(Wuxi Institute of Experimental Geology, China Petrochemical Company, Wuxi, Jiangsu 2 14 15 1)
TSM basin simulation is a numerical simulation guided by the thought of 3T (environment) -4S (action) -4M (response) basin system, which integrates the system network from basin to trap according to the four historical systems of burial, heating, hydrocarbon generation and migration and accumulation. In the application of Subei basin, the burial history of two-dimensional kinematic fault-fault depression prototype superposition is reproduced, and the change process of superimposed thermal field of fault depression is fitted in combination with the change of tectonic-thermal system in different periods, which provides the prototype control boundary conditions for the dynamic change of oil and gas P (pressure), V (volume) and T (temperature) for the basin, so that the system can generate and expel hydrocarbons reasonably until. Through the fitting of known oil and gas fields, the location of unknown possible oil and gas accumulation zones is predicted and verified in later exploration. The application shows that TSM simulation embodies the research direction of systematization, dynamics and quantification of petroliferous basins, and emphasizes that the study of geological conceptual model and the analysis of the juxtaposition and superposition relationship of prototype basins under different tectonic-thermal systems are important prerequisites for simulation implementation. The simulation method has the functions of testing the geological conceptual model and revealing the evolution process of the basin. The ultimate goal is to predict the quantity and distribution of oil and gas resources, and make a rolling evaluation with the exploration process to achieve the purpose of guiding exploration.
Guiding ideology of 1 TSM basin simulation research
Basin research is a complex system engineering. In order to understand the internal relations of various things in the basin system, basin research is developing rapidly in three directions: systematization, quantification and dynamics. Zhu Xia (1982) put forward TSM working procedure for basin research in his paper "Formation and Development Mechanism of Oil-bearing Basin in China and Its Control on Oil-gas Generation, Migration and Accumulation" [1]. The program shows that the three major elements of global structure (3T) control the formation of basins in different geological historical stages, and different mechanisms produce different prototype basins. The whole basin is the juxtaposition and superposition of prototype basins. Because the basin itself is a prototype combination of different formation and evolution mechanisms, the four major geological factors (4S) and the four major oil and gas response factors (4M) in the basin have their own characteristics. The systematicness of basin research makes basin research involve many disciplines, and a huge chain network is formed among various parameters related to the genesis of oil and gas basins, and the change of almost any factor will affect the change of system network. In this network, all elements are integrated according to the quantitative model relationship formed by known geological facts, that is, they are interrelated and locked in the whole network matching, thus revealing the oil and gas accumulation effect. Therefore, it is required to reasonably approximate or repeatedly predict the location and quantity of oil and gas in the process of real-time geological history recovery and exploration and inspection, so as to improve the exploration hit rate. As Zhu Xia (1985) pointed out, the research on such a system should be carried out according to the procedure of theoretical modeling, case verification and dynamic simulation. Therefore, TSM program organically combines the systematicness and dynamics of basin research, and provides a feasible guiding ideology for quantitative analysis and simulation of basins.
2 the concept and basic methods of simulation
Basin simulation is an extremely important method for basin comprehensive research. The so-called simulation is a kind of simulation technology. Dynamic simulation means that it can simulate the change of the research object with time; It reflects the dynamic changes of the basin system, which also means that the simulation results are dynamic, and the understanding of the basin can be continuously revised with the improvement of exploration degree; It also means that the simulation method is dynamic, and the new exploration results test the simulation prediction and provide new information, which can be used for re-simulation, repeated prediction, continuous fidelity and continuous guidance to practice. However, the deterministic simulation method needs strict logical relationship or functional relationship to describe the object, so it highlights the combination of physical and chemical theorems and geological principles or laws, rather than quantitative prediction based on descriptive or statistical analysis. That is, trying to express the relationship between geological process (S) and oil-gas response (M) by physical or chemical mathematical logic method, dynamically simulating the quantity and occurrence position of oil and gas, and then comprehensively reflecting the essential characteristics of oil-gas formation and evolution process has become an important means to solve the research of dynamic system.
For a long time, the controlling factors of oil and gas accumulation that we know are basically static geological systems. It is probably arbitrary to construct and interpret with static geological elements [2](Magara, 1986). Therefore, the value of simulation, especially dynamic system simulation, should not be evaluated by absolute terms such as "yes" or "no", but by "reasonable" or "unreasonable". Therefore, understanding the geological system is still the key to improve the feasibility of simulation and prediction. Once the forecasting ability is expanded, the exploration risk is reduced.
Basin simulation generally goes through geological conceptual model, mathematical model and computer realization. The so-called conceptual model is the geological concept formed in people's minds. Through long-term geological research, the understanding of geological problems has improved from descriptive to regular, from qualitative to quantitative, thus forming a geological conceptual model that can be transformed into a mathematical model. In fact, a lot of geological observation and research is to get such knowledge to guide the production practice of oil exploration. In other words, quantitative basin simulation research can only be carried out if geological research goes deep to a certain extent. Mathematical model is to express geological laws with mathematical formulas, abstract geological facts into data, transform geological concepts into mathematical physical concepts, and then realize comprehensive computer realization by solving problems such as data format, calculation method, program organization, input and output. The simulation system is mainly composed of database subsystem, simulation calculation subsystem, display and drawing subsystem. The database subsystem includes original database, parameter database and result database; The simulation calculation subsystem contains software libraries of various model simulation methods, which can be flexibly accessed according to the actual situation and combined in series to form a suitable system; The display and drawing subsystem is mainly used to display output data, graphs and reports. It is a service subsystem, which mainly includes some specially developed and general display software packages.
3 basin dynamic system simulation model
3. 1 general model for evolution simulation of subsidence basin
Basin simulation system is the final comprehensive expression of geological model and mathematical model. The mathematical dynamic model of oil and gas basin involves a wide range of geological models, including the geotectonic environment model of basin formation and development, the model of basin subsidence and sedimentation-tectonism, the model of oil and gas generation and accumulation conditions, and the compilation of logical relations among these models. To realize this huge and complex simulation of oil and gas basins, we need a geological model library that can be used for simulation and can represent various prototype basins, and the geological models in the library are constantly supplemented and updated with the in-depth study of oil and gas basins. Therefore, according to the previous research work, we put forward and established the dynamic simulation model base of TSM basin exploration and evaluation system (figure 1), which needs to be further developed and enriched in the future research work.
Figure 1 TSM Basin Dynamic Simulation Model Block Diagram
(The semi-circular box outside the box indicates the main calculation parameters or functional relationships)
It can be seen from the model block diagram that the subsidence models of different prototype basins can be established from the geological process of the basin, and the burial history and thermal history can be restored to reflect the geological process of basin occurrence and development, and indicate the formation temperature and pressure at any time and the related factors affecting oil and gas conditions. They are "linked" with the process of describing oil and gas generation (hydrocarbon generation history), migration and trap (migration and accumulation history), which can establish a series of relationships between geological processes and oil and gas response, thus achieving the purpose of predicting oil and gas.
3.2 geological process simulation model of subsidence basin
The "4S" simulation of the basin is an important part of the whole dynamic system, which reveals the subsidence mode and sedimentary characteristics of the oil-bearing basin in a certain stress environment, provides boundary conditions for the prototype basin to control the dynamic changes of oil and gas P (pressure), V (volume) and T (temperature), and is the premise for graduate students to study hydrocarbon history, hydrocarbon expulsion history and migration and accumulation history.
A large number of basin analysis results show that any basin prototype is controlled by the tectonic-thermal system at that time, and under the action of the stress field formed by it, a certain scale of main fault system (tension and compression) is formed, which controls deformation or basement deflection (depression), and makes the basin settle, forming a certain settlement space, accompanied by sedimentation and stratum deformation. From the characteristics of burial depth, compaction and structure reflected by the prototype geological process of the basin, we can see the style and features of a prototype basin. Different regions have different tectonic-thermal systems, so there are different basin styles and different geological process simulation systems. Zhu Xia [3]( 1986) and Zhang Yuchang [4]( 1997) think that it is globally comparable to divide oil and gas basins from prototype basins formed under a single dynamic mechanism. Therefore, we focus on the study and establishment of geological models of settlement process under a single dynamic mechanism, such as extensional fault depression, uniform extension, compressive fold and other models listed in figure 1. According to the concept of juxtaposition and superposition of the prototype basin, the subsidence history, sedimentation history and erosion history of the basin are simulated by relying on the specific geological conceptual model of the study area. During the "Seventh Five-Year Plan", "Eighth Five-Year Plan" and "Ninth Five-Year Plan", we made one-dimensional and two-dimensional simulations in Yancheng sag, Qintong sag, Qutang Bao Li area, Mamusu sag in Badain Jilin basin and Changling sag in Songliao basin respectively.
3.3 Simulation model of oil-gas response in subsidence basin
The evolution process of oil and gas generation, migration and accumulation in subsidence basins is a difficult point in petroleum geology research. After nearly 20 years of efforts, the development from hydrocarbon generation to migration has also changed from qualitative research to quantitative development. Especially in recent years, many scholars at home and abroad have put forward a large number of models through a lot of research on the mechanism and combination of oil and gas accumulation (Figure 1).
At present, the basic concepts of our model take into account the development in recent years. Because there is a big difference between the model and the actual evolution of the basin, the fundamental problem lies in the insufficiency and accuracy of the parameters provided by the geological model. The solution of the problem lies in establishing several basic models that can be well quantified, and then calculating, fitting and comparing with different assumptions according to the geological conceptual model, and obtaining knowledge feedback through exploration and inspection, thus promoting "rolling" simulation fitting, and finally getting more reasonable simulation results of hydrocarbon generation history, hydrocarbon expulsion history and migration and accumulation history, so as to serve oil and gas evaluation and exploration.
Application of simulation technology in evaluation of oil and gas resources in No.4 basin
Because the research of modern petroleum geology is systematic, dynamic and quantitative, computers have become an important auxiliary tool. Among them, the striking research method is to use computer to dynamically simulate geological process, so as to test the accuracy of geological concept, reveal the relationship between geological historical process and oil generation, migration and accumulation events, and finally quantitatively determine the amount and location of oil and gas resources, so as to achieve the purpose of predicting the unknown and evaluating oil and gas. According to the established model system, we have made a series of applications in northern Jiangsu, Badain Jaran, East China Sea and Songliao Basin, and gained some understanding.
4. 1 test geological conceptual model
The simulation results of oil and gas basin can reflect the subsidence, oil generation and migration and accumulation of the basin, and can test the knowledge gained from oil and gas exploration. For example, many years' exploration shows that Qintong sag is an extensional fault depression formed on the basis of Cretaceous depression, which has experienced the fault depressions of Taizhou Formation-Funing Formation, Dai Nan Formation-Sanduo Formation and Yancheng Formation-Dongtai Formation. In addition, the Dai Nan movement and Triassic movement in this area caused two denudation. The simulation results of subsidence history show that the Cenozoic basin in Qintong sag experienced the geological evolution process of fault depression, and the unbalanced tension tensor in each period not only reflected the existence of two faults, but also coincided with the scale of tension depression and sedimentary environment revealed by exploration. Similarly, the structural profile formed in another compressional environment, using the balanced profile to test the geological interpretation has played a reasonable limit, making the geological understanding (model) closer to reality.
4.2 Reveal the basin evolution process
At present, the data obtained from oil and gas basin exploration and actual observation are static data, which reflects the static situation of the current geological system. However, the process control of oil and gas generation and migration is a dynamic and time-varying geological system element, but their direct evidence no longer exists. Therefore, the historical evolution data can only be revealed by basin simulation. It is more reasonable to simulate the geological evolution process according to the physical and chemical laws, which can avoid arbitrary interpretation. The simulation work in northern Jiangsu, Badain Jilin and other areas has dynamically revealed the evolution process of burial history, thermal history, hydrocarbon generation history and migration and accumulation history, and expressed it through a large number of maps such as burial history evolution map, paleogeothermal evolution map, hydrocarbon generation maturity map, hydrocarbon generation isoline map, hydrocarbon expulsion volume and location map, water head isoline map of each layer in each period, oil and gas migration trend map, etc., so that people can dynamically and intuitively understand the four-dimensional space of the basin.
Fig. 2 migration and accumulation history of Yancheng sag
[Simplified by Zhang Yuchang et al. (1989)] (a) and (b) are hydrocarbon migration and accumulation when the third member of Funing Formation (Ef3) was deposited in Yancheng Formation (Ny) and now; (c) and (d) are oil and gas migration and accumulation of the first member of Funing Formation (Ef 1) reservoir deposited in Yancheng Formation (Ny) and present time respectively; (e), (f) and (g) are Taizhou Formation reservoirs of Dai Nan Formation.
Sedimentary period and present oil and gas migration and accumulation in Yancheng Formation.
1. hydrocarbon receiver location; 2. Possible gathering areas; 3. The direction of secondary migration; 4. Possible secondary migration direction; 5. Equal water head line
4.3 Prediction of oil and gas resources
The simulation results show the change of the subsidence center of the basin, and the hydrocarbon generation period, peak period and hydrocarbon expulsion period of different source layers well reflect the organic matching relationship with the structural formation period, so as to predict the direction of oil and gas migration and accumulation, possible trap positions and types (Figures 2 and 3). Of course, all the simulation results will be tested in the exploration. With the improvement of the model and the increase of parameters, simulation can realize "rolling" evaluation and continuously guide exploration and production.
Schematic diagram of oil and gas prediction in the third member of Paleogene Funing Formation in Qintong Depression.
(Xu Xuhui et al., 1997)[5]
1. Primary normal fault; 2. Secondary normal fault; 3. Tertiary normal fault; 4. Isobathymetric line/meter; 5. Possible migration direction of oil and gas; 6. Primary oil and gas prediction area; 7. Secondary field of oil and gas prediction; 8.22Ma high oil accumulation area (> 0.12m); 9.22 mA high with 8 heads (> 0.6m)
refer to
Zhu Xia. Formation and development mechanism of China petroliferous basin and its control on oil and gas generation, migration and accumulation [A]. On plate tectonics and analysis of oil and gas basins [C]. Shanghai: Tongji University Press, 1982.
[2] Magala and Ginger. Geological model of polonium trap [M]. Elsevier Applied Science Press, 1986.
Zhu Xia. On the structure of China petroliferous basin [M]. Beijing: Petroleum Industry Press, 1986.
Zhang Yuchang. Prototype analysis of China petroliferous basin [M]. Nanjing: Nanjing University Press, 1997.
Xu Xuhui, Jiang Xingge, Zhu Jianhui, et al. TSM Basin Simulation-Application in Qintong Depression in Northern Jiangsu [M]. Beijing: Geological Publishing House, 1997.
[6] Magala and Ginger. Compaction and fluid migration [M]. Elsevier applied science press, 1987.