Summary
This paper introduces a predictive tool that forecasts the drawdown associated with the onset of sanding as well as it predicts the sanding rate in real time. Experimental data on hollow cylinder samples (HCS) are used to support the validity of the numerical model.
Experiments on hollow-cylinder synthetic-sandstone specimens were conducted, involving real-time sand-production measurement under various conditions. A numerical approach was used for simulating the experimental results. The material behavior was simulated using an elastoplastic stress-strain relationship. The model simulated the interaction between fluid flow and mechanical deformation of the medium in predicting sand production. The model simulated strain softening of the material accompanied with shear-bands formation as well as tensile failure. In the post-disaggregation phase, additional features were considered, including allowing for the removal of the disaggregated elements that have satisfied the sanding criteria and, consequently, making the necessary adjustments to the size and properties of the domain under consideration. The model can be used for time-dependent analysis of wellbore stability as it undergoes disaggregation and sand production induced by depletion, drawdown, and water cut. Such numerical tools can be used in designing the completion by identifying the critical operational conditions associated with severe sanding over the lifetime of the wellbore.
The model showed a reasonable agreement with experimental results in terms of rock deformation and sanding rate. Further validation of the model against experimental and field data is necessary for its potential field applications.
Introduction
It is estimated that 70% of the total world's oil and gas reserves are found in poorly consolidated reservoirs (Bianco and Halleck 2001). Poorly consolidated formations are the most common solid producers. Several sand-production prediction methods have been proposed using geotechnical models. Existing models can effectively predict the onset of sand production and analyze cavity stability and rock failure; however, there still is room for improvement in predicting the volumetric sand production over the lifetime of the wellbore as a function of the completion strategy, drawdown, depletion, and water-cut.
In the following, a brief description of the existing models is introduced.
Modeling Strategies.
Several analytical and numerical models have been proposed for the prediction of sanding (Risnes et al. 1982; Perkins and Weingarten 1988; Sanfilippo et al. 1995; Vaziri et al. 1997; Vaziri and Palmer 1998; Morita and Fuh 1998). Most predict only the onset of sanding (Sanfilippo et al. 1995; Morita et al. 1989a; Morita et al. 1989b; Veeken et al. 1991; Weingarten and Perkins 1995; Kessler et al. 1993; Tronvoll and Halleck 1994; Wang and Dusseault 1996). There are only a few that give an indication of the severity of sanding (Papamichos and Malmanger 1999; Nouri et al. 2003; van den Hoek and Geilikman 2003). Some models view sand production as a mixed hydromechanical process (Papamichos and Malmanger 1999; Tronvoll et al. 1992; Tronvoll et al. 1997a; Tronvoll et al. 1997b; Charlez 1997). Some others base their sanding model solely on a cavity's mechanical stability (Antheunis et al. 1976a).