Study and Application of Stabilization and Differentiated Acidizing Stimulation System for Unconsolidated Sandstone Reservoirs

One of Middle East oilfield main production layers is a sandstone reservoir, primarily composed of sandstone and argillaceous siltstone. The rock is loose and prone to sand production. Conventional acidizing technologies are slow-acting and may even cause sand production. This paper analyze the mechanism of sand production and blockage in the reservoir, and develop a composite acidizing stimulation technology targeted at unconsolidated sandstone reservoirs. Based on the principle of "stabilization first, then stimulation," this technology can not only alleviate well blockage damage but also maintain reservoir stability. Through laboratory experiments, this paper developed a sandstone stabilizer suitable for high scouring flow rates. Under a flow rate of 1800 mL/h, the sand production rate can be stably controlled within 0.01%. Meanwhile, by applying the synergistic principle of different working fluid systems and aiming for "more scale removal, less sand dissolution," a differentially dissolving acidizing and descaling system was developed. Laboratory tests show that the dissolution rate of scale samples in the acid system is ≥95%, while the sand dissolution rate is <25%. The acid fluid can effectively alleviate the dissolution of sandstone minerals and maintain rock structure stability. Field tests have demonstrated that the composite acidizing technology, which follows the "stabilize first, then descale" approach, has increased average production and extended the treatment's effective period, effectively mitigating the problem of sand production in the reservoir. This provides a theoretical basis and practical direction for acidizing treatments in unconsolidated sandstone oilfields.