Understanding the Mechanisms of Drilling Challenges through a Systematic Risk Assessment and Geomechanics Modeling; a Post-Drill Case Study, Balsam Field, Onshore East Nile Delta, Egypt

Abstract

This case study represents an approach of applying a systematic risk assessment in combination with Post-Drilling Geomechanics modeling to properly understand the root causes of drilling challenges through Late Messenain – Early Tortunian formations, Balsam field, onshore East Nile Delta, Egypt. The aim of the analysis is to support pro-actively the operator to drill the future wells safely through the problematic formation in the field. According to the risk assessment; drilling the reservoir section experienced three major challenges including downhole losses, tight spots, and differential sticking. The case study includes two phases; phase-I (Risk Identification Phase) considers defining the drilling hazards utilizing daily drilling reports (DDR’s), meanwhile Phase-II considers (1D Geomechanics & Wellbore Stability) constructing a post-drill Geomechanics models using a licensed Software using all available E-logs, borehole image and caliper data. Post-drill geomechanics models calibrated using drilling events, borehole image, caliper data and reservoir pressure measurements. The results of both risk identification and geomechanics models confirms that tight spots and differential sticking was related to overbalance drilling with improper wellbore strengthening package of drilling fluids that results in invasion/pressure transmission and eventually thick filter cake across high permeable/depleted sandstone rock. the study results indicates that the drilling challenges might be related to certain geomechanics signs e.g. time-dependent failures, weak bedding planes and pressure transmissions. Those Geomechanics events could be related to fluids-rock interactions and lack of improper wellbore strengthening art. The study outcomes would help in minimizing drilling challenges for future wells considering both drilling practices and drilling fluids design.