New Tool Designs For High Rate Gravel Pack Operations
Authors: Ross Colby M. 
Published: October 2008

Fracturing of the wellbore to improve hydrocarbon recovery has been a universally accepted practice in the oilfield. The fracturing procedures reduce skin by breaking through or bypassing near wellbore damage that inhibits production. In loosely consolidated formations, a propped fracture can reduoe fluid velocity in the near wellbore region, which subsequently reduces fines migration that can plug the wellbore. Fracturing also provides highly conductive paths for gas and oil production.

Gravel packing is another operation that is often needed during a well?s productive cycle. When a highly conductive fracture is created before a gravel packing operation is run, it has been found that well productivity increases. Performing the operations separately, however, dimishes the productivity gains because of formation damage that can occur between completion operations.

A method of gravel packing that includes a tip-screen out- design fracturing procedure, performed with thegravel pack packer, screen, and blank in the hole, was proposed to allow the procedures to be performed simultaneously. This paper will describe the various types of gravel packing tools that are currently in use, their specific application, and a new series of gravel packing tools that was developed to resolve the difficulties that arose when the operations of fracturing and gravel packing were combined. Also discussed is the need that arose for tools that could sustain high flow rates in small casing diameters.

Test results will be used to provide acceptable flow rates for different bore sizes.

INTRODUCTION

Many fracturing operations require fluids to be pumped into the fractures at very high rates and high pressures, followed by a proppant such as sand to hold the fracture open as soon as the pump is stopped or the fluid leaks off into the formation.? Because the proppant-laden fluids are very erosive and fracture pressures exceed normal gravel pack and formation operating pressures, specialized completion equipment is required to help prevent tool damage from occurring on the surface or downhole.

Gravel packing is typically performed at rates of.5 to 5 bbl/min. The perforation tunnels and the screen annulus can be tightly packed with sand at these rates. If the rates and pressures are increased, a small fracture can perforation tunnels and screen annulus are packed with sand. When this operation takes place, productivity increases can be obtained. If the fracturing operation is completed before the gravel pack operation is performed, however, some of the productivity gains can be reduced as a result of formation damage that occurs between the time when the stimulation packer is pulled from the well and the gravel pack packer/screen assembly is made up and run. This damage can result from such conditions as addition of fluid loss additives, which are regularly needed during these operations, fluid incompatibilities with the formation, casing scale, and contamination from solids in the completion fluid.

The combined gravel packing and small fracturing procedure (frac pack) offered a viable solution to the problems of formation damage that occurred when the operations were run separately. In addition, the reduction in the number of trips into the wellbore reduces operational time and costs.