A Novel Technique to Control Sand Production from Mature Consolidated Sandstone Formation by Using Sodium Phosphate to Enhance the Formation Strength Conference Paper uri icon

abstract

  • Abstract It is known that sandstone formations often experience significant sand production when water saturation increases, especially in mature fields. Essentially, the amount of sanding mainly depends on the change in rock strength. Therefore, this paper examines the silica dissolution mechanism to establish a correlation between silica dissolution and rock strength as a function of water saturation. Additionally, the study explores the potential of sodium phosphate as an inhibitor to mitigate dissolution and enhance formation strength. A combination of static and dynamic experimental approaches was employed to establish a correlation between silica dissolution and rock strength as a function of water saturation. In the static approach, crushed core fine and coarse particles are utilized under different reservoir conditions to examine the silica dissolution. For the dynamic core flood test, silica dissolution was investigated as a function of water saturation in the presence and absence of sodium phosphate as an inhibitor to prevent dissolution. Then, core strength was recorded using unconfined compressive strength. Silica dissolution was detected by using a UV-Vis spectrophotometer. The results from the static experiments revealed that silica dissolution is mainly influenced by the pH and temperature of water. Additionally, water salinity impacts the amount of silica dissolved, indicating sodium chloride and potassium chloride have a higher effect on dissolution than magnesium chloride and calcium chloride. Moreover, fine particles have more dissolution compared to coarse particles. The core flooding test shows a clear relationship between increased water saturation and accelerated dissolution rate, consequently reducing core strength. Core strength decreased from 35.4 MPa (dry condition) as water saturation increased from 20% to 100%. This decrease was accompanied by an increase in silica dissolution. The reduction in core strength was consistent, reaching a maximum drop at 100 % water saturation, where it declined to 19.5 MPa, coinciding with the peak rate of silica dissolution, measured at 14 mg/l. Regarding the inhibitor effect, sodium phosphate notably suppresses silica dissolution, particularly at concentrations of 0.1 wt% and 1 wt%. This inhibition effectively maintains core strength near its original value. This study contributes novelty by understanding the main reasons contributing to sand production in mature, consolidated sandstone as water saturation increases. Additionally, it proposes an innovative approach to mitigate sand production by introducing an inhibitor (sodium phosphate) to control the reduction in sandstone strength through reducing silica dissolution.

publication date

  • 2025

start page

  • D031S044R001