Abstract
One of the most common methods of preventing downhole and topside mineral scale formation in oilfields is through the use of chemical scale inhibitors. Several aspects of the brine composition may affect the performance of the various scale inhibitors used in oilfield applications. In this paper, we focus on the influence of divalent cations such as calcium and magnesium. The concentration of such divalent cations is shown to effect the barium sulphate inhibition efficiency of generically different species of scale inhibitors by varying degrees, and in different directions. In previous work, the effect of calcium cations on the performance of various inhibitor species was demonstrated. In this paper, these observations are extended to include the effects of the magnesium cations in solution.
The influence of divalent cations such as Ca2+ and Mg2+ on the barium sulphate inhibition efficiency of generically different inhibitor species has been examined here in a variety of brine systems including low scaling “Brent type” and medium scaling “Forties type” brines. In addition, low salinity “ideal” brine systems have also been examined. The scale inhibitors studied include: penta-phosphonate (DETPMP), hexa-phosphonate (TETHMP), phosphino-poly carboxylate (PPCA) and poly-vinyl sulphonate (PVS). Results are presented from a series of static barium sulphate inhibition efficiency tests conducted at 95°C over 2 and 22 hour residence times.
The results presented here demonstrate how phosphonate inhibitors are significantly improved in the presence of [Ca2+] and also that their effectiveness is considerably reduced, or poisoned by increased [Mg2+]. The performance of the phosphonate species are shown to be controlled by the performance of inhibitor/Ca2+ complexes, whereas the formation of inhibitor/Mg2+ complexes effectively poisons the phosphonate species ability to inhibit. The polymeric species (PPCA and PVS) are shown to be less influenced by increased [Mg2+]; indeed, marginally improved performance is obtained. This paper significantly extends the findings reported previously in SPE 3727.
The influence of divalent cations such as Ca2+ and Mg2+ on the barium sulphate inhibition efficiency of generically different inhibitor species has been examined here in a variety of brine systems including low scaling “Brent type” and medium scaling “Forties type” brines. In addition, low salinity “ideal” brine systems have also been examined. The scale inhibitors studied include: penta-phosphonate (DETPMP), hexa-phosphonate (TETHMP), phosphino-poly carboxylate (PPCA) and poly-vinyl sulphonate (PVS). Results are presented from a series of static barium sulphate inhibition efficiency tests conducted at 95°C over 2 and 22 hour residence times.
The results presented here demonstrate how phosphonate inhibitors are significantly improved in the presence of [Ca2+] and also that their effectiveness is considerably reduced, or poisoned by increased [Mg2+]. The performance of the phosphonate species are shown to be controlled by the performance of inhibitor/Ca2+ complexes, whereas the formation of inhibitor/Mg2+ complexes effectively poisons the phosphonate species ability to inhibit. The polymeric species (PPCA and PVS) are shown to be less influenced by increased [Mg2+]; indeed, marginally improved performance is obtained. This paper significantly extends the findings reported previously in SPE 3727.
| Original language | English |
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| Pages | 1-6 |
| Number of pages | 6 |
| DOIs | |
| Publication status | Published - Feb 1999 |
| Event | SPE International Symposium on Oilfield Chemistry - Houston, United States Duration: 16 Feb 1999 → 19 Feb 1999 |
Conference
| Conference | SPE International Symposium on Oilfield Chemistry |
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| Country/Territory | United States |
| City | Houston |
| Period | 16/02/99 → 19/02/99 |