Wells – Processes – Placing fluid into the formation
Reexamination Certificate
2000-05-25
2004-06-15
Tsay, Frank (Department: 3672)
Wells
Processes
Placing fluid into the formation
C166S280100, C166S305100
Reexamination Certificate
active
06749025
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to methods and compositions useful for controlling sand production from subterranean formations. In particular, this invention relates to use of relatively lightweight and/or substantially neutrally buoyant particles as particulate material in sand control methods such as gravel packing, frac packs, etc.
2. Description of the Related Art
Production of particulate solids with subterranean formation fluids is a common problem. The source of these particulate solids may be unconsolidated material from the formation, proppant from a fracturing treatment and/or fines generated from crushed fracture proppant. Production of solid proppant material is commonly known as “proppant flowback.” In addition to causing increased wear on downhole and surface production equipment, the presence of particulate materials in production fluids may also lead to significant expense and production downtime associated with removing these materials from wellbores and/or production equipment. Accumulation of these materials in a wellbore may also restrict or even prevent fluid production. In addition, loss of proppant due to proppant flowback may also reduce conductivity of a fracture pack.
In an effort to control or prevent production of formation or proppant materials, many methods have been developed. Included among these are those methods commonly referred to as gravel packing and frac packs. These methods commonly employ particulate materials that are placed downhole with a gelled carrier fluid (e.g., aqueous-based fluid such as gelled brine). Gelling agents for gelling carrier fluids may provide a source of formation damage. 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 sand control particulate advantageously may provide for substantially improved overall system performance in particulate-based sand control methods such as gravel packing and frac packing. By “relatively lightweight” it is meant that a particulate has a density that is substantially less than a conventional particulate material employed in particulate-based sand control methods, e.g., conventional gravel packing gravel, 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 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 sand control 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 buoyancy particulate material may eliminate the need for gellation of carrier fluid, thus eliminating a source of potential formation damage. Furthermore, use of a relatively lightweight particulate material typically means that a much reduced mass of relatively lightweight particulate material is required to fill an equivalent volume than is required with conventional sand control particulates used, for example, for gravel packing purposes. 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 on-location 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 sand control particles may be employed to simplify sand control treatments performed through coil tubing, by greatly reducing fluid suspension property requirements. Downhole, with a much reduced propensity to settle (as compared to conventional sand control particulates), more efficient packing particularly in highly deviated or horizontal wellbore sections) may be achieved. In this regard, the disclosed substantially neutral buoyancy particulate 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.
Elimination of the need to formulate a suspension gel advantageously may mean a reduction in tubing friction pressures (particularly in coiled tubing), a reduction in the amount of on-location mixing equipment and/or mixing time requirements, as well as reduced costs. 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 sand control methodology and results, including reduction in 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 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 sand control 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 sand control particulate 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 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 sand control methods, e.g., conventional gravel packing 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 material may be advantageously pre-suspended and stored in a storage fluid (e.g., brine of near or substantially equal density),
Brannon Harold D.
Rickards Allan R.
Stephenson Christopher J.
BJ Services Company
O'Keefe Egan & Peterman, LLP
Tsay Frank
LandOfFree
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