CN102721635A - Quantitative analysis method for amount of precipitated wax of reservoirs with different pore structures - Google Patents

Abstract

The invention relates to a quantitative analysis method for the amount of precipitated wax of reservoirs with different pore structures in the field of oil exploitation. The quantitative analysis method for the amount of the precipitated wax of reservoirs with different pore structures comprises the following steps of: quantitatively detecting the amount of the precipitated wax of a sample of a reservoir in a wax precipitation state by gas chromatography; measuring the specific surface area and the aperture parameter of rock of the reservoir after wax is removed by a nitrogen adsorption method; establishing a one-to-one correspondence curve of the amount of precipitated wax of the reservoir and the specific surface area and the aperture; and analyzing the deposition characteristic and the deposition law of paraffin wax in porous media. The quantitative analysis method for the amount of precipitated wax of reservoirs with different pore structures is simple in experimental process and high in operability, and can be used for visually and fast determining the relationship between the amount of precipitated wax of the reservoir and the specific surface area, and the relationship between the amount of precipitated wax of the reservoir and the aperture, and a qualitative interpretation of the amount of the precipitated wax and the pore parameter of the reservoir is changed into quantitative and semi-quantitative interpretation, so that subsequent wax removal and preventative measures for the reservoir are established scientifically and reasonably.

Description

A kind of different pore structures reservoir is analysed the quantitative analysis method of wax amount

Technical field

The present invention relates to the quantitative analysis method that a kind of field of petroleum exploitation different pore structures reservoir is analysed the wax amount.

Background technology

In oil-gas mining, solid precipitation phenomenons such as wax and bituminous matter can be accompanied by each link of Petroleum Production: oil and gas reservoir, exploitation, equipment, gathering line or the like always.After the precipitation of paraffin, can damage well, stop up oil pipeline, reduce the efficient of gathering.But; Paraffin is one of basic composition of oil; In the oil-gas mining process, can produce the precipitation of paraffin phenomenon inevitably, and there are some researches show, deposition of wax is irreversible; Be paraffin in case just very difficult being dissolved in again in the same fluid after separating out in the solution also is like this even recovered original formation temperature.

Paraffin separates out in the stratum that the part that can cause the fluid flow bore road is stopped up or sealing, reduces the factor of porosity and the permeability on stratum greatly, thus big limitations the seepage flow of oil gas, thereby reduce the production capacity of oil well; And the paraffin that deposits is adsorbed in the porous medium surface, and the wetting state of rock is changed, and reduces recovery ratio, had a strong impact on the production economic benefit.

At present; The research precipitation of paraffin adopts rock-kapillary simplified model usually to the influence of reservoir porosity and permeability; True reservoir rock is simplified to being made up of a series of capillary bunch; Derive the mutual relationship between factor of porosity, permeability, capillary radius and the specific surface of rock of rock thus: along with the increase of precipitation of paraffin thickness in the reservoir, factor of porosity and permeability all sharply reduce; The variable quantity of factor of porosity and precipitation of paraffin thickness are approximate exponential taper relation, and changes in permeability amount and precipitation of paraffin thickness are the approximately linear relation of successively decreasing.

Above-mentioned test model can only can not truly reflect precipitation of paraffin characteristic and deposition rule in the porous medium to analysing the wax amount and the reservoir pore space parameter is done qualitative interpretation, can't realize the long-pending wax amount of analysing with the pore texture reservoir of different rock specific surface is carried out quantitative test.

Summary of the invention

The quantitative analysis method that the object of the present invention is to provide simple, the workable measurement reservoir different pore structures of a kind of experimentation to analyse the wax amount; This method can be intuitively, confirm that fast reservoir analyses the relation between wax amount and specific surface area and the aperture, realize analysing wax amount and reservoir pore space parameter by qualitative interpretation to quantitatively and sxemiquantitative explanation transformation.

For realizing above-mentioned purpose; The technical scheme that the present invention adopts is: a kind of different pore structures reservoir is analysed the quantitative analysis method of wax amount; Adopt gas chromatography that the wax amount of analysing that is in the reservoir sample of analysing the wax state is carried out detection by quantitative,, set up the one-to-one relationship curve that reservoir is analysed wax amount and specific surface area and aperture with specific surface area and the aperture parameters behind the nitrogen adsorption method mensuration reservoir rock wax removal; Analyze precipitation of paraffin characteristic and deposition rule in the porous medium, specifically comprise the following steps:

1, choose and analyse the serious reservoir of wax, extract the rock sample sample of different pore structures, before the test sample is carried out pre-service:

(1) with ethanol sample being carried out washing oil handles;

(2) sample is processed the graininess of the about 3mm of particle diameter, 2 parts in the sample of the about 5g of weight is respectively charged in the special-purpose test tube;

2,, the wax amount of analysing of sample is carried out qualitative and quantitative detection with gas phase and gaschromatographic mass spectrometry method:

(1) sample extraction

In the pretreated sample of step 1 is packed assay flask into, add normal hexane 50ml with above-mentioned, the oscillator of packing into vibration 10min; Filter; To filtrate at rotary evaporation in 60 ℃ of water-baths and constantly be stirred to do after, be transferred in the 10ml scale glass test tube, be settled to 5ml with normal hexane.Solid particle after the filtration stays does test specific surface area and aperture usefulness;

(2) sample purification

The 1ml concentrated sulphuric acid is added in the above-mentioned glass test tube solution, after mixing 2min on the vortex appearance,, draw supernatant liquor in the sample introduction bottle, treat the machine test with the centrifugal 10min of 5000r/min;

(3) sample test

A: inject gas chromatograph and gas chromatography mass spectrometer are measured respectively with the standard solution in step 2 (2) the sample introduction bottle;

B: analyse the wax qualitative and quantitative analysis: select for use 54～58 label paraffin as standard substance, with C26～C29 n-alkane add with peak area as qualitative and quantitative foundation;

3, the test in specific surface area and aperture

Handle the specific surface area and the aperture of filtering back solid particle samples with the full-automatic specific surface area of nitrogen adsorption method and pore size determination appearance testing procedure 2 (1), decide the shape in hole according to the shape of hysteresis loop, by different pore model calculating pore size distribution and specific surface areas;

4, the stratographic analysis recovery, precision checking:

To pass through the paraffin that adds high, medium and low 3 variable concentrations in the not content of wax core sample after step 3 is tested specific surface area and pore texture; Make positive; Carry out extraction and analysis according to (1) in the above-mentioned steps 2～(3) method; Replicate determination 6 times, the recovery reaches 95.8%, shows that measurement result is accurately and reliably;

5, the test data of comparative analysis step 2 and step 3 is set up reservoir and is analysed wax amount and specific surface area and the aperture structure figure that crosses, and the relation between wax amount and specific surface area and the aperture is analysed in comparative analysis.Reservoir is divided into 3 types by its pore size: macropore:＞50nm, mesopore: 2～50nm, micropore:＜2nm, carry out quantitative test to the wax amount of analysing of several kinds of reservoir different pore structures and specific surface area.

Said step 3 comprises the following steps: that (1) handle to filter step 2 (1) in the special-purpose test tube of packing into after the solid particle sample oven dry of back, under 100 ℃ and 300 ℃ of desorption conditions, places the processing that outgases in the instrument degas chamber respectively;

(2) degassing places liquid nitrogen with test tube after accomplishing, and moves to the analysis room and analyzes, and at-194 ℃～-198 ℃ temperature range build-in test nitrogen adsorbances and pressure, generates isothermal adsorption-desorption curve;

(3) analyze isothermal adsorption-desorption curve and be detained annular attitude, use corresponding principle to calculate, obtain pore size distribution curve.

Different pore structures reservoir of the present invention is analysed the quantitative analysis method of wax amount can be to analysing the wax amount and the reservoir pore space parameter is done qualitative interpretation; Can truly reflect precipitation of paraffin characteristic and deposition rule in the porous medium, realize the long-pending wax amount of analysing with the pore texture reservoir of different rock specific surface is carried out quantitative test.

Description of drawings

Fig. 1 is the process flow diagram that different pore structures reservoir of the present invention is analysed the quantitative analysis method of wax amount;

Fig. 2 is the gas chromatography spectrogram;

Fig. 3 gaschromatographic mass spectrometry figure;

Fig. 4 is a different labels paraffin distribution of normal alkanes situation map;

Fig. 5 is an isothermal adsorption-desorption curve.

Embodiment

Detailed elaboration is done in quantitative analysis method below in conjunction with embodiment and accompanying drawing are analysed the wax amount to different pore structures reservoir of the present invention.

A kind of different pore structures reservoir is analysed the quantitative analysis method of wax amount; Adopt gas chromatography that the wax amount of analysing that is in the reservoir sample of analysing the wax state is carried out detection by quantitative; With specific surface area and the aperture parameters behind the nitrogen adsorption method mensuration reservoir rock wax removal, set up the one-to-one relationship curve that reservoir is analysed wax amount and specific surface area and aperture, analyze precipitation of paraffin characteristic and deposition rule in the porous medium; This method flow diagram is as shown in Figure 1, and practical implementation step and technical essential are following:

1, choose and analyse the serious reservoir of wax, extract the rock sample sample of different pore structures, before the test sample is carried out following pre-service:

(1) with ethanol rock sample being carried out washing oil handles;

(2) sample is processed the graininess of the about 3mm of particle diameter, 2 parts in the sample of the about 5g of weight is respectively charged in the special-purpose test tube;

2, with gas phase and gaschromatographic mass spectrometry method, the wax amount of analysing of sample is carried out qualitative and quantitative detection, concrete steps are following:

(1) sample extraction

In the pretreated sample of step 1 is packed assay flask into, add normal hexane 50ml with above-mentioned, the oscillator of packing into vibration 10min; Filter; To filtrate at rotary evaporation in 60 ℃ of water-baths and constantly be stirred to do after, be transferred in the 10ml scale glass test tube, be settled to 5ml with normal hexane.Solid particle after the filtration stays does test specific surface area and aperture usefulness.

(2) sample purification

The 1ml concentrated sulphuric acid is added in the above-mentioned glass test tube solution, after mixing 2min on the vortex appearance,, draw supernatant liquor in the sample introduction bottle, treat the machine test with the centrifugal 10min of 5000r/min.

(3) sample test

A: with the standard solution in step 2 (2) the sample introduction bottle respectively inject gas chromatograph and gas chromatography mass spectrometer measure, chromatogram and mass spectrum conditional parameter are following:

A, GC conditions parameter:

(1) chromatographic column: HP-5 (MS) 30.00m * 0.32mm * 0.25 μ m;

(2) intensification condition: 150 ℃ of initial temperatures, be warming up to 300 ℃ with 10 ℃/min, keep 10min, after 310 ℃, move 2min;

(3) injector temperature: 250 ℃;

(4) detector temperature: 270 ℃; Flow velocity: 1.0ml/min;

(5) input mode; Split sampling, split ratio 10: 1; Sample size: 5.0 μ l.

B, mass spectrum conditional parameter:

(1) interface temperature is 280 ℃;

(2) ion source temperature is 230 ℃;

(3) the quadrupole rod temperature is 150 ℃;

(4) scan pattern SCAN;

(5) ion scan scope: m/z 50～500.

Gas chromatography is confirmed 4 (C26, C27, C28, C29) n-alkanes according to retention time, and mass spectrum confirms that through library searching the gas chromatography spectrogram is as shown in Figure 2 according to each component fragmention characteristic, and gaschromatographic mass spectrometry figure is as shown in Figure 3.

B: analyse the wax qualitative and quantitative analysis: the distribution situation to n-alkane in the paraffin is analyzed; Solution with the candle preparation written treaty 1.000mg/ml of the paraffin of different labels and purchase; Use vapor-phase chromatography analysis respectively; With the carbon number is horizontal ordinate, and the peak area of corresponding n-alkane (all conversion is 1.000mg/m1) is drawn correlation curve for ordinate.

Repeated detection result shows that the peak area sum of the different labels paraffin C26～C29 n-alkane of same concentrations is very approaching, and relative deviation is no more than 10%, and is as shown in Figure 4.Select for use 54～58 label paraffin as standard substance, with C26～C29 n-alkane add with peak area as qualitative and quantitative foundation;

3, the test in specific surface area and aperture

Handle the specific surface area and the aperture of filtering back solid particle sample with full-automatic specific surface area of nitrogen adsorption method and pore size determination appearance testing procedure 2 (1).Nitrogen adsorption method principle is that the sample after the oven dry degassing is handled places liquid nitrogen, regulates different tests pressure, measures the adsorbance to nitrogen respectively, draws absorption and desorption isotherm.Decide the shape in hole according to the shape of hysteresis loop, calculate pore size distribution and specific surface area by different pore models, concrete steps are following:

(1) step 2 (1) handle is filtered in the special-purpose test tube of packing into after the solid particle sample oven dry of back, under 100 ℃ and 300 ℃ of desorption conditions, place the processing that outgases in the instrument degas chamber respectively;

(2) degassing places liquid nitrogen with test tube after accomplishing, and moves to the analysis room and analyzes, and at-194 ℃～-198 ℃ temperature range build-in test nitrogen adsorbances and pressure, generates isothermal adsorption-desorption curve, shown in figure (5);

(3) analyze isothermal adsorption-desorption curve and be detained annular attitude, use corresponding principle to calculate, obtain pore size distribution curve.

The micropore diameter test is to utilize BJH (Barrett-Joyner-Halenda) principle, and computing formula is shown in formula (1):

Formula (1): $V_{\mathrm{Pn}}={\left\{\frac{r_{\mathrm{Pn}}}{r_{\mathrm{Kn}}+{\mathrm{\Δ\; l}}_n/2}\right\}}^2\{{\mathrm{\Δ\; V}}_n-{\mathrm{\Δ\; t}}_n\underset{j=1}{\overset{n-1}{\mathrm{\Σ}}}{A}_{\mathrm{Cj}}\}$

In the formula: V _Pn---volume of voids;

r _Pn---the largest hole radius;

r _Kn---capillary radius;

V _n---the kapillary volume;

t _n---the blanket of nitrogen thickness of absorption;

A _Cj---the area after the previous emptying.

The analysis of specific surface parameter mainly is based on the BET theory of testing and carries out; Through surveying 3～5 groups of samples multilayer adsorbance under different nitrogen partial pressures; With P/P0 is the X axle, and P/V (P0-P) is the Y axle, is figure by the BET equation and carries out linear fit; Obtain slope and intercept, calculate the sample specific surface area thereby try to achieve the Vm value.When P/P0 got o'clock in 0.35～0.05 scope, BET equation and actual adsorption process matched, and the figure linearity is also fine, therefore in the actual test process reconnaissance in this scope.The BET equation is shown in formula (2):

Formula (2): $\frac{P}{V(P_0-P)}=\frac{1}{\mathrm{Vm}\·C}+\frac{C-1}{\mathrm{Vm}\·C}\×\left\{\frac{P}{P_0}\right\}$

In the formula: P---nitrogen partial pressure;

P ₀---under the liquid nitrogen temperature, the saturated vapor pressure of nitrogen;

The actual adsorbance of V---sample surfaces nitrogen;

Vm---nitrogen individual layer saturated extent of adsorption;

The parameter that C---sample adsorptive power is relevant.

4, the stratographic analysis recovery, precision checking:

To pass through the paraffin that adds high, medium and low 3 variable concentrations in the not content of wax core sample after step 3 is tested specific surface area and pore texture; Make positive; Carry out extraction and analysis according to (1) in the above-mentioned steps 2～(3) method; Replicate determination 6 times, the recovery reaches 95.8%, shows that measurement result is accurately and reliably;

5, the test data of comparative analysis step 2 and step 3 is set up reservoir and is analysed wax amount and specific surface area and the aperture structure figure that crosses, and the relation between wax amount and specific surface area and the aperture is analysed in comparative analysis.Reservoir is divided into 3 types by its pore size: macropore:＞50nm, mesopore: 2～50nm, micropore:＜2nm, carry out quantitative test to the wax amount of analysing of several kinds of reservoir different pore structures and specific surface area.

Claims (3)

1. quantitative analysis method that the different pore structures reservoir is analysed the wax amount; It is characterized in that: the wax amount of analysing that is in the reservoir sample of analysing the wax state is carried out detection by quantitative with gas chromatography; With specific surface area and the aperture parameters behind the nitrogen adsorption method mensuration reservoir rock wax removal; Set up reservoir and analyse the one-to-one relationship curve in wax amount and specific surface area and aperture, analyze precipitation of paraffin characteristic and deposition rule in the porous medium, specifically comprise the following steps:

1, choose and analyse the serious reservoir of wax, extract the rock sample sample of different pore structures, before the test sample is carried out pre-service:

2,, the wax amount of analysing of sample is carried out qualitative and quantitative detection with gas phase and gaschromatographic mass spectrometry method:

(1) sample extraction

In the pretreated sample of step 1 is packed assay flask into, add normal hexane 50ml with above-mentioned, the oscillator of packing into vibration 10min; Filter; To filtrate at rotary evaporation in 60 ℃ of water-baths and constantly be stirred to do after, be transferred in the 10ml scale glass test tube, be settled to 5ml with normal hexane.Solid particle after the filtration stays does test specific surface area and aperture usefulness;

(2) sample purification

The 1ml concentrated sulphuric acid is added in the above-mentioned glass test tube solution, after mixing 2min on the vortex appearance,, draw supernatant liquor in the sample introduction bottle, treat the machine test with the centrifugal 10min of 5000r/min;

(3) sample test

A: inject gas chromatograph and gas chromatography mass spectrometer are measured respectively with the standard solution in step 2 (2) the sample introduction bottle;

B: analyse the wax qualitative and quantitative analysis: select for use 54～58 label paraffin as standard substance, with C26～C29 n-alkane add with peak area as qualitative and quantitative foundation;

3, the test in specific area and aperture: with full-automatic specific area of nitrogen adsorption method and pore size determination appearance testing procedure 2(1) handle the specific area and the aperture of filtering back solid particle sample; Decide the shape in hole based on the shape of hysteresis loop, calculate pore size distribution and specific area by different pore models;

4, the stratographic analysis recovery, precision checking: will pass through the paraffin that adds high, normal, basic 3 variable concentrations in the not content of wax core sample after step 3 is tested specific surface area and pore texture; Make positive; Carry out extraction and analysis according to (1) in the above-mentioned steps 2～(3) method; Replicate determination 6 times, the recovery reaches 95.8%, shows that measurement result is accurately and reliably;

5, the test data of comparative analysis step 2 and step 3 is set up reservoir and is analysed wax amount and specific surface area and the aperture structure figure that crosses, and the relation between wax amount and specific surface area and the aperture is analysed in comparative analysis; Reservoir is divided into 3 types by its pore size: macropore:＞50nm, mesopore: 2～50nm, micropore:＜2nm, carry out quantitative test to the wax amount of analysing of several kinds of reservoir different pore structures and specific surface area.

2. different pore structures reservoir according to claim 1 is analysed the quantitative analysis method of wax amount, it is characterized in that: in the said step 1 The pretreatment is comprised the following steps: that (1) carry out washing oil with ethanol to sample and handle; (2) sample is processed the graininess of the about 3mm of particle diameter, 2 parts in the sample of the about 5g of weight is respectively charged in the special-purpose test tube.

3. different pore structures reservoir according to claim 1 is analysed the quantitative analysis method of wax amount, it is characterized in that: the test in specific surface area and aperture comprises the following steps: in the said step 3

(1) step 2 (1) handle is filtered in the special-purpose test tube of packing into after the solid particle sample oven dry of back, under 100 ℃ and 300 ℃ of desorption conditions, place the processing that outgases in the instrument degas chamber respectively;

(2) degassing places liquid nitrogen with test tube after accomplishing, and moves to the analysis room and analyzes, and test nitrogen adsorbance and pressure under-194 ℃～-198 ℃ temperature generate isothermal adsorption-desorption curve;

(3) analyze isothermal adsorption-desorption curve and be detained annular attitude, use corresponding principle to calculate, obtain pore size distribution curve.

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