Experimental Study of the Effect of Anisotropy on the Orientation of Breakouts in Wells

Abstract

On rock samples taken from the Cenomanian horizon of the PK1 formation of the gas and gas condensate fields of the Arctic shelf of Russia, direct physical modeling of the formation under the action of equal component stresses of breakouts in wells directed along the normal and along the occurrence was carried out. In the first case, the shape of the breakouts was cylindrical, and in the second case, in the form of two caverns. Such a form of breakouts, when interpreting well logging, is usually assumed to be caused by an unequal component stress field, which obviously does not correspond to the results of the experiments. Independent experiments were also carried out to determine the anisotropy of the elastic and strength properties of the studied rock. It was found that the studied rock has a specific type of strength anisotropy, not directly related to the weakening along the bedding. It is shown that this type of strength anisotropy can lead to the formation of breakouts of the observed shape. The main purpose of the article is to draw attention to the fact that stress anisotropy is not necessarily the main or only cause of the observed breakouts in wells. The results can be used in the design and development of hydrocarbon fields and underground gas storages, as well as in the interpretation of well measurements to determine the natural stress field in the Earth's crust.