For offshore developments it is anticipated that several wells will be completed using gravel packed sand screens divided by long blank pipe sections. Open-hole gravel packing has routinely been used as a sand control method in long horizontal wells. However handling long blank pipe sections represents a challenge. The length of blank pipe section could be 600 meters or longer. In such cases, the chart of the surface pump pressure versus the pumping time is different when compared with a typical profile from a horizontal gravel pack in a section without blank pipe. Typically, gravel pack sand moves in from heel to toe of a well for roughly half of the cross section area (alpha wave) followed by a final placement of the remaining part of the annulus from toe to heel (beta wave).
Since there is no flow through the pipe in the blank pipe section, the beta wave does not exist here, and its absence complicates the gravel placement in the heel region of the reservoir. On the upstream side of the blank pipe, the slurry is dehydrated through the screen. This slows down the rate in the area adjacent to the blank pipe where in turn a new alpha wave adjacent to the blank pipe starts. This process appears to continue until the majority of the area open to flow above the alpha wave adjacent to the blank pipe has been filled in. The beta wave adjacent to the screen on the upstream side of the blank pipe then continues normally.
The paper describes in detail a mechanistic model based on experiments which predicts the phenomena discussed above. This model for gravel placement has been validated both qualitatively and quantitatively with both laboratory and the North Sea field Heidrun data.