(28a) R&D Efforts to Control, Monitor and Identify Drilling Fluid Invasion in Reservoir Rocks

In exploratory wells during sampling operations the drilling fluid filtrate invasion into the reservoir increases operation time and the possibility of contaminating samples. Inadequate fluid samples can lead to inaccurate information about the economic feasibility of the reservoir development. In heavy oil reservoirs, oil and filtrate interaction may generate stable emulsions, reducing its initial and/or its long term productivity. Invasion in light oil reservoirs is less critical, due to its good mobility properties. Another critical scenario is low permeability gas reservoirs where imbibition effects may result in deep invasion, causing a phenomenon known as water blocking, dramatically reducing production

This article aims to summarize R&D efforts to control, monitor and diagnose drilling fluid invasion in reservoir rocks. The main focus includes:

·     Modeling of drilling fluid invasion in two-phase radial flows considering: fluid and filter cake compressibility, relative permeabilities, anisotropic rocks, capillary effects, fines migration, break=out pressures, inversion log analysis.

·     Experimental methodology to evaluate and optimize filter cake properties, including shape and size distribution of bridging agents, static and dynamic filtration processes, quantitative evaluation of filter cake compressibilities, and filtration in anisotropic and fractured cores.

·     Software development for optimizing of bridging agent and the necessary requirements for Field implementation.

·     Customization of drilling fluid systems for non-conventional reservoirs.