Unveiling the Potential: A Novel Hydraulic Fracturing Workflow for Laminated Limestone Stringer Formation

Abstract Hydraulic fracturing was not initially part of the development strategy for the Ghazij formation—a vertically heterogeneous, laminated limestone-shale reservoir in Pakistan—due to concerns over fracture containment and mechanical complexity. However, positive results from prior acid stimulation campaigns and the potential for improved reservoir access prompted the execution of a dedicated Proof of Concept (PoC) hydraulic fracturing program. This paper presents the first PoC implementation in the Ghazij formation, focused on validating fracture placement feasibility and informing future stimulation design in complex laminated systems. The study followed a fully integrated, cross-disciplinary workflow structured into three key phases: Pre-Drilled, Post-Drilled, and Evaluation. In the Pre-Drilled Phase, regional well logs, core measurements, and offset production data were used to construct a detailed static model incorporating petrophysical layering, elastic properties, and mechanical facies. Particular emphasis was placed on identifying fracture-prone stringers, mapping natural barriers, and delineating productive lobes within the reservoir. Mineralogical evaluation using XRD and cutting analysis highlighted zones dominated by swelling clays and shale laminations, informing both frac fluid compatibility and embedment risk. In the Post-Drilled Phase, image logs revealed critical insights into in-situ stress orientation, lamination architecture, and bedding-plane slippage potential. These logs were used alongside sonic and density data to calibrate a 1D Mechanical Earth Model (MEM) tailored to the Ghazij pilot well. Cement bond evaluation confirmed zonal isolation, enabling two stages fracturing across discrete lobes. A Diagnostic Fracture Injection Test (DFIT) further refined the pore pressure and stress gradient assumptions, strengthening the MEM and stage-specific treatment design. During the Evaluation Phase, both stages were executed using different stimulation philosophies. Stage-1 employed a conservative baseline design, while Stage-2 implemented an optimized approach using modified fluid chemistry and proppant strategy. Early-time production testing revealed a significant uplift in gas rate and improved cleanup performance in Stage-2, confirming the benefits of tailored treatment design in mechanically layered systems. This work demonstrates that hydraulic fracturing is technically feasible in the Ghazij formation and highlights the critical role of integrated petrophysical, geomechanical, and mineralogical analysis in de-risking stimulation in laminated carbonate-shale reservoirs. The workflow and findings presented herein provide a valuable reference for future vertical, deviated, and horizontal well development in similar complex settings.