Schlumberger

Technical Paper: New Solutions To Extend the Application Window of Horizontal Openhole Gravel Packing

Society: SPE
Paper Number: 96257
Presentation Date: 2005
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Abstract

Open hole gravel packing using the alpha/beta wave placement technique, has become the completion of choice for many operators developing fields with horizontal wells in unconsolidated sands. The interrelationships of the gravel placement parameters in these wells are well understood, and the process can be effectively modeled. However, for completions in deep and ultra deep water, difficulties limit the use of this technique.

New solutions are required to overcome the challenge of successfully packing through shale intervals, and to reliably overcome the gravel placement limitations imposed by low frac gradients. This paper presents the solutions currently in use and provides an application example using a new solution.

  • Horizontal Open Hole Gravel Pack (HZ-OHGP) Techniques
  • Successful gravel packing of long horizontal open holes has been achieved with two alternative gravel placement techniques—alternate path (A/P) and alpha/beta (A/B).

Alternate path technology was originally developed as a means of ensuring effective and complete gravel placement, even when annular blocking occurs. The early applications of this technique were for slurry packing in cased and perforated holes.[1] Since its introduction, alternative path placement has evolved to also become an option for the slurry packing of horizontal open holes, and several successful jobs have been completed (including in the Campos basin offshore Brazil). For most operators the costs of alternate path packing in long horizontal open holes have limited its application, for most operators, to wells that are considered challenging for the simpler alpha/beta placement technique.

The alpha/beta wave placement technique used for horizontal open hole gravel packing with non-viscous brines, is a characteristic of the flow of solid and liquid mixtures. During A/B wave packing, a stationary bed is deposited at the bottom of the flow path and a heterogeneous mixture of solid particles and carrier fluid (slurry) flows above it. The stationary bed at the bottom of flow path builds up and grows forward like a wave (from which the term "alpha wave" is derived). The theory behind the phenomena is that whenever the slurry velocity is less than the critical velocity, the particles in the slurry will drop and settle to the bottom bed, while at the same time some particles will be picked up from the bed.

There are several correlations for the critical velocity. The one that best describes the phenomena is the Oroscar and Turian correlation.[2] This correlation takes into account both: the hindered settling velocity and turbulent fluid eddy currents within the pipe. It considers turbulent fluid eddy velocity, as the mechanism by which energy is provided to keep solid particulate suspended in the fluid. In this argument, Υ is the dimensionless velocity of the turbulent fluid eddies within the pipe, defined as the root mean square of the three-dimensional turbulent eddy velocity fluctuations. Υ is also defined as the ratio of particulate settling velocity to critical velocity. χ is that fraction of the turbulent fluid eddies possessing a velocity larger than the particulate settling velocity.