2A0830 PLS Ltd Flow From Temperature in Production Logging

8/2/2019 2A0830 PLS Ltd Flow From Temperature in Production Logging

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FlowfromTemperature

Presented at Devex Conference May09.

AbstractFlow From Temperature (FFT) is a new module of PLWin software from PLS Production Log

Software UG (www.DBPLS.com) which is used in our consultancy service to interpret difficult PLT

logs. It interprets temperature curves recorded across the pay zone of oil wells, either on its own orin combination with other Production Log (PLT) data to yield the flow profile of the reservoirintervals.

Modern permanent down hole continuous recorders may only provide temperature curves and a

single pressure. Cable run PLT logs measure 3 phase flows using 3 sensors: a spinner and two fluididentifiers, which are prone to failure. The temperature can be substituted for one or more missingdevices.

In single phase flows and theoretically in some two-phase flows the temperature curve alone isenough to yield the flow profile and formation pressure.

FFT uses all features that influence the temperature curve:1) Geothermal gradient2) Depletion cooling3) Friction heating or gas cooling due to drawdown.4) Mass enthalpy: the impact of an entry on the total flow.5) Conduction heat losses, rising cooling and friction heat and water rollback. These influence

the curvature of the temperature log.

1.Introduction

Measuring flow of three components requires three sensors to solve the unknowns. In single or two phase wells the temperature can provide a continuous flow profile with depth. There are threeaccurate features on the temperature curve that can be used.

The first is steps caused by entries of different temperature due to their depth and the geothermal

gradient. This is known as the mass enthalpy (heat) method and is suitable for all but horizontalwells: it works better the greater the vertical spacing between productive intervals. The basic

equation is

Qbelow Tbelow +Qentry Tentry = Qabove Tabove

In the past this equation has been used for oil water mixes: it worked because oil and water oftenundergo similar friction heat and have fairly similar specific heat. Variations in entry temperatures

were hand calculated from zone pressure derived from shut in logs.

The second is the temperature loss due to conduction (Ramey, 1962) and is suitable for wells withlong unproductive intervals or low flows and is improved by larger casings and light fluids (gas).

Third is the entry temperature which is sensitive to and can yield formation pressure. With wide

variations in Zone pressure, zone pressure must be solved to resolve flow.

With these three measurements there is the potential to solve for two phase flow and formation zone

pressure.


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Unfortunately there are two additional unknowns, fallback and geothermal position, which may haveto be solved from the temperature log alone.

Measuring flow is difficult in large diameter bores in two phases when the heavy phase falls back,

and the spinner sits in an unrepresentative part of the flow. For example in oil and water mixtures itis common to have an error in spinner fluid velocity of +/-5 m/min; this error is multiplied by five in

gas water. In oil water mixes in 6 internal diameter directional bores the error is around +/-100m3/day (600 barrels/day) for a correctly centralised tool.

Even in single phase wells, there is often a static water column through which hydrocarbon flows.The induced error is often greater than the flow. The spinner is therefore the instrument commonly

requiring a substitute.

The PLT interpretation in two-phase for example is the solution of two linear simultaneous equationssuch as:

Qoil = Eoil (Qtotal + A Vslip (1 - Eoil)) .1. the hold up equation

Qtotal = Vspinner A the spinner equation

Mass Enthalpy Equation

Either equation can be replaced by the linear multiphase equation mass enthalpy equation 2:

(Qbelow Cp) fluid Tbelow +(Qentry Cp Tentry ) fluid =(Qabove Cp) fluid Tabove +losses

The losses are the sum of thermal expansion due to pressure loss rising in the hole, conduction to thebore hole wall and friction heat generated by the slipping fluids. Losses are significant when entries

are small and spread over a wide interval.

This equation works provided circulating fluids (fallback) has not displaced, (smeared) thetemperature steps to non- productive interzones. A similar effect is caused by the tool mass and

motion itself.

The equation 2 requires the entry temperatures of each fluid, Tentry, to be pre-calculated. Eachdepends on the rock temperature, depletion and drawdown. Geothermal gradients vary with rock

type and need actual measurements. Pressure depletion causes the whole reservoir to cool due to(isentropic) expansion in the pore space, depending on saturations, porosity, depletion, and each

fluids Ic (Ic cooling coefficient C/bar) and specific heat Cp. Depletion cooling will diffuseperpendicular to the reservoir and so diminish and spread according to the field age. We term this

distorted geothermal the depletion temperature (Tdeplet_FM on the plot). In wells with pressure supportit does not occur, and in thin beds, low porosity and light gas may be insignificant. Each fluid then

undergoes frictional expansion (Joule Thomson = isenthalpic) into the wellbore, so water, oil andhigh pressure gas go through friction heating and low pressure gas Joule Thomson cooling. The

original reservoir pressure, temperature gradient, current zonal reservoir pressure(s) and wellborepressure must be known to calculate the Tentry for each fluid.

The mass enthalpy method requires the flow to surface to be known, so cannot be used for

crossflows, unless one crossflow is identified from the curvature method.

Slope and Curvature

Fluid rising between zones undergoes losses: whilst this is interference for mass enthalpy methods, it

provides additional measurements of flow. Losses are from conduction, expansion cooling


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(isentropic) and friction heating. For example oil rising by itself exhibits isentropic cooling, whileoil percolating slowly through water will undergo isentropic and friction heating (which together

sum to the isenthalpic loss). A two-phase production partly undergoes isentropic and partlyfrictional rising. Given a high rate, or in a place where the slope coincides with bore hole wall

temperature, the cooling slope is solely dependent on the fluid types and is a fluid identifier. Whenrates are low the conduction loss to the bore hole wall is the main loss and the slope gives the flow

rate and cumulatively a curvature. If the wall temperature (Tplateau) is known, a single phase flow ratecan be derived from the differential equation:

dT/dD = (T - Tplateau) Cl / (Q Cp) ( Ramey, 1962)

In short intervals where the Tplateau is known the slope can give the flow rate.If the interval is long enough, the temperature becomes a curve: the upflow curvature gives the rate

and the slope at the wall temperature gives the fluid flow rates. If the fluid rates are already known,the curve shape will show the wall temperature. If the curve is long enough the flow rate and wall

temperature can both be derived. A lot of information can be obtained if the flow is only upwards,but when a heavy fluid causes fallback a downflow curvature interferes with the upflow one.

Bore Hole Wall TemperatureEstimating the bore hole wall temperature is challenging. Strictly speaking, the bore hole wall has aradial temperature gradient across it forced by the current flow, the casing having the fluid

temperature, the distant rock being at depletion temperature. If the flow stops, a quasi steady plateauof equal temperature forms, getting steadier and wider diameter with time according to the

diffusivity (diffusivity = conductivity/Cprock). The plateau is due to the collapsing effect of all formertemperature radial diffusions. The plateau only really exists if there is or was a period of no fluid

movement (no forcing), so it only is seen by the log in a period of no flow. If there was a period ofno flow, a short plateau may exist away from the well bore, but will not be seen by the temperaturelog.

The plateau may therefore only be seen in the cap rock (monoflow, or if there is no fluid exchange tothe tubing) or in a perfectly static shut in well, which is rare. It is not steady, but declinescontinually at an ever decreasing rate following the diffusivity equation, never quite returning to the

geothermal. In the case where a new flow regime takes over, such as a shut in, the new temperaturegradient is superimposed on the Tplateau of the former flow(s).

The plateau temperature is estimated by FFT by imposing the effects of all former wellbore

diffusions upon depletion. In practice, only brief events that occurred recently and long term (usuallyproduction) temperatures which occurred some time ago need be considered.

Conduction loss therefore changes as the plateau decays. It is of course highest, a surge, when a new

temperature different from the old one is applied by a new flow, such as a shut in crossflow. This iswhy small shut in crossflows are more easily identified from the curvature.

How FFT solves the Flow equations

Consider a two phase well : 2 PLT measurements, spinner and fluid identifier, will have beenattempted. Curvature is the product of 3 equations and 4 unknowns. FFT simulates a temperature

curve to match T by trial and error adjustments of whatever is missing from the measurements, plusthe fallback and the geothermal. In the best low rate circumstances the curve shape is almost only

driven by flow convection power Hnet, the geothermal, and the fallback: the 4th

unknown, (fluidmix) effect is negligible so arbitrary mix (holdup) could be entered. The curvature will therefore

solve for convection, geotherm and fallback. It can solve for the fluid flow ratios when a real fluididentifier must is entered. (In high flow rates only the slope will be seen, a product only of the fluid

mix and their expansion cooling: curvature simulation will solve only for fluid mix.) By removing


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the fallback effect it derives a convection upwards only curve Tsimple so that the entry steps are inthe correct depth of the entry. The geothermal and Tsimple are taken for use in the mass enthalpy

analysis which solves the simultaneous equations: mass enthalpy 1, hold up equation 2 (and a thirdhold up equation if there are 3 fluids) to give the fluid flows. Zone pressure needs adjusting until the

Hnet matches the curvature result of Hnet, thus solving for zone pressure.

Its a little confusing because of the options. Let us restate the situation:There are are 5 unknowns Oil Flow, Water flow, Zone pressure, Geothermal and Fallback.

There are 3 equations in curvature , the mass enthalpy (2) and the hold up equation (1): total 5There are 5 inputs. Zone Temperature value, Step, Curve up, Curve down, and Position.

These all come from the temperature log.The 5 unknowns can be solved.

If any inputs are weak, a fluid identifier is needed.The hold up equation is usable in the curvature, and/or with the mass enthalpy equations set.

In principle for every useable input there can be an output. But two of the outputs, geothermal and

fallback, are requirements of the calculation, not initial objectives.

If curvature is not visible for example, the geotherm must be estimated somehow else. The massenthalpy equation 2 and the hold up equation must be solved with input from temperature steps and

a fluid identifier. Zone pressure will not be solved, and must be estimated from other informationsuch as shut in logs.

Most of our experience comes from cable logs with missing spinner, such as the example below.

FFT has nevertheless been built with the capability to solve more complex situations which themathematics appears capable of.

Example:

In the example below, a flow of gas, there are 2 desirable unknowns:

zone pressure, gas flow.The curve simulation matching solves for flow, geothermal position, and fallback which removes thesmear from the step.

The geothermal position , Tsimple curve with restored step, and flow are taken to the mass enthalpyequation which solves for pressure.

The mass enthalpy equation is arranged in FFT to give flow results. It is used to solve for pressureby an trial and error process in which pressures are adjusted until flows by the two methods are the

same.

In a two phase well:The curve matching solves the total flow heat convection Hnet. Add a zone pressure, say from a

shut in log so the mass enthalpy equation in combination with the hold up equation 1 solves for 2fluid flows. Here iterative guesses of the hold ups would be made until the mass enthalpy equation

gives the same Hnet.Alernatively if a fluid identifier gives the fluid hold up, the curve matching gives the flow of 2

fluids, and the geothermal position. The mass enthalpy equation is then available for zone pressure.

The software PVT prediction provides the two relationsTeoil = f (G, Pz, ) ( Pz controls depletion and friction heating)

Tew = f ( G, Pz).The history/former temperature provides the relation between Tplateau identified from the curve

match, and Tdeplet_FM required by the mass enthalpy.


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If a full character curvature is not available, its likely G might be uncertain. Then a fluid identifierwould be required.

Going Through the FFT ModuleI dont want to go through all the formulae, but will conduct you through an analysis outlining the

FFT special steps as if you were used to PLT analysis. I assume the user has knowledge of PLT loganalysis and has already set up a well, zones and predicted PVT properties.

T refers to the temperature curve being analysed TEMPP1R1.P1 refers to producing state 1

R1 refers to run 1, the first PLT log in the well.

Formation InputsEnter a porosity, water saturation and oil saturation curve, or values estimated for the zone, internal

diameter deviation and TVD.

Default formation specific heat of rock and fluid Cv are offered (by FFT). The module will calculatethe Cp values from PVT properties and pressures. Rock conductivity is offered.

Enter the original reservoir pressures. Enter a curve containing current reservoir pressures for shut

in pressure or if not known, the wellbore shut in pressure curve, or a fixed value.


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Logging HistoryEnter the field life: used with the porosity, saturation and pressure depletion to calculate the

depletion cooling Tdeplet_FM allowing for vertical diffusion.

Enter the well age, the curve name associated with the regular flow (usually the same as loggedflowing).

Enter the time shut in, the time logged in the shut in state and the name of the shut in temp curve.Enter the time the flow was started stabilising for logging and the time of logging.

The module will create the Tdeplet_FM, Tplateau relevant to the flowing state based on the depletion,vertical diffusion, radial diffusion, decay of the radial temperature from the regular flow and the 12hrs of shut in. It also shows the conduction loss in watts/meter of hole per C temperature

difference.

Physical InputsMass of tool & cable speed, these are used in estimation of smear effects. Smear of the true

temperature in the well by the already present fallback is increased by the tool.

Enter fluid identifiers: The temperature curve to be analysed, and the pressure, used for drawdownhence for Joule Thomson heating/cooling.

Slippage


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Slip velocity is crucial in low flow rates. The software predicts flow slip (V slip) for each fluid fromhold up and velocity. One is allowed to change these with a multiplying factor. In certain situations,

commonly above the pay, it is obvious if the slip predicted is incorrect. The slip in turn is used topredict the rollback velocity for single and 2 phase .

Interzones

Select intervals where there are no entries between one producing zone and the next.The program averages fluid hold ups over the interzone and calculates a temperature curve shape

over it.

PVT Thermal PropertiesThe program calculates depletion cooling; it is done in 40 bar steps because PVT parameters change.

Also calculates Joule Thomson cooling and heating for oil, gassy oil if present, gas and water for usein drawdown to give entry temperatures and for the bore hole to give slip heating and isentropic

(rising) cooling.

Geothermal, Tdeplet-FM and Tplateau and simulations

.

The user makes critical skilful choices to position the geothermal. The curvature locates Tplateau , thehistory relate it to Tdeplet_FM and the geothermal. It is the last input for Tdeplet_FM and. Ideally the

field would have been logged in the virgin state months after drilling, before perforating to provide ageothermal across the pay: rarely is this available. Anchor the geothermal slope in the sump 40m

below the base zone to allow for tool differences: this should be within 0.1 deg of the geothermal, as

in the example. If no sump, anchor in the caprock using Tplateau or using another curved interzone.


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After production, the geothermal never is seen again, but its position can be inferreda) from T which may cross the Tplateau at the slope given by the rising cooling (almost vertical).

This may occur in shut in logs or gas producers. The rising cooling is the sum of slip heat andisentropic cooling. The program allows you to see what this angle is by computing gold

curves simulating slip heat & expansion loss rising this tells where the Tplateau is. If nocrossing, it can still be located: the curve simulation will not be correct till Tplateau is located.

It is easier with no fallback. The geotherm is adjusted adjust the curves match. Withfallback, its less reliable of course, but the curve shape will not match until the geothermal is

correctly placed. Strong fallback or flow make location less reliable.b) From shut in cap rock temperatures. If there is no tubing runback, or runback is long time

complete, T shut in will overlay Tplateau. Obviously more likely in monophasic wells.c) From the asymptote of T. In long wells or low flow rates T asymptotes (straightens) onto a

slope path Z meters above the TplateauIn a well without fallback, Z is Rameys depth constant Z= (Q Cp / Cl. = Hnet/Cl. Rarely will this

be seen as loggers rarely log far above the top, and it requires the distance 3Z to stabilise.

For a well flowing 10 m3/d of oil, Z is 10 800 2700 / 3 / (60 60 24) = 83 meters

In the example Tempp1r1 crosses Tplateau at the angle of Texploss (Tsliploss heat being vertical, ornegligible). This is a gas well with gas cooling 20 C at the base zone showing this to be the highestpressured. Zone 2 is lowest pressured.

Mass Enthalpy

The FFT program computes flows starting at the top. This can be run first, but if curvaturesimulation is possible, it should be done first.

The result shows the flow QTTEPP1R1. It is computed continuously. It makes minor mistakes above

zone 1 and at the base of zone 1 interprets the fall back curvature as flow, and assigns a negativeentry due to a change in water hold up. It is the result of a small error in slip and the top of a staticwater column. The fall back error is removed by the interzone simulation, and the slip error has

been left for demonstration deliberately: a small trimming of the slip velocity will remove it andrefine our slip prediction. The curvatures between zone 1, 2 and 3 are due to small errors in

conduction loss which have been attributed incorrectly to flow. It is a long shot to get the flow 300 mbelow the starting point.

The improved calculation QTTE2 does not allow entries interzonally. The zonal pressures aretrimmed until the result matches the gas flow from the curvature.

If there were insufficient accuracy in some interzones to solve the curvature, and the mass enthalpyresult is suspect, as tends to happen further down multizone wells, the result from curvature may be

imposed and the mass enthalpy calculation calculates results for zones below. This is the method forshut in logs.

Depletion Cooling

Depletion cooling is observable in shut in wells only when there is no crossflow. Otherwise, as in alltemperature work, convection dominates. As most wells have more than one productive zone this is

rare. It can be seen in un-perforated sumps and wells which have only one effective zone, and usedto give formation pressures. In most wells it is just another factor that has to be allowed for.


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Interzone Simulation: Curvature.

Likely use the default heat exchange, temperature at top, at base of curve total flow.Edit the total flow and rollback multiplier and geothermal slope match the curve shape Tsimfb to T.

The purposes of interzone simulation are to extract the maximum information from the T curvature.The curve has two curvatures, position, and starting points. The upward curve is a measure of the

flow rate (actually the convection heat transfer Q Cp) , the downward one (below the top

entry) the fall back (though perhaps influenced by the tool), and its position reveals the position of

Tplateau, ( the Tplateau crossover if there is one makes it clear, if not the curve will not match) hence the

geotherm. The starting points reveal the zone pressures. If you already know for example thegeotherm, you may use the information to confirm water cut, otherwise the position is required tolocate the geotherm. In this example, a monophase gas producer, we used the starting points to give

the formation pressures. This is done by forcing the mass enthalpy method to give the flow rates ofthe simulation: we alter the zonal pressures, the gas entry temperature changes and the entries at

zone 1 and 2 change. The position of the geotherm was checked by the T curve position, but wasalso given by the caprock temperature.

The relation between flow, end temperatures and curvature and position are well predicted by the

software, but the relationship with fall back is not well catalogued. It is hoped with experience theuser will get to know it.

About fallback:


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Fallback occurs when up velocities are too slow to prevent heavy fluid (eg water) falling back. Itsdriven by bubble slip, (vertical segregation) where water falls to the low side of an inclined bore and

drags oil and water down the inclined slope ( a factor which also increases net slip V slip). From flowloop experiments in 8.5 id its been seen to be 2 times predicted slip, but likely varies with casing

size. Its quite crippling to a spinner, but less so to temperature as it is the convection down whichcounts, not the flow, & convection is reduced by the heat exchange Ce (watts/m) across the pipe, so

that the depth constant of the fallback curvature is related to Qfb Cp / Ce.

The software by default sets fallback velocity to 2 .Vslip in 4 internal diameter, so if you see

downward curvature you know upward velocities are less than 2 Vslip, and this effectively puts alimit on flow.

Whether fallback is regarded as an asset to define flow, or just an interference that has to be allowed

for, it is best to remove it from the T curve. It is a smear downwards, a rounding or smoothing ofsharp temperature steps at entries, and like tool smear effect needs removing before the flow profile

is calculated.

In the interzone calculation, let us suppose the geotherm still needs locating, you may thus enter one

or two unknown parameters (usually the flow, perhaps also the hold up) and compute a Tsim_FB. Asimulated curve Tsim_FB will appear which you adjust parameters and geothermal to get the bestmatch. When obtained calculate another curve Tsimple, which has no fallback. Do this in all

interzones. Tsimple is then imposed into the curve T: effectively the smeared entries are put wherethey belong, back in the productive zones.

The curve QTTE2 is then computed using the mass enthalpy method. The mass enthalpy method

should give flow in interzones as entered for the simulation. You must then choose which is morereliable.

For high rate wells or short interzones, the interzone simulation will only serve to show the lower

limit of flow.

Shut in Logs


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Shut in logs in this well (Temps1r1) were defective and required excessive editing so are notanalysed. The Temps1r1 has been used to derive the Tplateau where its impact is small, for illustration.

The temperature of the shut-in zone 1 has risen due to the reduced drawdown. Temps1r1 curvestowards Tplateaus.

Tplateaus overlays Temps1r1 in the caprock above zone 1, and there is no rollback because there is no

water in the crossflow.

You can see that approximately:

Tplateau = .3 TdepletF_M + .6 Tempp1r1 (regular flow for 8yrs) + .1 Temps1r1

Tplateaus = .3 TdepletF_M + .7 Tempp1r1 (regular flow)

.5 .4 & .1 are the weighting factors applied by the software. This illustrates the temperature in an 8year old well recovers 30% to the original in 12 hrs

Its likely in shut in wells there will be crossflows in both directions. Both will require at least one

curvature analysis to establish a starting point for the mass enthalpy method.


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Friction Heat Uses

Friction heat calculation was used to derive zone pressures. The analysis above was useful, as in this

example only a single rate log was recorded. What we did above for zone 2 & 3 was complicatedand relies on the fact the simulation is independent of pressure while the mass enthalpy profile relies

on pressure. It works better for strong entries as zone 1 because the flow past is obviously smallerthan the Zone1 contribution, and you could estimate the pressure with knowledge of Kjt gas at 1250

psi. For higher drawdowns the software sums the range of Kjt s involved in the pressure drop. Thezone 3 calculation is the most accurate because there is no flow past and the temperature seen is that

of the entry.

Limitations

The example shown is low flow rate gas only. It would be more difficult to get answers in a similar 2

phase flow because of additional uncertainties in slip. Some additional judgements would likely berequired.

For example high pressure tight zones such as zone 2 & 3 being relatively undepleted, would likelynot contribute water.

In higher flow rates slip uncertainties are less important.

Some equations are not linear, so there may be more than one solution, and up to user judgement tochoose likely solutions.

Its obvious that in single fluid the mass enthalpy cannot resolve flow if the Tentry coincides with T.

This can only happen in a producing well in gas when the flow may be colder than the geothermal.Likewise in two fluids, if the entry mix temperature coincides with T and the entry mix fluid ratio

coincides with well hold up, the flow is unresolved. Similarly if dTentrymix/dP is zero ( the entry mixtemperature does not change with zone pressure), the pressure cannot be resolved: this last situation

can arise in theory with methane around 500bar and with gas liquid mixes.

Its unlikely curvature and step methods will be available for every interzone.

Indeed in high productivity wells fluid enters with negligible friction heating, there is usually nointerzone with curvature. This zone pressure cannot be solved, but the mass enthalpy works well

based on geothermally different entry temperatures, effectively replacing one missing sensor.

In highly productive fields updip (or perhaps even downdip) flow tends to affect crestal wells

causing a rise in temperature difficult to predict.

Symbols Used

A pipe areaCv Specific heat at constant volume joules/kilo

Cp Specific heat constant pressure : joules/kilo, can be calculated from Cv and PVTCe Heat exchange between down flowing and up flowing fluid, watts/m

Cl Conduction Loss: Overall Heat exchange coeff between bore fluid and Rock (Tplateau).Reduces with time as the depth of influence gets radially deeper.

D DepthEoil Hold up of oil in borehole, fraction

dT/dD temperature gradientG Geothermal temperature.

Hnet the net convective heat due to flow, watts/ CIc Isentropic Cooling due to expansion: fluid expanding (no choke) does work on the

surrounding pressure and for HP gas its own nuclear bonding. Causes cooling

greater than isenthalpic. C /bar


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Kjt joule Thomson coefficient for isenthalpic (choked) expansion, C /bar. Gas looseningnuclear forces cools; liquids heats; atmospheric air stays the same.

Pz pressure in a productive zone.Q flow m3/s The equations are easiest stated in SI (MKS) units

Qtotal Flow in the wellbore, m3/secQoil Oil Flow in the well boreQentry Flow entering from the formationQfb Fall back fluid rate m3/sec on low side of hole.

T Recorded temperature being analysed such as TEMPP1R1Tplateau Temperature of rock in region around borehole due to forerunning temperatures

Tplateaus Temp of rock in region around borehole, shut in, due to forerunning temperaturesTdeplet_FM Temperature of rock at far distance from borehole due to geothermal depletion.

Tbelow, Tabove Temperature of fluid in adjacent intervals below and above each other.Above is the interval in which flows are known: mass enthalpy works from top to bottom

Below is the interval where flows to be calculated. Interval is the log step, commonly 1ft, 0.1meter

Tentry, Teoil Tew Temperature of fluid entering from formationTsim_FB Simulated Temperature with all components including fallback

Tsimple Simulated temperature with all components , but without fallbackTexploss Showing temperature slope due to expansion loss rising of rising fluid mix

T slip heat Showing effect of slip heat only.Vslip Slip velocity

Vspinner Fluid velocity from spinnerTslipheat A curve generated to show the effect of slip heat.Texploss A curve generated to show the effect of isentropic cooling with rising flow.Z depth constant, meters. The steady rising slope (seen in low flow rates in long logs) is Z

meters above the geothermal, with a small correction for rising cooling. An importantvalue to interpret flows. Temperature disturbances due to entries T off the steady

rising slope :

start decaying with slope T/Z,curve towards it with exponential decay e

-D/Z,

remain .63T after distance Z and .87 after 2Z.

QTTEPP1R1 Flow computed from temperature.

TEMPP1R1 Temperature recorded during 1st

flow state P1, Run 1 (1st

PLT)TEMPS1R1 Temp in the shut in state.

DENDP1R1 Density of borehole mix.PRESP1R1 bore hole pressure.

fluid density

sum

2.AcknowledgementsAD Hill: Monograph Vol. 14 SPE Henry L Doherty Series.

Ramey HJ Jr: Wellbore Heat Transmission: Journal of Petroleum Technology April62Dieter Bartsch, website www.DBPLS.com for advice on Production Log Interpretation

Michael Morgan ([email protected]), programmer and contractor to PLS.

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2A0830 PLS Ltd Flow From Temperature in Production Logging

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