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Acid switchable frac-screens for sand control

IP.com Disclosure Number: IPCOM000241488D
Publication Date: 2015-May-05
Document File: 2 page(s) / 15K

Publishing Venue

The IP.com Prior Art Database

Abstract

In this invention, we report novel designs of frac-screens for sand control during oil and gas production. These frac-screens form a temporary plug that can be switched to form a filtration media by treating with an organic acid, or an acidized ethylene glycol. These frac-screens are made of beaded-screens (bonded stainless steel beads) in conjunction with selectively dissolvable thermoset epoxy. In one embodiment, a beaded-screen is infused and cured with selectively dissolvable thermoset epoxy to form a solid composite plug. In another embodiment, discs of the dissolvable thermoset are placed on top and/or bottom of a beaded-screen, or sandwiched in between two beaded-screens acting as the barrier. Another embodiment of the frac-sreen has beaded-screen infused with epoxy resin, and excess layers of cured thermoset epoxy in form of discs providing further protection and strength on top, and/or bottom of the screen. Similar designs in conjunction with the selectively dissolvable thermoset could be envisioned with other metallic screens typically used for sand control. The dissolution rate of the thermoset epoxy can be controlled by varying the concentration of the acidic medium. The thermoset polymer system in current invention is ductile, load-bearing, and a cost-effective option over currently used corrodable metal plates. This epoxy based thermoset material provides an added advantage of working as a “switch”, since the degradation takes place ONLY in selective acidic solution, while remaining unaffected by most downhole formation fluids. The selectively dissolvable thermoset epoxy is expected to cost only a fraction of the corrodable metal plate. • The thermoset epoxy, in its unfilled, neat state exhibits a flexural strength and modulus of 100 MPa and 3 GPa, and a tensile strength and modulus of 73 MPa and 3.4 GPa, respectively, with 6 of tensile elongation before its breakage. • A density of 1.2 g/cc, and a typical commercial epoxy glass transition temperature (Tg) is identified as 113C (235°F). Thus a load bearing property of the current thermoset material can conveniently be utilized towards its entire glassy region, e.g., until 100C (212F). Further extension of the glassy region is possible, and a consequent extension in service temperature can further be expected. • Some non-limiting embodiments of the inventions are as follows: a. A composite plug, as designed for sand control can be embodied with a combination of beaded-screen (Figure 1) and in conjunction with a selectively dissolvable thermoset epoxy matrix (Figure 2). The infused and cured thermoset, when required, can be dissolved and/or disintegrated away by treating the plug with an organic acid or acidized ethylene glycol to create a filtration media. b. A plug, as designed for sand control can be assembled with a beaded-screen and molded discs of a selectively dissolvable thermoset epoxy either on top and/or bottom of a beaded-screen (Figure 3). A sandwiched structure of epoxy wafer in between two beaded-screens can further be envisioned, where once required the epoxy barrier can be wiped off by treating with an organic acid or acidized ethylene glycol. c. A plug design that is a combination of (a) and (b). d. A plug, as designed for sand control embodied with metallic filtration screens and a selectively dissolvable thermoset epoxy. The infused epoxy resin, wherein the metal screen acting as a scaffold, can be cured to form a composite structure. Alternatively the molded discs of thermosets can be assembled with the screens forming a layered structure. When desired, an organic acid or acidized ethylene glycol treatment dissolves away the epoxy to create a filtration media. • Dissolution behavior of a selectively dissolvable unfilled thermoset epoxy are exemplified as follows: a. Depending on the thermal treatment, as observed from 60C to 100C, a 25 acetic acid solution in water dissolves the thermoset leaving behind less than 10 weight residue in couple of hours to a day, respectively. b. Depending on the concentration in water, a 10 to 50 acetic acid solution dissolves the thermoset leaving behind less than 10 weight residues within an hour to 8 hours, respectively when treated at 100°C. c. Depending on thermal treatment, a 10 HCl in ethylene glycol also disintegrates the thermoset within couple of hours. d. Physical, chemical and mechanical properties of the selectively dissolvable epoxy was found to be unaffected when treated at 90°C for 4 hours separately, in CL-7 type motor oil, in ethylene glycol, a 3 KCl solution, and in 19.2 ppg ZnBr2/ CaBr2 solution (HYCAL III). Some surface pitting was observed under the same treatment in 34 concentrated HCI.

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Acid switchable frac-screens for sand control

In this invention, we report novel designs of frac-screens for sand control during oil and gas production. These frac-screens form a temporary plug that can be switched to form a filtration media by treating with an organic acid, or an acidized ethylene glycol. These frac-screens are made of beaded-screens (bonded stainless steel beads) in conjunction with selectively dissolvable thermoset epoxy. In one embodiment, a beaded-screen is infused and cured with selectively dissolvable thermoset epoxy to form a solid composite plug. In another embodiment, discs of the dissolvable thermoset are placed on top and/or bottom of a beaded-screen, or sandwiched in between two beaded-screens acting as the barrier. Another embodiment of the frac-sreen has beaded-screen infused with epoxy resin, and excess layers of cured thermoset epoxy in form of discs providing further protection and strength on top, and/or bottom of the screen. Similar designs in conjunction with the selectively dissolvable thermoset could be envisioned with other metallic screens typically used for sand control. The dissolution rate of the thermoset epoxy can be controlled by varying the concentration of the acidic medium. The thermoset polymer system in current invention is ductile, load-bearing, and a cost-effective option over currently used corrodable metal plates. This epoxy based thermoset material provides an added advantage of working as a “switch”, since the degradation takes place ONLY in selective acidic solution, while remaining unaffected by most downhole formation fluids.

The selectively dissolvable thermoset epoxy is expected to cost only a fraction of the corrodable metal plate. • The thermoset epoxy, in its unfilled, neat state exhibits a flexural strength and modulus of 100 MPa and 3 GPa, and a tensile strength and modulus of 73 MPa and 3.4 GPa, respectively, with 6 of tensile elongation before its breakage. • A density of 1.2 g/cc, and a typical commercial epoxy glass transition temperature (Tg) is identified as 113°C (235°F). Thus a load bearing property of the current thermoset material can conveniently be utilized towards its entire glassy region, e.g., until 100°C (212°F). Further extension of the glassy region is possible, and a consequent extension in service temperature can further be expected. • Some non-limiting embodiments of the inventions are as follows: a....