Variation of Total Stresses During Field Operation Using Finite Element Technique, Zubair Oil Field.

Abstract

Most problems in the Zubair oil field are geomechanical which can lead to maximized the non-productive time and some of these troubles are reservoir compaction, porosity change, permeability change, wellbore instability, casing smash, pipe damage, and well kick. This study was to introduce a couple of the reservoir model and geomechanical model using the finite element method. The interesting data (logs, calibration data, drilling, and mud report) were utilized to build one dimensional model (1D) for each well using Techlog 2015 software. The 3D geomechanical model builds by Petrel 2017 software while the finite element technique was built using CMG 2018 program to forecast the stress states during production or injection operation in the field for 10 years. The 1D model results show a good match between mechanical properties and calibration data which is mean a perfect mechanical earth model. Distribution results of all mechanical rock properties in the 3D geomechanical model showed that Shuaiba and Al-Hammar domes were not sufficient for stable wells, especially in the Tanuma formation. While the results of Mishrif formation showed more stability despite production. 3D Finite element model results showed that the total horizontal stress decreases during production and increases in injection wells, this would cause increases in the effective horizontal stress during production and a decrease for injection. The effective vertical stress increased during the production and decreased during injection wells. Based on these results production could cause an increase in the differential stress which leads to rock shear failure.