Shale gas full life cycle yield prediction method

Abstract

The invention discloses a shale gas full life cycle yield prediction method, and relates to the field of shale gas development. According to the shale gas full life cycle yield prediction method, the production stage of a shale gas well is divided into six stages of stable yield, continuous decreasing, intermittent production, pressurization decreasing, pressurization intermittent opening and fracturing effect receiving; in the stable production stage, the gas production rate is predicted by adopting a productivity coefficient method based on unstable linear flow, in the continuous decline stage, the gas production rate is predicted according to the ARPS decline model analogy partition decline rate, and in the intermittent production stage, the gas production rate is predicted by combining the ARPS decline model and the intermittent efficiency; in the pressurization decline stage, the gas production rate is predicted according to the gas well decline rate of the corresponding decline stage by adopting monthly production data; the gas production rate is predicted in combination with a decline model and the intermittent opening efficiency in the pressurizing intermittent opening stage; and predicting the gas production rate by using the effected ARPS model in the fracturing effected stage. According to the shale gas full life cycle yield prediction method, the corresponding yield prediction method is established according to the production rules of different development stages of the shale gas full life cycle, and the yield prediction efficiency and accuracy are improved.

Description

Technical Field

[0001] The present application relates to the field of shale gas development, and specifically to a method for predicting shale gas production throughout its life cycle. Background Art

[0002] The complexity of shale gas development makes conventional gas reservoir engineering theories and methods inapplicable. Domestic shale gas geological conditions and production methods differ from those found abroad. The high-pressure differential production methods employed abroad are not applicable to domestic production, while the fixed-rate production method employed in China cannot be adapted to foreign production forecasting methods. While empirical decline analysis is often used abroad to analyze production, this decline analysis method has limitations and is not suitable for the initial fixed-rate production methods used in domestic gas wells.

[0003] Currently, no unified shale gas well production prediction method has been established domestically or internationally. Existing production prediction methods are only applicable to a specific stage or production method and cannot predict gas well production throughout its multi-stage life cycle. Summary of the Invention

[0004] The purpose of this application is to provide a shale gas production prediction method for the entire life cycle, which establishes a corresponding production prediction method based on the production laws of different development stages of the shale gas life cycle, thereby improving the efficiency and accuracy of production prediction.

[0005] This application is implemented as follows:

[0006] This application provides a shale gas production prediction method for the entire life cycle, which includes the following steps:

[0007] S1. The production phase of shale gas wells in their entire life cycle is divided into three phases: self-flowing production, pressurized production, and fracturing effectiveness.

[0008] S2. The gas flow production stage is divided into a stable production stage, a continuous decline stage, and an intermittent production stage. In the stable production stage, the capacity coefficient method based on unstable linear flow is used to predict gas production. In the continuous decline stage, the gas production to the abandoned production is predicted based on the ARPS decline model and the partition decline rate. In the intermittent production stage, the gas production is predicted by combining the ARPS decline model and the intermittent efficiency.

[0009] S3. Divide the boost production phase into a boost decline phase and a boost intermittent phase; in the boost decline phase, use monthly production data to predict gas production based on the decline rate of the gas wells in the corresponding decline phase; in the boost intermittent phase, combine the decline model and intermittent efficiency to predict gas production;

[0010] S4. During the effective fracturing stage, the ARPS model is used to predict gas production.

[0011] In some optional implementation schemes, the productivity coefficient method based on unstable linear flow in step S2 refers to using the unstable linear flow equation to predict the cumulative production when the bottom hole flow pressure reaches the external transmission pressure according to the given production allocation of the gas well, that is, the cumulative production during the stable production period.

[0012] In some optional embodiments, the unsteady linear flow equation is a straight line with a slope of -1 / 2 as shown on a graph of normalized pressure and material balance time data for a shale gas well.

[0013] In some optional implementation schemes, in step S2, the gas production to the abandoned production is predicted based on the analogous partition decline rate of the ARPS decline model, and the production decline curve model is determined based on the shale gas production data, the time step of the production prediction and the abandoned production are set, and then the production prediction is performed based on this.

[0014] In some optional implementation schemes, the pressurized production stage in step S3 refers to the production stage in which the gas gathering station compressor intervenes to reduce the gas wellhead pressure.

[0015] In some optional implementation schemes, in step S3, for the wells with obvious decreasing patterns before and after the pressurization, the production data is normalized with pressurization production as the starting point, and a pressurization production incremental decrease model is established to predict the gas well production in the pressurization stage.

[0016] In some optional implementation schemes, in step S4, the effective fracturing stage starts from the obvious changes in gas well pressure and production after the effective fracturing, and the APRS decline analysis method is used to predict the corresponding production based on the post-effective model.

[0017] In some optional implementation schemes, shale gas wells are divided into self-flowing production, boosted production and fracturing production according to the production mode.

[0018] The beneficial effects of the present application are as follows: the shale gas production prediction method provided in the present application includes the following steps: dividing the production stages of a shale gas well throughout its life cycle into three stages: self-flowing production, boosted production and effective fracturing; dividing the self-flowing production stage into a stable production stage, a continuous decline stage and an intermittent production stage; in the stable production stage, the production capacity coefficient method based on unstable linear flow is used to predict the gas production; in the continuous decline stage, the gas production to the abandoned production is predicted by analogy with the partition decline rate of the ARPS decline model; in the intermittent production stage, the gas production is predicted in combination with the ARPS decline model and the intermittent efficiency; dividing the boosted production stage into a boosted decline stage and a boosted intermittent stage; in the boosted decline stage, monthly production data is used to predict the gas production according to the gas well decline rate of the corresponding decline stage; in the boosted intermittent stage, the gas production is predicted in combination with the decline model and the intermittent efficiency; and in the effective fracturing stage, the gas production is predicted using the effective ARPS model. The shale gas full life cycle production prediction method provided in this application establishes a corresponding production prediction method based on the production laws of different development stages of the shale gas full life cycle, effectively improving the efficiency and accuracy of production prediction, thereby guiding the preparation of shale gas development plans and on-site production allocation of shale gas wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 A schematic diagram of the process of predicting shale gas production throughout its life cycle provided in an embodiment of the present application;

[0021] Figure 2 This is a shale gas well production decline curve in the decline stage of the shale gas full life cycle production prediction method provided in the embodiment of the present application. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0023] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0024] The characteristics and performance of the shale gas full life cycle production prediction method of the present application are further described in detail below with reference to the examples.

[0025] like Figure 1 and Figure 2 As shown, the embodiment of the present application provides a shale gas full life cycle production prediction method, which includes the following steps:

[0026] S1. Based on the production mode of shale gas wells, carry out detailed division of the production stages of the entire life cycle, and divide the production stages of shale gas wells into three stages: self-flowing production, pressurized production and fracturing effect;

[0027] S2. The self-flowing production stage is divided into the stable production stage, the continuous decline stage and the intermittent production stage; in the stable production stage, the productivity coefficient method based on unstable linear flow is used to predict the gas production. The productivity coefficient method based on unstable linear flow refers to the use of the unstable linear flow equation to predict the cumulative production when the bottom hole pressure reaches the external transmission pressure according to the given production allocation of the gas well, which is the cumulative production in the stable production period. The unstable linear flow equation is the -1 / 2 slope straight line presented on the normalized pressure and material balance time data board of the shale gas well; in the continuous decline stage, the gas production to the abandoned production is predicted by analogy with the partition decline rate of the ARPS decline model. The gas production to the abandoned production is predicted by analogy with the partition decline rate of the ARPS decline model. The production decline curve model is determined according to the shale gas production data, and the time step and abandoned production of the production prediction are set, and then the production is predicted based on this; in the intermittent production stage, the gas production is predicted by combining the decline model and the intermittent efficiency;

[0028] S3. The pressurized production stage is divided into a pressurized production decline stage and a pressurized production intermittent stage. The pressurized production stage refers to the stage in which the compressor at the gas gathering station intervenes to reduce the wellhead pressure of the gas well. In the pressurized production decline stage, monthly production data is used to predict gas production based on the decline rate of the gas wells in the corresponding decline stage. In the pressurized production decline stage, for wells with obvious decline patterns before and after pressurization, pressurized production is used as the starting point, and production data is normalized. A pressurized production increment-decline model is established to predict gas well production in the pressurized production stage. In the pressurized production intermittent stage, the decline model and intermittent efficiency are combined to predict gas production.

[0029] S4. During the effective fracturing stage, the ARPS model after the effect is used to predict gas production. The effective fracturing stage is based on the significant changes in gas well pressure and production after the fracturing is effective. The APRS decline analysis method is used to predict the corresponding production based on the model after the effect.

[0030] The shale gas production prediction method provided in the embodiment of the present application establishes a stage-by-stage production prediction method based on the production laws of different development stages of the shale gas life cycle, effectively improving the efficiency and accuracy of production prediction, thereby guiding the preparation of shale gas development plans and on-site production allocation of shale gas wells. This method can accurately predict the production of gas wells at different stages, provide guidance for the timing of intervention of production-increasing measures such as boosted production, drainage gas production, and gas lift, and at the same time provide effective technical support for the monthly and annual production planning and recoverable reserves calibration of the block.

[0031] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. A shale gas production prediction method for the entire life cycle, characterized in that: It includes the following steps: S1. The production phase of shale gas wells in their entire life cycle is divided into three phases: self-flowing production, pressurized production, and fracturing effectiveness. S2. Dividing the self-flowing production stage into a stable production stage, a continuous decline stage, and an intermittent production stage; in the stable production stage, using a capacity coefficient method based on unstable linear flow to predict gas production; in the continuous decline stage, predicting gas production to abandoned production by analogy with the partition decline rate of the ARPS decline model; and in the intermittent production stage, combining the ARPS decline model and the intermittent efficiency to predict gas production; S3. Dividing the pressurized production phase into a pressurized decline phase and a pressurized intermittent phase; in the pressurized decline phase, using monthly production data to predict gas production based on the decline rate of the gas wells in the corresponding decline phase; and in the pressurized intermittent phase, combining the decline model and intermittent efficiency to predict gas production; S4. In the effective fracturing stage, the gas production is predicted using the effective ARPS model.

2. The shale gas full life cycle production prediction method according to claim 1, characterized in that: The productivity coefficient method based on unstable linear flow in step S2 refers to using the unstable linear flow equation to predict the cumulative production when the bottom hole pressure reaches the external transmission pressure according to the given production allocation of the gas well, that is, the cumulative production during the stable production period.

3. The shale gas full life cycle production prediction method according to claim 2, characterized in that: The unstable linear flow equation is a straight line with a slope of -1 / 2 that appears on the graph of the normalized pressure and material balance time data of the shale gas well.

4. The shale gas full life cycle production prediction method according to claim 1, characterized in that: The gas production to the abandoned production is predicted by analogy of the regional decline rate based on the ARPS decline model in step S2, which is to determine the production decline curve model based on the shale gas production data, set the time step of the production prediction and the abandoned production, and then perform the production prediction based on this.

5. The shale gas full life cycle production prediction method according to claim 1, characterized in that: The pressurized production stage in step S3 refers to the stage in which the gas gathering station compressor intervenes in production to reduce the gas wellhead pressure.

6. The shale gas production prediction method for the entire life cycle according to claim 1, characterized in that: In step S3, for the wells with obvious decreasing regularity before and after the pressurization, the production data is normalized with the pressurization production as the starting point, and a pressurization production incremental decreasing model is established to predict the gas well production in the pressurization stage.

7. The shale gas production prediction method for the entire life cycle according to claim 1, characterized in that: In step S4, the fracturing effect stage starts from the obvious changes in gas well pressure and production after the fracturing effect. The APRS decline analysis method is used to predict the corresponding production based on the post-effect model.

8. The shale gas full life cycle production prediction method according to claim 1, characterized in that: Shale gas wells are divided into self-flowing production, boosted production and fracturing production according to the production method.

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