Sand production is a serious problem in unconsolidated sandstone, it's becomes more critical as operators follow more aggressive production strategies. A successful sand control or management needed to evaluate sand production probability, to quantify risk reduction, and to establish practical operational scheme for safe and optimum production.
In this paper, focusing on the coupling between fluid flow and solid deformation, a consistent geometrical frame for sand prediction is established, which includes the capacity to predict sand production onset, sand quantities and sand production rates. Finite element method is used to solve the coupled governing equation system. Field data for sand production and enhanced oil production from Bohai Oilfield (Tianjin, China) were used to validate the model for the sand rate and sand production. Our studies indicate that the optimized pressure drawdown in unconsolidated sand be controlled by the following key physical parameters:
rock strength;
fluid viscosity;
pressure drawdown build-up strategy and pressure disturbance.
The simulation results relating cumulative sand production and sand production rate to these important variables are presented.
The study suggests that the proposed model may be used to generate quantitative information for predicting sand production and optimizing pressure drawdown. This provides a tool for sand-management in exploiting the weakness of sanding-prone scenarios.
Sand production occurs when the well fluid under high pumping rate dislodges a portion of the formation solids leading to a continuous flux of formation solids. Sand production compromises oil production; increases completion costs, and erodes casing, pipes and pumps or plugs the well if sufficient quantities are produced. Another important sanding process occurs in formation failure leading to the well bore instabilities, this is particularly serious for the unconsolidated sand reservoirs in Bohai oilfield (Tianjin, China). A high stress distribution, especially near a well and perforation tips, often induces local formation collapse. Such collapse region may spread with fluid flow and sand production process. These sanding effects are becoming more critical these days as operators are following more aggressive production schedules. However, the permeability in the wellbore vicinity is increased as a result of cleaning of formation sand. Sand production has been proven a most effective way to increase well productivity both in heavy oil and light oil reservoirs.
Because of the drawbacks of classical sand control techniques and the risks involved in uncontrolled sand production, Sand management has been operating in Bohai oilfield to optimized production rates and well productivity. Sanding prediction model predicts the production condition, e.g. pressure drawdown, at which sand production occurs and how much sand will be produced (rate and duration). It will be shown latter that, the pressure gradient variable takes as the important double roles in eroding formation matrix and dragging solid grains. At the same time, the fluid pressure can enhance solid matrix instability tendency. It is critical for sand management decision-making on whether or not sand control should be used, or when to use sand control.