Abstract: The present invention involves a method and apparatus for enhanced recovery of petroleum fluids from the subsurface by injection of a steam and hydrocarbon vaporized solvent in contact with the oil sand formation and the heavy oil and bitumen in situ. Multiple propped hydraulic fractures are constructed from the well bore into the oil sand formation and filled with a highly permeable proppant. Steam, a hydrocarbon solvent, and a non-condensing diluent gas are injected into the well bore and the propped fractures. The injected gas flows upwards and outwards in the propped fractures contacting the oil sands and in situ bitumen on the vertical faces of the propped fractures. The steam condenses on the cool bitumen and thus heats the bitumen by conduction, while the hydrocarbon solvent vapors diffuse into the bitumen from the vertical faces of the propped fractures.

Abstract: Subterranean formation treatment methods incorporating a rheology model which enables prediction of fluid rheology properties during a treatment operation, where the foundation of the model is a description of the reaction chemistry which describes how the number of crosslinks and broken polymer linkages develops in time under the influence of crosslinkers, breakers, and/or thermally induced effects and pressure effects. In one aspect, when used as a tool for simulating the fluid viscosity, the model can help optimizing the fluid design and optional breaker schedule for a hydraulic fracturing treatment.

Abstract: A system for completing a well having casing (34) includes a perforating assembly (38) and a tubing string assembly (40). The tubing string assembly (40) including a pair of seal assemblies (56, 74), a production screen assembly (58) and a ported sleeve (66) positioned between the seal assemblies (56, 74) and a live annulus screen assembly (76) positioned uphole of the seal assemblies (56, 74). The perforating assembly (38) is operated to perforate the well and is then released downhole. The tubing string assembly (40) is then repositioned such that the production screen assembly (58) is located proximate the perforated interval (14) so that when the well is hydraulically fractured with a treatment slurry that is pumped through the ported sleeve (66), the formation reaction to the fracturing is monitored by obtaining pressure readings in the annulus in fluid communication with the live annulus screen assembly (76).

Abstract: A process to determine optimal completion type and design prior to drilling of a hydrocarbon producing well utilizing information from hydrocarbon recovery modeling such as reservoir, geo-mechanical, and material modeling over the production life of the well. An embodiment of the process includes obtaining information regarding pore pressure depletion, stress magnitudes and orientations, and strength of rock formation from hydrocarbon recovery modeling to determine optimum well completion design including the selection of a completion type, trajectory, and location. Additionally, the process may also consider probable failure mechanisms and identified completion requirements, and their corresponding effect on completion options.

Abstract: The present invention provides for an apparatus and method of use to control a downhole tool remotely based on the autocorrelation of command sequences. Repeating signals of a priori unknown or undefined shape can be correlated to themselves to reliably distinguish intentional changes from random fluctuations or other operations performed on the well. Using autocorrelation, any fluctuation of pressure of sufficient amplitude can be used to send commands by controlling the timing or the number of repetitions of the sequence.

Abstract: The invention relates to a method of controlling the production of oil or gas from a formation (1) comprising that a first and second drilled production well (105, 110) are formed next to each other that extend essentially horizontally, that, at the drilled production wells, a further drilled well (115) is formed that extends between the first and the second drilled production well (105, 110), that the production of oil or gas is initiated, and that, while oil or gas is being produced, a liquid is conveyed to said further drilled well (115) and out into the formation (1) for a first period of time T1. The invention is characterised in that the pore pressure of the formation is influenced during the period T1 with the object of subsequently controlling the formation of fractures along a drilled well, typically across large distances in the reservoir.

Abstract: Hydraulic fracture dimensions and, optionally, fracture closure pressure and time are determined by adding particulate matter that discharges to create an acoustic signal to the proppant, allowing the particulate matter to discharge, and detecting the acoustic signal with geophones or accelerometers. The particulate matter may be spheres or fibers. The discharge may be explosion, implosion, detonation, or rapid combustion or ignition. The discharge may be triggered by fracture closure or by chemical reaction.

Abstract: Solutions for the propagation of a hydraulic fracture in a permeable elastic rock and driven by injection of a Newtonian fluid. Through scaling, the dependence of the solution on the problem parameters is reduced to a small number of dimensionless parameters.

Abstract: The present invention relates generally to subterranean well construction, and more particularly, to improved methods for producing gas from subterranean formations that include coal seams. The method according to the present invention includes the steps of drilling at least one substantially vertical well bore intersecting the coal seam, drilling at least one substantially horizontal well bore disposed substantially within the coal seam and exiting from the at least one substantially vertical well bore, and fracturing the coal seam along the at least one substantially horizontal well bore using a hydrajetting tool to produce a plurality of fractures. The plurality of fractures is spaced to maximize interference between the fractures and enhances the production of gas from the coal seam of the subterranean formation. A plurality of substantially horizontal well bores can also be drilled.

Abstract: Changes occurring downhole during a fracturing process can create or reflect pressure signals. Capturing and evaluating such pressure waves during fracturing enables personnel to monitor, in real time or later, what happens downhole. When a fracture extends, a burst of acoustic noise is embodied in a pressure wave or signal, as is noise coming from other sources. By transforming time-based pressure signals to a frequency base, one can monitor this acoustic noise. In a particular implementation, a waterfall plot of frequency spectra at successive time slices of the original signal is used to determine frequency ridges, such as a ridge of decreasing frequencies indicates fracture extension and a ridge of increasing frequencies indicates either closure or proppant backing up in the fracture. Filtering, such as wavelet filtering, can be used. A fracturing process can be controlled in response to determining whether the fracture is extending.

Abstract: A method for growth of a hydraulic fracture or a tall frac is described wherein the tall frac is disposed next to a well bore using a sandpacked annulus. Also, a method for creating a permeable well bore annulus is disclosed. The method for creating the tall frac includes creating a linear-sourced, cylindrical stress field by maneuvering the intersection of two independent friction-controlled pressure gradients of a frac pad fluid. The intersection of these two frac pad fluid pressure gradients can be controlled when the frac pad fluid traverses along a well bore sandpacked annulus. The first pressure gradient is created by controlling the fluid flow rate and the consequent, friction pressure loss in the frac pad fluid flow through a portion of the sandpacked annulus, located above the top of the upwardly propagating tall frac hydraulic fracture. The first pressure gradient must be significantly greater than the average gradient of the formation, frac-extension pressure gradient.

Abstract: A well testing system and well testing method is described which can be operated as a closed system with no production of hydrocarbons outside the well or gas can be separated and flared at surface giving minimal environmental impact with the liquid hydrocarbon being re-injected. This is achieved by providing a string with at least two well conduits which may be arranged in a concentric or non-concentric parallel configuration. One conduit is used to produce formation fluids to surface or to produce/store unrepresentative initial flow products and the other conduit is used to store formation fluid. The storage conduit can be filled from the top (surface) or the bottom of the well. In a preferred arrangement a valve is provided between the storage conduit and the well annulus for well pressure control, and a shut-in or test valve, which is controllable from surface, is disposed in the non-storage production conduit.

Abstract: A method is given of fracturing a subterranean formation including the step of a) pumping at least one device actively transmitting data that provide information on the device position, and further comprising the step of assessing the fracture geometry based on the positions of said at least one device, or b) pumping metallic elements, preferably as proppant agents, and further locating the position of said metallic elements with a tool selected from the group consisting of magnetometers, resistivity tools, electromagnetic devices and ultra-long arrays of electrodes, and further comprising the step of assessing the fracture geometry based on the positions of said metallic elements. The method allows monitoring of the fracture geometry and proppant placement.

Abstract: A method of increasing productivity and recovery of wells in oil and gas fields includes determining a direction of maximal horizontal stresses, producing at least two wells so that they are spaced from one another in a direction corresponding to the direction of the maximum horizontal stresses, forming in at least one of the wells at least one vertical slot oriented substantially from the at least one well to the other of the wells, and introducing a hydrofracturing fluid at least into the at least one well to produce a hydraulic fracture in direction from the at least one well to the other well.

Abstract: A method of stimulating an entire target formation of an oil or gas well during fluid treatment is obtained by dividing the target formation into intermediate zones and initiating stimulation in each intermediate zone. Once stimulation is initiated in each intermediate zone, ball sealers are used to block the casing perforations at the intermediate zone and divert fluids to another intermediate zone. After stimulation has been initiated in all intermediate zones, the ball sealers are removed from the perforations and treatment of the entire target formation is conducted.

Abstract: A method and system and program storage device is adapted to continuously update a perimeter of a fracture footprint created in an Earth formation when a fracturing fluid fractures the formation penetrated by a wellbore. Two embodiments of a Volume of Fluid (VOF) software, adapted to be stored in a memory of a computer system, will locate the position of a fracture perimeter during the evolution of that fracture when the software is executed by the processor of the computer system. The two embodiments, called the ‘Marker VOF (MVOF)’ and the ‘Full VOF (FVOF)’ software, will continuously update the perimeter of the fracture footprint by updating a Fill Fraction for each tip element. The MVOF software will use a fill fraction mass balance integral equation to update the Fill Fraction for each tip element, and the FVOF software will use an integrated form of fluid flow equations to update the Fill Fraction for each tip element.

Abstract: The present invention relates to systems and methods useful in subterranean treatment operations. Examples of methods of the present invention include methods for fracturing a portion of a subterranean formation penetrated by a well bore; methods of enhancing production from multiple subterranean formations penetrated by a well bore during a single trip through the well bore; and methods of enhancing production, in real time, from multiple subterranean formations penetrated by a well bore during a single trip through the well bore.

Abstract: In an embodiment, a system may be used to heat a hydrocarbon containing formation. The system may include a conduit placed within an opening in the formation. A conductor may be placed within the conduit. The conductor may provide heat to a portion of the formation. In some embodiments, an electrically conductive material may be coupled to a portion of the conductor in the overburden. The electrically conductive material may lower the electrical resistance of the portion of the conductor in the overburden. Lowering the electrical resistance of the portion of the conductor in the overburden may reduce the heat output of the portion in the overburden. The system may allow heat to transfer from the conductor to a section of the formation.

Abstract: A method of propagating a fracture farther from a well-bore into an oil and/or gas-bearing zone of a target formation while inhibiting growth of the fracture into an adjacent water-bearing zone under or over the oil and/or gas-bearing zone, comprises creating a zone of increased in-situ stress a vertical distance adjacent a target interval and then creating a main fracture in the target interval by, for example, fracturing the target interval with enough fracture fluid and pressure to propagate the main fracture, inter alia, vertically to the zone of increased in-situ stress. When vertical growth of the main fracture reaches the limit set by the zone of increased stress, additional fracture fluid pumped into the target interval tends not to propagate the main fracture vertically beyond that limit and, instead, tends to propagate the main fracture more laterally and farther from the well. Such zone(s) of increased in-situ stress can be created above, below, or both above and below the target interval.

Abstract: Disclosed is a method of determining the extent of recovery of materials injected into oil wells or subsurface formations. The method includes injection of one or more tracers into an oil well or into a formation. Included in the method are the steps of introducing a material of interest into the oil well or into the subsurface formation associated with the bore of the oil well; introducing a tracer into the oil well or into the subsurface formation associated with the bore of the oil well; recovering from the oil well a production fluid, analyzing the production fluid for a concentration of the chemical tracer present in the production fluid; and calculating the amount of material of interest recovered from the oil well using the concentration of the chemical tracer present in the production fluid as a basis for the calculation.

Abstract: The invention describes a method of cement lining a wellbore to enable a fixed sensor internal of the lining to sense characteristics of the external formations surrounding the wellbore using, at the region of the sensor position, a permeability changing device before completion of setting of the cement to create, in use, a permanent fluid communication through the cement lining between the external formation and the sensor.

Abstract: A oil shale formation may be treated using an in situ thermal process. A mixture of hydrocarbons, H2, and/or other formation fluids may be produced from the formation. Heat may be applied to the formation to raise a temperature of a portion of the formation to a pyrolysis temperature. Heat sources may be used to heat the formation. The heat sources may be positioned within the formation in a selected pattern.

Abstract: A casing sensor and methods for sensing using a casing sensor are disclosed. The casing sensor includes a casing shoe and a sensor coupled to the casing shoe. A casing data relay includes a downhole receiver coupled to a well casing and a transmitter coupled to the receiver. The casing sensor may be coupled to the transmitter. A drill string actuator may be controllable through the downhole receiver.

Abstract: The present invention relates to methods of designing a hydraulic fracturing treatment in a subterranean reservoir and methods of treatment. Methods of the invention include quantifying reservoir parameters such as bottomhole temperature and formation permeability, then assessing the temporary variation in temperature of the formation due to the injection of calibration and/or clean up fluids. Treatment fluids are then design based upon the temporary temperature. The fluids are then pumped to treat the reservoir.

Abstract: A portion of at least one fiber is moved from a wellbore into a formation such that the portion is placed to conduct a signal responsive to at least one parameter in the formation. One particular implementation uses fiber optic cable with a process selected from the group consisting of a fracturing process, an acidizing process, and a conformance process.

Abstract: A system and method for sensing and recovering data in a well, according to which one or more sensors are located in an area of the well for sensing data associated with the well and transmitting corresponding signals. A tool is lowered into the area and a receiver mounted on the tool is adapted to receive the signals and transmit the signals to the ground surface.

Abstract: A formation fracturing method with which to mitigate risk to hydrocarbon productivity includes pumping fracturing fluid, during at least part of a fracturing job time period, into a well to fracture a formation; generating signals, within the fracturing job time period, in response to at least one dimension of the fracture; and further pumping fracturing fluid, within the fracturing job time period, into the well in response to the generated signals. Further pumping includes controlling at least one of a pump rate of the further pumping and a viscosity (either fluid viscosity or particulate concentration) of the further pumped fracturing fluid. Control can include comparing a measured magnitude of at least one dimension of the fracture represented by the generated signals with a predetermined modeled magnitude of the same dimension. Tiltmeters can be used to sense fracture height and width, for example.

Abstract: A method for outward and upward growth of a hydraulic fracture along a well bore sandpacked annulus and over a selected rock formation interval along a length of a well bore. The fracture is created along the interval encompassing a multitude of oil and gas saturated sand formations and intervening silt and shale formations for more efficiently producing oil and/or gas from the formations. The method includes creating a linear sourced, cylindrical, stress field by maneuvering an intersection of a fluid friction controlled first pressure gradient and a second pressure gradient of a frac pad fluid traversing through a well bore sandpacked annulus and a hydraulic frac in the adjacent rock formation interval. The first pressure gradient is created by controlling a fluid flow rate of the frac pad fluid through a portion of the sandpacked annulus located above the top of an upwardly propagating hydraulic fracture.

Abstract: The present invention relates to a method of determining the proppant friction generated in a fracture of a subterranean formation during a hydraulic fracturing treatment involving injection stages of pad and of proppant-laden fluids. This method is based on close monitoring of surface pressure to define a “net pressure rate” which defines an increase or decrease of net pressure while the job is being pumped, and then relates it with the pressure changes observed with the onset of proppant stages of varying concentrations.

Abstract: An instrumented perforating gun and associated methods. One aspect provides a recess for placement of instruments on the perforating gun. Another aspect provides methods for perforating and completing a well in a single trip. The present invention also provides an instrumented intergun housing. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A system and method for the measurement of the stresses and pressure perturbations surrounding a well, and a system for computing the optimum location for initiating a hydraulic stress fracture. The technique includes using sensors attached to the wellbore casing connected to a data analyzer. The analyzer is capable of analyzing the stresses on the well system. Using an inverse problem framework for an open-hole situation, the far field stresses and well departure angle are determined once the pressure perturbations and stresses are measured on the wellbore casing. The number of wellbore measurements needed for the inverse problem solution also is determined. The technique is also capable of determining the optimal location for inducing a hydraulic fracture, the effect of noisy measurements on the accuracy of the results, and assessing the quality of a bond between a casing and a sealant.

Abstract: The present invention provides a downhole sample tank and a plurality of micro sample chambers. The micro sample chambers can have at least one window for introduction of visible, near-infrared (NIR), mid-infrared (MIR) and other electromagnetic energy into the tank for samples collected in the micro sample chamber downhole from an earth boring or well bore. The window is made of sapphire or another material capable of allowing electromagnetic energy to pass through the window. The entire micro sample chamber can be made of sapphire or another material capable of allowing electromagnetic energy to pass another material enabling visual inspection or analysis of the sample inside the micro sample chamber. The micro sample chamber enables immediate testing of the sample on location at the surface to determine the quality of the sample in the main sample tank or to enable comprehensive testing of the sample.

Abstract: A method for optimally orienting perforations in a subterranean formation is disclosed, the optimization process being based on establishing the orientation of bedding planes in the formation and, where applicable, hole size effects while determining an orientation of the perforation that balances the stress concentration along the circumference of the cross-section between perforation and bedding plane in further improvements of the method inhomogeneous stress distributions and permeability are included into the optimization process.

Abstract: A method for addressing the problem known as formation breathing occurring during the drilling of a subsea well in an earth formation in performing a series of leak off tests to determine the earth formation fracture propagation pressure and the earth formation fracture reopen pressure and maintaining the hydrostatic pressure on the earth formation in a range between the fracture reopen pressure and the fracture propagation pressure.

Abstract: Hydraulic fracture dimensions and, optionally, fracture closure pressure and time are determined by adding particulate matter that discharges to create an acoustic signal to the proppant, allowing the particulate matter to discharge, and detecting the acoustic signal with geophones or accelerometers. The particulate matter may be spheres or fibers. The discharge may be explosion, implosion, detonation, or rapid combustion or ignition. The discharge may be triggered by fracture closure or by chemical reaction.

Abstract: Changes occurring downhole during a fracturing process can create or reflect pressure signals. Capturing and evaluating such pressure waves during fracturing enables personnel to monitor, in real time or later, what happens downhole. When a fracture extends, a burst of acoustic noise is embodied in a pressure wave or signal, as is noise coming from other sources. By transforming time-based pressure signals to a frequency base, one can monitor this acoustic noise. In a particular implementation, a waterfall plot of frequency spectra at successive time slices of the original signal is used to determine frequency ridges, such as a ridge of decreasing frequencies indicates fracture extension and a ridge of increasing frequencies indicates either closure or proppant backing up in the fracture. Filtering, such as wavelet filtering, can be used. A fracturing process can be controlled in response to determining whether the fracture is extending.

Abstract: A method of designing a hydraulic fracturing treatment in a subterranean reservoir comprising the steps of a) quantifying reservoir parameters including the bottomhole temperature and the formation permeability, b) assessing the temporary variation in temperature of the formation due to the injection of a treatment fluid and c) designing a fluid optimized for said temporary temperature.

Abstract: Changes occurring downhole during a fracturing process can create or reflect pressure signals. Capturing and evaluating such pressure waves during fracturing enables personnel to monitor, in real time or later, what happens downhole. When a fracture extends, a burst of acoustic noise is embodied in a pressure wave or signal, as is noise coming from other sources. By transforming time-based pressure signals to a frequency base, one can monitor this acoustic noise. In a particular implementation, a waterfall plot of frequency spectra at successive time slices of the original signal is used to determine frequency ridges, such as a ridge of decreasing frequencies indicates fracture extension and a ridge of increasing frequencies indicates either closure or proppant backing up in the fracture. Filtering, such as wavelet filtering, can be used. A fracturing process can be controlled in response to determining whether the fracture is extending.

Abstract: A formation fracturing method with which to mitigate risk to hydrocarbon productivity includes pumping fracturing fluid, during at least part of a fracturing job time period, into a well to fracture a formation; generating signals, within the fracturing job time period, in response to at least one dimension of the fracture; and further pumping fracturing fluid, within the fracturing job time period, into the well in response to the generated signals. Further pumping includes controlling at least one of a pump rate of the further pumping and a viscosity (either fluid viscosity or particulate concentration) of the further pumped fracturing fluid. Control can include comparing a measured magnitude of at least one dimension of the fracture represented by the generated signals with a predetermined modeled magnitude of the same dimension. Tiltmeters can be used to sense fracture height and width, for example.

Abstract: Fracture design for well completion includes determining a conductivity profile for the given reservoir to be fractured. Materials needed to obtain this conductivity profile are selected based on their ability to meet the conductivity objective and their rank based on economic value. A further step gives the designer a pumping schedule to be performed on the surface after an initial test in the actual well. This can reduce the iterations required to optimize a fracturing treatment and significantly reduce the redesign process at the well site.

Abstract: The invention relates to a method of controlling the production of oil or gas from a formation (1) comprising that a first and second drilled production well (105, 110) are formed next to each other that extend essentially horizontally, that, at the drilled production wells, a further drilled well (115) is formed that extends between the first and the second drilled production well (105, 110), that the production of oil or gas is initiated, and that, while oil or gas is being produced, a liquid is conveyed to said further drilled well (115) and out into the formation (1) for a first period of time T1. The invention is characterised in that the pore pressure of the formation is influenced during the period T1 with the object of subsequently controlling the formation of fractures along a drilled well, typically across large distances in the reservoir.

Abstract: Characteristics of a reservoir are monitored during a casing drilling operation using a casing drilling assembly that includes a drill bit for drilling a borehole through an earth formation. A casing tubular is coupled with the casing drilling assembly and includes at least one station having at least one slot in the casing tubular. An antenna or sensor, adapted for signal transmission and/or reception, is disposed within the casing tubular and positioned such that the antenna or sensor is aligned with the at least one slotted station. The antenna or sensor is activated during a casing drilling operation to transmit and/or receive a signal.

Abstract: A technique that is usable with a subterranean well includes introducing a fluid into the well in connection with a fluid efficiency test. The technique also includes measuring a temperature versus depth distribution along a section of the well in response to the introduction of the fluid.

Abstract: A new process of fracture stimulating a carbonate reservoir in a subterranean formation to stimulate the production of hydrocarbon fluids from the formation is described. During the process, the composition and reactivity of the fracture stimulation fluid that is injected into the formation surrounding a wellbore is varied from a lower reactive fluid to a higher reactive fluid. The process is designed to stimulate the fracture starting from the tip of the fracture and progressing along the fracture back to the wellbore. The reactivity of the fracture stimulation fluid is increased to maintain optimum stimulation conditions for the formation of conductive flow channels along the faces of the fracture. An optimum fracture stimulation efficiency number, Ff, is used (generally integrated into a fracture simulator computer program) to regulate the fluid composition by reactivity and flow rate, based on formation and fluid parameters.

Abstract: A casing sensor and methods for sensing using a casing sensor are disclosed. The casing sensor includes a casing shoe and a sensor coupled to the casing shoe. A casing data relay includes a downhole receiver coupled to a well casing and a transmitter coupled to the receiver. The casing sensor may be coupled to the transmitter. A drill string actuator may be controllable through the downhole receiver.

Abstract: Compositions and methods for determining the source of treatment fluids being produced from a production formation having multiple zones by introducing a treatment composition having a tracking material into a zone in the subterranean formation, and detecting the tracking material in treatment composition that flows back from the subterranean formation.

Abstract: An excitation event in an oil, gas or geothermal well creates a responsive signal having lower and higher frequency components, which higher frequency component provides information about one or more characteristics of the well. Examples of such characteristics pertaining to a subterranean fracture include: breakdown pressure at fracture initiation, time it takes proppant to reach and to screenout the tip of the fracture, fracture geometry and fracture growth, fracture closure pressure, relative fluid flow through respective perforations, and horsepower requirements to perform a fracture treatment. One excitation event includes creating an excitation signal having a maximum amplitude change occurring within a time t1, which is less than a period t2 of the higher frequency component. Wavelet processing may be used to separate or distinguish the higher frequency waveform from the lower frequency waveform.

Abstract: A method for assessing the fracture pressure closure is proposed. This method includes first injecting a fluid into the formation at a first generally constant rate Q to create a fracture, and then, dropping the pumping rate to significantly smaller feed rate q so that the volume of the fracture becomes constant, in other words. As the fracture volume becomes constant at equilibrium, the well is shut-in. The wellbore pressure is monitored and the closure pressure is determined from the analysis of the wellbore pressure using a time-function of the dimensionless “shut-in” time, defined as the ratio of time since shutting to pumping time. This method provides a way of estimating the friction component of the monitored wellbore pressure due to the fracture tortuosity and friction. It is applicable to the art of fracturing subterranean formations and more particularly to the process of designing and analyzing stimulation treatments.

Abstract: Solutions for the propagation of a hydraulic fracture in a permeable elastic rock and driven by injection of a Newtonian fluid. Through scaling, the dependence of the solution on the problem parameters is reduced to a small number of dimensionless parameters.

Abstract: Disclosed is a method of determining the extent of recovery of materials injected into a oil well comprising the steps of: a) preparing a material to be injected into an oil well; b) admixing therewith a chemical tracer compound at a predetermined concentration; c) injecting the admixture into an oil well; d) recovering from the oil well a production fluid; e) analyzing the production fluid for the concentration of the chemical tracer present in the production fluid; and f) calculating the amount of admixture recovered from the oil well using the concentration of the chemical tracer present in the production fluid as a basis for the calculation. Fluorinated benzoic acids are disclosed as a preferred tracer.