1 Regional Overview
Five oil and gas fields have been discovered in the abdomen of the Junggar Basin, Luliang, Shixi, Chenan, Mobei and Mosuo Bay, and six sets of reservoirs with the Jurassic Sangonghe Formation (J1s) and the Xishan Kiln Formation (J2x) as the main oil-bearing system and three sets of hydrocarbon source layers of the Lower Permian Fengcheng Formation, the Lower Wuerhe Formation of the Upper Permian and the Jurassic Coal System have been found, and the views of “source control theory” and “Liang aggregation theory” of oil and gas distribution were proposed [1] . In the past five years, its new proven oil and gas reserves have accounted for 60% of the new proven reserves in the whole basin, and it has become a key area for increasing reserves and production in Xinjiang oilfield.
Basal faults and capsular faults develop in the abdominal area of the Junggar Basin, and the previous exploration and research results show that the faults and disintegration surfaces in this area are good channels for oil and gas transport. However, the fine structural characteristics of the abdominal region are limited by the data and research methods, and there are multiple solutions, and its structural characteristics and evolutionary characteristics are not well understood. Therefore, this paper will use PETREL software to model the 3D solid in the belly area of the Junggar Basin, restore the characteristics of underground faults and unintegrated surfaces, and then predict the favorable area more accurately, which provides a new basis for oil and gas exploration [2] .
2. Data Entry
2.1. Seismic Data Body Input
Open the Petrel software, click on the blank space of the explorer, and select Import File. Select the location of the file, select the target file in.sgy format, select SGY-Y seismic data as the file type, and finally determine the import to successfully import the seismic data body, which is the basic condition for the establishment of geological models.
2.2. Wellhead File Input
The content of the file includes the basic information of the well, such as well name, well type, well depth, and well coordinates:
The import steps are: click the blank space of Software Explorer, select Import File, select the target well head file, and the import format is well head. After confirming the import, click select CRS to select the Coordinate reference system (CRS) corresponding to the target area and click OK to perform the next step of data processing, and determine the type and order of input data according to the order of the original data in the data column, the original data is visible in this step, which is convenient for users to choose the format of the imported data. After completing the above steps, the well location data is successfully imported into petrel, and you can select the well in the explorer to display the 3D distribution of the well position in the visual interface, and you can directly see the distribution of the well position (Figure 1).
2.3. Entering Data Input
Layer data includes: Inline, Corssline, X, Y, Z coordinates, and layer names.
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Figure 1. Three-dimensional well distribution interface in the abdomen of the Junggar Basin.
Click on the blank area of the resource manager, select the Import File, select the target file, the file type is selected according to the original file format. The selection type of this article is Kingdom 3D Interpretation Lines (ASCII) to confirm the opening file. In the next step, select the data body and data type (time or depth) corresponding to the introduction of layer data (Figure 2).
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Figure 2. Data Display at the 5th region of the Basin of the Basin in the Basin of the Basin.
2.4. Introduction to Tables Data
Fault data includes: X, Y, Z coordinates, fault name, fault point and other information.
Click the blank area of the PETREL resource manager, select Import File, select the target file, the file type is selected according to the original file format. The selection type of this article is Seisworks FaultSticks (ASCII), and click to open. Enter the data columns corresponding to X, Y, Z value and the corresponding data of Point Number, Name, and click OK to successfully import the broken data. In the next step, the break can be successfully displayed on the 3D visual window. As shown in Figure 3, the nature and direction of the breakthrough in the abdomen area are complex and changeable.
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Figure 3. Three-dimensional display of fault distribution in the abdominal area of Junggar Basin.
3. Establish a Construction Model
The structural model is an important basis for 3D geological modeling, and the skeletal model of the entire 3D geological model can reflect the distribution form and distribution outline of the entire work area in 3D space. Only when the correct construction model is established can the phase model and attribute model be constructed. A construction model generally consists of two parts, namely a fault model and a plane model.
3.1. Establish a Fault Model
Fault models are generated by using Petrel to import faults according to the above steps or manually and finely interpret them based on seismic data. In the process of manual interpretation, it should be noted that open the Fault interpretation tool option of the Tool Palette tool box, and correctly activate the corresponding fault name for editing, otherwise the result of fault disorder will occur, which will affect the subsequent fault interpretation and three-dimensional fault display (Figure 4).
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Figure 4. Fracture manual interpretation interface.
3.2. Layered Model
The establishment of the level model can directly import the level data into the software or manually interpret the three-dimensional seismic structure, supplemented by well-seismic combination, and use the mathematical interpolation method to generate the top and bottom surface structural maps of each layer, and then superimpose the generated top and bottom surface structural maps to finally establish a complete spatial level structural model (Figure 5).
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Figure 5. 3D data body and layer display interface.
4. Phase Modeling
Phase modeling means the distribution of discretized data into the entire model network, and Petrel provides several deterministic and random phase modeling techniques that characterize the phase band distribution characteristics in detail, such as indicating Chris, sequential indication simulation, truncated Gaussian simulation, neural network methods, etc., and can be used interactively. Users can accurately describe the spatial distribution of facies zones in each sedimentary period and analyze the history of sedimentary evolution [3] . Generally, the phase model of sequential indication simulation (A stochastic algorithm based on phase elements sets its own variation function and proportion for each phase, and establishes a sedimentary facies model under the constraints of the sedimentary conceptual model and the seismic attribute model) is used to calculate randomly, using the data analysis results, and adding the sedimentary facies distribution map of each layer to constrain.
5. Build Property Models
To establish the attribute model of the reservoir, each element in the 3D grid is assigned an attribute value, and the deterministic and random attribute modeling in the working area is carried out by using logging data and drilling data and trend graphs at each attribute level, and the sequential Gaussian simulation algorithm is used [4] .
In the actual attribute modeling process, there are two types: phased model and earthquake control model. The phased model first establishes a sedimentary facies model, constrains porosity in the sedimentary facies model, and then constrains permeability with sedimentary facies and porosity, while the seismic control model directly constrains porosity and permeability with seismic properties [5] . Generally, the phased model is mostly used when there are many wells in the study area. In this study area, there are more well location data and complete data, so the phased model is selected for modeling.
6. Conclusion
The abdomen of the Junggar Basin mainly develops the tertiary fault, and the third-stage fault is reduced through accurate fault interpretation, and the fault system, sand body drainage layer, unintegrated surface and other elements constitute a variety of oil and gas transmission combinations, through accurate structural model, petrographic model and attribute model, a geological model in line with the actual reservoir is established, the detailed characteristics of the reservoir are finely and accurately described, and the three-dimensional visualization of the underground reservoir is realized, which provides a basis for better understanding the characteristics of the reservoir and proposing more feasible development schemes. Establishing accurate 3D geological models and accurately depicting underground faults, fractures, and sand body connectivity are the key to the numerical simulation of reservoir engineering [6] .