Coupled reservoir geomechanics with sand production to minimize the sanding risks in unconsolidated reservoirs

Abstract

Sand production in unconsolidated reservoirs has become a cause of concern for production engineers. Issues with sand production include increased wellbore instability and surface subsidence, plugging of production liners, and potential damage to surface facilities. A field case in southeast Iraq was conducted to predict the critical drawdown pressures ($\mathit{CDDP}$) at which the well can produce without sanding. A stress and sanding onset models were developed for Zubair reservoir. The results show that sanding risk occurs when rock strength is less than 7,250 psi, and the ratio of shear modulus to the bulk compressibility is less than 0.8 × 10¹² psi². As the rock strength is increased, the sand free drawdown and depletion becomes larger. The $\mathit{CDDP}$ of the upper and lower sand units are 3,900 and 5,400 psi at zero depletion rate, respectively. This indicates that the sanding risk may initiate earlier at the upper sand unit. The sanding potential occurs at the perforated interval within the upper sand unit when drawdown pressures reach 2,160 psi. The sensitivity analysis shows a wide range of $\mathit{CDDPs}$ when the uncertainty of rock strength is considered. This study will assist in optimizing the type of completion and minimize the sanding risk in unconsolidated reservoirs.

Keywords:

• critical drawdown pressure
• mechanical earth model
• reservoir geomechanics
• sand production
• sensitivity analysis