Mechanical Earth Model (MEM): An Effective Tool for Borehole Stability Analysis and Managed Pressure Drilling (Case Study)

Abstract

Abstract As a borehole is drilled, hydraulic pressure of the drilling mud must replace the support lost by removal of the original column of rock. But mud pressure being uniform in all directions cannot exactly balance the earth stress. Consequently, rock surrounding the borehole is distorted or strained, and may fail if the redistributed stresses exceed rock strength. The bottom line for the drilling engineer striving to maintain stable hole is choosing the right mud weight. The aim of this study is to build a Mechanical Earth Model using available data for one of the Iranian oil field to evaluate wellbore stability and to choose optimum mud weight. For making MEM different sources of data including, drilling data, logging data, DST, MDT, LOT, FIT, etc were used. After making MEM with available data, suggestion for selection the right mud weight for each interval to prevent the common instability problems (lost circulation, borehole breakout) 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 sand production and perforation stability and so on. Numerical modeling has been carried out using MEM data for comparing analytical and numerical wellbore stability analysis to select optimum mud weight, to investigate the feasibility of managed pressure drilling for problematic formations, and to determine the most effective azimuth for drilling horizontal wells into the reservoir section.