PROCEDURE FOR DETERMINING THE NATURE OF CALCIUM CARBONATE FORMATION ON OILFIELD EQUIPMENT

Abstract

In the article, the authors propose to use the method of X-ray diffraction analysis (XRD) to establish the nature of the formation of oilfield deposits using of calcium carbonate as an example. It was shown for the first time that comparative diffraction patterns of natural and technogenic carbonate mineral deposits of oilfield equipment differ significantly in the physical broadening of diffraction reflections. In addition, it has been established that the diffraction reflections of technogenic calcite are characterized by shifts to the region of large scattering angles. These facts are taken as the basis for establishing the nature of the formation of carbonate deposits using X-ray diffraction analysis. It has been shown that natural (core) carbonate minerals are characterized by narrow reflections with good resolution of doublet lines, while in minerals formed under borehole conditions, the diffraction maxima are much broader, and low-intensity reflections are not resolved. Precision analysis of diffraction patterns showed that the reasons for such atypical broadenings and shifts of reflections in technogenic mineral deposits are the relatively small sizes of grains — crystallites and high microdistortions of the crystal lattice compared to their natural analogues. It is shown that in order to establish the nature of carbonate deposits of oilfield equipment, it is necessary to measure diffraction patterns of natural and technogenic minerals under the same shooting conditions. Subsequently, the obtained diffraction patterns are analyzed and X-ray diffraction data on the microstructure of the studied minerals are determined. It has been established that in technogenic calcite the crystallite sizes in all arbitrarily selected directions (hkl) are more than 1.6 times smaller than in its natural analogue. The X-ray diffraction method has shown that the average value of microdistortion of the crystal lattice of technogenic calcite is 1.7 times greater than that of its natural analogue. As a result of comparing X-ray diffraction data on the fine structure of mineral deposits of oilfield equipment with those obtained from core material, the nature of the formation of the analyzed minerals is established. To confirm the XRD results, visual studies using scanning electron microscopy (SEM) were also carried out.