Geomechanics-Driven Well Design for Offshore Tight and Weak Sand Reservoirs: Wellbore Stability Management and Sanding Prediction in Anambas Field, Indonesia

Abstract KUFPEC Indonesia (Anambas) B.V. is planning to develop the Anambas Field, located offshore Natuna, Indonesia. Recognizing that the reservoir is prone to sand production, KUFPEC conducted a comprehensive geomechanics and sand production study using available subsurface data. The planned wells are designed to be deviated, including one extended-reach drilling (ERD) well. Consequently, careful planning of mud weight design and casing shoe depth selection is essential to ensure wellbore stability, prevent formation failure, and support safe and efficient drilling operations. There are eight (8) development producing wells located in Anambas Field offshore Natuna, Indonesia that will be developed after successful discovery of A-2X Exploration well. The four (4) wells are to be developed as first drilling campaign followed by another four wells on second drilling campaign. Before conducting further analysis on sand-production, wellbore stability and hydraulic fracturing design, a Mechanical Earth Model (MEM) was generated utilizing available data in three offset wells incorporate log data, drilling experiences, available pressure information, and rock mechanics tests to calibrate the mechanic properties. The primary tool used was sand-management, wellbore stability within Techlog* software (SLB proprietary software) which is based on linear-elastic model. Sand production risk was evaluated by calculating the critical drawdown pressure across all reservoir intervals for four (4) planned wells. The analysis included sensitivity testing against various input parameters such as unconfined compressive strength (UCS), grain size, well trajectory, and perforation orientation to account for uncertainties. The mud weight window was also calculated to determine the safe drilling range for each planned well, including sensitivity analyses of borehole azimuth and inclination. The study offers advantages by delivering a rapid yet accurate evaluation, the approach enables quicker decision-making without compromising reliability. By integrating sensitivity analyses and calibrated MEM, the integrated study will optimize the well completion strategies in challenging reservoir conditions.