Method for regulating and controlling formation pressure in offshore oilfield reinjection process based on environmental protection collaboration

Abstract

The invention discloses a method for regulating and controlling formation pressure in an offshore oilfield reinjection process based on environmental protection synergy, which relates to the technical field of oilfield production water reinjection, and comprises the following steps: collecting the reinjection displacement, reinjection pressure and operation time of a throttle valve, a Christmas tree channel and a reinjection fluid under the working condition of conveying to a formation along a water injection string; unified checking and working condition correlation analysis are carried out, and a reinjection basic operation parameter set is generated; and performing throttling valve and Christmas tree internal flow characteristic analysis on the reinjection basic operation parameter set to obtain equivalent throttling characteristic parameters, and correcting wellhead injection pressure according to the equivalent throttling characteristic parameters to obtain effective injection pressure. According to the method, a unified and continuous pressure correction basis is provided for determining the safety constraint boundary and screening the optimal combination of the reinjection pressure and the reinjection displacement, so that reinjection regulation and control are unified among efficiency, safety and stability.

Description

Technical Field

[0001] This invention relates to the field of oilfield production water reinjection technology, and in particular to a method for regulating formation pressure during offshore oilfield reinjection based on environmental protection collaboration. Background Technology

[0002] As offshore oilfield development enters its mid-to-late stages, reinjection technology has become a crucial technical approach for maintaining formation pressure, enhancing oil recovery, and achieving injection-production balance. Currently, the water treatment capacity of some offshore production facilities is saturated. Injecting treated production water back into designated formations on a large scale fundamentally solves the problem of insufficient wastewater treatment capacity. This removes constraints on fluid extraction and provides critical infrastructure support for high and stable production in oilfield clusters. Existing offshore oilfield reinjection operations typically involve transporting and regulating the reinjection fluid through throttle valves, Christmas trees, and water injection tubing, and monitoring the reinjection status based on wellhead pressure and reinjection flow rate parameters. With the increasing scale of reinjection and the promotion of non-flowback operation modes, the reinjection process is gradually exhibiting characteristics of high flow rate, long cycle, and strong coupling, placing higher demands on the accuracy of pressure control and formation response understanding during the reinjection process.

[0003] However, reinjection pressure control largely relies on static design parameters and local monitoring results, making it difficult to fully reflect the flow and pressure states of throttle valves, Christmas trees, water injection tubing, and sand control tubing during continuous reinjection. Especially under non-flowback conditions, the dynamic correlation between reinjection pressure changes and formation pressure response remains unclear, resulting in a lack of unified constraints on reinjection pressure regulation and easily creating a conflict between ensuring formation safety and reinjection efficiency. Therefore, how to achieve coordinated optimization of reinjection pressure and reinjection discharge under the combined effects of multi-node flow constraints and formation dynamic response has become an urgent problem to be solved in current offshore oilfield reinjection technology. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a method for regulating formation pressure during offshore oilfield reinjection based on environmental protection collaboration, which solves the problem of the lack of a unified and collaborative control basis between the dynamic changes of reinjection pressure and the formation pressure response and multi-node pressure constraints during the reinjection process without backflow.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] This invention provides a method for formation pressure control during offshore oilfield reinjection based on environmental protection collaboration. The method includes: collecting data on reinjection flow rate, reinjection pressure, and operating time under conditions where the reinjection fluid is transported to the formation via a throttle valve, Christmas tree channel, and water injection string; performing unified verification and condition correlation analysis to generate a basic set of reinjection operating parameters; analyzing the internal flow characteristics of the throttle valve and Christmas tree within the basic reinjection operating parameter set to obtain equivalent throttle characteristic parameters; correcting the wellhead injection pressure based on these equivalent throttle characteristic parameters to obtain the effective injection pressure; and performing dynamic response analysis of formation pressure based on the effective injection pressure to determine and identify the formation pressure change trend. Abnormal pressure rise characteristics are identified, and pressure response results are obtained. Based on the pressure response results, pressure regulation is performed on the reinjection pressure under the current reinjection conditions without backflow, resulting in the reinjection pressure state. Under the reinjection pressure state, the pressure response results are verified against the pressure bearing states of the throttle valve, Christmas tree, and water injection tubing during the reinjection process to obtain safety constraint boundaries. These safety constraint boundaries are then matched with the preset formation allowable pressure range to obtain the optimal combination of reinjection pressure and reinjection flow rate. Continuous reinjection is performed on the optimal combination of reinjection pressure and reinjection flow rate to obtain a new reinjection pressure. The new reinjection pressure is compared with the pressure response results to generate a pressure regulation parameter set.

[0008] As a preferred embodiment of the method for formation pressure control during offshore oilfield reinjection based on environmental protection synergy described in this invention, the steps for generating the basic operating parameter set for reinjection are as follows:

[0009] Perform unified time alignment and consistency verification on reinjection displacement, reinjection pressure, and running time to generate valid reinjection operation data;

[0010] The effective reinjection operation data is stabilized to obtain stable reinjection pressure data and stable reinjection discharge data;

[0011] Based on stable reinjection pressure data and stable reinjection discharge data, the reinjection pressure change rate and reinjection discharge stability parameters are calculated, and the reinjection pressure change rate and reinjection discharge stability parameters are correlated with the running time to obtain the operating condition characteristic parameters.

[0012] The stable reinjection pressure data, stable reinjection displacement data, operating time, and operating condition characteristic parameters are uniformly packaged to generate a set of basic reinjection operating parameters.

[0013] As a preferred embodiment of the method for formation pressure control during offshore oilfield reinjection based on environmental protection synergy described in this invention, the steps for obtaining the equivalent throttling characteristic parameters are as follows:

[0014] Based on the basic operating parameter set of reinjection, the reinjection conditions of the throttle valve and the wellhead are digitally twinned and instantiated to form the internal flow conditions of the throttle valve and the wellhead.

[0015] Under the constraints of the flow conditions inside the throttle valve and the tree, operator mapping reasoning is performed on the flow regions inside the throttle valve and the tree to obtain the pressure and velocity changes in each flow region.

[0016] Physical consistency correction is performed on the pressure and velocity changes in each flow region, and the rotation-dominant flow characteristics of the throttling part of the throttling valve, the tree angle, and the valve cavity region are identified simultaneously.

[0017] By correlating the rotation-dominant flow characteristics with the local pressure variation characteristics inside the wellhead over time and unifying the scale, equivalent throttling characteristic parameters are obtained.

[0018] As a preferred embodiment of the method for formation pressure control during offshore oilfield reinjection based on environmental protection synergy described in this invention, the steps for obtaining the effective injection pressure are as follows:

[0019] By correlating the wellhead injection pressure with the equivalent throttling characteristic parameters in the basic reinjection operating parameter set over time, a throttling correction relationship is established.

[0020] Based on the throttling correction relationship, the changes in wellhead injection pressure during the reinjection process are corrected to form the wellhead pressure evolution state;

[0021] By using the wellhead pressure evolution state as the basis for correction, the wellhead injection pressure is uniformly corrected to obtain the effective injection pressure.

[0022] As a preferred embodiment of the method for formation pressure control during offshore oilfield reinjection based on environmental protection synergy described in this invention, the steps for obtaining the pressure response results are as follows:

[0023] The process of effective injection pressure changing over time is organized and serialized to construct an injection pressure change sequence.

[0024] Based on the injection pressure change sequence, dynamic response analysis is performed on the formation pressure change over time to obtain pressure response results.

[0025] As a preferred embodiment of the method for formation pressure control during offshore oilfield reinjection based on environmental protection synergy described in this invention, the steps for obtaining the reinjection pressure state are as follows:

[0026] Based on the pressure response results, determine the range of pressure variations that the formation can withstand under the current reinjection conditions;

[0027] Under the constraint of pressure variation range, the control and planning of the reinjection pressure variation process under the condition of no backflow is carried out to obtain the reinjection pressure variation process;

[0028] The reinjection pressure is uniformly regulated according to the change process of the reinjection pressure to form a reinjection pressure state.

[0029] As a preferred embodiment of the method for formation pressure control during offshore oilfield reinjection based on environmental protection synergy described in this invention, the steps for obtaining the safety constraint boundary are as follows:

[0030] Using the reinjection pressure state as a unified operating condition basis, a safety assessment is conducted on the formation pressure response and formation pressure change state to form a formation-side safety assessment result.

[0031] The pressure-bearing status of the throttle valve, the wellhead, and the water injection tubing is checked, and the pressure loss status of the sand control tubing during the reinjection process is estimated to form the equipment-side safety assessment results.

[0032] By unifying and correlating the results of the formation-side safety assessment with the results of the equipment-side safety assessment, we can identify the synergistic constraint relationship between formation safety requirements and equipment bearing capacity.

[0033] Based on the collaborative constraint relationship, the allowable pressure range that simultaneously satisfies the safety assessment results on the formation side and the equipment side is determined, thus obtaining the safety constraint boundary.

[0034] As a preferred embodiment of the method for formation pressure control during offshore oilfield reinjection based on environmental protection synergy described in this invention, the steps for obtaining the optimal combination of reinjection pressure and reinjection displacement are as follows:

[0035] Align the safety constraint boundary with the preset formation allowable pressure range to determine the feasible pressure range that can be used for reinjection control under the current reinjection conditions.

[0036] Within the feasible pressure range, the reinjection pressure and corresponding reinjection discharge are screened and constrained to form a candidate combination range that meets the safety conditions;

[0037] The optimal combination of reinjection pressure and reinjection displacement is obtained by selecting the combination of reinjection pressure and reinjection displacement from the candidate combination range that can achieve the best reinjection capacity without exceeding the feasible pressure range.

[0038] As a preferred embodiment of the method for controlling formation pressure during offshore oilfield reinjection based on environmental protection synergy described in this invention, the steps for obtaining the new reinjection pressure are as follows:

[0039] The optimal combination of reinjection pressure and reinjection displacement is set as the control benchmark for the current reinjection operating condition. Under the constraint of the control benchmark, the reinjection process is continuously adjusted to form a stable reinjection operating state.

[0040] Under stable reinjection operation, the change process of reinjection pressure over time is continuously recorded to obtain the new reinjection pressure.

[0041] As a preferred embodiment of the method for formation pressure control during offshore oilfield reinjection based on environmental protection synergy described in this invention, the steps for generating the pressure control parameter set are as follows:

[0042] The new reinjection pressure is aligned with the pressure response results of the corresponding time period to form a pressure alignment sequence.

[0043] Based on the pressure alignment sequence, the difference between the new reinjection pressure and the pressure response result is quantitatively analyzed to form pressure deviation characteristics;

[0044] Based on the pressure deviation characteristics, the reinjection pressure level under stable reinjection operation is characterized and summarized to form a pressure control parameter set.

[0045] The beneficial effects of this invention are as follows: By characterizing the internal flow characteristics of the throttle valve and the Christmas tree and extracting equivalent throttle characteristic parameters, the wellhead injection pressure can be specifically corrected during reinjection, obtaining an effective injection pressure that better reflects the actual reinjection conditions. This allows the characterization of reinjection pressure to go beyond surface monitoring values ​​and reflect the influence of the internal flow state of the throttle valve and the Christmas tree on pressure transmission, providing a more reliable basis for identifying the dynamic response of formation pressure. Furthermore, reinjection pressure regulation closely follows the actual pressure changes in the formation, effectively supporting pressure regulation decisions under non-flowback conditions and preventing the accumulation of mismatches between reinjection pressure and formation response during operation. Simultaneously, it provides a unified and continuous pressure correction basis for determining safety constraint boundaries and selecting the optimal combination of reinjection pressure and flow rate, achieving a balance between efficiency, safety, and stability in reinjection regulation. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a flowchart of a method for regulating formation pressure during offshore oilfield reinjection based on environmental protection collaboration.

[0048] Figure 2 A flowchart for generating the basic runtime parameter set for back injection.

[0049] Figure 3 A flowchart for obtaining safety constraint boundaries.

[0050] Figure 4 A flowchart for generating equivalent throttling characteristic parameters. Detailed Implementation

[0051] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0052] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0053] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0054] Reference Figures 1-4 This is one embodiment of the present invention, which provides a method for regulating formation pressure during offshore oilfield reinjection based on environmental protection synergy, comprising the following steps:

[0055] S1. Collect the reinjection discharge rate, reinjection pressure, and operating time under the operating conditions of the throttle valve, the tree channel, and the reinjection fluid being transported to the formation along the water injection string. Perform unified verification and operating condition correlation analysis to generate a set of basic reinjection operating parameters.

[0056] S1.1: Perform unified time alignment and consistency verification on reinjection displacement, reinjection pressure and running time to generate valid reinjection operation data;

[0057] Specifically, the reinjection volume, reinjection pressure, and operating time are organized according to a unified time identifier, so that the reinjection volume and reinjection pressure form a one-to-one correspondence in the operating time dimension. According to the operating time sequence, the synchronization and continuity of the reinjection volume change process and the reinjection pressure change process in the corresponding operating time period are compared and verified. It is checked whether the reinjection volume change process and the reinjection pressure change process maintain a synchronous continuity in the corresponding operating time period, and segments with missing records and abrupt changes in the operating time are removed. The verified reinjection volume, reinjection pressure, and corresponding operating time are then integrated and correlated with the operating conditions to generate valid reinjection operating data.

[0058] S1.2: The effective reinjection operation data is stabilized to obtain stable reinjection pressure data and stable reinjection discharge data;

[0059] Specifically, the effective reinjection operation data is continuously organized according to the operation time sequence, so that the reinjection pressure and reinjection discharge are continuously connected on a unified operation time axis. The high-frequency fluctuations in the reinjection process are compressed in time continuity, so that the changes in reinjection pressure and reinjection discharge are smooth and continuous in the operation time, and stable reinjection pressure data and stable reinjection discharge data that reflect the characteristics of stable reinjection conditions are obtained.

[0060] S1.3: Based on the stable reinjection pressure data and stable reinjection discharge data, calculate the reinjection pressure change rate and reinjection discharge stability parameters, and perform correlation analysis between the reinjection pressure change rate and reinjection discharge stability parameters and the running time to obtain the operating condition characteristic parameters;

[0061] Specifically, based on stable reinjection pressure data and stable reinjection discharge data, the reinjection pressure change rate and reinjection discharge stability parameters are calculated. The reinjection pressure change rate and reinjection discharge stability parameters are correlated and compared according to the operating time sequence and the operating conditions are merged. In this way, the differences in operating conditions corresponding to the degree of reinjection pressure change and the stability level of reinjection discharge are clarified in different operating time periods, and the operating condition characteristic parameters are obtained.

[0062] The expressions for calculating the reinjection pressure change rate and the reinjection displacement stability parameters are as follows:

[0063] ;

[0064] The expression for calculating the reinjection displacement stability parameter is:

[0065] ;

[0066] ;

[0067] in, Indicates the first The rate of change of reinjection pressure at each sampling time is expressed in MPa / s. This indicates that the steady-state reinjection pressure data is in the first... Stable reinjection pressure data at each sampling time, in MPa; This indicates that the steady-state reinjection pressure data is in the first... Stable reinjection pressure data at each sampling time, in MPa; Indicates the first The running time at each sampling moment is expressed in seconds. Indicates the first The running time at each sampling moment is expressed in seconds. This represents the sample sequence number index during runtime; This represents the parameter indicating the stability of the reinjection displacement. This indicates the total number of sampling points included within the selected continuous running time period; This represents the index of the sampling point within the selected continuous running time period; Indicates the first time in a continuous running period Stable reinjection discharge data corresponding to each sampling point; This represents the average level of stable reinjection discharge data within the selected continuous operating time period.

[0068] S1.4: Unify and encapsulate the stable reinjection pressure data, stable reinjection displacement data, operating time and operating condition characteristic parameters to generate a set of basic reinjection operating parameters.

[0069] Specifically, the stable reinjection pressure data and stable reinjection displacement data are organized according to the operating time sequence to form a stable correspondence between them in the operating time dimension. The operating condition characteristic parameters corresponding to each operating time period are synchronously collected with the stable reinjection pressure data and stable reinjection displacement data, and then uniformly compiled and organized according to the operating time sequence. This ensures that the operating time, stable reinjection pressure data, stable reinjection displacement data, and operating condition characteristic parameters are consistently arranged in the same record structure, generating a set of basic reinjection operating parameters.

[0070] It should be noted that the stable reinjection pressure data refers to the stable pressure state formed by the wellhead injection pressure over the operating time dimension, which is used to reflect the actual driving pressure formed before the injected fluid enters the wellbore.

[0071] S2. Analyze the internal flow characteristics of the throttling valve and the wellhead on the basic operating parameter set of the reinjection system to obtain the equivalent throttling characteristic parameters. Then, correct the wellhead injection pressure based on the equivalent throttling characteristic parameters to obtain the effective injection pressure.

[0072] S2.1: Based on the basic operating parameter set of reinjection, perform digital twin instantiation processing on the reinjection conditions of the throttle valve and the wellhead to form the internal flow conditions of the throttle valve and the wellhead.

[0073] Specifically, based on the basic operating parameter set of reinjection, the reinjection discharge and reinjection pressure corresponding to the operating time are mapped one by one according to the actual channel structure of the throttle valve and the wellhead. This allows the reinjection discharge and reinjection pressure to form a flow distribution relationship corresponding to the actual operating state in the throttle valve channel, the main channel and branch channel of the wellhead. The mapping results under different operating time periods are continuously spliced ​​together, so that the flow state of the throttle valve and the wellhead during the reinjection process forms a continuously changing working condition mapping with the operating time, forming the internal flow working condition state of the throttle valve and the wellhead.

[0074] S2.2: Under the constraints of the internal flow conditions of the throttle valve and the tree, perform operator mapping reasoning on the internal flow regions of the throttle valve and the tree to obtain the pressure and velocity changes of each flow region.

[0075] Specifically, under the constraints of the flow conditions inside the throttle valve and the Christmas tree, the flow path inside the throttle valve and the Christmas tree is divided into multiple flow regions. Based on the correspondence between the reinjection discharge and reinjection pressure in each flow region according to the basic reinjection operating parameters, the flow state is mapped to each flow region step by step along the flow path, so that the flow state formed in the previous flow region naturally extends to the next flow region. Thus, under the constraints of the continuous structure of the internal channels of the throttle valve and the Christmas tree, the pressure change and flow velocity change states corresponding to each flow region are gradually obtained.

[0076] S2.3: Perform physical consistency correction on the pressure and velocity changes in each flow region, and simultaneously identify the rotation-dominant flow characteristics of the throttling valve throttling point, the tree angle, and the valve cavity region.

[0077] Specifically, based on the pressure and velocity changes in each flow region, the connection between adjacent flow regions is uniformly checked to ensure that the pressure and velocity changes remain continuous and consistent along the flow paths inside the throttling valve and the tree. Local changes that do not conform to the connection are uniformly adjusted to match the pressure and velocity changes in each flow region with the spatial morphology of the throttling valve, the tree corner, and the valve cavity area. Based on the throttling valve and the marked corner and valve cavity areas inside the tree, the velocity change pattern in the turning position and cavity space is synchronously identified, thereby identifying the dominant rotational flow characteristics in the throttling valve, tree corner, and valve cavity areas.

[0078] S2.4: The rotationally dominant flow characteristics and the local pressure change characteristics inside the wellhead are correlated over time and scaled to obtain the equivalent throttling characteristic parameters.

[0079] Specifically, the rotating dominant flow characteristics are aligned with the local pressure change characteristics at corresponding locations inside the throttling valve and the wellhead according to the operating time sequence. This ensures that the rotating dominant flow characteristics correspond consistently with the local pressure changes in the time dimension. Furthermore, the rotating dominant flow characteristics and local pressure change characteristics under different operating time periods are uniformly merged to form a stable correspondence between the rotating dominant flow characteristics and local pressure change characteristics at the same scale level, thus forming an equivalent throttling characteristic parameter that can reflect the degree of throttling influence inside the wellhead.

[0080] S2.5: Establish a throttling correction relationship by correlating the wellhead injection pressure and equivalent throttling characteristic parameters in the reinjection basic operating parameter set over time;

[0081] Specifically, the wellhead injection pressure in the basic reinjection operating parameter set is organized according to the operating time sequence and mapped one-to-one with the equivalent throttling characteristic parameter under the same operating time identifier, so that the wellhead injection pressure and the corresponding equivalent throttling characteristic parameter are established in a stable correspondence within each operating time period. The correspondence between the changes in wellhead injection pressure and the changes in equivalent throttling characteristic parameter within different operating time periods is uniformly merged and organized to form a throttling correction relationship that can reflect the changes in wellhead injection pressure under the influence of throttling in different operating time periods.

[0082] S2.6: Based on the throttling correction relationship, correct the changes in wellhead injection pressure during the reinjection process to form the wellhead pressure evolution state;

[0083] Specifically, based on the throttling correction relationship, the changes in wellhead injection pressure at different operating times during the reinjection process are compared segment by segment to ensure that the wellhead injection pressure remains consistent with the throttling effect reflected by the throttling correction relationship within each operating time period. Wellhead injection pressures that deviate from the throttling correction relationship are then sequentially calibrated. The calibrated wellhead injection pressures are then continuously connected and uniformly organized according to operating time, so that the change process of wellhead injection pressure with operating time is uniformly standardized in terms of temporal continuity and change trend, forming a wellhead pressure evolution state.

[0084] S2.7: Using the wellhead pressure evolution state as the basis for correction, the wellhead injection pressure is uniformly corrected to obtain the effective injection pressure.

[0085] Specifically, the pressure change process of the wellhead injection pressure and the corresponding time period in the wellhead pressure evolution state is compared segment by segment according to the operation time sequence. The segments of change in the wellhead injection pressure that are inconsistent with the wellhead pressure evolution state are uniformly corrected so that the wellhead injection pressure is consistent with the wellhead pressure evolution state in terms of change amplitude and continuity. The corrected wellhead injection pressure is then reorganized according to the operation time to form an effective injection pressure that can truly reflect the actual injection conditions during the reinjection process.

[0086] S3. Based on the effective injection pressure, perform dynamic response analysis of formation pressure to determine the trend of formation pressure change and identify abnormal pressure rise characteristics, and obtain pressure response results.

[0087] S3.1: Organize and serialize the process of effective injection pressure changing over time to construct an injection pressure change sequence;

[0088] Specifically, the effective injection pressure is organized according to the corresponding operating time sequence, so that the effective injection pressure forms a continuous correspondence in the operating time dimension. The changes of the effective injection pressure in each operating time period are arranged sequentially. The sequential changes of the effective injection pressure are organized through a unified operating time identifier, so that the change process of the effective injection pressure with operating time has continuity and integrity, forming an injection pressure change sequence.

[0089] S3.2: Based on the injection pressure change sequence, perform dynamic response analysis on the formation pressure change over time to obtain pressure response results.

[0090] Specifically, the injected pressure change sequence is compared segment by segment with the corresponding operating time to ensure that the injected pressure change sequence is consistent with the formation stress process in the operating time dimension. According to the sequential changes of the injected pressure change sequence, the formation pressure change process over time is continuously mapped to obtain the changes of formation pressure in different operating time periods. In the process of change, the overall trend of formation pressure change over time and the abnormal pressure rise patterns that occur during operation are summarized to form a pressure response result that includes the dynamic response of formation pressure, the trend of formation pressure change, and the abnormal pressure rise patterns.

[0091] S4. Based on the pressure response results, perform pressure regulation treatment on the reinjection pressure under the current reinjection conditions without backflow to obtain the reinjection pressure status.

[0092] S4.1: Based on the pressure response results, determine the range of pressure variations that the formation can withstand under the current reinjection conditions;

[0093] Specifically, based on the dynamic response of formation pressure, the trend of formation pressure change, and the abnormal pressure rise pattern in the pressure response results, the overall trend and local fluctuation of formation pressure changes in different operating periods are compared and analyzed to clarify the range of formation pressure that remains stable under continuous reinjection conditions and does not trigger abnormal pressure rise patterns. This range is then taken as the range of pressure changes that the formation can continuously withstand under the current reinjection conditions.

[0094] S4.2: Under the constraint of pressure change range, the control and planning of the reinjection pressure change process under the condition of no backflow is carried out to obtain the reinjection pressure change process;

[0095] Specifically, under the constraint of pressure variation range, taking the premise that no medium backflow occurs under the current reinjection conditions as a prerequisite, the process of reinjection pressure variation with operating time is sequentially analyzed to ensure that the pressure rise, stabilization, and adjustment phases of reinjection pressure are all limited within the pressure variation range. Based on the risk characteristics reflected by the abnormal pressure rise pattern in the pressure response results, the sequence and magnitude of reinjection pressure variation are coordinated to ensure that the reinjection pressure maintains a continuous transition during operation without exceeding the pressure variation range, thus obtaining the reinjection pressure variation process.

[0096] S4.3: The reinjection pressure is uniformly regulated according to the process of reinjection pressure change to form a reinjection pressure state.

[0097] Specifically, based on the process of reinjection pressure change, the sequence and magnitude of reinjection pressure changes over time are uniformly regulated so that the reinjection pressure strictly corresponds to the operating state defined by the process of reinjection pressure change during the pressure increase, pressure stabilization and adjustment phases. During continuous reinjection, the rhythm of reinjection pressure change is kept consistent with the process of reinjection pressure change, so that the reinjection pressure remains in a stable and controllable operating state throughout the entire operating time range, thus forming a reinjection pressure state.

[0098] S5. Under the reinjection pressure condition, verify the pressure response results and the pressure bearing state of the throttle valve, production tree and water injection string during the reinjection process to obtain the safety constraint boundary. Match the safety constraint boundary with the preset formation allowable pressure range to obtain the optimal combination of reinjection pressure and reinjection discharge rate.

[0099] S5.1: Using the reinjection pressure state as a unified operating condition basis, conduct a safety assessment of the formation pressure response and formation pressure change state to form a formation-side safety assessment result;

[0100] Specifically, the reinjection pressure state is used as a unified operating condition. The operating time periods corresponding to the reinjection pressure state are aligned and organized with the formation pressure response, so that the formation pressure response forms a verifiable formation pressure change state under the constraint of the reinjection pressure state. The consistency between the formation pressure change state and the abnormal pressure rise pattern in the formation pressure response is checked to determine whether the formation pressure change state exceeds the preset formation allowable pressure range under the reinjection pressure state. When there is an exceedance, the corresponding operating time period is marked as a pressure risk section; when there is no exceedance, the corresponding operating time period is marked as a pressure safety section. The formation pressure safety sections and pressure risk sections of each operating time period are uniformly merged to form the formation-side safety assessment results.

[0101] It should be noted that the allowable formation pressure range is set based on the dynamic response of formation pressure, the trend of formation pressure change, and the constraints on formation integrity and long-term stability caused by abnormal pressure rise patterns. The specific setting steps include: under reinjection conditions, summarizing the changes in formation pressure over time according to the injection pressure change sequence, identifying pressure ranges where the formation can maintain stable pressure and without abnormal pressure rise patterns during continuous reinjection; comparing and screening pressure sections that have not experienced formation anomalies, have not significantly deteriorated seepage capacity, and have remained stable during the reinjection process in historical reinjection phases, selecting pressure ranges that maintain stable performance across multiple operating time periods as the allowable formation pressure range; the exemplary range is 6.36 MPa to 8.99 MPa. The allowable wellhead injection pressure range of 6.36 MPa to 6.74 MPa corresponds to the scenario of "two wells injecting water simultaneously, with a single well injection rate of 15,000 m³ / d". Under the reinjection condition of a single well injecting water at a rate of 30,000 m³ / d, the corresponding allowable wellhead injection pressure range is 8.61 MPa to 8.99 MPa. When the wellhead injection pressure is below 6.36 MPa, the dynamic response amplitude of the formation pressure is relatively small, and the pressure change during reinjection is difficult to form a continuous and stable response characteristic, and the reinjection discharge is prone to significant fluctuations over time. When the wellhead injection pressure is above 8.99 MPa, the abnormal pressure rise characteristics in the dynamic response of the formation pressure are significantly enhanced, the formation pressure change trend deviates from the stable zone, and the formation integrity risk accumulates with the increase of operating time.

[0102] S5.2: Verify the pressure-bearing status of the throttle valve, the wellhead, and the water injection tubing, and estimate the pressure loss status of the sand control tubing during the reinjection process to form the equipment-side safety assessment results.

[0103] Specifically, under the reinjection pressure condition, the reinjection pressure condition within the corresponding operating time period is aligned with the channel positions of the throttle valve, Christmas tree, and water injection tubing. This ensures that the reinjection pressure condition forms a verifiable pressure condition record at the actual pressure-bearing locations of the throttle valve, Christmas tree, and water injection tubing. The pressure condition record is then compared segment by segment with the preset equipment pressure tolerance range to determine whether the pressure levels of the throttle valve, Christmas tree, and water injection tubing are within the equipment pressure tolerance range for each operating time period. Combining the reinjection pressure condition at the end of the water injection tubing, the reinjection discharge rate, and the structural dimensions and layout information of the sand control tubing, the pressure loss of the reinjected fluid within the sand control tubing is estimated, resulting in the pressure loss state of the sand control tubing during the reinjection process. Finally, the pressure verification results of the throttle valve, Christmas tree, and water injection tubing are unified and merged with the pressure loss state of the sand control tubing to form the equipment-side safety assessment result.

[0104] It should be noted that the allowable pressure range of the equipment is set based on the balance between the actual pressure conditions of the throttle valve, Christmas tree, water injection tubing, and sand control tubing during the reinjection process under reinjection pressure and the structural load-bearing safety requirements. The specific setting steps include: during reinjection operation, combining the reinjection foundation operating parameter set and pressure response results, clarifying the changes in pressure levels caused by the reinjection pressure acting on the throttle valve, Christmas tree, water injection tubing, and sand control tubing at different operating time periods, and comparing this with the pressure conditions required for the equipment to maintain structural stability and load-bearing reliability under long-term reinjection conditions, selecting a pressure range that simultaneously satisfies reinjection continuity and structural safety as the allowable pressure range of the equipment; an example value range is provided. The pressure ranges from 6.36 MPa to 15.00 MPa. The lower limit of 6.36 MPa is taken from the lower boundary of the allowable wellhead injection pressure under the condition of simultaneous water injection in two wells. This is used to ensure that the choke valve, Christmas tree, water injection tubing, and sand control tubing have the basic differential pressure drive required for continuous reinjection. The upper limit of 15.00 MPa is taken from the injection pressure level of 15 MPa on the equipment platform side. This is used to limit the equipment side from entering abnormal sections. When the pressure level is lower than 6.36 MPa, the space for adjusting the reinjection discharge is limited and the stability decreases. When the pressure level is higher than 15.00 MPa, it is easy to cause aggravated erosion at the choke point, abnormal stress at the connection of the Christmas tree, and a decrease in the long-term load-bearing reliability of the water injection tubing and sand control tubing.

[0105] S5.3: Unify and align the formation-side safety assessment results with the equipment-side safety assessment results, and perform correlation analysis to identify the synergistic constraint relationship between formation safety requirements and equipment bearing capacity;

[0106] Specifically, the formation-side safety assessment results and equipment-side safety assessment results are aligned according to the operating time periods corresponding to the reinjection pressure states, ensuring a one-to-one correspondence between the formation pressure safety level and the pressure safety levels of the throttle valve, Christmas tree, water injection tubing, and sand control tubing during the reinjection process. The formation-side safety assessment results and equipment-side safety assessment results within the same operating time period are compared and verified to determine whether the formation safety requirements and equipment bearing capacity simultaneously meet the preset allowable formation pressure range and equipment pressure allowable range under different reinjection pressure states. When both are in the safe zone, it is marked as a synergistically satisfied zone; when either is in the risk zone, it is marked as a synergistically restricted zone. Synergistically satisfied zones and synergistically restricted zones are then uniformly merged to identify the synergistic constraint relationship between formation safety requirements and equipment bearing capacity.

[0107] S5.4: Based on the cooperative constraint relationship, determine the allowable pressure range that simultaneously satisfies the formation-side safety assessment results and the equipment-side safety assessment results, and obtain the safety constraint boundary.

[0108] Specifically, based on the collaborative constraint relationship, the reinjection pressure status of the sections marked as collaboratively satisfied within each operating time period is centrally organized, so that the reinjection pressure status that simultaneously satisfies the formation-side safety assessment results and the equipment-side safety assessment results forms a continuous and usable pressure section. The upper and lower boundaries of the pressure section in the operating time dimension are uniformly summarized to determine the pressure allowable range that does not exceed the preset formation allowable pressure range or the preset equipment pressure bearing allowable range under the current reinjection conditions, and the pressure allowable range is used as the safety constraint boundary.

[0109] It should be noted that the allowable pressure range is set based on the requirement that the formation-side safety assessment results and the equipment-side safety assessment results be met simultaneously according to the cooperative constraint relationship. The exemplary range is 6.36MPa to 8.99MPa. When the reinjection pressure is lower than 6.36MPa, the reinjection driving force is insufficient, the space for increasing the reinjection discharge is limited, and fluctuations in the reinjection process and a decrease in reinjection stability are likely to occur. When the reinjection pressure is higher than 8.99MPa, the reinjection pressure will exceed the controllable pressure range corresponding to the formation-side safety assessment results, and at the same time, the pressure bearing level of the throttle valve and the tubing will increase significantly, which can easily cause abnormal pressure rise characteristics and increase the safety risks in the reinjection process.

[0110] S5.5: Align the safety constraint boundary with the preset formation allowable pressure range to determine the feasible pressure range that can be used for reinjection control under the current reinjection conditions;

[0111] Specifically, the safety constraint boundary and the preset formation allowable pressure range are aligned according to the operating time period corresponding to the reinjection pressure state, so that the safety constraint boundary and the preset formation allowable pressure range form a pressure range that can be directly compared in the time dimension. Within each operating time period, pressure segments that fall into both the safety constraint boundary and the preset formation allowable pressure range are identified, and the pressure segments are continuously sorted and merged to determine the feasible pressure range.

[0112] S5.6: Within the feasible pressure range, the reinjection pressure and corresponding reinjection displacement are screened and constrained to form a candidate combination range that meets the safety conditions;

[0113] Specifically, within the feasible pressure range, the reinjection pressure and corresponding reinjection discharge are compared and organized according to the operating time period corresponding to the reinjection pressure state, so that each reinjection pressure level corresponds to a clear reinjection discharge change segment. The combination segment where the reinjection pressure and reinjection discharge are both within the feasible pressure range is marked, and the reinjection discharge segments that do not fall within the feasible pressure range or do not match the reinjection pressure state are excluded. The combination segment of reinjection pressure and reinjection discharge that simultaneously meets the feasible pressure range and has continuous availability under the current reinjection conditions is retained to form a candidate combination interval.

[0114] S5.7: Select the optimal combination of reinjection pressure and reinjection displacement from the candidate combination range that can achieve the best reinjection capacity without exceeding the feasible pressure range, and obtain the optimal combination of reinjection pressure and reinjection displacement.

[0115] Specifically, within the candidate combination range, each combination of reinjection pressure and reinjection displacement is compared sequentially according to the operating time period corresponding to the reinjection pressure state. Priority is given to selecting combination segments that continuously fall within the feasible pressure range throughout the entire operating time period and maintain a stable and continuous reinjection displacement level. When multiple combination segments meet the conditions, the reinjection displacement corresponding to each combination segment at the same reinjection pressure level is compared. The combination of reinjection pressure and reinjection displacement with a higher overall reinjection displacement level and a continuous and consistent operating process is selected as the optimal combination of reinjection pressure and reinjection displacement.

[0116] S6. Continuously reinject the optimal combination of reinjection pressure and reinjection displacement to obtain a new reinjection pressure. Compare the new reinjection pressure with the pressure response results to generate a pressure control parameter set.

[0117] S6.1: Set the optimal combination of reinjection pressure and reinjection displacement as the control benchmark for the current reinjection operating condition, and continuously adjust the reinjection process under the constraint of the control benchmark to form a stable reinjection operating state;

[0118] Specifically, the optimal combination of reinjection pressure and reinjection displacement is set as the control benchmark under the current reinjection conditions, and the control benchmark is aligned with the corresponding operating time period to ensure that the reinjection pressure and reinjection displacement have a unified reference standard during operation. Under the constraint of the control benchmark, the reinjection pressure and reinjection displacement are continuously coordinated in accordance with the change sequence corresponding to the optimal combination of reinjection pressure and reinjection displacement during the reinjection process. This ensures that the actual reinjection process gradually conforms to the control benchmark and maintains the continuity and consistency of the change process, thereby keeping the reinjection pressure and reinjection displacement stably within the range of the control benchmark throughout the entire operating time period, forming a stable reinjection operating state.

[0119] S6.2: Under stable reinjection operation, the change process of reinjection pressure over time is continuously recorded to obtain the new reinjection pressure.

[0120] Specifically, the reinjection pressure is aligned with the corresponding operating time, and the changes in reinjection pressure are continuously collected and sorted in sequence according to the operating time. This results in a continuous and complete time-corresponding record of the reinjection pressure within each operating time period, preserving the reinjection pressure status of each time period under stable reinjection operation, and obtaining a new reinjection pressure that can reflect the changes in reinjection pressure over time under stable reinjection operation.

[0121] S6.3: Align the new reinjection pressure with the pressure response results of the corresponding time period to form a pressure alignment sequence;

[0122] Specifically, under stable reinjection operation, the operating time period corresponding to the new reinjection pressure is aligned with the time markers of the formation pressure dynamic response, formation pressure change trend, and abnormal pressure rise pattern in the pressure response results. This ensures a one-to-one correspondence between the new reinjection pressure and the corresponding pressure response results within each operating time period. The correspondence is then arranged continuously according to the operating time sequence, and the new reinjection pressure and the pressure response results of the corresponding time period are uniformly organized into a pressure alignment sequence with temporal continuity.

[0123] S6.4: Based on the pressure alignment sequence, a quantitative analysis is performed on the difference between the new reinjection pressure and the pressure response result to form pressure deviation characteristics;

[0124] Specifically, based on the pressure alignment sequence, the dynamic response of formation pressure, the trend of formation pressure change, and the abnormal pressure rise pattern in the new reinjection pressure and the corresponding pressure response results are compared segment by segment according to the operating time sequence. The differences between the new reinjection pressure and the pressure response results in each operating time period are summarized and organized. The differences formed in each operating time period are uniformly collected in terms of time continuity and change trend, forming a pressure deviation feature that can reflect the degree of difference and change law between the new reinjection pressure and the pressure response results.

[0125] S6.5: Based on the pressure deviation characteristics, the reinjection pressure level under stable reinjection operation is characterized and summarized to form a pressure control parameter set.

[0126] Specifically, based on the pressure deviation characteristics, the operating time periods corresponding to the pressure deviation characteristics are aligned one-to-one with the reinjection pressure levels under stable reinjection operating conditions. The changes in the reinjection pressure levels relative to the pressure deviation characteristics within each operating time period are merged, so that reinjection pressure levels with similar pressure deviation characteristics form a clear correspondence in the operating time dimension. Furthermore, the reinjection pressure levels corresponding to different pressure deviation characteristics under stable reinjection operating conditions are uniformly summarized, thereby extracting a set of pressure control parameters that can reflect the reinjection pressure control needs and control direction.

[0127] In summary, this invention, by characterizing the internal flow characteristics of the throttling valve and the Christmas tree and extracting equivalent throttling characteristic parameters, enables targeted correction of the wellhead injection pressure during reinjection. This yields an effective injection pressure that better reflects the actual reinjection conditions, ensuring that the characterization of reinjection pressure is no longer limited to surface monitoring values ​​but reflects the influence of the internal flow state of the throttling valve and the Christmas tree on pressure transmission. This provides a more reliable basis for identifying the dynamic response of formation pressure. Furthermore, the reinjection pressure regulation closely follows the actual pressure changes in the formation, effectively supporting pressure regulation decisions under non-flowback conditions and preventing the accumulation of mismatches between the reinjection pressure and formation response during operation. Simultaneously, it provides a unified and continuous pressure correction basis for determining safety constraint boundaries and selecting the optimal combination of reinjection pressure and flow rate, achieving a balance between efficiency, safety, and stability in reinjection regulation.

[0128] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for regulating formation pressure during offshore oilfield reinjection based on environmental protection synergy, characterized in that: comprising, collecting the reinjection discharge capacity, the reinjection pressure and the running time of the choke valve, the Christmas tree channel and the reinjection fluid under the working condition of the reinjection fluid column to the formation, and performing unified checking and working condition correlation analysis to generate a reinjection basic operation parameter set; performing choke valve and Christmas tree internal flow characteristic analysis on the reinjection basic operation parameter set to obtain equivalent choke characteristic parameters, and correcting the wellhead injection pressure according to the equivalent choke characteristic parameters to obtain an effective injection pressure; based on the effective injection pressure, performing formation pressure dynamic response analysis to judge the formation pressure change trend and identify abnormal pressure rise characteristics, and obtaining a pressure response result; based on the pressure response result, performing pressure regulation processing on the reinjection pressure under the condition of no backflow discharge under the current reinjection working condition to obtain a reinjection pressure state; under the reinjection pressure state, checking the pressure response result and the pressure bearing state of the choke valve, the Christmas tree and the reinjection fluid column in the reinjection process to obtain a safety constraint boundary, matching the safety constraint boundary with a preset formation allowable pressure interval to obtain an optimal combination of reinjection pressure and reinjection discharge capacity; continuously reinjecting the optimal combination of reinjection pressure and reinjection discharge capacity to obtain a new reinjection pressure, comparing the new reinjection pressure with the pressure response result to generate a pressure regulation parameter set.

2. The method for regulating formation pressure during offshore oilfield injection based on environmental protection synergy according to claim 1, characterized in that: The generation of the reinjection basic operation parameter set includes the following steps, performing unified time alignment and consistency checking on the reinjection discharge capacity, the reinjection pressure and the running time to generate effective reinjection operation data; performing smoothing processing on the effective reinjection operation data to obtain smooth reinjection pressure data and smooth reinjection discharge capacity data; calculating the reinjection pressure change rate and the reinjection discharge capacity stability parameter according to the smooth reinjection pressure data and the smooth reinjection discharge capacity data, and performing correlation analysis on the reinjection pressure change rate and the reinjection discharge capacity stability parameter with the running time to obtain working condition characteristic parameters; unified packaging of the smooth reinjection pressure data, the smooth reinjection discharge capacity data, the running time and the working condition characteristic parameters to generate the reinjection basic operation parameter set.

3. The method for regulating formation pressure during offshore oilfield injection based on environmental protection synergy according to claim 2, characterized in that: The equivalent choke characteristic parameters are obtained by the following steps, based on the reinjection basic operation parameter set, performing digital twin instantiation processing on the reinjection working condition of the choke valve and the Christmas tree to form the internal flow working condition state of the choke valve and the Christmas tree; under the constraint of the internal flow working condition state of the choke valve and the Christmas tree, performing operator mapping reasoning on the internal flow regions of the choke valve and the Christmas tree to obtain the pressure change and flow velocity change states of each flow region; performing physical consistency correction on the pressure change and flow velocity change states of each flow region, and simultaneously identifying the rotational dominant flow characteristics of the choke valve throttling part, the Christmas tree corner and the valve cavity region; time correlation and scale unification of the rotational dominant flow characteristics and the local pressure change characteristics of the choke valve and the Christmas tree to obtain the equivalent choke characteristic parameters.

4. The method for regulating formation pressure during offshore oilfield injection based on environmental protection synergy of claim 1, characterized in that: The effective injection pressure is obtained by the following steps, time correlation of the wellhead injection pressure in the reinjection basic operation parameter set with the equivalent choke characteristic parameters to establish a choke correction relationship; according to the choke correction relationship, correcting the wellhead injection pressure change during the reinjection process to form a wellhead pressure evolution state; By using the wellhead pressure evolution state as the basis for correction, the wellhead injection pressure is uniformly corrected to obtain the effective injection pressure.

5. The method for regulating formation pressure during offshore oilfield injection based on environmental protection synergy according to claim 4, characterized in that: The steps for obtaining the pressure response results are as follows: The process of effective injection pressure changing over time is organized and serialized to construct an injection pressure change sequence. Based on the injection pressure change sequence, dynamic response analysis is performed on the formation pressure change over time to obtain pressure response results.

6. The method for regulating formation pressure during offshore oilfield injection based on environmental protection synergy according to claim 5, characterized in that: The steps to obtain the reinjection pressure state are as follows: Based on the pressure response results, determine the range of pressure variations that the formation can withstand under the current reinjection conditions; Under the constraint of pressure variation range, the control and planning of the reinjection pressure variation process under the condition of no backflow is carried out to obtain the reinjection pressure variation process; The reinjection pressure is uniformly regulated according to the change process of the reinjection pressure to form a reinjection pressure state.

7. The method for regulating formation pressure during offshore oilfield injection based on environmental protection synergy according to claim 6, characterized in that: The steps to obtain the safety constraint boundary are as follows: Using the reinjection pressure state as a unified operating condition basis, a safety assessment is conducted on the formation pressure response and formation pressure change state to form a formation-side safety assessment result. The pressure-bearing status of the throttle valve, the wellhead, and the water injection tubing is checked, and the pressure loss status of the sand control tubing during the reinjection process is estimated to form the equipment-side safety assessment results. By unifying and correlating the results of the formation-side safety assessment with the results of the equipment-side safety assessment, we can identify the synergistic constraint relationship between formation safety requirements and equipment bearing capacity. Based on the collaborative constraint relationship, the allowable pressure range that simultaneously satisfies the safety assessment results on the formation side and the equipment side is determined, thus obtaining the safety constraint boundary.

8. The method for regulating formation pressure during offshore oilfield injection based on environmental protection synergy of claim 1, wherein: The steps to obtain the optimal combination of reinjection pressure and reinjection displacement are as follows: Align the safety constraint boundary with the preset formation allowable pressure range to determine the feasible pressure range that can be used for reinjection control under the current reinjection conditions. Within the feasible pressure range, the reinjection pressure and corresponding reinjection discharge are screened and constrained to form a candidate combination range that meets the safety conditions; The optimal combination of reinjection pressure and reinjection displacement is obtained by selecting the combination of reinjection pressure and reinjection displacement from the candidate combination range that can achieve the best reinjection capacity without exceeding the feasible pressure range.

9. The method for regulating formation pressure during offshore oilfield injection based on environmental protection synergy according to claim 8, characterized in that: The steps to obtain the new reinjection pressure are as follows: The optimal combination of reinjection pressure and reinjection displacement is set as the control benchmark for the current reinjection operating condition. Under the constraint of the control benchmark, the reinjection process is continuously adjusted to form a stable reinjection operating state. Under stable reinjection operation, the change process of reinjection pressure over time is continuously recorded to obtain the new reinjection pressure.

10. The method for regulating formation pressure during offshore oilfield injection based on environmental collaboration, as claimed in claim 1, wherein: The steps for generating the pressure control parameter set are as follows: The new reinjection pressure is aligned with the pressure response results of the corresponding time period to form a pressure alignment sequence. Based on the pressure alignment sequence, the difference between the new reinjection pressure and the pressure response result is quantitatively analyzed to form pressure deviation characteristics; Based on the pressure deviation characteristics, the reinjection pressure level under stable reinjection operation is characterized and summarized to form a pressure control parameter set.

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