Precipitation and dissolution of calcium phosphonates for the enhancement of squeeze lifetimes
- Univ. of Michigan, Ann Arbor, MI (United States)
Injection of scale inhibitors into a formation is a commonly used technique to prevent scale formation during oil production. The success of a squeeze treatment often is determined by its effective lifetime in inhibiting scale in a reservoir system, and this lifetime is dictated by the retention/release mechanism of inhibitor in the reservoir. This paper focuses on a study of the precipitation/dissolution of calcium 1-hydroxyethylidene-1, 1-diphosphonic acid (HEDP) in a porous medium to elucidate the important factors that affect the release of this precipitate. Experiments carried out in ceramic cores indicate that precipitation squeezes offer longer squeeze lifetimes and more HEDP retention than adsorption squeezes. Micromodel experiments show that the calcium-HEDP precipitate placed in porous media is made up of long, fibrous particles preferentially situated in pore throats. The elution from micromodels indicates that slow dissolution of apparently strong pore-throat plugs dictates the long tailing region. Finally, multiple-shut-in experiments performed in ceramic cores show that, while the amount of calcium-HEDP retention per shut-in does not increase with successive shut-ins, an enhanced returns effect is observed with respect to the squeeze lifetime.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC22-89BC14474
- OSTI ID:
- 87492
- Journal Information:
- SPE Production and Facilities, Journal Name: SPE Production and Facilities Journal Issue: 3 Vol. 10; ISSN 1064-668X; ISSN SPRFEZ
- Country of Publication:
- United States
- Language:
- English
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