Optimized production allocation method and system in full-life-cycle production process of high-sulfur-content gas well

Abstract

The invention discloses an optimized production allocation method and system in the full-life-cycle production process of a high-sulfur-content gas well, and relates to the technical field of petroleum and natural gas exploration and development.The method comprises the steps that sulfur-containing gas samples at the bottom of the high-sulfur-content gas well are collected, and an indoor sulfur solubility test experiment is utilized; identification and division of a sulfur deposition low-risk area and a sulfur deposition high-risk area under the underground reservoir condition in the full-life-cycle production process of the gas well are achieved; when the gas well is in a sulfur deposition low-risk area, a conventional gas well yield optimization production allocation method is preferably selected; when the gas well is in a sulfur deposition high-risk area, elemental sulfur in the area is separated out in the form of solid particles, and a gas well yield optimization production allocation method considering sulfur deposition is preferably adopted. According to the method, the low-risk area and the high-risk area of sulfur deposition are divided, different optimized production allocation methods are adopted, production and development strategies of the high-sulfur-content gas well in different stages are formed, the development potential of the high-sulfur-content gas well can be greatly improved, and technical support is provided for efficient development of the high-sulfur-content gas reservoir in China.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and natural gas exploration and development, and in particular to a method and system for optimizing production allocation during the entire life cycle production process of a high-sulfur gas well. Background Art

[0002] The development process of high-sulfur gas reservoirs generally faces the problem of sulfur particle deposition and clogging, which poses a challenge to the safe and efficient development of high-sulfur gas reservoirs. Previous studies have shown that in the middle and late stages of high-sulfur gas reservoir development, the pressure reduction in the near-wellbore area of ​​the reservoir will cause a large amount of elemental sulfur particles to precipitate, thereby clogging the reservoir and affecting the production capacity of the gas well. When the sulfur saturation of the reservoir reaches 20%, the gas well production capacity decreases by as much as 50%. Under the influence of sulfur deposition, how to reasonably allocate production of high-sulfur gas wells to reduce the impact of sulfur deposition on gas well production has become the most noteworthy scientific production issue in the field of high-sulfur gas reservoir development.

[0003] In the prior art, the commonly used production allocation methods for gas wells are the unimpeded flow method, the analogy method, the production dynamic analysis method, the objective function constraint method, etc. For example, the patent document CN109488266A provides "a gas well production allocation method and system", which first determines the first gas production of the gas well through the gas production indication curve and the minimum critical sand pressure difference, the temperature and pressure data of the casing annulus and the tubing anti-external extrusion parameters, the production risk correction coefficient, etc., and then compares the first gas production with the economic limit gas production, and takes the minimum value of the two as the gas well production allocation value; for example, the patent document CN114417716A also provides "a gas well production allocation method, device, electronic equipment and medium", which first obtains the constraints that the decision variables need to meet, and then constructs the objective function with the decision variables as the independent variables and the received gas well production allocation target as the dependent variable; the gas well production allocation plan is determined by using the heuristic algorithm according to the constraints and the objective function, and the production of each gas well is allocated according to the production allocation plan. However, these test methods are not suitable for production allocation of high-sulfur gas wells, and they have the following problems: (1) The commonly used open-flow method, analogy method, production dynamic analysis method, etc. mainly rely on existing empirical parameters and are difficult to adapt to current production needs; (2) These methods do not consider the impact of sulfur deposition. Therefore, it is urgent to propose a new optimization production allocation method to solve the problem of optimized production allocation during the entire life cycle of high-sulfur gas reservoirs, especially in the middle and late stages of development, after sulfur is adsorbed and deposited in the formation, how to optimize the production allocation of high-sulfur gas wells to reduce the impact of sulfur deposition on gas well production capacity. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for optimizing production allocation during the entire life cycle of a high-sulfur gas well. The method mainly identifies and divides the sulfur deposition low-risk area and the sulfur deposition high-risk area in the underground near-well area of ​​the gas well during the entire life cycle of the high-sulfur gas well. According to different scenarios and production stages, the production optimization allocation method for the low-risk sulfur deposition area and the production optimization allocation method for the high-risk sulfur deposition area are selected to achieve optimized production allocation during the entire life cycle of the high-sulfur gas well. To achieve the above purpose, the present invention provides the following technical solutions:

[0005] The present invention provides a method for optimizing production allocation during the whole life cycle production of a high-sulfur gas well, the method comprising:

[0006] Step S101, collect sulfur-containing gas samples from the bottom of a high-sulfur gas well, and use an indoor sulfur solubility test experiment to identify and divide sulfur deposition low-risk areas and sulfur deposition high-risk areas under underground reservoir conditions during the production process of the gas well throughout its life cycle;

[0007] Step S102: When the gas well is in a low risk area for sulfur deposition, a conventional gas well production optimization allocation method is preferably used;

[0008] Step S103: When the gas well is in a high-risk area for sulfur deposition, sulfur is precipitated in the form of solid particles in this area, and a method for optimizing the production allocation of the gas well taking sulfur deposition into consideration is preferably adopted.

[0009] Furthermore, step S101 specifically includes:

[0010] After obtaining the bottom-hole sulfur-containing gas sample, the solubility tester is used to measure the sulfur content in the bottom-hole high-sulfur gas sample, and the sulfur saturation of the bottom-hole high-sulfur gas sample under the bottom-hole temperature of the gas well and different development pressure conditions is measured to draw the bottom-hole sulfur solubility curve of the gas well;

[0011] The original sulfur content before the gas well is put into production is marked on the sulfur solubility curve, and the sulfur solubility prediction empirical formula is obtained through sulfur solubility test experiments;

[0012] According to the sulfur solubility curve and the original sulfur content, the critical pressure condition for the precipitation of sulfur at the bottom of the gas well is obtained. Through the critical pressure node for the saturated precipitation of sulfur, the underground production process of the gas well throughout its life cycle is divided into a low-risk area for sulfur deposition and a high-risk area for sulfur deposition.

[0013] Furthermore, the sulfur deposition low risk area is a gas well bottom hole pressure higher than the gas well bottom hole sulfur element saturation precipitation pressure interval, in this interval sulfur element exists in the high sulfur gas in the form of dissolved state, sulfur deposition risk is low;

[0014] The high-risk area for sulfur deposition is a pressure range where the bottom hole pressure of the gas well is in the pressure range where sulfur is saturated and precipitated at the bottom hole of the gas well. In this range, sulfur is precipitated in the form of solid particles, and the risk of sulfur deposition is high.

[0015] Furthermore, step S102 specifically includes:

[0016] When the bottom hole pressure of the gas well is higher than the saturated precipitation pressure of sulfur at the bottom hole of the gas well, the initial production allocation of the gas well before production is quickly determined by analogy method and open-flow method; including: when there is a large difference between the initial production allocation of high-sulfur gas wells determined by analogy method and open-flow method, the initial production allocation obtained by analogy method is preferred; when it is difficult to find a reference for existing production wells under similar geological conditions, the initial production allocation obtained by open-flow method is selected;

[0017] After the gas well has been producing for a period of time, the modern production decline method is used to fit the production data to obtain the dynamic reserves of the gas well. Further, based on the stable production period requirements during the preparation of the gas reservoir plan, a reasonable production allocation is selected to meet the stable production requirements of high-sulfur gas wells. This production allocation plan is implemented when the gas well has not entered the high-risk area for sulfur deposition.

[0018] Furthermore, the analogy method refers to the production of existing high-sulfur gas wells that can produce stably under similar geological conditions;

[0019] The open flow rate method uses 1 / 4 of the open flow rate calculated by the productivity equation of the high-sulfur gas well as the initial production allocation of the gas well.

[0020] Furthermore, step S103 specifically includes:

[0021] When the bottom hole pressure of the gas well is in the pressure range where sulfur is saturated and precipitated at the bottom hole of the gas well, the relationship between reservoir physical properties and sulfur saturation is optimized, and then the production capacity equation and sulfur saturation prediction equation considering sulfur deposition are established;

[0022] Draw production indicator curves under the influence of different sulfur saturation;

[0023] The production indicator curve is used to determine the reasonable production allocation method of the gas well.

[0024] Furthermore, the method for determining a reasonable production allocation of a gas well by using a production indicator curve includes:

[0025] The production indicator curve under the influence of different sulfur saturations is to draw the production indicator curve under the influence of different sulfur saturations through the multi-zone composite horizontal well productivity equation under sulfur deposition, and find the point where the production deviates from the early straight line as the reasonable production of the gas well;

[0026] According to the reasonable production allocation data under different sulfur saturations, a relationship chart between reasonable production allocation value and sulfur saturation under different sulfur saturations is established. At the same time, according to the numerical simulation prediction method, a relationship chart between pressure and production time after sulfur deposition appears at the bottom of the gas well is established;

[0027] According to the bottom hole pressure of the gas well, the corresponding time node is found on the relationship chart of pressure and production time after sulfur deposition appears at the bottom of the well, and then the corresponding sulfur saturation is found on the chart of sulfur saturation and production time after sulfur deposition appears at the bottom of the well. Finally, the reasonable production allocation value under the current degree of sulfur deposition is optimized through the relationship chart of reasonable production allocation value and sulfur saturation under different sulfur saturations.

[0028] The present invention also provides an optimized production allocation system for a high-sulfur gas well during the entire life cycle production process, the system comprising:

[0029] The module for identifying and dividing sulfur deposition low-risk and high-risk areas is used to collect sulfur-containing gas samples at the bottom of high-sulfur gas wells, and use indoor sulfur solubility test experiments to identify and divide sulfur deposition low-risk areas and sulfur deposition high-risk areas under underground reservoir conditions during the production process of the gas well throughout its life cycle;

[0030] A production allocation method optimization module for low-risk sulfur deposition areas, which is used to optimize the production allocation method for conventional gas wells when the gas well is in a low-risk sulfur deposition area;

[0031] The module for optimizing the production allocation method in high-risk areas of sulfur deposition is used when the gas well is in a high-risk area of ​​sulfur deposition. The sulfur element is precipitated in the form of solid particles in this area. It is preferred to adopt a gas well production optimization production allocation method that takes sulfur deposition into consideration.

[0032] Furthermore, the module for identifying and dividing sulfur deposition low-risk areas and high-risk areas is specifically used for:

[0033] After obtaining the bottom-hole sulfur-containing gas sample, the solubility tester is used to measure the sulfur content in the bottom-hole high-sulfur gas sample, and the sulfur saturation of the bottom-hole high-sulfur gas sample under the bottom-hole temperature of the gas well and different development pressure conditions is measured to draw the bottom-hole sulfur solubility curve of the gas well;

[0034] The original sulfur content before the gas well is put into production is marked on the sulfur solubility curve, and the sulfur solubility prediction empirical formula is obtained through sulfur solubility test experiments;

[0035] According to the sulfur solubility curve and the original sulfur content, the critical pressure condition for the precipitation of sulfur at the bottom of the gas well is obtained. Through the critical pressure node for the saturated precipitation of sulfur, the underground production process of the gas well throughout its life cycle is divided into a low-risk area for sulfur deposition and a high-risk area for sulfur deposition.

[0036] Furthermore, the preferred module of the sulfur deposition low risk area production allocation method is specifically used for:

[0037] When the bottom hole pressure of the gas well is higher than the saturated precipitation pressure of sulfur at the bottom hole of the gas well, the initial production allocation of the gas well before production is quickly determined by analogy method and open-flow method; including: when there is a large difference between the initial production allocation of high-sulfur gas wells determined by analogy method and open-flow method, the initial production allocation obtained by analogy method is preferred; when it is difficult to find a reference for existing production wells under similar geological conditions, the initial production allocation obtained by open-flow method is selected;

[0038] After the gas well has been producing for a period of time, the modern production decline method is used to fit the production data to obtain the dynamic reserves of the gas well. Further, based on the stable production period requirements during the preparation of the gas reservoir plan, a reasonable production allocation is selected to meet the stable production requirements of high-sulfur gas wells. This production allocation plan is implemented when the gas well has not entered the high-risk area for sulfur deposition.

[0039] Furthermore, the preferred module of the production allocation method in high-risk areas of sulfur deposition is specifically used for:

[0040] When the bottom hole pressure of the gas well is in the pressure range where sulfur is saturated and precipitated at the bottom hole of the gas well, the relationship between reservoir physical properties and sulfur saturation is optimized, and then the production capacity equation and sulfur saturation prediction equation considering sulfur deposition are established;

[0041] Draw production indicator curves under the influence of different sulfur saturation;

[0042] The production indicator curve is used to determine the reasonable production allocation method of the gas well.

[0043] Technical effects and advantages of the present invention:

[0044] First, the present invention uses indoor sulfur solubility test experiments to accurately identify and divide the low-risk areas and high-risk areas of sulfur deposition in the production process of high-sulfur gas wells throughout their life cycle, and then formulates different optimization production allocation methods according to different underground conditions of gas wells. When high-sulfur gas wells are in the low-risk area of ​​sulfur deposition in the early stage of development, the analogy method, the unimpeded flow method, etc. are used to quickly determine the production allocation plan when the gas well is put into production. After the gas well has been produced for a period of time, the modern production decline method can be used to fit the dynamic reserves of the gas well, and the single well stability during the preparation of the gas reservoir plan can be used to optimize the production allocation plan. Based on the production life requirements, a more reasonable production allocation can be set; with the development of gas reservoirs, the formation pressure continues to decline. When the bottom hole pressure of the gas well is in the sulfur saturation precipitation pressure range, sulfur will precipitate and deposit to block the pore throat, affecting the gas well production capacity. At this time, the production capacity equation and sulfur saturation prediction model under the influence of sulfur deposition can be established, and then the gas production indicator curve under the influence of sulfur deposition can be drawn. Through the gas production indicator curves under different sulfur saturations, reasonable production allocation can be carried out to minimize the impact of sulfur deposition on the gas well production capacity, thereby improving the development effect of the gas well.

[0045] Second, the present invention divides the sulfur deposition low-risk areas into high-risk areas, adopts different optimization production allocation methods, and forms production and development strategies for high-sulfur gas wells at different stages, which can greatly enhance the development potential of high-sulfur gas wells and provide technical support for the efficient development of my country's high-sulfur gas reservoirs.

[0046] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0048] Figure 1 This is a flow chart of a method for optimizing production allocation during the entire life cycle production of a high-sulfur gas well according to the present invention;

[0049] Figure 2 A schematic diagram of the division and identification of low-risk and high-risk areas for sulfur deposition at the bottom of a gas well according to an embodiment of the present invention;

[0050] Figure 3 A graph showing the relationship between sulfur saturation and production time after sulfur deposition occurs at the bottom of a gas well according to an embodiment of the present invention;

[0051] Figure 4 A schematic diagram of a gas production indication curve and a reasonable production allocation determination diagram when the sulfur saturation of a gas well is 20% according to an embodiment of the present invention;

[0052] Figure 5 A graph showing the relationship between the reasonable production value and the sulfur saturation at different sulfur saturations at the bottom of a gas well according to an embodiment of the present invention;

[0053] Figure 6 This is a graph showing changes in formation pressure and production time after saturation precipitation of elemental sulfur according to an embodiment of the present invention;

[0054] Figure 7 It is a schematic diagram of an optimized production allocation system for a high-sulfur gas well during the entire life cycle production process of the present invention. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] In order to solve the deficiencies of the prior art, the present invention discloses a method for optimizing production allocation during the entire life cycle of a high-sulfur gas well. Figure 1 The flowchart of the method for optimizing production allocation during the whole life cycle production of a high-sulfur gas well of the present invention is as follows: Figure 1 As shown, the method comprises the following steps:

[0057] Step S101, identification and division of the low-risk area and high-risk area of ​​sulfur deposition at the bottom of a high-sulfur gas well: collect sulfur-containing gas samples from the high-sulfur gas well, and use indoor sulfur solubility test experiments to identify and divide the low-risk area and high-risk area of ​​sulfur deposition under underground reservoir conditions during the entire life cycle of the gas well.

[0058] Step S101 specifically includes the following steps:

[0059] First, before collecting the sulfur-containing gas sample, a downhole pressure gauge needs to be lowered to obtain the bottom hole temperature and pressure of the gas well; the sulfur-containing gas sample is a bottom hole gas sample of a high-sulfur gas well, and is a bottom hole gas sample under the original conditions before the gas well is put into production. After obtaining the bottom hole sulfur-containing gas sample, a solubility tester is used to determine the sulfur content in the bottom hole high-sulfur gas sample, and at the same time, the sulfur saturation of the bottom hole high-sulfur gas sample under the bottom hole temperature of the gas well and different development pressure conditions is determined to draw the bottom hole sulfur solubility curve of the gas well.

[0060] Furthermore, the bottom hole high-sulfur gas sample is a high-temperature, high-pressure, high-sulfur original gas sample obtained from the bottom hole under reservoir conditions.

[0061] Preferably, the method for determining the original sulfur content in the bottom hole high-sulfur gas sample and the sulfur solubility curve under different development pressures is quantitative detection by gas chromatography-mass spectrometry.

[0062] Then, the original sulfur content before the gas well is put into production is marked in the sulfur solubility curve, and the sulfur solubility prediction empirical formula is obtained through the sulfur solubility test experiment (the fitted empirical formula is used for the dc / dp calculation in the production capacity equation).

[0063] Furthermore, the empirical formula for predicting sulfur solubility is the Chrastil empirical formula:

[0064]

[0065] In formula (1), K, A, and B are experimental coefficients; C is the sulfur solubility, ρ g is the gas density and T is the temperature.

[0066] Finally, based on the sulfur solubility curve and the original sulfur content, the critical pressure condition for the precipitation of sulfur at the bottom of the gas well is obtained. Through the critical pressure node for the saturated precipitation of sulfur, the underground production process of the gas well throughout its life cycle is divided into a low-risk area for sulfur deposition and a high-risk area for sulfur deposition. Among them, the low-risk area for sulfur deposition is the pressure interval where the bottom-hole pressure of the gas well is higher than the pressure interval when the sulfur at the bottom of the gas well is saturated and precipitated. In this interval, sulfur exists in the high-sulfur gas in a dissolved state, and the risk of sulfur deposition is low. The high-risk area for sulfur deposition is the pressure interval where the bottom-hole pressure of the gas well is in the pressure interval when the sulfur at the bottom of the gas well is saturated and precipitated. In this interval, sulfur precipitates in the form of solid particles, and the risk of sulfur deposition is high.

[0067] Step S102, the production allocation method for the low risk area of ​​sulfur deposition at the bottom of a high-sulfur gas well is preferred: when the gas well is in the low risk area of ​​sulfur deposition, the conventional gas well production optimization production allocation method is preferred.

[0068] Step S102 specifically includes the following steps:

[0069] First, when the bottom hole pressure of the gas well is higher than the saturated precipitation pressure of sulfur at the bottom hole of the gas well, sulfur deposition has no effect on the gas well production capacity, and the optimization of gas well production allocation does not need to consider the impact of sulfur deposition. The initial production allocation of the gas well can be quickly determined by analogy and unimpeded flow method. When there is a large difference between the initial production allocation of high-sulfur gas wells determined by analogy and unimpeded flow methods, the initial production allocation obtained by analogy is preferred; when it is difficult to find existing production wells under similar geological conditions for reference, the initial production allocation obtained by unimpeded flow method is selected.

[0070] Then, after the gas well has been producing for a period of time, the modern production decline method is used to fit the production data to obtain the dynamic reserves of the gas well. Further, based on the stable production period requirements during the preparation of the gas reservoir plan, a reasonable production allocation is selected to meet the stable production requirements of high-sulfur gas wells. This production allocation plan is implemented when the gas well has not entered the high-risk area for sulfur deposition.

[0071] Furthermore, the analogy method refers to the production of existing high-sulfur gas wells that can produce stably under similar geological conditions; the open-flow rate method uses 1 / 4 of the open-flow rate calculated by the production capacity equation of the high-sulfur gas well as the initial production allocation of the gas well.

[0072] Step S103, the production allocation method for the high-risk area of ​​sulfur deposition at the bottom of a high-sulfur gas well is preferably adopted: when the gas well is in the high-risk area of ​​sulfur deposition, sulfur is precipitated in the form of solid particles in this area, and the gas well production optimization allocation method considering sulfur deposition is preferably adopted.

[0073] Step S103 specifically includes the following steps:

[0074] First, when the bottom hole pressure of the gas well is in the pressure range when sulfur is saturated and precipitated at the bottom hole of the gas well, sulfur precipitates from the sulfur-containing gas in the form of solid particles. After sulfur deposition and precipitation, the reservoir pores are blocked, affecting the gas well production capacity. The influence of sulfur deposition needs to be considered when optimizing the production allocation of gas wells. At this stage, the optimized production allocation of high-sulfur gas wells should focus on reducing the influence of sulfur deposition on the seepage capacity of gas wells. The relationship between reservoir physical properties and sulfur saturation can be optimized, and then the production capacity equation and sulfur saturation prediction equation considering sulfur deposition are established.

[0075] Preferably, the relationship between the reservoir physical property and sulfur saturation is:

[0076] lmk r =aS s ; (2)

[0077] In formula (2), K r is the relative permeability of the reservoir when sulfur deposition occurs, a is the empirical coefficient, which is -6.824, S s is the sulfur saturation of the reservoir.

[0078] Preferably, the sulfur saturation prediction equation is a sulfur saturation prediction equation under non-Darcy flow conditions of gas:

[0079]

[0080]

[0081]

[0082] In formulas (3)-(5), S s is the sulfur saturation of the reservoir, A and B are experimental coefficients, α is the empirical coefficient, r is the well radius, h is the effective thickness of the reservoir, μ is the gas viscosity, φ is the reservoir porosity, and q g is the natural gas production, S wi is the irreducible water saturation of the reservoir, B g is the natural gas volume coefficient, K a is the original permeability of the formation, dc / dp is the change in sulfur solubility in natural gas under unit pressure drop, t is the production time, β is the turbulence coefficient, ρ g is the gas density and β is the turbulence coefficient.

[0083] Preferably, the productivity equation under the effect of sulfur deposition refers to a productivity equation for multi-zone composite high-angle wells under the effect of sulfur deposition established on the basis of reservoir core physical properties and sulfur saturation model and sulfur deposition saturation prediction model.

[0084] Furthermore, the productivity equation of the high-angle well under the sulfur deposition effect is:

[0085]

[0086]

[0087]

[0088]

[0089]

[0090] In formulas (6)-(9), P e is the supply boundary pressure, P wf is the bottom hole pressure, A and B are experimental coefficients, q sc is the gas volume flow rate (ground), K a is the original permeability of the formation, B g is the natural gas volume coefficient, Z is the gas deviation factor, p sc is the gas pressure under standard conditions, T is the formation temperature, T sc is the gas temperature under standard conditions, h is the effective thickness of the reservoir, μ g is the gas viscosity; γ g is the relative density of gas, β is the turbulence coefficient, r a Radius of pollution zone, r w is the wellbore radius, r wθ is the effective well radius of the inclined well, r1 is the supply boundary, r a is the sulfur deposition radius, θ is the well inclination angle, L is the length of the inclined well, S s is the sulfur saturation of the reservoir.

[0091] Then, the production indicator curve under the influence of different sulfur saturations is drawn. The production indicator curve under the influence of different sulfur saturations refers to the production indicator curve under the influence of different sulfur saturations drawn by the multi-zone composite horizontal well productivity equation under the effect of sulfur deposition, and the point of production that deviates from the early straight line is found as the reasonable production of the gas well. According to the reasonable production allocation data under different sulfur saturations, a relationship chart between the reasonable production allocation value and the sulfur saturation under different sulfur saturations is established. At the same time, according to the numerical simulation prediction method, a relationship chart between the pressure and the production time change after sulfur deposition appears at the bottom of the gas well is established.

[0092] Finally, according to the bottom hole pressure of the gas well, the corresponding time node is found on the relationship chart of pressure and production time after sulfur deposition appears at the bottom of the well, and then the corresponding sulfur saturation is found on the chart of sulfur saturation and production time after sulfur deposition appears at the bottom of the well. Finally, the reasonable production allocation value under the current degree of sulfur deposition is optimized through the relationship chart of reasonable production allocation value and sulfur saturation under different sulfur saturations.

[0093] Example:

[0094] Step S101: Collect sulfur-containing gas samples from the high-sulfur gas well, and use indoor sulfur solubility test experiments to identify and divide sulfur deposition low-risk areas and sulfur deposition high-risk areas under underground reservoir conditions during the entire life cycle of the gas well.

[0095] Before collecting the sulfur-containing gas sample, a downhole pressure gauge was lowered to obtain a gas well bottom temperature of 90°C and a pressure of 50 MPa;

[0096] The gas sample is a bottom gas sample of a high-sulfur gas well, and is a bottom gas sample under original conditions before the gas well is put into production. After obtaining the bottom gas sample, a solubility tester is used to determine the sulfur content in the bottom high-sulfur gas sample. At the same time, the sulfur saturation of the bottom high-sulfur gas sample at a bottom temperature of 90°C and different development pressures is determined. A bottom sulfur solubility curve of the gas well is drawn, and the original sulfur content of 0.39 g / m before the gas well is put into production is marked in the sulfur solubility curve. 3 At the same time, through the sulfur solubility test experiment, the empirical formula for predicting sulfur solubility is obtained. Figure 2 Schematic diagram of the division and identification of low-risk and high-risk areas for sulfur deposition at the bottom of a gas well according to an embodiment of the present invention, as shown in FIG. Figure 2 As shown, according to the sulfur solubility curve and the sulfur content under original conditions, the critical pressure condition for the precipitation of sulfur at the bottom of the gas well is obtained. Through the critical pressure node for the saturated precipitation of sulfur, the underground production process of the gas well throughout its life cycle is divided into a low-risk area for sulfur deposition and a high-risk area for sulfur deposition.

[0097] The bottom hole high-sulfur gas sample is a high-temperature, high-pressure, high-sulfur original gas sample obtained from the bottom hole under reservoir conditions.

[0098] Preferably, the method for determining the original sulfur content in the bottom hole high-sulfur gas sample and the sulfur solubility curve under different pressures is quantitative detection by gas chromatography-mass spectrometry.

[0099] The low risk area for sulfur deposition is a pressure range where the bottom hole pressure of the gas well is higher than the pressure range at which sulfur is saturated and precipitated at the bottom hole of the gas well. In this range, sulfur exists in a dissolved state in the high sulfur-containing gas, and the risk of sulfur deposition is low.

[0100] The high-risk area for sulfur deposition is a pressure range where the bottom hole pressure of the gas well is in the pressure range when sulfur is saturated and precipitated at the bottom hole of the gas well. In this range, sulfur is precipitated in the form of solid particles, and the risk of sulfur deposition is high.

[0101] The empirical formula for predicting sulfur solubility is the Chrastil empirical formula:

[0102]

[0103] In the above formula, C is the sulfur solubility, T is the temperature, K, A, and B are experimental coefficients, and their values ​​are: A=4099.5, B=-9.3, K=4336.1 / T-10.168 respectively.

[0104] Step S102: When the gas well is in a low risk area for sulfur deposition, it is preferred to adopt a production optimization allocation method that does not consider sulfur deposition.

[0105] When the bottom hole pressure of a gas well is higher than the saturated precipitation pressure of sulfur at the bottom hole of the gas well, sulfur deposition has no effect on the gas well productivity, and the optimization of gas well production allocation does not need to consider the impact of sulfur deposition. The initial production allocation of a gas well can be quickly determined by analogy and unimpeded flow method. When there is a large difference between the initial production allocation of a high-sulfur gas well determined by the analogy and unimpeded flow methods, the initial production allocation obtained by the analogy method is preferred; when it is difficult to find a reference to an existing production well under similar geological conditions, the initial production allocation obtained by the unimpeded flow method is selected.

[0106] After the gas well has been producing for a period of time, the dynamic reserves of the gas well are obtained by fitting the production data using the modern production decline method. Further, based on the stable production period requirements during the preparation of the gas reservoir plan, a reasonable production allocation is selected to meet the stable production requirements of high-sulfur gas wells. This production allocation plan is implemented when the gas well has not entered the high-risk area for sulfur deposition.

[0107] The analogy method is to refer to the production of existing high-sulfur gas wells that can produce stably under similar geological conditions;

[0108] The open flow rate method uses 1 / 4 of the open flow rate calculated by the productivity equation of the high-sulfur gas well as the initial production allocation of the gas well.

[0109] In this embodiment, the analogy method is used to optimize the production scale of 1.6 million cubic meters / day. After 5 months of production, according to the modern output decline method with a 5-year stable production period as the requirement, the production scale of 1.5 million cubic meters / day is optimized.

[0110] Step S103: When the gas well is in a high-risk area for sulfur deposition, sulfur is precipitated in the form of solid particles in this area, and a production optimization method that takes sulfur deposition into consideration is preferably used.

[0111] When the bottom hole pressure of the gas well is in the pressure range when sulfur is saturated and precipitated at the bottom hole of the gas well, sulfur precipitates from the sulfur-containing gas in the form of solid particles. After the sulfur deposits are precipitated, the reservoir pores are blocked, affecting the gas well production capacity. The influence of sulfur deposition needs to be considered when optimizing the production allocation of gas wells. At this stage, the optimized production allocation of high-sulfur gas wells should be mainly based on reducing the influence of sulfur deposition on the seepage capacity of the gas well. The relationship between reservoir physical properties and sulfur saturation can be optimized, and then the production capacity equation considering sulfur deposition and the sulfur saturation prediction equation are established, and the production indicator curve (i.e., gas production indicator curve) under the influence of different sulfur saturations is drawn, and the gas production indicator curve is used to determine the reasonable production allocation method of the gas well.

[0112] Preferably, the relationship between the reservoir physical properties and sulfur saturation is:

[0113] lmk r =aS s ;

[0114] In the above formula, K r is the relative permeability of the reservoir when sulfur deposition occurs, a is the empirical coefficient with a value of -6.824, and Ss is the sulfur saturation of the reservoir.

[0115] Preferably, the sulfur saturation prediction model is a sulfur saturation prediction model under non-Darcy flow conditions of gas:

[0116]

[0117]

[0118]

[0119] In the above formula, S s is the sulfur saturation of the reservoir, A and B are experimental coefficients, α is the empirical coefficient, r is the well radius, h is the effective thickness of the reservoir, μ is the gas viscosity, φ is the reservoir porosity, and q g is the natural gas production, S wi is the irreducible water saturation of the reservoir, B g is the natural gas volume coefficient, K a is the original permeability of the formation, dc / dp is the change in sulfur solubility in natural gas under unit pressure drop, t is the production time, β is the turbulence coefficient, ρ g is the gas density and β is the turbulence coefficient.

[0120] Figure 3 The graph of the relationship between sulfur saturation and production time after sulfur deposition appears at the bottom of a gas well according to an embodiment of the present invention is as follows: Figure 3 As shown in the figure, according to the sulfur saturation equation, the relationship between sulfur saturation and production time after sulfur deposition appears at the bottom of the gas well is obtained, and its expression is as follows:

[0121] y=10 -8 x 2 -4*10 -5 x+0.0234;

[0122] Where y is the sulfur saturation after sulfur deposition occurs at the bottom of the gas well; x is the production time.

[0123] The productivity equation under the effect of sulfur deposition refers to a productivity equation for multi-zone composite high-angle wells under the effect of sulfur deposition, which is established on the basis of reservoir core physical properties and sulfur saturation model and sulfur deposition saturation prediction model.

[0124] Preferably, the productivity equation of the high-angle well under the sulfur deposition effect is:

[0125]

[0126]

[0127]

[0128]

[0129]

[0130] In the above formula, P e is the supply boundary pressure, P wf is the bottom hole pressure, A and B are experimental coefficients, and their values ​​are: A = 4099.5, B = -9.3, q sc is the gas volume flow rate (ground), K a is the original permeability of the formation, B g is the natural gas volume coefficient, Z is the gas deviation factor, p sc is the gas pressure under standard conditions, T is the formation temperature, T sc is the gas temperature under standard conditions, h is the effective thickness of the reservoir, μ g is the gas viscosity, mPa·s; γ g is the relative density of gas, β is the turbulence coefficient, r a Radius of pollution zone, r w is the radius of the well bottom, r wθ is the effective well radius of the inclined well, r1 is the supply boundary, r a is the sulfur deposition radius, θ is the well inclination angle, L is the length of the inclined well, S s is the sulfur saturation of the reservoir.

[0131] The production indicator curve under the influence of different sulfur saturations refers to the production indicator curve under the influence of different sulfur saturations drawn by the multi-zone composite horizontal well productivity equation under the action of sulfur deposition, and the point of production that deviates from the early straight line is found as the reasonable production of the gas well. Figure 4 The gas production indication curve when the sulfur saturation of the gas well in the embodiment of the present invention is 20% is shown as follows: Figure 4 As shown, according to the gas production indication curve, when the sulfur saturation at the bottom of the gas well is 20%, the reasonable production allocation is 800,000 cubic meters per day.

[0132] According to the reasonable production allocation data under different sulfur saturations, a relationship chart between reasonable production allocation value and sulfur saturation under different sulfur saturations is established. Figure 5 The relationship between the reasonable production value and the sulfur saturation at different sulfur saturations at the bottom of the gas well according to the embodiment of the present invention is shown in the following expression:

[0133] y=0.052x 2 -5.0959x+157.42;

[0134] Where y is the sulfur saturation after sulfur deposition occurs at the bottom of the gas well; x is the production time.

[0135] At the same time, according to the numerical simulation prediction method, a chart showing the relationship between pressure and production time after sulfur deposition appears at the bottom of the gas well is established. Figure 6 This is a graph showing the change in formation pressure and production time after sulfur saturation precipitation in an embodiment of the present invention. Further fitting is performed to obtain a relationship between formation pressure and time change, and the expression is as follows:

[0136] P = -0.0056d + 30.277;

[0137] Where P is the bottom hole pressure and d is the production time.

[0138] According to the bottom hole pressure of the gas well, the corresponding time node is found on the relationship chart of the pressure and production time after the occurrence of sulfur deposition at the bottom of the well, and then the corresponding sulfur saturation is found on the chart of the sulfur saturation and production time after the occurrence of sulfur deposition at the bottom of the well. Finally, the reasonable production allocation value under the current degree of sulfur deposition is optimized through the relationship chart of the reasonable production allocation value and sulfur saturation under different sulfur saturations.

[0139] The present invention also discloses an optimized production allocation system for a high-sulfur gas well during the entire production life cycle. Figure 7 FIG. 1 is a schematic diagram of an optimized production allocation system for a high-sulfur gas well during the entire life cycle of production according to the present invention. Figure 7 As shown, the system includes: a sulfur deposition low-risk area and a high-risk area identification and division module 201, which is used to collect sulfur-containing gas samples at the bottom of a high-sulfur gas well, and use an indoor sulfur solubility test experiment to realize the identification and division of sulfur deposition low-risk areas and sulfur deposition high-risk areas under underground reservoir conditions during the production process of the gas well throughout its life cycle; a sulfur deposition low-risk area production allocation method optimization module 202, which is used to optimize the conventional gas well production allocation method when the gas well is in the sulfur deposition low-risk area; a sulfur deposition high-risk area production allocation method optimization module 203, which is used when the gas well is in the sulfur deposition high-risk area, in this interval, sulfur element is precipitated in the form of solid particles, and preferably adopts the gas well production optimization allocation method considering sulfur deposition.

[0140] Furthermore, the sulfur deposition low-risk area and high-risk area identification and division module 201 is specifically used for: after obtaining the bottom hole sulfur-containing gas sample, using a solubility tester to determine the sulfur content in the bottom hole high-sulfur gas sample, and at the same time determining the sulfur saturation of the bottom hole high-sulfur gas sample under the bottom hole temperature of the gas well and different development pressure conditions, and drawing the bottom hole sulfur solubility curve of the gas well; marking the original sulfur content of the gas well before production in the sulfur solubility curve diagram, and at the same time obtaining the sulfur solubility prediction empirical formula through the sulfur solubility test experiment; according to the sulfur solubility curve and the original sulfur content, obtaining the critical pressure condition for the precipitation of sulfur at the bottom of the gas well, and dividing the underground production process of the gas well into a low-risk area for sulfur deposition and a high-risk area for sulfur deposition through the critical pressure node for the saturated precipitation of sulfur.

[0141] Furthermore, the production allocation method optimization module 202 for low-risk areas of sulfur deposition is specifically used for: when the bottom hole pressure of the gas well is higher than the saturated precipitation pressure of sulfur at the bottom hole of the gas well, quickly determining the initial production allocation of the gas well by analogy and the open-flow method; including: when there is a large difference between the initial production allocations of high-sulfur gas wells determined by the analogy and the open-flow method, the initial production allocation obtained by the analogy method is preferred; when it is difficult to find existing production wells under similar geological conditions for reference, the initial production allocation obtained by the open-flow method is selected; after the gas well has been produced for a period of time, the dynamic reserves of the gas well are obtained by fitting the production data using the modern production decline method, and further based on the stable production period requirements during the preparation of the gas reservoir plan, a reasonable production allocation is selected to meet the stable production requirements of the high-sulfur gas well, and the production allocation plan is executed when the gas well has not entered the high-risk area of ​​sulfur deposition.

[0142] Furthermore, the production allocation method optimization module 203 for high-risk areas of sulfur deposition is specifically used for: when the bottom hole pressure of the gas well is in the pressure range when sulfur is saturated and precipitated at the bottom hole of the gas well, optimizing the relationship between reservoir physical properties and sulfur saturation, then establishing a production capacity equation and a sulfur saturation prediction equation considering sulfur deposition, drawing production indicator curves under the influence of different sulfur saturations, and determining a reasonable production allocation method for the gas well using the production indicator curves.

[0143] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for optimizing production allocation during the entire life cycle of a high-sulfur gas well, characterized in that: The method comprises: Step S101, collect sulfur-containing gas samples from the bottom of a high-sulfur gas well, and use an indoor sulfur solubility test experiment to identify and divide sulfur deposition low-risk areas and sulfur deposition high-risk areas under underground reservoir conditions during the production process of the gas well throughout its life cycle; Step S102: When the gas well is in a low risk area for sulfur deposition, a conventional gas well production optimization allocation method is preferably used; Step S103: When the gas well is in a high-risk area for sulfur deposition, sulfur is precipitated in the form of solid particles in this area, and a method for optimizing the production allocation of the gas well taking sulfur deposition into consideration is preferably adopted.

2. The method for optimizing production allocation during the whole life cycle production of a high-sulfur gas well according to claim 1, characterized in that: Step S101 specifically includes: After obtaining the bottom-hole sulfur-containing gas sample, the solubility tester is used to measure the sulfur content in the bottom-hole high-sulfur gas sample, and the sulfur saturation of the bottom-hole high-sulfur gas sample under the bottom-hole temperature of the gas well and different development pressure conditions is measured to draw the bottom-hole sulfur solubility curve of the gas well; The original sulfur content before the gas well is put into production is marked on the sulfur solubility curve, and the sulfur solubility prediction empirical formula is obtained through sulfur solubility test experiments; According to the sulfur solubility curve and the original sulfur content, the critical pressure condition for the precipitation of sulfur at the bottom of the gas well is obtained. Through the critical pressure node for the saturated precipitation of sulfur, the underground production process of the gas well throughout its life cycle is divided into a low-risk area for sulfur deposition and a high-risk area for sulfur deposition.

3. The method for optimizing production allocation during the whole life cycle production of a high-sulfur gas well according to claim 1 or 2, characterized in that: The low risk area for sulfur deposition is a pressure interval where the bottom hole pressure of the gas well is higher than the pressure interval at which sulfur is saturated and precipitated at the bottom hole of the gas well. In this interval, sulfur exists in a dissolved state in the high sulfur-containing gas, and the risk of sulfur deposition is low. The high-risk area for sulfur deposition is a pressure range where the bottom hole pressure of the gas well is in the pressure range where sulfur is saturated and precipitated at the bottom hole of the gas well. In this range, sulfur is precipitated in the form of solid particles, and the risk of sulfur deposition is high.

4. The method for optimizing production allocation during the whole life cycle production of a high-sulfur gas well according to claim 1, characterized in that: Step S102 specifically includes: When the bottom hole pressure of the gas well is higher than the saturated precipitation pressure of sulfur at the bottom hole of the gas well, the initial production allocation of the gas well before production is quickly determined by analogy method and open-flow method; including: when there is a large difference between the initial production allocation of high-sulfur gas wells determined by analogy method and open-flow method, the initial production allocation obtained by analogy method is preferred; when it is difficult to find a reference for existing production wells under similar geological conditions, the initial production allocation obtained by open-flow method is selected; After the gas well has been producing for a period of time, the modern production decline method is used to fit the production data to obtain the dynamic reserves of the gas well. Further, based on the stable production period requirements during the preparation of the gas reservoir plan, a reasonable production allocation is selected to meet the stable production requirements of high-sulfur gas wells. This production allocation plan is implemented when the gas well has not entered the high-risk area for sulfur deposition.

5. The method for optimizing production allocation during the whole life cycle production of a high-sulfur gas well according to claim 4, characterized in that: The analogy method is to refer to the production of existing high-sulfur gas wells that can produce stably under similar geological conditions; The open flow rate method uses 1 / 4 of the open flow rate calculated by the productivity equation of the high-sulfur gas well as the initial production allocation of the gas well.

6. The method for optimizing production allocation during the whole life cycle production of a high-sulfur gas well according to claim 1, characterized in that: Step S103 specifically includes: When the bottom hole pressure of the gas well is in the pressure range where sulfur is saturated and precipitated at the bottom hole of the gas well, the relationship between reservoir physical properties and sulfur saturation is optimized, and then the production capacity equation and sulfur saturation prediction equation considering sulfur deposition are established; Draw production indicator curves under the influence of different sulfur saturation; The production indicator curve is used to determine the reasonable production allocation method of the gas well.

7. The method for optimizing production allocation during the whole life cycle production of a high-sulfur gas well according to claim 6, characterized in that: The method for determining the reasonable production allocation of a gas well by using a production indicator curve comprises: The production indicator curve under the influence of different sulfur saturations is to draw the production indicator curve under the influence of different sulfur saturations through the multi-zone composite horizontal well productivity equation under sulfur deposition, and find the point where the production deviates from the early straight line as the reasonable production of the gas well; According to the reasonable production allocation data under different sulfur saturations, a relationship chart between reasonable production allocation value and sulfur saturation under different sulfur saturations is established. At the same time, according to the numerical simulation prediction method, a relationship chart between pressure and production time after sulfur deposition appears at the bottom of the gas well is established; According to the bottom hole pressure of the gas well, the corresponding time node is found on the relationship chart of pressure and production time after sulfur deposition appears at the bottom of the well, and then the corresponding sulfur saturation is found on the chart of sulfur saturation and production time after sulfur deposition appears at the bottom of the well. Finally, the reasonable production allocation value under the current degree of sulfur deposition is optimized through the relationship chart of reasonable production allocation value and sulfur saturation under different sulfur saturations.

8. An optimized production allocation system for high-sulfur gas wells during the entire life cycle of production, characterized in that: The system comprises: The module for identifying and dividing sulfur deposition low-risk and high-risk areas is used to collect sulfur-containing gas samples at the bottom of high-sulfur gas wells, and use indoor sulfur solubility test experiments to identify and divide sulfur deposition low-risk areas and sulfur deposition high-risk areas under underground reservoir conditions during the production process of the gas well throughout its life cycle; A production allocation method optimization module for low-risk sulfur deposition areas, which is used to optimize the production allocation method for conventional gas wells when the gas well is in a low-risk sulfur deposition area; The module for optimizing the production allocation method in high-risk areas of sulfur deposition is used when the gas well is in a high-risk area of ​​sulfur deposition. The sulfur element is precipitated in the form of solid particles in this area. It is preferred to adopt a gas well production optimization allocation method that takes sulfur deposition into consideration.

9. The optimized production allocation system for high-sulfur gas wells during the entire life cycle of production according to claim 8, characterized in that: The sulfur deposition low-risk area and high-risk area identification and division module is specifically used for: After obtaining the bottom-hole sulfur-containing gas sample, the solubility tester is used to measure the sulfur content in the bottom-hole high-sulfur gas sample, and the sulfur saturation of the bottom-hole high-sulfur gas sample under the bottom-hole temperature of the gas well and different development pressure conditions is measured to draw the bottom-hole sulfur solubility curve of the gas well; The original sulfur content before the gas well is put into production is marked on the sulfur solubility curve, and the sulfur solubility prediction empirical formula is obtained through sulfur solubility test experiments; According to the sulfur solubility curve and the original sulfur content, the critical pressure condition for the precipitation of sulfur at the bottom of the gas well is obtained. Through the critical pressure node for the saturated precipitation of sulfur, the underground production process of the gas well throughout its life cycle is divided into a low-risk area for sulfur deposition and a high-risk area for sulfur deposition.

10. The optimized production allocation system for high-sulfur gas wells during the entire life cycle of production according to claim 9, characterized in that: The preferred module of the sulfur deposition low risk area production allocation method is specifically used for: When the bottom hole pressure of the gas well is higher than the saturated precipitation pressure of sulfur at the bottom hole of the gas well, the initial production allocation of the gas well before production is quickly determined by analogy method and open-flow method; including: when there is a large difference between the initial production allocation of high-sulfur gas wells determined by analogy method and open-flow method, the initial production allocation obtained by analogy method is preferred; when it is difficult to find a reference for existing production wells under similar geological conditions, the initial production allocation obtained by open-flow method is selected; After the gas well has been producing for a period of time, the modern production decline method is used to fit the production data to obtain the dynamic reserves of the gas well. Further, based on the stable production period requirements during the preparation of the gas reservoir plan, a reasonable production allocation is selected to meet the stable production requirements of high-sulfur gas wells. This production allocation plan is implemented when the gas well has not entered the high-risk area for sulfur deposition.

11. The optimized production allocation system for high-sulfur gas wells during the entire life cycle of production according to claim 9, characterized in that: The preferred module of the production allocation method in high-risk sulfur deposition areas is specifically used for: When the bottom hole pressure of the gas well is in the pressure range where sulfur is saturated and precipitated at the bottom hole of the gas well, the relationship between reservoir physical properties and sulfur saturation is optimized, and then the production capacity equation and sulfur saturation prediction equation considering sulfur deposition are established; Draw production indicator curves under the influence of different sulfur saturation; The production indicator curve is used to determine the reasonable production allocation method of the gas well.

Images