53rd U.S. Rock Mechanics/Geomechanics Symposium,
New York City, New York
2019. American Rock Mechanics Association
1 in the last 30 days
45 since 2007
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ABSTRACT: Carbonate reservoirs are characterized by extremely heterogeneity full of microcracks and vugs in it. It also presents anisotropic property of water filtration in terms of distribution of microcracks and void space. Incidents are common practice when drilling through carbonate formation such as loss circulation and borehole breakout. In drilling through fractured carbonate formation in North China, excessive volume of cavings accompanied significant volume of mud loss. To better understand the mechanism of this instability, both laboratory experiment and numerical simulation are conducted. The laboratory mechanical testing provides insight for the bearing capacity of carbonate rock and assists calibration for numerical modeling. Discrete element method (DEM) is used in this study to establish wellbore model. To characterize the anisotropy of pore space and microcracks, smooth-joint contact model is used. In addition, hydraulic flow in microcracks and matrix in the model is coupled with mechanical analysis. Discrete element-based hollow wellbore model is validated with analytical solution to gain reliability on the modelling. After running a specified time, the modeling results show that no fracture is induced in this incident, but significant mud loss is observed.
Carbonate reservoirs are known globally as an important source for hydrocarbon resources, and more recently as potential carbon dioxide storage sites. Carbonate reservoirs (limestone or dolomite) are made of materials such as shell or coral. These reservoirs are characterized by a matrix with a low permeability and heterogeneities such as fractures and voids. In the oil deposit exploitation, water injection method is widely used to balance reservoir pressure. When water is injected into reservoir in case of the lack of fracturing, the direction of injected water flows in the formation is determined by the direction of predominant rock pore channels. This anisotropy of filtrations along different directions is common in sedimentary rocks and occur in carbonate rocks as well (Kuzmin et al., 2011). The effect of anisotropy of filtration is always present and particularly revealed in large-pore and cavernous interlayers of carbonate rocks. This anisotropy is poorly studied due to the complexity of its evaluation.
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