilling and tripping activities as much as possible across the extended lateral section (wells converted to extended-reach wells).