Optimized production allocation method and system for high-sulfur gas wells during the entire production life cycle

Abstract

The present invention discloses a method and system for optimizing production allocation during the entire life cycle production process of a high-sulfur gas well, which relates to the technical field of oil and natural gas exploration and development, including: collecting sulfur-containing gas samples from the bottom of a high-sulfur gas well, and using indoor sulfur solubility test experiments to realize the identification and division of low-risk areas for sulfur deposition and high-risk areas for sulfur deposition under underground reservoir conditions during the entire life cycle production process of the gas well; when the gas well is in a low-risk area for sulfur deposition, a conventional gas well production optimization allocation method is preferably used; when the gas well is in a high-risk area for sulfur deposition, sulfur elemental precipitates in the form of solid particles within this interval, and a gas well production optimization allocation method that takes sulfur deposition into consideration is preferably used. The present invention forms production and development strategies for high-sulfur gas wells at different stages by dividing the low-risk area for sulfur deposition into high-risk areas and adopting different optimization allocation methods, 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.

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 full life cycle production of a high-sulfur gas well. Background Art

[0002] The development of high-sulfur gas reservoirs is often plagued by sulfur particle deposition and clogging, posing a significant challenge to their safe and efficient development. Previous research has shown that during the middle and late stages of high-sulfur gas reservoir development, pressure drop near the wellbore causes large amounts of elemental sulfur particles to precipitate, blocking the reservoir and impacting gas well productivity. When the reservoir sulfur saturation reaches 20%, well productivity can drop by as much as 50%. Under the influence of sulfur deposition, how to optimally allocate production to high-sulfur gas wells and minimize their impact on well productivity has become a critical scientific and production issue in the development of high-sulfur gas reservoirs.

[0003] In the prior art, commonly used production allocation methods for gas wells include the open-flow method, analogy method, production dynamic analysis method, and objective function constraint method. For example, patent document CN109488266A provides a "gas well production allocation method and system." First, the first gas production rate of the gas well is determined using the gas production indicator curve and the minimum critical sand production pressure difference, temperature and pressure data of the casing annulus, tubing anti-external squeeze parameters, and production risk correction coefficient. This first gas production rate is then compared with the economic limit gas production rate, and the minimum of the two is taken as the gas well production allocation value. For example, patent document CN114417716A also provides a "gas well production allocation method, device, electronic device, and medium." First, the constraints that the decision variables need to meet are obtained. Then, an objective function is constructed using the decision variables as independent variables and the received gas well production allocation target as the dependent variable. A gas well production allocation plan is determined using a heuristic algorithm based on the constraints and the objective function, and production is allocated to each gas well according to the production allocation plan. However, these test methods are not suitable for production allocation of high-sulfur gas wells. They have the following problems: (1) 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 optimized production allocation method to solve the problem of optimized production allocation during the entire life cycle of high-sulfur gas reservoir production, especially after sulfur is adsorbed and deposited in the formation in the middle and late stages of development, how to optimize the production allocation of high-sulfur gas wells to reduce the impact of sulfur deposition on gas well productivity. Summary of the Invention

[0004] The present invention aims to provide a method and system for optimizing production allocation during the entire life cycle of a high-sulfur gas well. This method primarily identifies and demarcates low-risk sulfur deposition zones and high-risk sulfur deposition zones in the subsurface near-wellbore area of ​​the gas well during the entire life cycle of the high-sulfur gas well. Based on different scenarios and production stages, the method for optimizing production allocation in the low-risk sulfur deposition zones and the method for optimizing production allocation in the high-risk sulfur deposition zones are selected to achieve optimized production allocation throughout the entire life cycle of the high-sulfur gas well. To achieve the above-mentioned purpose, the present invention provides the following technical solutions:

[0005] The present invention provides a method for optimizing production allocation during the entire life cycle 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 delineate low-risk sulfur deposition areas and high-risk sulfur deposition areas under underground reservoir conditions during the entire life cycle of the gas well.

[0007] Step S102: When the gas well is in a low-risk area for sulfur deposition, a conventional gas well production optimization 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 within this area. It is preferred to adopt a gas well production optimization method that takes sulfur deposition into consideration.

[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. At the same time, the sulfur saturation of the bottom-hole high-sulfur gas sample under the bottom-hole temperature and different development pressure conditions is measured to draw the bottom-hole sulfur solubility curve of the gas well;

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

[0012] 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 entire life cycle is divided into a low-risk area for sulfur deposition and a high-risk area for sulfur deposition.

[0013] Furthermore, the low-risk sulfur deposition zone is a gas well bottom hole pressure range 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 gas, and the sulfur deposition risk is low.

[0014] The high-risk sulfur deposition area is a pressure range where the bottom hole pressure of the gas well is in the saturated precipitation of sulfur 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 bottomhole pressure of a gas well is higher than the saturated precipitation pressure of elemental sulfur at the bottomhole of the gas well, the initial production allocation of the gas well is quickly determined by the analogy method and the open flow method. This includes: when there is a large difference between the initial production allocations of a high-sulfur gas well determined by the analogy method and the open flow method, 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 open flow method is selected;

[0017] After a 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, the relationship between reservoir physical properties and sulfur saturation is optimized, and then a production capacity equation and a sulfur saturation prediction equation considering sulfur deposition are established;

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

[0023] Use production indicator curves to determine the reasonable production allocation method for gas wells.

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

[0025] The production indicator curve under the influence of different sulfur saturations is drawn by using the multi-zone composite horizontal well productivity equation under the effect of sulfur deposition. The production indicator curve under the influence of different sulfur saturations is found at the point where the production deviates from the early straight line and is regarded as the reasonable production rate of the gas well.

[0026] Based on the reasonable production allocation data under different sulfur saturations, a relationship chart between reasonable production allocation value and sulfur saturation under different sulfur saturations was established. At the same time, based on the numerical simulation prediction method, a relationship chart between pressure and production time after sulfur deposition appeared at the bottom of the gas well was established;

[0027] According to the bottom hole pressure of the gas well, the corresponding time node is found on the relationship chart between pressure and production time after sulfur deposition appears at the bottom hole. Then, the corresponding sulfur saturation is found on the relationship chart between sulfur saturation and production time after sulfur deposition appears at the bottom hole. Finally, the reasonable production allocation value under the current degree of sulfur deposition is optimized through the relationship chart between 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 its entire life cycle, the system comprising:

[0029] The module for identifying and demarcating low-risk and high-risk sulfur deposition areas is used to collect sulfur-containing gas samples from the bottom of high-sulfur gas wells. Using indoor sulfur solubility testing, it can identify and demarcate low-risk and high-risk sulfur deposition areas under underground reservoir conditions throughout the production life cycle of the gas well.

[0030] The module for optimizing the production allocation method in low-risk sulfur deposition areas is used to optimize the production allocation method of 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. In this area, sulfur is precipitated in the form of solid particles. It is preferred to adopt a gas well production optimization 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 to:

[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. At the same time, the sulfur saturation of the bottom-hole high-sulfur gas sample under the bottom-hole temperature and different development pressure conditions is measured to draw the bottom-hole sulfur solubility curve of the gas well;

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

[0035] 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 entire 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 production allocation method in the low-risk sulfur deposition area is specifically used to:

[0037] When the bottomhole pressure of a gas well is higher than the saturated precipitation pressure of elemental sulfur at the bottomhole of the gas well, the initial production allocation of the gas well is quickly determined by the analogy method and the open flow method. This includes: when there is a large difference between the initial production allocations of a high-sulfur gas well determined by the analogy method and the open flow method, 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 open flow method is selected;

[0038] After a 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 for high-risk sulfur deposition areas is specifically used to:

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

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

[0042] Use production indicator curves to determine the reasonable production allocation method for gas wells.

[0043] The technical effects and advantages of the present invention are as follows:

[0044] First, the present invention uses indoor sulfur solubility test experiments to accurately identify and divide the low-risk sulfur deposition areas and high-risk sulfur deposition areas during the entire life cycle of high-sulfur gas wells, and then formulates different optimized production allocation methods according to different underground conditions of gas wells. When a high-sulfur gas well is in a low-risk sulfur deposition area in the early stage of development, the analogy method, the open 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 in production 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. 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 bottomhole 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 gas well production capacity, thereby improving the development effect of the gas well.

[0045] Second, the present invention divides sulfur deposition into low-risk areas and high-risk areas, adopts different optimized 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 high-sulfur gas reservoirs in my country.

[0046] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing 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 is a brief introduction to 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 any creative work.

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

[0049] 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;

[0050] Figure 3 This is 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 gas production indication curve and a schematic diagram for determining a reasonable production allocation when the sulfur saturation of a gas well is 20% according to an embodiment of the present invention;

[0052] Figure 5 This is 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 This 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. DETAILED DESCRIPTION

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts 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 This is a flow chart of a method for optimizing production allocation during the entire life cycle of a high-sulfur gas well according to the present invention. Figure 1 As shown, the method includes the following steps:

[0057] Step S101, identifying and demarcating the low-risk and high-risk sulfur deposition areas at the bottom of high-sulfur gas wells: collecting sulfur-containing gas samples from high-sulfur gas wells, and using indoor sulfur solubility testing experiments to identify and demarcate the low-risk and high-risk sulfur deposition areas under underground reservoir conditions during the entire life cycle of the gas well production.

[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 bottomhole temperature and pressure of the gas well; the sulfur-containing gas sample is a bottomhole gas sample of a high-sulfur gas well, and is a bottomhole gas sample under the original conditions before the gas well is put into production. After obtaining the bottomhole sulfur-containing gas sample, a solubility tester is used to measure the sulfur content in the bottomhole high-sulfur gas sample. At the same time, the sulfur saturation of the bottomhole high-sulfur gas sample under the bottomhole temperature of the gas well and different development pressure conditions is measured to draw a bottomhole sulfur solubility curve of the gas well.

[0060] Furthermore, the bottom hole high sulfur content gas sample is a high temperature, high pressure, high sulfur content 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 was put into production was marked on the sulfur solubility curve. At the same time, the sulfur solubility prediction empirical formula was obtained through sulfur solubility test experiments (the fitted empirical formula was 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 entire 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 when the bottom of the gas well pressure 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 a dissolved form in the high-sulfur gas, and the risk of sulfur deposition is low. The high-risk area for sulfur deposition is the pressure interval when the bottom of the gas well pressure 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 bottomhole pressure of a gas well is higher than the saturated precipitation pressure of elemental sulfur at the bottomhole, sulfur deposition has no effect on the gas well's productivity, and the optimized production allocation of the gas well does not need to be considered. The initial production allocation of a gas well can be quickly determined using the analogy method and the open-flow method. When there is a significant difference between the initial production allocations of a high-sulfur gas well determined by the analogy method and the open-flow method, the initial production allocation determined by the analogy method is preferred. When it is difficult to find a reference to an existing producing well under similar geological conditions, the initial production allocation determined by the open-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-sulfur gas well bottom-hole sulfur deposition high-risk area is preferred: when the gas well is in the sulfur deposition high-risk area, sulfur is precipitated in the form of solid particles in this area, and the gas well production optimization production allocation method considering sulfur deposition is preferably adopted.

[0073] Step S103 specifically includes the following steps:

[0074] First, when the bottomhole pressure of the gas well is in the pressure range where sulfur is saturated and precipitated at the bottomhole of the gas well, sulfur precipitates from the sulfur-containing gas in the form of solid particles. After the sulfur deposits precipitate, 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 impact 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 and sulfur saturation prediction equation considering sulfur deposition are established.

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

[0076] lnk 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:

[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 sulfur deposition refers to a productivity equation for multi-zone composite high-angle wells under 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 a highly deviated well under the effect of sulfur deposition 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] Next, production indicator curves under different sulfur saturations are drawn. This production indicator curve under different sulfur saturations is drawn using a multi-zone composite horizontal well productivity equation under sulfur deposition. The point where the production deviates from the initial straight line is determined as the optimal production rate for the gas well. Based on the optimal production allocation data under different sulfur saturations, a relationship chart between the optimal production allocation value and sulfur saturation is established. Furthermore, a numerical simulation prediction method is used to establish a relationship between pressure changes at the bottom of the gas well and production time after sulfur deposition occurs.

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

[0093] Example:

[0094] Step S101: Sulphur-containing gas samples are collected from the high-sulfur gas well, and an indoor sulphur solubility test is performed to identify and demarcate low-risk and high-risk sulphur deposition 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-hole gas sample of a high-sulfur gas well, and is a bottom-hole gas sample under original conditions before the gas well is put into production. After obtaining the bottom-hole gas sample, the sulfur content in the bottom-hole high-sulfur gas sample is determined using a solubility tester. At the same time, the sulfur saturation of the bottom-hole high-sulfur gas sample at a bottom-hole temperature of 90°C and different development pressures is determined. A bottom-hole 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 sulfur solubility test experiments, an 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. Figure 2 As shown in the figure, based on 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 entire 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 content gas sample is a high temperature, high pressure, high sulfur content 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 using gas chromatography-mass spectrometry.

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

[0100] The high-risk sulfur deposition area is a pressure range where the bottom hole pressure of the gas well is in the saturated precipitation of sulfur. 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.

[0104] Step S102: When the gas well is in a low-risk area for sulfur deposition, a production optimization method that does not consider sulfur deposition is preferably used.

[0105] When the bottomhole pressure of a gas well is higher than the saturated precipitation pressure of elemental sulfur at the bottomhole, sulfur deposition has no effect on the gas well's productivity, and the optimized production allocation of the gas well does not need to be considered. The initial production allocation of a gas well can be quickly determined using the analogy method and the open-flow method. When there is a significant difference between the initial production allocations of a high-sulfur gas well determined by the analogy method and the open-flow method, the initial production allocation determined by the analogy method is preferred. When it is difficult to find existing production wells with similar geological conditions as a reference, the initial production allocation determined by the open-flow method is selected.

[0106] After a 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. Furthermore, based on the stable production period required 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 production 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 within this area, and a production optimization method that takes sulfur deposition into consideration is preferably used.

[0111] When the bottom hole pressure of a gas well is in the pressure range where 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 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 impact of sulfur deposition on the seepage capacity of the gas well. The relationship between reservoir physical properties and sulfur saturation can be optimized. Subsequently, a production capacity equation considering sulfur deposition and a sulfur saturation prediction equation are established, and production indicator curves (i.e., gas production indicator curves) under the influence of different sulfur saturations are drawn. The gas production indicator curves are used to determine a reasonable production allocation method for the gas well.

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

[0113] lnk 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 This is 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. 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 sulfur deposition refers to a productivity equation for multi-zone composite high-angle wells under sulfur deposition, established on the basis of reservoir core physical properties, sulfur saturation model, and sulfur deposition saturation prediction model.

[0124] Preferably, the productivity equation of a highly deviated well under the effect of sulfur deposition 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, which 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 bottom radius of the well, 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 drawing the production indicator curve under the influence of different sulfur saturations through the multi-zone composite horizontal well productivity equation under the effect of sulfur deposition, and finding the point where the production deviates from the early straight line as the reasonable production rate of the gas well. Figure 4 This is a gas production indication curve when the sulfur saturation of the gas well is 20% according to an embodiment of the present invention. Figure 4 As shown in FIG, according to the gas production indicator 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 sulfur saturation at different bottom sulfur saturations of the gas well according to the embodiment of the present invention is shown in the figure. The expression is as follows:

[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 changes in formation pressure and production time after saturation precipitation of elemental sulfur in an embodiment of the present invention. Further fitting is performed to obtain a relationship between formation pressure and time, which is expressed 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 between pressure and production time after sulfur deposition appears at the bottom hole. Then, the corresponding sulfur saturation is found on the relationship chart between sulfur saturation and production time after sulfur deposition appears at the bottom hole. Finally, the reasonable production allocation value under the current degree of sulfur deposition is optimized through the relationship chart between reasonable production allocation value and sulfur saturation under different sulfur saturations.

[0139] The present invention also discloses an optimized production allocation system for high-sulfur gas wells during the entire production life cycle. Figure 7 This is a schematic diagram of an optimized production allocation system for a high-sulfur gas well during the entire production life cycle of 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 from the bottom of a high-sulfur gas well, and use indoor sulfur solubility test experiments to realize the identification and division of sulfur deposition low-risk areas and sulfur deposition high-risk areas under underground reservoir conditions during the entire life cycle production process of the gas well; 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; and a sulfur deposition high-risk area production allocation method optimization module 203, which is used to optimize the gas well production allocation method that takes sulfur deposition into consideration when the gas well is in the sulfur deposition high-risk area.

[0140] Furthermore, the module 201 for identifying and dividing low-risk and high-risk sulfur deposition areas is specifically configured to: after obtaining a bottom-hole sulfur-containing gas sample, determine the sulfur content in the bottom-hole high-sulfur gas sample using a solubility tester, and simultaneously determine 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 draw a bottom-hole sulfur solubility curve for the gas well; mark the original sulfur content before the gas well is put into production on the sulfur solubility curve, and simultaneously obtain an empirical formula for predicting sulfur solubility through a sulfur solubility test experiment; obtain the critical pressure condition for the precipitation of sulfur at the bottom of the gas well based on the sulfur solubility curve and the original sulfur content, and divide the underground production process of the gas well into a low-risk sulfur deposition area and a high-risk sulfur deposition area through the critical pressure node for the saturated precipitation of sulfur.

[0141] Furthermore, the production allocation method optimization module 202 in the low-risk sulfur deposition area is specifically used to: when the bottomhole pressure of the gas well is higher than the saturated precipitation pressure of elemental sulfur at the bottomhole of the gas well, quickly determine the initial production allocation of the gas well by analogy and open-flow method; including: when there is a large difference between the initial production allocations of high-sulfur gas wells determined by analogy and open-flow method, preferably the initial production allocation obtained by analogy; when it is difficult to find an existing production well reference under similar geological conditions, select the initial production allocation obtained by open-flow method; after the gas well has been in production for a period of time, use the modern production decline method to fit the production data to obtain the dynamic reserves of the gas well, and further, based on the stable production period requirement during the preparation of the gas reservoir plan, optimize the reasonable production allocation to meet the stable production requirement of the high-sulfur gas well, and execute the production allocation plan when the gas well has not entered the high-risk sulfur deposition area.

[0142] Furthermore, the production allocation method optimization module 203 in the high-risk sulfur deposition area is specifically used to: when the bottom hole pressure of the gas well is in the pressure range when the bottom hole pressure of the gas well is saturated and precipitated by sulfur element, optimize the relationship between reservoir physical properties and sulfur saturation, then establish a production capacity equation and a sulfur saturation prediction equation considering sulfur deposition, draw production indicator curves under the influence of different sulfur saturations, and use the production indicator curves to determine a reasonable production allocation method for the gas well.

[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, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or 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 scope of protection 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 delineate low-risk sulfur deposition areas and high-risk sulfur deposition areas under underground reservoir conditions during the entire life cycle of the gas well. 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. At the same time, the sulfur saturation of the bottom-hole high-sulfur gas sample under the bottom-hole temperature and different development pressure conditions is measured to draw the bottom-hole sulfur solubility curve of the gas well; Mark the original sulfur content before the gas well is put into production on the sulfur solubility curve, and obtain the empirical formula for sulfur solubility prediction through sulfur solubility test experiments; Based on the sulfur solubility curve and the original sulfur content, the critical pressure condition for sulfur precipitation at the bottom of the gas well is obtained. Based on the critical pressure node for saturated sulfur precipitation, the underground production process of the gas well throughout its life cycle is divided into low-risk sulfur deposition areas and high-risk sulfur deposition areas. Step S102: When the gas well is in a low-risk area for sulfur deposition, a conventional gas well production optimization method is selected; Step S103: When the gas well is in a high-risk area for sulfur deposition, sulfur is precipitated in the form of solid particles within this area, and a gas well production optimization method that takes sulfur deposition into consideration is selected.

2. The method for optimizing production allocation during the entire life cycle of a high-sulfur gas well according to claim 1, characterized in that: The low-risk sulfur deposition zone is a gas well bottom hole pressure range 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 gas, and the sulfur deposition risk is low. The high-risk sulfur deposition area is a pressure range where the bottom hole pressure of the gas well is in the saturated precipitation of sulfur 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.

3. The method for optimizing production allocation during the entire life cycle of a high-sulfur gas well according to claim 1, characterized in that: Step S102 specifically includes: When the bottomhole pressure of a gas well is higher than the saturated precipitation pressure of elemental sulfur at the bottomhole of the gas well, the initial production allocation of the gas well is quickly determined using the analogy method and the open flow method. Specifically, when there is a significant difference between the initial production allocations of a high-sulfur gas well determined by the analogy method and the open flow method, the initial production allocation obtained by the analogy method is selected; when it is difficult to find a reference to an existing production well under similar geological conditions, the initial production allocation obtained by the open flow method is selected. After a 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. Furthermore, 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.

4. The method for optimizing production allocation during the entire life cycle of a high-sulfur gas well according to claim 3, 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.

5. The method for optimizing production allocation during the entire life cycle 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, the relationship between reservoir physical properties and sulfur saturation is selected, 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 saturations; Use production indicator curves to determine the reasonable production allocation method for gas wells.

6. The method for optimizing production allocation during the entire life cycle of a high-sulfur gas well according to claim 5, characterized in that: The method for determining the reasonable production allocation of a gas well using a production indicator curve includes: Production indicator curves under different sulfur saturations are drawn using the multi-zone composite horizontal well productivity equation under sulfur deposition, and the production deviation from the early straight line is found as the reasonable production rate of the gas well. Based on the reasonable production allocation data under different sulfur saturations, a relationship chart between reasonable production allocation value and sulfur saturation under different sulfur saturations was established. At the same time, based on the numerical simulation prediction method, a relationship chart between pressure and production time after sulfur deposition appeared at the bottom of the gas well was established; According to the bottom hole pressure of the gas well, the corresponding time node is found on the relationship chart between pressure and production time after sulfur deposition appears at the bottom hole. Then, the corresponding sulfur saturation is found on the relationship chart between sulfur saturation and production time after sulfur deposition appears at the bottom hole. Finally, the reasonable production allocation value under the current degree of sulfur deposition is selected through the relationship chart between reasonable production allocation value and sulfur saturation under different sulfur saturations.

7. An optimized production allocation system for high-sulfur gas wells during their entire life cycle, characterized in that: The system comprises: The module for identifying and demarcating low-risk and high-risk sulfur deposition areas is used to collect sulfur-containing gas samples from the bottom of high-sulfur gas wells and, through indoor sulfur solubility testing, to identify and demarcate low-risk and high-risk sulfur deposition areas under underground reservoir conditions during the entire life cycle of the gas well. Specifically, the module is used to: 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. At the same time, the sulfur saturation of the bottom-hole high-sulfur gas sample under the bottom-hole temperature and different development pressure conditions is measured to draw the bottom-hole sulfur solubility curve of the gas well; Mark the original sulfur content before the gas well is put into production on the sulfur solubility curve, and obtain the empirical formula for sulfur solubility prediction through sulfur solubility test experiments; Based on the sulfur solubility curve and the original sulfur content, the critical pressure condition for sulfur precipitation at the bottom of the gas well is obtained. Based on the critical pressure node for saturated sulfur precipitation, the underground production process of the gas well throughout its life cycle is divided into low-risk sulfur deposition areas and high-risk sulfur deposition areas. The module for selecting production allocation methods in low-risk sulfur deposition areas is used to select production optimization methods for conventional gas wells when the gas well is in a low-risk sulfur deposition area. The module for selecting production allocation methods in high-risk sulfur deposition areas is used when a gas well is in a high-risk sulfur deposition area. In this area, sulfur is precipitated in the form of solid particles. The module selects a production allocation method that optimizes gas well production by taking sulfur deposition into consideration.

8. The optimized production allocation system for high-sulfur gas wells during the entire production life cycle according to claim 7, characterized in that: The sulfur deposition low risk area production allocation method selection module is specifically used to: When the bottom hole pressure of a gas well is higher than the saturated precipitation pressure of elemental sulfur at the bottom hole of the gas well, the initial production allocation of the gas well is quickly determined by the analogy method and the open flow method. Specifically, when there is a large difference between the initial production allocations of a high-sulfur gas well determined by the analogy method and the open flow method, the initial production allocation obtained by the analogy method is selected; When it is difficult to find existing production wells with similar geological conditions, the initial production allocation obtained by the open flow method is selected; After a 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. Furthermore, 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.

9. The optimized production allocation system for high-sulfur gas wells during the entire production life cycle according to claim 7, characterized in that: The sulfur deposition high risk area production allocation method selection module is specifically used to: When the bottom hole pressure of the gas well is in the pressure range where sulfur is saturated and precipitated, the relationship between reservoir physical properties and sulfur saturation is selected, 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 saturations; Use production indicator curves to determine the reasonable production allocation method for gas wells.

Images