Wells – Processes – Specific propping feature
Reexamination Certificate
2000-05-25
2002-04-02
Tsay, Frank (Department: 3672)
Wells
Processes
Specific propping feature
C166S308400, C507S924000
Reexamination Certificate
active
06364018
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to subterranean formation treatments and, more specifically, to hydraulic fracturing treatments for subterranean formations. In particular, this invention relates to use of relatively lightweight and/or substantially neutrally buoyant particles as proppant material in hydraulic fracturing treatments.
2. Description of the Related Art
Hydraulic fracturing is a common stimulation technique used to enhance production of fluids from subterranean formations. In a typical hydraulic fracturing treatment, fracturing treatment fluid containing a solid proppant material is injected into the formation at a pressure sufficiently high enough to cause the formation or enlargement of fractures in the reservoir. During a typical fracturing treatment, proppant material is deposited in a fracture, where it remains after the treatment is completed. After deposition, the proppant material serves to hold the fracture open, thereby enhancing the ability of fluids to migrate from the formation to the well bore through the fracture. Because fractured well productivity depends on the ability of a fracture to conduct fluids from a formation to a wellbore, fracture conductivity is an important parameter in determining the degree of success of a hydraulic fracturing treatment.
Hydraulic fracturing treatments commonly employ proppant materials that are placed downhole with a gelled carrier fluid (e.g., aqueous-based fluid such as gelled brine). Gelling agents for proppant carrier fluids may provide a source of proppant pack and/or formation damage, and settling of proppant may interfere with proper placement downhole. Formulation of gelled carrier fluids usually requires equipment and mixing steps designed for this purpose.
SUMMARY OF THE INVENTION
In the disclosed method, the application of relatively lightweight and/or substantially neutrally buoyant particulate material as a fracture proppant particulate advantageously may provide for substantially improved overall system performance in hydraulic fracturing applications. By “relatively lightweight” it is meant that a particulate has a density that is substantially less than a conventional proppant particulate material employed in hydraulic fracturing operations, e.g., sand or having a density similar to these materials. By “substantially neutrally buoyant”, it is meant that a particulate has a density sufficiently close to the density of a selected ungelled or weakly gelled carrier fluid (e.g., ungelled or weakly gelled completion brine, other aqueous-based fluid, or other suitable fluid) to allow pumping and satisfactory placement of the proppant particulate using the selected ungelled or weakly gelled carrier fluid. For example, urethane resin-coated ground walnut hulls having a specific gravity of from about 1.25 to about 1.35 grams/cubic centimeter may be employed as a substantially neutrally buoyant proppant particulate in completion brine having a density of about 1.2. It will be understood that these values are exemplary only. As used herein, a “weakly gelled” carrier fluid is a carrier fluid having minimum sufficient polymer, viscosifier or friction reducer to achieve friction reduction when pumped down hole (e.g., when pumped down tubing, work string, casing, coiled tubing, drill pipe, etc.), and/or may be characterized as having a polymer or viscosifier concentration of from greater than about 0 pounds of polymer per thousand gallons of base fluid to about 10 pounds of polymer per thousand gallons of base fluid, and/or as having a viscosity of from about 1 to about 10 centipoises. An ungelled carrier fluid may be characterized as containing about 0 pounds per thousand gallons of polymer per thousand gallons of base fluid.
Advantageously, in one embodiment use of substantially neutral buoyant particulate material may eliminate the need for gellation of carrier fluid, thus eliminating a source of potential proppant pack and/or formation damage. Furthermore, a relatively lightweight particulate material may be easier to place within a targeted zone due to lessened settling constraints. Elimination of the need to formulate a complex suspension gel may mean a reduction in tubing friction pressures, particularly in coiled tubing and in the amount of onlocation mixing equipment and/or mixing time requirements, as well as reduced costs. Furthermore, when treated to have sufficient strength (e.g., by substantially filling the permeable porosity of a porous particle with resin or hardener), the disclosed relatively lightweight proppant particles may be employed to simplify hydraulic fracturing treatments performed through coil tubing, by greatly reducing fluid suspension property requirements. Downhole, a much reduced propensity to settle (as compared to proppant particulates) may be achieved. In this regard, the disclosed substantially neutral buoyancy proppant material may be advantageously employed in any deviated well having an angle of deviation of between about 0 degree and about 90 degrees with respect to the vertical. However, in one embodiment, the disclosed particulate material may be advantageously employed in horizontal wells, or in deviated wells having an angle with respect to the vertical of between about 30 degrees and about 90 degrees, alternatively between about 75 degrees and about 90 degrees. Thus, use of the disclosed relatively lightweight and/or substantially neutrally buoyant particulate materials disclosed herein may be employed to achieve surprising and unexpected improvements in fracturing methodology, including reduction in proppant pack and/or formation damage, and enhancement of well productivity.
In another embodiment, protective and/or hardening coatings, such as resins described elsewhere herein may be selected to modify or customize the specific gravity of a selected base particulate proppant material, e.g., ground walnut hulls, etc. Modification of particulate specific gravity (i.e., to have a greater or lesser specific gravity) may be advantageously employed, for example, to provide proppant particulates of customized specific gravity for use as a substantially neutrally buoyant particulate with a variety of different weight or specific gravity carrier fluids. In yet another embodiment, protective and/or hardening-type coatings may be optionally curable to facilitate proppant pack consolidation after placement. In this regard, curable resins are know to those of skill in the art, and with benefit of this disclosure may be selected to fit particular applications accordingly.
The disclosed relatively lightweight and/or substantially neutrally buoyant particulate proppant materials may be employed with carrier fluids that are gelled, non-gelled, or that have a reduced or lighter gelling requirement as compared to carrier fluids employed with conventional fracture treatment methods. In one embodiment employing one or more of the disclosed substantially neutrally buoyant particulate materials and a brine carrier fluid, mixing equipment need only include such equipment that is capable of (a) mixing the brine (dissolving soluble salts), and (b) homogeneously dispersing in the substantially neutrally buoyant particulate material.
In one embodiment, a substantially neutrally buoyant particulate proppant material may be advantageously pre-suspended and stored in a storage fluid (e.g. brine of near or substantially equal density), and then pumped or placed downhole as is, or diluted on the fly.
In one respect, disclosed is a hydraulic fracturing method for a well penetrating a subterranean formation, including introducing a relatively lightweight and/or substantially neutral density particulate proppant material into the well. Individual particles of the particulate material optionally may have a shape with a maximum length-based aspect ratio of equal to or less than about 5. Individual particles may also be optionally coated with protective materials such as resins and/or hardeners, for example, “2AC” phenol formaldehyde hardener from BORDE
Brannon Harold D.
Rickards Allan R.
Stephenson Christopher J.
BJ Services Company
O'Keefe Egan & Peterman, LLP
Tsay Frank
LandOfFree
Lightweight methods and compositions for well treating does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lightweight methods and compositions for well treating, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lightweight methods and compositions for well treating will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2830658