Early exploration well tests in the Colville River field (also known as the Alpine reservoir) drilled with water-based mud (WBM) systems exhibited unexplainably high near-wellbore residual skin damage documented by pressure-buildup testing. Typical formation-damage mechanisms, including clay reactions, mechanical damage, and gas trapping, could not explain the damage.Between March 1998 and July 2001, laboratory testing determined imbibition-induced water trapping to be the primary formation-damage mechanism. In-situ water saturation is significantly lower than residual or connate-water saturation, a condition rarely encountered in the field. Lab tests quantified impacts and identified methods to minimize or eliminate formation damage. This paper documents how successful identification of a unique damage mechanism improved drilling results in low-permeability sandstone.

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TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractQuantitative production logging of openhole and horizontal wellbores presents a challenge for conventional logging tools and techniques. The complicating factors of horizontal logging are primarily related to low fluid velocities and stratified flow. Openhole horizontal completions further the challenge by increasing the opportunity for tool fouling and fill obstruction, creating abrasive running environments, and finally complicating interpretation with unknown hole geometries.To address these challenges, a new diverter logging system based on inflatable packer technology has been developed. The tool is inflated at discrete locations in the horizontal section so that all flow at each stop is diverted through rockexcluding screens and past conventional memory logging tools in a carrier. Pressure drop through the tool is minimal, and the fixed internal diameter carrier allows for high resolution logging over a wide range of rates.Developing a method to allow packer setting and resetting in wire/umbilical-free Coiled Tubing (CT), while constantly maintaining a production or injection path through the tool, called for innovative engineering. The tool has been run in nine wells to date. This paper will discuss the need, development, and field results of the new inflatable packer logging system.

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