Gravel Pack Joint
Some oil wells will produce sand along with the production of oil. This unwanted sand production is often controlled with screens, slotted liners, and also the use of gravel packs. A gravel pack is the term used when a column of sand is placed between the sand controlling equipment and the sand formation down hole. The silica sand (controlled grain size) is mixed with a liquid and the slurry is pumped down the well to fill the annulus required. The gravel pack acts as a filter media, which will filter some of the fines before it reaches the sand control equipment. This process has reduced the amount of sand produced at surface on some wells.
The sizing of the silica sands is determined from a sieve analysis created from the formation sands, as well as the filter size and type of sand control equipment to be chosen to be run in conjunction with the gravel pack. Once the size is determined it is pumped down the well on the outside of the sand control equipment. On horizontally drilled wells, the pumping action does not place the sand evenly in the annulus evenly after well angles greater than 65°. Placement in wells with greater angles than 65° will typically place the silica sands on the bottom of the annulus and not in the top area.
The Gravel Pack Joint (GPJ) is manufactured on surface before running in the well. The purpose of the GPJ eliminates the pumping of the silica sands into the well resulting in poor or improper placements of the silica sands. The GPJ will also contain one more sand control media then the gravel pack being pumped. Pumped gravel packs give control with the silica sand and the sand control equipment (2 medias). The GPJ has an outer slotted liner and an inner slotted liner, each having different medias, and the silica sand (3 medias). The GPJ is manufactured with the inner slotted liner containing a slot size designed around containing the small formation sands. The outside slotted liner’s slot size is designed around containing the large formation sands. These 2 slot sizes are also designed to contain the silica sands that will be placed and contained between the 2 slotted liners. The GPJ assembly will contain a smaller liner (5 ½”) inside a larger liner (7”) held together with special subs, and the silica sand are then placed between the 2 liners. Assembly is done in the vertical position to eliminate any void sand placements.