No abstract

Summary A 3D elasto‐plastic rate‐dependent model for rock mechanics is formulated and implemented into a Finite Element (FE) numerical code. The model is based on the approach proposed by Vermeer and Neher (A soft soil model that accounts for creep. In: Proceedings of the International Symposium “Beyond 2000 in Computational Geotechnics,” pages 249‐261, 1999). An original strain‐driven algorithm with an Inexact Newton iterative scheme is used to compute the state variables for a given strain increment.The model is validated against laboratory measurements, checked on a simplified test case, and used to simulate land subsidence due to groundwater and hydrocarbon production. The numerical results prove computationally effective and robust, thus allowing for the use of the model on real complex geological settings.

Summary Sand production is a critical issue in the oil and gas industry. During the production of a well, sand production may have negative consequences, such as risk of well failure, erosion of pipelines and surface facilities, and the need for sand separation and disposal. Knowing the conditions for the onset of sand production allows optimizing sand free production and, eventually, avoiding or delaying the use of sand-control methods. The aim of this work is to establish a reliable workflow for the estimation of the conditions for sand production in real field cases by means of finite-element modeling. The fundamental requirement is to set up a 3D coupled model that can be easily adjusted to the most complex conditions (e.g., stress anisotropy, deviated wells, and complex perforation patterns). The most suitable geometries and associated meshing strategies to describe the wellbore, the perforation tunnels, and the surrounding formation are analyzed. Further improvements with respect to previous approaches include the fact that the drilling and completion phases were also simulated to compute the correct stress distribution before the production, and that fluid flow and rock deformation are simulated in a fully coupled way to investigate accurately the effect of drawdown. Shear failure of reservoir rock, considered as an elastoplastic medium, is the main sand-production mechanisms analyzed, and the damage of the rock around the perforations is evaluated by analyzing the distribution of the equivalent plastic strain. Two real field cases are simulated, and the results of the finite-element models are consistent with the ones obtained by means of an analytical models and with field observations. Moreover, this numerical approach allows quantifying the spatial distribution and the severity of the damage of the rock around the perforations, facts that are either oversimplified or not considered at all in analytical models. For future applications, this model can be straightforwardly extended to more complex conditions and can also be improved to provide volumetric sand prediction.

No abstract

Sand production is a critical issue in Oil & Gas industry. During the production of a well, sand production may have negative consequences such as risk of well failure, erosion of pipelines and surface facilities and need for sand separation and disposal. Knowing the conditions for the onset of sand production allows optimizing sand free production and, eventually, avoiding or delaying the use of sand control methods. The aim of this work is to establish a reliable workflow for the estimation of the conditions for sand production, in real field cases, by means of Finite Element Modelling. With this respect, the fundamental requirement is to set-up a 3D coupled model that can be easily adjusted the most complex conditions (e.g. stress anisotropy, deviated wells, complex perforations patterns). The most suitable geometries and associated meshing strategies to describe the wellbore, the perforation tunnels and the surrounding formation are analyzed. The drilling and completion phases were also simulated to compute the correct stress distribution before the production. Fluid flow and rock deformation are simulated in a fully coupled way to investigate accurately the effect of drawdown. Shear failure of reservoir rock, considered as an elasto-plastic medium, is the main sand production mechanisms analyzed and the damage of the rock around the perforations is evaluated by analyzing the distribution of the equivalent plastic strain. A real field case is simulated and the results of the Finite Element model are consistent with the ones obtained by means of an analytical model and with field observations. Moreover, this numerical approach allows quantifying the spatial distribution and the severity of the damage of the rock around the perforations, facts that are either oversimplified or not considered at all in analytical models. For future applications, this model can be straightforwardly extended to more complex conditions and can also be improved to provide volumetric sand prediction. SPE 134464The common drawback of all these approaches is their cost and their negative impact on the productivity of a well: the correct assessment of the risk of sand production from a well can be a key factor in establishing the most profitable compromise between the maximization of the production and the control of costs for eventual sand management actions. Therefore, various approaches were proposed in literature to evaluate the eventual onset of sand production and, if possible, to quantify it. Available approachesPredicting the onset of sand production is a geomechanical issue that has been investigated for a long time (see e.g.[10], [19], [5] and [3], even if not an exhaustive list of the earlier works). The approaches developed throughout the years can be divided into three categories. The first class includes the development of methods based upon empirical relationships between the onset of sand production and some parameter that characterize either the mechanical properties of the rock (e.g. P-wave transit time [21] ) or the o...