A method for calculating the dynamic reserves of deep-water gas reservoirs

Abstract

This invention relates to the technical field of natural gas development, and more specifically, to a method for calculating the dynamic reserves of deep-water gas reservoirs. The method includes: acquiring basic information about the target well; establishing a dynamic reserve calculation equation for the deep-water gas reservoir; correcting the dynamic reserve calculation equation for the deep-water gas reservoir; and solving the corrected dynamic reserve calculation equation for the deep-water gas reservoir. This invention obtains the dynamic reserve calculation equation for deep-water gas reservoirs by establishing a material balance equation for a finite, enclosed water body. Furthermore, considering the complex phase changes present in deep-water gas reservoir development, the dynamic reserve calculation equation for deep-water gas reservoirs is corrected from five aspects: condensate water, anti-condensate, dissolved gas, rock skeleton expansion, and formation water intrusion. After obtaining the corrected dynamic reserve calculation equation, solving the corrected dynamic reserve calculation equation allows for a more accurate calculation of the dynamic reserves of deep-water gas reservoirs.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of natural gas development, and more particularly to a deepwater gas reservoir dynamic reserve calculation method. BACKGROUND

[0002] The dynamic reserve refers to the total amount of natural gas that can be produced when all production wells produce to zero pressure drop based on the existing production process and mode. There are many existing methods for determining the dynamic reserve, which can be mainly divided into three categories according to different calculation principles: the first method is to calculate the dynamic reserve by using static pressure data based on the material balance principle; the second method is to calculate the dynamic reserve by using flow pressure data based on the gas seepage law; and the third method is to estimate the dynamic reserve by predicting the change of gas well production based on the production law of gas reservoirs. The first method is relatively simple and has high precision, and requires the shut-in well to restore to static pressure. Deepwater gas reservoirs are subject to development costs, and the formation pressure is generally good, so the time for the formation pressure to recover to static pressure is short, and therefore the first method is more practical. The second method is relatively complex, and commercial software is generally used. In addition, clear understanding of the formation permeability, reservoir distribution and heterogeneity, and skin factor of the gas well is required, so that the model can be reasonably selected to avoid multiple solutions. The third method has strong dependence on the production law, and has good effect on ideal homogeneous gas reservoirs in the decline period, but sometimes has large error when applied to actual gas reservoirs.

[0003] The material balance method has high applicability in deepwater gas reservoirs in terms of calculation principle and convenience. However, there is another difficulty in determining the dynamic reserve of deepwater gas reservoirs. Deepwater gas reservoirs are generally developed by using a unique method of combining a subsea wellhead with a sea pipe in series. The sea pipe is surrounded by seawater on the seabed, and the gas reservoir fluid needs to be transported through a long distance of sea pipe to reach the platform. The fluid is affected by the large change of environmental temperature and pressure, and there is a certain gap between the metering data on the platform and the gas reservoir environment, resulting in large calculation error of the dynamic reserve of deepwater gas reservoirs. SUMMARY

[0004] The present application aims to overcome the large calculation error of the dynamic reserve of deepwater gas reservoirs in the prior art, and provides a deepwater gas reservoir dynamic reserve calculation method, which can make the calculation of the dynamic reserve of deepwater gas reservoirs more accurate.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0006] A deepwater gas reservoir dynamic reserve calculation method is provided, comprising the following steps:

[0007] Obtaining basic information of the target well: obtaining field data and experimental data of the target well;

[0008] Establishing a deepwater gas reservoir dynamic reserve calculation equation: establishing a deepwater gas reservoir dynamic reserve calculation equation through a material balance equation of a limited closed water body;

[0009] modifying the deepwater gas reservoir dynamic reserve calculation equation, the deepwater gas reservoir dynamic reserve calculation equation is modified considering the effects of condensate water, retrograde condensation, water-soluble gas, rock skeleton expansion and formation water invasion on the deepwater gas reservoir, and a modified deepwater gas reservoir dynamic reserve calculation equation is obtained;

[0010] solving the modified deepwater gas reservoir dynamic reserve calculation equation, the modified deepwater gas reservoir dynamic reserve calculation equation is solved through the field data and the experimental data, and the deepwater gas reservoir dynamic reserve is obtained.

[0011] The deepwater gas reservoir dynamic reserve calculation method of the present application is improved on the basis of the traditional material balance method in view of the characteristics that the deepwater gas reservoir is affected by the stable pressure change of the environment and there is a certain gap between the metering data of the platform and the gas reservoir environment, a material balance equation of a limited closed water body is established to obtain a deepwater gas reservoir dynamic reserve calculation equation, and the deepwater gas reservoir dynamic reserve calculation equation is further modified from five aspects of condensate water, retrograde condensation, water-soluble gas, rock skeleton expansion and formation water invasion in view of the complex phase change existing in the development of the deepwater gas reservoir, and the modified deepwater gas reservoir dynamic reserve calculation equation is solved, so that the calculation of the deepwater gas reservoir dynamic reserve is more accurate.

[0012] Preferably, the field data specifically include wellhead natural gas production, pressure at standard condition, temperature at standard condition, pressure under original gas reservoir condition, temperature under original gas reservoir condition, pressure under current gas reservoir condition and temperature under current gas reservoir condition.

[0013] Preferably, the experimental data specifically include water body multiple, content of salt in produced water, natural gas volume coefficient in the gas reservoir under original state, natural gas volume coefficient in the gas reservoir under current state, deviation factor at standard condition, deviation factor under original gas reservoir condition, deviation factor under current gas reservoir condition, rock pore volume compression coefficient, formation water compression coefficient, formation water volume coefficient, irreducible water saturation and formation water volume in the gas reservoir except condensate water.

[0014] Preferably, the deepwater gas reservoir dynamic reserve calculation equation is specifically as follows:

[0015]

[0016] wherein, is the deepwater gas reservoir dynamic reserve, and the unit is m 3 ; is the gas reservoir natural gas production, and the unit is m 3 ; is the gas reservoir natural gas remaining amount, and the unit is m 3 ; is the pore volume occupied by the remaining gas in the current state, in m 3 ; is the gas volume factor in the gas reservoir in the current state, dimensionless.

[0017] Preferably, the modified deepwater gas reservoir dynamic reserve calculation equation is specifically as follows:

[0018]

[0019] wherein, is the deepwater gas reservoir dynamic reserve, in m 3 ; is the remaining amount of gas in the gas reservoir, in m 3 ; is the wellhead natural gas production, in m 3 ; is the volume change amount caused by condensate water, in m 3 ; is the gas volume factor in the gas reservoir in the current state, dimensionless; is the pore volume occupied by the remaining gas in the original state of the gas reservoir, in m 3 ; is the volume change amount caused by rock skeleton expansion, in m 3 ; is the volume change amount caused by formation water invasion, in m 3 ; is the volume change amount caused by water-soluble gas, in m 3 ; is the volume change amount caused by retrograde condensation, in m 3 .

[0020] Preferably, the relationship between the volume of the gas reservoir in the original state and the production and the equation of state are introduced to simplify the modified deepwater gas reservoir dynamic reserve calculation equation, and the following formula is used for simplification:

[0021]

[0022] to obtain the simplest deepwater gas reservoir dynamic reserve calculation equation, which is specifically as follows:

[0023]

[0024] wherein, is the gas volume factor in the gas reservoir in the original state, dimensionless; is the pressure under standard conditions, in MPa; is the deviation factor under standard conditions, dimensionless; is the temperature under standard conditions, in K; Poi is the pressure under the original gas reservoir condition, in MPa; Zoi is the deviation factor under the original gas reservoir condition, dimensionless; T0i is the temperature under the original gas reservoir condition, in K; P0 is the pressure under the current gas reservoir condition, in MPa; Z0 is the deviation factor under the current gas reservoir condition, dimensionless; T0 is the temperature under the current gas reservoir condition, in K.

[0025] Preferably, the trial-and-error method and the image method are used to solve the simplest deepwater gas reservoir dynamic reserve calculation equation, and the specific process is as follows:

[0026] Step one: parameter replacement is performed on the simplest deepwater gas reservoir dynamic reserve calculation equation, specifically as follows:

[0027]

[0028] Wherein, A, B and C are constants;

[0029] Step two: assuming , formula (2) is solved to obtain the values of A, B and C;

[0030] Step three: taking A as the vertical coordinate, as the horizontal coordinate, a graph of formula (1) is drawn;

[0031] Step four: the value of the intersection point of the graph of formula (1) and the horizontal coordinate is ;

[0032] Step five: when the is not equal to the , the value of is assigned to , and the cycle starts from step two until the is equal to the , and this is the solution of the simplest deepwater gas reservoir dynamic reserve calculation equation. By using the trial-and-error method and the image method to solve the simplest deepwater gas reservoir dynamic reserve calculation equation, the deepwater gas reservoir dynamic reserve can be calculated more conveniently and intuitively.

[0033] Preferably, the volume change amount caused by condensate water is calculated by the following formula:

[0034]

[0035] Wherein, is the volume change amount caused by condensate water, in m 3 ; is the wellhead natural gas production, in m 3 ; is the condensate water ratio, in m 3 / 10 4 m 3 ; is the correction coefficient, dimensionless; is the current gas reservoir pressure, in MPa; is the current gas reservoir temperature, in K; is the salt content correction coefficient, dimensionless; is the salt content in the produced water, in %; C and D are constants. The correction coefficient is used to correct the volume change caused by condensate water, so that the calculation result of the deepwater gas reservoir dynamic reserves is more in line with the actual situation, thereby enabling the calculation of deepwater gas reservoir dynamic reserves to be more accurate.

[0036] Preferably, the volume change caused by the rock skeleton expansion is specifically calculated by the following formula:

[0037]

[0038] wherein, is the volume change caused by the rock skeleton expansion, in m 3 ; is the gas reservoir pore volume, in m 3 ; is the rock pore volume compression coefficient, in MPa -1 ; is the gas reservoir pressure drop, in MPa; is the deepwater gas reservoir dynamic reserves, in m 3 ; is the irreducible water saturation, dimensionless; is the original gas reservoir pressure, in MPa; is the current gas reservoir pressure, in MPa.

[0039] Preferably, the volume change caused by the formation water invasion is specifically calculated by the following formula:

[0040]

[0041] wherein, is the volume change caused by the formation water invasion, in m 3 ; is the formation water volume in the gas reservoir, in m 3 ; is the formation water compression coefficient, in MPa -1 ; is the pressure drop of the gas reservoir, and the unit is MPa; is the formation water volume of the gas reservoir except for condensate water, and the unit is m 3 ; is the formation water volume coefficient, and the unit is dimensionless; is the pore volume of the gas zone in the gas reservoir, and the unit is m 3 ; is the irreducible water saturation, and the unit is dimensionless; is the pore volume of the water zone in the gas reservoir, and the unit is m 3 ; is the water body multiple, and the unit is dimensionless; is the pressure under the original gas reservoir condition, and the unit is MPa; is the pressure under the current gas reservoir condition, and the unit is MPa; is the pore volume of the gas reservoir, and the unit is m 3 ; is the dynamic reserve of the deepwater gas reservoir, and the unit is m 3 .

[0042] Compared with the prior art, the beneficial effects of the present application are:

[0043] 1. The deepwater gas reservoir dynamic reserve calculation method of the present application is improved on the basis of the traditional material balance method according to the characteristics that the deepwater gas reservoir will be affected by the environmental pressure change, there is a certain gap between the platform measurement data and the gas reservoir environment, the material balance equation of the limited closed water body is established, the deepwater gas reservoir dynamic reserve calculation equation is obtained, and the deepwater gas reservoir development is further considered. The complex phase change exists, the deepwater gas reservoir dynamic reserve calculation equation is modified from five aspects of condensate water, reverse condensation, water-soluble gas, rock skeleton expansion and formation water invasion, and the modified deepwater gas reservoir dynamic reserve calculation equation is obtained. The deepwater gas reservoir dynamic reserve calculation equation is solved, which can make the calculation of the deepwater gas reservoir dynamic reserve more accurate.

[0044] 2. The deepwater gas reservoir dynamic reserve calculation method of the present application can more conveniently and intuitively calculate the deepwater gas reservoir dynamic reserve by using the trial method and the image method to solve the simplest deepwater gas reservoir dynamic reserve calculation equation. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is the flow chart of the deepwater gas reservoir dynamic reserve calculation method;

[0046] Figure 2 is the solving schematic diagram of solving the deepwater gas reservoir dynamic reserve in example four. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application.

[0048] Embodiment one

[0049] The present embodiment is a first embodiment of a deepwater gas reservoir dynamic reserve calculation method, as shown in the following steps: Figure 1

[0050] Target well basic information acquisition: acquiring field data and experimental data of the target well;

[0051] Establishing a deepwater gas reservoir dynamic reserve calculation equation: a deepwater gas reservoir dynamic reserve calculation equation is established through a material balance equation of a limited closed water body; the deepwater gas reservoir dynamic reserve calculation equation is an improvement on a traditional material balance equation, and the material balance equation is established from the phase state change of the limited closed water body.

[0052] Correcting the deepwater gas reservoir dynamic reserve calculation equation: the deepwater gas reservoir dynamic reserve calculation equation is corrected by considering the influence of condensate water, retrograde condensation, water-soluble gas, rock skeleton expansion and formation water invasion on the deepwater gas reservoir, so as to obtain a corrected deepwater gas reservoir dynamic reserve calculation equation; in the correction, the result deviation caused by the phase state change of natural gas due to condensate water, retrograde condensation and water-soluble gas is mainly considered.

[0053] Solving the corrected deepwater gas reservoir dynamic reserve calculation equation: the corrected deepwater gas reservoir dynamic reserve calculation equation is solved through field data and experimental data, so as to obtain the deepwater gas reservoir dynamic reserve.

[0054] The working principle of the deepwater gas reservoir dynamic reserve calculation method of the present embodiment is as follows:

[0055] The present application is mainly applicable to a limited closed water body deepwater gas reservoir with complex phase state changes. In view of the characteristics that the deepwater gas reservoir will be affected by the stable pressure change of the environment, there is a certain gap between the metering data of the platform and the gas reservoir environment, the traditional material balance method is improved, the material balance equation of the limited closed water body is established, the deepwater gas reservoir dynamic reserve calculation equation is obtained, the complex phase state changes existing in the development of the deepwater gas reservoir are further considered, the deepwater gas reservoir dynamic reserve calculation equation is corrected from five aspects of condensate water, retrograde condensation, water-soluble gas, rock skeleton expansion and formation water invasion, the corrected deepwater gas reservoir dynamic reserve calculation equation is solved, and the calculation of the deepwater gas reservoir dynamic reserve is more accurate.

[0056] Embodiment two

[0057] ​The deep water gas reservoir dynamic reserve calculation method provided in the embodiment is based on the embodiment one, in the embodiment, the field data specifically includes wellhead natural gas output, pressure under standard condition, temperature under standard condition, pressure under original gas reservoir condition, temperature under original gas reservoir condition, pressure under current gas reservoir condition and temperature under current gas reservoir condition; the original gas reservoir condition is the condition before the oil and gas field is exploited, and the current gas reservoir condition is the condition when the measurement is performed after exploitation.

[0058] The field data of the target well is acquired, and the specific steps are as follows: the target well is closed, and the formation is restored to static pressure, which can ensure that the measurement of the field data is performed under the same pressure condition each time, and can improve the accuracy of the deep water gas reservoir dynamic reserve; the measurement is performed on the target well by a measurement device, that is, the measurement is performed by a series of technical means such as fluid meter, logging and geophysics at the oil and gas field production site; and the field data is obtained.

[0059] The experimental data specifically includes water multiple, content of salt in output water, natural gas volume coefficient in the gas reservoir under original state, natural gas volume coefficient in the gas reservoir under current state, deviation factor under standard condition, deviation factor under original gas reservoir condition, deviation factor under current gas reservoir condition, rock pore volume compression coefficient, formation water compression coefficient, formation water volume coefficient, irreducible water saturation and formation water volume in the gas reservoir except condensate water;

[0060] The experimental data of the target well is acquired, in the embodiment, the experimental data mainly refers to parameters that cannot be directly measured and provided at the oil and gas field production site, and the parameters are obtained by using experiments and related calculation formulas, and the specific steps are as follows: the material of the target well is collected; the material is analyzed by using experimental equipment, mainly the measured gas component is analyzed and calculated; and the experimental data is obtained.

[0061] The deep water gas reservoir dynamic reserve calculation equation specifically is as follows:

[0062]

[0063] wherein, is the deep water gas reservoir dynamic reserve, and the unit is m 3 ; is the gas reservoir natural gas output, and the unit is m 3 ; is the gas reservoir natural gas remaining amount, and the unit is m 3 ; is the pore volume occupied by the remaining gas under current state, and the unit is m 3 ; is the natural gas volume coefficient in the gas reservoir under current state, and is dimensionless.

[0064] The modified deepwater gas reservoir dynamic reserve calculation equation is as follows:

[0065]

[0066] wherein, is the deepwater gas reservoir dynamic reserve, unit is m 3 ; is the gas reservoir remaining gas, unit is m 3 ; is the wellhead natural gas production, unit is m 3 ; is the volume change amount caused by condensate water, unit is m 3 ; is the gas volume coefficient in the gas reservoir under the current state, dimensionless; is the remaining gas occupying pore volume under the original state, unit is m 3 ; is the volume change amount caused by rock skeleton expansion, unit is m 3 ; is the volume change amount caused by formation water invasion, unit is m 3 ; is the volume change amount caused by water-soluble gas, unit is m 3 ; is the volume change amount caused by reverse condensation, unit is m 3 .

[0067] The relationship between the gas reservoir volume and the production under the original gas reservoir state and the state equation are introduced, and the modified deepwater gas reservoir dynamic reserve calculation equation is simplified, and the following formula is used for simplification:

[0068]

[0069] The simplest deepwater gas reservoir dynamic reserve calculation equation is obtained, and is as follows:

[0070]

[0071] wherein, is the gas volume coefficient in the gas reservoir under the original state, dimensionless; is the pressure under the standard condition, unit is MPa; is the deviation factor under the standard condition, dimensionless; is the temperature under the standard condition, unit is K; is the pressure under the original gas reservoir condition, unit is MPa; is the deviation factor under the original gas reservoir condition, dimensionless; is the temperature under the original gas reservoir condition, unit is K; P is the current gas reservoir pressure, unit: MPa; B is the current gas reservoir bias factor, dimensionless; T is the current gas reservoir temperature, unit: K.

[0072] To obtain the volume change amount of the formation natural gas caused by the condensate water due to phase change in the production process, the gas well water production can be analyzed, and the condensate water production is converted to the volume under the temperature and pressure conditions of the gas reservoir. There are many methods to determine the content of natural gas condensate water, such as experimental determination, chart determination, state equation calculation and empirical formula method. Experimental determination is time-consuming and costly; chart determination is tedious and prone to human error; state equation calculation is based on oil-gas-water multiphase equilibrium theory and fluid thermodynamics balance principle, and the calculation process is complex; empirical formula is obtained by regression according to the measured data, although the calculation is simple and convenient, but due to the great difference of natural gas components in different regions, the use of empirical formula has limitations. Combining the characteristics of the above methods, the present application adopts empirical formula regression based on experiment, if there is no experimental condition, the appropriate formula can be selected according to the characteristics of natural gas components in the gas reservoir, in the embodiment, the volume change amount caused by condensate water is calculated by the following formula:

[0073]

[0074] Wherein, The volume change amount caused by condensate water is m 3 ; The wellhead natural gas production is m 3 ; The condensate water gas ratio is m 3 / 10 4 m 3 ; The correction coefficient is dimensionless; P is the current gas reservoir pressure, unit: MPa; T is the current gas reservoir temperature, unit: K. The salt content correction coefficient is dimensionless; The content of salt in the produced water is in percentage, the produced water is the water produced in addition to the condensate water, including formation water and movable water; C and D are constants. The correction coefficient is obtained by comparing the calculated value with the actual value after simulating the water-gas ratio data in the early stage of actual production, when the water-gas ratio is stable and the chloride content is low, and at the same time, the correction coefficient can be used to convert the condensate water production to the temperature and pressure conditions of the gas reservoir. The volume change amount caused by condensate water is corrected by using the correction coefficient, so that the calculation result of the dynamic reserves of the deepwater gas reservoir is more in line with the actual situation, so that the calculation of the dynamic reserves of the deepwater gas reservoir is more accurate.

[0075] The volume change amount caused by the expansion of the rock skeleton is calculated by the following formula:

[0076]

[0077] wherein, The volume change amount caused by the expansion of the rock skeleton is in m 3 ; The pore volume of the gas reservoir is in m 3 ; The rock pore volume compression coefficient is in MPa -1 ; The pressure drop of the gas reservoir is in MPa; The dynamic reserves of the deepwater gas reservoir are in m 3 ; The irreducible water saturation is dimensionless; The pressure under the original gas reservoir conditions is in MPa; The pressure under the current gas reservoir conditions is in MPa.

[0078] The volume change amount caused by the invasion of formation water is calculated by the following formula:

[0079]

[0080] wherein, The volume change amount caused by the invasion of formation water is in m 3 ; The volume of formation water in the gas reservoir is in m 3 ; The formation water compression coefficient is in MPa -1 ; The pressure drop of the gas reservoir is in MPa; The volume of formation water produced in addition to condensate water in the gas reservoir is in m 3 ; The formation water volume coefficient is dimensionless; The pore volume of the gas-bearing zone in the gas reservoir, in cubic meters (m³). 3 ; To constrain water saturation, it is dimensionless; This refers to the pore volume of the water zone in a gas reservoir, expressed in cubic meters (m³). 3 ; It is a multiple of the water volume and has no dimension. This represents the pressure under the original gas reservoir conditions, expressed in MPa. This represents the pressure under current gas reservoir conditions, expressed in MPa. This refers to the pore volume of the gas reservoir, in meters (m³). 3 ; Dynamic reserves of deep-water gas reservoirs, in cubic meters (m³). 3 .

[0081] Determining the amount of natural gas released from dissolved formation water essentially involves solving a phase equilibrium problem between the gas and water phases. The theoretical basis for this problem is Henry's law, which is often modified using the Krichevsky-Kasarnovsky equation under high-pressure conditions. The volume change caused by dissolved gas in water is calculated using the equation of state method, primarily based on the reservoir's pressure stability, the composition of water, and the composition of gas. In practical applications, the effectiveness of the equation of state varies significantly due to differences in temperature and pressure conditions, gas composition, and formation water properties. When the calculated value differs greatly from the experimental value, it is necessary to change the equation of state or adjust the Henry's constant to recalculate the amount of dissolved natural gas.

[0082] During production, gas reservoirs follow the laws of gas seepage, and the pressure distribution around the gas well exhibits a funnel shape, meaning the pressure drop is greater near the well and smaller further away. When the pressure drops below the dew point pressure, reverse condensation occurs in the gas reservoir. The amount of reverse condensation in the reservoir is closely related to the pressure distribution range. The volume change caused by reverse condensation is calculated using numerical simulation. Based on a component model, historical data is fitted to predict the formation pressure distribution and corresponding oil saturation during production, thus obtaining the amount of residual condensate oil precipitated in the gas reservoir.

[0083] After solving for the above unknowns, the simplest equation for calculating the dynamic reserves of deep-water gas reservoirs is solved using a trial-and-error method and a graphical method. The specific process is as follows:

[0084] Step 1: Perform parameter replacement on the simplified deep-water gas reservoir dynamic reserve calculation equation, specifically as follows:

[0085]

[0086] Where A, B, and C are constants;

[0087] Step Two: Assumption Solve formula (2) to obtain the values ​​of A, B and C;

[0088] Step 3: Plot A as the ordinate, Use the x-axis to plot the graph of formula (1);

[0089] Step 4: The value of the intersection point of the graph of formula (1) and the horizontal axis is... ;

[0090] Step 5: When the above With the Indefinitely The value assigned to The process repeats from step two until the aforementioned... With the Equal, that This is the solution to the simplified equation for calculating the dynamic reserves of deep-water gas reservoirs. By using a trial-and-error method and a graphical method to solve the simplified equation for calculating the dynamic reserves of deep-water gas reservoirs, the dynamic reserves of deep-water gas reservoirs can be calculated more conveniently and intuitively.

[0091] Example 3

[0092] This embodiment applies a dynamic reserve calculation method for deep-water gas reservoirs to calculate the dynamic reserves of well A1 in a deep-water L gas field. Building upon embodiments one through three, this embodiment describes a lithological structural gas reservoir with only one producing well. Under the original reservoir conditions, the pressure is 39.35 MPa, the water volume ratio is 3.5, the bound water saturation is 0.257, and the rock pore volume compressibility coefficient is 9.16 × 10⁻⁶. -4 MPa -1 The formation water compressibility coefficient is 5.10 × 10⁻⁶. -4 MPa -1 The deviation factor under the original gas reservoir conditions was 1.11, the correction coefficient was 1.02, the deviation factor under standard conditions was 0.99, and the temperature was 92.6℃. The specific test data of this well are shown in Table 1.

[0093] Table 1 Well shut-in pressure testing and corresponding production data

[0094]

[0095] Using the simplest equation for calculating the dynamic reserves of deep-water gas reservoirs, a trial-and-error method and a graphical method are employed to solve the problem, assuming... Using the value of A, solve Formula 2 to obtain the values ​​of A, B, and C; plot the value of A on the ordinate, The value is the x-axis. Plot the graph according to Formula 1, as shown below. Figure 2 As shown; the intersection of the graph of Formula 1 and the horizontal axis is... The value; when The value and when the values of are not equal, the value of is assigned to , and the cycle is started from step two until the value of is equal to the value of , the value of is the solution of the equation for calculating the dynamic reserves of the deepwater gas reservoir, and the dynamic reserves of the deepwater gas reservoir is calculated to be 125.99 x 10 4 m 3 .

[0096] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, different embodiments or examples described in the present specification and the features of different embodiments or examples can be combined and combined by those skilled in the art without contradiction.

[0097] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the implementation manner of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, it is not necessary and impossible to exhaust all the implementation manners. Any modification, equivalent replacement and improvement, etc. within the spirit and principle of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A method for calculating dynamic reserves of a deep-water gas reservoir, characterized in that, The method comprises the following steps: Target well basic information acquisition: acquiring field data and experimental data of the target well; the field data specifically comprises wellhead natural gas output, pressure under standard condition, temperature under standard condition, pressure under original gas reservoir condition, temperature under original gas reservoir condition, pressure under current gas reservoir condition and temperature under current gas reservoir condition; the experimental data specifically comprises water multiple, content of salt in output water, natural gas volume coefficient under original state in gas reservoir, natural gas volume coefficient under current state in gas reservoir, deviation factor under standard condition, deviation factor under original gas reservoir condition, deviation factor under current gas reservoir condition, rock pore volume compression coefficient, formation water compression coefficient, formation water volume coefficient, irreducible water saturation and formation water volume except condensate water in gas reservoir; Establishing a deep water gas reservoir dynamic reserve calculation equation: a deep water gas reservoir dynamic reserve calculation equation is established through a material balance equation of a limited closed water body; the deep water gas reservoir dynamic reserve calculation equation is specifically as follows: wherein, is the dynamic reserves of the deep-water gas reservoir, in m 3 ; is the gas production of the gas reservoir, in m 3 ; is the remaining gas of the gas reservoir, in m 3 ; is the pore volume occupied by the remaining gas under the current state, in m 3 ; is the gas volume factor in the gas reservoir under the current state, dimensionless; Amending the deep water gas reservoir dynamic reserve calculation equation: the deep water gas reservoir dynamic reserve calculation equation is amended by considering the influence of condensate water, retrograde condensation, water-soluble gas, rock skeleton expansion and formation water invasion on the deep water gas reservoir, so as to obtain an amended deep water gas reservoir dynamic reserve calculation equation; Solving the amended deep water gas reservoir dynamic reserve calculation equation: the amended deep water gas reservoir dynamic reserve calculation equation is solved through the field data and the experimental data, so as to obtain a deep water gas reservoir dynamic reserve.

2. The method of claim 1, wherein, The amended deep water gas reservoir dynamic reserve calculation equation is specifically as follows: wherein, is the dynamic reserves of the deep-water gas reservoir, in m 3 ; is the remaining amount of natural gas in the gas reservoir, in m 3 ; is the wellhead natural gas production, in m 3 ; is the volume change amount due to condensate water, in m 3 ; is the volume coefficient of natural gas in the gas reservoir under the current state, dimensionless; is the pore volume occupied by the remaining gas under the original state, in m 3 ; is the volume change amount due to rock skeleton expansion, in m 3 ; is the volume change amount due to formation water invasion, in m 3 ; is the volume change amount due to water-soluble gas, in m 3 ; is the volume change amount due to retrograde condensation, in m 3 .

3. The method of claim 2, wherein, Introducing a relationship between gas reservoir volume under original gas reservoir condition and output and a state equation, simplifying the amended deep water gas reservoir dynamic reserve calculation equation, and specifically simplifying the equation by using the following formula: Obtaining a simplest deep water gas reservoir dynamic reserve calculation equation, which is specifically as follows: wherein, is the gas volume factor in the original state of the gas reservoir, dimensionless; is the pressure at standard conditions, in MPa; is the deviation factor at standard conditions, dimensionless; is the temperature at standard conditions, in K; is the pressure at the original gas reservoir conditions, in MPa; is the deviation factor at the original gas reservoir conditions, dimensionless; is the temperature at the original gas reservoir conditions, in K; is the pressure at the current gas reservoir conditions, in MPa; is the deviation factor at the current gas reservoir conditions, dimensionless; is the temperature at the current gas reservoir conditions, in K.

4. The method of claim 3, wherein, Solving the simplest deep water gas reservoir dynamic reserve calculation equation by using a trial method and an image method, and the specific process is as follows: Step one: parameter replacement is performed on the simplest deep water gas reservoir dynamic reserve calculation equation, which is specifically as follows: Wherein, A, B and C are constants; Step two: Hypothesis Solving equation (2) gives the values of A, B and C. Step three: plot equation (1) with A as the ordinate, and B as the abscissa. Step four: the value of the intersection of the graph of the formula (1) with the abscissa is ; Step five: when the is equal to the , the is assigned the value of the , the loop from step two is started until the is equal to the , the is the solution to the equation for the minimum dynamic reserve of a deep gas reservoir.

5. The method of calculating the dynamic reserves of a deep-water gas reservoir according to any one of claims 2 to 4, characterized in that, The volume change amount caused by condensate water is calculated by using the following formula: wherein, is the volume change amount due to condensate water, unit: m 3 ; is the wellhead natural gas production, unit: m 3 ; is the condensate water gas ratio, unit: m 3 / 10 4 m 3 ; is the correction coefficient, dimensionless; is the pressure under the current gas reservoir condition, unit: MPa; is the temperature under the current gas reservoir condition, unit: K; is the salt content correction coefficient, dimensionless; is the content of salt in the produced water, unit: %; C and D are constants.

6. The method of calculating the dynamic reserves of a deep-water gas reservoir according to any one of claims 2 to 4, characterized in that, The volume change amount caused by rock skeleton expansion is calculated by using the following formula: wherein, is the volume change due to the expansion of the rock matrix, in m 3 ; is the pore volume of the gas reservoir, in m 3 ; is the compressibility of the rock pore volume, in MPa -1 ; is the pressure drop of the gas reservoir, in MPa; is the dynamic reserve of the deepwater gas reservoir, in m 3 ; is the irreducible water saturation, dimensionless; is the pressure under the original gas reservoir conditions, in MPa; is the pressure under the current gas reservoir conditions, in MPa.

7. The method of calculating the dynamic reserves of a deep-water gas reservoir according to any one of claims 2 to 4, characterized in that, The volume change amount caused by formation water invasion is calculated by using the following formula: wherein, is the volume change due to the invasion of formation water, in m 3 ; is the volume of formation water in the gas reservoir, in m 3 ; is the compressibility of formation water, in MPa -1 ; is the pressure drop in the gas reservoir, in MPa; is the volume of formation water produced in the gas reservoir excluding condensate water, in m 3 ; is the formation water volume coefficient, dimensionless; is the pore volume of the gas zone in the gas reservoir, in m 3 ; is the irreducible water saturation, dimensionless; is the pore volume of the water zone in the gas reservoir, in m 3 ; is the water volume multiple, dimensionless; is the pressure under the original gas reservoir conditions, in MPa; is the pressure under the current gas reservoir conditions, in MPa; is the pore volume of the gas reservoir, in m 3 ; is the dynamic reserve of the deepwater gas reservoir, in m 3 .

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