CN102998422B - Prediction method for solubility of elemental sulfur in sulfur-containing gas - Google Patents

Abstract

The invention discloses a prediction method for solubility of elemental sulfur in sulfur-containing gas. The method comprises the steps of first determining H2S content and gas density in the sulfur-containing gas and calculating according to Cr=rho<k>exp(a/T +b); and determining constants k, a and b, wherein the constants k, a and b are determined according to the conformity of the H2S content and the gas density in the sulfur-containing gas with a certain set of data. The prediction result of the method has good fitness with an actual value.

Description

The Forecasting Methodology of elementary sulfur solubleness in sulfur-containing gas

Technical field

The present invention relates to the Forecasting Methodology about elementary sulfur solubleness in rock gas in gas prospecting, exploitation.

Background technology

Along with sour gas reservoir constantly gos deep into exploratory development, its adjoint problem is also paid close attention to thereupon widely.In sour gas reservoir performance history, H ₂s burn into severe toxicity and sulphur deposition are the Three Difficult Issues needing to pay close attention to.And for gas reservoir engineering Shi Eryan, Elemental sulfur deposition is most crucial problem, elementary sulfur (elemental sulfur) deposits and the reduction of gas well output all can be caused even directly to stop production in reservoir, shaft bottom or oil pipe.Therefore, the Accurate Prediction of elementary sulfur solubleness is one of problem that must first solve in sour gas reservoir performance history.Although experiment can obtain the elementary sulfur solubleness under different temperatures pressure and physical property of natural gas, but it needs a large amount of time and equipment cost, also there is toxicity simultaneously, therefore by experiment detection means detect in real time Practical Project practice in not there is practical value.Therefore, extensively theoretical empirical formulae discovery is passed through by the CHrastil model of following formula (1) in the prediction putting into practice elementary sulfur solubleness.

$C_r={\mathrm{\&rho;}}^k\exp (\frac{a}{T}+b)---\left(1\right)$

In above formula, mixed gas density is expressed from the next:

$\mathrm{\&rho;}=\frac{M_a{\mathrm{\&gamma;}}_{g}p}{\mathrm{ZRT}}=3.484\&times;{10}^3\frac{{\mathrm{\&gamma;}}_{g}p}{\mathrm{ZT}}---\left(2\right)$

In formula: C _rthe concentration of-solute in gas, g/L;

The density of ρ-gas, g/L;

The temperature of T-gas, K;

K-association number (number of the solvent molecule be namely combined with a solute molecule);

M _athe molecular weight of-dry air, 28.97;

γ _gthe relative density of-gas;

The Z-factor (mean value) of Z-gas;

R-universal gas constant, 0.008315MPa.m ³/ kmol.k;

P-gaseous tension, MPa.

1997, Roberts.B.E. on the basis of Chrastll Model on Solubilities, in conjunction with the experimental data (table 1) of two group element sulphur solubleness in sulfur-containing gas that E.Brunner and W.Woll records, simulated the constant coefficient model of a set of prediction elementary sulfur solubleness in sulfur-containing gas, computing formula is as shown in the formula (3):

$C_r={\mathrm{\&rho;}}^4(\frac{-4666}{T}-4.5711)---\left(3\right)$

Table 0Roberts.B.E fits and uses experimental system

Experimental system	Gas composition
		BW1	66%CH 4、20%H 2S、10%CO 2、4%N 2
BW3	81%CH 4、6%H 2S、9%CO 2、4%N 2

Elementary sulfur after Model on Solubilities (3) proposition, because it is convenient and practical, obtains very soon and uses widely in sulfur-containing gas.But, due to the undeclared temperature, pressure scope that it is suitable for of CHrastil model itself and gas composition feature, this model only with density and temperature for variable, and the experimental data that Roberts model uses is less, this theoretical model is caused to have some limitations, namely deviation is excessive under certain condition, cannot apply in engineering practice.To this, domestic and international many researchists have studied the relation of elementary sulfur solubleness and physical property of natural gas under different temperatures pressure, but Solubility Prediction model still only rests on the experimental data constant coefficient model of Roberts, how to improve this theoretical model more comprehensively and need further investigation to reduce deviation.

Summary of the invention

The problem that the deviation existed for elementary sulfur Solubility Prediction method in existing sulfur-containing gas and model is larger, the object of the present invention is to provide the Forecasting Methodology of elementary sulfur solubleness in a kind of new sulfur-containing gas.

A Forecasting Methodology for elementary sulfur solubleness in sulfur-containing gas, first determines H in sulfur-containing gas ₂s content and natural gas density, and the solubleness Cr calculating element sulphur according to following formula (1),

$C_r={\mathrm{\&rho;}}^k\exp (\frac{a}{T}+b)---\left(1\right)$

In formula: Cr is the solubleness of sulphur, unit is g/m ³; T is natural gas temperature, and unit is K;

The determination of constant k, a, b is the H of rock gas per sample ₂the density of S mass content and rock gas is with certain is organized the situation of conforming in data and determines below:

A, H ₂s content is 20%, natural gas density ρ <200kg/m ³, k=1.592044, a=-2737.23, b=-8.89768;

Natural gas density ρ >200kg/m ³, k=3.288695, a=4880.74, b=-12.4969;

B, H ₂s content is 7%, natural gas density ρ <200kg/m ³, k=1.38, a=-2582.202543, b=-8.39375;

Natural gas density ρ >200kg/m ³, k=3.20, a=4880.738659, b=-12.4969;

C, H ₂s content is 6%, natural gas density ρ <200kg/m ³, k=1.20, a=-2582.202543, b=-8.393748181;

Natural gas density ρ >200kg/m ³, k=3.28, a=-4880.738659, b=-12.49685448;

D, H ₂s content is 1%, natural gas density ρ <200kg/m ³, k=1.20, a=-2582.2, b=-8.39375;

Natural gas density ρ >200kg/m ³, k=3.245, a=-4880.74, b=-12.4969.

The Forecasting Methodology of elementary sulfur solubleness in sulfur-containing gas of the present invention, although remain based on CHrastil model, considers H ₂s content and density are on the impact of constant k, a, b, and k, a, b value under obtaining different condition.Through checking, Forecasting Methodology of the present invention is compared with existing Roberts.B.E. model, it predicts the outcome close many with sulfur solubility trial value under rock gas actual reservoir temperature, pressure condition, and energy matching preferably and prediction element sulfur solubility are with temperature, pressure Changing Pattern.

Embodiment

Below in conjunction with specific embodiment, the present invention is described in further detail, to help understanding content of the present invention.

Embodiment 1

The gas component of test is as table 1.

Table 1 gas component

Component	H 2S	N 2	He	CO 2	CH 4
						Well stream thing (wt%)	6.86	0.5	0.02	2.76	89.86

Due to H in gas component ₂s is 6.86%, and close to 7%, therefore determine to adopt B formula, calculating natural gas density according to temperature and pressure by (2) formula, is be greater than 200 (kg/m according to density ³still 200 (kg/m are less than ³select k, a, b parameter, natural gas density ρ <200kg/m ³, k=1.38, a=-2582.202543, b=-8.39375; Natural gas density ρ >200kg/m ³, k=3.20, a=-4880.738659, b=-12.4969; Calculate the solubleness of element sulphur again according to formula (1), and calculate element sulphur solubleness with the Roberts formula of formula (3) simultaneously, and contrast with actual measurement solubleness, its result is as shown in table 2.

Table 2 Calculation of Solubility contrasts

As can be seen from Table 2, adopt the result of Roberts formulae discovery and measured value to differ greatly (more than two orders of magnitude), and the result of method of the present invention calculating and measured value close many.

Embodiment 2

Experiment is as shown in table 3 with institute's natural component.

Table 3 gas component and mass content thereof

Component	H 2S	CO 2	CH 4
				1	4.95%	7.40%	87.65%

Found out by table 3, H ₂s content is 4.95%, close to 6%, therefore selects formula C, and calculate density according to temperature, pressure and relative density, density is all greater than 200kg/m ³, therefore k=3.28, a=-4880.738659, b=-12.49685448, calculates the solubleness of element sulphur, and calculates element sulphur solubleness with the Roberts formula of formula (3) simultaneously, and contrasts with actual measurement solubleness, and its result is as shown in table 4.

Table 4 Calculation of Solubility contrasts

As can be seen from Table 4, differ greatly according to the solubleness of Roberts formulae discovery and measured value, relative to Roberts model, the result that method of the present invention calculates and measured value close many.

Embodiment 3

Experiment rock gas component is as shown in table 5.

Table 5 gas component and mass content

Component	H 2S	CO 2	CH 4
				2	9.93%	7.16%	82.91%

H as can be seen from Table 6 ₂s content, close to 7%, chooses B formula, calculates density be all greater than 200kg/m according to temperature, pressure and relative density ³, determine to calculate with k=3.20, a=-4880.738659, b=-12.4969, use Roberts formulae discovery simultaneously, with measured value comparing result as table 6.

Table 6 Calculation of Solubility contrasts

As can be seen from Table 6, differ greatly according to the solubleness of Roberts formulae discovery and measured value, the result calculated relative to Roberts model method of the present invention and measured value close many.

Embodiment 4

Rock gas component is as shown in table 7.

Table 7 gas component and mass content

Component	H 2S	CO 2	CH 4
				3	14.98%	7.31%	77.71%

According to H in rock gas ₂s content is determined to adopt A formula, and is greater than 200kg/m according to natural gas density ³, determine to calculate with k=3.288695, a=-4880.74, b=-12.4969, use Roberts formulae discovery simultaneously, with measured value comparing result as table 8.

Table 8 Calculation of Solubility contrasts

As can be seen from Table 8, relative to Roberts model, result and the measured value of method calculating of the present invention are close many.

Embodiment 5

Rock gas component is as shown in table 9.

Table 9 gas component and mass content

Component	H 2S	CO 2	CH 4
				4	17.71%	6.81%	75.48%

According to H ₂s can determine to adopt A formula, then in conjunction with density, when determining that temperature is 303.2K, pressure is 20Mpa, k, a, b value is respectively k=1.592044, a=-2737.23, b=-8.89768; Other groups get k=3.288695, a=-4880.74, b=-12.4969; Calculate element sulphur solubleness, and as shown in table 10 with the Comparative result of measured value and Roberts formulae discovery.

Table 10 Calculation of Solubility contrasts

As can be seen from Table 10, the result of the present invention's calculating is than the result of Roberts formulae discovery and the better of measured value matching.

Embodiment 6

Table 11 gas component and mass content

Component	H 2S	CO 2	CH 4
				5	26.62%	7%	66.38%

According to rock gas H ₂s component concentration is determined to calculate by k=3.288695, a=-4880.74, b=-12.4969 in formula A, the results are shown in Table 12.

Table 12 Calculation of Solubility contrasts

As can be seen from Table 12, the result of the present invention's calculating is than the result of Roberts formulae discovery and the better of measured value matching.

Embodiment 7

Table 13 gas component and mass content

Component	H 2S	CO 2	CH 4
				6	10%	0.86%	89.14%

According to H ₂s component concentration is all greater than 200kg/m close to 7% and density ³, determine to calculate by k=3.20, a=-4880.738659, b=-12.4969 in formula B, it the results are shown in Table 14.

Table 14 Calculation of Solubility contrasts

As seen from Table 14, result of the present invention is close many with measured value compared with the result of Roberts formulae discovery.

Embodiment 8

Table 15 gas component and mass content

Component	H 2S	CO 2	CH 4
				7	10.03%	10.39%	79.58%

According to H ₂s content and density, determine to calculate with k=3.20, a=4880.738659, b=-12.4969 in B group, the results are shown in Table 16.

Table 16 Calculation of Solubility contrasts

As can be seen from Table 16, result of the present invention is close many with measured value compared with the result of Roberts formulae discovery.

Embodiment 9

Table 17 gas component and mass content

H 2S	CO 2	N 2	CH 4	C 2H 6	C 3H 8
						44.11%	0.72%	0.68%	47.97%	4.09%	2.43%

According to H ₂s content is determined with A group formulae discovery, and is greater than according to density and is less than 200kg/m ³select k, a, b, calculate element sulphur solubleness, the results are shown in Table 18.

Table 18 Calculation of Solubility contrasts

As can be seen from Table 18, result of the present invention is close many with measured value compared with the result of Roberts formulae discovery.

Claims (1)

1. the Forecasting Methodology of elementary sulfur solubleness in sulfur-containing gas, is characterized in that, first determine H in sulfur-containing gas ₂s content and natural gas density, and the solubleness Cr calculating element sulphur according to following formula (1),

In formula: Cr is the solubleness of sulphur, unit is g/m ³; T is natural gas temperature, and unit is K;

The determination of constant k, a, b is the H of rock gas per sample ₂the density of S mass content and rock gas is with certain is organized the situation of conforming in data and determines below:

A, H ₂s content is 20%, natural gas density ρ < 200kg/m ³, k=1.592044, a=-2737.23, b=-8.89768; Natural gas density ρ > 200kg/m ³, k=3.288695, a=-4880.74, b=-12.4969;

B, H ₂s content is 7%, natural gas density ρ < 200kg/m ³, k=1.38, a=-2582.202543, b=-8.39375; Natural gas density ρ > 200kg/m ³, k=3.20, a=-4880.738659, b=-12.4969;

C, H ₂s content is 6%, natural gas density ρ < 200kg/m ³, k=1.20, a=-2582.202543, b=-8.393748181; Natural gas density ρ > 200kg/m ³, k=3.28, a=-4880.738659, b=-12.49685448;

D, H ₂s content is 1%, natural gas density ρ < 200kg/m ³, k=1.20, a=-2582.2, b=-8.39375; Natural gas density ρ > 200kg/m ³, k=3.245, a=-4880.74, b=-12.4969.