Harmonizing an Amalgamation of Advanced Technologies: The Enduring Learning Curve in Tar Identification

Abstract Heavy oil and tar-bearing formations marked by elevated viscosity levels pose formidable production hurdles, affecting key factors including oil mobility, flow rates, injectivity and overall production efficiency. Horizontal wells intersecting these zones often fall short of target production rates and ultimate recovery objectives, resulting in less favourable well economics and reduced return on investment. This study aims to confront these challenges through optimized solutions and advanced technologies, with the goal of augmenting production efficiency. While conventional triple-combo logs have been used in the past for tar identification, their precision in quantifying tar quantities and fluid properties is limited. The methodology is structured on timely and accurate tar detection, incorporating real-time Nuclear Magnetic Resonance (NMR) data and Pyrolitic Oil Productivity Index (POPI) services, alongside Formation Pressure While Drilling (FPWD) tool. This holistic approach enables real-time interpretation and empower decision-making directed at early tar zone identification. Upon tar zone detection, the deep azimuthal resistivity tool deployed in real-time to strategically maintain a safe distance from the pre-defined tar zone, ensuring seamless drilling operations devoid of tar-related challenges. The methodology has demonstrated its effectiveness in multiple wells, successfully identifying TAR and heavy oil across diverse formations. NMR technology has revealed intriguing findings during the analysis of high-viscosity tar, distinct from more mobile fluids such as water and conventional oil. The NMR data yielded underestimated porosity compared to the conventional measurements. This divergence arises from the distinct relaxation behaviour of tar, causing faster return to equilibrium after excitation, shorter relaxation times, and rapid signal decay, often extending beyond the standard NMR logging tool capabilities. Heavy oil exhibits distinctive relaxation behaviour compared to other fluids. causing signal decay within bound fluid relaxation time, resulting in an increase of the bulk water volume compared to values derived from conventional measurements. These findings are substantiated through pressure points, revealing low mobility indicating restricted fluid flow. This multifaceted approach has achieved a dual purpose. Firstly, it provides insights into formation mobility, a critical factor for confirming the presence of tar. Secondly, it expedites early tar zone detection, streamlining decision-making and mitigating tar-related challenges. The utilization of the azimuthal distance-to-boundary tool plays a noteworthy role in maintaining a safe separation from the tar zone, thereby enhancing the overall efficiency of the methodology. The methodology stands out for its forward-thinking and solution-focused approach, which enables the early detection of tar reservoirs during drilling operations. It facilitates data-driven decision-making to enhance productivity and mitigate risks. This comprehensive strategy not only identifies tar zones but also achieves significant cost savings and enhanced operational safety by seamlessly integrating the navigation service into the workflow. This integration firmly establishes the methodology as an innovative best practice within the industry.