Wells – Processes – Graveling or filter forming
Reexamination Certificate
2002-01-07
2004-06-15
Neuder, William (Department: 3672)
Wells
Processes
Graveling or filter forming
C166S051000, C166S236000
Reexamination Certificate
active
06749023
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
REFERENCE TO MICROFICHE APPENDIX
Not applicable
TECHNICAL FIELD
This invention relates to improved methods and apparatus for completing wells, and more particularly, to improved methods and apparatus for gravel packing, fracturing or frac packing by providing multiple flow paths for slurry flow via bypass tubes or conduits in the well annulus.
BACKGROUND OF THE INVENTION
The production of hydrocarbons from unconsolidated or poorly consolidated formations may result in the production of sand along with the hydrocarbons. The presence of formation fines and sand is disadvantageous and undesirable in that the particles abrade pumping and other producing equipment and reduce the fluid production capabilities of the producing zones in the wells.
Particulate material (e.g., sand) may be present due to the nature of a subterranean formation and/or as a result of well stimulation treatments wherein proppant is introduced into a subterranean formation. Unconsolidated subterranean zones may be stimulated by creating fractures in the zones and depositing particulate proppant material in the fractures to maintain them in open positions.
Gravel packs with sand screens and the like have commonly been installed in wellbores penetrating unconsolidated zones to control sand production from a well. The gravel packs serve as filters and help to assure that fines and sand do not migrate with produced fluids into the wellbore.
Cased-hole gravel packing requires that the perforations or fractures extending past any near-wellbore damage as well as the annular area between the outside diameter (OD) of the screen and the inside diameter (ID) of the casing be tightly packed with gravel. See Brochure: “Sand Control Applications,” by Halliburton Energy Services Inc., which is incorporated herein by reference. The open-hole gravel-pack completion process requires only that the gravel be tightly packed in the annulus between the OD of the screen and the openhole.
Several techniques to improve external gravel-pack placement, either with or without fracture stimulation, have been devised. These improved techniques can be performed either with the gravel-pack screen and other downhole equipment in place or before the screen is placed across the perforations. The preferred packing methods are either 1) prepacking or 2) placing the external pack with screens in place, combined with some sort of stimulation (acid-prepack), or with fracturing or acidizing. The “acid-prepack” method is a combination stimulation and sand control procedure for external gravel-pack placement (packing the perforations with gravel). Alternating stages of acid and gravel slurry are pumped during the treatment. The perforations are cleaned and then “prepacked” with pack sand.
Combination methods combine technologies of both chemical consolidation and mechanical sand-control. Sand control by chemical consolidation involves the process of injecting chemicals into the naturally unconsolidated formation to provide grain-to-grain cementation. Sand control by resin-coated gravel involves placing a resin-coated gravel in the perforation tunnels. Resin-coated gravel is typically pumped as a gel/gravel slurry. Once the resin-coated gravel is in place, the resin sets up to form a consolidated gravel filter, thereby removing the need for a screen to hold the gravel in place. The proppant pumped in a frac treatment may be consolidated into a solid (but permeable) mass to prevent proppant-flow back without a mechanical screen and to prevent formation sand production. U.S. Pat. No. 5,775,425, which is incorporated herein by reference, discloses an improved method for controlling fine particulates produced during a stimulation treatment, including the steps of providing a fluid suspension including a mixture of a particulate coated with a tackifying compound and pumping the suspension into a formation and depositing the mixture within the formation.
A combined fracturing and gravel-packing operation involves pumping gravel or proppant into the perforations at rates and pressures that exceed the parting pressure of the formation. The fracture provides stimulation and enhances the effectiveness of the gravel-pack operation in eliminating sand production. The fracturing operation produces some “restressing” of the formation, which tends to reduce sanding tendencies. See Brochure: “STIMPAC Service Brochure,” by Schlumberger Limited, which is incorporated herein by reference. The high pressures used during fracturing ensure leakoff into all perforations, including those not connected to the fracture, packing them thoroughly. Fracturing and gravel packing can be combined as a single operation while a screen is in the well.
“Fracpacking” (also referred to as “HPF,” for high-permeability fracturing) uses the tip-screenout (TSO) design, which creates a wide, very high sand concentration propped fracture at the wellbore. See M. Economides, L. Watters & S. Dunn-Norman,
Petroleum Well Construction
, at 537-42 (1998), which is incorporated herein by reference. The TSO occurs when sufficient proppant has concentrated at the leading edge of the fracture to prevent further fracture extension. Once fracture growth has been arrested (assuming the pump rate is larger than the rate of leakoff to the formation), continued pumping will inflate the fracture (increase fracture width). The result is short but exceptionally wide fractures. The fracpack can be performed either with a screen and gravel-pack packer in place or in open casing using a squeeze packer. Synthetic proppants are frequently used for fracpacks since they are more resistant to crushing and have higher permeability under high confining stress.
In a typical gravel pack completion, a screen is placed in the wellbore and positioned within the zone which is to be completed. The screen is typically connected to a tool which includes a production packer and a crossover port, and the tool is in turn connected to a work string 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 port whereby it flows into the annulus between the screen and the wellbore and into the perforations, if applicable. The liquid forming the slurry leaks off into the subterranean zone and/or through the screen which is sized to prevent the sand in the slurry from flowing therethrough. As a result, the sand is deposited in the annulus around the screen whereby it forms a gravel pack. The size of the sand in the gravel pack is selected such that it prevents formation fines and sand from flowing into the wellbore with produced fluids.
Circulation packing (sometimes called “conventional” gravel-packing) begins at the bottom of the screen and packs upward along the length of the screen. Gravel is transported into the annulus between the screen and casing (or the screen and the open hole) where it is packed into position from the bottom of the completion interval upward. The transport fluid then returns to the annulus through the washpipe inside the screen that is connected to the workstring.
Horizontal gravel packs can be placed in open or cased hole completions of varying lengths. The alpha/beta wave approach has been used extensively for gravel packing horizontal wells. See Dickinson, W. et al.: “A Second-Generation Horizontal Drilling System,” paper 14804 presented at the 1986 IADC/SPE Drilling Conference held in Dallas, Tex., February 10-12; Dickinson, W. et al.: “Gravel Packing of Horizontal Wells,” paper 16931 presented at the 1987 SPE Annual Technical Conference and Exhibition held in Dallas, Tex., September 27-29; and M. Economides, L. Watters & S. Dunn-Norman,
Petroleum Well Construction
, at 533-34 (1998), which are all incorporated herein by reference. This method is a two-step procedure, which includes an alpha wave sand deposition in one direction and a beta wave sand deposition in the opposite direction. Water
Nguyen Philip D.
Sanders Michael W.
Halliburton Energy Service,s Inc.
Neuder William
Schroeder Peter V.
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