Abstract

A vibrating rod downhole fluid density device with the unique perpendicular oscillation modes provides in-situ fluid density measurements that improve a wireline formation tester's pressure, mobility, downhole fluid analysis, and sampling applications.

The measurement applications for the real-time water-base mud (WBM) formation-water sampling include contamination monitoring, in-situ fluid density, fluids identification, pressure gradient and fluid contact, and vertical compartmentalization. Field examples validate the measurements with the sample laboratory analysis and other measurements.

Introduction

Understanding the nature and composition of formation water is just as critical to the economics of field development as determining hydrocarbon composition. Chemical analysis of formation or connate water determines the scaling and corrosion potential of produced fluids, which determination is required for the design of completion and processing facilities. It also establishes the salinity for petrophysical evaluation, and fingerprints the aquifer for studies on basin hydrology. Water composition is important for production strategies involving inhibitor injection, wellstream mixing, process sharing, and enhanced oil recovery (EOR) injection (O'Keefe 2006; Godefroy et al. 2008).

The formation water samples are required early in the exploration /appraisal phase because water will not be intentionally produced from conventional drill stem testing (DST) and will not be produced until the field cut water at the later stage, thus too late for the planning. In the offshore or in environmentally sensitive areas, where margins for error are small and large capital expenditures must be spent upfront, proper planning is crucial.

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