First Core Analysis-Based Acid Fracturing Strategy Unlocked the Full Potential of the Abu Ghirab Oilfield Asmari Complex Carbonate Reservoir

Abstract Objectives / Scope The Abu Ghirab oilfield is located in the Missan province, southeast Iraq, near the borders with Iran. The Asmari Group A reservoir mainly consists of Tertiary carbonate formations with low to medium interconnected porosity; natural fractures and vugular storage capacity are both present at different intensity among its sub-layers defining its reservoir quality heterogeneity. Primary target zones contain interbedded dolomite and argillaceous dolomite layers that promotes an inherent rock fabric and properties anisotropy. This paper presents the first ever horizontal well successfully stimulated in the Missan basin, using a core analysis-based acid fracturing technique focused on deploying sustainable conductive hydraulic fractures along the complex carbonate lateral section. Methods, Procedures, Process The reservoir heterogeneity led to poor initial productivity for some of the candidate horizontal wells. Therefore, a Matrix Acidizing campaign got deployed with no significant improvement, having several stimulated wells still unable to produce at a continuous and sustainable-economic rate. As a result, a full core study coupled with laboratory tests, reservoir petrophysics, image logs and geomechanics analysis were carried out to define the optimum stimulation strategy. Several representative cores from the three Asmari Group A sub-layers were strategical selected to perform X-ray Diffraction, Scanning Electron Microscopy, Casting Thin Section analysis and Core Strength-Elastic Properties Tests to define the optimum Stimulation and Completion Strategy. Treatment Fluids technology platform was tailored through Acid-Core Flow tests, Acid-Core Etched Fracture Conductivity test, Acid-Core Reaction Rate, Activation Energy and effective Mass Transfer Coefficient measurements, Based on the comprehensive core-centric study and an integrated carbonate stimulation modeling, a unique Acid Fracturing treatment combined with a bi-modal degradable particles diverter confirmed to be the optimum production enhancement Technique. Results, Observations, Conclusions The Asmari reservoir candidate well has transformed from a non-productive well into a high sustainable production asset. This First successful strategic workflow implementation as well as the measured acid-rock reaction kinetics parameters described in this paper, will provide a strong technical platform and guidance for the entire Missan province carbonate basin development. Novel / Additive Information This paper takes a novel acid frac technology approach, enhanced by the principal petroleum engineering disciplines and core-centric studies to its successful practical end-use where there had been doubt on the asset return on investment as well as the full potential benefits for the southeastern Iraq region development. The Carbonate Stimulation Model calibrated with the measured reaction kinetics, image logs preferred fracture plane and geomechanical parameters showed an excellent matching with the post-job fracture geometry and production performance results.