Drilling through subjected mature offshore oil field is made more challenging by problems arising from wellbore instability, mud losses, excessive cutting, tight hole, stuck pipes and kick/flow zones for last few years. These problematic layers have caused quite a significant NPT (non productive time) during drilling.

For better understanding of factors causing wellbore instability problem and to predict mud weight window to be used for future wells, construction of mechanical earth model (MEM) was essential.

Mechanical Earth Model (MEM) is a numerical representation of the state of stress and rock mechanical properties for a specific stratigraphic section in a field or basin2 .

In this study main drilling problems for each drilling interval in this field were described afterward different stages for construction an 1D Mechanical Earth Model (MEM) for the field was established. It was then demonstrated that how 1D MEM could be used to predict and prevent the common instability problems encountered during drilling.

For making MEM different sources of data including, drilling data, formation evaluation data, well testing, etc were used.

After making MEM for the field, safe and intact mud weight window was determined and according to that, suggestions for optimum mud weight for stable borehole on each interval was made.

MEM for this field can now be used to predict not only the safe mud weight window and possible drilling hazards, but can also be used for studies like reservoir compaction, sand production, and perforation stability and so on.

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