tailieunhanh - Investigation of calcium carbonate scale inhibitioand scale morphology by scanning electron microscopy

Calcium carbonate scale inhibition in squeeze treatment by the phosphonate–type scale inhibitors, such as diethylenetriamine penta (methylene phosphonic acid) (DETPMP), ethylene diamine tetra(methyelne phosphonic acid) (EDTMP) or by the mixing of DETPMP, EDTMP and chelants (citric acid (CA), maleic acid (MA), ethylendiamintetraacetic acid (EDTA) has been studied in previous works [5,6]. This paper focused on several aspects concerning calcium carbonate scale inhibition mechanism of DETPMP and of the mixing of DETPMP with trace of chelants by scale morphology on scanning electron microscopy (SEM). From the SEM photos, it can be observed that the presence of the inhibitors, especially with the right ones, causes | Journal of Chemistry Vol. 43 3 P. 384 - 387 2005 INVESTIGATION OF CALCIUM CARBONATE SCALE INHIBITION AND SCALE MORPHOLOGY BY SCANNING ELECTRON MICROSCOPY Received 23rd-June-2004 NGUyEN THI PHUONG PHONG Institute of Materials Science Hochiminh City branch Hochiminh City SUMMARY Calcium carbonate scale inhibition in squeeze treatment by the phosphonate--type scale inhibitors such as diethylenetriamine penta methylene phosphonic acid DETPMP ethylene diamine tetra methyelne phosphonic acid EDTMP or by the mixing of DETPMP EDTMP and chelants citric acid CA maleic acid MA ethylendiamintetraacetic acid EDTA has been studied in previous works 5 6 . This paper focused on several aspects concerning calcium carbonate scale inhibition mechanism of DETPMP and of the mixing of DETPMP with trace of chelants by scale morphology on scanning electron microscopy SEM . From the SEM photos it can be observed that the presence of the inhibitors especially with the right ones causes deformation of the crystal morphology of both the adhered and precipitated crystals. The strong depression of adhesion of crystal calcite is caused by the adsorption of inhibitor on its surface. I - INTRODUCTION Oilfield scale is practically a ubiquitous problem in oilfield operations. It can form when incompatible waters mix for example during water flood or it can form when reservoir pressure and temperature changes are endured by self-scaling brines. Sulfat scale commonly occurs with the former mechanism and carbonat scale with the latter 1 2 . CaCO3 scale deposition depends upon the temperature of the fluid calcium carbonate scale exists predominantly in calcite form at temperature of 50oC and exists predominantly in aragonite form at temperature of 65oC. Carbonate calcium has in practice three polymorphs forms calcite hexagonal aragonite ortho-rhombic and vaterite hexagonal depending on the increasing solubility and decreasing thermo-dynamic stability. In our works 5 6 phosphonates are the most .