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While drilling through clay rocks using water-based mud, number of challenges need to be faced in view of hydration and swelling of this type of rock. Those phenomena consist in the fact, that clay mineral grows in volume due to water contact. In order to limit hydration phenomenon, for clay rocks drilling are used drilling muds with addition of chemical agents called hydration inhibitors. The article describes studies, which resulted in development of new formula of drilling mud with addition of a new short-chained amino polymer developed in Drilling, Oil and Gas Faculty AGH-UST Krakow. For the developed mud, tests of technological parameters were conducted according to API RP 13B-1 as well as specialist examinations: linear swelling of Miocene shale and clay rock disintegration. Studies also consists of syntheses of polyampholyte and short-chained cationic polymer. Based on performed studies, it was found that studied mud is characterized by good and easy to regulate technological parameters as well as effective inhibition of hydration, swelling and disintegration of clay rocks.

The paper describes studies on the development of the new formulas of water-based drilling mud for drilling in clays and shales. The research were undertaken as a part of the OPTIDRILTEC project. First stage of the project included studies related to selection of ionic inhibitors of hydration. The tests of inorganic agents with various concentrations influence on technological parameters of the developed drilling muds was undertaken. The disintegration and linear swelling tests under influence of developed muds with different ionic inhibitors were conducted on the rock samples. Miocene shale was used as the model rocks. Within a framework of the project, it was conducted selection of the polymeric inhibitors of hydration. Subsequently, different polymers were tested for the influence on technological parameters of drilling muds as well as on disintegration and linear swelling of model rocks. Studies also consists of synthesis of short-chained cationic polymers (with primary amine groups in the side chains) and cationic-anionic polymers (with, apart amine groups, sulfonic amine groups). Synthesized polymers are characterized by low molecular masses (about 10.000 – 20.000 atomic mass unit) and small steric hindrance of side chains. The studies allowed development of new water-based mud formulas for drilling in clay rocks. Developed drilling muds are characterized by good technological parameters, resistance to temperature and to salts along with effective preservation against disintegration and swelling of clay rocks. Moreover, based on the research results it can be observed that synthesized cationic polymers are efficient inhibitors of clay rocks hydration. Newly developed drilling muds could be successfully applied in the oil and gas industry causing improved drilling conditions and decreased drilling costs.

The research was supported by the Polish National Center for Research and Development, project Optidrilltec in Blue Gas Programme

The work realized within statutory research program of Faculty of Drilling, Oil and Gas, No. 11.11.190.555