Quantitative 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 rock-excluding 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.
The operators of the Alpine field on Alaska's North Slope have chosen to develop the field using long openhole lateral wellbores. While performing above expectations, this completion practice has proven to be a difficult environment for surveillance logging. Experience in the field offers support to the following statement: Production and injection profile surveillance in horizontal wells has lagged the E&P industry's ability to drill, complete and produce these wells. This is unfortunate, for understanding the effective length of a horizontal well is important when investigating formation damage, contemplating remedial stimulation, deciding how long to drill new wells in the same reservoir, and how best to layout flood patterns.
Early attempts at logging these wells provided less than ideal results. Drilling and formation debris, abrasive formations, and to some degree wellbore geometry limited our ability to reach the full measured depth of the laterals. Stratified flow regimes, unknown flow area and debris-fouled logging tools complicated log interpretation even when the targeted depths were achieved. An assumption that the entire openhole wellbore is flowing homogeneously and is of known gauge, can lead to significant interpretation errors. Portions of openhole laterals may have significant fill or debris, effectively altering the cross sectional flow area.
An inflatable packer flowmeter tool was identified as a logging method that could address many of the aforementioned challenges. The simple goal was to meter the entire flow stream through a precisely known internal diameter. Although basket flowmeters are available to achieve the same end, these systems were not deemed sufficiently robust to use on coil and their ability to provide an adequate seal in openhole conditions was questioned.
Having decided on inflatable packer technology to address this application, the design criteria were developed. First, the geometry had to accommodate a wide range of flow. Second, it had to have an adequate pressure rating. Third, it had to be suitably robust to survive the Alpine openhole conditions.
Given this is a stationary measurement device, the packer would have to be inflated and deflated numerous times, all the while maintaining a wellbore fluid passage so as to not significantly disrupt and potentially destabilize well flow. The inflation process would also have to limit the amount of fluid, if any, that would be vented to the injection or production stream, again, to minimize well flow effects. Other considerations included the need for good reliability, the ability to run and pull the tool in arctic conditions with limited lubricator height, and the need for redundant deflation and disconnect systems.