Research history of (1) sedimentary physical simulation technology
1. The primary stage with observing and describing phenomena as the main research content.
At the end of 19, Deacon (1894) first observed and described the wave marks formed by sediment movement in a glass tank. Gilbert (19 14) conducted the flume experiment for the first time with sand of various particle sizes under different water flow intensities, and observed and described a series of deposition phenomena and structures in detail. The sand dunes he described at that time were later named asymmetric wave marks by other researchers. In the forties and fifties of the 20th century, Einstein (1950), Brooks (1965) and Berg Nordor (l954, 1966) also completed some groundbreaking experiments and established some basic methods of experimental sedimentology, but during this period, Simmons et al. (/kloc)
Simmons' experiment was carried out in an inclined circulating tank with a length of 150 feet, a width of 8 feet and a depth of 2 feet. The inclination of the water tank can be changed from 0 degree to 0.0 13 degree, and the flow rate can be changed from 2 to 22 feet 3/ sec ... In addition, Simons et al. also used a small inclined circulation tank with a length of 60 feet, a width of 2 feet and a depth of 2.5 feet, and the bottom slope of the small tank can be changed from 0 to 0.025. A special study was carried out in a small flume with a width of 2 feet to determine the important roles of viscosity, riverbed density and riverbed sorting in alluvial river flow.
Simons gives the particle size distribution of bed material used in 8-foot wide large tank and 2-foot wide small tank. Unless otherwise specified, the particle size distribution is expressed as sedimentation particle size (Colby, 1964). The distribution curve is based on the particle size analysis of a large number of randomly selected sand samples during and after the experimental study.
Simmons and Richardson completed a series of experiments from 1956 and 1965. The general step of each experiment is to circulate the given water-sediment mixed flow until the equilibrium flow condition is established. Simons defines equilibrium flow as a kind of flow, that is, the bed surface shape and bottom slope established by water flow in the whole flume are consistent with the characteristics of fluid flow and riverbed quality, except for the scope of import and export effect, that is, the time-average water surface slope of water flow is constant and parallel to the time-average riverbed bottom slope, and the concentration of riverbed quality flow is constant. Note that Simons et al. especially emphasize here that the concepts of balanced flow and constant uniform flow should not be confused, because for water-sediment balanced flow, the velocity can change at the same spatial point, or it can change from this spatial point to another spatial point. That is to say, the alluvial channel has no constant and uniform water flow except the flat bottom shape.
2. The rapid development period with the study of sedimentary mechanism as the main content.
From the 1960s to the 1980s, with the development of science and technology, the equipment and technology of simulation experiments were increasingly improved. The experimental content is not limited to the observation and description of deposition phenomena, but to the in-depth study of deposition mechanism.
Schumm( 1968, 197 1, 1977) and Williams studied the response of non-uniform bottom bed to flow change through flume experiment. Kalinsk (1987), Cher (1986), Fraser (1990), Bridge (198 1), Lide (1983). Susad of the Department of Earth and Planetary Sciences at the Massachusetts Institute of Technology and his colleague Bogewall (1973) used an inclined flume with a length of 6m, a width of 17cm and a depth of 30cm to conduct an experimental study from ripples to flat bed sand at the bottom. Then, in the time of 198 1 year, In cooperation with Canadian scholar Costero (198 1), the migration and hydraulic characteristics of the bottom flow pattern were studied by using well-sorted coarse sand in a tank with a length of 1 1.5m and a width of 0.92m. Southard( 197 1) and Ashley (1982) of the Department of Geological Sciences, New Jersey State University, USA, respectively simulated the sedimentary characteristics of creeping wave bedding with flume, and characterized the bed surface shape in an open channel uniform flow with water depth and average flow velocity. If dimensionless water depth, flow velocity and particle size (or these three variables themselves) are used,
There are three scholars worth mentioning in this period, namely J.B.Southand, J.R.L.Allen and J.L.Best. Because of their excellent work, the discipline of sedimentation has a solid foundation, and the research of sedimentation simulation has been given new vitality.
In the later stage of this stage, the content of simulation experiments has been very extensive, such as turbidity current simulation experiment, wind tunnel simulation experiment, storm simulation experiment and so on. These simulation experiments not only promote the development of sedimentology theory, but also have important practical significance for oil and gas exploration and development. For example, in the 1970s, the US Geological Survey began to study the characteristics of aeolian sand dunes with wind tunnel experiments, and further studied the seepage characteristics of sand layers, thus serving for oil recovery research. Wind tunnel experiments have also gone through a long process. In the 1940s and 1960s, wind tunnel experiments were mainly used to study the transport mechanism of sand and soil. Scholars include Nordor (19 14), Cepil and Chepil et al. (1963). In 1970s and 1980s, wind tunnel experiments have been used. Mckee et al. (197 1) used wind tunnel experiments to study various deformation structures on the leeward side of aeolian sand piles, and Fryberger et al. (198 1) further developed these deformation structures. This wind tunnel consists of a trough and a basin. This experiment focuses on the sedimentary characteristics of wave marks, slump and particle falling, and describes their forming conditions. Since 1960s, more and more attention has been paid to turbidity current simulation experiments, including Middleton (1976b, 1976, 1977), Riddell (1969) and Laval, etc. Although the simulation experiments in 1970s were in-depth, the mathematical model could not predict them. Although Selley (1979) and Allen (1976) put forward promising methods, they failed to predict the change of bottom shape in detail and accurately under controlled conditions.
During this period, other scholars engaged in experimental research include Rathbun et al. (1969), Williams (1967) and Rees (1966).
3. The simulation stage of lake basin sand body with the formation process and evolution law as the main research content.
From 1980s to 1990s, the study of sedimentary simulation entered the stage of lake basin sand body simulation with the formation process and evolution law as the main research contents. This stage not only pays attention to solving theoretical problems, but also pays attention to solving practical problems, which is combined with oil and gas exploration and development.
If we carefully study the experimental contents and foreign literature before the 1980s, it is not difficult to find that there are three main problems in the simulation experiment of sediment deposition before that: first, the experimental conditions, the previous flume experiments mostly used separated sand, ignoring the deposition of sediment and gravel; In addition, the uniform flow is mostly used in the experimental process, and the non-uniform flow is ignored; Most of them are carried out under stable and balanced conditions, ignoring the influence of unstable state, and these neglected factors are the common conditions for bed formation in natural environment. The second is the experimental content. In the past, flume experiments mainly simulated the transport and deposition of rivers and muddy water, but the simulation experiments of basin sedimentary system and sand body distribution and the quantitative prediction of sand body scale and extension were insufficient or basically not carried out. Third, the experimental purpose. Previous flume experiments mainly focused on the basic theory of sedimentology, but paid little attention to practical application. The reason is that there are many practical difficulties in doing this experiment. For example, the experiment of gravel deposition needs a wider, deeper and larger flow tank, the experiment of silt deposition needs stricter chemical and physical conditions, and the simulation experiment of great basin deposition system needs more advanced technical equipment and control system.
Since 1980s, in view of the serious deficiencies in the above aspects, experimental sedimentologists in various countries have adjusted their research ideas and overcome many difficulties. On the basis of keeping the original characteristics as much as possible, they either rebuilt the original laboratory structure on a large scale or re-established a large laboratory suitable for sand body simulation. The following three are worth mentioning.
1) Large-scale flowing water landform experimental device of Engineering Research Center of Colorado State University. The experimental device mainly simulates river sedimentation, and at the same time can simulate the influence of natural rainfall on river landform, as well as the deformation law of river bed and the formation mechanism of single sand body under different boundary conditions. Many American experimental sedimentologists have completed a series of experiments in this laboratory (Baridge,1993; Bryant, 1993), a visiting scholar in China, Professor Lai Zhiyun also completed the simulation experiment of the formation and evolution of the Bird's Foot Delta here.
2) Delft Simulation Laboratory of Swiss Federal Institute of Technology. The laboratory belongs to the Dutch River and Navigation Branch and is a relatively modern laboratory. In order to do applied basic research, a large water tank was specially built in this room. The water tank is made of reinforced concrete, and the observation part is made of steel frame with glass window. The total length of the water tank is 98m, the width is 2.5m, the length with glass window is 50m, and the measuring section is 30m, with the measuring sections of 0.3m and 1.5m respectively. The maximum sediment-free water depth is1m. Various control and measurement devices are installed around the sink, and the microcomputer and microprocessor can automatically obtain data and change various boundary conditions (such as flow). A track is arranged above the glass window part for the operation of the instrument vehicle.
Three profile indicators and a water level gauge are installed on the instrument truck, so that three longitudinal bed horizontal profiles can be measured, usually one is located in the middle of the tank and the other two are located at the tank wall width 1/6. The recorded data are collected, stored and calculated by a microcomputer, and finally the results are output. In 1983, Wijbenga, a project engineer, and Klaasen, a project consultant, used this device to study the change of bottom shape scale under the condition of unstable flow. After data processing, the relationship curves of water depth and time, sand pile height and time, sand pile length and time in each transition zone are automatically drawn, so as to determine the changing law of bottom shape scale. European scholars have completed the simulation experiments of the formation process of small alluvial fans and fan deltas here, and achieved some qualitative and semi-quantitative results.
3) Simulation Laboratory of University of Tsukuba, Japan. The laboratory is 343 meters long and several meters wide (the exact number is unknown). High degree of automation, relatively complete monitoring equipment and advanced analysis methods. A series of experiments on sediment transport and transformation by waves, river sedimentation system of saturated and unsaturated sediment transport, lake sedimentation and hydrodynamics have been completed successively, and a group of visiting researchers from all over the world regularly publish their research results.
From this point of view, the sedimentary simulation in 1980s and 1990s has two characteristics, one is the gradual change from qualitative description to semi-quantitative or quantitative research, and the other is the change from small-scale flume experiment to large-scale basin sedimentary system simulation.
(2) The development status of sedimentary physical simulation technology in China.
1. Basic survey of sedimentary physical simulation research in China
Before 1985, flume laboratories in China were mainly concentrated in relevant universities and research units in water conservancy, hydropower and geography departments, engaged in experimental research on sediment movement law, river evolution and large-scale water conservancy and hydropower projects. In the late 1970s, Changchun Institute of Geology built the first small glass tank for sedimentology research. This pool is 6 meters long, 80 centimeters high and 25 centimeters wide. It mainly studies the formation and development of the bottom shape. In the 1980s, the Institute of Geology of the Chinese Academy of Sciences also did some research work with its own small sink. These are the only two flumes in China that are mainly used for sedimentology research. Although there is still a certain gap between the research content, depth and breadth and the international level, it has taken the first step for the development of sedimentary simulation experiments in China.
With the development of sedimentology theory and the need that science and technology must be transformed into productive forces, the situation of oil and gas exploration and development in China puts forward some practical problems that need to be solved urgently for quantitative sedimentology, reservoir sedimentology and sedimentary simulation experiments. Over the years, there have been some controversial issues in the study of continental rift lake basins in eastern China, such as the steep slope sedimentary system, the formation conditions and distribution laws of fan deltas and underwater fans, and the differences between rift lake basins and depressed lake basins, which need to be verified by sedimentary simulation experiments. The shape, scale and extension direction of different types of single sand layers also need to be reasonably predicted through sedimentary simulation experiments. Therefore, after 1985, many sedimentologists actively called for the establishment of a sedimentary simulation laboratory in China according to the current development trend of sedimentology in the world and the production practice and future development needs of oil and gas exploration and development in China. Experts believe that the laboratory should focus on simulating sedimentary sand bodies in continental basins, focusing on reservoir research, solving practical problems in production, and taking the distribution of sand bodies in continental lake basins, quantitatively predicting the scale and performance of various sand bodies, and improving the success rate of exploration and development benefits as the main goals; In addition, the establishment of the laboratory should also take into account the basic research of sedimentology, provide conditions for personnel training and foreign exchanges, promote the development of sedimentology theory in China, and gradually develop into a national sedimentary simulation laboratory. The establishment of this laboratory is also an important means to transform theoretical research into productivity, which is in line with the world trend of paying attention to reservoirs in oil and gas exploration and development, so the key laboratory of sedimentary simulation of PetroChina came into being.
2.2 Introduction of experimental device. Key Laboratory of Sedimentary Simulation of China Petroleum Group.
(1) factory scale
The experimental device of the key laboratory of sedimentary simulation of China Petroleum and Natural Gas Group Company is 16m long, 6m wide, 0.8m deep and 2.2m high from the ground. There are 1 water inlets (outlets) in the front of the lake basin, two on both sides to simulate the composite sedimentary system, and one at the tail. The whole lake basin is poured with concrete to ensure no leakage. A circular waterway surrounds the lake basin. The roof of the lake basin adopts channel steel asbestos tile structure, which can ensure that the experimental process is not affected by weather changes and is conducive to lighting.
(2) Movable bottom plate and control system
The raised floor system is an important part of the laboratory. According to the actual situation of the fault basin in the east of China, without the rise and fall of the basement, the fault system can not be generated, the tectonic movement can not be simulated, and the control effect of the structure on the sedimentation can not be simulated, so the function and role of the laboratory will be greatly reduced. Therefore, it is necessary to set up a raised floor in the lake basin area.
The raised floor area of the laboratory consists of four raised floors, each with an area of 2.5m×2.5m=6.25m2, and the raised floor can be tilted synchronously, asynchronously, synchronously and asynchronously from left to right. The slope of the active area is arc tangent 0.35, the rising range is 10cm, the falling range is 35cm, and the synchronization error is less than 2 mm ... Each bottom plate is supported by four pillars, which is watertight and sand-tight, flexible and reliable, and basically meets the experimental requirements.
The control of the raised floor is realized by 16 stepping motor, 16 reducer, four driving power supplies, computer and electronic components. The number of pulses output by the computer controls the rotation of the stepping motor and converts it into the lifting of the movable floor. The biggest advantage of stepping motor is that it can accurately control the motion state, and the vertical speed can be adjusted as needed, thus meeting the requirements of natural crustal motion characteristics.
(3) Detection of bridge drive positioning system
In order to effectively monitor the sand body deposition process and facilitate sand body detection, a detection bridge with a span of 6m and a width of 1m has been installed on the lake basin. The measuring bridge has the following functions: ① The measuring bridge can move freely and position itself automatically in the longitudinal range of 16m, and the mechanical error between the guide rail and the measuring bridge is less than 2mm, which meets the requirements of high-precision sand body shape detection; ② A console is set at one end of the measuring bridge to control the automatic positioning and detection of the measuring bridge; ③ A set of CCD laser grating detection system is set on the measuring bridge, and the whole system can move horizontally for 6m for superposition detection, thus improving the measurement accuracy; ④ A detection trolley is set in the middle of the bridge, which can move within 6m span and scan the sand body deposition process.
3. Brief introduction of sedimentology flume laboratory of Youshi University (East China) in China.
Fault basin is a typical intracontinental rift basin formed in eastern China since Mesozoic and Cenozoic, and it is rich in oil and gas resources. With the shift of oil and gas exploration focus to stratigraphic and lithologic reservoirs, turbidite sand bodies in fault basins have also become an important field of subtle oil and gas reservoir exploration. However, the formation and distribution of turbidite sand bodies in fault basins are influenced by many factors, and the formation process is sudden. Therefore, the understanding of turbidite sand bodies is still in the stage of qualitative analysis through seismic and drilling data, and the understanding of its genesis and dynamic mechanism is not deep, and there is no effective prediction method. Physical deposition simulation can reproduce the formation process, development and evolution law of turbidite sand bodies, thus establishing a fluid flow model, predicting the shape and distribution law of sand bodies, and discussing the controlling factors of turbidite sand bodies. The sedimentology flume laboratory of China Youshi University (East China) was established under this premise.
China Youshi University (East China) sedimentology flume laboratory was established in 2002. It consists of three parts: experimental water tank, sand box and built-in bottom template. After many transformations, the experimental simulation of gravel rock mass, fan delta, slump turbidite and seismic turbidite on the steep slope of delta front has been successfully carried out. The inner wall of the experimental flume is 5m long, 2m wide and 1m high. The side wall of the long axis is made of glass, which is convenient for observation and photography. The side wall and bottom surface of the short axis are cement walls with a thickness of 25 cm. The whole sink is placed on a 40 cm high base. One end of the side wall of the short shaft is provided with a water inlet and the other end is provided with a water outlet. The water inlet is externally connected with a sand adding tank, and sediment and water are simultaneously injected into the water tank from the sand adding tank. A movable metal bracket is placed in the sink, and the surface of the bracket is covered with an iron plate to simulate the original bottom shape. The inclination of the bottom shape can be adjusted by lifting the control lever. A metal tube is fixed on the support as the trigger point of the seismic source, and the metal tube is struck by external force to simulate the occurrence of vibration (Figure 10- 1, Figure 10-2).
Fig. 10- 1 cross-sectional view of tank simulation experimental device (unit: cm)
(3) Development trend of sedimentary simulation research.
After 1990s, there have been some new developments and trends in sedimentary physical simulation technology, which can be summarized as the following five aspects.
1. The increasing combination of physical simulation and numerical simulation.
After a century of development, a number of excellent academic achievements have been made in sedimentary simulation research. However, these achievements mainly focus on physical simulation research. With the wide application of computer in geosciences, the numerical simulation of clastic sand body deposition process is gradually developing into an important branch of sedimentary simulation technology, and it is increasingly infiltrated with physical simulation, which complement each other, depend on each other and promote each other. The multi-level combination of physical simulation and numerical simulation of clastic deposition process is an important development direction of deposition simulation technology. Through the combination of physical simulation and numerical simulation, the research of numerical simulation can get rid of the interference of human factors. Physical simulation provides quantitative parameters through Cheng Kewei computer numerical simulation, which makes the numerical simulation have a reliable physical basis and closer to the actual production of oil fields, thus guiding oil and gas exploration and development more effectively.
Figure 10-2 perspective view of tank simulation experiment device (unit: cm)
Numerical simulation has gradually developed into an important branch of sedimentary simulation technology because it has some outstanding advantages compared with physical simulation, which are embodied in the following four aspects.
1) All conditions of numerical simulation are given by numerical values, which are not limited by scale and experimental conditions, and the boundary conditions of wells can be strictly controlled to change with time;
2) Numerical simulation is universal, and it can be applied to different practical problems as long as appropriate application software is developed, so numerical simulation has the characteristics of high efficiency;
3) Numerical simulation also has ideal anti-interference performance, and repeated simulation can get exactly the same result, which is difficult for physical simulation to achieve;
4) With the rapid upgrade of computers, the functions are constantly strengthened, and the cost is constantly reduced, which is relatively cheap.
2. It provides a new method for reservoir prediction in early exploration.
At the initial stage of exploration in a basin or block, there are few drilling wells and appraisal wells, but there are often more detailed seismic data. Through the interpretation of seismic data, the boundary types and conditions of basins or blocks and the types of sedimentary systems can be determined. Combined with drilling data, we can establish a conceptual geological model, extract the main controlling factors and establish a physical model. Under the guidance of physical model, physical simulation experiments can be carried out. Using the parameters provided by physical simulation, numerical simulation research can be carried out, thus accurately predicting the distribution law of sedimentary system and the distribution of high-quality reservoirs in the basin, and providing basis for the selection of exploration targets. This is an important aspect of sedimentary simulation research serving oil and gas exploration and development, and it is also an important trend of sedimentary simulation technology development.
3. It provides a new technique for describing sandstone heterogeneity in the later stage of development.
There are a lot of static and dynamic data in the later stage of oilfield development. We can use rich oilfield development and production data to establish a fine geological model, and carry out simulation experiments according to sand layer groups or single sand layers, and compare the experimental results with the existing static and dynamic data. If the experimental results are highly consistent with the characteristics of sand bodies reflected by static and dynamic data of well points, the experimental results can be considered reliable. The characteristics of prototype sand bodies between well points can be described by the characteristics of experimental sand bodies (model sand bodies) corresponding to well points, so as to quantitatively predict the distribution and heterogeneity of reservoirs between wells and the distribution law of remaining oil, which is another important trend in the development of sedimentary simulation technology.
4. Combined with the analysis method of structural elements of reservoir buildings.
The essence of the analysis method of reservoir configuration elements is the hierarchy of reservoirs, an important feature of the reservoir-forming process and a universal law of geological phenomena. Each level has two elements, namely, level interface and level entity (Lin Kexiang et al., 1995). The main advantage of sedimentary simulation experiment is that it can describe the shape, fluctuation, continuity, distribution range and thickness change of these interfaces in detail according to the time unit of formation process, and confirm with the results of modern sedimentation and outcrop investigation, establish the geological knowledge base and reservoir parameter model of reservoir prediction, and put forward the controlling factors of sand body formation and distribution and the geological law of evolution, which is not available in other research methods. In recent years, some literatures at home and abroad are trying to explore the possibility of combining them (Miall, 1985, 1988), and some innovative achievements have been made, forming a new trend in the development of sedimentary simulation technology.
5. Combining flow unit division and high-resolution sequence stratigraphy research.
In the later stage of oil and gas field development, an important means to study the distribution law of remaining oil is to re-divide and identify flow units. In this process, the study of high-resolution sequence is the foundation, and sedimentary simulation technology has also played a very important role in this research in recent years. Because the key of high-resolution sequence stratigraphy research is the fine division of isochronous interface, and sedimentary simulation technology has this advantage, both physical simulation experiment and numerical simulation research of sand body formation process can provide time interface at any stage, reservoir distribution and internal structure characteristics at this time period, and point out reservoir evolution trend and development characteristics in the next time period. Therefore, the combination of sedimentary simulation technology and high-resolution sequence stratigraphy research will surely show great vitality in subdividing flow units and predicting remaining oil. Many scholars at home and abroad are carrying out this work in different ways, and there is reason to believe that this method will develop into a practical technology to predict the distribution of remaining oil in the next few years.
To sum up, after entering the 2 1 century, in addition to maintaining the advantages of its original sedimentology theory research, the main development trend is to combine with geological research methods such as computers to form a comprehensive practical technology for predicting reservoir development and evolution trend.