Wells – Processes – Providing porous mass of adhered filter material in well
Reexamination Certificate
2000-02-15
2001-10-16
Suchfield, George (Department: 3672)
Wells
Processes
Providing porous mass of adhered filter material in well
C166S278000, C166S295000, C166S300000, C166S309000
Reexamination Certificate
active
06302207
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improved methods of completing wells in unconsolidated subterranean zones, and more particularly, to improved methods of completing such wells whereby the migration of sand with the fluids produced therefrom is prevented.
2. Description of the Prior Art
Oil and gas wells are often completed in unconsolidated formations containing loose and incompetent sand which migrates with fluids produced by the wells. The presence of formation sand in the produced fluids is disadvantageous and undesirable in that the particles abrade pumping and other producing equipment and reduce the fluid production capabilities of producing zones in the wells. Heretofore, unconsolidated subterranean producing zones have been completed by forming gravel packs in the well bore adjacent the producing zones. The gravel packs serve as filters and function to prevent formation sand from migrating with produced fluids into the well bores.
In a typical gravel pack completion, a screen is placed in the well bore and positioned within the unconsolidated subterranean producing zone which is to be completed. The screen is typically connected to a tool which includes a production packer and a crossover, and the tools is in turn connected to a work or production string. A particulate material which is usually graded sand, often referred to in the art as gravel, is pumped in a slurry down the work or production string and through the crossover whereby it flows into the annulus between the screen and the well bore. The liquid forming the slurry leaks off into the subterranean zone and/or through the screen which is sized to prevent the particulate material in the slurry from flowing therethrough. As a result, the particulate material is deposited in the annulus around the screen whereby it forms a gravel pack. The size of the particulate material in the gravel pack is selected such that it prevents formation sand from flowing into the well bore with produced fluids.
A problem which is often encountered in forming gravel packs, particularly gravel packs in long and/or deviated unconsolidated producing zones, is the formation of particulate material bridges in the annulus. That is, non-uniform packing of the particulate material in the annulus between the screen and the well bore often occurs as a result of the loss of carrier liquid into high permeability portions of the subterranean zone. This, in turn, causes the formation of particulate material bridges in the annulus before all of the particulate material has been placed. The particulate material bridges block further flow of the slurry through the annulus which leaves voids below the bridges. When the well is placed on production, the flow of produced fluids is concentrated through the voids in the gravel pack which soon causes the screen to be eroded and the migration of formation sand with the produced fluids to result.
Thus, there are needs for improved methods of completing wells utilizing gravel packs whereby voids in the gravel packs do not occur or are eliminated prior to when the wells are placed on production.
SUMMARY OF THE INVENTION
The present invention provides improved methods of completing subterranean producing zones containing unconsolidated sand which meet the needs described above and overcome the deficiencies of the prior art. A method of this invention is basically comprised of the steps of placing a sand screen in the zone to be completed, isolating the annulus between the screen and the well bore in the zone, introducing a mixture of particulate material and foam forming pellets into the annulus between the sand screen and the well bore whereby the mixture of particulate material and foam forming pellets is packed into the annulus and activating the foam forming pellets whereby foam is formed in the annulus which expands and solidifies therein thereby eliminating voids and strengthening the resulting permeable pack.
An alternate embodiment of the methods of the present invention basically comprises the steps of placing a sand screen in the subterranean zone to be completed, isolating the annulus between the sand screen and the well bore in the zone, and then introducing a plurality of solidified open cell foam pieces into the annulus between the sand screen and the well bore whereby the foam pieces are uniformly packed into the annulus. The open cells of the foam pieces are of a size such that the unconsolidated sand is prevented from entering the cell but produced fluids can flow therethrough. The solidified open cell foam pieces do not readily form bridges in the annulus between the sand screen and the well bore and can be uniformly packed in the annulus. Optionally, particulate solids can be introduced into the annulus along with the open cell foam pieces. Also, the open cell foam pieces and the particulate solids, if used, can be coated with a hardenable resin which upon hardening consolidates the pack formed into a permeable mass. Additionally, foam forming pellets can be included with the open cell foam pieces and solid particles, if used, which upon activation expands and solidifies in the pack.
It is, therefore, a general object of the present invention to provide improved methods of completing unconsolidated subterranean producing zones.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention provides improved methods of completing unconsolidated subterranean zones penetrated by well bores. In accordance with the improved methods of the invention, conventional gravel pack forming tools well known to those skilled in the art are utilized. That is, a conventional sand screen is placed in the subterranean zone to be completed. The sand screen is connected to a conventional cross-over and production packer which is in turn connected to a production string or work string. The production packer is set in the well which isolates the annulus between the sand screen and the well bore. Thereafter, a mixture of particulate material is introduced into the annulus by way of the cross-over so that the particulate material is packed into the annulus.
In one embodiment of the present invention, the particulate material utilized is a mixture of graded sand or other similar material such as ceramic beads, plastic beads, glass beads and the like and foam forming pellets. After the mixture of particulate material and form forming pellets is placed in the annulus, the foam forming pellets are activated whereby foam is formed in the annulus which expands and solidifies therein thereby eliminating voids and strengthening the resulting permeable particulate material pack whereby it effectively prevents unconsolidated formation sand from flowing into the well bore with produced fluids.
The particulate material utilized in accordance with the present invention is preferably graded sand which is sized based on a knowledge of the size of the formation fines and sand in the unconsolidated zone to prevent the formation fines and sand from passing through a permeable pack of the graded sand. The sand generally has a particle size in the range of from about 10 to about 70 mesh, U.S. Sieve Series. Preferred sand particle size distribution ranges are one or more of 10-20 mesh, 20-40 mesh, 40-60 mesh or 50-70 mesh, depending on the particle size and distribution of the formation fines and sand to be screened out by the particulate material.
A variety of foam forming pellets can be utilized which are activated by the heat in the subterranean zone, by steam injection or other suitable techniques. The foam forming pellets are generally comprised of a thermoplastic polymer containing a foaming agent. When the pellets are activated, the thermoplastic polymer is liquefied and foamed by the foaming agent. Examples of foam forming beads which can be utilized in accordance with this inve
Dewprashad Brahmadeo T.
Dusterhoft Ronald D.
Nguyen Philip D.
Schreiner Kirk L.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Kent Robert A.
Suchfield George
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