Permeability and Saturation Evaluation in Deepwater Turbidite Utilizing Logging-While-Drilling Low-Gradient Magnetic Resonance

Abstract

fax 01-972-952-9435. AbstractThe economic recovery of hydrocarbons from deepwater reservoirs continues to be a major challenge facing the exploration and production industry, not just contending with the multitude of market uncertainties, but also, more importantly, reservoir deliverability uncertainties associated with deeply deposited pay targets. One large field subject of this study is such, deposited in stacked Pliocene sandstones. These are high net-to-gross, with predominant very finegrained sands. The efficient sweep of the oil in place requires a detailed understanding of the network of the reservoir pore structure, and the permeability distribution and capillary bound fluids.To better understand and characterize the permeability and to help quantify the potential reserves, a novel low gradient magnetic resonance LWD tool for application on conventional drilling assemblies was used. This is a major departure from the more conventional techniques which use high gradient magnetic resonance on post-drilled wireline platforms. Advantages of an LWD approach are twofold; the wellbore is in good condition at the time of drilling, yielding high quality data, and the gain in rig time is significant.The high quality magnetic resonance dataset acquired was confirmed by overlaying with stationary measurements. The data was integrated with offset core data to normalize permeability models and saturation functions. LWD density images acquired during drilling were also used to provide detailed visualizations of the internal laminations of the turbidites, as well as a reservoir structural setting. Formation pressures and mobility measurements acquired during drilling were also integrated in the normalization process to characterize the deliverability of the sands. The resulting permeability model was used to study and redesign future development in the field. The saturation results also provide an improvement over the previous resistivity-only based saturation values, which were pessimistic due to the fine-grained structure of the reservoir sands.

High-Speed Wired Drillstring Telemetry Network Delivers Increased Safety, Efficiency, Reliability and Productivity to the Drilling Industry

“…This type of information can be combined with saturation and permeability information from recently introduced Magnetic Resonance while drilling tools 35 . Clearly the more complete the LWD measurement set in real-time, the better the chance for an accurate model update.…”

Magnetic resonance in porous media: Recent progress

“…Jackson et al 100 used two electromagnets with their north poles facing each other to generate a remotely toroidal region. This type of design is currently used in the logging-while-drilling tools by BakerHughes 101 and operates with a proton resonance frequency in the range of 400-600 kHz. NUMAR developed and commercialized ͑1991͒ an NMR well-logging tool based on a permanent dipole magnet with a cylindrical region of sensitivity.…”