A pressure-up blow-down method for recovering oil from an underground hydrocarbon formation, comprising the steps of: injecting an injection fluid into alternatingly-spaced multiple-induced fractures which extend radially outwardly and along a horizontal portion of a wellbore in the formation; ceasing injection of said injection fluid; recovering to surface oil which flows from remaining of the multiple induced fractures into the wellbore; and successively repeating the foregoing steps one or more times. Gas preferentially is initially used as the injection fluid and after one successive iteration water is then used. A sliding sleeve or sleeves which may be selectively slid open and closed within the wellbore in accordance with the method to allow and prevent, at various time periods in the method, fluid communication with fluid injection fractures and oil production fractures.

A pressure-up blow-down method for recovering oil from an underground hydrocarbon formation, comprising the steps of: injecting an injection fluid into alternatingly-spaced multiple-induced fractures which extend radially outwardly and along a horizontal portion of a wellbore in the formation; ceasing injection of said injection fluid; recovering to surface oil which flows from remaining of the multiple induced fractures into the wellbore; and successively repeating the foregoing steps one or more times. Gas preferentially is initially used as the injection fluid and after one successive iteration water is then used. A sliding sleeve or sleeves which may be selectively slid open and closed within the wellbore in accordance with the method to allow and prevent, at various time periods in the method, fluid communication with fluid injection fractures and oil production fractures.

A flapper valve includes a body having first and second end, and a flapper pivotably coupled to the body and movable between a closed position, where the flapper prevents fluid flow through the body, and an open position, where fluid flow is allowed through the body. A first torsion spring is coupled to the body at the second end and provides a spring arm that engages and urges the flapper to the closed position. A support beam is coupled to the body and includes an axial extension that extends axially past the second end. A closure beam having a first beam end is pivotably coupled to the axial extension and a second beam end is engageable with the flapper. A second torsion spring is coupled to the axial extension and engageable with the closure beam to urge the closure beam into engagement with the flapper.

A fracturing tool features spaced releasable packers with an outlet in between. The housing has relatively moving components for opening the frac port between the packers with weight set on the lower packer. Once the frac port is opened the upper packer is set and the pumping begins. The upper packer can be released so that tension can be pulled on the lower packer to close the frac port and open a through passage in the housing. In one embodiment the through passage can be located above the lower packer to a sand jet perforator to clean debris away from the lower packer if it is difficult to release the lower packer or to abrasively perforate through a tubular. In another embodiment the housing outlet can be below bottom packer to perform a treatment further downhole or to operate another tool. The straddle tool can be run in on coiled tubing.

A fracturing tool features spaced releasable packers with an outlet in between. The housing has relatively moving components for opening the frac port between the packers with weight set on the lower packer. Once the frac port is opened the upper packer is set and the pumping begins. The upper packer can be released so that tension can be pulled on the lower packer to close the frac port and open a through passage in the housing. In one embodiment the through passage can be located above the lower packer to a sand jet perforator to clean debris away from the lower packer if it is difficult to release the lower packer or to abrasively perforate through a tubular. In another embodiment the housing outlet can be below bottom packer to perform a treatment further downhole or to operate another tool. The straddle tool can be run in on coiled tubing.

A one-way valve for use in a wellbore includes a housing having a longitudinal axis defining a flow bore. A valve seat is arranged in the housing along the flow bore. A flapper member is pivotally supported in the housing between a closed position and an open position. The flapper member includes a first side having a sealing surface that selectively engages the valve seat in the closed position and an opposing second side. The flapper member also includes a central portion that is aligned with the longitudinal axis in the closed portion and a passage extending through the flapper member. An equalizing cartridge is arranged in the passage. The equalizing cartridge includes an equalizing housing and an equalizing plunger including an activation end provided at the first side of the flapper member.

A one-way valve for use in a wellbore includes a housing having a longitudinal axis defining a flow bore. A valve seat is arranged in the housing along the flow bore. A flapper member is pivotally supported in the housing between a closed position and an open position. The flapper member includes a first side having a sealing surface that selectively engages the valve seat in the closed position and an opposing second side. The flapper member also includes a central portion that is aligned with the longitudinal axis in the closed portion and a passage extending through the flapper member. An equalizing cartridge is arranged in the passage. The equalizing cartridge includes an equalizing housing and an equalizing plunger including an activation end provided at the first side of the flapper member.

A valve assembly can include a generally tubular housing, a mandrel reciprocably disposed in the housing and operative to displace a valve closure in response to relative displacement between the mandrel and the housing, an engagement device reciprocably disposed externally on the housing and secured relative to the mandrel, so that the mandrel displaces with the engagement device, and a biasing device that biases the mandrel and engagement device in a selected longitudinal direction. A system can include a tubular string and a valve assembly reciprocably disposed in the tubular string, the valve assembly including a valve that selectively restricts flow through a longitudinal passage. The valve closes in response to displacement of the valve assembly in a selected longitudinal direction relative to the tubular string, and the valve opens in response to displacement of the valve assembly in the same longitudinal direction relative to the tubular string.

A chemical treatment assembly can include a section including a pressure containment valve that selectively permits and prevents fluid communication with a flow passage in the section, and another section including a pressure containment valve that selectively permits and prevents fluid communication with a flow passage in the section. The pressure containment valves are closed in response to disconnection of the sections. A method of containing pressure in sections of a chemical treatment assembly can include installing a pressure containment valve in each of the sections, the pressure containment valves being configured to close in response to disconnecting the sections. Another chemical treatment assembly can include an outer housing, a flow passage extending longitudinally through the outer housing, a chemical treatment positioned in the flow passage, and a pressure containment valve that selectively permits and prevents fluid communication with the flow passage through the pressure containment valve.

A chemical treatment assembly can include a section including a pressure containment valve that selectively permits and prevents fluid communication with a flow passage in the section, and another section including a pressure containment valve that selectively permits and prevents fluid communication with a flow passage in the section. The pressure containment valves are closed in response to disconnection of the sections. A method of containing pressure in sections of a chemical treatment assembly can include installing a pressure containment valve in each of the sections, the pressure containment valves being configured to close in response to disconnecting the sections. Another chemical treatment assembly can include an outer housing, a flow passage extending longitudinally through the outer housing, a chemical treatment positioned in the flow passage, and a pressure containment valve that selectively permits and prevents fluid communication with the flow passage through the pressure containment valve.