Mechanism Study of Borehole Instability in Carbonate Reservoir through Discrete Element Modeling
Carbonate reservoirs are characterized by extremely heterogeneity having fissures and vugs in them. Incidents are common practice when drilling through carbonate formation such as the loss of circulation and borehole breakouts. In drilling through fractured carbonate formation in North China, excessive volume of cavings accompanied significant volume of the mud loss were observed. Numerous laboratory experiments and the numerical simulation are conducted to better understand the mechanism of this drilling instability. Microstructure analysis of outcrop carbonate rock showed weak inter-granular bonding and abundance of microcracks existed in carbonate rock. Mechanical testing had been also conducted to obtain mechanical properties of carbonate rock. Through our work, discrete element method (DEM)-based square-shaped hollow model was established to further investigate the mechanism of the drilling instability of carbonate rock. Our modeling results showed that fluid invasion played the main role in detachment of particles and particle erosion was accompanied with few shear-induced microcracks. The borehole breakout orientation was along the maximum horizontal principal stress direction. The influence of drilling mud density on instability patterns was further analyzed through our DEM modeling.
C. Zeng and W. Deng, "Mechanism Study of Borehole Instability in Carbonate Reservoir through Discrete Element Modeling," Geotechnical Special Publication, no. GSP 312, pp. 51-61, American Society of Civil Engineers (ASCE), Mar 2019.
The definitive version is available at https://doi.org/10.1061/9780784482148.006
8th International Conference on Case Histories in Geotechnical Engineering: Geoenvironmental Engineering and Sustainability, Geo-Congress 2019 (2019: Mar. 24-27, Philadelphia, PA)
Civil, Architectural and Environmental Engineering
Keywords and Phrases
Boreholes; Carbonates; Carbonation; Finite difference method; Infill drilling; Mechanical testing; Microcracks; Petroleum reservoirs; Pore pressure; Sedimentary rocks; Stability, Borehole instability; Carbonate formations; Discrete element modeling; Fractured carbonates; Laboratory experiments; Loss of circulations; Maximum horizontal principal stress; Microstructure analysis, Boring
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01 Mar 2019