Stable production method suitable for crack production control compact sandstone reservoir with edge and bottom water

Abstract

The invention relates to the technical field of gas reservoir development, in particular to a stable production method suitable for a crack production control compact sandstone reservoir with edge and bottom water. The method comprises the following steps: step 1, collecting geological exploration data of a target area, summarizing geological characteristics of a gas reservoir of a beihe river group in the target area, obtaining gas reservoir production dynamic characteristics of the target area according to production data of a pilot production well, and establishing a production parameter stable production allocation scheme for the first time; 2, according to the production parameter stable production allocation schemes, the production parameter change conditions of the single well in the target area under different production allocation schemes are calculated and analyzed; a secondary production parameter stable production allocation scheme is carried out; and 3, according to the stable production allocation scheme finely adjusted in the step 2, the production dynamic state of the gas well in the target area is tracked regularly, and stable production of the gas well in the target area is achieved. According to the characteristics of the gas reservoir, a differential production allocation scheme and a production system based on geological characteristics are designed, the development efficiency and the productivity of the gas reservoir of the Taihe River group are greatly improved, and the development cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of gas reservoir development, and particularly relates to a stable production method applicable to a fractured production-controlled tight sandstone reservoir with edge and bottom water. Background Art

[0002] In recent years, the exploration well Xinsheng 1 and the development evaluation well Xinsheng 101 with the Xujiahe Formation Member 2 as the target layer have both obtained industrial gas flows during testing, and the subsequent production test conditions are good, indicating that the Xujiahe Formation gas reservoir in the eastern slope of western Sichuan, mainly composed of matrix pores and fractures, has good development and evaluation potential and has attracted much attention. The aforementioned eastern slope of western Sichuan refers to the eastern slope area of the western Sichuan depression in a geological sense; the Xujiahe Formation Member 2 gas reservoir in the eastern slope area of western Sichuan has a relatively large burial depth. Due to the influence of tectonic movements with multiple periods and different principal stress directions, faults are generally well developed. Due to the complex structure, different basic elements of each fault and varying degrees of fracture development, the production effects vary. Among them, in the eastern slope area of western Sichuan Hexingchang The Xujiahe Formation gas reservoir near the fault development has a relatively high degree of fracture development and is a high-yield block of the Xujiahe Formation gas reservoir in the eastern slope area of western Sichuan.

[0003] However, gas reservoirs with unique gas reservoir geological characteristics such as the Xujiahe Formation gas reservoir in the eastern slope area of western Sichuan usually have the following complex characteristics: (1) The gas reservoir is located on the transition zone between the western Sichuan depression and the central Sichuan uplift, with a complex structure and various structural styles; (2) The gas-water relationship is complex, with different gas-water relationships in different regions, and there are edge water and bottom water, without a unified gas-water boundary. (3) It is a typical ultra-low porosity - tight reservoir, with an average porosity of 3.54%, good permeability, an average permeability of 0.97 mD, and a matrix permeability of 0.11 mD. (4) Overall, it is mainly composed of underwater distributary channel deposits on the delta front, with local development of the side edge of the distributary channel and underwater interdistributary bays. (5) The cuttings are mainly argillaceous siltstone and silty mudstone.

[0004] In view of the complex structure and complex gas-water distribution characteristics of the Xujiahe Formation gas reservoir in Hexingchang, eastern slope area of western Sichuan, the traditional production mode of "pressure maintenance, stable production, and production control" cannot meet the requirements of stable production of this gas reservoir. First, the existence of microfractures will improve the pore and permeability conditions of the sandstone. The siltstone has good wettability, and the formation water with a large amount of water deep in the formation is easy to penetrate into the fractures, causing "explosive water flooding". Second, due to the relatively high content of carbon dioxide components in the gas reservoir, carbon dioxide corrosion occurs to the wellbore, surface pipelines, and equipment. Moreover, the Xujiahe Formation gas reservoir in Hexingchang, eastern slope area of western Sichuan has a deep burial depth, and the formation water has a high calcium ion content, which is easy to scale at the water accumulation areas such as the diameter change of the surface pipeline, hindering the migration of natural gas. Therefore, the development research and production management of this gas reservoir are more difficult than those of general tight sandstone gas reservoirs, and the development cost is high. Summary of the Invention

[0005] The object of the present invention is to: aiming at the problems in the prior art that the reservoirs of the Xujiahe gas reservoir are ultra-dense, with strong heterogeneity of fractures, complex gas-water distribution, and mud invasion, resulting in complex "four-property relationships" of the reservoir and great difficulty in accurately identifying gas and water layers, a stable production method for fractured-production-controlled tight sandstone reservoirs with edge and bottom water is provided. According to the characteristics of the gas reservoir, a differential production allocation plan and production system based on geological characteristics are designed to improve the development efficiency and production capacity of the Xujiahe gas reservoir and reduce the development cost.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A stable production method for fractured-production-controlled tight sandstone reservoirs with edge and bottom water, specifically including the following steps:

[0008] Step 1: Collect geological exploration data of the target area, obtain the geological characteristics of the fractured-production-controlled tight sandstone reservoir with edge and bottom water in the target area, and obtain the production dynamic characteristics of the gas reservoir in the target area according to the production data of the test production wells, and initially establish a stable production allocation plan for the production parameters of the wells to be allocated; in Step 1, the test production wells and the wells to be allocated need to be in the same fracture system and have similar geological and dynamic characteristics;

[0009] Step 2: According to the stable production allocation plan of the production parameters described in Step 1, calculate and analyze the changes in the production parameters of individual wells in the target area under different production allocation plans; and perform a secondary stable production allocation plan for the production parameters.

[0010] Step 3: According to the refined stable production allocation plan in Step 2, regularly track the production dynamics of the gas wells in the target area to achieve stable production of the gas wells in the target area.

[0011] In the technical solution of the present invention, the fractured-production-controlled tight sandstone reservoirs with edge and bottom water in the eastern slope area of western Sichuan have many geological element configuration relationships and complex gas-water relationships. The Xujiahe gas reservoir in Hexingchang is the most typical. The Xujiahe gas reservoir has diverse geological element configuration relationships and complex gas-water relationships. The original production allocation of gas wells often does not match the actual production situation. High production allocation causes negative impacts such as water invasion and too fast pressure decline rate, thus affecting the ultimate recovery rate of gas wells. Low production allocation cannot effectively release the production capacity of gas wells, and it is impossible for oil and gas production enterprises to recover their investments in a timely manner. Therefore, during the production process of gas wells, technical personnel need to dynamically adjust the production allocation according to parameters such as gas well pressure, gas production, water production, and water body properties to ensure stable production of gas wells, formulate a scientific production rate, and improve the ultimate recovery rate.

[0012] In the technical solution of the present invention, due to the strong randomness and large scale difference in the distribution of natural fractures in the Xujiahe Formation gas reservoir, there are both small-scale microfractures and large-scale faults and fractures, etc., resulting in complex water invasion laws in fractured edge water and gas reservoirs. It is relatively difficult to determine a reasonable production scale, especially the reasonable production pressure difference value of gas wells is difficult to obtain, which also brings great uncertainty to the preparation of gas reservoir development plans and the adjustment of technical countermeasures. Therefore, accurately determining the reasonable production pressure difference of production wells is of great significance for improving the development effect and benefits of fractured edge water and gas reservoirs.

[0013] In the technical solution of the present invention, due to reasons such as the ultra-tight reservoir of the Xujiahe-2 gas reservoir, strong fracture heterogeneity, complex gas-water distribution, and mud invasion, the "four-property relationship" of the reservoir is complex, and it is difficult to accurately identify gas and water layers. The inventor found through summary of practical experience that: the calculation and analysis accuracy is relatively high according to the following method, and the judgment is also relatively accurate.

[0014] Specifically, in step 2, the specific calculation and analysis process includes the following steps:

[0015] Step 21: According to the formation, structure, sedimentary microfacies, and reservoir characteristics of the fracture system where the Xujiahe Formation gas well is located, taking permeability as the first quantitative evaluation factor, establish a reservoir classification and evaluation standard, which is divided into three grades: good, relatively good, and medium; among them, for fracture-porous reservoirs with a permeability ≥ 100 mD, a porosity ≥ 5%, a pore median radius ≥ 0.06 μm, and favorable diagenetic facies being chlorite cementation facies and fracture-dissolution facies, they are evaluated as good reservoirs; for fracture-porous reservoirs with a permeability between 10 - 100 mD, a porosity between 4 - 5%, a pore median radius between 0.04 - 0.06 μm, and favorable diagenetic facies being fracture-dissolution facies and dissolution facies, they are evaluated as relatively good reservoirs; for fracture-porous reservoirs with a permeability between 0.3 - 10 mD, a porosity between 3 - 4%, a pore median radius between 0.02 - 0.04 μm, and favorable diagenetic facies being dissolution facies, they are evaluated as medium reservoirs; for porous reservoirs with a permeability between 0.03 - 0.3 mD, a porosity ≥ 3%, a pore median radius between 0.005 - 0.02 μm, and favorable diagenetic facies being fracture-dissolution facies and dissolution facies, they are evaluated as medium reservoirs.

[0016] Step 22: Determine the fluid properties such as natural gas and water bodies in different fracture systems. Based on the changes in the chemical properties of the water body in a single well and its water body distribution characteristics, combined with the research results of the accumulation and evolution of the gas reservoir, conduct research on the occurrence status of the water body. The occurrence status of the water body in the gas reservoir in the target area is divided into four categories: gaseous water, bound water, capillary water, and free water. Among them, gaseous water coexists with natural gas in a gaseous form under high temperature and high pressure, with a low salinity generally lower than 1000 mg / L. As the production layer of the gas well is opened and the temperature and pressure conditions change, it enters the surface and is produced in a liquid form. The water body with a small volume is gaseous water. Retained on the surface of hydrophilic sand grains in a thin film form under the action of surface molecular forces, with a total salinity generally lower than 5000 mg / L. As the production layer of the gas well is opened and the temperature and pressure conditions change, it enters the surface and is produced in a liquid form. Part of the bound water will become mobile water and flow in the production layer, which is bound water. Due to the poor reservoir quality (tight - ultra - tight, strong heterogeneity), the water body retained in the fine pore throats under the restraint of capillary force. As the production / displacement pressure difference increases, part of the capillary water can be converted into free water and flow. The water body with a salinity generally in the range of 5000 mg / L - 60000 mg / L is capillary water. The water body that can move freely under the action of gravity is commonly found in sand bodies with good reservoir physical properties where there is no effective gas injection. Long - term water - rock interaction results in a relatively high salinity of the water body, in the range of 60353 - 186254 mg / L, with an average of 82403 mg / L, which is free water.

[0017] In the technical solution of the present invention, the differences in natural gas components between different layers of the gas reservoir in the target area are not significant, belonging to a dry gas reservoir. The natural gas composition is mainly methane. The average methane content in each gas sample is 96.60%, the average carbon dioxide content is 1.27%, and there is no hydrogen sulfide. The measured average density of natural gas is 0.70 kg / m 3 . The gas - water distribution in the gas reservoir in the target area is complex, without a unified gas - water interface.

[0018] Step 23: Calculate the dynamic reserves according to the formation pressure, seepage characteristics, etc. of different fracture systems, conduct gas production allocation for gas wells, and use the four indicators of wellhead pressure, gas production, water production, and water body properties that can directly reflect the production status of gas wells as the monitoring indicators for reasonable gas production allocation and stable production of gas wells. In view of the fact that most gas wells in the Xu - 2 gas reservoir have been in production for a long time and have entered the decline stage, and formation temperature and pressure data have been obtained during the well testing process. Combining with the production history data of gas wells, the production decline analysis method is used to calculate the dynamic reserves of gas wells. Among them, the Blasingame dynamic analysis method is the most typical. By using the material balance time to "approximately convert" the variable - flow problem into a constant - flow problem and fitting it with the typical curve of constant - production pressure drop analysis, the production dynamic characteristics of gas wells are analyzed. According to the principle and process of this method, the production dynamic analysis software Topaze of Kappa Company has been formed.

[0019] The theoretical basis of the Blasingame method is based on a closed elastic drive system, which satisfies the pseudo-steady state flow condition (PSS) in the middle and late stages of production, that is, the fixed production pressure drop is linearly related to the material balance time.

[0020]

[0021]

[0022]

[0023]

[0024]

[0025] Where Δp(t) = p i - p(t), Δp(t) represents the production pressure drop, with the unit of MPa; N p represents the cumulative gas production of the gas well, with the unit of m 3 ; N represents the original controlled reserves of the gas well, with the unit of m 3 ; μ o represents the viscosity at the current average pressure , with the unit of mPa·s, Bo represents the volume factor at the current average pressure , with the unit of sm 3 / m 3 ; B oi —The volume factor at the original formation pressure Pi, with the unit of sm 3 / m 3 ; c t —The comprehensive compressibility factor, with the unit of 1 / MPa; C A represents the gas reservoir shape factor, dimensionless; A represents the controlled area, m 2 ; S represents the pseudo-skin factor (equivalent vertical well), dimensionless.

[0026] Blasingame further defines three types of flow diagnostic functions to identify the flow state, namely:

[0027] (1) Flow function

[0028]

[0029] (2) Flow integral function

[0030]

[0031] (3) Flow integral derivative function

[0032]

[0033] Make the differential pressure per unit production Δp / q from the variable production rate and flowing pressure data (pseudo-steady flow period controlled by the boundary) of long-term production gas wells o versus the material balance time plot, showing a linear relationship, from which the single-well controlled reserves N are estimated from the slope.

[0034] For gas wells, first define the pseudo-pressure and material balance pseudo-time:[[]]

[0035]

[0036]

[0037] Assume that the pseudo-pressure and pseudo-time can completely linearize the gas reservoir seepage equation. Under the pseudo-steady flow state (PSS) controlled by the boundary, the fixed-production pressure drop (pseudo-pressure) has a linear relationship with the pseudo-time:

[0038]

[0039]

[0040]

[0041]

[0042] Note that in the calculation of the material balance pseudo-time the average formation pressure at the current cumulative production needs to be cited which is closely related to the original reserves of the gas reservoir. Through and the straight-line fitting trial and error method, the original reserves can be searched and determined from the variable production rate and flowing pressure data (pseudo-steady flow period controlled by the boundary) of long-term production wells.

[0043] The Blasingame method is based on the flow rate function In this form, the pressure error may be amplified, resulting in the variation of the diagnostic curve. However, when the gas production index is low in the later production stage, the influence of the pressure error can be ignored. Therefore, in the Blasingame diagnostic curve of actual data, the part that can reflect the formation flow characteristics is the flow rate function in the later stage (i.e., the gas production index). Thus, considering the errors in actual production data and the conversion error of the bottom-hole flowing pressure, when fitting the Blasingame curve, it is necessary to take into account the flow rate, the integral of the flow rate, and the derivative line of the integral of the flow rate, and perform trend fitting. At the same time, the Blasingame curve fitting requires the gas well production to be relatively stable. Multiple well shut-ins or large-scale production adjustments will affect the shape of the Blasingame diagnostic curve, resulting in a decrease in the accuracy of the analysis results.

[0044] ​Step 24: Install a digital pressure gauge at the wellhead, a flowmeter in the gas production process, and a digital liquid level gauge in the liquid storage tank to achieve minute-level tracking of pressure, production volume, and water production volume. Monitor the changes in water body properties through daily manual chloride titration, total iron measurement, etc.

[0045] Step 25: Based on the dynamic and static characteristics of similar fracture systems, clarify the reasonable range of changes in stable production parameters and the types of gas well production anomalies corresponding to different parameter combinations, and adjust the development strategy in a timely manner. The dynamic characteristics include the gas saturation and stable production volume of the fracture system, and the static characteristics include the ancient tectonic position, current tectonic position, fracture characteristics, effective fracture density strip, and high-quality reservoir thickness of the fracture system. Among them, for gas wells with ancient and current tectonic positions both at high positions, fracture characteristics being fourth-level fractures, effective fracture density strip > 0.8 m, high-quality reservoir thickness ≥ 10 m, gas saturation ≥ 60%, and stable production volume ≥ 200,000 m³ / day, the production allocation recommendation is 300,000 - 500,000 m³ / day. For gas wells with ancient tectonic position at high position, ancient tectonic position at relatively high position, fracture characteristics being fourth-level fractures, effective fracture density strip between 0.5 - 0.8 m, high-quality reservoir thickness ≥ 10 m, gas saturation ≥ 60%, and stable production volume ≥ 100,000 m³ / day, the production allocation recommendation is 70,000 - 270,000 m³ / day. For gas wells with ancient tectonic position at high position, ancient tectonic position at relatively high position, fracture characteristics being third-level or fifth / sixth-level fractures, effective fracture density strip between 0.3 - 0.5 m, high-quality reservoir thickness ≥ 20 m, gas saturation ≥ 55%, and stable production volume ≥ 60,000 m³ / day, the production allocation recommendation is 30,000 - 200,000 m³ / day. For gas wells with ancient tectonic position at high position, ancient tectonic position at high position, fracture characteristics being undeveloped fractures, matrix reservoir, and gas saturation ≥ 50%, they cannot build production naturally and have been flooded, and processes such as foam drainage and gas lift are used to drain water.

[0046] In the stable production allocation scheme of the secondary production parameters of the present invention, the method for obtaining the selected parameters is simple and does not require excessive investment. Secondly, the selected parameters are highly representative and can intuitively reflect the production status of gas wells. Moreover, a dynamic development thinking is used to track the production status of gas wells, achieving "one well, one time, one strategy", further ensuring the stable production of gas wells throughout their life cycle.

[0047] As a preferred scheme of the present invention, in step 2, the types of gas well production anomalies include the following five categories:

[0048] Water invasion, liquid accumulation in the wellbore, tubing corrosion, blockage at the wellhead throttle or in the gas transmission pipeline, and abnormal metering system.

[0049] As a preferred scheme of the present invention, for each specific type of gas well production anomaly, the adjustment measurement strategy is as follows:

[0050] a. When water invasion occurs, adjust through formation water shutoff;

[0051] b. When wellbore liquid loading occurs, adjust by injecting foam drainage agent into the wellbore;

[0052] c. When tubing corrosion occurs, adjust by injecting corrosion inhibitor into the wellbore;

[0053] d. When blockage occurs at the wellhead throttle or in the gas transmission pipeline, adjust by injecting antifreeze agent through the process;

[0054] e. When the metering system malfunctions, the adjustment countermeasures are: cleaning the orifice plate inspection hole, purging the pressure guiding pipe, or calibrating and replacing the transmitter.

[0055] When abnormal conditions occur in a gas well, timely response measures are very necessary. More importantly, accurate judgment of gas well production abnormalities is required. If the judgment is incorrect and wrong response strategies are adopted, the best intervention time will be missed, resulting in a decrease in gas reservoir development efficiency.

[0056] The difficulty of the technical solution of the present invention also lies here, which requires high capabilities of technical personnel and the integration of multiple specialties such as geology, development, and gas production technology. Second, high requirements are placed on the accuracy and timeliness of obtaining various parameters. Only by accurately and timely obtaining data can abnormalities be judged and maintenance measures be carried out in advance.

[0057] Specifically, different types of gas well production abnormalities correspond to different parameter change characteristics. For the water invasion type, the corresponding parameter changes are: the wellhead pressure decreases, the gas production rate decreases, the water production rate increases, and the chloride ion value increases;

[0058] For abnormalities of the wellbore liquid loading type, the corresponding parameter changes are: the wellhead pressure decreases, the gas production rate decreases, the water production rate decreases, and the chloride ion value remains unchanged;

[0059] For abnormalities of the tubing corrosion type, the corresponding parameter changes are: the wellhead pressure remains unchanged, the gas production rate remains unchanged, the water production rate remains unchanged, and the iron ion content increases;

[0060] For abnormal conditions of blockage at the wellhead throttle or in the gas transmission pipeline, the corresponding parameter changes are: the wellhead pressure rises, the gas production rate decreases, the water production rate decreases, and the chloride ion value remains unchanged;

[0061] For abnormal conditions of the metering system, the corresponding parameter changes are: the wellhead pressure remains unchanged, the gas production rate suddenly changes, the water production rate remains unchanged, and the chloride ion value remains unchanged. Specifically, the sudden change in gas production rate means that the average gas production rate in the current 10 minutes is less than 50% of the average gas production rate in the previous 10 minutes, or the average gas production rate in the current 10 minutes is higher than 150% of the average gas production rate in the previous 10 minutes.

[0062] As a preferred solution of the present invention, in step 1, the geological characteristics of the gas reservoir are specifically:

[0063] According to the previous research data: The depth of the Xujiahe Formation Member 2 gas reservoir in the eastern slope area of western Sichuan is large. Due to the influence of tectonic movements with different principal stress directions in multiple periods, faults are generally well-developed. Due to the complex structure, the basic elements of each fault are different, and the degree of fracture development varies, so the production effects are different. The Hexingchang Xujiahe Formation gas reservoir in the eastern slope area of western Sichuan is close to the fracture zone where fractures are developed, and it is a high-production area of the Xujiahe Formation Member 2 gas reservoir in the eastern slope area of western Sichuan.

[0064] Natural fractures are high-quality natural gas transmission channels. The Xujiahe Formation Member 2 gas reservoir is mainly a tight sandstone gas reservoir dominated by siltstone. The surrounding siltstone has good wettability, making it conducive to the accumulation of water at the fractures. Once the gas-water distribution near the production horizon changes suddenly, the fractures are easily occupied by formation water, blocking the flow of natural gas and causing the "water lock" phenomenon. However, the gas-water distribution of each level of fault is different, resulting in a complex gas-water distribution in the Hexingchang Xujiahe Formation gas reservoir in the eastern slope area of western Sichuan, without a unified gas-water interface. The formation water with a large amount of water in the deep part is easy to penetrate into the fractures, triggering "violent water flooding". Therefore, in order to avoid the influence of "water invasion", it is necessary to obtain more production data through pilot production, master the production laws of gas wells, formulate reasonable and effective management methods, and stabilize the efficient production of gas wells in the Hexingchang Xujiahe Formation gas reservoir in the eastern slope area of western Sichuan.

[0065] As a preferred embodiment of the present invention, in step 3, taking four stabilities as the production allocation principle, if at least one parameter among the wellhead pressure, gas production, chloride ion, and water production of the gas well shows a sudden change after production adjustment, it is necessary to adjust back to the original working system.

[0066] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are:

[0067] In the technical solution of the present invention, by according to the geological characteristics and production laws of gas wells in the target area, combined with the goal of economic exploitation, calculating gas well parameters through research, dynamically tracking production laws, and formulating detailed tracking response measures in an organized manner, four-stable production of gas wells in the target area is achieved, greatly reducing the negative impacts such as "water invasion", tubing fracture, and rapid decline of gas well pressure caused by unreasonable production allocation, constructing a production management system comparable to the Xujiahe Formation gas reservoir in the eastern slope area of western Sichuan and having a fractured controlled-production tight sandstone reservoir with edge-bottom water, formulating the efficient production rate of gas wells for benefit, thereby improving the ultimate recovery rate of gas wells and increasing the recoverable reserves of the gas reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 is a flow chart of the reservoir stable production method of the present invention;

[0069] Figure 2 is the water body occurrence relationship of the reservoir of the present invention;

[0070] Figure 3It is the gas production curve of Well XS101 in Embodiment 2 of the present invention;

[0071] Figure 4 It is the binomial productivity equation diagram of Well XS101 in Embodiment 2 of the present invention;

[0072] Figure 5 It is the gas production curve of Well 3 in Embodiment 3 of the present invention;

[0073] Figure 6 It is the gas production curve of Well 4 in Embodiment 3 of the present invention;

[0074] Figure 7 It is the gas production curve of Well 5 in Embodiment 3 of the present invention; Detailed implementation manners

[0075] The present invention will be described in detail below with reference to the accompanying drawings.

[0076] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0077] Combined with the gas reservoir geological characteristics of the target area and the data of the preliminary test production wells, the present invention determines that the Hexingchang Xujiahe Formation gas reservoir in the eastern slope area of Western Sichuan has the production characteristics of high production, water production, and carbon dioxide corrosion, clarifies the important monitoring role of chloride ions in the stable production of this gas reservoir, establishes a reasonable production allocation system of "pressure maintenance, stable production, water control, and stable chloride ions" based on geological characteristics, and specifically proposes a production system of "reasonable production allocation, chloride ion monitoring, anti-corrosion, and scale inhibition". The present invention is applicable to the production management of the Xujiahe Formation gas reservoir in Western Sichuan.

[0078] Embodiment 1

[0079] This embodiment provides a method for stable production of a fractured production-controlled tight sandstone reservoir with edge and bottom water, specifically including the following steps:

[0080] Step 1: Collect geological exploration data of the target area, obtain the geological characteristics of the Xujiahe Formation gas reservoir in the target area, and obtain the gas reservoir production dynamic characteristics of the target area according to the production data of the test production wells, and initially establish a stable production allocation plan for production parameters;

[0081] Step 2: According to the stable production allocation plan for production parameters described in Step 1, calculate and analyze the changes in production parameters of single wells in the target area under different production allocation plans; and perform a secondary stable production allocation plan for production parameters;

[0082] In the technical solution of this embodiment, Figure 1 The flow chart of the reservoir stable production method of the present invention is shown;

[0083] Specifically, according to existing research: The Xujiahe Formation Member 2 gas reservoir in the eastern slope area of western Sichuan has a large burial depth. Due to the influence of tectonic movements with multiple phases and different principal stress directions, faults are generally well-developed. Due to the complex structure, the basic elements of each fault are different, and the degree of fracture development varies, so the production effects are different. The Hexingchang Xujiahe Formation gas reservoir in the eastern slope area of western Sichuan is close to the fracture zone where fractures are developed and is a high-production area of the Xujiahe Formation Member 2 gas reservoir in the eastern slope area of western Sichuan.

[0084] According to previous data, natural fractures are high-quality natural gas transmission channels. The Xujiahe Formation Member 2 gas reservoir is mainly a tight sandstone gas reservoir dominated by siltstone. The surrounding siltstone has good wettability, making it conducive to the accumulation of water at the fractures. Once the gas-water distribution near the production horizon changes suddenly, the fractures are easily occupied by formation water, blocking the flow of natural gas and causing the "water lock" phenomenon. However, the gas-water distribution of each level of fault is different, resulting in a complex gas-water distribution in the Hexingchang Xujiahe Formation gas reservoir in the eastern slope area of western Sichuan, without a unified gas-water interface. Formation water with a large amount of water in the deep part is easily infiltrated into the fractures, triggering "violent water flooding". Therefore, in order to avoid the influence of "water invasion", more production data need to be obtained through pilot production, the production laws of gas wells need to be mastered, and reasonable and effective management methods need to be formulated to stabilize the efficient production of gas wells in the Hexingchang Xujiahe Formation gas reservoir in the eastern slope area of western Sichuan.

[0085] Specifically, in step 2, the specific calculation and analysis process includes the following steps:

[0086] Step 21: Based on the formation, structure, sedimentary microfacies, and reservoir characteristics of the fracture system where the Xujiahe Formation gas well is located, taking permeability as the first quantitative evaluation factor, establish a reservoir classification and evaluation standard, which is divided into three grades: good, better, and medium.

[0087] Step 22: Determine the fluid properties such as natural gas and water body in different fracture systems. According to the change of the chemical properties of the water body in a single well and its water body distribution characteristics, combined with the research results of gas reservoir accumulation and evolution, conduct research on the occurrence status of the water body, and divide the occurrence status of the gas reservoir water body in the target area into four categories: gaseous water, bound water, capillary water, and free water.

[0088] Step 23: Calculate the dynamic reserves according to the formation pressure, seepage characteristics, etc. of different fracture systems, carry out gas production allocation for gas wells, and use the indicators that can directly reflect the production status of gas wells as the monitoring indicators for reasonable gas production allocation and stable production of gas wells; in step 23, the indicators include wellhead pressure, gas production, water production, and water body properties.

[0089] Step 24: Conduct minute-level tracking of the indicators determined in step 23 at the wellhead, and monitor the change of water body properties through daily artificial chloride titration, total iron measurement, etc.; in step 24, the tracking equipment includes installing a digital pressure gauge at the wellhead, installing a flowmeter in the gas production process, and installing a digital liquid level gauge in the liquid storage tank.

[0090] Step 25: Based on the dynamic and static characteristics of the similar fracture system, clarify the reasonable range of changes in stable production parameters and the types of gas well production anomalies corresponding to different parameter combinations, and adjust the development strategy in a timely manner.

[0091] More specifically, in the above-mentioned Step 2, the types of gas well production anomalies include the following five categories:

[0092] Water invasion, liquid loading in the wellbore, tubing corrosion, blockage at the wellhead throttle or in the gas transmission pipeline, and abnormality in the metering system. In the above-mentioned Step 2, for each specific type of gas well production anomaly, the adjustment strategies are as follows:

[0093] a. When water invasion occurs, adjust by plugging water in the formation.

[0094] b. When liquid loading in the wellbore occurs, adjust by injecting foam drainage aid into the wellbore.

[0095] c. When tubing corrosion occurs, adjust by injecting corrosion inhibitor into the wellbore.

[0096] d. When blockage occurs at the wellhead throttle or in the gas transmission pipeline, adjust by injecting antifreeze into the process.

[0097] e. When an abnormality occurs in the metering system, the adjustment countermeasure is: clean the orifice plate inspection hole, purge the pressure guiding pipe, or calibrate and replace the transmitter.

[0098] Furthermore, in the above-mentioned Step 2, different types of gas well production anomalies correspond to different parameter change characteristics. For the water invasion type, the corresponding parameter changes are: wellhead pressure decreases, gas production decreases, water production increases, and chloride ion value increases;

[0099] For the anomaly of liquid loading in the wellbore type, the corresponding parameter changes are: wellhead pressure decreases, gas production decreases, water production decreases, and chloride ion value remains unchanged;

[0100] For the anomaly of tubing corrosion type, the corresponding parameter changes are: wellhead pressure remains unchanged, gas production remains unchanged, water production remains unchanged, and iron ion content increases;

[0101] For the abnormal situation of blockage at the wellhead throttle or in the gas transmission pipeline, the corresponding parameter changes are: wellhead pressure rises, gas production decreases, water production decreases, and chloride ion value remains unchanged;

[0102] For the situation of abnormality in the metering system, the corresponding parameter changes are: wellhead pressure remains unchanged, gas production suddenly changes, water production remains unchanged, and chloride ion value remains unchanged.

[0103] Specifically, the above different anomalies and corresponding countermeasures are sorted out as shown in Table 1 below:

[0104] Table 1 is a comparison table of abnormalities and countermeasures

[0105]

[0106] By adjusting the working system of the test production well and combining with the gas production curve, gas component analysis and testing are carried out to clarify that this gas reservoir belongs to a dry gas reservoir, with a relatively high carbon dioxide content and no hydrogen sulfide. Figure 2 It shows the water occurrence relationship of the Xujiahe Formation gas reservoir in Xujiahe Formation, which is divided into four categories: gaseous water, bound water, capillary water, and free water. Their water volume and salinity increase successively from top to bottom. According to the analysis of water chemical components, it shows that the water chemical characteristics of the Xujiahe Formation gas reservoir in Hexingchang area, eastern Sichuan slope, are stable. The change of formation water chemical components is a precursor of violent water flooding. The chloride ion representing the formation water chemical characteristics is the key parameter for monitoring the change of formation water properties. The sudden change of its value means that the gas well has "water invasion". Therefore, during the production process of gas wells in the Xujiahe Formation gas reservoir in Hexingchang area, eastern Sichuan slope, the wellhead pressure, gas production, chloride ion, and water production are taken as the key attention objects, and the four stable production parameters of "pressure maintenance, stable production, water control, and stable chloride ion" are used as the reasonable production allocation principle.

[0107] Step 3: According to the fine-tuned stable production allocation plan in Step 2, regularly track the production dynamics of gas wells in the target area to achieve stable production of gas wells in the target area.

[0108] Specifically, during the test production process, after adjusting the choke size of the test production well, observe that the chloride ion of the formation water of the gas well is similar to that before the adjustment, the water production changes little, the gas production meets the expectation, and the wellhead pressure meets the expectation. Moreover, as time goes by, these four production parameters fluctuate normally, then the gas well is stable in this working system. Based on the four stable principles, the reasonable working system of the gas well can be determined to achieve stable liquid-carrying production.

[0109] Example 2

[0110] Specifically, taking the XS101 well as an example Figure 3It is the gas production curve of this well. After the well was opened for liquid drainage in the initial production stage, during the first stage, a trial production was carried out through a choke with a diameter of 4.8 mm. During this stage, the daily gas production of the gas well was about 15×10⁴ m³ / d, the daily water production was about 6 m³ / d, the casing pressure was about 45 MPa, the chloride ion content of the formation water was 23000 - 25000 ppm, and the production was stable; Stage 2: The choke was adjusted up to 5.5 mm. The daily gas production increased to 18.5×10⁴ m³ / d, the daily water production was about 6 m³ / d, the casing pressure was about 43 MPa, and the chloride ion content was 21000 - 25000 ppm. The gas well production remained stable while the production increased; Stage 3: The choke was adjusted two levels larger. The daily gas production increased to about 24×10⁴ m³ / d, the water production doubled, the casing pressure dropped to 40 MPa, and the chloride ion content also suddenly increased to 31000 ppm. Combining the four stability principles, at this time, the gas well showed the characteristics of early water invasion. The choke size was adjusted back to that of the second stage, and finally the reasonable working system of this well was determined. Then, using the production characteristic data that met the four stability principles during the trial production stage, through Figure 4 the binomial deliverability equation shown, the absolute open flow potential of this well was estimated to further reflect the actual production capacity of this well.

[0111] Example 3

[0112] Specifically, taking Well 3 as an example, Figure 5 is the gas production curve of Well 3. When this well was put into production initially, the gas production was 10×10 4 m 3 / d, and the water production was 0.7 m 3 / d. In the first 2 years of open well production, the change curves of the wellhead pressure, gas production, and water production were relatively stable, maintaining stable production. However, subsequently, the water production of this well increased sharply (0.7↑58.2 m 3 / d), the gas production decreased to 0.52×10 4 m 3 / d, the wellhead casing pressure decreased, and a large amount of formation water invaded the gas well borehole. This not only caused the casing pressure difference at the wellhead to continuously increase (0.9↑3.8 MPa), the gas production continued to decrease, but also aggravated the corrosion of the wellbore. This well was later shut in due to tubing fracture and gas well flooding.

[0113] Example 4

[0114] With the development of technology, chloride ion monitoring has become an effective means to predict gas well water invasion. Taking Well 4 as an example, Figure 6This is the comprehensive gas production curve of the well. At the wellhead pressure and daily gas production curves of the well in Stage 1 were relatively stable, the daily water production showed an upward trend, and the chloride ion value fluctuated significantly between 30,000 - 50,000 mg / L, suspected of formation water invasion. After adjusting the production regime, it entered Stage 2. In the early stage, the well was able to maintain a stable production state of the four parameters, and then the regular monitoring of the chloride ion value was cancelled; however, after the well was reopened for production in the middle stage, it could never recover to the gas production before shutting in. At the same time, the chloride ion value exceeded 60,000 mg / L and continued to rise, while the water production and wellhead pressure changed relatively stably. Until January 22, 2023, the wellhead pressure (34.9↓30.3 MPa) and gas production (21.9↓17.3×10 4 m 3 / d) dropped sharply, the water production increased sharply (35.5↑61.5 m 3 / d), and the chloride ion value also continued to rise, indicating that water invasion occurred in the well. In Stage 3, affected by water invasion, the water production of Well 2 increased to 158 m 3 / d, the gas production decreased to 5.5×10 4 m 3 / d, and the wellhead pressure dropped to 18.2 MPa. To prevent Well 2 from being flooded, water plugging measures were adopted to relieve water invasion, and the changes in the wellhead pressure, gas production, water production, and chloride ion value of the well were continuously monitored regularly. Their change curves were all stable, so the well could maintain stable production in Stage 4.

[0115] Example 5

[0116] Similarly, as Figure 7 shown, the wellhead pressure of Well 5 at the initial stage of production was 34.34 MPa, the gas production was 34×10 4 m 3 / d, the water production was 9.1 m 3 / d, and the chloride ion was 18,804 mg / L. In Period A, the wellhead pressure, gas production, and water production remained unchanged, and the chloride ion value increased significantly. Subsequently, the water production increased (9.1↑14.8 m 3 / d). After the choke was adjusted downwards several times, the chloride ion value gradually stabilized at 36,396 mg / L, the water production continued to increase, and at the same time, the gas production and wellhead pressure decreased. After adjusting the choke again, the wellhead pressure, gas production, and water production tended to be stable, while the chloride ion value continued to rise to 42,462 mg / L. At this time, the water production increased from 52.2 m 3 / d to 62.8 m 3 / d. Due to the well having carbon dioxide corrosion and bacterial corrosion, water invasion led to liquid accumulation in the wellbore and gas transmission pipeline, further exacerbating the corrosion phenomenon and causing pipeline leakage, making it difficult for the gas well to maintain long-term uninterrupted production. Therefore, it is also necessary to relieve corrosion by injecting corrosion inhibitors and bactericides. Currently, the chloride ion value and water production of the well remain unchanged, and the wellhead pressure and gas production are slowly decreasing.

[0117] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A stable production method applicable to fractured production-controlled tight sandstone reservoirs with edge and bottom water, characterized in that, it includes the following steps: Step 1: Collect geological exploration data of the target area, obtain the geological characteristics of the fractured production-controlled tight sandstone reservoir with edge and bottom water in the target area, and based on the production data of the test production wells, obtain the gas reservoir production dynamic characteristics of the target area, and initially establish a stable production parameter allocation plan for the proposed production wells; Step 2: According to the stable production parameter allocation plan described in Step 1, further calculate and analyze the changes in production parameters of individual wells in the target area under different allocation plans; and perform a secondary stable production parameter allocation plan; Step 3: According to the secondary stable production parameter allocation plan in Step 2, regularly track the production dynamics of the gas wells in the target area to achieve stable production of the gas wells in the target area.

2. The stable production method applicable to fractured production-controlled tight sandstone reservoirs with edge and bottom water according to claim 1, characterized in that, in the said Step 2, the specific calculation and analysis process includes the following steps: Step 21: Based on the formation, structure, sedimentary microfacies, and reservoir characteristics of the fracture system where the gas wells in the tight sandstone reservoir are located, taking permeability as the first quantitative evaluation factor, establish a reservoir classification and evaluation standard, which is divided into three grades: good, better, and medium; Step 22: Determine the fluid properties of natural gas and water bodies in different fracture systems. According to the changes in the chemical properties of the water body in individual wells and its water body distribution characteristics, combined with the research results of gas reservoir accumulation and evolution, carry out research on the occurrence status of the water body, and divide the occurrence state of the gas reservoir water body in the target area into four categories: gaseous water, bound water, capillary water, and free water; Step 23: Calculate the dynamic reserves according to the formation pressure, seepage characteristics, etc. of different fracture systems, allocate production to the gas wells, and use the indicators that can directly reflect the production status of the gas wells as the monitoring indicators for reasonable production allocation and stable production of the gas wells; Step 24: Track the indicators determined in Step 23 at the wellhead of the gas well, and monitor the changes in water body properties through daily artificial chloride titration and total iron measurement methods; Step 25: According to the dynamic and static characteristics of similar fracture systems, clarify the reasonable range of changes in stable production parameters, as well as the types of production anomalies corresponding to different parameter combinations, and adjust the development strategy.

3. The stable production method applicable to fractured production-controlled tight sandstone reservoirs with edge and bottom water according to claim 2, characterized in that, in Step 23, the said indicators include wellhead pressure, gas production, water production, and water body properties.

4. The stable production method applicable to fractured production-controlled tight sandstone reservoirs with edge and bottom water according to claim 2, characterized in that, in Step 24, the tracking equipment includes installing a digital pressure gauge at the wellhead, installing a flowmeter in the gas production process, and installing a digital liquid level gauge in the liquid storage tank.

5. The stable production method applicable to fractured production-controlled tight sandstone reservoirs with edge and bottom water according to claim 2, characterized in that, in the said Step 2, the types of production anomalies of gas wells include the following five categories: water invasion, wellbore liquid accumulation, tubing corrosion, blockage at the wellhead throttle or in the gas transmission pipeline, and abnormal metering system.

6. The stable production method for fractured production-controlled tight sandstone reservoirs with edge and bottom water according to claim 5, characterized in that, in step 2, for each specific type of abnormal gas well production, the adjustment strategy is as follows: a. When water invasion occurs, adjust by plugging the formation water; b. When wellbore liquid accumulation occurs, adjust by injecting foam drainage agent into the wellbore; c. When tubing corrosion occurs, adjust by injecting corrosion inhibitor into the wellbore; d. When the wellhead throttle or the gas transmission pipeline is blocked, adjust by injecting antifreeze agent into the process; e. When the metering system malfunctions, the adjustment countermeasure is: clean the orifice plate inspection hole, purge the pressure guiding pipe, or calibrate and replace the transmitter.

7. The stable production method for fractured production-controlled tight sandstone reservoirs with edge and bottom water according to claim 5, characterized in that, in step 2, different types of abnormal gas well production have different parameter change characteristics. For the water invasion type, the corresponding parameter changes are: the wellhead pressure decreases, the gas production rate decreases, the water production rate increases, and the chloride ion value increases; For the abnormal situation of wellbore liquid accumulation, the corresponding parameter changes are: the wellhead pressure decreases, the gas production rate decreases, the water production rate decreases, and the chloride ion value remains unchanged; For the abnormal situation of tubing corrosion, the corresponding parameter changes are: the wellhead pressure remains unchanged, the gas production rate remains unchanged, the water production rate remains unchanged, and the iron ion content increases; For the abnormal situation of blockage at the wellhead throttle or the gas transmission pipeline, the corresponding parameter changes are: the wellhead pressure rises, the gas production rate decreases, the water production rate decreases, and the chloride ion value remains unchanged; For the abnormal situation of the metering system malfunction, the corresponding parameter changes are: the wellhead pressure remains unchanged, the gas production rate suddenly changes, the water production rate remains unchanged, and the chloride ion value remains unchanged.

8. The stable production method for fractured production-controlled tight sandstone reservoirs with edge and bottom water according to claim 7, characterized in that, in step 3, if after adjustment, at least one of the parameters of the wellhead pressure, gas production rate, chloride ion, and water production rate of the gas well suddenly changes, it is necessary to adjust back to the original working system.

9. The stable production method for fractured production-controlled tight sandstone reservoirs with edge and bottom water according to any one of claims 1-9, characterized in that, in step 1, the test production well and the proposed production-allocated well need to be in the same fracture system and have similar geological and dynamic characteristics.

10. The stable production method for fractured production-controlled tight sandstone reservoirs with edge and bottom water according to claim 9, characterized in that, the stable production described in step 3 is a long-term changing process, and it is necessary to dynamically adjust the production parameters at different production stages of the gas well to obtain long-term stable production.

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