A method for evaluating dynamic characteristics of CCUS
By conducting simulation experiments on rock cores and establishing CCUS characteristic curves, the geological burial mechanism of CO2 in residual oil reservoirs and water layers was solved, enabling qualitative research and quantitative calculation, improving the CO2 replacement rate and burial rate, and providing scientific guidance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2022-10-31
- Publication Date
- 2026-07-21
Smart Images
Figure CN117990885B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of shale oil-bearing evaluation technology, specifically to a CCUS dynamic characteristic evaluation method. Background Technology
[0002] Carbon capture, utilization, and storage (CCUS) is a method of geologically storing CO2 in oil reservoirs. It simultaneously enhances oil recovery and achieves carbon sequestration, making it the most feasible and economically viable approach. Field statistics from the Jilin Oilfield's CO2-assisted oil recovery project show that the target reservoir's oil recovery can be increased by more than 10%, with an average injection of 2-3 tons of CO2 replacing 1 ton of crude oil. Therefore, the dual advantages of enhancing oil recovery and geologically storing CO2 are significant.
[0003] Many scholars have conducted research on CO2 enhanced oil recovery and CO2 geological storage, including analysis of CO2 storage mechanisms and effects, reliability analysis of CO2 capture and storage, and analysis of factors affecting CO2 enhanced oil recovery and storage. Cao Molei et al. (Cao Molei, Chen Jianping. Geological evaluation of CO2 storage site selection in deep saline aquifers [J]. Acta Geologica Sinica, 2022, 96(5):15.) studied the feasibility of CO2 storage in deep saline aquifers. Yuan Zhou et al. (Yuan Zhou, Liao Xinwei, Zhang Kuaile, et al. The effect of inorganic salt precipitation on oil recovery during CO2 flooding - a case study of Changqing Oilfield Chang 8 Block [J]. Petroleum Exploration and Development, 2021, 048(002):379-385.) conducted indoor displacement experiments to quantitatively simulate the effect of inorganic salt precipitation generated during CO2 injection on oil recovery. The experimental results showed that the porosity of the samples before and after CO2 displacement was positively correlated with the experimental temperature and displacement pressure difference. Inorganic salt precipitation was generated near the production well, which led to a deterioration in the oilfield development effect. Considering the precipitation effect, the recovery rate of the block after 20 years of CO2 flooding was 33.45%, while the recovery rate was 37.64% without considering the precipitation effect. Li Kunquan et al. (Li Kunquan, Li Ping, Wei Minzhang, et al. Pilot test of CO2 flooding and burial in Chang 8 ultra-low permeability reservoir in Huang 3 block of Changqing Oilfield [J]. Journal of Engineering Geology, 2021.) evaluated the adaptability and application potential of CO2 flooding and burial pilot test technology in ultra-low permeability reservoirs of Changqing Oilfield, and confirmed that CO2 flooding has a good prospect for further promotion in Changqing Oilfield.
[0004] Patent CN108828136B provides a qualitative and quantitative analysis method for indoor CO2 flooding, qualitatively and quantitatively dividing the CO2 flooding process into three different stages: the gas-free recovery stage, the gas emergence stage, and the gas channeling stage. Then, based on the changes in parameters during each stage, the CO2 flooding, gas channeling patterns, and enhanced oil recovery mechanisms are determined. Patent CN107941838B discloses a quantitative evaluation method for the influence of asphaltenes precipitation on pore throat distribution during carbon dioxide flooding, achieving a quantitative evaluation of the impact of asphaltenes precipitation on pore throat distribution during carbon dioxide flooding.
[0005] The above research findings mainly focus on the mechanism of CO2 enhanced oil recovery, without addressing the qualitative and quantitative study of the geological storage mechanism of CO2 in residual oil reservoirs and water layers. Jilin Oilfield has a long history of CO2 enhanced oil recovery development, and its underground reservoirs possess excellent conditions for CO2 geological storage. Therefore, it is urgent to conduct an assessment of the reservoir's adaptability to CO2 enhancement in Jilin Oilfield. Summary of the Invention
[0006] The purpose of this invention is to provide a dynamic characteristic evaluation method for CCUS, which realizes the qualitative study of CO2 sequestration mechanism and the quantitative calculation of CO2 storage volume through the analysis of dynamic characteristic curves.
[0007] To achieve the above objectives, this application proposes a CCUS dynamic feature evaluation method, including:
[0008] S1. Measure the dry weight and size of the core, then measure the core porosity and pore volume, saturate the core with formation water after vacuuming, and age the core.
[0009] S2. Place the core into the holder, and after the core is saturated with oil, perform water-drive oil treatment, setting the back pressure to pressure a;
[0010] S3. For the core in the holder: inject CO2 into the core at a constant rate until 100% gas is produced. After a period of gas production, close the outlet of the back pressure control device and inject CO2 at a constant rate to increase the pressure to pressure b. When the pressure transmission is balanced, inject CO2 again to the pressure b until the pressure transmission is balanced.
[0011] S4. Establish CCUS characteristic curves;
[0012] S5. Based on the dynamic characteristic parameter index change law of the CCUS characteristic curve at different stages, qualitatively determine the CO2 sequestration mechanism and quantitatively calculate the CO2 burial amount.
[0013] Furthermore, in step S3, after the second pressure transmission balance, the injection pressure, gas production, and water production data are monitored.
[0014] Furthermore, in step S4, a CCUS characteristic curve is established with the injected CO2 volume as the abscissa and the CO2 storage rate as the ordinate.
[0015] Furthermore, in step S4, the process of establishing the CCUS characteristic curve is divided into two stages: the dynamic burial stage and the sealing burial stage.
[0016] Furthermore, the dynamic storage stage refers to the stage of injecting CO2 at a constant rate to pressure a.
[0017] Furthermore, the sealing and burying stage refers to the stage where, after closing the gas outlet, pressurization continues until pressure b is reached.
[0018] Furthermore, the core sample is a long core sample made up of short core samples, and the length of the long core sample is not less than 60cm.
[0019] Furthermore, the pressure 'a' is the formation pressure.
[0020] Furthermore, the pressure b is the formation fracturing pressure.
[0021] Furthermore, the equipment used in the CO2 geological storage determination experiment included: a clamp, a displacement pump (flow rate accuracy of 1%), a pressure sensor (accuracy of 0.5%), an oil-water separator, a balance, a stopwatch, and vernier calipers; the experiment was conducted in accordance with the relevant standards of the People's Republic of China's petroleum and natural gas industry, GB / T 28912-2012 "Method for Determination of Relative Permeability of Two-Phase Fluids in Rocks".
[0022] Compared with the prior art, the above technical solution adopted in this invention has the following advantages: This invention conducts a rock physics simulation experiment on CO2 burial in long core samples, uses the injected CO2 volume as the abscissa and the CO2 burial rate as the ordinate to establish a CCUS dynamic characteristic curve. Through the analysis of the dynamic characteristic curve, a qualitative study of the CO2 sequestration mechanism and a quantitative calculation of the CO2 burial amount are realized, which can provide scientific guidance for the design of CO2 burial schemes in mines and indoor numerical simulation research. Attached Figure Description
[0023] Figure 1 This is an experimental setup for CO2 geological sequestration.
[0024] Figure 2 This is a dynamic curve of the replacement and pressure of the buried material in Scheme 1 of Example 1;
[0025] Figure 3 This is a dynamic curve of the dynamic buried amount and pressure in Scheme 1 of Example 1;
[0026] Figure 4 This is a dynamic curve of the replacement and pressure of the buried stock in Scheme 2 of Example 1;
[0027] Figure 5 This is a dynamic curve of the dynamic buried amount and pressure in Scheme 2 of Example 1;
[0028] Figure 6 This is a dynamic curve of the replacement and pressure of the buried material in Scheme 3 of Example 2;
[0029] Figure 7 This is a dynamic curve of the dynamic buried amount and pressure in Scheme 3 of Example 2;
[0030] Figure 8 This is a dynamic curve of the replacement and pressure of the buried material in Scheme 4 of Example 2;
[0031] Figure 9 This is a dynamic curve of dynamic buried quantity and pressure in Scheme 4 of Example 2. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application; that is, the described embodiments are only a part of the embodiments of this application, and not all of them. The components of the embodiments of this application described and shown in the accompanying drawings can typically be arranged and designed in various different configurations.
[0033] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.
[0034] It should be noted that relational terms such as "a" and "b" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0035] Example 1
[0036] To address the evaluation of the dynamic characteristics of CO2 sequestration in pure aquifers, this embodiment conducts a long core physical simulation experiment to qualitatively study the CO2 sequestration mechanism and quantitatively calculate the CO2 storage volume; the experimental setup includes... Figure 1 As shown.
[0037] To study the impact of sealing on replacement burial capacity, two schemes were used for comparative experiments: Scheme 1 did not consider sealing, while Scheme 2 considered sealing.
[0038] Since the experiment simulates a pure water layer, saturated oil is not required.
[0039] This embodiment presents a CCUS dynamic feature evaluation method, which includes the following steps:
[0040] Option 1:
[0041] (1) Measure the dry weight and size of the core, then measure the porosity and pore volume of the core, saturate the core with formation water after vacuuming, and age the core.
[0042] Table 1 shows the statistical table of physical properties of long cores used in Scheme 1 and Scheme 2 of Example 1. The porosity and permeability are the average values of porosity and permeability of each spliced short core.
[0043] Table 1
[0044] Serial Number serial number Pore volume / ml Length / cm Porosity % <![CDATA[Permeability (10 -3 μm 2 )]]> 1 Option 1 37.97 62.15 12.28 2.31 2 Option 2 38.73 60.47 12.88 3.05
[0045] (2) Place the core into the holder, and after the water injection is stable, set the back pressure at the outlet end to 23 MPa (formation pressure);
[0046] (3) Inject CO2 at a rate of 0.02 ml / min until 100% of the gas is visible;
[0047] (4) During the experiment, the gas volume, water volume and injection pressure were monitored throughout the process.
[0048] like Figure 2 and Figure 3 The diagram shows the displacement / dynamic displacement and pressure dynamic curves for Scheme 1. With increasing injection volume, the displacement volume, displacement rate, and gas-liquid ratio all increase, stabilizing after 100% gas production. The injection pressure initially increases and then stabilizes, slightly decreasing after 100% gas production. Due to increased gas output in the later stages, the dynamic displacement rate gradually decreases. The dynamic displacement is defined as the difference between the injected and produced gas volumes. The dynamic displacement rate is the ratio of the dynamic displacement to the injected gas volume.
[0049] Option 2:
[0050] (1) Measure the dry weight and size of the core, measure the porosity and pore volume of the core, saturate the core with formation water after vacuuming, and age the core.
[0051] (2) Place the core into the holder, and after the water injection is stable, set the back pressure at the outlet end to 23 MPa (formation pressure);
[0052] (3) Inject CO2 at a rate of 0.02 ml / min until 100% gas is produced; after a period of gas production, close the outlet of the back pressure control device, inject CO2 to increase the pressure to 40 MPa (rock fracture pressure), and wait for the pressure transmission to balance; inject CO2 again to 40 MPa, stop injection, and then balance the pressure transmission again (repeat 2 times).
[0053] (4) After sealing for a period of time, open the outlet, reduce the pressure and exhaust the extraction to 23MPa, and inject CO2 at a constant rate of 0.02ml / min;
[0054] (5) During the experiment, the gas volume, water volume and injection pressure were monitored throughout the process.
[0055] like Figure 4 and Figure 5 The figure shows the displacement / dynamic displacement volume and pressure dynamic curves for Scheme 2. Before 100% gas breakthrough, the dynamic changes are consistent with Scheme 1. Afterwards, through three rounds of pressurization to 40 MPa (formation fracture pressure), the pressure stabilized in the long core and was sealed for a period before depressurization exhaustion and subsequent CO2 injection. During the exhaustion and subsequent injection stages, both the displacement rate and displacement volume increased to some extent, especially during the exhaustion stage, where the increase was more significant.
[0056] Comparing the two sets of experiments, the replacement rate and burial volume at different stages are as follows:
[0057] Table 2: Comparison of Replacement Capacity between Scheme 1 and Scheme 2
[0058]
[0059] Table 3: Dynamic Buried Stock Volume at Different Stages of Scheme 1 and Scheme 2
[0060]
[0061] The above comparison shows that under the target reservoir conditions, direct CO2 injection into a pure water layer can achieve a replacement rate of 41.60%–41.83%, and after a period of storage, the replacement rate can reach 45.44%. This demonstrates that CO2, after being stored for a period of time, fully contacts the rock and formation water in the reservoir, which helps to improve the replacement and storage rate.
[0062] In pure water layers, pressurized storage helps to increase the displacement storage rate; the actual storage volume is higher than the displacement storage volume, mainly because some CO2 is dissolved and stored; experiments show that pressurized storage can be carried out after depletion, and 0.27 PV of CO2 can be added.
[0063] Example 2:
[0064] To address the issue of evaluating the dynamic characteristics of CCUS in water-driven residual oil reservoirs, Example 2 conducts a long core physical simulation experiment to qualitatively study the CO2 sequestration mechanism and quantitatively calculate the CO2 burial volume.
[0065] To study the impact of sealing on replacement burial capacity, two schemes were used for comparative experiments: Scheme 3 did not consider sealing, while Scheme 4 considered sealing.
[0066] This embodiment presents a CCUS dynamic feature evaluation method, which includes the following steps:
[0067] Option 3:
[0068] (1) Measure the dry weight and size of the core, measure the porosity and pore volume of the core, saturate the core with formation water after vacuuming, and age the core.
[0069] Table 4 shows the statistical table of physical properties of the long cores used in Schemes 3 and 4 of Example 2. The porosity and permeability are the average values of porosity and permeability of each spliced short core.
[0070] Table 4
[0071] Serial Number serial number Pore volume / ml Length / cm Porosity % <![CDATA[Permeability (10 -3 μm 2 )]]> 1 Option 3 35.60 62.15 11.52 1.69 2 Option 4 36.29 60.75 11.74 1.96
[0072] (2) The core is placed in the holder, and after the core is saturated with oil, it is subjected to water flooding treatment. The system back pressure is set to 23 MPa.
[0073] (3) Inject CO2 at a rate of 0.02 ml / min until 100% of the gas is visible;
[0074] (4) During the experiment, the gas volume, water volume and injection pressure were monitored throughout the process.
[0075] like Figure 6 and Figure 7 The diagram shows the displacement / dynamic storage volume and pressure dynamic curves for Scheme 3. In the CO2 injection stage of Scheme 3, as the injection volume increases, the storage volume, displacement rate, and gas-liquid ratio all initially increase and then stabilize. The injection pressure initially increases, then decreases after gas is observed, stabilizing at 100% gas observation. After gas emission, the emission volume increases, leading to a gradual decrease in the dynamic storage rate. The dynamic storage volume is defined as the difference between the injected gas volume and the produced gas volume. The dynamic storage rate is the ratio of the dynamic storage volume to the injected gas volume.
[0076] Option 4:
[0077] (1) Measure the dry weight and size of the core, measure the porosity and pore volume of the core, saturate the core with formation water after vacuuming, and age the core.
[0078] (2) The core is placed in the holder, and after the core is saturated with oil, it is subjected to water flooding treatment, and the back pressure is set to 23 MPa;
[0079] (3) Inject CO2 at a rate of 0.02 ml / min until 100% gas is seen; after a period of gas outage, close the outlet, inject CO2 to increase the pressure to 40 MPa (rock fracture pressure), and wait for the pressure conduction to balance; inject CO2 to the inlet to reach 40 MPa again, stop injection and then balance the pressure conduction again (repeat 2 rounds).
[0080] (4) After sealing for a period of time, open the outlet, reduce the pressure and exhaust the extraction to 23MPa, and inject CO2 at a constant rate of 0.02ml / min;
[0081] (5) During the experiment, the gas volume, water volume and injection pressure were monitored throughout the process.
[0082] like Figure 8 and Figure 9 The figure shows the displacement / dynamic storage volume and pressure dynamic curves for Scheme 4. It can be seen that the dynamic changes in Scheme 4 before 100% gas breakthrough are consistent with those in Scheme 3. After three rounds of pressurization to 40 MPa (formation fracture pressure), the pressure was stabilized in the long core and then sealed for a period of time before depressurization exhaustion and subsequent CO2 injection. During the exhaustion and subsequent injection stages, both the displacement storage rate and dynamic storage volume increased to some extent. After gas emergence, the dynamic storage rate gradually decreased as the gas output increased. The displacement rate and storage volume results at different stages are compared between the two sets of experiments as follows:
[0083] Table 5: Comparison of Replacement Capacity between Scheme 1 and Scheme 2
[0084]
[0085] Table 6: Dynamic Buried Stock Volume at Different Stages of Scheme 1 and Scheme 2
[0086]
[0087] The above comparison shows that under the target reservoir conditions, direct injection of CO2 into the water-driven residual oil reservoir can achieve a replacement rate of 43.54% to 44.10%. After a period of storage, the replacement rate can reach 48.36%, indicating that CO2 storage helps to improve the replacement and storage rate.
[0088] Meanwhile, comparing the replacement rates of Scheme 1 (41.60%) and Scheme 2 (45.44%) in Example 1, the residual oil reservoir has a higher CO2 replacement rate than the pure water reservoir, indicating a stronger replacement and burial capacity.
[0089] from Figure 8 and Figure 9 It can be seen that pressurization and sequestration in residual oil reservoirs helps to improve the displacement burial rate; since some CO2 is dissolved in it, the burial amount is higher than the displacement burial amount; experiments show that pressurization and sequestration after flooding can continue to burial 0.33PV of CO2; the displacement rate of residual oil reservoirs is higher than that of pure water reservoirs.
[0090] This experiment can simultaneously obtain the recovery levels at different stages, thus providing a foundation for subsequent research on enhanced carbon dioxide recovery and integrated recovery and burial processes. The recovery levels at different stages are summarized below:
[0091] Table 7: Comparison of recovery rates at different stages of Scheme 3 and Scheme 4
[0092]
[0093] It can be seen that CO2 injection can increase the water drive recovery rate by about 15%, and after pressurization and storage, the recovery rate can be further increased (by about 2.5 percentage points).
[0094] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.
Claims
1. A CCUS dynamic feature evaluation method, characterized in that, include: S1. Measure the dry weight and size of the core, then measure the core porosity and pore volume, saturate the core with formation water after vacuuming, and age the core. S2. Place the core into the holder, and after the core is saturated with oil, perform water-drive oil treatment, setting the back pressure to pressure a; S3. Conduct a CO2 geological burial test on the core in the holder: Inject CO2 into the core at a constant rate until 100% gas is seen. After a period of gas emission, close the outlet of the back pressure control device and inject CO2 at a constant rate to increase the pressure to pressure b. When the pressure transmission is balanced, inject CO2 again to the pressure b until the pressure transmission is balanced. S4. Establish CCUS characteristic curves; S5. Based on the dynamic characteristic parameter index change law of the CCUS characteristic curve at different stages, qualitatively determine the CO2 sequestration mechanism and quantitatively calculate the CO2 storage amount. In step S4, a CCUS characteristic curve is established with the injected CO2 volume as the x-axis and the CO2 storage rate as the y-axis. The process of establishing CCUS characteristic curves is divided into two stages: dynamic burial stage and sealing burial stage. The dynamic storage stage refers to the stage of injecting CO2 at a constant rate to pressure a; The sealing and burying stage refers to the stage where, after the air outlet is closed, pressurization continues until pressure b is reached; The pressure 'a' is the formation pressure; The pressure b is the fracture pressure of the formation.
2. The CCUS dynamic feature evaluation method according to claim 1, characterized in that, In step S3, the injection pressure, gas production, and water production data are monitored throughout the process.
3. The CCUS dynamic feature evaluation method according to claim 1, characterized in that, The core sample is a long core sample made up of short core samples, and the length of the long core sample is not less than 60cm.
4. The CCUS dynamic feature evaluation method according to claim 1, characterized in that, The equipment used in the CO2 geological burial determination experiment included: a clamp, a displacement pump, a pressure sensor, an oil-water separator, a balance, a stopwatch, and vernier calipers; the experiment was conducted in accordance with the relevant standards of the People's Republic of China's petroleum and natural gas industry, GB / T 28912-2012 "Method for Determination of Relative Permeability of Two-Phase Fluids in Rocks".