Abstract: A stock shape for a downhole tool component includes a magnesium alloy including a phase containing 70 to 95 wt. % of magnesium in which 0 wt. % or more and less than 0.3 wt. % of a rare earth metal, a metal material other than the magnesium and the rare earth metal, and 0.1 to 20 wt. % of a degradation accelerator are distributed, and the stock shape has an average particle size of the metal material of 1 to 300 ?m, tensile strength of 200 to 500 MPa, and a degradation rate in a 2% potassium chloride aqueous solution at 93° C. of not less than 20 mg/cm2 and not greater than 20000 mg/cm2 per day. Accordingly, a downhole tool having high strength and being readily degradable is established.

Abstract: A downhole tool member for hydrocarbon resource recovery, comprising a shaped body of a polyglycolic acid resin having a weight average molecular weight of at least 70,000, having an effective thickness which is ½ or more of a critical thickness of surface decomposition, and exhibiting a thickness reduction rate in water which is constant with respect to time. As a result, it has become possible to more accurately design the strength and time up to the collapse of the downhole tool member which forms the whole or a part of a downhole tool for developing or repairing downholes for recovery of hydrocarbon resources, such as oil and gas.

Abstract: A plug for well drilling includes a mandrel and at least one diametrically expandable annular rubber member and at least one slip disposed on an outer circumferential surface orthogonal to an axial direction of the mandrel; (i) the mandrel being formed from a degradable material; and (ii) the at least one diametrically expandable annular rubber member being formed from a degradable rubber material having a rate of decrease of not less than 5% in 50% strain compressive stress after immersion in water at a temperature of 150° C. for 24 hours relative to the compressive stress before immersion; and/or having a rate of loss of mass of from 5 to 100% after immersion in water at a temperature of 150° C. for 72 hours relative to the mass before immersion. A well drilling method includes a step of isolating a borehole using the plug for well drilling, part or all of the plug being degraded thereafter.

Abstract: Provided is a rubber member for downhole tools, of which a decrease rate of 50% strain compressive stress after immersion for 24 hours in 150° C. water relative to 50% strain compressive stress before immersion is not less than 5%, and preferably not less than 50%. The rubber member is suitable for a seal member, ball sealer, ball seat, and a protecting member. Also provided is a downhole tool comprising the rubber member, and a method for recovering a hydrocarbon resource using the downhole tool.

Abstract: Provided is a rubber member for downhole tools, of which a decrease rate of 50% strain compressive stress after immersion for 24 hours in 150° C. water relative to 50% strain compressive stress before immersion is not less than 5%, and preferably not less than 50%. The rubber member is suitable for a seal member, ball sealer, ball seat, and a protecting member. Also provided is a downhole tool comprising the rubber member, and a method for recovering a hydrocarbon resource using the downhole tool.

Abstract: A degradable rubber member for a downhole tool formed from a rubber material containing from 0.1 to 20 parts by mass of a degradation accelerator relative to 100 parts by mass of a degradable rubber (optionally containing other rubber materials and/or reinforcing materials), of which, preferably, the decrease rate of the mass or the 50% strain compressive stress after immersion for 24 hours in 150° C. water is not less than 5%, and/or the mass loss rate after immersion for 72 hours in 150° C. water is from 5 to 100%, and further, as desired, the tensile fracture strain at 66° C. is not less than 50%, the 70% strain compressive stress is not less than 10 MPa, and the compressive fracture strain is not less than 50%; a degradable seal member or a protecting member for downhole tools comprising such a rubber member; and a downhole tool such as a plug for well drilling, and a method for well drilling.

Abstract: A degradable seal member for downhole tools, the member being a diameter-expandable annular seal member, the diameter-expandable annular seal member comprising: two or more annular members distributed along an axial direction, the annular members being formed from a degradable polymer material having hardness in a range from A60 to D80; a plug for well drilling; and a method for well drilling using the degradable seal member for downhole tools.

Abstract: A stock shape for a downhole tool component includes a magnesium alloy including a phase containing 70 to 95 wt. % of magnesium in which 0 wt. % or more and less than 0.3 wt. % of a rare earth metal, a metal material other than the magnesium and the rare earth metal, and 0.1 to 20 wt. % of a degradation accelerator are distributed, and the stock shape has an average particle size of the metal material of 1 to 300 ?m, tensile strength of 200 to 500 MPa, and a degradation rate in a 2% potassium chloride aqueous solution at 93° C. of not less than 20 mg/cm2 and not greater than 20000 mg/cm2 per day. Accordingly, a downhole tool having high strength and being readily degradable is established.

Abstract: A downhole tool member for hydrocarbon resource recovery, comprising a shaped body of a polyglycolic acid resin having a weight average molecular weight of at least 70,000, having an effective thickness which is ½ or more of a critical thickness of surface decomposition, and exhibiting a thickness reduction rate in water which is constant with respect to time. As a result, it has become possible to more accurately design the strength and time up to the collapse of the downhole tool member which forms the whole or a part of a downhole tool for developing or repairing downholes for recovery of hydrocarbon resources, such as oil and gas.

Abstract: A solidification- and extrusion-molded article of polyglycolic acid, which is formed of a resin material containing polyglycolic acid, the polyglycolic acid having a melt viscosity of 200 to 2,000 Pa·s, and has a thickness or diameter of greater than 100 mm but not greater than 500 mm. A downhole tool or a component thereof and a ball sealer for petroleum excavation are formed by cutting the solidification- and extrusion-molded article. A method for manufacturing the solidification- and extrusion-molded article of polyglycolic acid and a method for manufacturing a ball sealer for petroleum excavation.

Abstract: A poly-L-lactic acid (PLLA) solid-state extrusion molded article having a weight average molecular weight of from 100,000 to 380,000 and a melt viscosity of from 20 to 2,000 Pa·s (at a temperature of 240° C. and a shear rate of 120 sec?1) and having an L-form content of from 80 to 100%, the article having a thickness or diameter of from 10 to 500 mm and a tensile strength of from 5 to 100 MPa at a temperature of 66° C.

Abstract: Provided are: a polyglycolic acid (PGA) solidification- and extrusion-molded article that is formed from a resin material containing PGA, the PGA having a weight average molecular weight of 100,000 to 300,000 and a melt viscosity (temperature: 270° C.; shearing speed: 120 sec?1) of 100 to 2,000 Pa·s, and that has a tensile strength at a temperature of 150° C.

Abstract: A solidification- and extrusion-molded article of polyglycolic acid, which is formed of a resin material containing polyglycolic acid, the polyglycolic acid having a melt viscosity of 200 to 2,000 Pa·s, and has a thickness or diameter of greater than 100 mm but not greater than 500 mm. A downhole tool or a component thereof and a ball sealer for petroleum excavation are formed by cutting the solidification- and extrusion-molded article. A method for manufacturing the solidification- and extrusion-molded article of polyglycolic acid and a method for manufacturing a ball sealer for petroleum excavation.

Abstract: A downhole tool member for hydrocarbon resource recovery, comprising a shaped body of a polyglycolic acid resin having a weight average molecular weight of at least 70,000, having an effective thickness which is ½ or more of a critical thickness of surface decomposition, and exhibiting a thickness reduction rate in water which is constant with respect to time. As a result, it has become possible to more accurately design the strength and time up to the collapse of the downhole tool member which forms the whole or a part of a downhole tool for developing or repairing downholes for recovery of hydrocarbon resources, such as oil and gas.

Abstract: Provided are a molded product for well drilling comprising a reactive metal and a degradable resin composition that promotes a degradation reaction of the reactive metal, preferably a degradable resin composition comprising a degradable resin that generates acid upon degradation or a degradable resin composition containing a degradable resin and an inorganic material or an organic material that promotes degradation of the reactive metal; a molded product for well drilling which is a downhole tool or a downhole tool member; and a method for well drilling that uses said molded product for well drilling.

Abstract: Described are a molded product having an effective thickness of 1 mm or more, the molded product being formed from an aliphatic polyester resin composition containing from 1 to 30 parts by mass of a carboxylic acid anhydride and preferably further containing from 1 to 50 parts by mass of at least one type of a short fiber reinforcing material, a thermoplastic elastomer, or an acrylic rubber core-shell polymer per 100 parts by mass of an aliphatic polyester resin containing not less than 50 mass % of a polyglycolic acid resin, the effective thickness being 1 mm or more; a downhole tool for hydrocarbon resource recovery formed from the molded product having an effective thickness of 1 mm or more; an aliphatic polyester resin composition for the downhole tool member for hydrocarbon resource recovery; and a well drilling method.

Abstract: A ball sealer for hydrocarbon resource recovery, characterized by being obtained by coating a spherical core that comprises at least one layer comprising a disintegrable aliphatic polyester resin with a resin material that has higher impact resistance than the aliphatic polyester resin and by having a diameter of not less than approximately 25 mm (1 inch). This ball sealer has a large diameter, retains the property of being disintegrable after fracturing, and has impact resistance which makes the ball withstand high-velocity loading. The sealer is suitable for use in hydraulic fracturing, which is commonly used for recovering hydrocarbon resources including petroleum and gases. This large-diameter ball sealer can be efficiently formed with high dimensional accuracy by a method including at least one insert injection molding step.

Abstract: A well treatment method characterized by disintegrating an elastic material by contacting a seal member for downhole tools comprising the elastic material with a well treatment fluid (acids such as hydrochloric acid, formic acid, acetic acid, and hydrofluoric acid, alkalis, hot water, steam, organic solvents, and the like).

Abstract: A downhole tool, provided with: a downhole-tool member containing a reactive metal; a downhole-tool member containing a degradable resin composition that promotes degradation of the reactive metal, preferably a degradable resin composition containing a degradable resin that generates an acid by degradation or a degradable resin composition containing a degradable resin and an inorganic substance or organic substance that promotes degradation of the reactive metal; and, as desired, a degradable rubber member. Moreover, a well-drilling method using this downhole tool.

Abstract: A plug for well drilling comprising a mandrel and members attached on an outer circumferential surface orthogonal to an axial direction of the mandrel, wherein at least one of the members or the mandrel is formed from a degradable material; a ring-shaped ratchet structure formed from a plurality of interlocking parts that allows movement of the member in one direction along the axial direction of the mandrel and restricts movement in the opposite direction is provided on an inner circumferential surface of the member and the outer circumferential surface of the mandrel; preferably further comprising a pushing jig including a ratchet structure and a ring-shaped plate adjacent to the axial direction leading side of the pushing jig. Additionally, a well drilling method using the plug for well drilling, comprising degrading a part or all of the plug after blocking a borehole.