CN105370255A - Method and device for determining temperature distribution of gas injection and electric ignition shaft of in-situ combustion cage - Google Patents

Abstract

The invention discloses a method and a device for determining temperature distribution of a gas injection electric ignition shaft of an in-situ combustion cage, wherein the method comprises the following steps: step 1, dividing a shaft into a plurality of shaft units dl in the axial direction, and enabling l to be 0 and k to be 1; step 2, calculating the temperature of the oil pipe air after being heated by the electric igniter; step 3, calculating formation thermal resistance, cement sheath thermal resistance, casing wall thermal resistance, thermal resistance between oil casing annulus air and a casing, tubing wall thermal resistance and air thermal resistance in the tubing; the well bore comprises the following components in sequence from inside to outside: the oil pipe is divided into an upper section and a lower section; step 4, calculating the total thermal resistance of the shaft in the radial direction; step 5, calculating the heat loss of the shaft in the radial direction; step 6, calculating the air temperature of the oil pipe; and 7, repeating the steps of 3 to 6 to perform iterative calculation until L is more than or equal to L and the iteration is finished, so as to obtain an oil pipe temperature curve. The calculation is simple, the precision is high, and the iteration times are low.

Description

The defining method of combustion in situ general gas injection electric ignition well bore temperature distribution and device

Technical field

The present invention relates to combustion in situ field, particularly relate to defining method and the device of a kind of combustion in situ general gas injection electric ignition well bore temperature distribution.

Background technology

Current domestic combustion in situ electric ignition technique major part is individual layer baked wheaten cake, and individual layer is lighted a fire general gas injection.Casing programme as shown in Figure 1, comprises from the inside to the outside successively: oil pipe, oil jacket annular space, sleeve pipe, cement sheath, stratum.Have electric igniter in oil pipe, because the calorific value of burning torch is very large, return to not allow as much as possible on annular space heat, the oil pipe at burning torch top (in figure B place) is connected with packer, by oil jacket annular isolation.In FIG, AB section is the cable length of igniter, and the calorific value of cable is smaller comparatively speaking; BC section is the length of burning torch, and the about length of burning torch is 50m.AB section is plain tubing, BC section has three kinds of possibilities: 1. adopt instlated tubular, avoid thermal loss as much as possible, this mode farthest can improve the temperature of exit air, but this tubular column structure couples together cumbersome, because plain tubing is connected with instlated tubular need reducing; 2. adopt screen casing, this mode connects more convenient, but heat waste is maximum; 3. adopt plain tubing, make upper-lower section oil pipe easy to connect, the heat waste of this mode is larger.General gas injection electric ignition can be realized by said structure.

Calculating well bore temperature distribution is realize the electrically-fired key of above-mentioned general gas injection, but, the defining method for the electrically-fired gas injection well well bore temperature distribution of above-mentioned general gas injection is not yet proposed at present.

Summary of the invention

The invention provides defining method and the device of a kind of combustion in situ general gas injection electric ignition well bore temperature distribution, at least to solve the problem not yet having general gas injection ignition process well-sinking thermal field defining method at present.

According to an aspect of the present invention, provide the defining method of a kind of combustion in situ general gas injection electric ignition well bore temperature distribution, comprise: step 1, pit shaft is divided in the axial direction multiple pit shaft unit, the length of each pit shaft unit is dl, makes l=0, k=1, wherein, l represents the length of current calculating, and k represents iterations; Step 2, calculates the temperature T of air after electric igniter heating being injected into oil pipe _s; Step 3, calculates the thermal resistance R on stratum respectively ₁, cement sheath thermal resistance R ₂, thermal resistance R between sleeve pipe inside and outside wall ₃, air in oil jacket annular space and the thermal resistance R between sleeve pipe ₄, thermal resistance R between oil pipe inside and outside wall ₅and the thermal convection current thermal resistance R of oily inner air tube ₆; Wherein, described pit shaft radially comprises from the inside to the outside successively: oil pipe, sleeve pipe and cement sheath, the position corresponding to burning torch top in oil jacket annular space is connected with packer, with described packer for boundary, described oil pipe is divided into epimere oil pipe and hypomere oil pipe, described hypomere oil pipe is instlated tubular, screen casing or plain tubing, and described pit shaft outside is stratum; Step 4, according to R ₁to R ₆calculate pit shaft entire thermal resistance diametrically; Step 5, according to described temperature T _s, described entire thermal resistance and formation temperature, calculate pit shaft heat waste diametrically; Step 6, according to described temperature T _s, described heat waste and described electric igniter power, calculate the air themperature of oil pipe; Step 7, makes l=l+dl, k=k+1, and according to the change of formation temperature, repeat above-mentioned steps 3 to step 6, carry out iterative computation, until l>=L, then iteration terminates, and obtains the temperature distribution history of described oil pipe, and wherein, L represents the total length of oil pipe.

According to another aspect of the present invention, provide the determining device of a kind of combustion in situ general gas injection electric ignition well bore temperature distribution, comprise: division unit, for pit shaft being divided in the axial direction multiple pit shaft unit, the length of each pit shaft unit is dl, makes l=0, k=1, wherein, l represents the length of current calculating, and k represents iterations; First computing unit, for calculating the temperature T of air after electric igniter heating being injected into oil pipe _s; Second computing unit, for calculating the thermal resistance R on stratum respectively ₁, cement sheath thermal resistance R ₂, thermal resistance R between sleeve pipe inside and outside wall ₃, air in oil jacket annular space and the thermal resistance R between sleeve pipe ₄, thermal resistance R between oil pipe inside and outside wall ₅and the thermal convection current thermal resistance R of oily inner air tube ₆; Wherein, described pit shaft radially comprises from the inside to the outside successively: oil pipe, sleeve pipe and cement sheath, the position corresponding to burning torch top in oil jacket annular space is connected with packer, with described packer for boundary, described oil pipe is divided into epimere oil pipe and hypomere oil pipe, described hypomere oil pipe is instlated tubular, screen casing or plain tubing, and described pit shaft outside is stratum; 3rd computing unit, for according to R ₁to R ₆calculate pit shaft entire thermal resistance diametrically; 4th computing unit, for according to described temperature T _s, described entire thermal resistance and formation temperature, calculate pit shaft heat waste diametrically; 5th computing unit, for according to described temperature T _s, described heat waste and described electric igniter power, calculate the air themperature of oil pipe; Iterative computation unit, for making l=l+dl, k=k+1, according to the change of formation temperature, utilize the second computing unit to carry out iterative computation to the 5th computing unit, until l>=L, then iteration terminates, obtain the temperature distribution history of described oil pipe, wherein, L represents the total length of oil pipe.

By defining method and the device of combustion in situ of the present invention general gas injection electric ignition well bore temperature distribution, consider the change of the many factors such as well bore and tubing string structure, the heat transfer of pit shaft radial direction and stratum thermophysical property along well depth, pit shaft is divided into some sections, obtain the physical parameter (thermal resistance, thermal transmittance) of correspondent section, part physical parameter is the function of temperature, adopt solution by iterative method, calculate oil pipe Temperature Distribution.Can in accurate Calculation general gas injection ignition process situation, any flow condition, any time are along the Temperature Distribution of gas injection well pit shaft.Meanwhile, computational process is simple and convenient, and have higher precision, iterations is low, and computational efficiency is high, has extraordinary stability and convergence.According to the Temperature Distribution of pit shaft, the air themperature arriving oil reservoir effectively can be predicted, to adjust gas injection rate and igniter power, and then the smooth enforcement of guarantee point ignition technique.

Accompanying drawing explanation

Accompanying drawing described herein is used to provide a further understanding of the present invention, and form a application's part, schematic description and description of the present invention, for explaining the present invention, does not form limitation of the invention.In the accompanying drawings:

Fig. 1 is the electrically-fired structural representation of the general gas injection of combustion in situ of the embodiment of the present invention;

Fig. 2 is the flow chart of the defining method of the combustion in situ general gas injection electric ignition well bore temperature distribution of the embodiment of the present invention;

Fig. 3 is the structured flowchart of the determining device of the combustion in situ general gas injection electric ignition well bore temperature distribution of the embodiment of the present invention;

The temperature distributing curve diagram of Fig. 4 to be the BC section of the embodiment of the present invention be oil pipe in instlated tubular situation.

Detailed description of the invention

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on embodiments of the invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to protection scope of the present invention.

Embodiments provide the defining method of a kind of combustion in situ general gas injection electric ignition well bore temperature distribution, Fig. 2 is the flow chart of the defining method of the combustion in situ general gas injection electric ignition well bore temperature distribution of the embodiment of the present invention, as shown in Figure 2, the method comprises following step S201 to step S207.

Step S201, is divided into multiple pit shaft unit in the axial direction by pit shaft, the length of each pit shaft unit is dl, makes l=0, k=1, and wherein, l represents the length of current calculating, and k represents iterations.

Step S202, calculates the temperature T of air after electric igniter heating being injected into oil pipe _s.

Step S203, calculates the thermal resistance R on stratum respectively ₁, cement sheath thermal resistance R ₂, thermal resistance R between sleeve pipe inside and outside wall ₃, air in oil jacket annular space and the thermal resistance R between sleeve pipe ₄, thermal resistance R between oil pipe inside and outside wall ₅and the thermal convection current thermal resistance R of oily inner air tube ₆; Wherein, pit shaft radially comprises from the inside to the outside successively: oil pipe, sleeve pipe and cement sheath, the position corresponding to burning torch top in oil jacket annular space is connected with packer, take packer as boundary, oil pipe is divided into epimere oil pipe and hypomere oil pipe, hypomere oil pipe is instlated tubular, screen casing or plain tubing, and pit shaft outside is stratum.

Step S204, according to R ₁to R ₆calculate pit shaft entire thermal resistance diametrically.

Step S205, according to temperature T _s, entire thermal resistance and formation temperature, calculate pit shaft heat waste diametrically.

Step S206, according to temperature T _s, heat waste and electric igniter power, calculate the air themperature of oil pipe.

Step S207, makes l=l+dl, k=k+1, and according to the change of formation temperature, repeat above-mentioned steps S203 to step S206, carry out iterative computation, until l >=L, then iteration terminates, and obtains the temperature distribution history of oil pipe, and wherein, L represents the total length of oil pipe.

Pass through said method, consider the change of the many factors such as well bore and tubing string structure, the heat transfer of pit shaft radial direction and stratum thermophysical property along well depth, pit shaft is divided into some sections, obtain the physical parameter of correspondent section, part physical parameter is the function of temperature, adopt solution by iterative method, calculate oil pipe Temperature Distribution.In the method energy accurate Calculation general gas injection ignition process situation, any flow condition, any time are along the Temperature Distribution of gas injection well pit shaft.Meanwhile, the method is simple and convenient, and have higher precision, iterations is low, and computational efficiency is high, has extraordinary stability and convergence.According to the Temperature Distribution of pit shaft, the air themperature arriving oil reservoir effectively can be predicted, to adjust gas injection rate and igniter power, and then the smooth enforcement of guarantee point ignition technique.

Main assumed condition in the embodiment of the present invention is:

(1) fluid flow state is for stablize one-way flow, and fluid is gas single-phase flow;

(2) in pit shaft, heat transfer is steady state heat conduction;

(3) stratum heat transfer is unsteady heat transfer, and obeys the non dimensional time function of Ramey;

(4) casing programme as shown in Figure 1: oil pipe-oil jacket annular space-sleeve pipe-cement sheath-stratum;

(5) heat waste in pit shaft and surrounding formation is radial, also considers the heat transfer of air flowing along well depth direction simultaneously;

(6) formation temperature linearly changes, known geothermal gradient and surface temperature;

(7) tubing and casing is concentric.

Casing programme as shown in Figure 1, getting well head is the origin of coordinates, is just straight down.

In one embodiment, the thermal resistance R on following formulae discovery stratum can be adopted ₁:

$R_1=\frac{f\left(t\right)}{2{\mathrm{\πK}}_e}---\left(1\right)$

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

Wherein, K _erepresent formation thermal conductivity, unit is W/ (mK); A represents the average coefficient of heat transfer in stratum, and unit is m ²/ d; T represents the oil well production time; r _hrepresent wellbore radius (namely gas injection well axis is to the distance of cement sheath outer wall), unit is m.

In one embodiment, the thermal resistance R of following formulae discovery cement sheath can be adopted ₂:

$R_2=\frac{1}{2{\mathrm{\πK}}_{cem}}ln\frac{r_h}{r_{co}}---\left(3\right)$

Wherein, K _cemrepresent cement sheath coefficient of thermal conductivity, unit is W/ (mK); r _hrepresent wellbore radius, unit is m; r _corepresent sleeve outer wall radius, unit is m.

In one embodiment, the thermal resistance R between following formulae discovery sleeve pipe inside and outside wall can be adopted ₃:

$R_3=\frac{1}{2{\mathrm{\πK}}_{cas}}ln\frac{r_{co}}{r_{ci}}---\left(4\right)$

Wherein, K _casrepresent sleeve pipe coefficient of thermal conductivity, unit is W/ (mK); r _cirepresent internal surface of sleeve pipe radius, unit is m; r _corepresent sleeve outer wall radius, unit is m.

In one embodiment, the thermal resistance R between air in following formulae discovery oil jacket annular space and sleeve pipe can be adopted ₄:

$R_4=\frac{1}{2\mathrm{\π}(h_{c1}+h_{r1})r_{ci}}---\left(5\right)$

Wherein, h _c1represent the free convection heat transfer coefficient of air in oil jacket annular space, unit is W/ (m ²k); h _r1represent the heat radiation thermal transmittance of air in oil jacket annular space, unit is W/ (m ²k); r _cirepresent internal surface of sleeve pipe radius.

Adopt following formulae discovery heat radiation thermal transmittance h _r1:

$h_{r1}={\mathrm{\δF}}_{tci}(T_{to}^{*2}+T_{ci}^{*2})(T_{to}^{*}+T_{ci}^{*})---\left(6\right)$

$T_{to}^{*}=T_{to}+273.15,T_{ci}^{*}=T_{ci}+273.15---\left(7\right)$

$\frac{1}{F_{tci}}=\frac{1}{{\mathrm{\ϵ}}_o}+\frac{r_{to}}{r_{ci}}\left(\frac{1}{{\mathrm{\ϵ}}_{ci}}-1\right)---\left(8\right)$

Wherein, δ represents Stefan-Boltzmann (this special fence-Boltzmann) constant, and value is 2.189 × 10 ^-8w/ (m ²k); F _tcirepresent that oil-pipe external wall surface is to internal surface of sleeve pipe surface emissivity coefficient of efficiency; T _torepresent oil-pipe external wall temperature; T _cirepresent internal surface of sleeve pipe temperature; ε _orepresent oil-pipe external wall blackness; ε _cirepresent internal surface of sleeve pipe blackness; r _torepresent oil-pipe external wall radius;

Adopt following formulae discovery free convection heat transfer coefficient h _c1:

$h_{c1}=\frac{0.049{\left(G_r{P}_r\right)}^{0.33}{P}_r^{0.074}{K}_{ha}}{r_{to}\ln \frac{r_{ci}}{r_{to}}}---\left(9\right)$

$G_r=\frac{{(r_{ci}-r_{to})}^3{\mathrm{g\ρ}}_{an}^2\mathrm{\β}(T_{to}-T_{ci})}{U_{an}^2}---\left(10\right)$

$P_r=\frac{C_{an}-U_{an}}{K_{ha}}---\left(11\right)$

Wherein, G _rrepresent Grashof number (grashof number); P _rrepresent Prandtl number (Prandtl number); K _harepresent the coefficient of thermal conductivity of the air of oil jacket annular space, unit is W/ (mK); G represents acceleration of gravity, and unit is m/s ²; ρ _anrepresent that the air of oil jacket annular space is at average temperature T _anunder density, unit is kg/m ³; U _anrepresent that the air of oil jacket annular space is at average temperature T _anunder viscosity, unit is mPas; C _anrepresent that the air of oil jacket annular space is at average temperature T _anunder thermal capacitance, unit is J (m ³k); β represents the thermal cubic expansion coefficient of air in oil jacket annular space, is a constant, and value can be 1.78 × 10 ^-3.

The thermal resistance of oil pipe can divide two sections to calculate, and as shown in Figure 1, with B point packer for boundary, AB section (i.e. epimere oil pipe) is plain tubing, and BC section (i.e. hypomere oil pipe) has three kinds of situations: instlated tubular, screen casing or plain tubing.Its computational process is below described.

In one embodiment, the thermal resistance R between oil pipe inside and outside wall is calculated ₅as shown in formula (12) to (15).

For epimere oil pipe, adopt its thermal resistance R of following formulae discovery ₅:

$R_5=\frac{1}{2{\mathrm{\πK}}_{tub}}ln\frac{r_{to}}{r_{ti}}---\left(12\right)$

Wherein, K _tubrepresent oil pipe coefficient of thermal conductivity, unit is W/ (mK); r _torepresent oil-pipe external wall radius, unit is m; r _tirepresent tube inner wall radius, unit is m.

If hypomere oil pipe is instlated tubular, adopt its thermal resistance R of following formulae discovery ₅:

$R_5=\frac{1}{2{\mathrm{\πK}}_{tub}}ln\frac{r_o}{r_i}+\frac{1}{2{\mathrm{\πK}}_{ins}}ln\frac{r_i}{r_{to1}}+\frac{1}{2{\mathrm{\πK}}_{tub}}ln\frac{r_{to1}}{r_{ti1}}---\left(13\right)$

Wherein, K _tubrepresent oil pipe coefficient of thermal conductivity, unit is W/ (mK); r _orepresent instlated tubular outer tube outer wall radius, unit is m; r _irepresent instlated tubular outer tube wall radius, unit is m; K _insrepresent instlated tubular coefficient of thermal conductivity, unit is W/ (mK); r _to1represent instlated tubular outer wall of inner tube radius, unit is m; r _ti1represent instlated tubular inner tube wall radius, unit is m.

If hypomere oil pipe is screen casing, adopt its thermal resistance R of following formulae discovery ₅:

$R_5=\frac{1}{2{\mathrm{\πK}}_{sie}}ln\frac{r_{to2}}{r_{ti2}}---\left(14\right)$

Wherein, K _sierepresent screen casing coefficient of thermal conductivity, unit is W/ (mK); r _to2represent screen casing exterior radius, unit is m; r _ti2represent screen casing inwall radius, unit is m.

If hypomere oil pipe is plain tubing, its thermal resistance calculation is identical with epimere oil pipe, concrete, adopts its thermal resistance R of following formula ₅:

$R_5=\frac{1}{2{\mathrm{\πK}}_{tub}}ln\frac{r_{to}}{r_{ti}}---\left(15\right)$

Wherein, K _tubrepresent oil pipe coefficient of thermal conductivity, unit is W/ (mK); r _torepresent oil-pipe external wall radius, unit is m; r _tirepresent tube inner wall radius, unit is m.

In one embodiment, the thermal convection current thermal resistance R of following formulae discovery oil inner air tube can be adopted ₆:

$R_6=\frac{r_{to}}{2{\mathrm{\πh}}_f{r}_{ti}}---\left(16\right)$

Wherein, h _frepresent the coefficient of thermal conductivity coefficient of oily inner air tube, value is 0.05W/ (mK); r _tirepresent tube inner wall radius; r _torepresent oil-pipe external wall radius.

In one embodiment, according to R ₁to R ₆adopt following formulae discovery pit shaft entire thermal resistance diametrically:

R＝R ₁+R ₂+R ₃+R ₄+R ₅+R ₆(17)

In FIG, pit shaft is divided in the axial direction several pit shaft unit, the initial temperature (i.e. the temperature of oily inner air tube after electric igniter heating) of oil pipe is the T calculated by formula (22) and (23) _s, main heat waste is heat waste diametrically.

In one embodiment, according to temperature T _s, entire thermal resistance and formation temperature, calculate pit shaft heat waste diametrically, comprising: according to law of conservation of energy, adopt following formulae discovery heat waste:

$Q=\frac{T_s-T_e}{R}dl---\left(18\right)$

Wherein, Q represents pit shaft unit radial heat waste, and unit is W; T _erepresent formation temperature, unit is DEG C; R represents pit shaft unit radial entire thermal resistance.

In one embodiment, according to temperature T _s, heat waste and electric igniter power, calculate the air themperature of oil pipe, comprising:

Following formulae discovery is adopted to be in the air themperature of epimere oil pipe (i.e. AB section):

CmT _s-Q/1000+0.4P＝CmT′ _s(19)

Following formulae discovery is adopted to be in the air themperature of hypomere oil pipe (i.e. BC section):

CmT _s-Q/1000+0.6P＝CmT′ _s(20)

Wherein, T ' _srepresent the air themperature after change in oil pipe, unit is DEG C; C represents the specific heat capacity of air, and value is 1.0069kJ/ (kg ﹒ DEG C); M represents the mass flow of air, and unit is kg/s; P represents the power of electric igniter; Q represents pit shaft unit radial heat waste.

In one embodiment, the change of following formulae discovery formation temperature can be adopted in step S207:

T _e＝T _ins+αdl(21)

Wherein, T _insrepresent surface temperature, unit is DEG C; α represents geothermal gradient, and unit is DEG C/m; T _erepresent formation temperature, unit is DEG C.

In one embodiment, consider that electric igniter cable probably has 40% along journey heat waste, calculate the temperature T of air after electric igniter heating being injected into oil pipe _s, comprising:

Adopt the temperature T of the air of following formulae discovery epimere oil pipe after electric igniter heating _s:

CmT+0.4P＝CmT _s(22)

Adopt the air of following formulae discovery hypomere oil pipe through electric igniter temperature after heating change T _s:

CmT+0.6P＝CmT _s(23)

Wherein, T represents the initial temperature of air, and unit is DEG C; C represents the specific heat capacity of air; M represents the mass flow of air; P represents the power of electric igniter.

Based on same inventive concept, the embodiment of the present invention additionally provides the determining device of a kind of combustion in situ general gas injection electric ignition well bore temperature distribution, may be used for the method realized described by above-described embodiment, repeats part and repeats no more.Following used, term " unit " can realize the software of predetermined function and/or the combination of hardware.Although the system described by following examples preferably realizes with software, hardware, or the realization of the combination of software and hardware also may and conceived.

Fig. 3 is the structured flowchart of the determining device of the combustion in situ general gas injection electric ignition well bore temperature distribution of the embodiment of the present invention, as shown in Figure 3, this device comprises: division unit 31, first computing unit 32, second computing unit 33, the 3rd computing unit 34, the 4th computing unit 35, the 5th computing unit 36 and iterative computation unit 37.Below this structure is specifically described.

Division unit 31, for pit shaft being divided in the axial direction multiple pit shaft unit, the length of each pit shaft unit is dl, makes l=0, k=1, and wherein, l represents the length of current calculating, and k represents iterations;

First computing unit 32, for calculating the temperature T of air after electric igniter heating being injected into oil pipe _s;

Second computing unit 33, for calculating the thermal resistance R on stratum respectively ₁, cement sheath thermal resistance R ₂, thermal resistance R between sleeve pipe inside and outside wall ₃, air in oil jacket annular space and the thermal resistance R between sleeve pipe ₄, thermal resistance R between oil pipe inside and outside wall ₅and the thermal convection current thermal resistance R of oily inner air tube ₆; Wherein, pit shaft radially comprises from the inside to the outside successively: oil pipe, sleeve pipe and cement sheath, the position corresponding to burning torch top in oil jacket annular space is connected with packer, take packer as boundary, oil pipe is divided into epimere oil pipe and hypomere oil pipe, hypomere oil pipe is instlated tubular, screen casing or plain tubing, and pit shaft outside is stratum;

3rd computing unit 34, for according to R ₁to R ₆calculate pit shaft entire thermal resistance diametrically;

4th computing unit 35, for according to temperature T _s, entire thermal resistance and formation temperature, calculate pit shaft heat waste diametrically;

5th computing unit 36, for according to temperature T _s, heat waste and electric igniter power, calculate the air themperature of oil pipe;

Iterative computation unit 37, for making l=l+dl, k=k+1, according to the change of formation temperature, utilize the second computing unit 33 to carry out iterative computation to the 5th computing unit 36, until l >=L, then iteration terminates, obtain the temperature distribution history of oil pipe, wherein, L represents the total length of oil pipe.

Pass through said apparatus, consider the change of the many factors such as well bore and tubing string structure, the heat transfer of pit shaft radial direction and stratum thermophysical property along well depth, pit shaft is divided into some sections, obtain the physical parameter (thermal resistance, thermal transmittance) of correspondent section, part physical parameter is the function of temperature, adopt solution by iterative method, calculate oil pipe Temperature Distribution.In this device energy accurate Calculation general gas injection ignition process situation, any flow condition, any time are along the Temperature Distribution of gas injection well pit shaft.Meanwhile, computational process is simple and convenient, and have higher precision, iterations is low, and computational efficiency is high, has extraordinary stability and convergence.According to the Temperature Distribution of pit shaft, the air themperature arriving oil reservoir effectively can be predicted, to adjust gas injection rate and igniter power, and then the smooth enforcement of guarantee point ignition technique.

In one embodiment, the second computing unit 33 is specifically for adopting the thermal resistance R on following formulae discovery stratum ₁:

$R_1=\frac{f\left(t\right)}{2{\mathrm{\πK}}_e},$

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

Wherein, K _erepresent formation thermal conductivity; A represents the average coefficient of heat transfer in stratum; T represents the oil well production time; r _hrepresent wellbore radius.

In one embodiment, the second computing unit 33 is specifically for adopting the thermal resistance R of following formulae discovery cement sheath ₂:

$R_2=\frac{1}{2{\mathrm{\πK}}_{cem}}ln\frac{r_h}{r_{co}},$

Wherein, K _cemrepresent cement sheath coefficient of thermal conductivity; r _hrepresent wellbore radius; r _corepresent sleeve outer wall radius.

In one embodiment, the second computing unit 33 is specifically for adopting the thermal resistance R between following formulae discovery sleeve pipe inside and outside wall ₃:

$R_3=\frac{1}{2{\mathrm{\πK}}_{cas}}ln\frac{r_{co}}{r_{ci}},$

Wherein, K _casrepresent sleeve pipe coefficient of thermal conductivity; r _cirepresent internal surface of sleeve pipe radius; r _corepresent sleeve outer wall radius.

In one embodiment, the second computing unit 33 is specifically for adopting the thermal resistance R between air in following formulae discovery oil jacket annular space and sleeve pipe ₄:

$R_4=\frac{1}{2\mathrm{\π}(h_{c1}+h_{r1})r_{ci}},$

Wherein, h _c1represent the free convection heat transfer coefficient of air in oil jacket annular space; h _r1represent the heat radiation thermal transmittance of air in oil jacket annular space; r _cirepresent internal surface of sleeve pipe radius;

Adopt following formulae discovery heat radiation thermal transmittance h _r1:

$h_{r1}={\mathrm{\δF}}_{tci}(T_{to}^{*2}+T_{ci}^{*2})(T_{to}^{*}+T_{ci}^{*}),$

$T_{to}^{*}=T_{to}+273.15,T_{ci}^{*}=T_{ci}+273.15,$

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

Wherein, δ represents Stefan-Boltzmann constant; F _tcirepresent that oil-pipe external wall surface is to internal surface of sleeve pipe surface emissivity coefficient of efficiency; T _torepresent oil-pipe external wall temperature; T _cirepresent internal surface of sleeve pipe temperature; ε _orepresent oil-pipe external wall blackness; ε _cirepresent internal surface of sleeve pipe blackness; r _torepresent oil-pipe external wall radius;

Adopt following formulae discovery free convection heat transfer coefficient h _c1:

$h_{c1}=\frac{0.049{\left(G_r{P}_r\right)}^{0.33}{P}_r^{0.074}{K}_{ha}}{r_{to}\ln \frac{r_{ci}}{r_{to}}},$

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

$P_r=\frac{C_{an}-U_{an}}{K_{ha}},$

Wherein, G _rrepresent Grashof number; P _rrepresent Prandtl number; K _harepresent the coefficient of thermal conductivity of the air of oil jacket annular space; G represents acceleration of gravity; ρ _anrepresent that the air of oil jacket annular space is at average temperature T _anunder density; U _anrepresent that the air of oil jacket annular space is at average temperature T _anunder viscosity; C _anrepresent that the air of oil jacket annular space is at average temperature T _anunder thermal capacitance; β represents the thermal cubic expansion coefficient of air in oil jacket annular space.

In one embodiment, the second computing unit 33 specifically for:

For epimere oil pipe, adopt its thermal resistance R of following formulae discovery ₅:

$R_5=\frac{1}{2{\mathrm{\πK}}_{tub}}ln\frac{r_{to}}{r_{ti}},$

Wherein, K _tubrepresent oil pipe coefficient of thermal conductivity; r _torepresent oil-pipe external wall radius; r _tirepresent tube inner wall radius;

If hypomere oil pipe is instlated tubular, adopt its thermal resistance R of following formulae discovery ₅:

$R_5=\frac{1}{2{\mathrm{\πK}}_{tub}}ln\frac{r_o}{r_i}+\frac{1}{2{\mathrm{\πK}}_{ins}}ln\frac{r_i}{r_{to1}}+\frac{1}{2{\mathrm{\πK}}_{tub}}ln\frac{r_{to1}}{r_{ti1}},$

Wherein, K _tubrepresent oil pipe coefficient of thermal conductivity; r _orepresent instlated tubular outer tube outer wall radius; r _irepresent instlated tubular outer tube wall radius; K _insrepresent instlated tubular coefficient of thermal conductivity; r _to1represent instlated tubular outer wall of inner tube radius; r _ti1represent instlated tubular inner tube wall radius;

If hypomere oil pipe is screen casing, adopt its thermal resistance R of following formulae discovery ₅:

$R_5=\frac{1}{2{\mathrm{\πK}}_{sie}}ln\frac{r_{to2}}{r_{ti2}},$

Wherein, K _sierepresent screen casing coefficient of thermal conductivity; r _to2represent screen casing exterior radius; r _ti2represent screen casing inwall radius;

If hypomere oil pipe is plain tubing, adopt its thermal resistance R of following formula ₅:

$R_5=\frac{1}{2{\mathrm{\πK}}_{tub}}ln\frac{r_{to}}{r_{ti}},$

Wherein, K _tubrepresent oil pipe coefficient of thermal conductivity; r _torepresent oil-pipe external wall radius; r _tirepresent tube inner wall radius.

In one embodiment, the second computing unit 33 is specifically for adopting the thermal convection current thermal resistance R of following formulae discovery oil inner air tube ₆:

$R_6=\frac{r_{to}}{2{\mathrm{\πh}}_f{r}_{ti}},$

Wherein, h _frepresent the coefficient of thermal conductivity coefficient of oily inner air tube; r _tirepresent tube inner wall radius; r _torepresent oil-pipe external wall radius.

In one embodiment, the 3rd computing unit 34 is specifically for adopting following formulae discovery pit shaft entire thermal resistance diametrically:

R＝R ₁+R ₂+R ₃+R ₄+R ₅+R ₆。

In one embodiment, the 4th computing unit 35 specifically for according to law of conservation of energy, adopts following formulae discovery heat waste:

$Q=\frac{T_s-T_e}{R}dl,$

Wherein, Q represents pit shaft unit radial heat waste; T _erepresent formation temperature; R represents pit shaft unit radial entire thermal resistance.

In one embodiment, the 5th computing unit 36 specifically for:

Following formulae discovery is adopted to be in the air themperature of epimere oil pipe:

CmT _s-Q/1000+0.4P＝CmT′ _s，

Following formulae discovery is adopted to be in the air themperature of hypomere oil pipe:

CmT _s-Q/1000+0.6P＝CmT′ _s，

Wherein, T ' _srepresent the air themperature after change in oil pipe; C represents the specific heat capacity of air; M represents the mass flow of air; P represents the power of electric igniter; Q represents pit shaft unit radial heat waste.

In one embodiment, iterative computation unit 37 is specifically for adopting the change of following formulae discovery formation temperature:

T _e＝T _ins+αdl，

Wherein, T _insrepresent surface temperature; α represents geothermal gradient; T _erepresent formation temperature.

In one embodiment, the first computing unit 32 is specifically for adopting the temperature T of the air of following formulae discovery epimere oil pipe after electric igniter heating _s:

CmT+0.4P＝CmT _s，

Adopt the air of following formulae discovery hypomere oil pipe through electric igniter temperature after heating change T _s:

CmT+0.6P＝CmT _s，

Wherein, T represents the initial temperature of air; C represents the specific heat capacity of air; M represents the mass flow of air; P represents the power of electric igniter.

Certainly, above-mentioned Module Division just a kind of signal divides, and the present invention is not limited thereto.As long as the Module Division of object of the present invention can be realized, protection scope of the present invention all should be belonged to.

In order to more clearly explain the defining method of above-mentioned combustion in situ general gas injection electric ignition well bore temperature distribution and device, be described below in conjunction with specific embodiment, but it should be noted that this embodiment is only to better the present invention is described, do not form and the present invention is limited improperly.

(1) pit shaft is divided in the vertical several pit shaft unit, each pit shaft element length is dl, and calculate from well head, make l=0, k=1, air injects at well head, and the initial temperature of air is T ₀, make T _s=T ₀.

(2) R is calculated ₁, R ₂, R ₃, R ₅, R ₆, make R ₄=0 (due to R ₄relevant with thermal transmittance, thermal transmittance is relevant with the temperature of pipe, and does not know temperature value at first, therefore, first arranges R ₄value is 0), calculate entire thermal resistance R by formula (17).

(3) heat waste is calculated by formula (18)

(4) oil-pipe external wall temperature T is calculated _to=T _s-(R ₅+ R ₆) × Q/dl.

(5) internal surface of sleeve pipe temperature T is calculated _ci=T _e+ (R ₁+ R ₂+ R ₃) × Q/dl.

(6) R is calculated by formula (5) ~ (11) ₄.

(7) again entire thermal resistance R is calculated by formula (17).

(8) again heat waste is calculated

(9) the temperature T ' of oil pipe air is calculated by formula (19) ~ (20) segmentation _s.

(10) k=k+1 is made, l=l+dl, by formula (21) fo pination temperature change T _e=T _ins+ adl, returns (3) step and continues iterative computation; If l>=L (oil pipe total length), then iteration terminates.Obtaining the temperature distribution history of oil pipe, is instlated tubular for BC section, and oil pipe temperature curve as shown in Figure 4.

In sum, the embodiment of the present invention is for the problem not yet having general gas injection ignition process well-sinking thermal field defining method at present, propose defining method and the device of a kind of combustion in situ general gas injection electric ignition well bore temperature distribution, during for combustion in situ electric ignition, the calculating of general gas injection gas injection well well bore temperature distribution.Consider the change of the many factors such as well bore and tubing string structure, the heat transfer of pit shaft radial direction and stratum thermophysical property along well depth, pit shaft is divided into some sections, obtains the physical parameter of correspondent section, part physical parameter is the function of temperature, adopt solution by iterative method, calculate oil pipe Temperature Distribution.According to the Temperature Distribution of pit shaft, the air themperature arriving oil reservoir effectively can be predicted, to adjust gas injection rate and igniter power, and then the smooth enforcement of guarantee point ignition technique.

The present invention adopts the corresponding Mathematical Modeling of thermal conduction study method establishment, and has carried out computer programming to the method.When setting up temperature distribution model, suppose that the heat transfer in pit shaft is steady state heat transfer, heat transfer in pit shaft surrounding formation is unsteady-state heat transfer, the heat waste in radial direction is not only considered when calculating well bore temperature distribution, have also contemplated that air flowing along the heat transfer in well depth direction to the impact of well bore temperature distribution, carry out segmentation according to the tubular column structure of oil pipe each section of tubing string difference, different situations calculate respectively.Computational process is simple and convenient, and have higher precision, iterations is low, and computational efficiency is high, has extraordinary stability and convergence, is more applicable to computer programming.Can in accurate Calculation general gas injection ignition process situation, any flow condition, any time are along the Temperature Distribution of gas injection well pit shaft

Describe and can be understood in flow chart or in this any process otherwise described or method, represent and comprise one or more for realizing the module of the code of the executable instruction of the step of specific logical function or process, fragment or part, and the scope of the preferred embodiment of the present invention comprises other realization, wherein can not according to order that is shown or that discuss, comprise according to involved function by the mode while of basic or by contrary order, carry out n-back test, this should understand by embodiments of the invention person of ordinary skill in the field.

Should be appreciated that each several part of the present invention can realize with hardware, software, firmware or their combination.In the above-described embodiment, multiple step or method can with to store in memory and the software performed by suitable instruction execution system or firmware realize.Such as, if realized with hardware, the same in another embodiment, can realize by any one in following technology well known in the art or their combination: the discrete logic with the logic gates for realizing logic function to data-signal, there is the special IC of suitable combinational logic gate circuit, programmable gate array (PGA), field programmable gate array (FPGA) etc.

Above-described specific embodiment; object of the present invention, technical scheme and beneficial effect are further described; be understood that; the foregoing is only specific embodiments of the invention; the protection domain be not intended to limit the present invention; within the spirit and principles in the present invention all, any amendment made, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (13)

1. a defining method for combustion in situ general gas injection electric ignition well bore temperature distribution, is characterized in that, comprising:

Step 1, is divided into multiple pit shaft unit in the axial direction by pit shaft, the length of each pit shaft unit is dl, makes l=0, k=1, and wherein, l represents the length of current calculating, and k represents iterations;

Step 2, calculates the temperature T of air after electric igniter heating being injected into oil pipe _s;

Step 3, calculates the thermal resistance R on stratum respectively ₁, cement sheath thermal resistance R ₂, thermal resistance R between sleeve pipe inside and outside wall ₃, air in oil jacket annular space and the thermal resistance R between sleeve pipe ₄, thermal resistance R between oil pipe inside and outside wall ₅and the thermal convection current thermal resistance R of oily inner air tube ₆; Wherein, described pit shaft radially comprises from the inside to the outside successively: oil pipe, sleeve pipe and cement sheath, the position corresponding to burning torch top in oil jacket annular space is connected with packer, with described packer for boundary, described oil pipe is divided into epimere oil pipe and hypomere oil pipe, described hypomere oil pipe is instlated tubular, screen casing or plain tubing, and described pit shaft outside is stratum;

Step 4, according to R ₁to R ₆calculate pit shaft entire thermal resistance diametrically;

Step 5, according to described temperature T _s, described entire thermal resistance and formation temperature, calculate pit shaft heat waste diametrically;

Step 6, according to described temperature T _s, described heat waste and described electric igniter power, calculate the air themperature of oil pipe;

Step 7, makes l=l+dl, k=k+1, and according to the change of formation temperature, repeat above-mentioned steps 3 to step 6, carry out iterative computation, until l >=L, then iteration terminates, and obtains the temperature distribution history of described oil pipe, and wherein, L represents the total length of oil pipe.

2. method according to claim 1, is characterized in that, adopts the thermal resistance R on following formulae discovery stratum ₁:

$R_1=\frac{f\left(t\right)}{2{\mathrm{\πK}}_e},$

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

Wherein, K _erepresent formation thermal conductivity; A represents the average coefficient of heat transfer in stratum; T represents the oil well production time; r _hrepresent wellbore radius.

3. method according to claim 1, is characterized in that, adopts the thermal resistance R of following formulae discovery cement sheath ₂:

$R_2=\frac{1}{2{\mathrm{\πK}}_{cem}}ln\frac{r_h}{r_{co}},$

Wherein, K _cemrepresent cement sheath coefficient of thermal conductivity; r _hrepresent wellbore radius; r _corepresent sleeve outer wall radius.

4. method according to claim 1, is characterized in that, adopts the thermal resistance R between following formulae discovery sleeve pipe inside and outside wall ₃:

$R_3=\frac{1}{2{\mathrm{\πK}}_{cas}}ln\frac{r_{co}}{r_{ci}},$

Wherein, K _casrepresent sleeve pipe coefficient of thermal conductivity; r _cirepresent internal surface of sleeve pipe radius; r _corepresent sleeve outer wall radius.

5. method according to claim 1, is characterized in that, adopts the thermal resistance R between air in following formulae discovery oil jacket annular space and sleeve pipe ₄:

$R_4=\frac{1}{2\mathrm{\π}(h_{c1}+h_{r1})r_{ci}},$

Wherein, h _c1represent the free convection heat transfer coefficient of air in oil jacket annular space; h _r1represent the heat radiation thermal transmittance of air in oil jacket annular space; r _cirepresent internal surface of sleeve pipe radius;

Adopt following formulae discovery heat radiation thermal transmittance h _r1:

$h_{r1}={\mathrm{\δF}}_{tci}(T_{to}^{*2}+T_{ci}^{*2})(T_{to}^{*}+T_{ci}^{*}),$

$T_{to}^{*}=T_{to}+273.15,T_{ci}^{*}=T_{ci}+273.15,$

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

Wherein, δ represents Stefan-Boltzmann constant; F _tcirepresent that oil-pipe external wall surface is to internal surface of sleeve pipe surface emissivity coefficient of efficiency; T _torepresent oil-pipe external wall temperature; T _cirepresent internal surface of sleeve pipe temperature; ε _orepresent oil-pipe external wall blackness; ε _cirepresent internal surface of sleeve pipe blackness; r _torepresent oil-pipe external wall radius;

Adopt following formulae discovery free convection heat transfer coefficient h _c1:

$h_{c1}=\frac{0.049{\left(G_r{P}_r\right)}^{0.33}{P}_r^{0.074}{K}_{ha}}{r_{to}\ln \frac{r_{ci}}{r_{to}}},$

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

$P_r=\frac{C_{an}-U_{an}}{K_{ha}},$

Wherein, G _rrepresent Grashof number; P _rrepresent Prandtl number; K _harepresent the coefficient of thermal conductivity of the air of oil jacket annular space; G represents acceleration of gravity; ρ _anrepresent that the air of oil jacket annular space is at average temperature T _anunder density; U _anrepresent that the air of oil jacket annular space is at average temperature T _anunder viscosity; C _anrepresent that the air of oil jacket annular space is at average temperature T _anunder thermal capacitance; β represents the thermal cubic expansion coefficient of air in oil jacket annular space.

6. method according to claim 1, is characterized in that, calculates the thermal resistance R between oil pipe inside and outside wall ₅comprise:

For epimere oil pipe, adopt its thermal resistance R of following formulae discovery ₅:

$R_5=\frac{1}{2{\mathrm{\πK}}_{tub}}ln\frac{r_{to}}{r_{ti}},$

Wherein, K _tubrepresent oil pipe coefficient of thermal conductivity; r _torepresent oil-pipe external wall radius; r _tirepresent tube inner wall radius;

If hypomere oil pipe is instlated tubular, adopt its thermal resistance R of following formulae discovery ₅:

$R_5=\frac{1}{2{\mathrm{\πK}}_{tub}}\ln \frac{r_o}{r_i}+\frac{1}{2{\mathrm{\πK}}_{ins}}ln\frac{r_i}{r_{to1}}+\frac{1}{2{\mathrm{\πK}}_{tub}}\ln \frac{r_{to1}}{r_{ti1}},$

Wherein, K _tubrepresent oil pipe coefficient of thermal conductivity; r _orepresent instlated tubular outer tube outer wall radius; r _irepresent instlated tubular outer tube wall radius; K _insrepresent instlated tubular coefficient of thermal conductivity; r _to1represent instlated tubular outer wall of inner tube radius; r _ti1represent instlated tubular inner tube wall radius;

If hypomere oil pipe is screen casing, adopt its thermal resistance R of following formulae discovery ₅:

$R_5=\frac{1}{2{\mathrm{\πK}}_{sie}}\ln \frac{r_{to2}}{r_{ti2}},$

Wherein, K _sierepresent screen casing coefficient of thermal conductivity; r _to2represent screen casing exterior radius; r _ti2represent screen casing inwall radius;

If hypomere oil pipe is plain tubing, adopt its thermal resistance R of following formula ₅:

$R_5=\frac{1}{2{\mathrm{\πK}}_{tub}}ln\frac{r_{to}}{r_{ti}},$

Wherein, K _tubrepresent oil pipe coefficient of thermal conductivity; r _torepresent oil-pipe external wall radius; r _tirepresent tube inner wall radius.

7. method according to claim 1, is characterized in that, adopts the thermal convection current thermal resistance R of following formulae discovery oil inner air tube ₆:

$R_6=\frac{r_{to}}{2{\mathrm{\πh}}_f{r}_{ti}},$

Wherein, h _frepresent the coefficient of thermal conductivity coefficient of oily inner air tube; r _tirepresent tube inner wall radius; r _torepresent oil-pipe external wall radius.

8. method according to claim 1, is characterized in that, according to R ₁to R ₆adopt following formulae discovery pit shaft entire thermal resistance diametrically:

R＝R ₁+R ₂+R ₃+R ₄+R ₅+R ₆。

9. method according to claim 1, is characterized in that, according to described temperature T _s, described entire thermal resistance and formation temperature, calculate pit shaft heat waste diametrically, comprising:

According to law of conservation of energy, adopt heat waste described in following formulae discovery:

$Q=\frac{T_s-T_e}{R}dl,$

Wherein, Q represents pit shaft unit radial heat waste; T _erepresent formation temperature; R represents pit shaft unit radial entire thermal resistance.

10. method according to claim 1, is characterized in that, according to described temperature T _s, described heat waste and described electric igniter power, calculate the air themperature of oil pipe, comprising:

Following formulae discovery is adopted to be in the air themperature of epimere oil pipe:

CmT _s-Q/1000+0.4P＝CmT _s'，

Following formulae discovery is adopted to be in the air themperature of hypomere oil pipe:

CmT _s-Q/1000+0.6P＝CmT _s'，

Wherein, T ' _srepresent the air themperature after change in oil pipe; C represents the specific heat capacity of air; M represents the mass flow of air; P represents the power of electric igniter; Q represents pit shaft unit radial heat waste.

11. methods according to claim 1, is characterized in that, adopt the change of following formulae discovery formation temperature in step 7:

T _e＝T _ins+αdl，

Wherein, T _insrepresent surface temperature; α represents geothermal gradient; T _erepresent formation temperature.

12. methods according to claim 1, is characterized in that, calculate the temperature T of air after electric igniter heating being injected into oil pipe _s, comprising:

Adopt the temperature T of the air of following formulae discovery epimere oil pipe after electric igniter heating _s:

CmT+0.4P＝CmT _s，

Adopt the air of following formulae discovery hypomere oil pipe through electric igniter temperature after heating change T _s:

CmT+0.6P＝CmT _s，

Wherein, T represents the initial temperature of air; C represents the specific heat capacity of air; M represents the mass flow of air; P represents the power of electric igniter.

The determining device of 13. 1 kinds of combustion in situ general gas injection electric ignition well bore temperature distribution, is characterized in that, comprising:

Division unit, for pit shaft being divided in the axial direction multiple pit shaft unit, the length of each pit shaft unit is dl, makes l=0, k=1, and wherein, l represents the length of current calculating, and k represents iterations;

First computing unit, for calculating the temperature T of air after electric igniter heating being injected into oil pipe _s;

Second computing unit, for calculating the thermal resistance R on stratum respectively ₁, cement sheath thermal resistance R ₂, thermal resistance R between sleeve pipe inside and outside wall ₃, air in oil jacket annular space and the thermal resistance R between sleeve pipe ₄, thermal resistance R between oil pipe inside and outside wall ₅and the thermal convection current thermal resistance R of oily inner air tube ₆; Wherein, described pit shaft radially comprises from the inside to the outside successively: oil pipe, sleeve pipe and cement sheath, the position corresponding to burning torch top in oil jacket annular space is connected with packer, with described packer for boundary, described oil pipe is divided into epimere oil pipe and hypomere oil pipe, described hypomere oil pipe is instlated tubular, screen casing or plain tubing, and described pit shaft outside is stratum;

3rd computing unit, for according to R ₁to R ₆calculate pit shaft entire thermal resistance diametrically;

4th computing unit, for according to described temperature T _s, described entire thermal resistance and formation temperature, calculate pit shaft heat waste diametrically;

5th computing unit, for according to described temperature T _s, described heat waste and described electric igniter power, calculate the air themperature of oil pipe;

Iterative computation unit, for making l=l+dl, k=k+1, according to the change of formation temperature, utilize the second computing unit to carry out iterative computation to the 5th computing unit, until l >=L, then iteration terminates, obtain the temperature distribution history of described oil pipe, wherein, L represents the total length of oil pipe.