1. Analytic Hierarchy Process
Analytic Hierarchy Process (AHP) is a practical multi-scheme or multi-objective decision-making method put forward by Professor T.L.Saaty, an American logistics scientist, in 1970s. It reasonably combines qualitative and quantitative decision-making, and quantifies the decision-making process according to the laws of thinking and psychology, especially for complex problems that are difficult to be fully quantitatively analyzed. Firstly, the problem to be analyzed is hierarchical, that is, according to the nature of the problem and the overall goal to be achieved, the problem is decomposed into different components, and the factors are aggregated and combined at different levels according to the mutual relationship and subordinate relationship between them. The formation of a multi-level analytical structure model ultimately boils down to the relative importance of the lowest level (programs, measures, indicators, etc.). ) relative to the highest level (overall goal) or relative priority order.
The advantages of analytic hierarchy process are: (1) simple and clear, which provides a hierarchical framework and is convenient for sorting out ideas; (2) Contrast calibration increases the objectivity of judgment; (3) The combination of qualitative judgment and quantitative reasoning enhances the scientificity and practicability.
However, AHP also has obvious shortcomings: (1) AHP has strong objectivity, and when there are many factors (more than 9), the workload of scaling is too heavy, which is easy to arouse the resentment of scaling experts and confuse judgment; (2) Analytic Hierarchy Process also has fatal shortcomings. It can only choose the best strategy among the given strategies, but can't give a new strategy. (The index system used in AHP needs the support of expert system. If the given index is unreasonable, the result will be inaccurate; (4) When constructing the judgment matrix, due to the limitation of data, information and the level of analysts, it is difficult to use "omitted" accurately. Important ","more important "and" extreme! Important "and other vague words to express the relationship between the two elements, the evaluation results are greatly influenced by human subjective factors, and the consistency of the judgment matrix is not ideal.
Analytic Hierarchy Process (AHP) can be used for the location of CO2 geological storage, which is mainly determined by the multi-factor nature of geological storage location (see Chapter 6, Section 4, GIS implementation of multi-factor sorting location technology). It can be seen from the structure table of factor weight distribution that factors are divided into index layer A, index sublayer B, index sublayer C and specific index layer D according to their characteristics. When dividing levels, we should consider the ownership relationship of factors. In addition, the factors with one-vote veto should be paid attention to and considered separately in the evaluation, and should not be included in the weight calculation of factors at the same level.
2. Center of gravity method
The center of gravity method is the most commonly used method for single facility location, such as logistics distribution center, oil depot location, warehouse, tool and equipment storage point, parking lot, etc. It is also often used to exclude some unsuitable substitutes. The barycenter method is a static method, which regards the demand points as an object system distributed on a certain plane, and regards the demand and resources of each point as the weight of the object respectively. The barycenter point of the object system will be the best setting point of the location space.
The shortest path analysis in GIS is a common method of gravity method.
The advantages of barycenter method are: (1) simple calculation, easy data collection and easy understanding; (2) When locating a single facility, it is simple and easy to apply the analysis method;
The disadvantages of the center of gravity method are: (1) too many degrees of freedom, resulting in a large amount of calculation; (2) The optimal position calculated by iterative method is often difficult to find; (3) For complex site selection problems, the center of gravity method is often difficult to use, and other more comprehensive analysis techniques are usually needed.
If the distribution of carbon sources is clear and the geological conditions of the target area are similar, this method can be used to find the best transportation route of CO2.
3. Network coverage model
The network coverage model can be used in many aspects, such as mobile base station coverage, service network coverage, and the location of the largest coverage area of oil depot. It can solve the problem of how to determine a set of service facilities to meet the needs of some demand points when the demand is known, that is, to determine the minimum number and suitable location of service facilities. It can be divided into two different models: set coverage model (covering all demand points with the least number of facilities) and maximum coverage model (covering as many demand points as possible with a given number of facilities). Heuristic algorithm is commonly used in the former; The latter usually uses greedy algorithm. Mobile base station coverage and other site selection can be based on the map in GIS, generate orthographic three-dimensional images according to digital topographic maps, or browse three-dimensionally to quickly grasp the topographic characteristics of the whole area, and at the same time, refer to the existing sites, residential areas and road locations to preliminarily infer several more reasonable site locations. After the initial selection of some address points, DEM analysis method can be used to optimize the site selection scheme, and the visible areas of several candidate points can be calculated by simultaneous analysis in GIS, and the visible areas can be superimposed on the map to measure whether the areas of interest to decision makers can be covered.
Considering the factors such as carbon source (demand point), site storage scale (maximum coverage model), traffic conditions or road location, this method can be used to determine the site scope under the condition that the geological conditions of site selection are clear, which provides economic basis for the layout of water injection wells.
4. Simulation method
Simulation method is to express practical problems with mathematical methods and logical relations, establish mathematical logic model, run the simulation model with a computer, simulate the running state of a time system and its changing process with time, describe or analyze the dynamic behavior of the system from one state to another according to certain operating rules, and obtain the output parameters and basic characteristics of the simulation system through observation and statistics of the simulated running process, so as to estimate and infer the real parameters and real performance of the actual system.
The advantages of simulation method are: (1) intuitive and clear; (2) Compared with the analytical method, the research results are closer to the actual situation.
Its disadvantages are as follows: (1) The reliability and validity of the model are relatively strict; (2) Some simulation systems are sensitive to the initial deviation, which often makes the simulation results deviate greatly from the actual results; (3) Designers are required to have rich experience and high analytical ability, and face relatively complex simulation systems.
The simulation method is mainly used for the site selection of CO2 geological storage, such as specific single-point site selection and construction site selection of water injection wells. Other numerical simulation methods should be combined in concrete use.
Of course, the application of spatial positioning method is not a simple application of a single method, but a combination of several methods. In addition, fuzzy clustering method, genetic algorithm and other algorithms can be used for mathematical modeling.