CN105547961B - Retrograde gas condensate saturation degree determines method in exhaustion formula exploitation sandstone gas condensate reservoir reservoir - Google Patents

Abstract

The invention discloses a method for determining the reverse condensate oil saturation in a sandstone condensate gas reservoir reservoir developed by depletion, including: (1) obtaining the core of the actual reservoir, cleaning and drying it; (2) testing different oil saturation To determine the gas-phase effective permeability K _egi under the condition of degree S _oi , determine the values of parameters a and b in the formula S _oi =aln(K _egi )+b; (3) prepare formation fluid samples; (4) restore the core to the original reservoir (5) reduce the pore pressure in the rock core, record the inlet end pressure of the rock core, the outlet end pressure, and the gas outlet volume of the rock core outlet end; (6) calculate the gas phase effective permeability K _fegi under the average pressure condition in the rock core depletion experiment process; ( 7) Calculate the reverse condensate oil saturation S _oi under different pressure conditions in the sandstone condensate gas reservoir. The invention is reliable in principle, simple and applicable, comprehensively considers the influence of porous medium, water saturation and condensate oil flow, and has broad market prospects.

Description

Determination method of retrograde condensate oil saturation in sandstone condensate gas reservoirs developed by depletion

technical field

The invention relates to a method for determining the reverse condensate oil saturation in the depletion-type development of sandstone condensate gas pool reservoirs in the field of petroleum and natural gas exploration and development.

Background technique

Condensate gas reservoirs refer to the hydrocarbons accumulated underground under the temperature and pressure of the reservoir, the heavy components of gasoline fractions to kerosene fractions and a small amount of high molecular hydrocarbons are dispersed in the natural gas in a uniform vapor state, when the reservoir pressure is lower than When the dew point pressure is reached, heavy components (condensate oil) in the system will precipitate and exist in the pores in the form of liquid phase, reducing the flow capacity of the gas phase. Therefore, determining the reverse condensate oil saturation under different pressure conditions is of great significance for the quantitative evaluation of condensate oil loss and its influence on gas phase flow capacity. At present, high-temperature and high-pressure experiments are the main method to determine the reverse condensate oil saturation of condensate gas reservoirs: one is the constant volume depletion experiment (SY/T 5542- 2000), and the other is the core experimental testing method with the help of modern physical testing technology. However, because the conventional volumetric depletion test does not consider the influence of porous media, water saturation and condensate flow, the determined retrograde condensate saturation is quite different from that in porous media (Wang Zhouhua. The influence of oil-type condensate gas phase state, Drilling and production technology, 2009, 32(3), 56-59); In addition, using ultrasonic and other modern physical testing techniques to directly test the oil saturation of porous media inverse condensate, the experimental test is complicated and difficult (Guo Ping, Application of Ultrasound in the Test of Critical Flow Saturation of Condensate Oil, Natural Gas Industry, 2001, 21(3): 22-25).

Contents of the invention

The purpose of the present invention is to establish a method for determining the reverse condensate oil saturation in the core of a sandstone condensate gas reservoir reservoir under actual reservoir conditions based on conventional core depletion experiments and relative permeability curve testing methods. The principle is reliable, simple and applicable, and the influence of porous media, water saturation and condensate flow is comprehensively considered, and has broad market prospects.

In order to achieve the above technical objectives, the present invention provides the following technical solutions.

The method for determining the retrograde condensate oil saturation in a sandstone condensate gas reservoir by depletion development includes the following steps in sequence:

(1) Obtain the core of the actual reservoir, clean it, dry it, and test the diameter D (cm), length L (cm), permeability K ₀ (mD), and porosity φ (%);

(2) Refer to the "gas-water phase permeability curve test method" in the industry standard SY/T5345-2007, test the gas phase effective permeability K _egi under different oil saturation S _oi conditions, and determine the values of parameters a and b in the following formula :

S _oi =aln(K _egi )+b

The specific process is as follows:

① Obtain the natural gas, condensate oil and formation water produced by the wellhead of the actual condensate gas reservoir;

②Calculate the core pore volume V=0.25πLD ² φ, and inject formation water with a volume of V (ml) into the core to saturate it;

③Inject condensate oil into the core from the inlet end of the core until no water comes out from the outlet end of the core, measure the accumulated water volume V _w (ml), this volume is the initial saturated oil volume V _o , and calculate the irreducible water saturation S _or = (V－V _w )/V×100%, determine the initial oil saturation S _o in the core = (1－S _or )×100%;

_④Inject natural gas into the core from the inlet of the core, and record the pressure at the inlet of the core P _1i , the pressure at the outlet of P _2i , the volume of gas at the outlet of the core V _gi (ml), and the volume of oil at V _oi ( ml), calculate the oil saturation S _oi in the core = (V _o -V _oi )/V _o ×100%;

⑤ Calculate the gas phase effective permeability K _egi (mD) of the core corresponding to the oil saturation S _oi :

In the formula:

μ _gi —gas viscosity, mPa·s, according to the apparent critical temperature T _pc and apparent critical pressure P _pc of natural gas

Carr Kobayshi and Burrows Viscosity Chart;

L—core length, cm;

A—core cross-sectional area, cm ² , A=0.25πD ² , D—core diameter, cm;

⑥ Analyze the relationship between the oil saturation S _oi in the core and the gas phase effective permeability K _egi , and determine the values of the coefficients a and b in the formula S _oi =aln(K _egi )+b;

(3) According to the industry standard SY/T 5542-2000, refer to the dew point pressure P _b and single degassed oil ratio GOR ₁ in the gas reservoir original formation fluid property analysis report to prepare formation fluid samples, that is, condensate gas samples;

(4) Restore the core to the original reservoir state. The specific process is: saturate it with formation water, then gradually increase the temperature and pressurize until the pore pressure and temperature of the core are consistent with the original formation pressure and temperature of the gas reservoir. The radial pressure P _d is 3 MPa higher than the pore pressure P _f , and then the prepared formation fluid sample is injected into the core, and the gas-oil ratio GOR ₂ at the outlet end of the core is tested every 0.5 hours until it is consistent with GOR ₁ ;

(5) Simulate the experimental process of gas reservoir depletion: reduce the pore pressure in the core by reducing the pressure P _2i at the outlet end of the core according to a certain pressure drop rate, and keep the radial pressure P _d of the core 3 MPa higher than the pore pressure P _f during the depressurization process , record the inlet pressure P _1i , the outlet pressure P _2i , and the gas volume V _gi at the outlet of the core at every interval △t ₂ (S), until the pressure P _2i at the outlet of the core drops to the abandonment pressure of the gas reservoir;

(6) Calculate the gas phase effective permeability K _fegi under the average pressure P _i during the core depletion experiment according to the following formula, where P _i is the average value of the pressure P _1i at the inlet end of the core and the pressure P _2i at the outlet end:

(7) Bring the K _fegi corresponding to each P _i point into S _oi =aln(K _egi )+b, and calculate the different pressures in the sandstone condensate gas reservoir according to the values of a and b determined in step (2). Reverse condensate oil saturation S _oi under the condition.

Compared with the prior art, the method for determining the reverse condensate oil saturation in depletion-type development of condensate gas reservoirs provided by the present invention is reliable in principle, easy to operate, economical and applicable, and comprehensively considers porous media, water saturation and condensate oil flow The impact has a broad market prospect.

Description of drawings

Fig. 1 is the relationship curve between oil saturation and gas phase effective permeability.

Fig. 2 is the relationship curve between gas phase effective permeability and pressure during the depletion development process of condensate gas reservoirs.

Fig. 3 is the change curve of reverse condensate oil saturation during the depletion recovery of condensate gas reservoirs.

detailed description

Further illustrate the present invention according to accompanying drawing and embodiment below.

A method for determining the retrograde condensate oil saturation in the porous medium of a depleted gas condensate reservoir, comprising the following steps in sequence:

(1) Obtain a condensate gas reservoir core Y-1, wash, dry, test diameter D (6.5cm), length L (7.9cm), permeability K ₀ (1.12mD), porosity φ (9.5 %);

(2) Referring to the "gas-water phase permeability curve test method" in the industry standard SY/T5345-2007, test the gas phase effective permeability K _egi under different oil saturation S _oi conditions, as shown in Figure 1, and establish the relationship between the two Between equations:

S _oi ＝－0.39ln(K _egi )－1.105

The specific process is as follows:

①Obtain natural gas, condensate oil and formation water produced by the wellhead of a condensate gas reservoir;

②Calculate the core pore volume V=0.25πLD ² φ=24.9ml, inject formation water with a volume of 24.9ml into the core;

③Inject condensate oil into the core at the inlet of the core until no water comes out at the outlet of the core, and measure the accumulated water volume V _w (16ml), which is the initial saturated oil volume V _o ; calculate the irreducible water saturation S _or = 100%×(V-V _w )/V=35.7%, the initial oil saturation S _o in the core is determined to be 100%×(1-0.357)=64.3%;

④Inject natural gas into the core from the inlet of the core, record the pressure P _1i at the inlet of the core, the pressure P _2i at the outlet of the core, the gas volume V _gi (ml) at the outlet of the core, and the oil volume V _oi (ml) at every interval of 1200s, and calculate the Heart oil saturation S _oi = 100% × (V _o - V _oi )/V _o ;

⑤ Calculation of gas phase effective permeability K _egi under the condition of corresponding oil saturation S _oi :

⑥ Analyze the relationship between oil saturation S _oi and gas phase effective permeability (K _egi ) in the rock, and determine the coefficients a and b in S _oi =aln(K _egi )+b, as shown in Figure 1;

(3) According to the industry standard SY/T 5542-2000, prepare formation fluid samples with reference to the dew point pressure (34MPa) and single degassed oil ratio (3010m ³ /m ³ ) in the gas reservoir original formation fluid property analysis report;

(4) Use the same core, saturated with formation water, gradually increase the temperature and pressurize until the pore pressure and temperature of the core are consistent with the original formation pressure and temperature of the gas reservoir, and the radial pressure Pd applied to the core is _3MPa higher than the pore pressure _Pf , Then inject prepared formation fluid samples into the core, and test the gas-oil ratio GOR ₂ at the outlet end of the core every 0.5 hours until the GOR ₂ (3008m ³ /m ³ ) is consistent with GOR ₁ (3010m ³ /m ³ ) by 4 times the pore volume ;

(5) _Simulate the depletion process of the gas reservoir, and gradually reduce the _pore pressure in the core by discharging the formation fluid in the core. Decrease speed (1MPa/h) to reduce core outlet pressure P _2i to reduce core pore pressure, and record corresponding core inlet pressure P _1i and released gas volume V _gi at every interval △t ₂ (3600s) until P _2i is reduced to gas reservoir abandonment pressure;

(6) According to core diameter D, length L, inlet port pressure P _1i , outlet port pressure P _2i , time interval △t ₂ , outlet port gas volume V _gi , according to Darcy's formula Calculate the gas phase effective permeability K _fegi under the condition of average pressure P _i (0.5×(P _1i +P _2i )) during the core depletion experiment (as shown in Fig. 2);

(7) Bring K _fegi into S _oi = aln(K _egi )+b, calculate the condensate oil saturation S _oi under reservoir conditions, and draw the relationship between pressure P _i and S _oi , so as to determine the Inverse condensate oil saturation (as shown in Figure 3).

Claims (3)

1. The depletion method for determining the reverse condensate oil saturation in sandstone condensate gas reservoirs includes the following steps in sequence: (1) Obtain the core of the actual reservoir, clean and dry it, and test the diameter D, length L, permeability K ₀ , and porosity φ; (2) Test the gas phase effective permeability K _egi under different oil saturation S _oi conditions, and determine the values of parameters a and b in the formula S _oi =aln(K _egi )+b, the specific process is as follows: ① Obtain the natural gas, condensate oil and formation water produced by the wellhead of the actual condensate gas reservoir; ②Calculate the core pore volume V=0.25πLD ² φ, and inject formation water with a volume of V (ml) into the core to saturate it; ③Inject condensate oil into the core from the inlet end of the core until no water comes out from the outlet end of the core, measure and accumulate the volume of water produced V _w , this volume is the initial saturated oil volume V _o , calculate the irreducible water saturation S _or =(V－ V _w )/V×100%, determine the initial oil saturation in the core S _o =(1-S _or )×100%; ④ Inject natural gas from the core inlet to the core, record the pressure P _1i at the core inlet, P _2i at the outlet, V _gi and V _oi at the outlet of the core at every interval △t ₁ , and calculate the oil saturation in the core S _oi = (V _o -V _oi )/V _o ×100%; ⑤ Calculate the gas phase effective permeability K _egi under the condition of corresponding oil saturation S _oi of the core: <mrow><msub><mi>K</mi><mrow><mi>e</mi><mi>g</mi><mi>i</mi></mrow></msub><mo>=</mo><mfrac><mrow><mo>(</mo><msub><mi>V</mi><mrow><mi>g</mi><mi>i</mi></mrow></msub><mo>/</mo><msub><mi>&amp;Delta;t</mi><mn>1</mn></msub><mo>)</mo><msub><mi>&amp;mu;</mi><mrow><mi>g</mi><mi>i</mi></mrow></msub><mi>L</mi></mrow><mrow><mn>10</mn><mi>A</mi><mrow><mo>(</mo><msubsup><mi>P</mi><mrow><mn>1</mn><mi>i</mi></mrow><mn>2</mn></msubsup><mo>-</mo><msubsup><mi>P</mi><mrow><mn>2</mn><mi>i</mi></mrow><mn>2</mn></msubsup><mo>)</mo></mrow></mrow></mfrac></mrow> In the formula: μ _{gi —viscosity} of gas, mPa·s; L—core length, cm; A—core cross-sectional area, cm ² , A=0.25πD ² , D—core diameter, cm; ⑥ Analyze the relationship between the oil saturation S _oi in the core and the gas phase effective permeability K _egi , and determine the values of the coefficients a and b in the formula S _oi =aln(K _egi )+b; (3) Refer to the dew point pressure P _b and single degassed oil ratio GOR ₁ in the original formation fluid property analysis report of the gas reservoir to prepare formation fluid samples, that is, condensate gas samples; (4) The rock core is restored to the original reservoir state; (5) Reduce the pore pressure in the core by reducing the pressure P _2i at the outlet end of the core. During the decompression process, the radial pressure P _d of the core is always kept 3 MPa higher than the pore pressure P _f , and the pressure P at the inlet end of the core is recorded at every interval △t _{2 1i} , outlet pressure P _2i , gas output volume V _gi at the outlet of the core, until the pressure P _2i at the outlet of the core decreases to the abandoned pressure of the gas reservoir; (6) Calculate the gas phase effective permeability K _fegi under the average pressure P _i during the core depletion experiment according to the following formula: <mrow><msub><mi>K</mi><mrow><mi>e</mi><mi>g</mi><mi>i</mi></mrow></msub><mo>=</mo><mfrac><mrow><mo>(</mo><msub><mi>V</mi><mrow><mi>g</mi><mi>i</mi></mrow></msub><mo>/</mo><msub><mi>&amp;Delta;t</mi><mn>2</mn></msub><mo>)</mo><msub><mi>&amp;mu;</mi><mrow><mi>g</mi><mi>i</mi></mrow></msub><mi>L</mi></mrow><mrow><mn>10</mn><mi>A</mi><mrow><mo>(</mo><msubsup><mi>P</mi><mrow><mn>1</mn><mi>i</mi></mrow><mn>2</mn></msubsup><mo>-</mo><msubsup><mi>P</mi><mrow><mn>2</mn><mi>i</mi></mrow><mn>2</mn></msubsup><mo>)</mo></mrow></mrow></mfrac><mo>;</mo></mrow> (7) Bring the K _fegi corresponding to each P _i point into S _oi =aln(K _egi )+b, and calculate the different pressures in the sandstone condensate gas reservoir according to the values of a and b determined in step (2). Reverse condensate oil saturation S _oi under the condition. 2. the method for determining the reverse condensate oil saturation in the depletion type development sandstone condensate gas reservoir reservoir as claimed in claim 1, is characterized in that, described step (4) core is restored to original reservoir state, concrete process It is: saturate it with formation water, then gradually raise the temperature and pressurize until the core pore pressure and temperature are consistent with the original formation pressure and temperature of the gas reservoir, the radial pressure P _d applied to the core is 3 MPa higher than the pore pressure P _f , and then The prepared formation fluid samples were injected into the core, and the gas-oil ratio GOR ₂ at the outlet end of the core was tested every 0.5 hours until it was consistent with GOR ₁ . 3. the depletion type development sandstone condensate gas reservoir reservoir as claimed in claim 1 is characterized in that, said step (6) average pressure P _i is rock core inlet port pressure P _i And the average value of the outlet pressure P _2i .