Abstract: A method can include measuring temperature along a relief wellbore, thereby detecting a temperature anomaly in an earth formation penetrated by the relief wellbore, and determining a location of an influx into a target wellbore, based on the temperature anomaly detecting. A thermal anomaly ranging system for use with a subterranean well can include a temperature sensor in a relief wellbore that penetrates an earth formation, the temperature sensor detecting a temperature anomaly in the formation, and the temperature anomaly being caused by an influx into a target wellbore. Another method can include measuring optical scattering in an optical waveguide positioned in a relief wellbore, thereby detecting a temperature anomaly in an earth formation penetrated by the relief wellbore, and determining a location of an influx into a target wellbore, based on the temperature anomaly detecting.

Abstract: A method of establishing fluid communication between wellbores can include forming a flow path from one wellbore to another wellbore, a flow area of the flow path increasing in a direction from the first wellbore toward the second wellbore. An explosive assembly for use in a well can include an explosive device having multiple explosive charges, the explosive charges producing longitudinal shock waves that collide with each other and result in a laterally directed shock wave, and a shield that focuses the laterally directed shock wave into a predetermined angular range of less than 360 degrees. A method of establishing fluid communication between wellbores can include forming a flow path from one wellbore to another wellbore, the flow path intersecting an uncased portion of the second wellbore.

Abstract: A method of establishing fluid communication between wellbores can include forming a flow path from one wellbore to another wellbore, a flow area of the flow path increasing in a direction from the first wellbore toward the second wellbore. An explosive assembly for use in a well can include an explosive device having multiple explosive charges, the explosive charges producing longitudinal shock waves that collide with each other and result in a laterally directed shock wave, and a shield that focuses the laterally directed shock wave into a predetermined angular range of less than 360 degrees. A method of establishing fluid communication between wellbores can include forming a flow path from one wellbore to another wellbore, the flow path intersecting an uncased portion of the second wellbore.

Abstract: A method can include measuring microseismic activity in a relief wellbore, thereby detecting a microseismic event in an earth formation penetrated by the relief wellbore, and determining a location of an influx into a target wellbore, based on the microseismic event detecting. A microseismic ranging system for use with a subterranean well can include at least one microseismic sensor in a relief wellbore that penetrates an earth formation, with the microseismic sensor detecting a microseismic event in the formation, the microseismic event being caused by an influx into a target wellbore. Another method can include measuring optical scattering in an optical waveguide positioned in a relief wellbore, thereby detecting a microseismic event in an earth formation penetrated by the relief wellbore, and determining a location of an influx into a target wellbore, based on the microseismic event detecting.

Abstract: A method of severing a tubular structure can include producing a stream of plasma between a plasma arc cutter and the tubular structure, and displacing the plasma arc cutter relative to the tubular structure, thereby cutting through the tubular structure. A plasma arc cutting apparatus can include a transport vehicle, a boom extending from the transport vehicle, at least one plasma arc cutter, and at least one actuator that displaces the plasma arc cutter relative to the boom. Another method of severing a tubular structure can include conveying a plasma arc cutter to the tubular structure with a transport vehicle, and displacing the plasma arc cutter relative to the transport vehicle.

Abstract: A method of connecting to an existing wellbore downhole can include installing a swellable material into the existing wellbore from a connecting wellbore drilled into the existing wellbore. A well system can include a relief wellbore drilled proximate an existing wellbore, a connecting wellbore drilled from the relief wellbore to the existing wellbore, a tubular string extending from the relief wellbore through the connecting wellbore and into the existing wellbore, and a swellable material which swells in an annulus formed between the tubular string and at least one of the relief wellbore, the connecting wellbore and the existing wellbore. Another method of connecting to an existing wellbore downhole can include drilling a relief wellbore proximate the existing wellbore, then drilling a connecting wellbore from the relief wellbore to the existing wellbore, and then installing a swellable material into the existing wellbore from the connecting wellbore.

Abstract: A method of establishing fluid communication between wellbores can include forming a flow path from one wellbore to another wellbore, a flow area of the flow path increasing in a direction from the first wellbore toward the second wellbore. An explosive assembly for use in a well can include an explosive device having multiple explosive charges, the explosive charges producing longitudinal shock waves that collide with each other and result in a laterally directed shock wave, and a shield that focuses the laterally directed shock wave into a predetermined angular range of less than 360 degrees. A method of establishing fluid communication between wellbores can include forming a flow path from one wellbore to another wellbore, the flow path intersecting an uncased portion of the second wellbore.

Abstract: A method can include measuring microseismic activity in a relief wellbore, thereby detecting a microseismic event in an earth formation penetrated by the relief wellbore, and determining a location of an influx into a target wellbore, based on the microseismic event detecting. A microseismic ranging system for use with a subterranean well can include at least one microseismic sensor in a relief wellbore that penetrates an earth formation, with the microseismic sensor detecting a micro seismic event in the formation, the microseismic event being caused by an influx into a target wellbore. Another method can include measuring optical scattering in an optical waveguide positioned in a relief wellbore, thereby detecting a microseismic event in an earth formation penetrated by the relief wellbore, and determining a location of an influx into a target wellbore, based on the microseismic event detecting.

Abstract: A method can include measuring temperature along a relief wellbore, thereby detecting a temperature anomaly in an earth formation penetrated by the relief wellbore, and determining a location of an influx into a target wellbore, based on the temperature anomaly detecting. A thermal anomaly ranging system for use with a subterranean well can include a temperature sensor in a relief wellbore that penetrates an earth formation, the temperature sensor detecting a temperature anomaly in the formation, and the temperature anomaly being caused by an influx into a target wellbore. Another method can include measuring optical scattering in an optical waveguide positioned in a relief wellbore, thereby detecting a temperature anomaly in an earth formation penetrated by the relief wellbore, and determining a location of an influx into a target wellbore, based on the temperature anomaly detecting.

Abstract: A method of establishing fluid communication between wellbores can include forming a flow path from one wellbore to another wellbore, a flow area of the flow path increasing in a direction from the first wellbore toward the second wellbore. An explosive assembly for use in a well can include an explosive device having multiple explosive charges, the explosive charges producing longitudinal shock waves that collide with each other and result in a laterally directed shock wave, and a shield that focuses the laterally directed shock wave into a predetermined angular range of less than 360 degrees. A method of establishing fluid communication between wellbores can include forming a flow path from one wellbore to another wellbore, the flow path intersecting an uncased portion of the second wellbore.

Abstract: A method of severing a tubular structure can include producing a stream of plasma between a plasma arc cutter and the tubular structure, and displacing the plasma arc cutter relative to the tubular structure, thereby cutting through the tubular structure. A plasma arc cutting apparatus can include a transport vehicle, a boom extending from the transport vehicle, at least one plasma arc cutter, and at least one actuator that displaces the plasma arc cutter relative to the boom. Another method of severing a tubular structure can include conveying a plasma arc cutter to the tubular structure with a transport vehicle, and displacing the plasma arc cutter relative to the transport vehicle.

Abstract: A method of connecting to an existing wellbore downhole can include installing a swellable material into the existing wellbore from a connecting wellbore drilled into the existing wellbore. A well system can include a relief wellbore drilled proximate an existing wellbore, a connecting wellbore drilled from the relief wellbore to the existing wellbore, a tubular string extending from the relief wellbore through the connecting wellbore and into the existing wellbore, and a swellable material which swells in an annulus formed between the tubular string and at least one of the relief wellbore, the connecting wellbore and the existing wellbore. Another method of connecting to an existing wellbore downhole can include drilling a relief wellbore proximate the existing wellbore, then drilling a connecting wellbore from the relief wellbore to the existing wellbore, and then installing a swellable material into the existing wellbore from the connecting wellbore.

Abstract: Subsea controlled milling apparatus and methods. In a described embodiment, a method of controlling displacement of a cutting device conveyed on a tubular string in a subterranean well includes the steps of: interconnecting an apparatus in the tubular string, the apparatus including an axial advancement device and an anchoring device; actuating the anchoring device to anchor the apparatus in the well; applying a pressure differential to the advancement device, thereby displacing the cutting device relative to the apparatus; and operating the cutting device to cut a structure in the well.

Abstract: Subsea controlled milling apparatus and methods. In a described embodiment, a method of controlling displacement of a cutting device conveyed on a tubular string in a subterranean well includes the steps of: interconnecting an apparatus in the tubular string, the apparatus including an axial advancement device and an anchoring device; actuating the anchoring device to anchor the apparatus in the well; applying a pressure differential to the advancement device, thereby displacing the cutting device relative to the apparatus; and operating the cutting device to cut a structure in the well.

Abstract: A wellbore junction isolation method and associated apparatus provide convenient isolation of a wellbore junction while permitting certain operations to be performed in a main or branch wellbore below the junction. In described embodiments, formations intersected by a main or branch wellbore below a wellbore junction may be stimulated by fracturing after installing an assembly at the wellbore junction, in a straddling and sealing relationship therewith, to isolate it from pressures applied during the fracturing operation. The illustrated isolation assembly may be installed in a single trip into the main wellbore.

Abstract: A wellbore junction isolation method and associated apparatus provide convenient isolation of a wellbore junction while permitting certain operations to be performed in a wellbore below the junction. In a described embodiment, a formation intersected by a main wellbore below a wellbore junction is stimulated by fracturing after installing an assembly at the wellbore junction to isolate it from pressures applied during the fracturing operation. In this embodiment, the assembly is installed in a single trip into the main wellbore.

Abstract: A wellbore junction isolation method and associated apparatus provide convenient isolation of a wellbore junction while permitting certain operations to be performed in a main or branch wellbore below the junction. In described embodiments, formations intersected by a main or branch wellbore below a wellbore junction may be stimulated by fracturing after installing an assembly at the wellbore junction, in a straddling and sealing relationship therewith, to isolate it from pressures applied during the fracturing operation. The illustrated isolation assembly may be installed in a single trip into the main wellbore.