Four-dimensional seismic depth domain velocity model method for oil sand reservoir exploitation monitoring

Abstract

The invention discloses a four-dimensional seismic depth domain velocity model method for oil sand reservoir exploitation monitoring, and the method comprises the following steps: S101, carrying out the conversion smoothing of a reference earthquake according to a time domain velocity model, and obtaining an initial velocity model; s102, performing pre-stack depth migration on a reference earthquake by using an initial velocity model to obtain an initial depth domain seismic section and a gather; step S103, for a reference earthquake, picking up residual delay on an initial depth domain seismic gather, and converting the residual delay into a residual offset equation set through ray tracing; according to the method, the change of the underground depth domain speed information in the steam-assisted gravity oil displacement process is truly reflected, and the change of the speed information is used for mining monitoring of the oil sand reservoir of the steam-assisted gravity oil displacement, so that the depth domain speed change between a reference earthquake and a monitoring earthquake and a corresponding depth domain seismic section can be obtained; therefore, the influence of steam and the change rule of the reservoir can be observed.

Description

Technical Field

[0001] The invention relates to the technical field of oil sand reservoir exploitation monitoring, in particular to a four-dimensional seismic depth domain velocity model method for oil sand reservoir exploitation monitoring. Background Art

[0002] Steam Assisted Gravity Drainage (SAGD) is an oil recovery method in which steam is injected into the oil reservoir from a vertical well or a horizontal well above a horizontal production well near the bottom of the reservoir, and the heated crude oil and steam condensate are produced from the horizontal well at the bottom of the reservoir.

[0003] Four-dimensional seismic refers to the process of monitoring the dynamics of oil and gas reservoirs by obtaining differential seismic information through repeated three-dimensional seismic observations of the same work area at different times using the same observation method.

[0004] Before or in the early stage of steam-assisted gravity recovery, three-dimensional seismic observation is carried out on the work area to obtain corresponding baseline seismic information. Thereafter, the above-mentioned steam is continuously injected within a certain period of time (such as within half a year), and then the work area is again subjected to three-dimensional seismic observation in the same observation method to obtain corresponding monitoring seismic information. The difference between the monitoring seismic information and the baseline seismic information is used to monitor the exploitation of oil sands and oil and gas reservoirs.

[0005] Commonly used monitoring information based on four-dimensional seismic is the time delay and amplitude change obtained on the time-shifted seismic profile. Steam injection will cause a decrease in the reservoir space velocity. Reasonable depth domain velocity model difference information can not only truly reflect the changes in underground velocity information, but also be used for process monitoring of steam-assisted gravity oil reservoir exploitation. Existing technology uses four-dimensional attributes such as time delay and amplitude change obtained on the pre-stack time-shifted data profile for monitoring, but it is difficult to obtain a reliable depth domain velocity model through the time-shifted velocity method, and thus it is difficult to obtain reasonable depth domain velocity difference information.

[0006] To this end, the present invention provides a four-dimensional seismic depth domain velocity model method for oil sand reservoir exploitation monitoring, which aims to truly reflect the changes in underground depth domain velocity information during steam-assisted gravity oil recovery. The changes in this velocity information are used for oil sand reservoir exploitation monitoring in steam-assisted gravity oil recovery. The depth domain velocity changes between the benchmark earthquake and the monitoring earthquake and the corresponding depth domain seismic profiles can be obtained, allowing us to observe the influence of steam and the changing laws of the reservoir. Summary of the invention

[0007] The purpose of the present invention is to provide a four-dimensional seismic depth domain velocity model method for oil sand reservoir exploitation monitoring to solve the problems raised in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: a four-dimensional seismic depth domain velocity model method for oil sand reservoir exploitation monitoring, comprising the following steps:

[0009] Step S101: for a benchmark earthquake, an initial velocity model is obtained by smoothing the time domain velocity model;

[0010] Step S102: For the reference earthquake, use the initial velocity model to perform prestack depth migration to obtain initial depth domain seismic profiles and gathers;

[0011] Step S103: for the reference earthquake, the residual delay is picked up on the initial depth domain seismic gather, the residual delay is converted into a residual migration equation group by ray tracing, the residual migration equation group is converted into a residual velocity field by reflection wave tomography inversion, the velocity update is obtained, and then the updated depth domain velocity model is obtained;

[0012] Step S104: For the benchmark earthquake, use the updated depth domain velocity model to perform prestack depth migration to obtain updated depth domain velocity profile and gather data;

[0013] Step S105: for the reference earthquake, determine whether the depth residual delay of the depth domain seismic trace gather output in S104 is less than the allowable error;

[0014] Step S106: If yes, stop updating, use the velocity model used in S104 as the final depth-domain velocity model of the benchmark earthquake, and use the seismic profile output by S104 as the final depth-domain seismic profile of the benchmark earthquake;

[0015] Step S107: If not, repeat steps S103-S104 to continue updating until the output depth domain seismic trace gathers have a depth residual delay less than the allowable error, and the velocity model at this time is used as the final depth domain velocity model of the benchmark earthquake, and the output seismic profile at this time is used as the final depth domain seismic profile of the benchmark earthquake;

[0016] Step S108: for the monitoring earthquake, the final depth domain velocity model of the benchmark earthquake is used as the initial velocity model of the monitoring data, and pre-stack depth migration is performed to obtain the initial depth domain seismic profile and gather data of the monitoring earthquake data;

[0017] Step S109: for the monitored earthquake, the residual delay is picked up on the initial depth domain seismic gather, the residual delay is converted into a residual migration equation group by ray tracing, the residual migration equation group is converted into a residual velocity field by reflection wave tomography inversion, the velocity update is obtained, and then the updated depth domain velocity model is obtained;

[0018] Step S110: For the monitored earthquake, use the updated depth domain velocity model to perform prestack depth migration to obtain updated depth domain velocity profile and gather data;

[0019] Step S111: for the monitored earthquake, determine whether the depth residual delay of the depth domain seismic trace gather outputted in S110 is less than the allowable error;

[0020] Step S112: If yes, stop updating, use the velocity model used in S110 as the final depth domain velocity model for monitoring earthquakes, and use the seismic profile output by S110 as the final depth domain seismic profile for monitoring earthquakes;

[0021] Step S113: If not, repeat steps S109-S110 to continue updating until the output depth domain seismic track set depth residual delay is less than the allowable error. The velocity model at this time is used as the final depth domain velocity model for monitoring earthquakes, and the output seismic profile at this time is used as the final depth domain seismic profile for monitoring earthquakes.

[0022] Preferably, the method further comprises the following steps:

[0023] Step S114: subtract the final depth-domain velocity model of the benchmark model from the final depth-domain velocity model of the monitored earthquake to obtain an absolute change in the depth-domain velocity.

[0024] Preferably, the method further comprises the following steps:

[0025] Step S115: Divide the change obtained in S114 by the final depth-domain velocity model of the reference model to obtain a relative change in the depth-domain velocity.

[0026] Preferably, the method further comprises the following steps:

[0027] Step S116: The absolute change amount and relative change amount of the velocity in the depth domain can be used to monitor the change pattern of the oil sand reservoir in steam-assisted gravity flooding.

[0028] The present invention provides a four-dimensional seismic depth domain velocity model method for oil sand reservoir exploitation monitoring. It has the following beneficial effects:

[0029] (1) Compared with the prestack time migration section, the present invention uses the prestack depth migration to achieve accurate positioning of seismic data. The velocity analysis method that only relies on the time domain migration imaging method is often difficult to obtain a reliable depth domain velocity model, which may cause the illusion of underground structure. The existing technology uses four-dimensional attributes such as time delay and amplitude change obtained on the prestack time migration digital section to monitor the change law of oil sands and oil and gas reservoirs. Through the technical solution of the present invention, it is possible to obtain reasonable depth domain velocity models of the benchmark earthquake and the monitoring earthquake, and then obtain the depth domain velocity change between the benchmark earthquake and the monitoring earthquake and the corresponding depth domain seismic section, so that we can more reasonably obtain the impact of steam injection on the oil sands and oil and gas reservoirs and the corresponding change law. This more accurate velocity change information can be used for steam-assisted gravity oil recovery oil sand reservoir exploitation monitoring.

[0030] (2) The present invention truly reflects the changes in underground depth-domain velocity information during steam-assisted gravity oil recovery. The changes in velocity information are used for monitoring oil sand reservoir exploitation in steam-assisted gravity oil recovery. The depth-domain velocity changes between the baseline earthquake and the monitoring earthquake and the corresponding depth-domain seismic profiles can be obtained, so that we can observe the influence of steam and the changing patterns of the reservoir. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] A preferred embodiment of a four-dimensional seismic depth domain velocity model method for monitoring oil sand reservoir exploitation provided by the present invention: A four-dimensional seismic depth domain velocity model method for monitoring oil sand reservoir exploitation comprises the following steps:

[0033] Step S101: for a benchmark earthquake, an initial velocity model is obtained by smoothing the time domain velocity model;

[0034] Step S102: For the reference earthquake, use the initial velocity model to perform prestack depth migration to obtain the initial depth domain seismic profile and gathers;.

[0035] Step S103: for the reference earthquake, the residual delay is picked up on the initial depth domain seismic gather, the residual delay is converted into a residual migration equation group by ray tracing, the residual migration equation group is converted into a residual velocity field by reflection wave tomography inversion, the velocity update is obtained, and then the updated depth domain velocity model is obtained;

[0036] Step S104: For the benchmark earthquake, use the updated depth domain velocity model to perform prestack depth migration to obtain updated depth domain velocity profile and gather data;

[0037] Step S105: for the reference earthquake, determine whether the depth residual delay of the depth domain seismic trace gather output in S104 is less than the allowable error;

[0038] Step S106: If yes, stop updating, use the velocity model used in S104 as the final depth-domain velocity model of the benchmark earthquake, and use the seismic profile output by S104 as the final depth-domain seismic profile of the benchmark earthquake;

[0039] Step S107: If not, repeat steps S103-S104 to continue updating until the output depth domain seismic trace gathers have a depth residual delay less than the allowable error, and the velocity model at this time is used as the final depth domain velocity model of the benchmark earthquake, and the output seismic profile at this time is used as the final depth domain seismic profile of the benchmark earthquake;

[0040] Step S108: for the monitoring earthquake, the final depth domain velocity model of the benchmark earthquake is used as the initial velocity model of the monitoring data, and pre-stack depth migration is performed to obtain the initial depth domain seismic profile and gather data of the monitoring earthquake data;

[0041] Step S109: for the monitored earthquake, the residual delay is picked up on the initial depth domain seismic gather, the residual delay is converted into a residual migration equation group by ray tracing, the residual migration equation group is converted into a residual velocity field by reflection wave tomography inversion, the velocity update is obtained, and then the updated depth domain velocity model is obtained;

[0042] Step S110: For the monitored earthquake, use the updated depth domain velocity model to perform prestack depth migration to obtain updated depth domain velocity profile and gather data;

[0043] Step S111: for the monitored earthquake, determine whether the depth residual delay of the depth domain seismic trace gather outputted in S110 is less than the allowable error;

[0044] Step S112: If yes, stop updating, use the velocity model used in S110 as the final depth domain velocity model for monitoring earthquakes, and use the seismic profile output by S110 as the final depth domain seismic profile for monitoring earthquakes;

[0045] Step S113: If not, repeat steps S109-S110 to continue updating until the output depth domain seismic trace gather depth residual delay is less than the allowable error, and the velocity model at this time is used as the final depth domain velocity model for monitoring earthquakes, and the output seismic profile at this time is used as the final depth domain seismic profile for monitoring earthquakes;

[0046] Step S114: subtracting the final depth-domain velocity model of the benchmark model from the final depth-domain velocity model of the monitored earthquake to obtain an absolute change in the depth-domain velocity;

[0047] Step S115: Divide the change amount obtained in S114 by the final depth domain velocity model of the reference model to obtain a relative change amount of the depth domain velocity;

[0048] Step S116: The absolute change amount and relative change amount of the velocity in the depth domain can be used to monitor the change pattern of the oil sand reservoir in steam-assisted gravity flooding.

[0049] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A four-dimensional seismic depth domain velocity model method for oil sand reservoir exploitation monitoring, characterized in that: The following steps are involved: Step S101: for a benchmark earthquake, an initial velocity model is obtained by smoothing the time domain velocity model; Step S102: For the reference earthquake, use the initial velocity model to perform prestack depth migration to obtain initial depth domain seismic profiles and gathers; Step S103: for the reference earthquake, the residual delay is picked up on the initial depth domain seismic gather, the residual delay is converted into a residual migration equation group by ray tracing, the residual migration equation group is converted into a residual velocity field by reflection wave tomography inversion, the velocity update is obtained, and then the updated depth domain velocity model is obtained; Step S104: For the benchmark earthquake, use the updated depth domain velocity model to perform prestack depth migration to obtain updated depth domain velocity profile and gather data; Step S105: for the reference earthquake, determine whether the depth residual delay of the depth domain seismic trace gather output in S104 is less than the allowable error; Step S106: If yes, stop updating, use the velocity model used in S104 as the final depth-domain velocity model of the benchmark earthquake, and use the seismic profile output by S104 as the final depth-domain seismic profile of the benchmark earthquake; Step S107: If not, repeat steps S103-S104 to continue updating until the output depth domain seismic trace gathers have a depth residual delay less than the allowable error, and the velocity model at this time is used as the final depth domain velocity model of the benchmark earthquake, and the output seismic profile at this time is used as the final depth domain seismic profile of the benchmark earthquake; Step S108: for the monitoring earthquake, the final depth domain velocity model of the benchmark earthquake is used as the initial velocity model of the monitoring data, and pre-stack depth migration is performed to obtain the initial depth domain seismic profile and gather data of the monitoring earthquake data; Step S109: for the monitored earthquake, the residual delay is picked up on the initial depth domain seismic gather, the residual delay is converted into a residual migration equation group by ray tracing, the residual migration equation group is converted into a residual velocity field by reflection wave tomography inversion, the velocity update is obtained, and then the updated depth domain velocity model is obtained; Step S110: For the monitored earthquake, use the updated depth domain velocity model to perform prestack depth migration to obtain updated depth domain velocity profile and gather data; Step S111: for the monitored earthquake, determine whether the depth residual delay of the depth domain seismic trace gather outputted in S110 is less than the allowable error; Step S112: If yes, stop updating, use the velocity model used in S110 as the final depth domain velocity model for monitoring earthquakes, and use the seismic profile output by S110 as the final depth domain seismic profile for monitoring earthquakes; Step S113: If not, repeat steps S109-S110 to continue updating until the output depth domain seismic track set depth residual delay is less than the allowable error. The velocity model at this time is used as the final depth domain velocity model for monitoring earthquakes, and the output seismic profile at this time is used as the final depth domain seismic profile for monitoring earthquakes.

2. The four-dimensional seismic depth domain velocity model method for oil sand reservoir exploitation monitoring according to claim 1 is characterized by: The following steps are also included: Step S114: subtract the final depth-domain velocity model of the benchmark model from the final depth-domain velocity model of the monitored earthquake to obtain an absolute change in the depth-domain velocity.

3. The four-dimensional seismic depth domain velocity model method for oil sand reservoir exploitation monitoring according to claim 1 is characterized by: The following steps are also included: Step S115: Divide the change obtained in S114 by the final depth-domain velocity model of the reference model to obtain a relative change in the depth-domain velocity.

4. The four-dimensional seismic depth domain velocity model method for oil sand reservoir exploitation monitoring according to claim 1 is characterized by: The following steps are also included: Step S116: The absolute change amount and relative change amount of the velocity in the depth domain can be used to monitor the change pattern of the oil sand reservoir in steam-assisted gravity flooding.