Technology Update

Some material in this article has been previously published in papers SPE 116474 and 116476, presented at the 2008 SPE Annual Technical Conference and Exhibition, Denver, 21-24 September. The figures for this article originally were published in paper SPE 116474.

Despite the credit crunch, worldwide subsea activity is still forecast to grow rapidly. In its recent 2009 subsea forecast, Infield Systems indicated that subsea drilling and completion expenditure will more than double to USD 80.5 billion between 2009 and 2013, from a total of USD 31.9 billion during the period from 2003 to 2007 (Infield 2009). Coupled with the increase in expenditure, Infield forecasts 3,222 subsea wells to be installed from 2009 through 2013, vs. 1,958 wells installed between 2004 and 2008. A large percentage of these wells will require sand control.

In market-share terms, Infield forecasts that Africa will remain the largest sector, representing 29% of the forecast capital expenditures between 2009 and 2013, followed by North America (25%), Latin America (19%), and Europe (13%). The remaining spending will be spread between Australasia, Asia, and the Middle East and Caspian region.

Despite this growth in the number of subsea wells, the expense of subsea well intervention often leads to insufficient reservoir information for accurately understanding reservoir connectivity, drainage, and flow assurance. This has led to an industry need for real-time data from sensors located on the sandface. For those wells requiring sand control, an additional constraint is that sandface sensors must be deployed on a separate completion run.

Reservoir-Monitoring Challenges in Dual-Stage Completions

Most wells with sand control use completion components that are deployed in multiple stages. This presents a challenge to achieving measurements from monitoring equipment located in the lowest stage of the completion because sensor power and data are required to be transferred across the junction between the lower and upper completion stages.

Consequently, reservoir monitoring in dual-stage completions has generally been limited to measurements of pressure and temperature near the production packer in the upper completion. These types of sensors cannot distinguish the downhole conditions of individual zones. Placing the sensors at the sandface, where the fluid enters, would take permanent monitoring to the next level because it enables operators to better understand the flow from each producing zone. This has now been achieved by an operator in southeast Asia who has deployed the Schlumberger WellWatcher Flux digital-sensor array system onto the screens of six openhole gravel packs in a subsea gas field. Data from those sensors has been transmitted to shore during cleanup, with the output used to make interpretations of permeability and cleanup efficiency for each producing zone.

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