Method for determining the distribution of a closed brine formation in which CO2 can be stored

Abstract

The application discloses a method for determining the distribution range of a closed brine formation capable of storing CO2 underground, comprising the following steps: determining the development horizon and thickness of the brine formation according to drilling data; determining the planar distribution range of the brine formation capable of storing CO2 according to the development horizon and thickness in combination with seismic data; determining the distribution range of the open brine formation capable of exchanging with surface water in the denudation area; determining the distribution range of the open brine formation capable of exchanging with surface water in the central fault development area of the basin; and subtracting the distribution range of the two open brine formations from the planar distribution range of the brine formation capable of storing CO2 to obtain the distribution range of the closed brine formation. The method has the beneficial effect that the planar distribution range of the brine formation is determined first, then the interference range is removed, and finally the distribution range of the brine formation capable of storing CO2 is obtained, thereby providing a quick solution for determining the target area of the brine formation when carrying out the CO2 geological storage research in the sedimentary basin, and improving the work efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of CO2 geological storage, and particularly relates to a method for determining the distribution range of a closed brine formation capable of storing CO2. BACKGROUND

[0002] CO2 is stored in a closed brine formation in the underground to reduce the content of CO2 in the air and slow down the speed of global warming. When CO2 is geologically stored in a closed brine formation, the distribution of the closed brine formation in the underground needs to be determined in advance.

[0003] The mechanism of storing CO2 in a brine formation is mainly that, after CO2 is injected into the brine formation, the CO2 spreads in the porous medium, replaces part of the formation water, gradually fills the entire flow space, and then is stored through a series of physical and chemical processes. The physical and chemical processes can be divided into physical capture and chemical capture. The physical capture is mainly hydrodynamic capture, and the chemical capture is mainly achieved through carbonate mineralization and carbonate dissolution. A large amount of CO2 is stored through physical capture, i.e. hydrodynamic storage. Hydrodynamic storage, also known as migration storage, refers to the fact that, under normal circumstances, CO2 slowly diffuses upward, and before it is transported to the surface for a long time, the CO2 is stored through various mechanisms such as residual gas storage (CO2 is stored in the pore space under the action of capillary force due to the existence of displacement and suction phase hysteresis), dissolution storage, ion storage (CO2 dissolved in water generates dissolution storage and ion storage), and mineral storage (CO2 further reacts with surrounding rocks to generate new minerals). An important feature of the brine formation capable of storing CO2 is its sealing property, i.e. the brine formation does not exchange with surface water. Once surface water invades, an open system will be formed, and the brine formation will exchange with the surface water, which will then bring the CO2 stored in the brine formation to the surface, resulting in a failure of the storage.

[0004] The hydrodynamic environment of a sedimentary basin is restricted by tectonic activities, stratigraphic structure, and surface hydrological conditions during the evolution of the basin, and has different hydrodynamic characteristics at different evolution stages. According to the macroscopic hydrodynamic cycle characteristics of the basin, the hydrodynamic evolution can be divided into two modes: compaction flow and gravity flow. During the period of continuous subsidence of the basin and large amount of deposition, the compaction effect is obvious, and at this time, the main water flow in the basin is compaction flow, and the water flow direction mainly moves from the center of the basin to the edge of the basin from deep to shallow. With the completion of the basin filling, the compaction effect tends to be weak, and the edge of the basin is uplifted and tilted due to the later crust movement, and at this time, the hydrodynamic environment in the basin is mainly gravity flow, and the water flow flows from the place with high potential to the center of the basin with lower potential, so that the deep formation water exchanges with the surface water.

[0005] According to the characteristics that the closed salt water layer does not exchange with surface water, and according to the water dynamic evolution characteristics of the sedimentary basin, it can be known that the stratum deposition is started in the initial development period of the basin, when the stratum deposition thickness reaches a certain value, the compaction water flow is mainly in the basin, until the basin is completely formed, the fluid of the deep closed salt water layer always moves from the center of the basin to the edge of the basin, and does not exchange with the surface water. When the basin is uplifted and eroded, the surface water flows from the edge of the basin to the center of the basin under the action of gravity flow, and stops flowing and exchanging with the deep salt water layer when the permeability of the rock layer is poor. When the basin develops a fault that reaches the surface, the surface water flows along the fault under the action of gravity flow, and exchanges with the lower salt water layer, and stops further exchanging when the permeability of the rock layer is poor.

[0006] At present, there is no standard evaluation method for the closed salt water layer, which leads to slow progress of the guidance work of CO2 geological storage, and even failure of the storage. SUMMARY

[0007] In view of the above problems, the application provides a method for determining the distribution range of a closed salt water layer capable of storing CO2 underground, and mainly solves the problem of the distribution range of the closed salt water layer capable of storing CO2.

[0008] To solve the above technical problems, the technical scheme of the application is as follows:

[0009] A method for determining the distribution range of a closed salt water layer capable of storing CO2 underground, comprising the following steps:

[0010] Step 1: determining the development horizon and thickness of the salt water layer according to drilling data;

[0011] Step 2: determining the planar distribution range of the salt water layer capable of storing CO2 according to the development horizon and the thickness in combination with seismic data;

[0012] Step 3: determining the distribution range of the open salt water layer in which the eroded area exchanges with surface water;

[0013] Step 4: determining the distribution range of the open salt water layer in which the central faulted area of the basin exchanges with surface water;

[0014] Step 5: subtracting the two distribution ranges of the open salt water layer obtained in steps 3 and 4 from the planar distribution range of the salt water layer capable of storing CO2 to obtain the distribution range of the closed salt water layer.

[0015] In some embodiments, step one includes: creating a profile distribution map showing the relationship between formation water salinity and depth based on formation water salinity data from known wells in the study area; identifying the distribution of saline layers with salinity ≥10 g / L from the profile distribution map according to the standard for saline layers; and determining the development layer and the thickness based on the distribution of the saline layers.

[0016] In some embodiments, step two includes mapping the developed stratigraphic level and the thickness onto seismic data, and tracing and determining the maximum horizontal distribution range S of the saline layer. z Then, based on the analysis results of drilling and seismic data, the distribution range of sandstone with porosity greater than 10% on the plane is characterized, and the distribution range of the sandstone is compared with the maximum distribution range S of the brine layer on the plane. z Cross-sectional analysis was conducted to ultimately determine the planar distribution range S of the saline layer that is prone to CO2 injection. y .

[0017] In some embodiments, step three includes determining the type of rock strata in contact with surface water in the erosion zone; if the rock strata are mudstone, then the distribution range S of the saline layer where the erosion zone exchanges with surface water is determined. b Set to zero. If the rock stratum type is sandstone, calculate the contact area between the sandstone layer and surface water, and include this contact area in the distribution range S of the open saline layer where the sandstone layer exchanges with surface water in the erosion zone. b middle.

[0018] In some embodiments, step four includes determining whether the saline sandstone layer is in direct contact with the cross-section; if not, then determining the distribution range S of the open saline layer in the fault-developed area in the central basin where surface water exchanges with the water. d If zero is set, then calculate the contact area between the fault-developed zone in the central basin and surface water, and include this contact area in the distribution range S of the open saline layer where surface water exchanges with the fault-developed zone in the central basin. d middle.

[0019] In some embodiments, the method for calculating the distribution range of the sealed brine layer in step five is as follows:

[0020] S f =S y -S b -S d

[0021] In the formula, S f S represents the distribution range of closed saline formations capable of storing CO2. y For the planar distribution range of brine layers where CO2 can be easily injected, S b For Sy the distribution range of the open salt water layer in the denudation zone of the basin and the surface water, S d S y the distribution range of the open salt water layer in the denudation zone of the basin and the surface water, S

[0022] The beneficial effect of the present application is that the distribution range of the salt water layer is determined first, then the interference range is removed, and finally the distribution range of the salt water layer capable of storing CO2 is obtained, which can provide a quick solution for determining the target area of the salt water layer when carrying out CO2 geological storage research in a sedimentary basin, and improve work efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic diagram of the relationship between the formation water salinity and the depth;

[0024] Figure 2 is a schematic diagram for determining the closed salt water layer in the denudation zone of the basin;

[0025] Figure 3 is a schematic diagram for determining the closed salt water layer in the fault zone;

[0026] Figure 4 is a schematic diagram of the distribution range of the closed salt water layer. DETAILED DESCRIPTION

[0027] To make the purpose, technical scheme and advantages of the present application clearer and more explicit, the content of the present application will be further described in detail below in combination with the drawings and specific embodiments. It can be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application. In addition, it should be noted that only the parts related to the present application are shown in the drawings for the convenience of description.

[0028] The present embodiment proposes a method for determining the distribution range of the closed salt water layer capable of storing CO2 underground, which determines the planar distribution range of the salt water layer first, then removes the interference range, and finally obtains the distribution range of the closed salt water layer capable of storing CO2, which can provide a quick solution for determining the target area of the salt water layer when carrying out CO2 geological storage research in a sedimentary basin, and improve work efficiency.

[0029] The method mainly includes the following steps:

[0030] Step one, determining the development horizon and thickness of the salt water layer according to the drilling data;

[0031] In the present embodiment, step one includes, for example, Figure 1As shown, a profile distribution map showing the relationship between formation water salinity and depth was created based on formation water salinity data from known wells in the study area. According to the standard for saline layers, the distribution status of saline layers with salinity ≥10g / L was identified from the profile distribution map, and the development strata and thickness were determined based on the distribution status of the saline layers.

[0032] Step 2: Determine the planar distribution range of saline layers that are prone to CO2 injection based on the developmental horizon and thickness, combined with seismic data;

[0033] In this embodiment, step two includes mapping the developed layers and thicknesses onto the seismic data, and tracing and determining the maximum horizontal distribution range S of the saline layer. z Then, based on the analysis results of drilling and seismic data, the distribution range of sandstone with porosity greater than 10% on the plane was delineated, and the distribution range of sandstone was compared with the maximum distribution range S of the brine layer on the plane. z Cross-sectional analysis was conducted to ultimately determine the planar distribution range S of the brine layer that is prone to CO2 injection. y The lower limit of porosity for sandstone capable of CO2 sequestration is 10%. Therefore, the purpose of this step is to determine the distribution range of sandstone brine layers with porosity greater than 10% in the plane.

[0034] Step 3: Determine the distribution range of open saline layers where the erosion zone exchanges with surface water;

[0035] In this embodiment, step three includes determining the type of rock strata in contact with surface water in the erosion zone. If the rock strata are mudstone, then the distribution range S of the saline layer where the erosion zone exchanges with surface water is determined. b Set to zero. If the rock stratum type is sandstone, calculate the contact area between the sandstone layer and surface water, and include this contact area in the distribution range S of the open saline layer where the sandstone layer exchanges with surface water in the erosion zone. b The purpose of this step is to determine the distribution range of saline layers where the erosion zone exchanges with surface water.

[0036] Regional tectonic movements cause uplift and erosion of strata, leading to the exposure of deep strata in eroded areas and their connection with surface water. Surface water can then infiltrate the saline layer, affecting the CO2 sequestration capacity of this stratum. Due to the complexity of the geological conditions, the exchange patterns between surface water and formation water in eroded areas are mainly divided into two scenarios, such as... Figure 2 As shown: First, when mudstone is in contact with surface water, the poor porosity and permeability of mudstone can prevent surface water from seeping downwards, thus the underlying saline sandstone layer can still effectively seal CO2. Figure 2 (Case ①); Second, when the sandstone layer is in contact with surface water, due to the good pore connectivity of the sandstone layer, it can completely exchange with surface water, and the distribution range of this stratum should be excluded. Figure 2(Situation ②) This step ultimately requires determining the distribution range S of the open saline layer where the erosion zone exchanges with surface water. b .

[0037] Step 4: Determine the distribution range of open saline layers where surface water exchanges with fault-developed areas in the central basin.

[0038] In this embodiment, step four includes determining whether the saline sandstone layer is in direct contact with the cross-section. If not, the distribution range S of the open saline layer in the fault-developed area in the central basin where surface water exchanges with the water is determined. d If zero, calculate the contact area between the fault-developed area in the central basin and surface water, and include this contact area in the distribution range S of the open saline layer where surface water exchanges with the fault-developed area in the central basin. d The purpose of this step is to determine the distribution range of saline layers where surface water exchanges with the fault-developed area.

[0039] Some faults that extend to the surface can connect the strata with surface water, thus affecting the CO2 sequestration capacity of saline aquifers. For example... Figure 3 As shown, based on the contact between the strata and the fault plane, the contact relationships can be divided into the following two types: First, the saline sandstone layer does not contact the fault plane ( Figure 3 In the case of ①, it can still effectively seal CO2; secondly, the saline sandstone layer is in direct contact with the cross-section ( Figure 3 Situation ②) can exchange with surface water and should be excluded. This step ultimately needs to determine the distribution range S of open saline layers exchanging with surface water in the fault-developed area. d .

[0040] Step 5: Subtract the two open brine layer distribution ranges obtained in Steps 3 and 4 from the planar distribution range of the brine layer that is easy to inject CO2, and obtain the distribution range of the closed brine layer.

[0041] In step five, the method for calculating the distribution range of the sealed brine layer is as follows:

[0042] S f =S y -S b -S d

[0043] In the formula, S f S represents the distribution range of closed saline formations capable of storing CO2. y For the planar distribution range of brine layers where CO2 can be easily injected, S b For S y The distribution range of open saline layers where erosion zones exchange with surface water within the area, S d For S yThe distribution range of the open salt water layer which exchanges with surface water in the development area of the middle basin fault.

[0044] In the embodiment, the salt water layer which is easy to inject CO2 and is determined in step two is removed from the distribution range of the salt water layer in the study area on the basis of the distribution range of the salt water layer which exchanges with surface water due to denudation in step three and the distribution range of the salt water layer which exchanges with surface water due to the influence of the "through-the-sky fault" in step four, and finally, the remaining area is the distribution range of the closed salt water layer which can store CO2 in the deep part as shown in Figure 4

[0045] The above embodiment is only for explaining the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it accordingly, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the essence of the present application should be covered within the protection scope of the present application.​

Claims

1. A method for determining the extent of a closed saline formation that can store CO2 underground, characterized in that, The method comprises the following steps: Step one, determining the development horizon and thickness of the salt water layer according to the drilling data; Step two, determining the planar distribution range of the salt water layer easy to inject CO2 by combining the development horizon and thickness with the seismic data; Step three, determining the distribution range of the open salt water layer exchanged with the surface water in the denudation area; Step four, determining the distribution range of the open salt water layer exchanged with the surface water in the central fault development area of the basin; Step five, subtracting the two distribution ranges of the open salt water layer obtained in steps three and four from the planar distribution range of the salt water layer easy to inject CO2 to obtain the distribution range of the closed salt water layer.

2. The method of determining the extent of a saline formation for sequestration of CO2 underground according to claim 1, wherein The step one comprises making a profile distribution map of the relationship between the formation water salinity and the depth according to the formation water salinity data of the known drilling in the study area, finding out the distribution state of the salt water layer with the salinity ≥10 g / L from the profile distribution map according to the standard of the salt water layer, and determining the development horizon and the thickness according to the distribution state of the salt water layer.

3. The method of determining the extent of a saline formation for sequestration of CO2 underground according to claim 2, wherein The step two comprises calibrating the development layer and the thickness to seismic data, and tracking to determine the maximum distribution range S of the salt water layer plane z Then, according to the analysis results of drilling and seismic data, the sandstone distribution range of sandstone with porosity greater than 10% in the plane is described, and the sandstone distribution range is combined with the maximum distribution range S of the salt water layer plane z The intersection analysis is carried out, and finally the maximum distribution range S of the salt water layer plane easy to inject CO2 is determined y .

4. The method of determining the extent of a saline formation for sequestration of CO2 underground according to claim 3, wherein Step three includes determining the type of rock strata in contact with surface water in the erosion zone. If the rock strata are mudstone, then the distribution range S of the saline layer where the erosion zone exchanges with surface water is determined. b Set to zero. If the rock stratum type is sandstone, calculate the contact area between the sandstone layer and surface water, and include this contact area in the distribution range S of the open saline layer where the sandstone layer exchanges with surface water in the erosion zone. b middle.

5. The method of determining the extent of a saline formation for sequestration of CO2 underground according to claim 4, wherein The step four includes judging whether the salt water sandstone layer is directly in contact with the fault section, if not, the distribution range S of the open salt water layer in the basin middle fault development area and the surface water exchange d is zero, if yes, the contact area of the basin middle fault development area and the surface water is calculated, and the contact area of the basin middle fault development area and the surface water is added to the distribution range S of the open salt water layer in the basin middle fault development area and the surface water exchange d is zero, if yes, the contact area of the basin middle fault development area and the surface water is calculated, and the contact area of the basin middle fault development area and the surface water is added to the distribution range S of the open salt water layer in the basin middle fault development area and the surface water exchange 6. The method of determining the extent of a saline formation for sequestration of CO2 underground according to claim 5, wherein In the step five, the calculation method of the distribution range of the closed salt water layer is as follows: S f = S y - S b - S d wherein S f is the distribution range of the closed saline formation that can store CO2, S y is the planar distribution range of the saline formation that is easy to inject CO2, S b is S y is the distribution range of the open saline formation that exchanges with surface water in the denudation area within the range, S d is S y is the distribution range of the open saline formation that exchanges with surface water in the development area of the central fault of the basin within the range.

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