Abstract
To overcome the drawbacks of conventional squeeze treatment, such as short lifetime and high initial concentration spike, a new metal phosphonate solid inhibitor has been synthesized and its long-term squeeze performance in different formations has been demonstrated. A combination of cations (Ca, Mg, Zr) and anions (citrate, DTPMP) are used to synthesize the metal phosphonate colloidal inhibitors with high product yield. Compared with amorphous metal phosphonate synthesized by direct precipitation, the solubility of this new metal phosphonate colloidal inhibitor is at least one order of magnitude lower. The proposed mechanism is that due to the formation of metal citrate complex, the initial free cation concentration is low so that the low solubility crystalline metal phosphonate product is formed. This colloidal inhibitor shows good permeability through sand packed columns. Laboratoy squeeze simulation shows low initial inhibitor return percentage and long lifetime of squeeze treatment in different rock formations. The colloidal inhibitor formula can be tailored to different minimum inhibitor concentrations (MIC) to protect the oil wells of different scaling risks. This new colloidal inhibitor will have significant implications in long-term squeeze treatment to lower the cost of overall downhole scale treatment.
