METHOD FOR STABILIZING CO2 MICROBUBBLE BY INJECTING NANOPARTICLES TO ENHANCE GEOLOGICAL STORAGE

Abstract

A method for enhancing geological storage by injecting nanoparticles to stabilize CO.sub.2 microbubbles, which belongs to the technical field of multiphase flow. The method first improves the physical properties of the fluid by pre-mixing CO.sub.2 and nanoparticles, and then the fluid is transported to the underground through high-pressure pipelines, and then CO.sub.2 microbubbles containing nanoparticles are generated through a dense perforated plate arranged by an injection well to improve the dissolution rate and sweep efficiency of the gas in the saline aquifer, so as to enhance the later mixing of the fluid. The combined injection can improve CO.sub.2 storage capacity and storage safety, and further reduce the risk of gas leakage in the reservoir.

Claims

1. A method for enhancing geological storage by injecting nanoparticles to stabilize CO.sub.2 microbubbles, comprising the following steps: step I: determining a location of an injection well; selecting a storage position to install the injection well, and installing a monitoring device (7) around the injection well; step II: obtaining nanoparticles; a raw material collection tank (1) containing raw materials for preparing nanoparticles entering into a nano-sand mill (2) via a pipeline (1a) for grinding, and then passing into a nanoparticle filter (4) via a pipeline (2a) and a valve (2b) to filter out the nanoparticles with a nanoparticle size <500 nm; the grind fineness of the nano-sand mill (2) being ≤200 nm; the nanoparticle filter (4) comprising a nanofiltration plate (5) with a diameter <500 nm and a leak detection sensor (3); step III: pre-mixing CO.sub.2 and nanoparticles; opening a CO.sub.2 valve (6b) and continuously introducing the CO.sub.2 into a mixer (6) at a constant flow rate through a CO.sub.2 high-pressure pipeline (6a); opening a nanoparticle valve (4a) so that the nanoparticles flow through a nanoparticle pipeline (4b) uniformly and constantly into the mixer (6), and obtaining a mixed fluid after mixing the two; the mixer (6) comprising a temperature and pressure monitoring device (11) and a high-pressure magnetic stirrer (12); step IV: generating CO.sub.2 microbubbles in a reservoir by the constant pressure injection; opening an injection well valve (6c), injecting the mixed fluid into the fluid in the reservoir while maintaining the reservoir pressure stable, placing a dense perforated plate (9) in a well shaft (10) of the injection well, and allowing the fluid to flow through the dense perforated plate (9) at the bottom of the well to generate the CO.sub.2 microbubbles containing nanoparticles; the dense perforated plate (9) using a corrosion-resistant material, and having an average pore size of 1 nm-1 μm; arranging an impurity filtering plate (8) in advance before the dense perforated plate (9); wherein the raw materials for preparing nanoparticles are carbon nanoparticles, strongly hydrophilic metal-based/metalloid nanoparticles, and/or strongly wettable industrial waste residues; the strongly hydrophilic metal-based/metalloid nanoparticles are SiO.sub.2 particles or Fe.sub.2O.sub.3 particles; the strong wet type industrial waste residues are waste cement powder or blast furnace slag.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0023] FIG. 1 is a flow chart of a method for enhancing geological storage by injecting nanoparticles to stabilize CO.sub.2 microbubbles.

[0024] FIG. 2 shows the effect of different concentrations of nanoparticles on improving convective interface stability.

[0025] In the figures: 1. raw material collection tank, 1a. pipeline, 2. nano mill, 2a. pipeline, 2b. valve, 3. leak detection sensor, 4. nanoparticle filter, 4a. nanoparticle valve, 4b. nanoparticle pipeline, 5. nanofiltration plate, 6. mixer, 6a. CO.sub.2 high-pressure pipeline, 6b. CO.sub.2 valve, 6c. injection well valve. 6d. injection well pipeline, 7. monitoring device, 8. impurity filtering plate, 9. dense perforated plate, 10. injection well shaft, 11. temperature and pressure monitoring device, 12. high-pressure magnetic stirrer.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Best Mode for Carrying Out the Invention Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example 1

[0027] FIG. 1 is a schematic diagram of a method for stabilizing CO.sub.2 microbubbles by injecting SiO.sub.2 nanoparticles to enhance geological storage, and the method is further described in conjunction with FIG. 1: [0028] step I: determining a location of an injection well; [0029] selecting the region with gentle terrain, stable geological structure, and good storage ability as the storage position, installing the injection well in a reasonable reservoir depth, installing monitoring devices 7 around the injection wells, and using deep and shallow monitoring technology to monitor the risk of leakage and blockage in real time; [0030] step II: obtaining SiO.sub.2 nanoparticles; [0031] charging the raw material collection tank 1 with the raw material for preparing SiO.sub.2 nanoparticles, the raw material entering through a pipeline into a nano-sand mill 2 for grinding, and then passing through a nanoparticle filter 4 to filter out nanoparticles with a nanoparticle size <500 nm. [0032] step III: pre-mixing CO.sub.2 and SiO.sub.2 nanoparticles; [0033] continuously introducing CO.sub.2 into the CO.sub.2 high-pressure pipeline at a suitable flow rate; then allowing the SiO.sub.2 nanoparticles to flow through the nanoparticles high-pressure pipeline into the mixer 6 uniformly and constantly, and both continuously introducing into the mixer until thoroughly mixing. [0034] step IV: generating CO.sub.2 microbubbles in the reservoir by constant pressure injection; [0035] by opening the injection well valve and injecting the mixed fluid into the fluid in the reservoir at 0.05 ml/min while keeping the reservoir pressure stable, placing a dense perforated plate 9 in the injection well shaft, and allowing the fluid to flow through the dense perforated plate at the bottom of the well to generate CO.sub.2 microbubbles containing SiO.sub.2 nanoparticles.

[0036] Firstly, SiO.sub.2 nanoparticles can improve the thermal properties, thermal conductivity, viscosity, and density of the fluid after mixing with CO.sub.2. When the mixed fluid is dissolved in saline water at the end of storage, the density difference between the mixed fluid and in-situ saline water is larger, thermal conductivity is enhanced, surface tension is reduced, etc. Using the improved fluid properties can effectively shorten the unstable onset time and mixing time of the convective mixing in the dissolution storage process, thereby enhancing dissolution.

[0037] In order to simplify the process of CO.sub.2 geological storage by nanoparticles mixed with SiO.sub.2, the influence of CO.sub.2 injection into nanoparticles fluid on the stability of fluid phase interface in the convective mixing process was analyzed in the laboratory by using a simulated fluid pair method to produce fluid with density difference (density and viscosity characteristics are selected according to geology fluid characteristics). The mass fractions (0 wt %, 0.1 wt %, 1 wt %) of the superhydrophilic SiO.sub.2 nanoparticles were added into the heavy fluid to study the optimal mixing ratio, and geology convection characteristics were studied by calculating dimensionless parameters. The interface stability improvement effect is shown in FIG. 2. Adding a certain concentration of fluid containing nanoparticles significantly improves the interfacial stability during convection, i.e. increases the sweep area and dissolution efficiency.

[0038] Secondly, in the data measured by micro-focus CT in the laboratory (40° C./10 MPa), a comparative experiment of displacement of saline water by ordinary CO.sub.2 and microbubble CO.sub.2 in 30 cm Berea core was carried out, and the experimental process was as follows: [0039] a) a Berea core was placed to fill the porous media and leak tested before the experiment. Connect the hose to the water jacket outside the container, keep the circulating fluorine oil at a high temperature, and use a vacuum pump to evacuate all the gases in the pipeline system; [0040] b) saline was slowly injected into the container from low pressure to 10 MPa, after the pressure is raised to the target value, kept standing for 5 h to ensure that all pore spaces are fully saturated saline, and performed presetting on the imaging parameters of CT; [0041] c) a back pressure pump was used to stabilize the system pressure to an experimental pressure of 10 MPa, starting data acquisition including a thermocouple and a pressure sensor, monitoring the temperature and pressure of the system, then opening an inlet valve, and using an air pump to inject normal CO.sub.2 or microbubble CO.sub.2 at a constant rate upwards (the microbubble CO.sub.2 is generated in situ by a perforated plate arranged on one side); [0042] d) the experimental procedure described above was repeated until regularly reliable core displacement data was obtained. This test analyzed 30 cm cores in three sections (each 10 cm in length).

[0043] In contrast, due to the characteristics of high specific surface area, high internal pressure, and high solubility of microbubble CO.sub.2, the contact area with saline water and dissolution rate increased significantly. In the low porosity zone, microbubble has a “preferential” selection mechanism. In the low porosity zone of sandstone (taking the second section of the core as an example), the sweep efficiency increased by 3.2-4.9% (Table 1), and the other sections increased.

TABLE-US-00001 TABLE 1 Comparison of CO.sub.2 saturation with injection volume fraction in each section of core CO.sub.2 Saturation (%) Volume fraction First Second Third of CO.sub.2 injected Bubble types section section section 0.15 Microbubbles 21.93 21.10  5.25 Ordinary bubbles 26.21 16.21  7.04 0.18 Microbubbles 23.04 23.32  8.31 Ordinary bubbles 28.00 18.54  9.65 2.50 Microbubbles 33.74 29.22 17.64 Ordinary bubbles 29.23 26.02 19.18

[0044] In conclusion, the combination of the two advantages can significantly enhance CO.sub.2 storage, dissolution, and mixing in the reservoir.

[0045] While the above examples are illustrative of specific embodiments of the present invention, it will be understood partial changes, substitutions and combinations of different methods performed by those skilled in the art within the scope of the technical solution shall be included in the scope of protection of the present invention.