CN103775058A - Shaft heat loss determining method - Google Patents

Abstract

The invention provides a shaft heat loss determining method. The shaft heat loss determining method comprises the steps that calculating parameters are read in; thermal resistance values at all positions in the radius directions in a shaft and a radial upper heat loss limit value of a shaft unit are calculated; a radial initial heat loss value of the shaft unit is set; a first current value and a second current value are set; a current total thermal resistance value and a third current value are calculated in a circulatory mode, and the first current value and the second current value are updated until the updated second current value is larger than or equal to the depth of the shaft; the obtained third values are summed, and the result obtained after summation is determined to be the shaft heat loss value. By the adoption of the shaft heat loss determining method, heat loss calculation is conducted on the shaft in a sectional mode, so that the shaft heat loss result worked out is more accurate.

Description

A kind of definite method of wellbore heat loss

Technical field

The present invention relates to steam injection oil recovery field, relate in particular to a kind of definite method of wellbore heat loss.

Background technology

In oil exploitation technology, directly from oil well, exploiting out unprocessed oil is crude oil, and the Crude viscosity of different cultivars is generally different.Wherein, viscous crude refers to asphalitine and the crude oil that gum level is higher, viscosity is larger.Practice shows, the viscosity of viscous crude generally can be along with significant change occurs in the variation of temperature.Along with the rising of temperature, the viscosity of viscous crude generally can reduce, so exploitation, conveying to super viscous crude generally need to utilize heating power means to reduce the viscosity of super viscous crude, for example, adopts exploitation via steam injection technology to surpass the exploitation of viscous crude.At present, the major way of thickened oil recovery is exploitation via steam injection, comprises two kinds of modes of steam soak and steam flooding, utilizes the wet saturated steam heat injecting to heat oil reservoir, reduces Viscosity of Heavy Crude Oil, with blowing and mechanical lift mode by heavy oil transportation to ground.

The shaft structure cross-section structure that steam injection is recovered the oil as shown in Figure 1, after steam injection in pit shaft, owing to there is heat conduction in pit shaft between tubing wall, casing wall and cement sheath, there is thermal convection current and heat radiation in annular space layer, make the heat in pit shaft radially flow to stratum, thereby produce heat waste.

In steam injection oil recovery process, what in pit shaft, the size of heat waste was directly determining to inject wellbore bottom is steam or saturation water, thereby is determining the quality of heating effect.Liaohe Oil Field is as domestic main viscous crude production base, and steam injection system energy consumption accounts for viscous crude and produces 80% of total energy consumption, and wherein, the heat waste energy consumption of the steam injection pipelines such as pit shaft accounts for viscous crude and produces 26.36% of total energy consumption.Therefore, calculate wellbore heat loss and have very important significance, based on the wellbore heat loss calculating, can propose to reduce the measure of heat waste, thereby improve the heating effect that steam injection is recovered the oil.

In the computational methods of wellbore heat loss, the computational methods of prior art are: first set an overall coefficient of heat transfer, calculate the parameters such as oil pipe temperature, bushing temperature according to this overall coefficient of heat transfer, revise overall coefficient of heat transfer according to the above-mentioned parameter such as oil pipe temperature, bushing temperature calculating again, constantly carry out iteration, when the overall coefficient of heat transfer obtaining when twice adjacent calculation approaches, iteration finishes, and the overall coefficient of heat transfer calculating is for the last time defined as to the overall coefficient of heat transfer of pit shaft, then calculate the heat waste of pit shaft according to the overall coefficient of heat transfer of above-mentioned definite pit shaft.But, above-mentioned computational methods are done as a whole continuation by the entire depth of pit shaft and are calculated, and do not consider the difference along with mine shaft depth, and in pit shaft, the factor such as vapor (steam) temperature can change, wellbore heat loss correspondingly also can change, and therefore the result of calculation of said method is inaccurate.Meanwhile, these computational methods, after iteration three or four times, there will be isolation layer outside wall temperature to be less than the phenomenon of internal surface of sleeve pipe temperature, and this phenomenon does not meet the natural law, and iteration does not restrain, and cannot proceed iterative computation.

Summary of the invention

The object of this invention is to provide a kind of definite method of wellbore heat loss, accurate to realize the heat waste result of calculation of pit shaft.

A kind of definite method that the invention provides wellbore heat loss, comprising:

S1: read in calculating parameter;

S2: according to thermal resistance value and pit shaft unit radial heat waste higher limit everywhere beyond radial direction annular space part in described calculation of parameter pit shaft;

S3: pit shaft unit radial heat waste initial value is set according to described higher limit;

S4: using described initial value as the first currency; To calculate pithead position and subscribe down step-length position as the second currency to it;

S5: based on thermal resistance value everywhere beyond annular space part in the first currency, the second currency and S2, calculate current total heat resistance;

S6: determine the 3rd currency based on current total heat resistance;

S7: the first currency in S6 is updated to the 3rd currency; The second currency in S6 is increased to predetermined step-length, and the second currency is updated to the value after the predetermined step-length of this increase;

S8: S5～S7 is carried out in circulation, until the second currency after upgrading in S7 is more than or equal to the degree of depth of pit shaft;

S9: to the 3rd currency summation of each execution S6 gained, described summed result is defined as wellbore heat loss.

In described S5, calculate current total heat resistance, specifically comprise:

S51: stratum average temperature, average pressure, the saturated vapour average temperature of calculating the second currency;

S52: calculate the radially temperature at diverse location place of the second currency according to the result of S51;

S53: calculate the second currency annular space free convection heat transfer coefficient and annular space radiation heat transfer coefficient according to the result of S52;

S54: calculate annular space thermal convection current thermal resistance value according to described annular space free convection heat transfer coefficient and annular space radiation heat transfer coefficient;

S55: calculate current total heat resistance according to thermal resistance value everywhere beyond annular space part in described annular space thermal convection current thermal resistance value and S2.

In described S51, calculate stratum average temperature, average pressure, the saturated vapour average temperature of the second currency, specific as follows:

The design formulas of described stratum average temperature is:

T _e=(b _k+b _k-1)/2

In above formula, b _krepresent the formation temperature at its lower k times of step-length place of well head, unit is degree Celsius; b _k-1represent the formation temperature at well head (k-1) times step-length place under it, unit is degree Celsius; b _kdesign formulas be:

b _k=(b _k-1+a1×dl)

In above formula, b _k-1represent the formation temperature at well head (k-1) times step-length place under it, unit is degree Celsius; A1 is geothermal gradient, and unit is degree Celsius/meter; Dl represents predetermined step-length, and unit is rice; Formation temperature initial value b ₀for surface temperature, unit is degree Celsius;

The calculating design formulas of described average pressure is as follows:

$\frac{\mathrm{dp}}{\mathrm{dl}}=-\frac{[{\mathrm{\ρ}}_l{H}_l+{\mathrm{\ρ}}_g(1-H_1)]g\sin \mathrm{\θ}+\frac{\mathrm{\λGv}}{2\mathrm{DA}}}{1-\frac{[{\mathrm{\ρ}}_l{H}_l+{\mathrm{\ρ}}_g(1-H_l)]{\mathrm{vv}}_{\mathrm{sg}}}{p}}$

In above formula, p represents the pressure of mixture, Pascal; Z represents the distance of axial flow, rice; ρ _lrepresent density of liquid phase, kilograms per cubic meter; ρ _grepresent density of gas phase, kilograms per cubic meter; H _lrepresent liquid holdup, cubic meter/cubic meter; G represents acceleration of gravity, rice/square second; θ represents the angle of pipeline and horizontal direction, degree; λ represents the on-way resistance coefficient of two-phase flow, and unit is 1; G represents the mass flow of mixture, Kilograms Per Second; V represents the flow velocity of mixture, meter per second; v _sgrepresent the specific speed of gas phase, meter per second; D represents pipe diameter, rice; A represents that pipeline section is long-pending, square metre;

The computational methods of described saturated vapour average temperature are:

T _s=195.94P ^0.225-17.8

In above formula, Ts represents saturated vapour average temperature, degree Celsius; P represents average pressure, Pascal.

In described S52, calculate the radially temperature at diverse location place of the second currency, comprising:

Tube inner wall temperature T _tifor: T _ti=T _s-R ₁q _k/ dl

Oil-pipe external wall temperature T _tofor: T _to=T _ti-R ₂q _k/ dl

Heat-insulated pipe inner wall temperature T _ifor: T _i=T _to-R ₃q _k/ dl

Heat-insulated pipe outside wall temperature T _ofor: T _o=T _i-R ₄q _k/ dl

The outer temperature T of cement sheath _hfor: T _h=T _e+ R ₈q _k/ dl

Sleeve outer wall temperature T _cofor: T _co=T _h+ R ₇q _k/ dl

Internal surface of sleeve pipe temperature T _cifor: T _ci=T _co+ R ₆q _k/ dl

In above-mentioned formula, the unit of temperature is degree Celsius; R ₁represent the thermal convection current thermal resistance value between steam and tube inner wall, R ₂thermally conductive heat resistance between inwall and the outer wall of expression oil pipe, R ₃represent the thermally conductive heat resistance of isolation layer, R ₄represent the thermally conductive heat resistance of instlated tubular tube wall, R ₆represent the thermally conductive heat resistance of casing wall, R ₇represent the thermally conductive heat resistance of cement sheath, R ₈represent the thermally conductive heat resistance of cement sheath, above-mentioned thermal resistance value is the thermal resistance value that S2 calculates, unit be (rice Kelvin)/watt; The first currency when Qk is the k time circulation execution S5, kilojoule/hour.

In described S53, calculate the second currency annular space free convection heat transfer coefficient and annular space radiation heat transfer coefficient, comprising:

Annular space radiation heat transfer coefficient h _rdesign formulas as follows:

$h_r=\mathrm{\δ}{F}_{\mathrm{tci}}(T_o^{*2}+T_{\mathrm{ci}}^{*2})+(T_o^{*}+T_{\mathrm{ci}}^{*})$

Wherein,

$T_o^{*}=T_o+273.15,T_{\mathrm{ci}}^{*}=T_{\mathrm{ci}}+273.15$

In above-mentioned formula: δ is Si Difen-Boltzmann constant, its value is 2.189 × 10 ^-8watt/(rice Kelvin); F _tcifor oil pipe or heat-insulated pipe outer wall surface are to internal surface of sleeve pipe surface emissivity coefficient of efficiency, calculate by following formula:

$\frac{1}{F_{\mathrm{tci}}}=\frac{1}{{\mathrm{\ϵ}}_o}+\frac{r_{\mathrm{to}}}{r_{\mathrm{ci}}}(\frac{1}{{\mathrm{\ϵ}}_{\mathrm{ci}}}-1)$

Wherein, ε _ofor the blackness of heat-insulated pipe outer wall, it is known quantity; ε _cifor the blackness of internal surface of sleeve pipe, it is known quantity;

Annular space free convection heat transfer coefficient h _cdesign formulas as follows:

$h_c=\frac{0.049{\left(G_r{P}_r\right)}^{0.33}{P}_r^{0.074}{K}_{\mathrm{ha}}}{r_o\ln \frac{r_{\mathrm{ci}}}{r_o}}$

In above formula, G _rfor Grashof number; P _rfor Prandtl number; G _rand P _rdesign formulas as follows:

$G_r=\frac{{(r_{\mathrm{ci}}-r_o)}^{3}g{\mathrm{\ρ}}_{\mathrm{an}}^2\mathrm{\β}(T_o-T_{\mathrm{ci}})}{U_{\mathrm{an}}^2}$

$P_r=\frac{C_{\mathrm{an}}{U}_{\mathrm{an}}}{K_{\mathrm{ha}}}$

Wherein: K _hafor the coefficient of thermal conductivity of annular fluid, watt/(rice Kelvin); G is acceleration of gravity, rice/square second; ρ _anfor annular fluid is at average temperature T _anunder density, kilograms per cubic meter; U _anfor annular fluid is at average temperature T _anunder viscosity, milli pascal second; Average temperature T _an=(T _s+ T _ci)/2, Kelvin; C _anfor annular fluid is at average temperature T _anunder thermal capacitance, joule/(cubic meter Kelvin).

In described S54, calculate annular space thermal convection current thermal resistance value, calculate according to following formula:

$R_5=\frac{1}{2\mathrm{\π}(h_c+h_r)r_o}$

Wherein, R ₅represent annular space thermal convection current thermal resistance value, (rice Kelvin)/watt; Hr is annular space radiation heat transfer coefficient, watt/(square metre Kelvin); Hc is the naturally right convective heat-transfer coefficient of annular space, watt/(square metre Kelvin); r _ofor heat-insulated pipe exterior radius, rice.

In described S55, calculate current total heat resistance, computational methods are:

R=R ₁+R ₂+R ₃+R ₄+R ₅+R ₆+R ₇+R ₈

In above formula, R represents current total heat resistance, R ₁represent the thermal convection current thermal resistance value between steam and tube inner wall, R ₂thermally conductive heat resistance between inwall and the outer wall of expression oil pipe, R ₃represent the thermally conductive heat resistance of isolation layer, R ₄represent the thermally conductive heat resistance of instlated tubular tube wall, R ₅represent annular space thermal convection current thermal resistance value, R ₆represent the thermally conductive heat resistance of casing wall, R ₇represent the thermally conductive heat resistance of cement sheath, R ₈represent the thermally conductive heat resistance of cement sheath; Unit be (rice Kelvin)/watt.

Described S6 determines the 3rd currency based on current total heat resistance, specifically comprises:

S61: according to the current current heat waste of total heat computing the resistor value;

S62: judge whether described current heat waste is greater than described higher limit; If described current heat waste is less than or equal to described higher limit, using described current heat waste as the 3rd currency; If described current heat waste is greater than described higher limit, using the described initial value in S3 as the 3rd currency.

Described S61 is according to the current current heat waste of total heat computing the resistor value, and computational methods are specially:

$Q_k^{\′}=\frac{T_s-T_h}{R}\mathrm{dl}$

In above formula, Q' _krepresent the current heat waste that the k time circulation calculates while carrying out S61, Ts is steam injection temperature, degree Celsius; Th is the outer temperature of cement sheath, degree Celsius; R represents current total heat resistance, (rice Kelvin)/watt; Dl represents predetermined step-length, rice.

Described pit shaft unit radial heat waste higher limit, calculate and obtain by following formula:

$Q_m=\frac{T_s-T_e}{R_1+R_2+{\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HDA0000451130510000021.png"\; state="\{\{state\}\}">R</figure-callout>}}_3+R_4+R_5+R_6+{\mathrm{<figure-callout\; id="7"\; label="R"\; filenames="HDA0000451130510000021.png"\; state="\{\{state\}\}">R</figure-callout>}}_7+R_8}\mathrm{dl}$

In above formula, R ₁represent the thermal convection current thermal resistance value between steam and tube inner wall, R ₂thermally conductive heat resistance between inwall and the outer wall of expression oil pipe, R ₃represent the thermally conductive heat resistance of isolation layer, R ₄represent the thermally conductive heat resistance of instlated tubular tube wall, R ₅represent annular space thermal convection current thermal resistance value, R ₆represent the thermally conductive heat resistance of casing wall, R ₇represent the thermally conductive heat resistance of cement sheath, R ₈represent the thermally conductive heat resistance of cement sheath, unit be (rice Kelvin)/watt; T _sfor steam injection temperature, T _efor formation temperature, unit is degree Celsius.

The selection range of described predetermined step-length is: 0<dl<h; Dl represents predetermined step-length, rice; H represents the degree of depth of earth's surface with well-sinking, rice.

The value of described pit shaft unit radial heat waste initial value is 0-Q _m, described Q _mit is the pit shaft unit radial heat waste higher limit calculating in S2.

The value of described pit shaft unit radial heat waste initial value is further chosen for 0.9Q _m.

Definite method of the wellbore heat loss that the application provides, has considered heat waste inhomogeneous factor in variant depths in pit shaft, adopts the method for segmentation pit shaft to be carried out to the calculating of heat waste, makes the result of the wellbore heat loss calculating more accurate; Simultaneously, using pit shaft unit radial heat flow heat waste as iteration variable, choose the numerical value that is slightly less than pit shaft unit radial heat flow heat waste higher limit as iteration initial value, also considered pit shaft unit radial heat flow heat waste higher limit pit shaft unit radial heat flow heat waste being carried out to timing, thereby only can avoid in conventional algorithm iteration several times to obtain just stopping after overall coefficient of heat transfer that precision is not high the phenomenon of calculating, make iterative process convergence.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present application or technical scheme of the prior art, to the accompanying drawing of required use in embodiment or description of the Prior Art be briefly described below, apparently, the accompanying drawing the following describes is only some embodiment that record in the application, for those of ordinary skills, do not paying under the prerequisite of creative work, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is the application's pit shaft cross-sectional view;

Fig. 2 is the flow chart that the application's wellbore heat loss is determined method;

Fig. 3 is that the application's wellbore heat loss is determined the flow chart that calculates current total heat resistance in method;

Fig. 4 is that the application's wellbore heat loss is determined the flow chart of determining the 3rd currency in method.

The specific embodiment

In order to make those skilled in the art person understand better the technical scheme in the application, below in conjunction with the accompanying drawing in the embodiment of the present application, technical scheme in the embodiment of the present application is clearly and completely described, obviously, described embodiment is only the application's part embodiment, rather than whole embodiment.Based on the embodiment in the application, those of ordinary skills, not making the every other embodiment obtaining under creative work prerequisite, should belong to the scope of protection of the invention.

Fig. 1 is the cross-sectional view of steam injection oil recovery pit shaft.As shown in Figure 1, be outwards followed successively by inner tube, heat insulation layer, outer tube, annular space layer, sleeve pipe, cement sheath, stratum from wellbore centre position along radial direction.After the steam injection of center, temperature is the highest, and due to the heat transfer process between each layer in pit shaft, wellbore centre position also raises along each layer of outside temperature of radial direction.At the radial direction of pit shaft, successively reduce from wellbore centre to lip temperature.

Fig. 2 is the flow chart that the application's wellbore heat loss is determined method.As shown in Figure 2, method of the present invention comprises:

S1: read in calculating parameter.

In oil recovery process, the parameter relevant to wellbore heat loss mainly comprises three aspects:

The first is the structure of pit shaft and relevant physical-property parameter thereof, for example: tube inner wall radius r _ti; Oil-pipe external wall radius r _to; Casing inner diameter r _ci; Heat-insulated pipe inwall radius r _i; Heat-insulated pipe exterior radius r _o; Sleeve pipe external diameter r _co; Heat insulation layer coefficient of thermal conductivity K _ins; Cement sheath coefficient of thermal conductivity K _cem; Well radius r _h; Deng.

The second is the thermal physical property parameter on stratum, for example: surface temperature T _e; Formation thermal conductivity K _e; Deng.

The third is well head injection parameter, for example: steam injection pressure P _s; Steam injection mass dryness fraction X _i; Steam injection speed M _s; Steam injection time t; Deng.

Read in for example above-mentioned said parameter relevant to wellbore heat loss in this step.

S2: according to thermal resistance value and pit shaft unit radial heat waste higher limit everywhere beyond radial direction annular space part in described calculation of parameter pit shaft.

First this step calculates thermally conductive heat resistance or the thermal convection current thermal resistance of pit shaft each several part.Particularly, because the heat waste of pit shaft is caused by thermal convection current and heat conduction, according to steam injection oil recovery principle, in pit shaft, the thermal resistance value computational methods of various piece are as follows successively:

Thermal convection current thermal resistance R between steam and tube inner wall ₁design formulas be:

$R_1=\frac{1}{2\mathrm{\&pi;}{h}_f{r}_{\mathrm{ti}}}---\left(1\right)$

Wherein, h _ffor moisture film thermal transmittance, watt/(square metre Kelvin), be known quantity; r _tifor tube inner wall radius, rice, is the known quantity measuring.

Thermally conductive heat resistance R between inwall and the outer wall of oil pipe ₂design formulas be:

$R_2=\frac{1}{2\mathrm{\&pi;}{K}_{\mathrm{tub}}}\ln \frac{r_{\mathrm{to}}}{r_{\mathrm{ti}}}---\left(2\right)$

Wherein, K _tubfor oil pipe coefficient of thermal conductivity, watt/(square metre Kelvin), be known quantity; r _tofor oil-pipe external wall radius, rice, is the known quantity measuring.

The thermally conductive heat resistance R of isolation layer ₃design formulas be:

${\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HDA0000451130510000021.png"\; state="\{\{state\}\}">R</figure-callout>}}_3=\frac{1}{2\mathrm{\&pi;}{K}_{\mathrm{ins}}}\ln \frac{r_i}{r_{\mathrm{to}}}---\left(3\right)$

Wherein, K _insfor heat insulation layer coefficient of thermal conductivity, watt/(square metre Kelvin), be known quantity; r _ifor heat-insulated pipe inwall radius, rice, is the known quantity measuring.

The thermally conductive heat resistance R of instlated tubular tube wall ₄design formulas be:

$R_4=\frac{1}{2\mathrm{\&pi;}{K}_{\mathrm{tub}}}\ln \frac{r_o}{r_i}---\left(4\right)$

Wherein, r _ofor heat-insulated pipe exterior radius, rice, is the known quantity measuring.

Annular space thermal convection current thermal resistance R ₅design formulas be:

$R_5=\frac{1}{2\mathrm{\&pi;}(h_c+h_r)r_o}---\left(5\right)$

Wherein, h _rfor annular space radiation heat transfer coefficient, watt/(square metre Kelvin); h _cfor the naturally right convective heat-transfer coefficient of annular space, watt/(square metre Kelvin); Above-mentioned two parameters are unknown quantity.

The thermally conductive heat resistance R of casing wall ₆design formulas be:

$R_6=\frac{1}{2\mathrm{\&pi;}{K}_{\mathrm{cas}}}\ln \frac{r_{\mathrm{co}}}{r_{\mathrm{ci}}}---\left(6\right)$

Wherein, K _casfor sleeve pipe coefficient of thermal conductivity, watt/(square metre Kelvin), be known quantity; r _cifor internal surface of sleeve pipe radius, rice, is the known quantity measuring; r _cofor sleeve outer wall radius, rice, is the known quantity measuring.

The thermally conductive heat resistance R of cement sheath ₇design formulas be:

${\mathrm{<figure-callout\; id="7"\; label="R"\; filenames="HDA0000451130510000021.png"\; state="\{\{state\}\}">R</figure-callout>}}_7=\frac{1}{2\mathrm{\&pi;}{K}_{\mathrm{cem}}}\ln \frac{r_h}{r_{\mathrm{co}}}---\left(7\right)$

Wherein, K _cemfor cement sheath coefficient of thermal conductivity, watt/(square metre Kelvin), be known quantity; r _hfor well radius, rice, is the known quantity measuring.

The thermally conductive heat resistance R of cement sheath ₈design formulas be:

$R_8=\frac{f\left(t\right)}{2\mathrm{\&pi;}{K}_e}---\left(8\right)$

Wherein, K _efor formation thermal conductivity, watt/(square metre Kelvin), be known quantity;

F(t in formula (8)) be time dependent conduction heat transfer function, calculated by following formula:

$f\left(t\right)=\ln \left(\frac{2\sqrt{\mathrm{at}}}{r_h}\right)-0.29---\left(9\right)$

In formula (9), a is the average coefficient of heat transfer in stratum, square metre/day, be known quantity; T represents the steam injection time, day, the actual number of days value during according to work; T _hfor the outer temperature of cement sheath, degree Celsius, be the known quantity measuring.

In above-mentioned formula (1)-(8), only have formula (5) to calculate required parameter annular space radiation heat transfer coefficient h _rwith annular space free convection heat transfer coefficient h _cfor unknown quantity, can not directly calculate R ₅value, all the other all can be by directly calculating the resistance of thermal resistance.

On the radial direction of pit shaft, pit shaft unit radial heat waste in predetermined step-length dl length is made as to Q, unit be kilojoule/hour, according to steam injection recover the oil principle, in wellbore radius direction, each several part Q value meets following formula:

$Q=\frac{T_s-T_{\mathrm{ti}}}{R_1}\mathrm{dl}=\frac{T_{\mathrm{ti}}-T_{\mathrm{to}}}{R_2}\mathrm{dl}=\frac{T_{\mathrm{to}}-T_i}{R_3}\mathrm{dl}=\frac{T_i-T_o}{R_4}\mathrm{dl}=\frac{T_o-T_{\mathrm{ci}}}{R_5}\mathrm{dl}=\frac{T_{\mathrm{ci}}-T_{\mathrm{co}}}{R_6}\mathrm{dl}=\frac{T_{\mathrm{co}}-{\mathrm{<figure-callout\; id="7"\; label="T\; h\; R"\; filenames="HDA0000451130510000021.png"\; state="\{\{state\}\}">T</figure-callout>}}_h}{R_{}}\mathrm{dl}=\frac{T_h-T_e}{R_8}\mathrm{dl}---\left(10\right)$

In formula (10), T _sfor steam injection temperature; T _tifor tube inner wall temperature; T _tofor oil-pipe external wall temperature; T _ifor heat-insulated pipe inner wall temperature; T _ofor heat-insulated pipe outside wall temperature; T _hfor the outer temperature of cement sheath; T _cofor sleeve outer wall temperature; T _cifor internal surface of sleeve pipe temperature; T _efor formation temperature; T _sand T _efor known quantity, all the other are calculative parameter, and unit is degree Celsius; Dl represents predetermined step-length, rice.

Can obtain two formulas below according to formula (10):

T _o=T _s-(R ₁+R ₂+R ₃+R ₄)Q/dl (11)

T _ci=T _e+(R ₆+R ₇+R ₈+R ₈)Q/dl (12)

The heat waste at general well head place is maximum, if annular space layer does not exist heat waste, i.e. R ₅value be 0, the pit shaft unit radial heat waste at well head place is maximum pit shaft unit radial heat waste, can be used as the higher limit of pit shaft unit radial heat waste.Around this principle, utilize formula (11) and formula (12) to calculate well head place pit shaft unit radial heat waste, and set it as the higher limit Q of pit shaft unit radial heat waste _m, design formulas is as follows:

$Q_m=\frac{T_s-T_e}{R_1+R_2+{\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HDA0000451130510000021.png"\; state="\{\{state\}\}">R</figure-callout>}}_3+R_4+R_5+R_6+{\mathrm{<figure-callout\; id="7"\; label="R"\; filenames="HDA0000451130510000021.png"\; state="\{\{state\}\}">R</figure-callout>}}_7+R_8}\mathrm{dl}---\left(13\right)$

S3: pit shaft unit radial heat waste initial value is set according to described higher limit.

The initial value Q of pit shaft unit radial heat waste ₀represent.Because the value of pit shaft unit radial heat waste is necessarily less than higher limit Q _m, the therefore initial value Q of pit shaft unit radial heat waste ₀value be 0～Q _m, experimental experience can be got Q ₀value be 0.9Q _m.Use respectively k and Q _krepresent the pit shaft unit radial heat waste after the k time circulation and the k time iteration.

S4: using described initial value as the first currency; To calculate pithead position and subscribe down step-length position as the second currency to it.

By described Q ₀as the first currency.The position l of well head part ₀represent l ₀=0.Predetermined step-length represents with dl, and the span of dl is: 0<dl<h.Described dl can be taken as 10 meters.To calculate pithead position l ₀subscribe down step-length dl position as the second currency to it.L _krepresent after the k time iteration, calculated pit shaft unit radial heat waste Q _klengthwise position.

S5: based on thermal resistance value everywhere beyond annular space part in the first currency, the second currency and S2, calculate current total heat resistance.

From S2, calculate the required thermal resistance value R of total heat resistance ₁-R ₈in, also need to calculate R ₅, calculate R ₅after, can further calculate entire thermal resistance.Fig. 3 is that the application's wellbore heat loss is determined the flow chart that calculates current total heat resistance in method, and as shown in Figure 3, this step, based on thermal resistance value everywhere beyond annular space part in the first currency, the second currency and S2, is calculated current total heat resistance.Specifically comprise:

S51: stratum average temperature, average pressure, the saturated vapour average temperature of calculating the second currency.

Calculate the temperature of each radial position place in the pit shaft of the second currency, need to first calculate saturated vapour average temperature in the pit shaft of the second currency, the average temperature on stratum and average pressure.

Described the second currency stratum average temperature Te utilizes following formula to calculate:

T _e=(b _k+b _k-1)/2 (14）

In above formula, b _krepresent the formation temperature at its lower k times of step-length place of well head, unit is degree Celsius; , b _k-1represent the formation temperature at well head (k-1) times step-length place under it, unit is degree Celsius; b _kdesign formulas be:

b _k=(b _k-1+a1×dl) （15）

In above formula, b _k-1represent the formation temperature at well head (k-1) times step-length place under it, unit is degree Celsius; A1 is geothermal gradient, and unit is degree Celsius/meter; Dl represents predetermined step-length, and unit is rice; Formation temperature initial value b ₀for surface temperature, unit is degree Celsius;

The design formulas of the second currency stratum average pressure P is as follows:

$\frac{\mathrm{dp}}{\mathrm{dl}}=-\frac{[{\mathrm{\&rho;}}_l{H}_l+{\mathrm{\&rho;}}_g(1-H_1)]g\sin \mathrm{\&theta;}+\frac{\mathrm{\&lambda;Gv}}{2\mathrm{DA}}}{1-\frac{[{\mathrm{\&rho;}}_l{H}_l+{\mathrm{\&rho;}}_g(1-H_l)]{\mathrm{vv}}_{\mathrm{sg}}}{p}}---\left(16\right)$

In formula (16), p represents the pressure (definitely) of mixture, Pascal; Z represents the distance of axial flow, rice; ρ _lrepresent density of liquid phase, kilograms per cubic meter; ρ _grepresent density of gas phase, kilograms per cubic meter; H _lrepresent liquid holdup, cubic meter/cubic meter; G represents acceleration of gravity, rice/square second; θ represents the angle of pipeline and horizontal direction, degree; λ represents the on-way resistance coefficient of two-phase flow, and unit is 1; G represents the mass flow of mixture, Kilograms Per Second; V represents the flow velocity of mixture, meter per second; v _sgrepresent the specific speed of gas phase, meter per second; D represents pipe diameter, rice; A represents that pipeline section is long-pending, square metre.The value of above-mentioned physical quantity is known.

According to above-mentioned average pressure, calculate saturated vapour average temperature Ts in the second currency pit shaft, design formulas is as follows:

T _s=195.94P ^0.225-17.8 （17）

In formula (17), P represents the stratum average pressure of the second currency, Pascal.

S52: calculate the radially temperature at diverse location place of the second currency according to the result of S51.

First the R calculating according to S2 ₁, R ₂, R ₃, R ₄, R ₆, R ₇, R ₈and first currency, calculate the radially temperature at diverse location place of the second currency, the temperature computation method of each position is as follows successively:

Tube inner wall temperature T _tifor: T _ti=T _s-R ₁q _k/ dl (18)

Oil-pipe external wall temperature T _tofor: T _to=T _ti-R ₂q _k/ dl (19)

Heat-insulated pipe inner wall temperature T _ifor: T _i=T _to-R ₃q _k/ dl (20)

Heat-insulated pipe outside wall temperature T _ofor: T _o=T _i-R ₄q _k/ dl (21)

The outer temperature T of cement sheath _hfor: T _h=T _e+ R ₈q _k/ dl (22)

Sleeve outer wall temperature T _cofor: T _co=T _h+ R ₇q _k/ dl (23)

Internal surface of sleeve pipe temperature T _cifor: T _ci=T _co+ R ₆q _k/ dl (24)

In above-mentioned formula (18)-(24), the unit of temperature is degree Celsius; R ₁, R ₂, R ₃, R ₄, R ₆, R ₇, R ₈for the thermal resistance that S2 calculates, unit be (rice Kelvin)/watt; Q _kbe the k time the first currency in circulation.

S53: calculate the second currency annular space free convection heat transfer coefficient and annular space radiation heat transfer coefficient according to the result of S52.

Owing to both having existed thermal convection current also to have heat radiation in annular space layer, therefore, the thermal resistance R of ring dead level ₅time, need first according to heat-insulated pipe outside wall temperature T _owith internal surface of sleeve pipe temperature T _cicalculate annular space free convection heat transfer coefficient h _cwith annular space radiation heat transfer coefficient h _r.

Annular space radiation heat transfer coefficient h _rdesign formulas as follows:

$h_r=\mathrm{\&delta;}{F}_{\mathrm{tci}}(T_o^{*2}+T_{\mathrm{ci}}^{*2})+(T_o^{*}+T_{\mathrm{ci}}^{*})---\left(25\right)$

Wherein,

$T_o^{*}=T_o+273.15,T_{\mathrm{ci}}^{*}=T_{\mathrm{ci}}+273.15---\left(26\right)$

$\frac{1}{F_{\mathrm{tci}}}=\frac{1}{{\mathrm{\&epsiv;}}_o}+\frac{r_{\mathrm{to}}}{r_{\mathrm{ci}}}(\frac{1}{{\mathrm{\&epsiv;}}_{\mathrm{ci}}}-1)---\left(27\right)$

In formula (25): δ is Si Difen-Boltzmann (Stefan-Boltzmann) constant, and its value is 2.189 × 10 ^-8watt/(rice Kelvin); F _tcifor oil pipe or heat-insulated pipe outer wall surface are to internal surface of sleeve pipe surface emissivity coefficient of efficiency, calculate by formula (25); ε _ofor the blackness of heat-insulated pipe outer wall, it is known quantity; ε _cifor the blackness of internal surface of sleeve pipe, it is known quantity.Conventionally, at a certain temperature, the radianting capacity of grey body and the ratio of the radianting capacity of synthermal lower black matrix are defined as to the blackness of object, or the emissivity of object, unit is 1.

Annular space free convection heat transfer coefficient h _cdesign formulas as follows:

$h_c=\frac{0.049{\left(G_r{P}_r\right)}^{0.33}{P}_r^{0.074}{K}_{\mathrm{ha}}}{r_o\ln \frac{r_{\mathrm{ci}}}{r_o}}---\left(28\right)$

In above formula, G _rfor Grashof (Grashof) number; P _rfor Prandtl (Prandtl) number.G _rand P _rdesign formulas as follows:

$G_r=\frac{{(r_{\mathrm{ci}}-r_o)}^{3}g{\mathrm{\&rho;}}_{\mathrm{an}}^2\mathrm{\&beta;}(T_o-T_{\mathrm{ci}})}{U_{\mathrm{an}}^2}---\left(29\right)$

$P_r=\frac{C_{\mathrm{an}}{U}_{\mathrm{an}}}{K_{\mathrm{ha}}}---\left(30\right)$

In formula (28)-(30): K _hafor the coefficient of thermal conductivity of annular fluid, watt/(rice Kelvin); G is acceleration of gravity, rice/square second; ρ _anfor annular fluid is at average temperature T _anunder density, kilograms per cubic meter; U _anfor annular fluid is at average temperature T _anunder viscosity, milli pascal second; Average temperature T _an=(T _s+ T _ci)/2, Kelvin; C _anfor annular fluid is at average temperature T _anunder thermal capacitance, joule/(cubic meter Kelvin); In above-mentioned each parameter, g is known quantity, and other parameters are to be measured or calculates, and is known quantity.

S54: calculate annular space thermal convection current thermal resistance value according to described annular space free convection heat transfer coefficient and annular space radiation heat transfer coefficient.

By the annular space free convection heat transfer coefficient h being calculated by S52 _cwith annular space radiation heat transfer coefficient h _rbring formula (5) into and calculate, can obtain annular space thermal convection current thermal resistance R ₅.

S55: calculate current total heat resistance according to thermal resistance value everywhere beyond annular space part in described annular space thermal convection current thermal resistance value and S2.

The annular space thermal convection current thermal resistance R calculating according to S54 ₅with other part thermal resistances of S2 calculating gained, can calculate the entire thermal resistance R of the pit shaft of the second currency.

Particularly, the design formulas of entire thermal resistance R is:

R=R ₁+R ₂+R ₃+R ₄+R ₅+R ₆+R ₇+R ₈ （31）

S6: determine the 3rd currency based on current total heat resistance.

The total heat resistance of calculating according to formula (31) can be used for determining the pit shaft unit radial heat waste of the second currency, and using the pit shaft unit radial heat waste calculating as the 3rd currency.Fig. 4 is that the application's wellbore heat loss is determined the flow chart of determining the 3rd currency in method, and as shown in Figure 4, this step specifically comprises:

S61: according to the current current heat waste of total heat computing the resistor value.

According to the thermodynamics formula that substantially conducts heat, according to the formula of total heat computing the resistor value heat waste be:

$Q_k^{\&prime;}=\frac{T_s-T_h}{R}\mathrm{dl}---\left(32\right)$

In formula (32), Q' _krepresent the current heat waste calculating, molecular moiety represents total temperature loss, and denominator part represents entire thermal resistance; T _sfor steam injection temperature, degree Celsius; T _hfor the outer temperature of cement sheath, degree Celsius.

S62: judge whether described current heat waste is greater than described higher limit; If described current heat waste is less than or equal to described higher limit, using described current heat waste as the 3rd currency; If described current heat waste is greater than described higher limit, using the described initial value in S3 as the 3rd currency.

This step is used for judging described current heat waste Q' _kwhether be greater than pit shaft unit radial heat waste higher limit Q _mif, described current heat waste Q' _kbe less than or equal to described higher limit Q _m, by described current heat waste Q' _kas the 3rd currency; If described current heat waste Q' _kbe greater than described higher limit, do not meet the natural law, using the described initial value in S3 as the 3rd currency, by Q _mas the 3rd currency.

S7: the first currency in S6 is updated to the 3rd currency; The second currency in S6 is increased to predetermined step-length, and the second currency is updated to the value after the predetermined step-length of this increase.

The first currency in S6 is updated to the 3rd currency, i.e. Q' _kvalue; The second currency in S6 is increased to predetermined step-length dl, i.e. (lk+dl), and the second currency is updated to the value after the predetermined step-length of this increase.

S8: S5～S7 is carried out in circulation, until the second currency after upgrading in S7 is more than or equal to the degree of depth of pit shaft.

S5～S7 is carried out in circulation, cycle calculations can calculate the wellbore heat loss of dl length at every turn, the second currency after upgrading in S7 is while being more than or equal to the degree of depth of pit shaft, so represent that the length of pit shaft all calculated completely, no longer carries out cycle calculations.

S9: to the 3rd currency summation of each execution S6 gained, described summed result is defined as wellbore heat loss.

This step is after loop calculation finishes completely, and the 3rd currency of S6 gained in each execution circulation is sued for peace, and described summed result is defined as to wellbore heat loss.

Definite method of the wellbore heat loss that the application provides, has considered heat waste inhomogeneous factor in variant depths in pit shaft, adopts the method for segmentation pit shaft to be carried out to the calculating of heat waste, makes the result of the wellbore heat loss calculating more accurate; Simultaneously, using pit shaft unit radial heat flow heat waste as iteration variable, choose the numerical value that is slightly less than pit shaft unit radial heat flow heat waste higher limit as iteration initial value, also considered pit shaft unit radial heat flow heat waste higher limit pit shaft unit radial heat flow heat waste being carried out to timing, thereby only can avoid in conventional algorithm iteration several times to obtain just stopping after overall coefficient of heat transfer that precision is not high the phenomenon of calculating, make iterative process convergence.

Although described the present invention by embodiment, those of ordinary skills know, the present invention has many distortion and variation and do not depart from spirit of the present invention, wish that appended claim comprises these distortion and variation and do not depart from spirit of the present invention.

Claims (13)

1. a definite method for wellbore heat loss, is characterized in that, comprising:

S1: read in calculating parameter;

S2: according to thermal resistance value and pit shaft unit radial heat waste higher limit everywhere beyond radial direction annular space part in described calculation of parameter pit shaft;

S3: pit shaft unit radial heat waste initial value is set according to described higher limit;

S4: using described initial value as the first currency; To calculate pithead position and subscribe down step-length position as the second currency to it;

S5: based on thermal resistance value everywhere beyond annular space part in the first currency, the second currency and S2, calculate current total heat resistance;

S6: determine the 3rd currency based on current total heat resistance;

S7: the first currency in S6 is updated to the 3rd currency; The second currency in S6 is increased to predetermined step-length, and the second currency is updated to the value after the predetermined step-length of this increase;

S8: S5～S7 is carried out in circulation, until the second currency after upgrading in S7 is more than or equal to the degree of depth of pit shaft;

S9: to the 3rd currency summation of each execution S6 gained, described summed result is defined as wellbore heat loss.

2. definite method of a kind of wellbore heat loss as claimed in claim 1, is characterized in that, calculates current total heat resistance in described S5, specifically comprises:

S51: stratum average temperature, average pressure, the saturated vapour average temperature of calculating the second currency;

S52: calculate the radially temperature at diverse location place of the second currency according to the result of S51;

S53: calculate the second currency annular space free convection heat transfer coefficient and annular space radiation heat transfer coefficient according to the result of S52;

S54: calculate annular space thermal convection current thermal resistance value according to described annular space free convection heat transfer coefficient and annular space radiation heat transfer coefficient;

S55: calculate current total heat resistance according to thermal resistance value everywhere beyond annular space part in described annular space thermal convection current thermal resistance value and S2.

3. definite method of a kind of wellbore heat loss as claimed in claim 2, is characterized in that, calculates stratum average temperature, average pressure, the saturated vapour average temperature of the second currency in described S51, specific as follows:

The design formulas of described stratum average temperature is:

T _e=(b _k+b _k-1)/2

In above formula, b _krepresent the formation temperature at its lower k times of step-length place of well head, unit is degree Celsius; b _k-1represent the formation temperature at well head (k-1) times step-length place under it, unit is degree Celsius; b _kdesign formulas be:

b _k=(b _k-1+a1×dl)

In above formula, b _k-1represent the formation temperature at well head (k-1) times step-length place under it, unit is degree Celsius; A1 is geothermal gradient, and unit is degree Celsius/meter; Dl represents predetermined step-length, and unit is rice; Formation temperature initial value b ₀for surface temperature, unit is degree Celsius;

The calculating design formulas of described average pressure is as follows:

$\frac{\mathrm{dp}}{\mathrm{dl}}=-\frac{[{\mathrm{\&rho;}}_l{H}_l+{\mathrm{\&rho;}}_g(1-H_1)]g\sin \mathrm{\&theta;}+\frac{\mathrm{\&lambda;Gv}}{2\mathrm{DA}}}{1-\frac{[{\mathrm{\&rho;}}_l{H}_l+{\mathrm{\&rho;}}_g(1-H_l)]{\mathrm{vv}}_{\mathrm{sg}}}{p}}$

In above formula, p represents the pressure of mixture, Pascal; Z represents the distance of axial flow, rice; ρ _lrepresent density of liquid phase, kilograms per cubic meter; ρ _grepresent density of gas phase, kilograms per cubic meter; H _lrepresent liquid holdup, cubic meter/cubic meter; G represents acceleration of gravity, rice/square second; θ represents the angle of pipeline and horizontal direction, degree; λ represents the on-way resistance coefficient of two-phase flow, and unit is 1; G represents the mass flow of mixture, Kilograms Per Second; V represents the flow velocity of mixture, meter per second; v _sgrepresent the specific speed of gas phase, meter per second; D represents pipe diameter, rice; A represents that pipeline section is long-pending, square metre;

The computational methods of described saturated vapour average temperature are:

T _s=195.94P ^0.225-17.8

In above formula, Ts represents saturated vapour average temperature, degree Celsius; P represents average pressure, Pascal.

4. definite method of a kind of wellbore heat loss as claimed in claim 2, is characterized in that, calculates the radially temperature at diverse location place of the second currency in described S52, comprising:

Tube inner wall temperature T _tifor: T _ti=T _s-R ₁q _k/ dl

Oil-pipe external wall temperature T _tofor: T _to=T _ti-R ₂q _k/ dl

Heat-insulated pipe inner wall temperature T _ifor: T _i=T _to-R ₃q _k/ dl

Heat-insulated pipe outside wall temperature T _ofor: T _o=T _i-R ₄q _k/ dl

The outer temperature T of cement sheath _hfor: T _h=T _e+ R ₈q _k/ dl

Sleeve outer wall temperature T _cofor: T _co=T _h+ R ₇q _k/ dl

Internal surface of sleeve pipe temperature T _cifor: T _ci=T _co+ R ₆q _k/ dl

In above-mentioned formula, the unit of temperature is degree Celsius; R ₁represent the thermal convection current thermal resistance value between steam and tube inner wall, R ₂thermally conductive heat resistance between inwall and the outer wall of expression oil pipe, R ₃represent the thermally conductive heat resistance of isolation layer, R ₄represent the thermally conductive heat resistance of instlated tubular tube wall, R ₆represent the thermally conductive heat resistance of casing wall, R ₇represent the thermally conductive heat resistance of cement sheath, R ₈represent the thermally conductive heat resistance of cement sheath, above-mentioned thermal resistance value is the thermal resistance value that S2 calculates, unit be (rice Kelvin)/watt; The first currency when Qk is the k time circulation execution S5, kilojoule/hour.

5. definite method of a kind of wellbore heat loss as claimed in claim 2, is characterized in that, calculates the second currency annular space free convection heat transfer coefficient and annular space radiation heat transfer coefficient in described S53, comprising:

Annular space radiation heat transfer coefficient h _rdesign formulas as follows:

$h_r=\mathrm{\&delta;}{F}_{\mathrm{tci}}(T_o^{*2}+T_{\mathrm{ci}}^{*2})+(T_o^{*}+T_{\mathrm{ci}}^{*})$

Wherein,

$T_o^{*}=T_o+273.15,T_{\mathrm{ci}}^{*}=T_{\mathrm{ci}}+273.15$

In above-mentioned formula: δ is Si Difen-Boltzmann constant, its value is 2.189 × 10 ^-8watt/(rice Kelvin); F _tcifor oil pipe or heat-insulated pipe outer wall surface are to internal surface of sleeve pipe surface emissivity coefficient of efficiency, calculate by following formula:

$\frac{1}{F_{\mathrm{tci}}}=\frac{1}{{\mathrm{\&epsiv;}}_o}+\frac{r_{\mathrm{to}}}{r_{\mathrm{ci}}}(\frac{1}{{\mathrm{\&epsiv;}}_{\mathrm{ci}}}-1)$

Wherein, ε _ofor the blackness of heat-insulated pipe outer wall, it is known quantity; ε _cifor the blackness of internal surface of sleeve pipe, it is known quantity;

Annular space free convection heat transfer coefficient h _cdesign formulas as follows:

$h_c=\frac{0.049{\left(G_r{P}_r\right)}^{0.33}{P}_r^{0.074}{K}_{\mathrm{ha}}}{r_o\ln \frac{r_{\mathrm{ci}}}{r_o}}$

In above formula, G _rfor Grashof number; P _rfor Prandtl number; G _rand P _rdesign formulas as follows:

$G_r=\frac{{(r_{\mathrm{ci}}-r_o)}^{3}g{\mathrm{\&rho;}}_{\mathrm{an}}^2\mathrm{\&beta;}(T_o-T_{\mathrm{ci}})}{U_{\mathrm{an}}^2}$

$P_r=\frac{C_{\mathrm{an}}{U}_{\mathrm{an}}}{K_{\mathrm{ha}}}$

Wherein: K _hafor the coefficient of thermal conductivity of annular fluid, watt/(rice Kelvin); G is acceleration of gravity, rice/square second; ρ _anfor annular fluid is at average temperature T _anunder density, kilograms per cubic meter; U _anfor annular fluid is at average temperature T _anunder viscosity, milli pascal second; Average temperature T _an=(T _s+ T _ci)/2, Kelvin; C _anfor annular fluid is at average temperature T _anunder thermal capacitance, joule/(cubic meter Kelvin).

6. definite method of a kind of wellbore heat loss as claimed in claim 2, is characterized in that, calculates annular space thermal convection current thermal resistance value in described S54, calculates according to following formula:

$R_5=\frac{1}{2\mathrm{\&pi;}(h_c+h_r)r_o}$

Wherein, R ₅represent annular space thermal convection current thermal resistance value, (rice Kelvin)/watt; Hr is annular space radiation heat transfer coefficient, watt/(square metre Kelvin); Hc is the naturally right convective heat-transfer coefficient of annular space, watt/(square metre Kelvin); r _ofor heat-insulated pipe exterior radius, rice.

7. definite method of a kind of wellbore heat loss as claimed in claim 2, is characterized in that, calculates current total heat resistance in described S55, and computational methods are:

R=R ₁+R ₂+R ₃+R ₄+R ₅+R ₆+R ₇+R ₈

In above formula, R represents current total heat resistance, R ₁represent the thermal convection current thermal resistance value between steam and tube inner wall, R ₂thermally conductive heat resistance between inwall and the outer wall of expression oil pipe, R ₃represent the thermally conductive heat resistance of isolation layer, R ₄represent the thermally conductive heat resistance of instlated tubular tube wall, R ₅represent annular space thermal convection current thermal resistance value, R ₆represent the thermally conductive heat resistance of casing wall, R ₇represent the thermally conductive heat resistance of cement sheath, R ₈represent the thermally conductive heat resistance of cement sheath; Unit be (rice Kelvin)/watt.

8. definite method of a kind of wellbore heat loss as claimed in claim 1, is characterized in that, described S6 determines the 3rd currency based on current total heat resistance, specifically comprises:

S61: according to the current current heat waste of total heat computing the resistor value;

S62: judge whether described current heat waste is greater than described higher limit; If described current heat waste is less than or equal to described higher limit, using described current heat waste as the 3rd currency; If described current heat waste is greater than described higher limit, using the described initial value in S3 as the 3rd currency.

9. definite method of a kind of wellbore heat loss as claimed in claim 8, is characterized in that, described S61 is according to the current current heat waste of total heat computing the resistor value, and computational methods are specially:

$Q_k^{\&prime;}=\frac{T_s-T_h}{R}\mathrm{dl}$

In above formula, Q' _krepresent the current heat waste that the k time circulation calculates while carrying out S61, Ts is steam injection temperature, degree Celsius; Th is the outer temperature of cement sheath, degree Celsius; R represents current total heat resistance, (rice Kelvin)/watt; Dl represents predetermined step-length, rice.

10. definite method of a kind of wellbore heat loss as claimed in claim 1, is characterized in that, described pit shaft unit radial heat waste higher limit is calculated and obtained by following formula:

$Q_m=\frac{T_s-T_e}{R_1+R_2+R_3+R_4+R_5+R_6+R_7+R_8}\mathrm{dl}$

In above formula, R ₁represent the thermal convection current thermal resistance value between steam and tube inner wall, R ₂thermally conductive heat resistance between inwall and the outer wall of expression oil pipe, R ₃represent the thermally conductive heat resistance of isolation layer, R ₄represent the thermally conductive heat resistance of instlated tubular tube wall, R ₅represent annular space thermal convection current thermal resistance value, R ₆represent the thermally conductive heat resistance of casing wall, R ₇represent the thermally conductive heat resistance of cement sheath, R ₈represent the thermally conductive heat resistance of cement sheath, unit be (rice Kelvin)/watt; T _sfor steam injection temperature, T _efor formation temperature, unit is degree Celsius.

Definite method of 11. a kind of wellbore heat loss as claimed in claim 1, is characterized in that, the selection range of described predetermined step-length is: 0<dl<h; Dl represents predetermined step-length, rice; H represents the degree of depth of earth's surface with well-sinking, rice.

Definite method of 12. a kind of wellbore heat loss as claimed in claim 1, is characterized in that, the value of described pit shaft unit radial heat waste initial value is 0-Q _m, described Q _mit is the pit shaft unit radial heat waste higher limit calculating in S2.

Definite method of 13. a kind of wellbore heat loss as claimed in claim 12, is characterized in that, the value of described pit shaft unit radial heat waste initial value is further chosen for 0.9Q _m.

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