Gravel Pack Tool

Gravel packs are used to prevent sand from flowing into the well while still allowing continuous rapid production. The construction consists of a slotted or perforated liner placed in the well and surrounded by small-sized gravel. The well is enlarged by underreaming at the point where the gravel is packed.

During placement or the life of the well, voids can occur whereby sand has an easy ingress route; this does not normally happen where resin bonded packs are used. Additionally, sand filling the interstices between the pieces of gravel will reduce its porosity and hence permeability, thus reducing production. This problem may occur as the well's age increases.

Description

In the case of voids, a gravel pack log provides an analysis of the areas in the pack that need to be replaced before the well is placed either on production or during continued production. Sand blocking of the pack, which can potentially reduce production, can also be detected providing the information that it is a well construction rather than a reservoir problem that is reducing yield.

The gravel pack tool consists of a scintillation gamma section with a source/ feedthrough sub attached to the bottom. The source sub accepts a gamma source of up to 150mci (5.5gbq) of caesium 137. The tool can be used at the bottom of a toolstring or with other tools fitted below it. In either case the tool should be run centralised.

In use, the tool can be regarded as an omni-directional density tool. Gamma rays from the source are detected at a rate dependent upon the variation of the total density of a volume of material, with a roughly spherical volume, centred on the tool measuring point. When examining the condition of a gravel pack, the variation is normally due to changes of pack porosity.

Features

• Detection of Voids in the Gravel Pack
• Monitoring of changes in porosity with time
• Combinable with other Ultrawire™ tools