Productivity Enhancement from Acidizing Horizontal Wells Drilled in Thin Carbonate Reservoir Layers

Abstract

Abstract This paper presents a careful integration of geomechanical and reservoir properties to avoid excessive fracture extension and achieve proper acid containment within a thin reservoir layer, yielding very successful results. In general, wells drilled in thin reservoir layers may not produce or sustain continuous production for an extended period, even though the reservoir may have good oil saturation and pressure support. Log derived mechanical properties and empirical correlations from lab test performed on numerous core plugs were compiled for geomechanical modeling. In addition to the density log integration, the dynamic and static mechanical properties were utilized to estimate the maximum and minimum horizontal stresses. The fracture gradient, wellhead injection pressure, acid volumes and operational requirements were determined to properly design the acid job to avoid fracturing the reservoir beyond its thickness, but effectively establishing communication between the reservoir and the bore hole. Well data gathering such as completion type, intervals to be acidized, and reservoir pressure were also incorporated during the workflow process. The approach was piloted in two wells. The productivity improvement from the acidizing job for the cases presented, show effective results in terms of near-wellbore formation damage removal and flow capacity improvement. The selected wells, former intermittent producers, responded favorably to the acid pumped with a considerable increase in oil production. Water cut did not initially increase, reflecting the effective avoidance of fracture creation to connect to lower aquifer zones. The validity of the log derived mechanical properties and stress profiles, as well as the lab derived correlations confirmed the validity of properly characterizing the reservoir in terms of strength and stiffness. Production improvement, modelling process and treatment have been captured and shared in this manuscript.