Gravel packing long horizontal wells presents many challenges to completion operations. The accurate calculation of Alpha wave dune height under dynamic wellbore conditions is on the top of the list. Alpha wave dune height is critical during job planning and the afterward successful gravel placement execution. Excessive Alpha wave dune height is the cause of many early time screenout and job failures. The job parameters, including wellbore geometry, pump rate, leakoff and leakoff control, fluid density and viscosity, gravel particle size and geometry, liteProp and conventional gravel, wellbore temperature profile, bottomhole pressure distribution, will all have impact on Alpha wave height.
This paper investigates and summarizes several particle transfer models, analytical and empirical ones, their applications in Alpha wave dune height calculations, their limitations and effective application windows. The paper also provides dynamic Alpha wave height calculation methodology to account for dynamic bottomhole conditions, especially the fluid leakoff to formation and to screen wash pipe annulus, bottomhole in-situ gravel concentration, and their impact on Alpha wave dune height calculation. The sensitivities of these models under different job conditions are also studied.
Several job designs and application histories are presented in the paper to demonstrate the application of different particle transport models. Guidelines are provided for operators to make proper adjustment when an undesired condition is present during gravel placement.
Introduction
Horizontal well openhole gravel packing is an effective sand control technique. Although the process itself is complex, the gravel placement can be simplified as Alpha-Beta wave packing. Job design and job planning play a critical role in the successful execution of gravel placement. This is especially the case for wells under extreme conditions, such as deep and ultra deep water, long and ultra long horizontal wellbore sections, and unconsolidated formations with low fracture gradient reservoirs.1–7
Gravel packing is a process of particle transfer, a dynamic process of particles being deposited and picked up, being transported forward. Particle transfer in horizontal and deviated pipes have long been research subjects, dealing with particle transport in mining industry, borehole cleaning and gravel packing in oil/gas industry. Different particle transfer models, both analytical and empirical ones have been published and each with its test conditions and applicable window to the field with conditions similar to conditions tested.
Particle Transfer Models and Critical Velocity
In horizontal pipes the solid-liquid flow can occur in a number of different flow regimes. The common flow regimes are pseudo-homogeneous suspensions, heterogeneous suspensions, heterogeneous suspensions with sliding beds, and stationary beds. Instead of studying the detail behavior of each flow regime, the critical or equilibrium velocities are the focal points of researches. Several models were published and adapted in the area of gravel packing.
The Model of Gruesbeck et al.
Gruesbeck et al.8 pioneered the studying of gravel packing deviated and horizontal wellbores. The equilibrium velocity model they developed was later used by different authors in publications.
The critical velocity model was a curve fitting from experimental data, when plotted observed critical velocity vs calculated critical velocity.
