Zonal compositional production rates in commingled gas wells

A production logging tool (PLT) is conveyed within production tubing containing production fluid flow established by zonal fluid flow from formation zones. The PLT measures a flow rate of the production fluid flow at each of a plurality of depths associated with a corresponding one of the zones. A flow rate of the zonal fluid flow from each zone is determined based on the flow rates of the production fluid flow measured at each of the depths. The PLT measures proportions of compositional components of the production fluid flow at each of the depths. A flow rate of each compositional component of the zonal fluid flow from each zone is determined based on the determined flow rate of the zonal fluid flow from each zone and the proportions of compositional components of the production fluid flow measured at each of the depths.

BACKGROUND OF THE DISCLOSURE

Downhole fluid analysis (DFA) in the petroleum industry provides identification of subterranean fluid characterization and variations in real time. DFA has contributed to the finding that hydrocarbons may be compositionally varied rather than homogeneously distributed, such as may be due to gravity, thermal gradients, biodegradation, water stripping, leaky seals, real time charging, multiple charging, and miscible sweep fluid injection, among other possible factors. However, DFA is currently performed via open-hole and cased-hole sampling tools that form a seal around a section of the borehole wall, or around casing perforations. That is, fluids in the formation are brought into the interior of the downhole tool where DFA is performed. As a result, DFA measurements may be restricted to station measurements, which may not be possible in many production logging environments. Moreover, existing DFA tools may have a larger diameter than can be accommodated in some production logging implementations, and may be conveyed within the wellbore via a larger diameter cable than can be accommodated while maintaining a pressure seal on a flowing well.

SUMMARY

Embodiments of this disclosure relate to various methods and devices for determining a flow rate of a zonal fluid flow at multiple depths in a production fluid flow. In one embodiment, a method includes conveying a tool within tubing having a zonal fluid flow and operating the tool to measure a flow rate of the fluid flow at multiple depths. Each of the multiple depths is associated with a corresponding zone of the zonal fluid flow. The method further includes determining a flow rate of the zonal fluid flow from each of the zones based on the flow rates of the fluid flow measured at each of the zone-associated depths and operating the tool to measure proportions of compositional components of the fluid flow at each of the zone-associated depths. The flow rate of each compositional component of the zonal fluid flow from each of the zones is determined based on the determined flow rate of the zonal fluid flow from each of the zones and the proportions of compositional components of the production fluid flow measured at each of the zone-associated depths.

Embodiments of the disclosure are also related to a method including conveying a production logging tool (PLT) within production tubing containing production fluid flow established by zonal fluid flow into the production tubing from zones of a subterranean formation through which the production tubing extends and operating the PLT to measure a flow rate of the production fluid flow at each of multiple depths. Each of the multiple depths is associated with a corresponding zone. The method includes positioning the PLT adjacent one of the zones and then varying a drawdown pressure while operating the PLT to measure proportions of compositional components of the production fluid flow at the PLT-adjacent zone-associated depth and determining a flow rate of each compositional component of the zonal fluid flow from the PLT-adjacent zone. The flow rate of each compositional component of the zonal fluid flow from the PLT-adjacent zone is based on the flow rate of the zonal fluid flow determined from the PLT-adjacent zone and the proportions of compositional components of the production fluid flow measured at the PLT-adjacent zone-associated depth. The condensate banking within the PLT-adjacent zone is assessed based on the determined flow rate of each compositional component of the zonal fluid flow from the PLT-adjacent zone.

Additionally, embodiments of the disclosure is related to an apparatus having a tool operable to be conveyed within tubing containing fluid flow established by zonal fluid flow into the tubing from zones of a subterranean formation through which the tubing extends. The tool includes a flow module operable to measure a flow rate of the fluid flow at each of a plurality of depths associated with a corresponding one of the zones and a sensor operable to measure proportions of compositional components of the fluid flow at each of the zone-associated depths. The apparatus also includes a controller operable to determine a flow rate of the zonal fluid flow from each of the zones based on the flow rates of the fluid flow measured at each of the zone-associated depths and determine a flow rate of each compositional component of the zonal fluid flow from each of the zones based on the determined flow rate of the zonal fluid flow from each of the zones and the proportions of compositional components of the fluid flow measured at each of the zone-associated depths.

DETAILED DESCRIPTION

Furthermore, the terms “casing” and “production tubing” may be used interchangeably within the scope of the present disclosure, contrary to their conventional meanings in the art. Thus, in the context of the present disclosure, including the claims, the term “casing” may indicate a casing, production tubing, a casing through which production tubing extends, and/or production tubing extending through a casing, as these terms are conventionally interpreted. Similarly, the term “production tubing” may indicate production tubing, a casing, production tubing extending through a casing, and/or a casing through which production tubing extends, as these terms are conventionally interpreted.

In addition, one or more aspects of the present disclosure may be applicable and/or readily adaptable to open-hole implementations. Accordingly, any reference herein to “casing” or “production tubing” may also indicate an open, barefoot, or non-cased wellbore, where appropriate, including in the claims.

FIG. 1is a schematic view of at least a portion of apparatus according to one or more aspects of the present disclosure. The apparatus depicted inFIG. 1comprises at least a portion of a downhole tool that is or comprises a production logging tool (“PLT”) and may thus be referred to herein as the PLT100. The PLT100is operable for conveyance within a borehole102that traverses a subterranean formation104. The borehole102may include a casing106through which the PLT100is conveyed via a wireline, slickline, and/or other cable. The PLT100may comprise one or more centralizers108operable to aid in centering and/or otherwise orienting the PLT100within the casing106and/or the borehole102. During production logging, formation fluid (e.g., formation liquid and/or formation gas) may be extracted from different zones, pay zones, and/or layers (hereafter collectively referred to simply as “zones”)105of the formation104. The PLT100is operable to measure, detect, and/or monitor flow rate, composition, and/or other properties and characteristics of the formation fluid as the formation fluid flows to surface101.

The PLT100comprises a housing110that may contain or be at least partially formed by one or more modules. For example, one such module may be an optical module112operable to perform spectroscopic measurements on a sample of the formation fluid114. The optical module112may be disposed at or near an end of the housing110(as shown inFIG. 1), and may be operable to perform Raman spectroscopy, laser induced breakdown spectroscopy, and/or other forms of spectrometry. The optical module112may comprise optics, a laser and/or other light source, and one or more detectors. For example, in implementations in which the optical module112utilizes back-scattering spectroscopy, the laser and/or other light source generates light that is utilized to analyze the formation fluid sample114, where the light that scatters back from the sample114is detected by the one or more detectors. The optics are operable to, for example, communicate the light to and from the sample114. For example, the optics may include a window118that may place the optical module112in optical communication with the formation fluid sample114. As such, the formation fluid sample114adjacent the window118may be analyzed by the optical module112. In the implementation depicted inFIG. 1, the window118is located at the lower end of the PLT100. However, instead of being located at the end of the PLT, or in addition thereto, the window may be located on a sidewall of the housing110.

As schematically depicted inFIG. 1, the PLT100may also comprise a flow module130operable to measure flow rates of the production fluid flow. For example, the flow module130may comprise an impeller or other member132, wherein the production fluid flow may impart rotary and/or other motion to the member132. The imparted motion sensed by one or more detectors of the flow module130may be proportional or otherwise related to the rate of production fluid flow. The flow module130, perhaps with other portions of the PLT100, may be or comprise the PS Platform of Schlumberger®, among other possible commercially available flow rate tools.

The PLT100may also comprise one or more other modules that may operationally support the optical module112and/or the flow module130. For example, the PLT100may comprise a power module120operable to at least partially power the light source(s) and the detector(s) of the optical module112and/or the flow module130. An amplification module122may be included in the PLT100to, for example, amplify electrical and/or other signals output from the optical module112and/or the flow module130. Such signals output from the optical module112may comprise one or more electrical and/or other type of signals that may be representative of light scattered back from the formation fluid sample114that is detected by the one or more detectors of the optical module112. The signals output from the flow module130may comprise one or more electrical and/or other type of signals that may be representative of the flow rate of fluid flow within the casing106that is detected by the one or more detectors of the flow module130. The PLT100may also comprise a telemetry module124operable to provide communication between the PLT100and surface electronics and processing equipment126. For example, the telemetry module124may communicate electrical and/or other signals from the optical module112and/or the flow module130to the surface101.

The PLT100may be utilized in a comingled gas/gas condensate well according to one or more aspects of the present disclosure. The pressures, temperatures, and fluid densities encountered in gas/gas condensate wells may produce a multi-phase flow with a phase separation as the gas and liquid flow to the surface101. The phase separation may produce an annular flow pattern with the gas fraction flowing in the middle of the casing106and the fluid fraction flowing against the sides of the casing106. The centralizers108may centrally position the optical sensor(s) to allow the gas fraction to be separately sampled, avoiding interference from the fluid fraction. The optical module112may be operable to analyze various different types of gases, including methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10), pentane (C5H12), hexane (C6H14), heptane (C7H16), octane (C8H18), nonane (C9H20), decane (C10H22), carbon dioxide (CO2), hydrogen sulfide (H2S), and nitrogen (N2), among others. The optical module112may be operable to analyze liquid fractions comprising hydrocarbons such as n-alkanes and/or other saturates, among other hydrocarbons, and/or aromatics such as benzene and m-xylene, among others. The liquid fraction may also comprise water and/or a multiphase mixture comprising one or more gases, liquid hydrocarbons, and/or water. The optical module112may be operable to perform and/or otherwise utilize Raman spectroscopy in conjunction with a pulsed laser light source to determine the above examples of compositional components in the formation fluid sample114, such as described in implementations described below or otherwise within the scope of the present disclosure.

In implementations in which the above-described back-scattering spectrometry is employed, an axis of the excitation beam of the laser and/or other light source may be collinear with an axis of the detected light. As such, the compositional components of the formation fluid sample114may be determined without the formation fluid sample114passing through an internal flow line of the PLT100. However, other implementations of the PLT100within the scope of the present disclosure are not limited to a back-scattering geometry. For example, the axis of the excitation beam may be spatially and/or angularly offset from the axis of the detected light.

One or more of the above-described modules and/or other modules of the PLT100may also be operable to measure, sense, and/or detect pressure and/or temperature of fluid flow past the PLT. One or more of the above-described modules and/or other modules of the PLT100may also comprise one or more controllers operable to control the functions described above and/or otherwise within the scope of the present disclosure. The one or more controllers may also be operable to communicate and/or work in conjunction with the surface equipment126. The controller(s) of the PLT and/or the surface equipment126may have one or more aspects in common with the processing system described below and shown inFIG. 10.

FIG. 2is a schematic view of an implementation of the PLT100shown inFIG. 1according to one or more aspects of the present disclosure, herein designated by reference numeral200. The PLT200may be substantially similar to the PLT100shown inFIG. 1except as described below.

The PLT200is suspended within a borehole202that traverses a subterranean formation204. The PLT200may be suspended within the borehole202via a multi-conductor cable that is spooled on a winch (not shown) and coupled to surface equipment203at the surface201. In contrast to the PLT100shown inFIG. 1, in which the formation fluid sample114is analyzed outside the PLT100, the PLT200draws the formation fluid sample into the tool and analyzes the sample within the tool. The fluid sample114may be a gas, a liquid, or a combination thereof.

The PLT200may comprise a formation tester206having a probe assembly that may be selectively extendable from the PLT200and/or that may be pressed against the sidewall of the borehole202by one or more back-up pistons (not shown). The probe assembly is thus configured to fluidly couple to an adjacent formation204and draw a formation fluid sample. For example, the formation tester206and/or another module, component, or portion of the PLT200may comprise a pump208operable to pass a formation fluid sample210through the probe assembly and into an internal flow line212of the PLT200.

The PLT200may also comprise a spectroscopy and/or other optical module214that may comprise one or more light sources and/or detectors substantially similar to those described above in reference to the optical module112of the PLT100shown inFIG. 1. The optical module214is in optical communication with the formation fluid sample210within the internal flow line212, such as via a window216. The window216may be substantially similar to the window118described above. After the formation fluid sample210is analyzed utilizing the optical module214, the sample may be expelled from the PLT200through a port (not shown) or directed to one or more sample chambers218.

Implementations within the scope of the present disclosure may not be limited to the PLT100shown inFIG. 1and the PLT200shown inFIG. 2. For example, an implementation of the PLT200shown inFIG. 2may comprise a window and an optical module operable to analyze formation fluid samples within the borehole and outside the tool. Implementations within the scope of the present disclosure may also be utilized in drilling applications, perhaps as or in conjunction with logging-while-drilling (LWD) apparatus and/or measurement-while-drilling (MWD) apparatus. For example, an LWD implementation within the scope of the present disclosure may comprise sampling-while-drilling apparatus, which may form part of an LWD tool string. In such implementations, a formation fluid sample may be drawn into the downhole tool from the formation and analyzed within the tool, in a manner similar to that of the PLT200shown inFIG. 2.

FIG. 3is a schematic view of a laser300that may be utilized as one of the above-described light sources according to one or more aspects of the present disclosure. The laser300may be operable to provide a light source for a variety of spectroscopy techniques, such as Raman spectroscopy, absorption spectroscopy, and/or laser induced breakdown spectroscopy, among others. However, implementations of the PLT100and/or the PLT200utilizing a laser other than the laser300shown inFIG. 3, and/or other light sources, and whether for Raman and/or other types of spectroscopy, are also within the scope of the present disclosure.

The laser300may comprise a monolithic body302having a first end304and a second end306. The first end304and the second end306may be polished. The monolithic body302may be rod-shaped, and may comprise a solid-state gain medium308having a first end310and a second end312. The solid-state gain medium308may comprise a solid-state material, such as a chromium-doped beryllium aluminum oxide crystal (Cr3+:BeAl2O4) (“alexandrite”), a neodymium-doped yttrium aluminum garnet crystal (Nd:Y3Al5O12) (“Nd:YAG”), and/or other materials. The solid-state gain medium308may comprise one or more dopant elements, such as neodymium (Nd), ytterbium (Yb), erbium (Er), titanium (Ti), thulium (Tm), and/or other dopants. The solid-state gain medium308may provide a photon gain when a pump source314creates a population inversion in the solid-state gain medium308.

A first reflector316and a second reflector318may be disposed on the first end304and the second end306of the monolithic body302, respectively. Thus, the solid-state gain medium308may be disposed between the first reflector316and the second reflector318. The first reflector316and the second reflector318may provide an optical resonator, reflecting light in a closed path.

The first and second reflectors316and318may be diffusion bonded to the first and second ends304and306, respectively, and/or may be or comprise one or more film coatings. The first reflector316may have a reflectivity of about 100 percent (e.g., 95%, 98%, 99%, 99.9%, etc.), and may thus substantially reflect light emitted from the solid-state gain medium308. The second reflector318may have a reflectivity of less than 100 percent (e.g., 80%, 90%, etc.), such as may permit the passage of a laser pulse. The reflective surfaces of the first and second reflectors316and318may be substantially parallel or curved. For example, the first and second reflectors316and318may be curved such that they are substantially confocal, having curvature radii that are substantially equal to the distance by which they are separated, or they may be substantially concentric, having curvature radii that are substantially equal to half of the distance by which they are separated.

The monolithic body302may comprise a Q-switch320. The Q-switch320may be a passive Q-switch, such as a saturable absorber, for example. A coefficient of thermal expansion of the Q-switch320may be substantially equal to a coefficient of thermal expansion of the solid-state gain medium308. The Q-switch320may be implemented utilizing a Cr:YAG crystal. One end322of the Q-switch320may be diffusion bonded, optical contact bonded, and/or otherwise non-adhesively bonded to the second end312of the solid-state gain medium308. In such implementations, the second reflector318may be disposed on an opposing end324of the Q-switch320. In other implementations, the second reflector318may be disposed on the second end312of the solid-state gain medium308. The Q-switch320may prevent the laser300from outputting a laser pulse until a population inversion in the solid-state gain medium308reaches a peak and/or otherwise predetermined level.

The pump source314may be or comprise a lamp pump source, such as a flash lamp and/or an arc lamp, among others, and/or a light emitting diode, a diode laser, and/or other example sources. The pump source314may be adjacent the monolithic body302. Longitudinal axes of the pump source314and the solid-state gain medium308may be substantially parallel. The pump source314may comprise a glass, quartz, and/or otherwise substantially transparent tube326filled with xenon, krypton, and/or other gases. The pump source314may be coupled to a capacitor and/or another electrical power source. During operation, an electric current may be delivered to the gas within the tube326via the electrical power source to cause the gas to ionize and an arc to form through the gas. The pump source314may have an arc length of about 50 mm, or may range between about 40 mm and about 60 mm, although other arc lengths are also within the scope of the present disclosure. The arc may emit a flash of light having a duration of about 100 μs, or ranging between about 10 μs and about 1000 μs, or the arc may emit light continuously. The temperature of the arc may be about 10,000° C., or may range between about 9,000° C. and about 11,000° C., although other temperatures are also within the scope of the present disclosure.

A reflective cavity328may substantially enclose the monolithic body302and the pump source314. The reflective cavity328may be defined by a glass and/or otherwise substantially transparent cylinder330that may be at least partially covered by a diffuse reflector332, such as may comprise barium sulfate, Teflon®, and/or other materials. The reflective cavity328may be an elliptical mirror. A first end334of the reflective cavity328may comprise an aperture (not shown) adjacent the first end304of the monolithic body302. A mount336may extend through the aperture to hold and/or substantially align the monolithic body302in the reflective cavity328. The mount336may receive and/or otherwise fix the first end304of the monolithic body302. Another mount may extend through another aperture of the reflective cavity328, such as to receive and/or otherwise fix the monolithic body302along the Q-switch320.

A second end338of the reflective cavity328may be at least partially transparent and/or comprise an aperture that may enable the laser300to output a laser pulse through the second end338of the reflective cavity328. The reflective cavity328and the mount336may be disposed in a housing340. The mount336may be coupled to the housing340. The housing340may be disposed within a downhole tool such as, for example, the PLT100shown inFIG. 1, the PLT200shown inFIG. 2, and/or other downhole tools within the scope of the present disclosure.

The pump source314may supply energy to the solid-state gain medium308by emitting light. The diffuse reflector332of the reflective cavity328may reflect the light emitted by the pump source314. The light may thus excite atoms in the solid-state gain medium308until a population inversion occurs in the solid-state gain medium308(i.e., a number of electrons in an excited state exceed a number of electrons in a lower energy state). When the population inversion occurs, the solid-state gain medium308emits more photons than the solid-state gain medium308absorbs. The reflective cavity328and the first and second reflectors316and318amplify the photons emitted by the solid-state gain medium308, thus causing a laser pulse to be transmitted through the second reflector318.

The Q-switch320may prevent the laser300from outputting or transmitting the laser pulse until the population inversion in the solid state gain medium308reaches a peak and/or otherwise predetermined level. For example, the Q-switch320may be a saturable absorber, and may thus be substantially non-transparent until the population inversion reaches the predetermined level. Once the population inversion reaches the predetermined level, the Q-switch320may become at least partially transparent, and the laser pulse may pass through the Q-switch320and the second reflector318.

When the laser300is exposed to temperatures between about room temperature and about 200° C., for example, the laser300outputs laser pulses having pulse energies substantially independent of the temperature, such as about 8 mJ, 14 mJ, or 22 mJ. For example, from about room temperature to about 200° C., the laser300may output laser pulses having pulse energies with a standard deviation within about 10 percent. The deviations may be substantially attributable to random fluctuations that occur during operation regardless of the temperature, such as creation of the arc in the pump source314, recombination and continuum emission events producing light via the arc, and emitted photon directions from the events, for example. Thus, the laser300may output laser pulses having substantially constant pulse energies when exposed to temperatures between about room temperature and about 200° C. The laser300may output the laser pulses even when subjected to shocks and/or vibrations.

One or more aspects of the apparatus and/or methods described above may be utilized in conjunction with various methods of production logging interpretation. For example, they may be utilized to determine zone-by-zone production rates of water, oil and/or gas, such as by utilizing a combination of velocity measurements, velocity slip correlations, and holdup (void fraction) measurements. One or more aspects of the apparatus and/or methods described above may also be utilized in conjunction with apparatus and/or methods for measuring the downhole molecular composition of the commingled production of gas. For example, apparatus and/or methods within the scope of the present disclosure may be utilized to assign detected molecules to the production from each of a plurality of zones. Once supplied with the composition of the gas from each zone, the source of rich gas, lean gas, CO2contaminated gas, and/or N2contaminated gas (among others) may be determined. This information may then be utilized to manage the well and/or reservoir in the formation, such as to maximize wanted gas production and minimize unwanted gas production. For example, zones identified as being unusually rich in CO2may not support commercial goals, and may thus be sequestered downhole while lean gas breakthrough in condensate sweep operations may be identified, and injection gas may be redeployed to un-swept zones.

For example, in a gas producing well having three zones, a production logging tool (such as the PLT100shown inFIG. 1, the PLT200shown inFIG. 2, and/or other production logging tools within the scope of the present disclosure) may be operated to measure the total volumetric flow rate Q1, Q2, and Q3of production fluid within the production tubing at respective depths just above each of the three zones, respectively. These depths will be referred to herein as zone-associated depths. The volumetric inflow from each of the three zones may then determined as set forth below in Equations (1), (2), and (3).
q1=Q1(1)
q2=Q2−Q1(2)
q3=Q3−Q2(3)
For the sake of clarity, the volumetric flow rate Qnwithin the production tubing may be referred to herein as a production fluid flow rate, and the volumetric flow rate qnof inflow from a zone into the production tubing may be referred to herein as zonal fluid flow rate. The following description is also presented in the context of the produced formation fluid comprising a binary gas mixture of methane and ethane, although this will seldom be the case in reality.

The PLT may also be operated to obtain a signal proportional to the number density fractions of methane and ethane, measured at each of the zone-associated depths. These fractions will be referred to herein as f1methane, f1ethane, f2methane, f2ethane, f3methane, and f3ethane. Equal moles of gases occupy the same volume at a given pressure (from the ideal gas law), so the production fluid flow rates associated with each zone n may be represented as set forth below in Equation (4).

The left- and right-hand sides of the Equation (4) give the production fluid flow rates of methane and ethane, respectively, as set forth below in Equations (5) and (6).

To a first order approximation, the zonal fluid flow rate of methane and ethane may then be determined as set forth below in Equations (7), (8), and (9).
qnmethane=Qnmethane−Qn−1methane(7)
qnethane=Qnethane−Qn−1ethane(8)
Q0methane=Q0ethane=0  (9)

However, according to the ideal gas law, borehole pressure changes from zone to zone will cause corresponding changes in volume. This change in volume might be apparent as a change in flow rate, which might be interpreted as an erroneous entry. Therefore, the PLT may be operated to measure the pressure Pnat each of the zone-associated depths, which may be normalized by a factor Pn/Pref. Changes in temperature and compression factor (departures from the ideal gas law) may similarly be accounted for by factors Tref/Tnand zref/zn. The reference conditions may be standard conditions, although a downhole reference or another reference may also be utilized. Applying such normalization factors to Equations (5) and (6) results in Equations (10) and (11) set forth below.

Assuming the number of compositional components is y (so that, in the above example, y=2), and yxis the xthcompositional component (where y1is methane and y2is ethane in the above example), Equations (10) and (11) may be generalized as set forth below in Equation (12).

Thus, the zonal contribution of the nthzone of the xthcompositional component will be as set forth below in Equation (13).
qnx=Qnx−Qn−1x(13)
where Q0xis zero.

In some implementations within the scope of the present disclosure, the Raman spectrometer and/or other sensor of the optical module of the PLT (such as the optical module112of the PLT100shown inFIG. 1and/or the optical module214of the PLT200shown inFIG. 2) may sense compositional component proportions in terms of mass fractions. In such implementations, a relative molecular mass term Mrmay be included in the above technique. For example, if wnmethaneand wnethanefractions represent the respective mass actions of methane and ethane associated with zone n, Equation (4) may be modified as set forth below in Equation (14).

In some implementations within the scope of the present disclosure, the Raman spectrometer and/or other compositional component sensor may be unable to detect and quantify some of the compositional components present in the production fluid flow. The technique described above may, in such instances, proportionally assign the missing proportions to those that have been detected, which may thus preserve a valid ratio of the detected components.

As described above, the compositional component proportions may be determined via operation of the PLT's Raman spectroscopy sensor(s). However, sensors such as those that may be utilized for infrared absorption spectroscopy, gas chromatography, and/or nuclear magnetic resonance, among others, may be similarly and/or simultaneously utilized to return a signal proportional to or otherwise representative of the fraction of each compositional component in the comingled production fluid flow.

As also described above, this technique is not limited to the gases methane and ethane utilized for illustration in the equations above, and may be applied to other compositional components, such as propane, butane, pentane, hexane, heptane, octane, nonane, decane, carbon dioxide, nitrogen, and/or hydrogen sulfide, among others. Moreover, this technique is not limited to gases, and may be applied or readily adapted for utilization with liquid fractions containing hydrocarbons, such as n-alkanes and/or other saturates, as well as benzene, m-xylene, and/or other aromatics, among other hydrocarbons. In such implementations, the liquid fraction may also comprise water, or a multiphase mixture containing gas, liquid hydrocarbon, and/or water.

Table 1 set forth below presents an example Raman spectrum of a natural gas mixture comprising methane, ethane, propane, and CO2.

TABLE 1Example Raman SpectrumCompositionalWavenumberRamanComponent(cm−1)IntensityMethane2910~115,000CO21383~5,200Ethane993~10,600Propane869~3,500
The units for the Raman intensity are arbitrary, such as a count of photons, among other examples.

The Raman signal from each molecule is linearly proportional to the density of the compositional component in the mixture. Analysis of the sample composition of the comingled gas is based on linear superposition in which the Raman spectrum of the mixture is equal to the weighted sum of the individual species in the mixture. A calibration procedure may establish the relationship between the measured response of an individual detector channel and the concentration of a particular compositional component in the mixture.

Raman spectrometry utilizes a high-brightness, narrow-band laser source, such as that shown inFIG. 3. Raman spectrometry may be utilized in some implementations within the present disclosure where, for example, an internal flowline may not be available for spectrometry. Raman photons are scattered isotropically, therefore the photons can be collected in a back-scattering geometry along the same axis as the excitation beam. Raman spectrometry may also be utilized in implementations without prior phase-separation of gas and water, because the water Raman band does not interfere with the Raman bands of any of the listed mixture species. Nonetheless, implementations within the scope of the present disclosure may instead (or additionally) utilize an infrared spectrometer, such as to perform an absorption measurement that, through application of Beer's law, may be utilized to determine the compositional component density/proportions.

There are many applications within the scope of the present disclosure that may utilize the techniques described above and/or the results thereof. Referring toFIG. 4, for example, a lean gas substantially comprising methane, ethane, nitrogen, carbon dioxide, and/or another sweeping fluid may be pumped into an injector well410by surface equipment415to sweep gas condensate from zones430-432of a formation F to a producing well420. In one of the zones431, the sweeping fluid from the injector well410may break through into the producing well420. The breakthrough may be determined utilizing the surface equipment415. PLT analysis according to one or more aspects of the present disclosure may be utilized to measure the ratios of compositional components at depths associated with each of the zones430-432to determine that the breakthrough has occurred in the one of the zones, depicted as zone431inFIG. 4. The zone431may then be shut-in by cementing and/or other means. As a result of the shut in, less compressed gas, water, and/or other sweeping agent may return to the surface through the production well420, and condensate swept from the other zones430and432may thus be increased.

FIG. 5provides another example application that may utilize one or more aspects of techniques within the scope of the present disclosure. InFIG. 5, a well510is depicted extending through the formation F, including intersecting sand bodies and/or other zones520,530,540, and550having variable CO2and/or H2S content. The net caloric content of the comingled production fluid flow within the well510may be lowered by CO2content, and surface equipment515may have a maximum H2S amount that can be safely handled. PLT analysis according to one or more aspects of the present disclosure may be utilized to determine the CO2and/or H2S proportion of the zonal fluid flow from each of the sand bodies and/or zones520,530,540, and550. For example, operation of a PLT within the scope of the present disclosure may determine that the CO2and/or H2S proportion of the sand bodies and/or zones520,530, and540may be less than 10% or some other predetermined threshold, while the CO2and/or H2S proportion of the sand body and/or zone550may be determined to be greater than 20% or some other predetermined threshold. Accordingly, the sand body and/or zone550may then be shut-in by cementing and/or other means555. As a result, more CO2and/or H2S may be sequestered downhole instead of being separated and/or otherwise handled by the surface equipment515.

FIG. 6provides another example application that may utilize one or more aspects of techniques within the scope of the present disclosure. InFIG. 6, a well610is depicted intersecting zones620,630,640, and650of the formation F. The upper zone650is depicted as including a gas condensate bank655, and the zones640and630similarly include respective gas condensate banks645and635. However, the condensate banks635,645, and655are of varying size. The condensate banks635,645, and655may occur if the corresponding zones630,640, and650become retrograde, such that reducing the drawdown pressure (the difference between formation pressure and pressure in the borehole and/or production tubing) results in an increase in liquid production, as opposed to zone620where the reduction in drawdown pressure results in an increase in gas production. In the retrograde zones630,640, and650, the liquid does not flow through the formation F as quickly as the gas flows through the zone620, which results in an accumulation of condensate choking the flow within the zone. Retrograde zones may present challenges in the context of modeling and real-time reservoir management.

However, one or more aspects of the present disclosure may be utilized in such scenarios. For example, the PLT may be positioned adjacent the condensate bank635,645, or655, and the drawdown pressure may be varied while utilizing the PLT to monitor the resulting variations in compositional component proportions of the associated zonal fluid flow. Variation of the drawdown pressure may be accomplished via operation of one or more chokes and/or other components of the associated surface equipment615. Consequently, the onset and/or degree of condensate banking may be measured on a zone-by-zone basis. This information may also be utilized to optimize the drawdown rate to, for example, maximize efficiencies of the system and/or minimize the production of unwanted gas and/or certain compositional components.

FIG. 7is a flow-chart diagram of at least a portion of a method700according to one or more aspects of the present disclosure. The method700comprises measuring (710) a volumetric flow rate of production fluid flow at each of a plurality of depths associated with a corresponding one of a plurality of zones of a formation. Such measuring may be performed by operation of a PLT, such as the PLT100shown inFIG. 1, the PLT200shown inFIG. 2, and/or another PLT within the scope of the present disclosure. The volumetric flow rate of the zonal fluid flow from each of the zones is then determined (720) based on the volumetric flow rates of the production fluid flow measured at each of the zone-associated depths. Such determination (720) may be according to the equations set forth above.

The method700also comprises measuring (730) proportions of compositional components of the production fluid flow at each of the zone-associated depths. Such measurement (730) may be performed by the same PLT utilized to measure the production fluid flow rates at each of the zone-associated depths, perhaps simultaneously, such as during a continuous or other conveyance of the PLT down (or up) the well. The measurements (710and730) may also be performed during different logging runs with potentially different downhole tools in the tool string. The compositional component proportions measured (730) at each of the zone-associated depths may be returned from the compositional component sensor of the PLT based on volume, number density, mass fractions, and/or otherwise. The volumetric flow rate of each compositional component of the zonal fluid flow from each of the zones may then be determined (740) based on the determined volumetric flow rate of the zonal fluid flow from each of the zones and the proportions of compositional components of the production fluid flow measured at each of the zone-associated depths. Such determination (740) may be according to the equations set forth above.

FIG. 8is a flow-chart diagram of at least a portion of a method800according to one or more aspects of the present disclosure. The method800may be substantially similar to, or have one or more aspects in common with, the method700shown inFIG. 7. For example, the method800comprises measuring (810) a volumetric flow rate of production fluid flow at each of a plurality of depths associated with a corresponding one of a plurality of zones of a formation. Such measuring (810) may be performed by operation of a PLT, such as the PLT100shown inFIG. 1, the PLT200shown inFIG. 2, and/or another PLT within the scope of the present disclosure. The volumetric flow rate of the zonal fluid flow from each of the zones is then determined (820) based on the volumetric flow rates of the production fluid flow measured (810) at each of the zone-associated depths. Such determination (820) may be according to the equations set forth above.

The method800also comprises measuring (830) proportions of compositional components of the production fluid flow at each of the zone-associated depths. Such measurement (830) may be performed by the same PLT utilized to measure the production fluid flow rates at each of the zone-associated depths, perhaps simultaneously, such as during a substantially continuous or other conveyance of the PLT down (or up) the well. The measurements (810and830) may also be performed during different logging runs with potentially different downhole tools in the tool string. The compositional component proportions measured (830) at each of the zone-associated depths may be returned from the compositional component sensor of the PLT based on volume, number density, mass fractions, and/or otherwise.

The volumetric flow rate of each compositional component of the zonal fluid flow from each of the zones may then be determined (840) based on the determined volumetric flow rate of the zonal fluid flow from each of the zones and the proportions of compositional components of the production fluid flow measured at each of the zone-associated depths. Such determination (840) may be according to the equations set forth above.

However, the method800may further comprise conveying (850) the PLT within casing and/or production tubing through which the production fluid flow is established by the zonal fluid flow into the casing and/or production tubing. Such conveyance may be via any means and remain within the scope of the present disclosure, such as slickline, wireline, coiled tubing, pipe, and/or other conveyance means.

The method800may further comprise operating the PLT to measure (860) pressure and/or temperature of the production fluid flow at each of the zone-associated depths. This information may be utilized when the compositional component zonal fluid flow rates are determined (840) for each zone. For example, the method800may further comprise determining a compression factor of the production fluid flow at each of the zone-associated depths based on the pressure and temperature of the production fluid flow measured at each of the zone-associated depths. Determining (840) the volumetric flow rate of each compositional component of the zonal fluid from each of the zones may then be further based on the pressure and temperature of the production fluid flow measured (860) at each of the zone-associated depths and the compression factor of the production fluid determined (870) at each of the zone-associated depths. Again, such determination (840) may be according to the equations set forth above.

Determining (820) the volumetric flow rate of the zonal fluid flow from each of the zones based on the volumetric flow rates of the production fluid flow measured at each of the zone-associated depths may comprise comparing the volumetric flow rates of the production fluid flow measured at neighboring ones of the zone-associated depths. Again, such determination (820) may be according to the equations set forth above.

The method800may further comprise operating (880) surface equipment to establish the zonal fluid flow into the production fluid flow. For example, such operation (880) may entail operation of one or more chokes and/or other components of the surface equipment, such as the surface equipment126shown inFIG. 1, the surface equipment203shown inFIG. 2, the surface equipment415shown inFIG. 4, the surface equipment515shown inFIG. 5, and/or the surface equipment615shown inFIG. 6.

The method800may further comprise varying (890) a drawdown pressure based on the determined volumetric flow rate of at least one of the compositional components of the zonal fluid flow from at least one of the zones. Such variation (890) may be utilized to optimize production from one or more of the zones, and may entail operation of one or more chokes and/or other components of the surface equipment, such as the surface equipment126shown inFIG. 1, the surface equipment203shown inFIG. 2, the surface equipment415shown inFIG. 4, the surface equipment515shown inFIG. 5, and/or the surface equipment615shown inFIG. 6.

FIG. 9is a flow-chart diagram of at least a portion of a method900according to one or more aspects of the present disclosure. The method900may be substantially similar to, or have one or more aspects in common with, the method700shown inFIG. 7and/or the method800shown inFIG. 8. For example, the method900comprises measuring (910) a volumetric flow rate of production fluid flow at each of a plurality of depths associated with a corresponding one of a plurality zones of a formation. Such measuring (910) may be performed by operation of a PLT, such as the PLT100shown inFIG. 1, the PLT200shown inFIG. 2, and/or another PLT within the scope of the present disclosure. The volumetric flow rate of the zonal fluid flow from each of the zones is then determined (920) based on the volumetric flow rates of the production fluid flow measured (910) at each of the zone-associated depths. Such determination (920) may be according to the equations set forth above.

The method900also comprises positioning the PLT adjacent a zone of interest and then varying (930) drawdown pressure. The zone of interest may be a retrograde zone and/or a zone suspected to have developed excessive condensate banking. While the drawdown pressure is varied (930), the PLT may be operated to measure (940) proportions of compositional components of the production fluid flow at the PLT-adjacent zone-associated depth and determine (950) a volumetric flow rate of each compositional component of the zonal fluid flow from the PLT-adjacent zone. Such determination (950) may be based on the determination (920) of the volumetric flow rate of the zonal fluid flow from the PLT-adjacent zone and the proportions of compositional components of the production fluid flow measured (940) at the PLT-adjacent zone-associated depth, such as according to the equations set forth above. Condensate banking within the PLT-adjacent zone may then be assessed (960) based on the determined (950) volumetric flow rate of one or more compositional components of the zonal fluid flow from the PLT-adjacent zone. The method900may further comprise shutting-in (965) the PLT-adjacent zone based on the determination (950) of the volumetric flow rate of at least one of the compositional components of the zonal fluid flow from the PLT-adjacent zone and/or the assessment (960) of condensate banking within the PLT-adjacent zone.

The measurement (940) of the proportions of the compositional components of the production fluid flow at PLT-adjacent zone-associated depth may be performed by the same PLT (after positioning (930)) utilized to measure (910) the production fluid flow rates at each of the zone-associated depths. The compositional component proportions measured (940) at the PLT-adjacent zone-associated depth may be returned from the compositional component sensor of the PLT based on volume, number density, mass fractions, and/or otherwise.

The variation (930) of the drawdown pressure may comprise operating surface equipment in fluid communication with the production tubing. For example, such operation may entail operation of one or more chokes and/or other components of the surface equipment, such as the surface equipment126shown inFIG. 1, the surface equipment203shown inFIG. 2, the surface equipment415shown inFIG. 4, the surface equipment515shown inFIG. 5, and/or the surface equipment615shown inFIG. 6.

The method900may further comprise measuring (970) pressure and temperature of the production fluid flow at the PLT-adjacent zone-associated depth, such as via operation of the PLT. A compression factor of the production fluid flow at the PLT-adjacent zone-associated depth may then be determined (980) based on the pressure and temperature of the production fluid flow measured (970) at the PLT-adjacent zone-associated depth. The determination (950) of the volumetric flow rate of each compositional component of the zonal fluid flow from the PLT-adjacent zone may thus be further based on the pressure and temperature of the production fluid flow measured (970) at the PLT-adjacent zone-associated depth and the compression factor of the production fluid determined (980) at the PLT-adjacent zone-associated depth.

The method900may further comprise conveying (990) the PLT within the casing and/or production tubing through which the production fluid flow is established by zonal fluid flow. Such conveyance (990) may be via any means and yet remain within the scope of the present disclosure, such as slickline, wireline, coiled tubing, pipe, and/or other conveyance means.

The method900may further comprise operating (995) surface equipment to establish the zonal fluid flow into the production fluid flow. For example, such operation (995) may entail operation of one or more chokes and/or other components of the surface equipment, such as the surface equipment126shown inFIG. 1, the surface equipment203shown inFIG. 2, the surface equipment415shown inFIG. 4, the surface equipment515shown inFIG. 5, and/or the surface equipment615shown inFIG. 6.

FIG. 10is a block diagram of an example processing system1000that may execute example machine-readable instructions used to implement one or more of the methods and/or processes described herein, and/or to implement the example downhole tools described herein. The processing system1000may be or comprise, for example, one or more processors, one or more controllers, one or more special-purpose computing devices, one or more servers, one or more personal computers, one or more personal digital assistant (PDA) devices, one or more smartphones, one or more internet appliances, and/or any other type(s) of computing device(s). One or more of the components of the example processing system1000may be implemented within the PLT100and/or surface equipment126shown inFIG. 1, and/or the PLT200and/or surface equipment203shown inFIG. 2.

The system1000comprises a processor1012such as, for example, a general-purpose programmable processor. The processor1012includes a local memory1014, and executes coded instructions1032present in the local memory1014and/or in another memory device. The processor1012may execute, among other things, machine-readable instructions to implement the methods and/or processes described herein. The processor1012may be, comprise or be implemented by any type of processing unit, such as one or more Intel® microprocessors, one or more microcontrollers from the ARM® and/or picoPower® families of microcontrollers, one or more embedded soft/hard processors in one or more FPGAs, etc. Of course, other processors from other families are also appropriate.

The processor1012is in communication with a main memory including a volatile (e.g., random access) memory1018and a non-volatile (e.g., read only) memory1020via a bus1022. The volatile memory1018may be, comprise or be implemented by static random access memory (SRAM), synchronous dynamic random access memory (SDRAM), dynamic random access memory (DRAM), RAMBUS dynamic random access memory (RDRAM) and/or any other type of random access memory device. The non-volatile memory1020may be, comprise or be implemented by flash memory and/or any other desired type of memory device. One or more memory controllers (not shown) may control access to the main memory1018and/or1020.

The processing system1000also includes an interface circuit1024. The interface circuit1024may be, comprise or be implemented by any type of interface standard, such as an Ethernet interface, a universal serial bus (USB) and/or a third generation input/output (3GIO) interface, among others.

One or more input devices1026are connected to the interface circuit1024. The input device(s)1026permit a user to enter data and commands into the processor1012. The input device(s) may be, comprise or be implemented by, for example, a keyboard, a mouse, a touchscreen, a track-pad, a trackball, an isopoint and/or a voice recognition system, among others.

One or more output devices1028are also connected to the interface circuit1024. The output devices1028may be, comprise or be implemented by, for example, display devices (e.g., a liquid crystal display or cathode ray tube display (CRT), among others), printers and/or speakers, among others. Thus, the interface circuit1024may also comprise a graphics driver card.

The interface circuit1024also includes a communication device such as a modem or network interface card to facilitate exchange of data with external computers via a network (e.g., Ethernet connection, digital subscriber line (DSL), telephone line, coaxial cable, cellular telephone system, satellite, etc.).

The processing system1000also includes one or more mass storage devices1030for storing machine-readable instructions and data. Examples of such mass storage devices1030include floppy disk drives, hard drive disks, compact disk drives and digital versatile disk (DVD) drives, among others.

The coded instructions1032may be stored in the mass storage device1030, the volatile memory1018, the non-volatile memory1020, the local memory1014and/or on a removable storage medium, such as a CD or DVD1034.

As an alternative to implementing the methods and/or apparatus described herein in a system such as the processing system ofFIG. 10, the methods and or apparatus described herein may be embedded in a structure such as a processor and/or an ASIC (application specific integrated circuit).

In view of the entirety of the present disclosure, including the figures, a person having ordinary skill in the art will recognize that the present disclosure introduces a method comprising: conveying a tool within a tubing comprising a zonal fluid flow; operating the tool to measure a flow rate of the fluid flow at each of a plurality of depths, wherein each of the plurality of depths is associated with a corresponding zone of the zonal fluid flow; determining a flow rate of the zonal fluid flow from each of the zones based on the flow rates of the fluid flow measured at each of the zone-associated depths; operating the tool to measure proportions of compositional components of the fluid flow at each of the zone-associated depths; and determining a flow rate of each compositional component of the zonal fluid flow from each of the zones based on: the determined flow rate of the zonal fluid flow from each of the zones; and the proportions of compositional components of the production fluid flow measured at each of the zone-associated depths.

The method may further comprise: operating the PLT to measure pressure and temperature of the production fluid flow at each of the zone-associated depths; and determining a compression factor of the production fluid flow at each of the zone-associated depths based on the pressure and temperature of the production fluid flow measured at each of the zone-associated depths; wherein determining the flow rate of each compositional component of the zonal fluid flow from each of the zones may be further based on: the pressure and temperature of the production fluid flow measured at each of the zone-associated depths; and the determined compression factor of the production fluid at each of the zone-associated depths.

Operating the PLT to measure proportions of the compositional components of the production fluid flow at each of the zone-associated depths may comprise operating the PLT to measure volumetric proportions of the compositional components of the production fluid flow at each of the zone-associated depths.

Operating the PLT to measure proportions of the compositional components of the production fluid flow at each of the zone-associated depths may comprise operating the PLT to measure mass proportions of the compositional components of the production fluid flow at each of the zone-associated depths.

Determining the flow rate of the zonal fluid flow from each of the zones based on the flow rates of the production fluid flow measured at each of the zone-associated depths may comprise comparing the flow rates of the production fluid flow measured at neighboring ones of the zone-associated depths.

The method may further comprise operating surface equipment in fluid communication with the production tubing to establish the zonal fluid flow into the production tubing. Operating the surface equipment may comprise operating a choke.

The method may further comprise shutting-in at least one of the zones based on the determined flow rate of at least one of the compositional components of the zonal fluid flow from that at least one zone.

The method may further comprise varying a drawdown pressure based on the determined flow rate of at least one of the compositional components of the zonal fluid flow from at least one of the zones. Varying the drawdown pressure may comprise operating surface equipment in fluid communication with the production tubing. Operating the surface equipment may comprise operating a choke.

The present disclosure also introduces a method comprising: conveying a production logging tool (PLT) within production tubing containing production fluid flow established by zonal fluid flow into the production tubing from zones of a subterranean formation through which the production tubing extends; operating the PLT to measure a flow rate of the production fluid flow at each of a plurality of depths associated with a corresponding one of the zones; determining a flow rate of the zonal fluid flow from each of the zones based on the flow rates of the production fluid flow measured at each of the zone-associated depths; positioning the PLT adjacent one of the zones and then varying a drawdown pressure while: operating the PLT to measure proportions of compositional components of the production fluid flow at the PLT-adjacent zone-associated depth; and determining a flow rate of each compositional component of the zonal fluid flow from the PLT-adjacent zone based on: the determined flow rate of the zonal fluid flow from the PLT-adjacent zone; and the proportions of compositional components of the production fluid flow measured at the PLT-adjacent zone-associated depth; and assessing condensate banking within the PLT-adjacent zone based on the determined flow rate of each compositional component of the zonal fluid flow from the PLT-adjacent zone.

The method may further comprise: operating the PLT to measure pressure and temperature of the production fluid flow at the PLT-adjacent zone-associated depth; and determining a compression factor of the production fluid flow at the PLT-adjacent zone-associated depth based on the pressure and temperature of the production fluid flow measured at the PLT-adjacent zone-associated depth; wherein determining the flow rate of each compositional component of the zonal fluid flow from the PLT-adjacent zone may be further based on: the pressure and temperature of the production fluid flow measured at the PLT-adjacent zone-associated depth; and the determined compression factor of the production fluid at the PLT-adjacent zone-associated depth.

Operating the PLT to measure proportions of the compositional components of the production fluid flow at the PLT-adjacent zone-associated depth may comprise operating the PLT to measure volumetric proportions of the compositional components of the production fluid flow at the PLT-adjacent zone-associated depth.

Operating the PLT to measure proportions of the compositional components of the production fluid flow at the PLT-adjacent zone-associated depth may comprise operating the PLT to measure mass proportions of the compositional components of the production fluid flow at the PLT-adjacent zone-associated depth.

The method may further comprise shutting-in the PLT-adjacent zone based on the determined flow rate of at least one of the compositional components of the zonal fluid flow from the PLT-adjacent zone.

Varying the drawdown pressure may comprise operating surface equipment in fluid communication with the production tubing. Operating the surface equipment may comprise operating a choke.

The present disclosure also introduces an apparatus comprising: a production logging tool (PLT) operable to be conveyed within production tubing containing production fluid flow established by zonal fluid flow into the production tubing from zones of a subterranean formation through which the production tubing extends, wherein the PLT comprises: a flow module operable to measure a flow rate of the production fluid flow at each of a plurality of depths associated with a corresponding one of the zones; and a sensor operable to measure proportions of compositional components of the production fluid flow at each of the zone-associated depths; and a controller operable to: determine a flow rate of the zonal fluid flow from each of the zones based on the flow rates of the production fluid flow measured at each of the zone-associated depths; and determine a flow rate of each compositional component of the zonal fluid flow from each of the zones based on: the determined flow rate of the zonal fluid flow from each of the zones; and the proportions of compositional components of the production fluid flow measured at each of the zone-associated depths. The apparatus may further comprise surface equipment comprising the controller.

The PLT may be further operable to measure pressure and temperature of the production fluid flow at each of the zone-associated depths, and the controller may be further operable to determine a compression factor of the production fluid flow at each of the zone-associated depths based on the pressure and temperature of the production fluid flow measured at each of the zone-associated depths. The controller may be operable to determine the flow rate of each compositional component of the zonal fluid flow from each of the zones based further on: the pressure and temperature of the production fluid flow measured at each of the zone-associated depths; and the determined compression factor of the production fluid at each of the zone-associated depths.

The sensor may be operable to measure volumetric proportions of the compositional components of the production fluid flow at each of the zone-associated depths.

The sensor may be operable to measure mass proportions of the compositional components of the production fluid flow at each of the zone-associated depths.

The sensor may comprise a spectrometer, such as a Raman spectrometer.