Optimizing fluid cleanup efficiency using mud-filtrate contamination transient analysis and the reciprocal contamination derivative method




Gelvez Gonzalez, Camilo Andrés

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Successful in situ fluid cleanup and sampling operations are commonly driven by a fast and reliable analysis of pressure, rate, and contamination measurements. Techniques such as pressure transient analysis (PTA) and rate transient analysis (RTA) currently provide important information to quantify reservoir complexity, while fluid contamination measurements are commonly overlooked for reservoir characterization purposes. I introduce a new interpretation technique to relate fluid contamination measurements with reservoir properties by identifying early- and late-time flow regimes in the derivative plots of reciprocal fluid contamination. Contamination transient analysis (CTA) evaluates transient measurements acquired during cleanup of mud-filtrate invasion to infer important reservoir geological and flow conditions. This thesis project presents the application of derivative methods to the reciprocal of the time evolution of fluid contamination to identify flow regimes, and an evaluation of the performance of several probe configurations under equivalent reservoir conditions to quantify and optimize filtrate cleanup efficiency. The study is carried out using a compositional simulator for a water-bearing reservoir invaded with blue-dye tracer included in water-base mud (WBM) filtrate. Complex tracer dynamics are accurately and expediently modeled using a flexible numerical algorithm to account for different probe types and tool configurations. Numerical simulations compare the fluid cleanup efficiency for various commercial formation-testing probes together with innovative probe designs that could potentially lead to a new tool or probe development. In addition, seven reservoir cases of WBM invading either water-or hydrocarbon-saturated formations are simulated to obtain contamination data: (1) homogeneous isotropic reservoir, (2) formation thickness, (3) laminated formations, (4) geological faults, (5) mud-filtrate invasion, (6) reservoir properties, and (7) permeability anisotropy. Reservoir limits and reservoir features are identified in the flow regimes detected with derivative plots of the reciprocal of the contamination. Moreover, field case studies are analyzed to highlight the value of the reciprocal contamination derivative (RCD) in real-time operations. The new approach of the RCD is an alternative to optimize fluid cleanup efficiency and to quantify the spatial complexity of the reservoir during real-time operations


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