Formation Damage: A Novel Approach to Evaluate Zonal Productivity Loss in Horizontal Wells

Abstract

Abstract The development of a complex oil wet carbonate green field requires an integrated data approach to characterize the reservoir and build a robust dynamic model, which will allow evaluating different development scenarios. Nevertheless, the predicted productivity of highly deviated wells is usually different from the actual values. This problem can lead to poor well completion choices and to suboptimal reservoir development plan. To overcome the issue, the detailed analysis of downhole wellbore damages and their impact on production per zone should be evaluated. In this study, a well productivity simulation model was built to model the flow behaviour in a horizontal well and was tested against the actual production logging data. The proposed formation damage estimation is based on the integration of conventional core analysis from nearby wells with logs aquired while drilling and wireline and with data from well testing pressure transient analysis before and after acidizing. The model was used to evaluate the impact of formation damage on zonal productivity. The proposed formation damage evaluation methodology allows reconciling between actual and expected productivities of reservoir zones across horizontal wells. A synthetic production profile with distributed drilling and acid damage skin is generated by the well model and is matched with actual production profile of a recently drilled and logged well. The results show the progression of damages through various stages of the well cycle: for permeable zones, the invasion is progressing heterogeneously while drilling and acidizing; for less permeable zones, the invasion caused by drilling might not be completely overtaken by acid stimulation. The study demonstrates the importance of drilling and well completion duration in invasion progress across the wellbore length. The paper describes a novel methodology to construct distributed formation damages across open hole wells in carbonate reservoirs and to evaluate the effects of damages on zonal productivity. This methodology improves the prediction of well productivity by identifying the contribution of various damages to zonal productivity. This is critical for efficient decision making concerning well completions and field development options, particularly at the early stages of green field development.