Rola związków glinu w stabilizowaniu skał ilasto-łupkowych

In most regions of the country where exploration is carried out, the cross-section of geological units is characterized by the predominance of clay and shale rocks. These rocks can easily disperse or swell; they also show structural damage in the form of crevices and micro-fractures. Therefore, they are often a source of unforeseen difficulties resulting from the lack of stability of the borehole wall, which sometimes prevents it from reaching its planned depth. The borehole wall stability is most often considered in two aspects, i.e. mechanical, which analyzes the forces and pressure acting on the borehole wall, and physicochemical, regarding the impact of the drilling fluid on the drilled layers. However, a significant role in stabilizing shale rocks is attributed to the physicochemical impact of drilling mud. Both laboratory tests and industrial experiments prove that the proper selection of drilling mud composition influencing its rheological and structural as well as inhibiting properties facilitates controlling the course of physicochemical processes occurring in the clay rock - drilling mud system. In borehole drilling of clay-shale rocks differing in mineralogical composition as well as physical and mechanical properties, a tripleinhibited drilling mud containing ionic inhibitor – KCl and two organic polymer inhibitors – PHPA and polyglycol is used. One of the newer directions of laboratory tests conducted at INiG – PIB was the use of aluminum compounds in the drilling mud composition in combination with organic acids, i.e. humic and fulvic acids. The composition of these agents in the composition of the developed drilling mud played the role of the basic, inorganic polymer inhibitor – Al-KHF, called the shale stabilizer. Its mechanism of impact on shale rocks consists in blocking their pores by the resulting Al(OH)3 deposits and humic acid flocculates. Under appropriate borehole conditions, the resulting precipitates, forming in pores and micro-fractures, create a physical barrier that blocks water/filtrate access and prevents pressure build-up. The article presents the results of selected research methods on the basis of which the influence of the developed drilling mud containing aluminum stabilizer and the mud used in borehole conditions on the stability of shales with different clay content was determined. Analysis of the test results showed that depending on the hydrophilic properties of clay shale, a drilling mud containing Al-KHF with or without glycol may be used to drill them.