Depok, May 12, 2026 – Wellbore instability remains a major challenge in the oil and gas industry as it can trigger various operational risks, ranging from wellbore collapse, pipe sticking, to rock fractures that cause loss of drilling fluid (lost circulation). These conditions not only increase operational costs and cause project delays, but also pose safety risks and reduce the effectiveness of hydrocarbon exploration and production.

This issue formed the background for the topic “Basic Geomechanic for Wellbore Stability Analysis” in the UI Geoscience Seminar x STARBORN MENGAJAR 2026 organized by Faculty of Mathematics and Natural Sciences, Universitas Indonesia on Monday (May 11, 2026) at Aula Prof. Dr. G.A. Siwabessy, Kampus FMIPA UI, Depok.

The event was attended by students from the Geology and Geophysics Study Programs at Faculty of Mathematics and Natural Sciences, Universitas Indonesia. The seminar featured Kukuh Al Rasyid, S.Si. as the speaker, a Business Analyst at PT Geoservices, with Agus Riyanto, S.Si., M.Si. serving as moderator.

In his presentation, Kukuh Al Rasyid, S.Si. explained that failure to properly understand subsurface geological conditions and rock mechanics can lead to inaccuracies in determining safe drilling pressures. As a result, wellbore stability becomes difficult to control.

According to Kukuh Al Rasyid, S.Si., wellbore stability is closely related to the interaction between pore pressure, subsurface stress distribution, rock elasticity characteristics, and mechanical changes caused by drilling activities. Therefore, a geomechanical approach is considered essential to help engineers and geoscientists predict rock responses to drilling processes through the analysis of physical and mechanical rock parameters.

“This understanding is needed to determine an optimal drilling design, including defining the mud weight window so that the drilling fluid pressure remains within safe limits—high enough to withstand formation pressure, but not exceeding the rock strength that could trigger fracturing,” said Kukuh Al Rasyid, S.Si.

He added that geomechanics is a branch of science that studies the mechanical behavior of rocks and the effects of pressure on subsurface conditions. According to him, understanding geomechanics plays an important role in maintaining wellbore stability during drilling operations.

“Geomechanics is an important foundation for understanding subsurface conditions so that drilling operations can be carried out more safely and efficiently,” said Kukuh Al Rasyid, S.Si.

The material presented covered various geomechanical parameters such as pore pressure, stress, rock strength, and rock elasticity, which are used in the development of a Mechanical Earth Model (MEM). This model serves to comprehensively describe subsurface mechanical conditions, enabling its use in the planning and evaluation of drilling operations.

Participants also received explanations on overpressure mechanisms, methods for estimating pore pressure using well log data, as well as the concepts of stress polygons and near-wellbore stress to understand stress distribution around the wellbore. Kukuh Al Rasyid, S.Si. explained that changes in stress around the borehole can affect rock strength and may trigger formation failure if not properly analyzed.

In addition, Kukuh Al Rasyid, S.Si. presented the rock failure criterion concept using the Mohr–Coulomb approach to analyze the potential for wellbore breakout and fracture. This approach is used to understand the limits of rock strength under specific stress combinations, enabling early prediction of possible rock failure or fracturing.

“Through wellbore stability analysis, potential drilling problems can be predicted earlier so that operational decisions can be made more accurately,” he said, referring to Kukuh Al Rasyid, S.Si.

After the presentation session, the event continued with an interactive mini-quiz designed to test participants’ understanding of basic geomechanics concepts and wellbore stability analysis. Three participants who successfully answered the questions correctly received souvenirs as a form of appreciation from the speaker.

In the closing session, Kukuh Al Rasyid, S.Si. reaffirmed the importance of mastering geomechanics to support safe and effective drilling operations. He also expressed his appreciation to the organizers and participants for the opportunity to share knowledge during the event.