Investigation of cuttings structure changes during the drilling
Rail Kadyrov
The increasing complexity of the developed reservoirs imposes new requirements on the methods for studying geological samples. A breakthrough in high-performance calculations for multiphysical processes allowed us to develop a digital core analysis technology based on X-ray computed tomography, which allows us to study the volume distribution of density inhomogeneities, physicochemical and petrophysical properties of rocks. However, well drilling with core extraction is one of the most expensive procedures in the oil industry. The next step, which may open up new opportunities in obtaining petrophysical information, is the development of the new technology, based on digital analysis of drill cuttings. Drill cuttings are particles that are formed during the drilling of a well. Today sampling of cuttings is required in the situation of low core output during the drilling of weakly cemented, porous and permeable differences. However, even despite the selection of drill cuttings, the amount of information obtained during its analysis is extremely low. Despite the general economic prospects of this area, as evidenced by the interest of various companies in this topic, studies in this area are poorly characterized.
In 2018 in collaboration with a local oil company, we drilled a horizontal well in carbonate reservoirs. During the boring process with core sampling, we filtered the well mud and collected the particles of cuttings (fig. 1). We had estimated the time of cuttings migration up and assigned them by the depth. Then we drilled microsamples from the core for the same intervals as for cuttings and made microCT both for the core samples and cuttings. We found that some part of cuttings had similar structural features as we observed for core samples. This means that they can be originated from the same intervals as core samples. However, drill cuttings experienced a significant structural changes during the migration in the well, which are described in this work.
This work was funded by the subsidy allocated to Kazan Federal University for the state assignment in the sphere of scientific activities (Project No. 0671-2020-0048).
