CN107506948B - Shale oil gas comprehensive yield analysis method based on dynamic drainage volume - Google Patents

Shale oil gas comprehensive yield analysis method based on dynamic drainage volume Download PDF

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CN107506948B
CN107506948B CN201710890029.5A CN201710890029A CN107506948B CN 107506948 B CN107506948 B CN 107506948B CN 201710890029 A CN201710890029 A CN 201710890029A CN 107506948 B CN107506948 B CN 107506948B
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shale oil
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袁彬
王文东
王凯
郑达
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China University of Petroleum UPC East China
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Abstract

The invention discloses a shale oil gas comprehensive yield analysis method based on dynamic drainage volume, which comprises the steps of arranging preparation data; initially estimating the limit leakage flow volume and the effective crack half length, and calculating the dynamic leakage flow volume, the average reservoir pressure change and the pressure correction factor; drawing a yield normalized simulated pressure curve, calculating the fluid diffusion coefficient in a fracturing transformation area, drawing a square root time characteristic curve, calculating the effective fracture half-length, and determining the ultimate discharge volume and the final output degree according to a modified Duong method; if the difference between the calculated values of the effective crack half length and the limit leakage volume and the input value is large, substituting the calculated values again, and circulating until the convergence is consistent to obtain the accurate effective crack half length and the limit leakage volume; substituting the dynamic drainage volume formula into a macroscopic material balance model, and comparing to obtain the cumulative contribution of the size of the fracturing modification area to the shale oil and gas production; and determining the optimal fracture interval and the optimal well spacing of the fractured horizontal well. The invention improves the accuracy of shale oil gas yield dynamic analysis and evaluation.

Description

Shale oil gas comprehensive yield analysis method based on dynamic drainage volume
Technical Field
The invention relates to the technical field of oilfield development and optimization, in particular to a shale oil gas comprehensive yield analysis method based on a dynamic drainage volume.
Background
In the shale oil and gas development process, the historical yield analysis of a production well is an important means for acquiring formation information, evaluating the production quality and optimizing the oil and gas production. However, complex reservoir characteristics of shale oil and gas, dynamic desorption of oil and gas, micro-nano multi-scale non-Darcy seepage, fracture closure and shale shrinkage in the production process and other complex factors cause the conventional oil and gas dynamic analysis method to be inaccurate and not applicable any more, thereby bringing difficult challenges for evaluating and optimizing shale oil and gas development by utilizing production data.
The main reasons are as follows: (1) the existing method is suitable for simple well types and conventional fracturing wells, and the production dynamics of the volume fracturing horizontal well adopted in shale oil and gas development is difficult to accurately represent. (2) The existing method does not have complex distribution attributes of coupling shale oil gas nanometer-scale matrix pores and a multi-scale fracture network. (3) The existing method does not couple the influence of shale oil pyrolysis, adsorption and non-Darcy seepage characteristics on the production well yield. (4) Existing methods are based on the assumption of steady-state flow of reservoir fluids; the shale permeability is extremely low, the steady-state flow stage is difficult to achieve in a short time, and the whole production life is in the transient flow stage, so that the existing method is not suitable any more. (5) The prior method does not consider the influence of dynamic damage change of reservoir rock and cracks on yield in the development process; the shale oil-gas well yield decreases rapidly and the pressure failure is rapid, so that the shale oil-gas reservoir has large rock shrinkage and crack closure damage which are not negligible. (6) The existing method is difficult to synchronously optimize and predict based on historical data, and achieves the coupling analysis of real-time evaluation and prediction. Therefore, the conventional oil and gas dynamic analysis method is not suitable for shale oil and gas, and even brings large errors, thereby bringing difficult challenges for effectively and optimally developing shale oil and gas.
Disclosure of Invention
Aiming at the technical defects of the existing analysis method, the invention provides a shale oil and gas comprehensive yield analysis method based on dynamic drainage volume, which fully considers the characteristics of shale oil and gas development complex reservoirs and fluid characteristics, and comprises the influences of extremely low permeability of shale nano-pore matrix, complex fracture network distribution of a fractured horizontal well, oil and gas dynamic desorption, limited fracture transformation range, shale shrinkage deformation, fracture closure and the like on the shale oil and gas development, so that the shale oil and gas comprehensive yield analysis method is a comprehensive yield analysis method integrating historical evaluation, development optimization and yield prediction, and the shale oil and gas yield dynamic analysis and evaluation accuracy is improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
a shale oil and gas comprehensive yield analysis method based on a dynamic leakage flow volume comprises the following steps:
(I): preparing data arrangement; the data includes: shale reservoir petrophysical properties, fluid physical properties, well parameters, and production history of the target well;
the shale reservoir rock physical properties comprise compressibility, shale permeability and oil gas desorption parameters, the fluid physical properties comprise viscosity, volume coefficient and fluid compressibility, the well parameters comprise drilling and fracturing completion parameters, and the production history of the target well comprises oil gas water daily yield and cumulative yield.
(II): and initially estimating the limit leakage flow volume and the effective fracture half-length to obtain a calculation expression of the saturation and the dynamic leakage flow volume of the shale oil-gas well, substituting the calculation expression and the production history of the target well into a macroscopic material balance model, and calculating the dynamic leakage flow volume, the average reservoir pressure change and a pressure correction factor in the production process.
(III): drawing a relation curve of the yield normalized simulated pressure and time, identifying the flowing stage of the shale fractured horizontal well, and calculating the fluid diffusion coefficient in the fractured modified area according to the ending time of the early transient linear flow and the known fracture interval; then drawing a square root time characteristic curve to obtain the slope of the square root time characteristic curve, and calculating the effective crack half-length; and carrying out production data decreasing analysis according to the modified Duong method, and determining the limit leakage flow volume and the final output degree;
(IV): and (3) if the difference between the effective crack half length and the limit leakage volume calculated in the step (three) and the input value in the step (two) is larger, substituting the value calculated in the step (three) into the step (two), repeating the step (two) and the step (three) in sequence until the input value in the step (two) is consistent with the convergence of the effective crack half length and the limit leakage volume calculated in the step (three), and stopping calculating to obtain the accurate effective crack half length and the limit leakage volume.
(V): the shale oil and gas flow area comprises two parts: and (3) calculating and expressing the dynamic drainage volume in the shale oil and gas production process of the volume fractured horizontal well in the fracturing modified area and the non-modified matrix area, substituting the dynamic drainage volume into a macroscopic material balance model, and comparing to obtain the cumulative contribution of the fracturing modified area and the non-modified matrix area to the shale oil and gas production.
(VI): and (4) performing optimization determination on fracture parameters and well spacing of the shale oil and gas fracturing horizontal well after analysis, evaluation and prediction based on the shale oil and gas production data.
Preferably, in the step (ii), the limit drainage volume and the effective fracture half-length are initially estimated to obtain a shale oil and gas well saturation calculation expression (1) and a dynamic drainage volume calculation expression (2) in the shale oil and gas production process applicable to the volume fracture horizontal well, then the calculation expressions and the production history of the target well are substituted into the macroscopic material balance model (3), and the dynamic drainage volume, the reservoir average pressure change and the pressure correction factor in the production process are calculated according to the production history of the shale oil and gas well.
A shale oil-gas well saturation calculation expression:
wherein, subscript n represents parameter values at different production moments; subscript i represents the values of the parameters at the initial reservoir conditions; RF is shale oil production degree and fraction at different production moments; b isoiIs the initial reservoir pressure piVolume coefficient of shale oil of m3/m3;BtiIs the initial reservoir pressure piFluid volume coefficient of shale oil reservoir, m3/m3;SwiThe original water saturation and fraction of the shale oil reservoir; vp(n)Is production of tnDynamic drainage volume m of shale oil well at any moment3;BoIs the average pressure condition of the reservoirLower crude oil volume coefficient, m3/m3;Sw(n),So(n),Sg(n)At a dynamic discharge volume Vp(n)Formation crude oil, water and gas saturations in; (ii) a B ist(n)Is tnFluid volume coefficient, m, of shale reservoir at that moment3/m3;ct(n)Is tnIntegral compression coefficient of shale oil reservoir at any moment, Pa-1;Vp,maxIs the ultimate drainage volume, m, of a shale oil and gas production well3
The dynamic drainage volume calculation expression is applicable to the shale oil and gas production process of the volume fracturing horizontal well:
a. and (3) keeping the shale gas well production bottom flow pressure constant:
wherein,xfIs the effective fracture half-length; t different production moments of the fractured horizontal well, day; t is teIs the time of the end of the early linear flow of the fractured horizontal well, h is the shale reservoir thickness, m, ηoIs the diffusion coefficient of the peripheral unmodified area of the shale reservoir, m2/s; ηIIs the diffusion coefficient of the fracture-reformed region, m2/s;yeIs the crack half spacing, m; vpIs the dynamic drainage volume, m, of shale oil and gas production wells3
Macroscopic material balance model:
wherein, VnIs tnDynamic drainage volume m of fractured horizontal well of shale oil reservoir at moment3(ii) a The subscript i represents the original reservoir pressure piEach parameter value under the condition; subscript n represents the shale reservoir mean pressure pnConditioning each parameter value; phi is aiIs the average porosity, fraction, of the shale reservoir under initial conditions; c. CfShale oil reservoir rock compressibility factor, Pa-1;Bo,Bw,BgIs the volume coefficient of crude oil, formation water and gas of the shale oil reservoir, m3/m3;RvIs the condensate gas-oil ratio of shale reservoir, m3/m3;RsShale oil reservoir crude oil dissolved gas-oil ratio, m3/m3;Sw,So,SgIs the formation crude oil, water and gas saturations; n is a radical ofop,Nwp,NgpIs the cumulative oil production, water production and gas production of the shale oil well at different moments m3
According to the invention, a shale oil-gas well saturation degree calculation expression (1) is substituted into a material balance equation (3), production prediction and historical analysis are coupled into a whole, and an iterative algorithm is used for synchronous calling calculation, so that the integration of 'historical evaluation-scheme optimization-production prediction' is realized.
The method also considers that the permeability of the shale oil and gas reservoir nano-scale pores is extremely low, and the transient flow of the volume fracture horizontal well can penetrate through the whole production stage, so that the traditional leakage flow volume calculation method based on steady-state linear flow or radial flow is not applicable any more. The method establishes the shale oil-gas fracturing horizontal well linear flow model, deduces the formula of the dynamic leakage flow volume model (2) in the shale oil-gas production process which is accurately suitable for the volume fracturing horizontal well, combines the formula (2) and the formula (3), and can represent the contribution of the dynamic leakage flow volume change and the fracturing transformation range to the shale oil-gas production based on historical data.
Preferably, in the step (three), because the shale oil and gas production process has rapid pressure failure, obvious matrix shrinkage and crack closure and obvious influence of stronger compressibility of shale fluid on the shale oil and gas yield, the method is different from the traditional yield analysis parameter definition method, the pseudo pressure m (p) considering permeability time-varying property and fluid compressibility, namely the formula (4a), is introduced, and the pressure correction factor f is introducedcpI.e., (4b), improves the desired parameters in the yield analysis curve: yield normalized pseudo pressure (4c) equation and production material equilibrium time (4d) equation:
wherein m (p) is a pseudo pressure, Pa, introduced in consideration of time-varying permeability and compressibility of the fluid; m (RNP) is the shale reservoir pseudo pressure after yield normalization, Pa/(m)3/d);m(Pwf) Shale oil reservoir production bottom hole pressure pwfA corresponding pseudo pressure value, Pa; m (p)i) Initial pressure p of shale oil reservoiriA corresponding pseudo pressure value, Pa; k is a radical ofiThe matrix permeability mD under the condition of the average pressure p of the shale oil reservoir; k is a radical ofroIs the average pressure p and the average saturation S of the shale oil reservoiroRelative permeability of the oil phase under the condition, and fraction; b isoIs the volume coefficient of crude oil m under the condition of the average pressure p of a shale oil reservoir3/m3;μoThe method comprises the steps of (1) determining the viscosity of crude oil in Pa.s under the condition of shale oil reservoir average pressure p; f. ofcpIs a pressure correction factor, fraction, gammakIs the reservoir permeability modulus, Pa-1;cfIs a reservoir under the condition of average pressure p of a shale oil reservoirCoefficient of compression, Pa-1;cμIs a crude oil viscosity factor Pa under the condition of shale oil reservoir average pressure p-1;qo,scFor crude oil production at surface conditions, m3A day; n is a radical ofopIs the cumulative oil production m of the shale oil well at different times t3;tmaConsidering the substance balance time corresponding to different moments t after the influence of daily output change of the shale oil well is considered, and measuring the substance balance time;
plotting normalized pseudo-pressure m (RNP) and time tmaPerforming instantaneous yield Analysis (RNP), identifying the flowing stage of the shale fractured horizontal well according to different slopes of a fitted regression line, and calculating the fluid diffusion coefficient in the fractured and transformed region by using a formula (2) according to the ending time te of the early Transient linear flow (the slope is 1/2) and the known fracture spacing; then drawing square root time characteristic curve (5) to obtain its slope mL, then according to Wattenbarger (6) formula calculating effective crack half-length xfAnd carrying out production data descending analysis according to the modified Duong method, and determining the limit leakage flow volume and the final output degree.
Wherein m isLIs a transient yield analysis (m (RNP) vs. tma) The slope of the relationship; mu.soIs crude oil viscosity, pa.s; h isfIs the shale oil well fracture height, m; x is the number offIs the crack length, m; q. q.so,scIs the crude oil yield m under the surface condition of the shale oil well3A day; k is shale reservoir matrix permeability, mD; phi is shale reservoir porosity, fraction; c. CtIs the overall compression coefficient, Pa, of the shale oil reservoir-1
Preferably, in the step (III), the limit drainage volume V is determined first due to the calculation of the crude oil recovery factor in the formula (1)pmaxWhich can be obtained by modifying the formula of Duong method (7)(from Duong, 2010). The specific calculation procedure includes first determining coefficients a and m using equation (7a), and then plotting 7 to determine the initial production q based on equation (7b)1
Wherein q isoIs the daily oil production m of the shale oil well at different times t3A day; n is a radical ofopIs the cumulative oil production m of the shale oil well at different times t3;qo,1Is the initial oil production of the shale oil well, m3A day; and a and m are yield curve fitting coefficients.
Preferably, in the step (six), based on analysis, evaluation and prediction of shale oil and gas production data, in order to eliminate interference caused by length difference of horizontal sections of different production wells, a horizontal section is introduced to normalize the final production degree, namely the ratio of the RF to the length of the horizontal section, namely the final production degree of a unit horizontal section; determining the optimal fracture interval of the fractured horizontal well by normalizing the horizontal segment lengths of all target production wells and classifying and analyzing the final extraction degree and the fracture interval; and meanwhile, determining the optimal fractured horizontal well spacing by dividing the predicted ultimate drainage volume by the known horizontal section length.
The beneficial effect of the invention is that,
1. comprehensive 'historical evaluation-development optimization-yield prediction' integration
Different from the existing dynamic analysis method, the shale oil-gas well saturation degree calculation expression (1), namely a relational expression between fluid saturation degree-reservoir pressure-extraction degree, is introduced into the macroscopic material balance model (3) for the first time, and the integration of 'historical evaluation-scheme optimization-production prediction' is realized by using an iterative algorithm for synchronous adjustment and calculation. Wherein, the history evaluation part: drawing a production flow stage identification curve and a square root time characteristic curve; and a future prediction part: predicting the final recovery rate and the ultimate discharge volume of shale oil and gas by adopting a corrected Duong curve; and an optimization design part: and obtaining the optimal fracture spacing and the optimal fractured horizontal well spacing by summarizing and analyzing all production well evaluation results of the target block. The invention mutually calls the input and output results of each part of the evaluation-optimization-prediction process, and realizes the comprehensive dynamic analysis of shale oil and gas production.
2. Introducing a dynamic drainage volume concept to represent the cumulative contribution of the fracturing modification range to the shale oil production
The permeability of the nano-scale pores of the shale oil and gas reservoir is extremely low, and the volume fracturing horizontal well with complex fracture distribution causes transient flow to possibly penetrate through the whole production stage, so that the traditional leakage flow volume calculation method based on steady-state linear flow or radial flow is not applicable any more. According to the method, the shale oil-gas fracturing horizontal well linear flow model is established, the dynamic drainage volume model which is accurately suitable for the shale oil-gas production process of the volume fracturing horizontal well is deduced, and the contribution of the fracturing modification range and the peripheral non-modification range to the shale oil-gas production can be represented respectively.
3. Shale matrix shrinkage and fracture closure influence are coupled, and iterative algorithm accurately represents fracture parameters
In order to consider the influences of matrix shrinkage and obvious fracture closure caused by fast pressure failure in the shale oil-gas production process and stronger compressibility of shale fluid on the shale oil-gas yield, the invention defines the simulated pressure introduced by considering permeability time-varying property and fluid compressibility, introduces the pressure correction primer, improves the yield normalization simulated pressure and the production material balance time in the shale oil yield analysis curve, and can obtain more accurate effective fracture length of the shale oil volume fracturing horizontal well.
4. Based on historical data analysis, shale oil and gas well arrangement and fracturing optimization are synchronously realized, and yield prediction is realized
Because the limit leakage flow volume is obtained firstly when calculating the shale oil dynamic production degree, and the limit leakage flow volume is obtained by predicting through yield decrement analysis. Therefore, the method couples shale oil and gas historical production data analysis with future production prediction by introducing an iterative algorithm. By adopting a modified Duong method, the final recovery rate and the ultimate drainage volume of shale oil and gas are predicted, then the final recovery rate and the ultimate drainage volume are substituted into a dynamic drainage volume model in the shale oil and gas production process to carry out yield dynamic analysis and cyclic iteration, the accurate ultimate drainage volume and the recovery degree are finally obtained, the shale oil and gas yield dynamic analysis and evaluation accuracy is improved, and technical support is provided for optimizing and developing shale oil and gas.
Drawings
FIG. 1 is a detailed flow chart of shale oil reservoir production data evaluation-optimization design-future prediction comprehensive analysis according to the invention;
FIG. 2 is a graph of results from determining different flow stages of a shale oil volume fractured horizontal well of a real block using RNP curve analysis according to an embodiment of the present invention;
FIG. 3 is a flow chart of decreasing analysis and prediction of a shale oil volume fractured horizontal well of a real block by using a modified Duong method according to an embodiment of the invention
FIG. 4 is a graph illustrating the contribution of the unmodified area and the fracture modified area of a shale oil volume fractured horizontal well of a certain practical block to the production of the horizontal well according to the embodiment of the invention;
FIG. 5 is a graph of the outcome of determining the optimal fracture spacing for a classification analysis of a real block of shale oil target production wells according to an embodiment of the present invention;
FIG. 6 is a schematic of the trilinear flow of a shale reservoir volume fractured horizontal well of the present invention;
FIG. 7 is a graph of the results of comparison of the dynamic drainage volume calculation analysis model and the CMG calculation results under the constant shale oil well production borehole bottom flow pressure according to the present invention;
FIG. 8 is a graph of a comparison result between a dynamic drainage volume calculation analysis model and a CMG calculation result under a constant shale oil well production speed condition according to the present invention;
FIG. 9 is a schematic diagram of a dynamic drainage volume change process during a long-term transient flow of a shale oil fractured horizontal well according to the present invention.
Detailed Description
The present invention will be further described with reference to the following examples.
A shale oil and gas comprehensive yield analysis method based on a dynamic leakage flow volume comprises the following steps:
(I): preparing data arrangement; the required data includes: shale reservoir petrophysical properties, fluid physical properties, well parameters, and production history of the target well;
the shale reservoir rock physical properties comprise compressibility, shale permeability and oil gas desorption parameters, the fluid physical properties comprise viscosity, volume coefficient and fluid compressibility, the well parameters comprise drilling and fracturing completion parameters, and the production history of the target well comprises oil gas water daily yield and cumulative yield.
Taking an example reservoir of Niobrara shale oil in the United states as an example, the data is collated as shown in Table 1.
TABLE 1 Niobrara shale oil reservoir and fluid parameters for a certain example of U.S.A
(II): initially estimating the limit leakage flow volume and the effective fracture half-length, respectively substituting into a shale oil-gas well saturation calculation expression (1) and a dynamic leakage flow volume calculation expression (2) suitable for a volume fracture horizontal well in a shale oil-gas production process, then substituting the calculation expressions and the production history of the target well into a macroscopic material balance model (3), calculating and determining the dynamic leakage flow volume of the shale oil well and the average reservoir pressure change in the production process according to the production history of the shale oil-gas well, and determining a pressure correction factor (4b) formula.
A shale oil-gas well saturation calculation expression:
wherein, subscript n represents parameter values at different production moments; subscript i represents the values of the parameters at the initial reservoir conditions; RF is shale oil production degree and fraction at different production moments; b isoiIs the initial reservoir pressure piVolume coefficient of shale oil of m3/m3;BtiIs the initial reservoir pressure piShale oil reservoirVolume coefficient of fluid, m3/m3;SwiThe original water saturation and fraction of the shale oil reservoir; vp(n)Is tnDynamic drainage volume m of shale oil well at any moment3;BoIs the average pressure condition of the reservoirLower crude oil volume coefficient, m3/m3;Sw(n),So(n),Sg(n)At a dynamic discharge volume Vp(n)Formation crude oil, water and gas saturations in; vp,maxUltimate discharge volume, m3;Bt(n)Is tnFluid volume coefficient, m, of shale reservoir at that moment3/m3;ct(n)Is tnIntegral compression coefficient, Pa, of shale reservoir at time-1;Vp,maxIs the ultimate drainage volume, m, of a shale oil and gas production well3
The dynamic drainage volume calculation expression is applicable to the shale oil and gas production process of the volume fracturing horizontal well:
a. and (3) keeping the shale gas well production bottom flow pressure constant:
wherein x isfIs the effective fracture half-length of the shale well; t is the different production times of the fractured horizontal well, day; t is teThe time of the completion of the early linear flow of the shale fractured horizontal well, i.e., the time of the completion of the early linear flow of the shale fractured horizontal well, h is the thickness of a shale reservoir, m, ηoIs the diffusion coefficient of the peripheral unmodified area of the shale reservoir, m2/s;ηIIs the diffusion coefficient of the fracture-reformed region, m2/s;yeIs the crack half spacing, m; vpIs the dynamic drainage volume, m, of the shale oil and gas well3
Macroscopic material balance model:
wherein, VnIs tnDynamic drainage volume m of fractured horizontal well of shale oil reservoir at moment3(ii) a The subscript i represents the original reservoir pressure piEach parameter value under the condition; subscript n represents the shale reservoir mean pressure pnConditioning each parameter value; phi is aiIs the average porosity, fraction, of the shale reservoir under initial conditions; c. CfShale oil reservoir rock compressibility factor, Pa-1;Bo,Bw,BgIs the volume coefficient of crude oil, formation water and gas of the shale oil reservoir, m3/m3;RvIs the condensate gas-oil ratio of shale reservoir, m3/m3;RsShale oil reservoir crude oil dissolved gas-oil ratio, m3/m3;Sw,So,SgIs the formation crude oil, water and gas saturations; n is a radical ofop,Nwp,NgpIs the cumulative oil production, water production and gas production of the shale oil well at different moments m3
(III): and (3) drawing a yield normalized simulated pressure and production time relation curve, as shown in figure 2, identifying the flow stage of the shale fractured horizontal well according to different slope sizes of the fitted regression line, and according to the ending time t of the early transient linear flow (the slope is 1/2)eAnd knowing the crack spacing, and calculating the fluid diffusion coefficient in the fracture transformation area by using the formula (2); then, the square root time characteristic curve (5) is drawn to obtain the slope mLThen, according to the formula of Wattenbarger (6), the effective half-length of the crack is calculated, and the production data is subjected to descending analysis according to the modified Duong method, as shown in figure 3(c), so as to determine the ultimate leakage flow volume and the final output degree. Different from the definition method of parameters used by the traditional oil deposit yield analysis method, due to the fast pressure failure, obvious matrix shrinkage and crack closure in the shale oil and gas production process and the influence of stronger compressibility of shale fluid on the shale oil and gas yield, pseudo pressure m (p) considering permeability time-varying property and fluid compressibility is introduced, as shown in formula (4a), and a pressure correction factor f is introducedcpI.e. (4b)) Formula (xxxvii), parameters required in improving RNP yield analysis curves: yield normalized pseudo pressure (4c) equation and production material equilibrium time (4d) equation:
wherein m (p) is a pseudo pressure, Pa, introduced in consideration of time-varying permeability and compressibility of the fluid; m (RNP) is the shale reservoir pseudo pressure after yield normalization, Pa/(m)3/d);m(Pwf) Shale oil reservoir production bottom hole pressure pwfA corresponding pseudo pressure value, Pa; m (p)i) Initial pressure p of shale oil reservoiriA corresponding pseudo pressure value, Pa; k is a radical ofiThe matrix permeability mD under the condition of the average pressure p of the shale oil reservoir; k is a radical ofroIs the average pressure p and the average saturation S of the shale oil reservoiroRelative permeability of the oil phase under the condition, and fraction; b isoIs the volume coefficient m of crude oil under the condition of average pressure p of shale oil reservoir3/m3;μoThe method comprises the steps of (1) determining the viscosity of crude oil in Pa.s under the condition of shale oil reservoir average pressure p; f. ofcpIs a pressure correction factor, fraction, gammakIs the reservoir permeability modulus, Pa-1;cfIs the reservoir compression coefficient Pa under the condition of the average pressure p of the shale oil reservoir-1;cμIs a crude oil viscosity factor Pa under the condition of shale oil reservoir average pressure p-1;qo,scIs the crude oil yield under surface conditions, m3A day; n is a radical ofopIs the cumulative oil production m of the shale oil well at different times t3;tmaConsidering the substance balance time corresponding to different moments t after the influence of daily output change of the shale oil well is considered, and measuring the substance balance time;
drawing a relation curve of yield normalized simulated pressure and production time, performing instantaneous yield Analysis (Rate-Transient Analysis, RNP), identifying the flowing stage of the shale fractured horizontal well according to different slopes of a fitted regression line, identifying the flowing stage of the shale fractured horizontal well according to different slopes of the fitted regression line, and calculating a fluid diffusion coefficient in a fracturing modification area (SRV) by using a formula (2) according to the ending time te of early Transient linear flow (the slope is 1/2) and the known fracture interval; then theDrawing square root time characteristic curve (5) to obtain its slope mLThen, according to the formula of Wattenbarger (6), calculating the effective half-length x of the crackfAnd carrying out production data descending analysis according to the modified Duong method to determine the limit leakage flow volume and the final output degree.
Wherein m isLIs a transient yield analysis (m (RNP) vs. tma) The slope of the relationship; mu.soIs crude oil viscosity, pa.s; h isfIs the shale oil well fracture height, m; x is the number offIs the effective fracture length of the shale production well, m; q. q.so,scIs the crude oil yield m under the surface condition of the shale oil well3A day; k is shale reservoir matrix permeability, mD; phi is shale reservoir porosity, fraction; c. CtIs the comprehensive compression coefficient, Pa, of shale oil reservoir-1
Since the calculation of the crude oil recovery in equation (1) requires first determining the ultimate drainage volume VpmaxIt can be determined by modifying the Duong method (7) equation, (from Duong, 2010). The specific calculation process comprises the steps of firstly determining coefficients a and m by using the formula (7a), fitting production data to obtain values of parameters a and m as shown in the figure 3(a), and then drawing and determining an initial yield q according to the formula (7b)1Fitting the production data acquisition parameters q as in FIG. 3(b)1,。
Wherein q iso(n)Is the daily oil production m of the shale oil well at different times t3A day; n is a radical ofop(n)Is the cumulative oil production m at different times t of the shale oil well3;qo1Is the initial oil production of the shale oil well, m3A day; and a and m are yield curve fitting coefficients.
(IV): and (3) if the difference between the effective crack half length and the limit leakage volume calculated in the step (III) and the input value in the step (II) is larger, substituting the value calculated in the step (III) into the step (II), repeating the step (II) and the step (III) in sequence until the input value in the step (II) is consistent with the convergence of the effective crack half length and the limit leakage volume calculated in the step (III), stopping calculation, and obtaining the accurate effective crack half length and the limit leakage volume.
(V): according to the formulas shown in fig. 6 and (2), the shale oil and gas flow area comprises two parts: a fracture engineered zone and an unmodified matrix zone. Substituting the formula (2) into a macroscopic material balance model (4), and comparing to obtain the cumulative contribution of the size of the fracturing modification area to the shale oil and gas production. As shown in fig. 4, in a certain practical shale oil calculation example, the contribution of the unmodified area to the 1000-day cumulative yield of the volume horizontal well is not more than 5%, that is, the size of the range of the practical fracture modified area basically determines most of the yield of the volume fracture horizontal well.
(VI): by integrating the production data evaluation and prediction results of all shale wells, as shown in table 2, in order to eliminate the interference caused by the length difference of the horizontal sections of different production wells, the horizontal section is introduced to normalize the final extraction degree (the ratio of the RF to the length of the horizontal section, i.e., the final extraction degree of the unit horizontal section). By normalizing the horizontal segment lengths of all target production wells to obtain the final extraction degree and the fracture spacing, classification analysis can be carried out, and the optimal fracture spacing of the fractured horizontal well can be determined to be about 20m, as shown in fig. 5. And then dividing the predicted ultimate drainage volume by the known horizontal segment length and the reservoir height of 15m to obtain the optimal fractured horizontal well spacing of about 180-270m by estimation.
TABLE 2. Niobrara shale oil certain practical block volume fracturing horizontal well production history evaluation and prediction result summarization
The invention relates to a determination of a dynamic leakage flow volume calculation expression in the shale oil and gas production process applicable to a volume fracture horizontal well:
the model derivation hypothesis is that ① shale oil reservoir outer boundary is closed, a homogeneous box shape is formed, physical properties do not change along with time, a single infinite large-flow-conductivity vertical fracture is fractured on a horizontal well section, a ② finite-flow-conductivity vertical artificial fracture completely penetrates through the reservoir, the fracture height is equal to the oil reservoir thickness, ③ reservoir fluid can only flow into a borehole from a fracture of a perforation section, pressure loss of the ④ horizontal well section is ignored, ⑤ hydraulic support fractures are symmetric double-wing fractures, are perpendicular to a horizontal shaft, fracture interference is considered, no-flow boundaries exist among fractures, and the model deduced by ⑥ is suitable for single-phase fluid flow.
As shown in fig. 6, the subscript "O" represents the fracture horizontal well peripheral unmodified zone, "I" represents the fracture modified zone, and "f" represents the fracture modified primary fracture. To facilitate the derivation of the formula for calculating the leakage area, the following dimensionless variables are defined:
dimensionless pressure:
dimensionless time:
dimensionless distance:
in the shale fracturing modified area and the peripheral non-modified area, the fluid flow diffusion coefficient is as follows:
the fluid in the shale oil reservoir has dimensionless flow capacity:
wherein k isI,kORespectively the permeability, mD, of a shale oil reservoir fracturing modification area and a peripheral non-modification area; h is shale reservoir height, m; q is the daily yield of crude oil from shale reservoir, m3A day; c. CtComprehensive compression coefficient, Pa, of shale oil reservoir-1;piIs the original reservoir pressure, Pa; x is the number offShale oil reservoir fracturing horizontal well fracture length m ηoIs the diffusion coefficient of the peripheral unmodified area of the shale reservoir, m2/s;ηIIs the diffusion coefficient of the fracture-reformed region, m2/s;yeIs the crack half spacing, m.
From the above model assumptions, the following set of seepage equations can be written for FIG. 6:
in the peripheral fracture non-modified area, the shale reservoir fluid flows into the internal fracture modified area linearly, the flow equation is as follows,
through Laplace transformation and combining boundary conditions, a mathematical model can be obtained:
the solution of the equation is that,
similar to the above, the mathematical model of seepage in the Laplace space of the internal fracture transformation area is listed as,
wherein the content of the first and second substances,
1. under the production condition of fixed bottom hole flowing pressure:
based on the above assumptions, only after the fluid flow pressure boundary in the fracture reformation region reaches the no-flow boundary between the primary fractures, i.e., time teDThe flow is started only in the outer unmodified range, while the bottom hole flow pressure is determined according to the obtained conditions of (Behmanesh et al, 2015) at teDAt the moment, the pressure distribution in the fracture transformation range is,
at this time, the pressure conditions at the non-flowing boundary between fractures and along the periphery of the main fracture are,
p=pwf→pD=1,atyD=0 (20)
combining the expressions (19) to (20) of the boundary conditions and the expression (18) of the initial condition, the solution of the expression of the nonhomogeneous partial differential equation (14) is,
wherein the content of the first and second substances,
b0=b2=0
C2=1-b0-C1
then, according to the equation (15), the pressure distribution in the outer unmodified region is,
2. under the condition of definite production yield
Similarly, the solution obtained according to (Behmanesh et al, 2015) at teDAt the moment, the pressure distribution in the fracture transformation range is,
the pressure conditions at the non-flowing boundaries between fractures and along the main fracture perimeter are,
at yD=0,tD>0 (24)
At yD=yeD,tD>0 (25)
Combining the expressions (24) to (25) of the boundary conditions and the expression (23) of the initial condition, the solution of the expression of the nonhomogeneous partial differential equation (14) is,
wherein the content of the first and second substances,
b3=b5=0
according to equation (15), the pressure distribution of the dynamic drainage volume of the outer unmodified region is expressed as,
3. determining the dynamic drainage volume of the volume fractured horizontal well:
according to fig. 6, the change of the leakage flow area in the shale oil and gas production process can be divided into two processes: in a fracturing modification area, the drainage area is continuously increased along the direction (y direction) vertical to the main crack until a non-flowing boundary in the middle of the crack is reached; then, the fluid in the peripheral non-modified area starts to flow into the fracture modified area along the x direction, and the drainage area starts to continuously expand and increase along the x direction. Thus, the blow-off volume of a volume fractured horizontal well may be expressed as:
Vpfracture transformation range + outer unmodified zone dynamic drainage volume (28)
According to the method for calculating the maximum reaction speed of the pressure wave adopted by the leakage flow boundary by Kuchuk (2009), the invention also determines the dynamic leakage flow volume expansion speed by calculating the leakage flow volume at the moment when the dimensionless pressure and the time second derivative are equal to zero, and the method comprises the following steps:
in consideration of the complexity of the quadratic derivation calculation of the expressions (22) and (27), it is difficult to directly obtain an analytical expression. Therefore, the invention adopts a multivariate regression analysis method to obtain a calculation method of the dynamic leakage flow volume by fitting.
a. Constant shale oil well production borehole bottom flow pressure:
wherein x isfIs the effective fracture half-length of the shale fractured horizontal well; t is the different production times of the fractured horizontal well, day; t is teIs the time of the end of the early linear flow of the fractured horizontal well, h is the shale reservoir thickness, m, ηoIs the diffusion coefficient of the peripheral unmodified area of the shale reservoir, m2/s;ηIIs the diffusion coefficient of the fracture-reformed region, m2/s;yeIs the crack half spacing, m; vpIs the dynamic drainage volume of the shale oil and gas production well, m3
In order to verify the accuracy of the formula (2) of the dynamic leakage flow volume calculation, a volume fracturing horizontal well calculation example is set by using a commercial numerical simulator CMG black oil model. As shown in fig. 7 and 8, the dynamic leakage flow volume obtained by the formula (2) calculation has good fitting consistency with the CMG calculation result, which shows that the dynamic leakage flow volume calculation expression newly derived in the shale oil and gas production process applicable to the volume fractured horizontal well is accurate enough.
A macroscopic material balance model for a volume fractured horizontal well based on dynamic drainage volume:
in the shale oil and gas production process, the dynamic drainage volume of the volume fracturing horizontal well changes, as shown in fig. 9, at the production time tnVolume of the relief volume of the volume fractured horizontal well is VnAt the next production time tn+1Dynamic drainage volume increase to Vn+1And the change of reservoir fracturing and fluid saturation in the dynamic process can be represented by using a macroscopic material balance relation.
In the shale oil and gas well production process, the material balance equation of the formation water is as follows:
wherein the content of the first and second substances,is tnAt time of dynamic drainage volume V(n)The amount of formation water inventory within,is tn+1-tnThe volume of formation water increases over a period of time due to the expansion of the blow-off volume,time dynamic discharge volume V(n+1)The amount of formation water therein. To the right of the equation at tn+1-tnCumulative water production from the well over the time period.
In the shale oil-gas well production process, the material balance equation of shale oil is as follows:
wherein the content of the first and second substances,is tnAt time of dynamic drainage volume V(n)The inventory of crude oil in the formation within,is tn+1Time dynamic discharge volume V(n+1)The reservoir of formation oil in the right side of the equation is at tn+1-tnCumulative oil production from the well over the time period. If the shale reservoir is not a condensate reservoir, the condensate oil content in the equation can be ignored
In the shale oil-gas well production process, the material balance equation of shale gas is as follows:
wherein the content of the first and second substances,represents the amount of dissolved gas released from the crude oil as the reservoir pressure drops, which is zero if the reservoir pressure is above the crude oil saturation pressure.
Adding and summing the material balance relation equations of oil, gas and water to obtain a macroscopic material balance equation in the shale oil-gas production process:
wherein, VnIs tnDynamic drainage volume m of fractured horizontal well of shale oil reservoir at moment3(ii) a The subscript i represents the original reservoir pressure piEach parameter value under the condition; subscript n represents the shale reservoir mean pressure pnConditioning each parameter value; phi is aiIs the average porosity, fraction, of the shale reservoir under initial conditions; c. CfShale oil reservoir rock compressibility factor, Pa-1;Bo,Bw,BgIs the volume coefficient of crude oil, formation water and gas of the shale oil reservoir, m3/m3;RvIs the condensate gas-oil ratio of shale reservoir, m3/m3;RsShale oil reservoir crude oil dissolved gas-oil ratio, m3/m3;Sw,So,SgIs the formation crude oil, water and gas saturations; n is a radical ofop,Nwp,NgpIs the cumulative oil production, water production and gas production of the shale oil well at different moments m3
In the production process of shale oil gas, the production data of crude oil, water and gas, the change of the dynamic drainage volume of the shale oil gas well can be obtained by calculating according to the formula (30) and substituted into the formula (34), and the formula is combined with Sw+SO+SgThe average formation pressure of the shale reservoir and the corresponding crude oil, gas and formation water saturations can be found as 1. In addition, according to the definition of the extent of production of a generic reservoir (Craft et al, 1991), the extent of dynamic production of shale reservoirs can be characterized as:
the shale oil reservoir extraction degree calculation comprises two parts: crude oil production efficiency and drainage volume sweep efficiency. Different from general oil reservoirs, the method introduces the drainage volume sweep efficiency, namely the ratio of the dynamic drainage volume to the limit drainage volume, and quantifies the long-term transient flow influence of the shale oil well. Wherein the limiting leakage volume is determined by a yield-decreasing analysis method. Meanwhile, the oil reservoir crude oil, formation water and gas saturation can be linked with the shale oil reservoir dynamic production degree by using the formula (36), as follows:
finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims (5)

1. A shale oil gas comprehensive yield analysis method based on dynamic leakage flow volume is characterized by comprising the following steps:
firstly, preparing data arrangement; the data includes: shale reservoir petrophysical properties including compressibility, shale permeability and hydrocarbon desorption parameters, fluid physical properties including viscosity, volume coefficient and fluid compressibility, well parameters including drilling and fracturing completion parameters, and production history of a target well including oil, gas and water daily yield and cumulative yield;
initially estimating the limit drainage volume and the effective fracture half-length to obtain a shale oil-gas well saturation and dynamic drainage volume calculation expression, substituting the calculation expression and the production history of the target well into a macroscopic material balance model, and calculating the dynamic drainage volume, the reservoir average pressure change and a pressure correction factor in the production process;
drawing a relation curve of the yield normalized simulated pressure and time, identifying the flowing stage of the shale fractured horizontal well, and calculating the fluid diffusion coefficient in the fractured modified area according to the ending time of the early transient linear flow and the known fracture interval; then drawing a square root time characteristic curve to obtain the slope of the square root time characteristic curve, and calculating the effective crack half-length; and carrying out production data decreasing analysis according to the modified Duong method, and determining the limit leakage flow volume and the final output degree;
if the difference between the effective crack half length and the limit leakage volume calculated in the step three and the input value in the step two is large, the value calculated in the step three needs to be substituted into the step two again, the step two and the step three are repeated in sequence until the effective crack half length and the limit leakage volume calculated in the step two are converged and consistent, the calculation is stopped, and the accurate effective crack half length and the accurate limit leakage volume are obtained;
fifthly, the shale oil and gas flow area comprises two parts: a fracture engineered zone and an unmodified matrix zone; substituting a dynamic leakage flow volume calculation expression in the shale oil and gas production process suitable for the volume fracturing horizontal well into a macroscopic material balance model, and comparing to obtain the cumulative contribution of a fracturing modification area and an unmodified matrix area to shale oil and gas production respectively;
and sixthly, performing optimization determination on fracture parameters and well spacing of the shale oil and gas fracturing horizontal well based on analysis, evaluation and prediction of shale oil and gas production data.
2. The shale oil and gas comprehensive yield analysis method based on the dynamic leakage flow volume as claimed in claim 1, wherein in the second step, firstly, the limit leakage flow volume and the effective fracture half-length are initially estimated to obtain a shale oil and gas well saturation degree calculation expression (1) and a dynamic leakage flow volume calculation expression (2) in the shale oil and gas production process suitable for the volume fracture horizontal well, then the shale oil and gas saturation degree calculation expression and the shale oil and gas production process suitable for the volume fracture horizontal well are substituted into a macroscopic material balance model (3), and the dynamic leakage flow volume, the reservoir average pressure change and the pressure correction factor in the production process are calculated according to the production history of the shale oil and gas well;
a shale oil-gas well saturation calculation expression:
wherein, subscript n represents parameter values at different production moments; subscript i represents the values of the parameters at the initial reservoir conditions; RF (radio frequency)(n)Shale oil extraction degrees and fractions at different production moments; b isoiIs the initial reservoir pressure piVolume coefficient of shale oil of m3/m3;BtiIs the initial reservoir pressure piFluid volume coefficient of shale oil reservoir, m3/m3;SwiThe original water saturation and fraction of the shale oil reservoir; vp(n)Is production of tnDynamic drainage volume m of shale oil well at any moment3;BoIs the reservoir mean pressure condition PnLower crude oil volume coefficient, m3/m3;Sw(n),So(n),Sg(n)At a dynamic discharge volume Vp(n)Formation crude oil, water and gas saturations in; b ist(n)Is tnFluid volume coefficient, m, of shale reservoir at that moment3/m3;ct(n)Is tnIntegral compression coefficient, Pa, of shale oil reservoir at any moment-1;Vp,maxIs the ultimate drainage volume, m, of the shale production well3,Bo(n) is the shale reservoir mean pressure pnVolume coefficient of shale reservoir crude oil, m3/m3
Shale suitable for volume fracturing horizontal well; the dynamic leakage flow volume calculation expression in the oil and gas production process is as follows:
a. and (3) keeping the shale gas well production bottom flow pressure constant:
wherein x isfIs the effective fracture half-length, m, of the shale fractured horizontal well; t is the different production times of the fractured horizontal well, day; t is teIs the time of the end of the early linear flow of the fractured horizontal well, h is the shale reservoir thickness, m, ηoIs the diffusion coefficient of the peripheral unmodified area of the shale reservoir, m2/s;ηIIs the diffusion coefficient of the fracture-reformed region, m2/s;yeIs the crack half spacing, m; vpIs the dynamic drainage volume, m, of a shale oil and gas production well3
Macroscopic material balance model:
wherein, V(n)Is tnDynamic drainage volume m of fractured horizontal well of shale oil reservoir at moment3;φ(i)Is the average porosity, fraction, of the shale reservoir under initial conditions; c. C(f)Shale oil reservoir rock compressibility factor, Pa-1;PnNamely the average pressure of the oil reservoir, Pa; piTo the original reservoir pressureForce, Pa;the formation crude oil saturation under the average pressure of the shale oil reservoir;is the volume coefficient of formation water, m, at the average pressure of the reservoir3/m3Gas saturation under the average pressure of the shale oil reservoir;is the volume coefficient of gas, m, at the average pressure of the reservoir3/m3;Rv(n)Is the condensate oil-gas ratio, m, of the shale oil-gas reservoir under the average pressure of the shale oil reservoir3/m3Water saturation under the average pressure of the shale oil reservoir;is the volume coefficient m of the crude oil of the shale oil reservoir under the average pressure of the shale oil reservoir3/m3;Rs(n)The shale oil reservoir crude oil dissolution gas-oil ratio m under the average pressure of the shale oil reservoir3/m3;Sw(i)The formation crude oil saturation under the original reservoir pressure of the shale; b isw(i)Is the volume coefficient of formation water, m, at the original reservoir pressure3/m3;So(i)Water saturation at original reservoir pressure; b iso(i)Is the volume coefficient of shale oil reservoir crude oil under the original reservoir pressure, m3/m3;Rs(i)Is the shale oil reservoir crude oil dissolution gas-oil ratio m under the original oil reservoir pressure3/m3;Sg(i)Gas saturation at the original reservoir pressure; b isg(i)Is the volume factor of the gas at the original reservoir pressure,m3/m3;Rv(i)is the condensate gas-oil ratio, m, of the shale oil-gas reservoir at the original reservoir pressure3/m3;Nwp(n)The cumulative water yield m of the shale oil well at different moments under the average pressure of the shale oil reservoir3;Nop(n)The cumulative oil production m of the shale oil well at different moments under the average pressure of the shale oil reservoir3;Ngp(n)The cumulative oil production m of the shale oil well at different moments under the average pressure of the shale oil reservoir3
3. The method for analyzing shale oil and gas comprehensive yield based on dynamic drainage volume as claimed in claim 2, wherein in the third step, because the shale oil and gas production process has rapid pressure failure, obvious matrix shrinkage and crack closure, and strong compressibility of shale fluid has obvious influence on shale oil and gas yield, the method is different from the traditional yield analysis parameter definition method, the method introduces pseudo pressure m (p) considering permeability time-varying property and fluid compressibility, namely formula (4a), and introduces a pressure correction factor fcpI.e., (4b), improves the desired parameters in the yield analysis curve: yield normalized pseudo pressure (4c) equation and production material equilibrium time (4d) equation:
wherein m (p) is a pseudo pressure, Pa, introduced in consideration of time-varying permeability and compressibility of the fluid; m (RNP) is the shale reservoir pseudo pressure after yield normalization, Pa/(m)3/d);m(Pwf) Shale oil reservoir production bottom hole pressure pwfA corresponding pseudo pressure value, Pa; m (p)i) Initial pressure p of shale oil reservoiriA corresponding pseudo pressure value, Pa; k is a radical ofiThe matrix permeability mD under the average pressure condition of the shale oil reservoir; k is a radical ofroIs the average pressure and average saturation S of shale oil reservoiroRelative permeability of the oil phase under the condition, and fraction; b isoIs the volume coefficient m of crude oil under the average pressure condition of the shale oil reservoir3/m3;μoThe viscosity of crude oil is Pa.s under the condition of average pressure of the shale oil reservoir; f. ofcpIs pressureForce correction factor, fraction, gammakIs the reservoir permeability modulus, Pa-1;cfIs the reservoir compression coefficient Pa of the shale oil reservoir under the condition of average pressure-1;cμIs a crude oil viscosity factor Pa under the condition of average pressure of shale oil reservoir-1;qo,scFor crude oil production at surface conditions, m3A day; n is a radical ofopIs the cumulative oil production m of the shale oil well at different times t3;tmaConsidering the influence of daily output change of the shale oil well, the material balance time, day and mu corresponding to different moments toiIs the crude oil viscosity, Pa.s, under the original reservoir pressure condition; b isoiMeans volume coefficient of shale reservoir crude oil under original reservoir pressure condition, m3/m3
Plotting normalized pseudo-pressure m (RNP) and time tmaPerforming instantaneous yield Analysis (Rate-Transient Analysis, namely RNP), identifying the flow stage of the shale fractured horizontal well according to different slopes of a fitted regression line, and calculating the fluid diffusion coefficient in the fractured reconstruction region by using a formula (2) according to early Transient linear flow, namely the end time te with the slope of 1/2 and the known fracture spacing; then drawing square root time characteristic curve (5) to obtain its slope mL, then according to Wattenbarger (6) formula calculating effective crack half-length xfCarrying out production data decreasing analysis according to a modified Duong method, and determining the limit leakage flow volume and the final output degree;
where the index i represents the value of each parameter under the original reservoir pressure conditions, mLIs the slope of the instantaneous yield analysis relationship curve; mu.soIs crude oil viscosity, pa.s; h isfIs the shale oil well fracture height, m; x is the number offIs the crack length, m; q. q.so,scIs the crude oil yield under the surface condition of the shale oil well,m3A day; k is shale reservoir matrix permeability, mD; phi is shale reservoir porosity, fraction; c. CtIs the overall compression coefficient, Pa, of the shale oil reservoir-1
4. The method for analyzing shale oil and gas comprehensive yield based on dynamic drainage volume as claimed in claim 3, wherein in the third step, the limit drainage volume V is determined first due to the calculation of the crude oil recovery factor in the formula (1)pmaxIt can be determined by modifying the Duong method (7) by a calculation process comprising first determining the coefficients a and m using equation (7a) and then plotting and determining the initial yield q according to equation (7b)o,1
Wherein q isoIs the daily oil production m of the shale oil well at different times t3A day; n is a radical ofopIs the cumulative oil production m of the shale oil well at different times t3;qo,1Is the initial oil production of the shale oil well, m3A day; and a and m are yield curve fitting coefficients.
5. The method according to claim 1, wherein in the sixth step, based on analysis, evaluation and prediction of shale oil and gas production data, in order to eliminate interference caused by length difference of horizontal sections of different production wells, a horizontal section is introduced to normalize the final extraction degree, i.e. the ratio of the RF to the length of the horizontal section, i.e. the ratio of the shale oil extraction degree to the length of the horizontal section at different production moments, and the fraction is the final extraction degree of the unit horizontal section; determining the optimal fractured horizontal well fracture interval by normalizing the horizontal segment lengths of all target production wells to obtain the final extraction degree and the fracture interval in a classification analysis manner; and meanwhile, determining the optimal fractured horizontal well spacing by dividing the predicted ultimate drainage volume by the known horizontal segment length.
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