A system includes a drillstring with an electromagnetic (EM) transmitter in a first borehole. The system also includes at least one fiber optic sensor deployed in a second borehole. The system also includes a processor configured to demodulate a data stream emitted by the EM transmitter based on EM field measurements collected by the at least one fiber optic sensor.

An assembly for use in a wellbore can include a plurality of sensors positioned external to a casing string. The plurality of sensors can be positioned for detecting an amount of a hydrocarbon that is present in a fluid in the wellbore and a pH of the fluid in the wellbore. The plurality of sensors can be positioned for wirelessly transmitting signals representing the amount of the hydrocarbon that is present in the fluid and the pH of the fluid to a receiving device.

An assembly for use in a wellbore can include a plurality of sensors positioned external to a casing string. The plurality of sensors can be positioned for detecting an amount of a hydrocarbon that is present in a fluid in the wellbore and a pH of the fluid in the wellbore. The plurality of sensors can be positioned for wirelessly transmitting signals representing the amount of the hydrocarbon that is present in the fluid and the pH of the fluid to a receiving device.

A method for drilling a new oil or gas well in a selected geographical location comprises extracting drilling modes from historic drilling data obtained from a group of drilled wells in the selected geographical location using a pattern recognition model. Each drilling mode represents a distinct pattern that quantifies at least two drilling variables at a specified drilling depth. The method also comprises selecting a sequence of drilling modes at positions along a reference well as reference drilling modes that represent more efficient values for a selection of one or more of the at least two drilling variables compared to other extracted drilling modes; associating drilling parameter settings with the reference drilling modes; and drilling the new oil or gas well applying at least some of the drilling parameter settings.

A method for drilling a new oil or gas well in a selected geographical location comprises extracting drilling modes from historic drilling data obtained from a group of drilled wells in the selected geographical location using a pattern recognition model. Each drilling mode represents a distinct pattern that quantifies at least two drilling variables at a specified drilling depth. The method also comprises selecting a sequence of drilling modes at positions along a reference well as reference drilling modes that represent more efficient values for a selection of one or more of the at least two drilling variables compared to other extracted drilling modes; associating drilling parameter settings with the reference drilling modes; and drilling the new oil or gas well applying at least some of the drilling parameter settings.

Systems and methods for drilling a borehole into the earth are provided. The systems and methods include drilling a first portion of a borehole with a drilling system comprising a disintegrating device, the first portion extending from the surface to a subsurface reference point, wherein steering within the first portion is performed based on a first coordinate system with a first origin, creating a second coordinate system, wherein the second coordinate system has a second origin that is related to subsurface reference point, and drilling a second portion of the borehole with the drilling system, wherein steering within the second portion is performed based on the second coordinate system.

Systems and methods for drilling a wellbore. The method includes measuring a first distance that a drilling device is raised while connected to a drill string, determining a weight-on-bit in the drill string, determining a second distance to lower the drilling device such that a drill bit at a lower extremity of the drill string approaches toward a bottom of the wellbore, based on the first distance and the weight-on-bit, and lowering the drilling device by the second distance.

Systems and methods for drilling a wellbore. The method includes measuring a first distance that a drilling device is raised while connected to a drill string, determining a weight-on-bit in the drill string, determining a second distance to lower the drilling device such that a drill bit at a lower extremity of the drill string approaches toward a bottom of the wellbore, based on the first distance and the weight-on-bit, and lowering the drilling device by the second distance.

A system and method of drilling a wellbore to a target may include measuring attitudes at two adjacent survey stations along a wellbore using a downhole surveying tool. An actual change in wellbore position over a survey leg linking the two survey stations may be determined. Corrections may be applied to the measured attitude at one or both of the survey stations such that an estimated well path joining the survey stations indicates the determined actual change in wellbore position between the two survey stations.

A system and method of drilling a wellbore to a target may include measuring attitudes at two adjacent survey stations along a wellbore using a downhole surveying tool. An actual change in wellbore position over a survey leg linking the two survey stations may be determined. Corrections may be applied to the measured attitude at one or both of the survey stations such that an estimated well path joining the survey stations indicates the determined actual change in wellbore position between the two survey stations.