###### Abstract  
Nowadays, the exploration of different deep subsurface energy-related natural resources (oil/gas, natural hydrogen, geothermal, among others) is gaining importance. The exploration of these deep subsurface resources can present several challenges, such as complex lithology to be drilled, high depth to be reached, and considerable rock hardness, among others. In this context, the implementation of methodologies focused on real-time operational efficiency improvement has gained attention. Mechanical specific energy (MSE), rate of penetration (ROP), and even vibrations are key indicators that can be combined and used for drilling process optimization and efficiency improvement. These indicators are linked to operational drilling mechanic parameters, such as weight on bit (WOB), rotary speed (RPM), torque (TOR), and flow rate (FLOW). Despite this, multi-objective research considering both MSE and torsional vibration (stick-slip) has been largely overlooked in drilling optimization studies. Therefore, the main objective of this paper is to analyze field data from carbonate reservoirs using a multi-objective optimization approach based on torsional vibration, by means of stick-slip and MSE analyses. The focus is to minimize MSE values and mitigate stick-slip using self-developed decision matrices which consider WOB, RPM, and FLOW as key elements. The research results demonstrated that FLOW is a crucial parameter for minimizing torsional vibrations and should be prioritized in drilling operations, also for mitigating undesirable events. The optimization process yielded optimal WOB values for each RPM range (from 100 to 180 [rev/min]) and FLOW range (from 2200 to 3900 [L/min]). The decision matrix revealed that regions with high desirability correspond to high RPM (above 120 [rev/min]), with WOB varying from 5 to 13 [tf], and FLOW rates above 2300 [L/min]. Critical drilling conditions occur when low RPM, low FLOW, and high WOB (above 13 [tf]) are applied, as these conditions and this combination of parameters are most susceptible to release severe torsional vibrations, indicating a higher risk of operational problems. vibration; drilling; efficiency; stick-slip; decision matrix; flow rate +
Footnote †: journal: Applied sciences  
0000-0002-4800-0000-0000-0000-0000-0000-0000-0000-0000-0000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-00000-000000-0000  
been an increasing demand for energy due to rapid economic and social development [2]. However, the high energy demands led to the depletion of global shallow oil and gas resources [1; 3; 4; 5]. Consequently, global oil and gas exploration and prospection has shifted from shallow targets, gaining a focus directed to deep and ultra-deep reservoirs [6]. For example, the pre-salt layers in Brazil, which encompass a large quantity of oil and natural gas reserves, can be found approximately 300 [km] from the coast in some locations, at varying depths, ranging mostly between 5000 and 7000 [m] [7]. Other wells drilled to great depths can be found around the world, such as in the Western Sichuan Basin in China, where the well depth reaches 8600 [m] below sea level [8; 9], and in the Shunbei Oil and Gas Field in the Tarim Basin, where a well exceeds 9000 [m], making it the deepest well in an Asian Onshore Oilfield [6]. Deep drilling is key in actual oil and gas exploration and exploitation [2], but in such environments there are challenges to face, unique from location to location, such as complex lithology, considerable formation resistance [1; 2; 3; 8; 10], weakness of real-time data transmission, considerable vibrations and also persistent stick-slip [11; 12]. These factors lead to a sharp drop in the rate of penetration (ROP), a reduction in drill-bit life, an overall increase in drilling time, and a higher risk of accidents and complications [10; 13]. The drilling industry has been continuously researching methods, techniques, and technologies aiming at enhancing drilling efficiency and reducing drilling costs [14].