CN104847341A - Correction method for reasonable productivity prediction of underground gas storage well - Google Patents

Abstract

The invention relates to a correction method for reasonable productivity prediction of an underground gas storage well. The method comprises the following steps that a gas well binomial productivity equation (inflow curves) represents the supply capacity of a stratum; the flowing capacity of an oil pipe under the condition of limited pipe diameter of the oil pipe is determined through the oil pipe flowing capacity (outflow curve); the maximum flowing capacity of a gas well under the condition of the oil pipe can be obtained through combined intersections of the curves; for the production capacity of the gas well, limits to reasonable production pressure differences also shall be taken into consideration besides the capacity of the intersections of the inflow curves and the outflow curve. According to the invention, the intersections of the inflow curves and the outflow curve are corrected through establishing reasonable production pressure differences of the gas well, and the reasonable productivity of the gas well is obtained after correction. The method is simple in calculation, conforms to the actual situation, and can further guide the design of the gas storage effectively.

Description

Underground natural gas storage tank well rational productivity forecast value revision method

Technical field

The present invention relates to the technical field of gas field development, more particularly, the present invention relates to a kind of underground natural gas storage tank well rational productivity forecast value revision method.

Background technology

The capability forecasting of the natural gas well is a kind of technology of reservoir produce oil gas ability being carried out to overall merit, it has extremely important meaning to the exploration and development in gas field, it is not only the key link improving exploration and development benefit, and can provide important scientific basis for development plan deployment with planning.

The method of current capability forecasting mainly contains three kinds: the first utilizes storage parameter and actual production capacity to carry out simulation and sets up forecast model; It two is store disaggregated model according to neural network, thus carries out capability forecasting.But the Forecasting Methodology of prior art, in the different phase of gas well exploitation, needs repeatedly fully productivity test.Although prior art considers the fluid ability of stratum and oil pipe in the design, mining site actual conditions not being considered, as shaked out, water outlet and the situation such as hypotonic, thus the irrational problem of producing pressure differential can be caused.

Summary of the invention

In order to solve the above-mentioned technical problem existed in prior art, the object of the present invention is to provide a kind of underground natural gas storage tank well rational productivity forecast value revision method.

To achieve these goals, present invention employs following technical scheme:

A kind of underground natural gas storage tank well rational productivity forecast value revision method, is characterized in that comprising the following steps:

1a according to Gas well test data determination gas well deliverability, deliverability equation when pseudostable flow moves that the gas well of state is anhydrous to be produced, and obtain flowing into curve;

1b obtains elution curve according to gas well straight tube flow equation;

Form the curve that crosses together with inflow curve is plotted in elution curve by 1c, the joint flowing into curve and elution curve obtains the gas well deliverability of gas well under gas well straight tube condition;

Wherein, for sandstone air reservoir utilize local area the to shake out pressure reduction that shakes out that experimental result draws, during gas well liquid loading, producing pressure differential should lower than the pressure reduction that shakes out; For the air reservoir that there is Bian Shui, end water intrusion effect, produce the restriction of water limit pressure difference according to gas well and determine Gas well dewatering pressure reduction, producing pressure differential should lower than Gas well dewatering pressure reduction; For without shake out and the gas well liquid loading pressure reduction of influence on water body lower than 2 times of Relationship with Yield flex point pressure reduction; And according to this producing pressure differential correction gas well deliverability.

Specifically, for sandstone reservoirs, the critical pressure reduction that shakes out of gas well by the spontaneous potential curve in well-log information and stratum interval transit time, in conjunction with the rock mechanics parameters that formation density log obtains, can obtain the critical pressure reduction formula that shakes out of gas reservoir.

${\mathrm{\ΔP}}_{\max }=P_p-\frac{0.5v}{1-v}{P}_o+\frac{1-1.5v}{1-v}\mathrm{\α}{P}_p-0.866S$

In formula: v poisson's ratio

$v=-\frac{\frac{1}{2}{\left(\frac{V_p}{\mathrm{Vs}}\right)}^2-1}{{\left(\frac{V_p}{\mathrm{Vs}}\right)}^2-1}$

α is constant

$\mathrm{\α}=1-\frac{E}{3(1-2v)}\×{10}^{-5}$

Wherein: E young's modulus of elasticity $E={\mathrm{\ρ}}_b\×V_p^2\frac{{3V}_p^2-{4V}_s^2}{V_p^2-V_s^2}\×1000$

S is shear strength

$S=0.544\cos \left(\mathrm{\ψ}\right)V_p^2$

Wherein ψ=(57.8-1.05V _sh× 100) π/180

Δ P _maxshake out for gas well is maximum pressure reduction, MPa; P _pfor pore pressure, MPa; P _ofor on cover rock pressure, MPa; V _pfor velocity of longitudinal wave, m/s; V _sfor shear wave velocity, m/s; V _shfor shale content, %; ρ _bfor rock density, g/cm ³.

For edge-bottom water gas reservoir, the producing pressure differential drawn according to gas well and gas well Relationship with Yield get 2A > Δ P _maxbetween > A, according to the larger value of influence on water body degree more close to A value, otherwise increase.

Wherein, in step (1a), flow equation is:

$P_R^2-P_{\mathrm{wf}}^2=\mathrm{Aq}+{\mathrm{Bq}}^2---\left(1\right)$

Wherein the expression formula of coefficient A, B is respectively

$A=\frac{1.291\×{10}^{-3}T\stackrel{\‾}{\mathrm{\μ}}\stackrel{\‾}{Z}}{K_{\mathrm{rg}\left(S_{\mathrm{wi}}\right)}h}[\ln \left(\frac{0.472r_e}{r_w}\right)+S]---\left(2\right)$

$B=\frac{2.282\×{10}^{-21}\mathrm{\β}{\mathrm{\γ}}_g\stackrel{\‾}{Z}T}{r_2{h}^2}---\left(3\right)$

In formula:

P _rfor strata pressure, MPa; P _wffor flowing bottomhole pressure (FBHP), MPa; Q is gas production, 10 ⁴m ³/ d; T is reservoir temperature, K; for average Natural Gas Viscosity, mPas; for average natural gas deviation factors, zero dimension; for the gas phase relative permeability under the irreducible water saturation of stratum, 10 ^-3μm ²; H is gas reservoir formation thickness, m; r _efor gas well drainage radius, m; r _wfor wellbore radius, m; S is skin factor, zero dimension.

Wherein, in step (1b), gas well Particle in Vertical Pipe Flow equation is:

$p_{\mathrm{wf}}=\sqrt{p_{\mathrm{tf}}^2{e}^{2s}+\frac{1.324\×{10}^{-18}{\left(q_{\mathrm{sc}}\stackrel{\‾}{T}\stackrel{\‾}{Z}\right)}^2(e^{2s}-1)}{d^5}}---\left(4\right)$

In formula: p _wf-flowing bottomhole pressure (FBHP), MPa; P _tf-well head pressure, MPa; gas average temperature in-tubing string, K; -wellbore gas coefficient of mean deviation, dimensionless; q _sc-gas standard condition down-off, m ³/ d; D-pipe aperture, mm.

Compared with prior art underground natural gas storage tank of the present invention well rational productivity forecast value revision method has following beneficial effect:

Parameter involved in the present invention is easy to get in the manufacturing process of gas field, and adopt producing pressure differential production control ability intuitive and convenient, as long as know that gas well flows into, flow out (nodal method) curvilinear motion relation, revised gas well liquid loading ability can be obtained, produce actual theoretical foundation for the formulation of air reservoir operating scheme and the establishment of lower step Adjusted Option provide more to meet.

Accompanying drawing explanation

Fig. 1 is that gas well inflow and outflow crosses curve.

Fig. 2 is gas well daily output tolerance and producing pressure differential relation curve.

Fig. 3 is that the inflow and outflow of reasonable pressure correction gas well crosses curve.

Detailed description of the invention

Below with reference to specific embodiment, underground natural gas storage tank of the present invention gas well deliverability modification method is further elaborated, has more complete, accurate and deep understanding to help those skilled in the art to inventive concept of the present invention, technical scheme; It is to be understood that be all exemplary in the description of specific embodiment, and do not mean limiting the scope of the invention, interest field of the present invention is as the criterion with the claim limited.

Embodiment 1

Below by the production history before and after certain air reservoir gas well deliverability correction, air reservoir gas well deliverability modification method of the present invention is described.Described method described in the present embodiment mainly comprises the following steps: utilize certain air reservoir well test data to obtain gas well binomial potential curve and equation air reservoir different pressures sub-surface flowing IPR curve can be drawn out.Use oil gas two-phase Particle in Vertical Pipe Flow formulae discovery gas well shaft bottom to the gas deliverability of well head, tubing diameter has selected 2 (7/8) ", well head pressure, to be not less than 4MPa for constraints, to have been carried out pit shaft gas deliverability and has been calculated, drawn gas well elution curve.And then the gas well inflow and outflow obtained as shown in Figure 1 crosses curve.Flow into curve and elution curve according to gas well to cross point value, draw the gas well gas production that this air reservoir gas well is corresponding when different pressures and producing pressure differential, result is as shown in table 1.

Yield data under different pressures before the correction of table 1 gas well

In table 1, result is the gas well maximum flow capacity of gas well under stratum ability and tubing size matching condition, but due to local area be sandstone air reservoir, to shake out experimental data according to gas well, local area gas well will obviously shake out when pressure reduction reaches 10MPa.Therefore, the restriction of 10MPa pressure reduction to be added, as shown in Figure 3, in case gas well shakes out affect gas well output and application life when the reasonable ability of design gas well.In addition, for the air reservoir that there is Bian Shui, end water intrusion effect, produce the restriction of water limit pressure difference according to gas well and determine Gas well dewatering pressure reduction, producing pressure differential should lower than Gas well dewatering pressure reduction; For without shake out and the gas well liquid loading pressure reduction of influence on water body lower than 2 multiple differential pressures of Relationship with Yield flex point pressure reduction, situation as shown in Figure 2.After the present embodiment correction, gas well liquid loading ability is in table 2, and comparing result can be found out: when producing high pressure after gas well correction, gas well gas deliverability decreases, and guarantees to decrease gas reservoir and gas well impact, makes gas well gas deliverability more reasonable.

Yield data under different pressures after the correction of table 2 gas well

Adopt the air reservoir gas well deliverability modification method that the method described in the present embodiment is derived, can the comparatively following gas well liquid loading ability of Accurate Prediction, can reduce bring thus to reservoir and gas well injury, there is important guiding effect to the steady production realizing gas-producing well, to formulate for air reservoir development plan and lower step measure and Adjusted Option establishment provide more to meet and produce actual theoretical foundation.

For the ordinary skill in the art; specific embodiment is just to invention has been exemplary description; obvious specific implementation of the present invention is not subject to the restrictions described above; as long as have employed the improvement of the various unsubstantialities that method of the present invention is conceived and technical scheme is carried out; or design of the present invention and technical scheme directly applied to other occasion, all within protection scope of the present invention without to improve.

Claims (6)

1. a underground natural gas storage tank well rational productivity forecast value revision method, is characterized in that comprising the following steps:

(1a) according to Gas well test data determination gas well deliverability, flow equation when pseudostable flow moves that the gas well of state is anhydrous to be produced, and obtain flowing into curve;

(1b) elution curve is obtained according to gas well straight tube flow equation;

(1c) inflow curve is plotted in elution curve together with formed and to cross curve, the joint flowing into curve and elution curve obtains the gas well deliverability of gas well under gas well straight tube condition;

(2) for sandstone reservoirs utilize local area the to shake out pressure reduction that shakes out that experimental result draws, during gas well liquid loading, producing pressure differential should lower than the pressure reduction that shakes out; For the gas reservoir that there is edge-bottom water, produce the restriction of water limit pressure difference according to gas well and determine Gas well dewatering pressure reduction, producing pressure differential should lower than Gas well dewatering pressure reduction; For without shake out and the gas well liquid loading pressure reduction of influence on water body lower than 2 times of Relationship with Yield flex point pressure reduction; And according to this producing pressure differential correction gas well deliverability.

2. underground natural gas storage tank according to claim 1 well rational productivity forecast value revision method, is characterized in that flow equation is in step (1a):

$P_R^2-P_{\mathrm{wf}}^2=\mathrm{Aq}+{\mathrm{Bq}}^2---\left(1\right)$

Wherein the expression formula of coefficient A, B is respectively

$A=\frac{1.291\×{10}^{-3}T\stackrel{\‾}{\mathrm{\μ}}\stackrel{\‾}{Z}}{K_{\mathrm{rg}\left(S_{\mathrm{wi}}\right)}h}[\ln \left(\frac{0.472r_e}{r_w}\right)+S]---\left(2\right)$

$B=\frac{2.282\×{10}^{-21}{\mathrm{\β\γ}}_g\stackrel{\‾}{Z}T}{r_w{h}^2}---\left(3\right)$

In formula:

P _rfor strata pressure, MPa; P _wffor flowing bottomhole pressure (FBHP), MPa; Q is gas production, 10 ⁴m ³/ d; T is reservoir temperature, K; for average Natural Gas Viscosity, mPas; for average natural gas deviation factors, zero dimension; K _rg(S _wi) be the gas phase relative permeability under the irreducible water saturation of stratum, 10 ^-3μm ²; H is gas reservoir formation thickness, m; r _efor gas well drainage radius, m; γ _wfor wellbore radius, m; S is skin factor, zero dimension.

3. underground natural gas storage tank according to claim 1 well rational productivity forecast value revision method, is characterized in that gas well Particle in Vertical Pipe Flow equation is in step (1b):

$p_{\mathrm{wf}}=\sqrt{p_{\mathrm{tf}}^2{e}^{2s}+\frac{1.324\×{10}^{-18}{\left(q_{\mathrm{sc}}\stackrel{\‾}{T}\stackrel{\‾}{Z}\right)}^2(e^{2s}-1)}{d^5}}---\left(4\right)$

In formula: p _wf-flowing bottomhole pressure (FBHP), MPa; P _tf-well head pressure, MPa; gas average temperature in-tubing string, K; -wellbore gas coefficient of mean deviation, dimensionless; q _sc-gas standard condition down-off, m ³/ d; D-pipe aperture, mm.

4. underground natural gas storage tank according to claim 1 well rational productivity forecast value revision method, it is characterized in that in step (2) for sandstone reservoirs, the critical pressure reduction that shakes out of gas well is by the spontaneous potential curve in well-log information and stratum interval transit time, in conjunction with the rock mechanics parameters that formation density log obtains, obtain the critical pressure reduction that shakes out of gas reservoir.

5. underground natural gas storage tank according to claim 4 well rational productivity forecast value revision method, is characterized in that:

${\mathrm{\ΔP}}_{\max }=P_p-\frac{0.5v}{1-v}{P}_o+\frac{1-1.5v}{1-v}{\mathrm{\αP}}_p-0.866S$

In formula: v poisson's ratio

$v=-\frac{\frac{1}{2}{\left(\frac{V_p}{\mathrm{Vs}}\right)}^2-1}{{\left(\frac{V_p}{\mathrm{Vs}}\right)}^2-1}$

α is constant

$\mathrm{\α}=1-\frac{E}{3(1-2v)}\×{10}^{-5}$

Wherein: E young's modulus of elasticity $E={\mathrm{\ρ}}_b\×V_p^2\frac{{3V}_p^2-{4V}_s^2}{V_p^2-V_s^2}\×1000$

S is shear strength

$S=0.544\cos \left(\mathrm{\ψ}\right)V_p^2$

Wherein $\mathrm{\ψ}=(\text{57.8-1.05}{V}_{\mathrm{sh}}\×100)\mathrm{\π}/180$

Δ P _maxshake out for gas well is maximum pressure reduction, MPa; P _pfor pore pressure, MPa; P _ofor on cover rock pressure, MPa; V _pfor velocity of longitudinal wave, m/s; V _sfor shear wave velocity, m/s; V _shfor shale content, %; ρ _bfor rock density, g/cm ³.

6. underground natural gas storage tank according to claim 1 well rational productivity forecast value revision method, is characterized in that for edge-bottom water gas reservoir in step (2), and the producing pressure differential drawn according to gas well and gas well Relationship with Yield get 2A > Δ P _maxbetween > A.