Condensate gas reservoir gas-water interface calculation method considering gravity differentiation influence
The method addresses inaccuracies in gas-water interface prediction by incorporating gravity differentiation effects, enabling precise interface determination for improved reserve assessment and management in thick plate-like fracture-cavity condensate gas reservoirs.
Patent Information
- Application Number
- CN202311872703.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-29
- Publication Date
- 2024-12-13
AI Technical Summary
Existing mine gas-water interface calculation methods fail to account for fluid density variations due to gravity differentiation in thick plate-like fault-controlled fracture-cavity condensate gas reservoirs, leading to inaccuracies in interface position prediction.
A method that considers gravity differentiation by using temperature, pressure, and fluid component testing data, combined with a component gradient model and density difference method to determine the gas-water interface, involving steps like well flow component analysis, phase fitting, and reservoir numerical simulation.
Provides accurate prediction of the gas-water interface, supporting reserve assessment, well network construction, and water risk management in such reservoirs.
Smart Images
Figure CN119122513A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of water-gas interface in condensate gas reservoirs, and in particular to a method for calculating the gas-water interface in condensate gas reservoirs taking into account the influence of gravity differentiation. Background Art
[0002] The condensate gas reservoir type in the study area presents a thick plate-like feature, and the reservoir structure is controlled by strike-slip faults, with a thickness of 500-1200m and good vertical connectivity. The fluid distribution under formation conditions is significantly affected by the gravity differentiation characteristics, and the fluid density at different depths varies greatly.
[0003] Existing mine gas-water interface calculation methods fail to take into account changes in fluid density and assume that the fluid in the reservoir is a homogeneous medium. However, during the development of thick plate-like fault-controlled fracture-cavity condensate gas reservoirs, it was found that gravity differentiation caused obvious differences in the vertical density distribution of the fluid, resulting in a significant deviation between the gas-water interface position calculated by constant density and the actual position. The present invention fully considers the vertical density difference of condensate gas, uses temperature testing, pressure testing, fluid component testing data and other information, and combines the component gradient model and density difference method to determine the gas-water interface position of the condensate gas reservoir. Accurate prediction of the gas-water interface can provide favorable support for reserve assessment, well network construction, water risk warning and comprehensive water management of thick plate-like fault-controlled fracture-cavity condensate gas reservoirs. Summary of the invention:
[0004] In order to solve the problem that in the traditional mine gas-water interface calculation process, the gas-water interface position calculated by the traditional mine gas-water interface calculation method is inconsistent with the actual gas-water interface position of the giant thick plate-like fracture-cavity condensate gas reservoir because the fluid in the reservoir is regarded as a uniform medium without considering the change of gas reservoir density with depth, the present invention discloses a gas-water interface calculation method for condensate gas reservoirs considering the influence of gravity differentiation, and utilizes the longitudinal density difference of giant thick plate-like fracture-cavity condensate gas reservoirs, combined with temperature testing, pressure testing and fluid component testing to determine the gas-water interface position of the giant thick plate-like fracture-cavity condensate gas reservoir, so as to provide favorable support for reserve assessment, well network construction, water breakthrough risk warning and comprehensive water breakthrough management of giant thick plate-like fault-controlled fracture-cavity condensate gas reservoirs.
[0005] The specific plan is as follows:
[0006] A method for calculating the gas-water interface of a condensate gas reservoir taking into account the influence of gravity differentiation, characterized in that it comprises the following steps:
[0007] S1: obtaining the original formation pressure and the static water column pressure measured when the target condensate gas reservoir well is shut in during well testing, measuring the depth of the middle gas layer of the target condensate gas reservoir well, and obtaining the formation water density corresponding to the target condensate gas reservoir;
[0008] S2: Obtain condensate gas sample and perform well flow component analysis: Use a separator to obtain a condensate gas sample from the target condensate gas reservoir well in S1, perform well flow component analysis on the condensate gas sample to obtain the molar content of each well flow component in the condensate gas sample, and perform component splitting on similar components in each well flow component according to the molar content of each well flow component to obtain a combined component;
[0009] S3: Performing phase fitting on the condensate gas sample: Performing phase fitting on the condensate gas sample in S2 using the combined components in S2, wherein the phase fitting includes: constant mass expansion experiment fitting and isochoric depletion experiment fitting, inputting the combined components with an error of less than 5% in the phase fitting result into the reservoir numerical simulation system, inputting the formation depth into the reservoir numerical simulation system, and obtaining the fluid density at different depths;
[0010] S4: Calculate the gas-water interface position of the target condensate gas reservoir well using the original formation pressure, static water column pressure, middle depth of the gas layer of the target condensate gas reservoir well, formation water density, and density of condensate gas at different depths in S3.
[0011] Preferably, the process of splitting similar components in the well flow materials to obtain merged components is: using the molar mass of each well flow component to re-divide the well flow components into 8 merged components, and the 8 merged components include: N2, CH4, C1+, C3+, C5+, C7+, C11+, C17+, and their compositions are: N2, CH4, CO2 / C2, C3 / iC4 / Nc4, iC5 / nC5 / iC6 / nC6, C7 / C8 / C9 / C10, C11 / C12 / C13 / C14 / C15 / C16, C17 / C18C19...
[0012] Preferably, the fitting process of the constant mass expansion experiment is: measuring the relative volume variation with pressure data and the liquid phase saturation variation with pressure data of the condensate gas sample of constant mass at formation temperature, and using the relative volume variation with pressure data of the condensate gas sample to obtain the dew point pressure of the condensate gas sample.
[0013] Preferably, the data fitted by the isochoric depletion experiment include: data on the variation of the compressibility factor Z value with pressure, data on the variation of the gas-liquid two-phase compressibility factor with pressure, data on the variation of the component mole fraction with pressure, and data on the variation of the liquid phase saturation with pressure.
[0014] Preferably, the method for calculating the gas-water interface position of the target condensate gas reservoir well by using the original formation pressure, the static water column pressure, the middle depth of the gas layer of the target condensate gas reservoir well, the formation water density, and the density of the condensate gas at different depths in the formation described in S3 is:
[0015]
[0016] Among them, D gwc is the depth of the air-water interface, D g is the depth of the middle gas layer of the condensate gas well, P i is the original formation pressure, P wD is the net water column pressure, ρw is the density of formation water, ρ gi is the density of condensate gas at different depths.
[0017] Preferably, the data fitted by the isochoric depletion experiment include: data on the variation of the compressibility factor Z value with pressure, data on the variation of the gas-liquid two-phase compressibility factor with pressure, data on the variation of the component mole fraction with pressure, and data on the variation of the liquid phase saturation with pressure.
[0018] Preferably, the method for calculating the gas-water interface position of the target condensate gas reservoir well by using the original formation pressure, the static water column pressure, the middle depth of the gas layer of the target condensate gas reservoir well, the formation water density, and the density of the condensate gas at different depths in the formation described in S3 is:
[0019]
[0020] Preferably, the method for calculating the gas-water interface position of the target condensate gas reservoir well by using the original formation pressure, the static water column pressure, the middle depth of the gas layer of the target condensate gas reservoir well, the formation water density, and the density of the condensate gas at different depths in the formation described in S3 is:
[0021]
[0022] Preferably, the reservoir numerical simulation system of S3 is the Grading Test module in tNavigator software.
[0023] Beneficial effects:
[0024] The present invention provides a method for calculating the gas-water interface in a condensate gas reservoir affected by gravity differentiation, and uses temperature test, pressure test, fluid component test data and other information, combined with a component gradient model and a density difference method to determine the position of the gas-water interface in the condensate gas reservoir. Specifically, S1: Obtain the original formation pressure and static water column pressure measured when the target condensate gas reservoir well is shut in during well testing, and use the well testing data to calculate the position of the gas-water interface, making full use of existing resources, and combining the actual situation of the target condensate gas reservoir well to calculate the position of the gas-water interface, thereby improving calculation efficiency and accuracy; S2: Obtain condensate gas samples and perform well flow component analysis: By performing well flow component analysis on the condensate gas samples, the components in the condensate gas samples are re-divided and integrated to meet the component simulator's requirements for the number of components while improving computational efficiency; S3: Perform Phase state fitting: constant mass expansion experiment fitting and isochoric exhaustion experiment fitting are used to simulate the changes in the volume of the condensate gas reservoir and the composition of the well flow with pressure in the unexploited closed state and during exhaustion exploitation. At the same time, the dew point pressure of the condensate gas reservoir is obtained by constant mass expansion experiment, so as to provide a good experimental numerical basis for the later numerical calculation using PVT phase state experimental data; S4: The gas-water interface position of the target condensate gas reservoir well is calculated using the original formation pressure, static water column pressure, middle depth of the gas layer of the target condensate gas reservoir well, formation water density, and the density of the formation condensate gas at different depths described in S3. Therefore, the present invention utilizes the vertical density difference of the giant thick plate-like fracture-cavity condensate gas reservoir, and combines temperature testing, pressure testing and fluid component testing to determine the gas-water interface position of the giant thick plate-like fracture-cavity condensate gas reservoir. Accurate prediction of the gas-water interface can provide favorable support for the reserve assessment, well network construction, water risk warning and comprehensive water management of the giant thick plate-like fault-controlled fracture-cavity condensate gas reservoir. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 Flow chart of a method for calculating the gas-water interface in a condensate gas reservoir affected by gravity differentiation.
[0026] Figure 2 A merged component graph obtained after component splitting of similar components.
[0027] Figure 3 Curve diagram of fluid density variation at different depths.
[0028] Figure 4 The fitting diagram of the data of relative volume changing with pressure in the constant mass expansion experiment fitting
[0029] Figure 5 Data fitting diagram of liquid phase saturation changing with pressure in constant mass expansion experiment fitting.
[0030] Figure 6 Data fitting diagram of the compression factor Z value changing with pressure in the isovolumetric depletion experiment.
[0031] Figure 7 Data fitting diagram of the gas-liquid two-phase compressibility factor changing with pressure in the isochoric depletion experiment.
[0032] Figure 8 Data fitting diagram of liquid phase saturation changing with pressure in isochoric depletion experiment.
[0033] Fig. 9 Data fitting diagram of the change of component mole fraction with pressure in the isochoric depletion experiment. DETAILED DESCRIPTION
[0034] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.
[0035] A method for calculating the gas-water interface in a condensate gas reservoir taking into account the influence of gravity differentiation. The overall flow chart of the specific method is as follows: Figure 1 As shown, the specific steps are as follows:
[0036] S1: obtaining the original formation pressure and the static water column pressure measured when the target condensate gas reservoir well is shut in during well testing, measuring the depth of the middle gas layer of the target condensate gas reservoir well, and obtaining the formation water density corresponding to the target condensate gas reservoir;
[0037] S2: Obtain condensate gas sample and perform well flow component analysis: Use a separator to obtain a condensate gas sample from the target condensate gas reservoir well in S1, perform well flow component analysis on the condensate gas sample, and obtain the molar content of each well flow component in the condensate gas sample, as shown in Table 1, which is a table of molar content of each well flow component. According to the molar content of each well flow component, similar components in each well flow component are split to obtain a combined component, as shown in Table 1. Figure 2 As shown, this is a combined component diagram obtained after splitting the components of the well flow.
[0038] Table 1
[0039]
[0040]
[0041] S3: Perform phase fitting on condensate gas sample: Use the combined components in S2 to perform phase fitting on condensate gas sample in S2. Table 2 shows the basic data for phase fitting on condensate gas sample in S2. The phase fitting includes: constant mass expansion experiment fitting, isochoric depletion experiment fitting. The combined components with phase fitting result error less than 5% are input into the reservoir numerical simulation system (tNavigator). The phase fitting result error is the error between the calculated value and the actual fitting value. Enter the formation depth in the reservoir numerical simulation system to obtain the fluid density at different depths, such as Figure 3As shown, it is the fluid density map obtained at different depths. The formation depth input in the reservoir numerical simulation system includes the bottom depth of the target reservoir and the top depth of the target reservoir. Preferably, the reservoir numerical simulation system of S3 is the Grading Test module in the tNavigator software. That is, on the basis of phase state fitting, the Grading Test module in the tNavigator software is used to carry out phase state experimental simulation, and the density values at different depths can be obtained by inputting the formation thickness. Figure 3 The bottom depth of the target oil reservoir is 7500m, the top depth of the target oil reservoir is 8800m, and the fluid densities at different depths obtained include fluid densities corresponding to 10 different formation depths obtained at equal intervals between the bottom depth of the target oil reservoir and the top depth of the target oil reservoir.
[0042] Table 2
[0043]
[0044]
[0045] S4: Calculate the gas-water interface position of the target condensate gas reservoir well using the original formation pressure, static water column pressure, middle depth of the gas layer of the target condensate gas reservoir well, formation water density, and density of condensate gas at different depths in S3.
[0046] Preferably, the process of splitting the similar components in the well flow to obtain the combined components is: using the molar mass of each well flow component to re-divide the well flow components into 8 combined components, and the 8 combined components include: N2, CH4, C1+, C3+, C5+, C7+, C11+, C17+. Figure 2 (b), the eight combined components N2, CH4, C1+, C3+, C5+, C7+, C11+, and C17+ are composed of: N2, CH4, CO2 / C2, C3 / iC4 / Nc4, iC5 / nC5 / iC6 / nC6, C7 / C8 / C9 / C10, C11 / C12 / C13 / C14 / C15 / C16, C17 / C18C19…. Using the above data, tNavigator is used to carry out phase fitting of condensate gas reservoirs. Limited by the computing speed, the number of components in the current component simulator is generally required to be within the range of 4-8, so similar components need to be combined. Figure 2(a) and (b) show the component re-splitting in PVTi. Nitrogen is quite different from other components and is also treated as a separate component. Carbon dioxide has a low content and can be combined with the C2 component. At the same time, isomers can be combined as a single component. Components above C11 are rare and can be combined as additional components. Based on the above principles, the components are recombined and split, and the final number of components is 8, which meets the needs of fine simulation and does not make the calculation speed too slow.
[0047] Preferably, the process of the constant mass expansion experiment fitting is: measuring the relative volume variation with pressure data and the liquid phase saturation variation with pressure data of the condensate gas sample of constant mass at the formation temperature, and obtaining the dew point pressure of the condensate gas sample using the relative volume variation with pressure data of the condensate gas sample, such as Figure 4 and Figure 5 Shown are the data fitting diagrams of relative volume and liquid phase saturation changing with pressure in the constant mass expansion experiment fitting.
[0048] Preferably, the data fitted by isochoric depletion experiment include: data on the variation of compression factor Z value with pressure, data on the variation of gas-liquid two-phase compression factor with pressure, data on the variation of component mole fraction with pressure, data on the variation of liquid phase saturation with pressure, such as Figure 6 , Figure 7 , Figure 8 , Fig. 9 The data fitting diagrams of the compressibility factor Z value, gas-liquid two-phase compressibility factor, liquid phase saturation, and component mole fraction as a function of pressure in the isochoric depletion experiment are shown in FIG. Figure 6-Figure 9 The fitting of the calculated value and the fitted value shows that the various indicators are well fitted, among which the fitting errors of the gas-liquid two-phase compressibility factor and the component mole fraction are small. The fitting weights of the gas-liquid two-phase compressibility factor and the component mole fraction are increased during the fitting process. Therefore, the dew point pressure can be faithful to the measured data, and the PVT fitting effect is good, which can be used for subsequent numerical simulation research.
[0049] Preferably, the method for calculating the gas-water interface position of the target condensate gas reservoir well by using the original formation pressure, the static water column pressure, the middle depth of the gas layer of the target condensate gas reservoir well, the formation water density, and the density of the condensate gas at different depths in the formation described in S3 is:
[0050]
[0051] Among them, D gwc is the depth of the air-water interface, D g is the depth of the middle gas layer of the condensate gas well, P i is the original formation pressure, P wD is the net water column pressure, ρw is the density of formation water, ρgi is the density of condensate gas at different depths.
[0052] Preferably, the data fitted by the isochoric depletion experiment include: data on the variation of the compressibility factor Z value with pressure, data on the variation of the gas-liquid two-phase compressibility factor with pressure, data on the variation of the component mole fraction with pressure, and data on the variation of the liquid phase saturation with pressure.
[0053] Preferably, the method for calculating the gas-water interface position of the target condensate gas reservoir well by using the original formation pressure, the static water column pressure, the middle depth of the gas layer of the target condensate gas reservoir well, the formation water density, and the density of the condensate gas at different depths in the formation described in S3 is:
[0054]
[0055] Preferably, the method for calculating the gas-water interface position of the target condensate gas reservoir well by using the original formation pressure, the static water column pressure, the middle depth of the gas layer of the target condensate gas reservoir well, the formation water density, and the density of the condensate gas at different depths in the formation described in S3 is:
[0056]
[0057] It should be noted that the above-described specific implementations can enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way. Therefore, although this specification has described the invention in detail with reference to the drawings and embodiments, those skilled in the art should understand that the invention can still be modified or replaced by equivalents. In short, all technical solutions and improvements that do not deviate from the spirit and scope of the invention should be included in the protection scope of the patent for the invention.
Claims
1. A method for calculating the gas-water interface in a condensate gas reservoir taking into account the influence of gravity differentiation, characterized in that: The steps include: S1: obtaining the original formation pressure and the static water column pressure measured when the target condensate gas reservoir well is shut in during well testing, measuring the depth of the middle gas layer of the target condensate gas reservoir well, and obtaining the formation water density corresponding to the target condensate gas reservoir; S2: Obtain condensate gas sample and perform well flow component analysis: Use a separator to obtain a condensate gas sample from the target condensate gas reservoir well in S1, perform well flow component analysis on the condensate gas sample to obtain the molar content of each well flow component in the condensate gas sample, and perform component splitting on similar components in each well flow component according to the molar content of each well flow component to obtain a combined component; S3: Performing phase fitting on the condensate gas sample: Performing phase fitting on the condensate gas sample in S2 using the combined components in S2, wherein the phase fitting includes: constant mass expansion experiment fitting and isochoric depletion experiment fitting, inputting the combined components with an error of less than 5% in the phase fitting result into the reservoir numerical simulation system, inputting the formation depth into the reservoir numerical simulation system, and obtaining the fluid density at different depths; S4: Calculate the gas-water interface position of the target condensate gas reservoir well using the original formation pressure, static water column pressure, middle depth of the gas layer of the target condensate gas reservoir well, formation water density, and density of condensate gas at different depths in S3.
2. The method for calculating the gas-water interface of a condensate gas reservoir taking into account the influence of gravity differentiation according to claim 1 is characterized in that: The process of splitting similar components in the well flow materials to obtain merged components is as follows: using the molar mass of each well flow component to re-divide the well flow components into 8 merged components, the 8 merged components include: N2, CH4, C1+, C3+, C5+, C7+, C11+, C17+, and their compositions are: N2, CH4, CO2 / C2, C3 / iC4 / Nc4, iC5 / nC5 / iC6 / nC6, C7 / C8 / C9 / C10, C11 / C12 / C13 / C14 / C15 / C16, C17 / C18C19… 3. The method for calculating the gas-water interface in a condensate gas reservoir taking into account the influence of gravity differentiation according to claim 1 or 2, characterized in that: The fitting process of the constant mass expansion experiment is as follows: the relative volume variation with pressure data and the liquid phase saturation variation with pressure data of the condensate gas sample of constant mass are measured at the formation temperature, and the dew point pressure of the condensate gas sample is obtained using the relative volume variation with pressure data of the condensate gas sample.
4. The method for calculating the gas-water interface in a condensate gas reservoir taking into account the influence of gravity differentiation according to claim 1 or 2, characterized in that: The data fitted by the isochoric depletion experiment include: data on the variation of the compressibility factor Z value with pressure, data on the variation of the gas-liquid two-phase compressibility factor with pressure, data on the variation of the component mole fraction with pressure, and data on the variation of the liquid phase saturation with pressure.
5. The method for calculating the gas-water interface of a thick plate-shaped fault-controlled fracture-cavity condensate gas reservoir according to claim 1 or 2, characterized in that: The method for calculating the gas-water interface position of the target condensate gas reservoir well by using the original formation pressure, the static water column pressure, the middle depth of the gas layer of the target condensate gas reservoir well, the formation water density and the density of the condensate gas at different depths in S3 is as follows: Among them, D gwc is the depth of the air-water interface, D g is the depth of the middle gas layer of the condensate gas well, P i is the original formation pressure, P wD is the net water column pressure, ρw is the density of formation water, ρ gi is the density of condensate gas at different depths.
6. The method for calculating the gas-water interface of a condensate gas reservoir taking into account the influence of gravity differentiation as claimed in claim 3, characterized in that: The data fitted by the isochoric depletion experiment include: data on the variation of the compressibility factor Z value with pressure, data on the variation of the gas-liquid two-phase compressibility factor with pressure, data on the variation of the component mole fraction with pressure, and data on the variation of the liquid phase saturation with pressure.
7. The method for calculating the gas-water interface of a thick plate-shaped fault-controlled fracture-cavity condensate gas reservoir according to claim 3 is characterized in that: The method for calculating the gas-water interface position of the target condensate gas reservoir well by using the original formation pressure, the static water column pressure, the middle depth of the gas layer of the target condensate gas reservoir well, the formation water density and the density of the condensate gas at different depths in S3 is as follows:
8. The method for calculating the gas-water interface of a thick plate-shaped fault-controlled fracture-cavity condensate gas reservoir according to claim 4 is characterized in that: The method for calculating the gas-water interface position of the target condensate gas reservoir well by using the original formation pressure, the static water column pressure, the middle depth of the gas layer of the target condensate gas reservoir well, the formation water density and the density of the condensate gas at different depths in S3 is as follows:
9. The method for calculating the gas-water interface of a thick plate-shaped fault-controlled fracture-cavity condensate gas reservoir according to claim 1 or 2, characterized in that: The S3 reservoir numerical simulation system is the Grading Test module in the tNavigator software.
10. The method for calculating the gas-water interface of a thick plate-shaped fault-controlled fracture-cavity condensate gas reservoir according to claim 3, characterized in that: The S3 reservoir numerical simulation system is the Grading Test module in the tNavigator software.