A system for fluid monitoring in a borehole for extracting hydrocarbons includes a casing to transport hydrocarbons, the casing defining an annulus between the casing and borehole wall. The system further includes a centralizer, coupled to the casing, to center the casing within the borehole. The system further includes a sensor unit, including a radio frequency identification (RFID) interrogator, positioned on the centralizer to monitor one or more fluids, including RFID tags, in the annulus.

A method for enhanced oil recovery from a hydrocarbon bearing subterranean formation includes withdrawing hydrocarbons from a production well extending into the formation, identifying a high permeability streak in the formation, and injecting a dense CO.sub.2 composition from an injection well into the high permeability streak. The dense CO.sub.2 composition includes dense CO.sub.2 and a thickener soluble in the dense CO.sub.2. The thickener includes copolymer. The method includes, after injecting the dense carbon dioxide composition into the high permeability streak, injecting an aqueous treatment fluid into the formation. The dense CO.sub.2 composition blocks the high permeability streak to divert at least a portion of the aqueous treatment fluid into bypassed regions of the formation during the injecting of the aqueous treatment fluid, and the injecting of the aqueous treatment fluid into the hydrocarbon bearing subterranean formation drives hydrocarbons in the hydrocarbon bearing subterranean formation towards the production well.

Wellbore treatment compositions comprising non-radioactive tracer materials and methods for using the non-radioactive tracer materials to determine the location of treatment fluids within a subterranean formation are provided herein. A method comprising introducing a treatment fluid comprising a non-radioactive tracer material into a subterranean formation; exposing a portion of the subterranean formation to neutrons from a neutron source to activate the non-radioactive tracer material in the portion of the subterranean formation; and detecting gamma rays emitted by the activated tracer material in the portion of the subterranean formation.

A well casing is cemented in a well bore in a subterranean formation by pumping cement slurry down into the well casing so that the cement slurry flows up into an annulus surrounding the well casing. While pumping the cement slurry, the position of the top of the cement slurry in the annulus is sensed, and the rise of the sensed position of the top of the cement slurry in the annulus is recorded as a function of time. The recording is analyzed to evaluate the cement job. For example, the analysis may indicate a problem addressed by adjusting a cement plan for a future cement job, and the analysis may indicate a need to repair a location of the set cement by perforating the well casing at the location to be repaired, and pumping cement slurry down the well casing to fill the location to be repaired.

A valve assembly for integration within a wellbore string disposed within a hydrocarbon-containing reservoir is provided. The valve assembly includes a valve housing having a plurality of frac ports for establishing fluid communication between a central passage and the reservoir. The valve assembly includes a bottom sleeve operatively mounted within the valve housing configured to selectively open the frac ports, and a top sleeve operatively mounted within the valve housing slidable between (i) a first position defining a first fluid pathway whereby fluid is flowable down into the central passage and into the reservoir via the frac ports, and (ii) a tracing position defining a second fluid pathway whereby fluid is flowable from the reservoir into an annulus defined between the top sleeve and the housing. The valve assembly also has a tracer compartment defined within the annulus forming part of the second fluid pathway and accommodating a tracer material.

A valve assembly for integration within a wellbore string disposed within a hydrocarbon-containing reservoir is provided. The valve assembly includes a valve housing having a plurality of frac ports for establishing fluid communication between a central passage and the reservoir. The valve assembly includes a bottom sleeve operatively mounted within the valve housing configured to selectively open the frac ports, and a top sleeve operatively mounted within the valve housing slidable between (i) a first position defining a first fluid pathway whereby fluid is flowable down into the central passage and into the reservoir via the frac ports, and (ii) a tracing position defining a second fluid pathway whereby fluid is flowable from the reservoir into an annulus defined between the top sleeve and the housing. The valve assembly also has a tracer compartment defined within the annulus forming part of the second fluid pathway and accommodating a tracer material.

A composition includes a functionalized fluorescent dye. The functionalized fluorescent dye includes an isothiocyanate-containing dye that is functionalized with a functional group. The functional group includes a primary amine. The functionalized fluorescent dye can be mixed with a fluid to form a tracer fluid for tracing fluid flow in a subterranean formation.

A composition includes a functionalized fluorescent dye. The functionalized fluorescent dye includes an isothiocyanate-containing dye that is functionalized with a functional group. The functional group includes a primary amine. The functionalized fluorescent dye can be mixed with a fluid to form a tracer fluid for tracing fluid flow in a subterranean formation.

The hydrocarbon wells include a radioactive tracer system, a production conduit, a lift gas supply conduit, a lift gas supply system configured to provide a lift gas stream to the lift gas supply conduit, and one or more gas lift valves each being configured to selectively permit lift gas to enter the production conduit and mix with reservoir liquid therein to generate a produced fluid stream. The radioactive tracer system is configured to inject a radioactive tracer into the lift gas stream and to detect the radioactive tracer within the produced fluid stream. The methods include injecting the radioactive tracer into the lift gas stream, flowing the radioactive tracer through an open gas lift valve into the production conduit, mixing the radioactive tracer with the reservoir liquid to generate a tracer-marked liquid band within the produced fluid stream, and detecting radiation from the tracer-marked liquid band.

Systems and methods for measuring flow velocity of a fluid mixture in a lateral section of an oil/gas well are presented. The flow velocity is measured by tracking movement of particles and/or features in the fluid mixture via visible and/or infrared imaging sensors of a camera-based flow sensor. According to another aspect, the imaging sensors detect back-reflected light by the particles and/or features, the light emitted by illuminators in the visible and/or infrared spectrum. According to yet another aspect, the particles are quantum dot illuminators injected into the fluid mixture, the flow velocity based on a time-of-flight of the quantum dots. The camera-based flow sensor may be rotatable to measure flow velocities at different angular positions of a pipe, rotation provided by rotation of an element of a mobile vessel to which the flow sensor is rigidly coupled.