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SPWLA Distinguished Lecture - Nader Gerges
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Abstract:
Water saturation modelling is a critical step in building robust geological models for the accurate estimation of hydrocarbon volumes in the carbonate fields of the middle east. Many field development plan decisions are based on the reservoir quality, types of hydrocarbons, available resource volumes and fluid distribution within the reservoir. The objective of this paper is to assess the current uncertainties in the log-based and capillary based water saturation models and the challenges of the reconciliation of the two independent models to accurately estimate the hydrocarbon volumes of a Supergiant carbonate reservoir from the UAE.
Hydrocarbon exploration and production on the major carbonate reservoirs of the UAE started in the mid-1960s, where the wireline logging tools were at their infancy in terms of technology and capabilities. Assessing the quality of the initial log-based water saturation models during the pre-production period could be challenging due to the formation invasion, lack of electrical
property measurements from core and the limitation of legacy electromagnetic resistivity tools. This could introduce significant errors on the estimation of log-based water saturation models compared to independent core based capillary pressure saturation height functions. In this paper, a novel methodology is developed to assess the independent uncertainties of the log-based and capillary based water saturation models to improve the reconciliation between the two independent modelling techniques.
Several attempts were made with modern Wireline and LWD resistivity tools to assess the impact of mud invasion on the log-based water saturation models. A full monte-Carlo uncertainty analysis with more than 1000 iterations on all the input variables of the log-based water saturation model is considered to evaluate the impact of each variable on the water saturation distribution of P10, P50 and P90 cases and its equivalent hydrocarbon volumes. A similar uncertainty analysis is conducted on the all the input variables of the capillary based water saturation modelling including the saturation equation selection, rock-types, porosity, permeability, interfacial tension, contact angle and free water level. Multiple methods were developed to reconcile the two independent water saturation models using the bulk volume of water and height above free water level per rock-type to ensure
the robustness of the water saturation distribution at the well level and within the 3D Geological model. The results have shown distinct patterns of uncertainty ranges depending on the well locations, transition vs Irreducible zones or based on rock-typing scheme.
A novel workflow was developed to assess the full uncertainties on the Saturation height modelling including all its input variables. The current workflow for the reconciliation of the log-based and capillary based water saturation model in carbonate reservoirs using the full uncertainty analysis have shown very valuable insights on the inherent uncertainties on each independent model and how it impacts the hydrocarbon volumes. This novel methodology led to a better understanding of the reliability of each saturation model specially when the two results are in a disagreement.
Bio Lecturer:
Nader Gerges has been an esteemed member of the SPWLA since 2004. He currently serves as a Senior Specialist Petrophysicist within the Advanced Geoscience Solutions team at ADNOC’s Thamama Excellence Centre. In this role, he supports best practices in Petrophysical modelling, reservoir characterization, EOR, and reservoir model assurance across the ADNOC Group of Companies. Nader Gerges holds a bachelor’s degree in Electronics and Robotics Engineering from Cairo University and brings with him an impressive 24 years of experience in the oil and gas industry. His areas of expertise encompass Petrophysical Modelling, Reservoir Characterization, Reservoir Monitoring, Geosteering operations, and developing Digital solutions for enhanced reservoir management and Field Development plan optimization. Throughout his illustrious career, he has contributed to projects worldwide, including in Egypt, Indonesia, Thailand, the UK North Sea, the US Gulf of Mexico, Norway, Canada, Nigeria, Iraq, Congo, Libya, and the United Arab Emirates.
Where
Building 5, Level 5, Room 5220
Thuwal, Makk Saudi Arabia