Seismic Random Noise Attenuation Method Based on Variational Mode Decomposition and Correlation Coefficients

Seismic data is easily affected by random noise during field data acquisition. Therefore, random noise attenuation plays an important role in seismic data processing and interpretation. According to decomposition characteristics of seismic signals by using variational mode decomposition (VMD) and the constraint conditions of correlation coefficients, this paper puts forward a method for random noise attenuation in seismic data, which is called variational mode decomposition correlation coefficients VMDC. Firstly, the original signals were decomposed into intrinsic mode functions (IMFs) with different characteristics by VMD. Then, the correlation coefficients between each IMF and the original signal were calculated. Next, based on the differences among correlation coefficients of effective signals and random noise as well as the original signals, the corresponding treatment was carried out, and the effective signals were reconstructed. Finally, the random noise attenuation was realized. After adding random noise to simple sine signals and the synthetic seismic record, the improved complementary ensemble empirical mode decomposition (ICEEMD) and VMDC were used for testing. The testing results indicate that the proposed VMDC has better random noise attenuation effects. It was also used in real-world seismic data noise attenuation. The results also show that it could effectively improve the signal-to-noise ratio (SNR) of seismic data and could provide high-quality basic data for further interpretation of seismic data

Geological Structure Interpretation of Coalbed Methane Enrichment Area based on VMDC and Curvature Attributes

Geological structures play a leading role in the occurrence characteristics of coalbed methane (CBM), and curvature attributes are an important geometric seismic attribute that can be used to identify a geological structure. In view of the characteristics of curvature attributes which are easily affected by noise, this paper proposes a method based on variational mode decomposition and correlation coefficients (VMDC) for denoising, and then extracts curvature attributes for geological structure interpretation. The geological models with anticline, syncline and normal fault structure characteristics are constructed, and curvature attributes of geological models without noise and with different percentages of random noise are calculated respectively. According to the time window test results, the 5 × 5 time window is more suitable in the case of no noise, while 9 × 9 time window is more suitable when there is noise. The results also show that both the median filtering and VMDC can suppress random noise, but VMDC can suppress noise better and improve the accuracy of curvature attributes. Mean curvature attributes can effectively identify geological structures such as anticlines, synclines and faults. Gauss curvature is not ideal for identifying geological structures. Both the maximum positive curvature and the minimum negative curvature have obvious responses to some geological structures. The method has been applied to a CBM enrichment area prediction in Qinshui Basin, China, and the geological structure characteristics of this area have been preliminarily interpreted. The known CBM content information verifies the feasibility and effectiveness of the proposed method

Beneficial development practice and countermeasures of Baima block in Fuling shale gas field, Sichuan Basin

In recent years, while actively promoting the development and adjustment of high-pressure shale gas reservoirs such as Jiaoshiba shale gas reservoir, Fuling shale gas field has steadily expanded its development targets to Baima block and other complex structural blocks in order to ensure continuous and stable production capacity. Based on the strong structural deformation, complex geological conditions, low single-well productivity, and great development difficulty of Baima block, this paper deeply studies the tectonic deformation stages, stress field distribution characteristics, favorable targets, and development technical countermeasures of Baima block by means of fracture zone calcite U-Pb dating, three-dimensional stress field modeling, geoengineering integration evaluation and other technical methods, and has made positive progress: it is suggested that the thrust nappe force is the main controlling factor of the deformation difference of marine normal pressure shale gas reservoirs in Fuling area; the evaluation parameter system of "two categories, six items" for development area selection is established, and the south of Baima syncline core is identified as the most favorable target for beneficial development; a differentiated development technology policy based on the development characteristics of natural fractures has been formed; the engineering process countermeasures based on different geological characteristics such as gas well buried depth, stress property and crack are formed. On the basis of the above understanding, and in accordance with the idea of "overall deployment, evaluation-construction integration, and platform replacement", 30 development well locations were deployed and implemented in 2021-2022, the average ROP was increased by 38%, the fracturing rate was increased by 2-3 times, the single stage fracturing cost was reduced to 850 000 yuan, the daily gas output was stable at 800 000 square meters, and the annual gas output reached 224 million square meters in 2022, basically realizing beneficial development

Research on Digital Power Grid Information Integration Solution

Information integration is an important part of the digital grid architecture. The purpose is to solve the information interaction obstacles between heterogeneous systems on the basis of making full use of the old system. This paper analyzes the development stage of digital power grid information integration from the perspective of information integration, and points out that the information integration of current digital power grid is mainly data-oriented integration. Based on the characteristics of digital power grid information integration, this paper puts forward a digital power grid information Integration solution combining horizontal information integration and vertical information integration, designs the overall architecture of digital power grid information integration, and elaborates the horizontal integration and vertical integration respectively

Characteristics and controlling factors of the organic-rich shale in the Wujiaping Formation of the Hongxing area, eastern Sichuan Basin

Objective The organic-rich shale of the Upper Permian Wujiaping Formation in the Hongxing area of eastern Sichuan is an important replacement area for shale gas exploration in the Sichuan Basin, and the exploration breakthroughs have been made. But how to achieve large-scale storage increase and efficient development needs to be tackled. Methods This paper investigates the source and reservoir quality characteristics of the shale of the Wujiaping Formation in the Hongxing area of eastern Sichuan based on lithological, geochemical and gas-bearing test and analysis data and discusses the factors controlling the development of high-quality reservoirs. Results The results show that the shale of the Wujiaping Formation has a good organic matter type, dominated by type Ⅱ1 kerogen, with high TOC content, high carbonate content and high gas content. The shale TOC content generally ranges from 1% to 11%, with an average value of 6.89%; the lithology is mainly siliceous shale and mixed shale, followed by calcareous shale, and the overall brittle mineral content is high; the reservoir organic matter pores are developed and have good physical properties, and the porosity generally ranges from 2% to 5%, with an average value of 3.1%. Comprehensive analysis shows that the high-quality reservoir of the Wujiaping Formation is strictly controlled by the depositional environment. The reservoir pore type is dominated by organic pores. Conclusion Under the control of this depositional model, sea level rise and fall, volcanic activity and palaeoclimate have jointly controlled the inhomogeneity and high-quality shale reservior distribution

Research on Digital Power Grid Information Integration Solution

Information integration is an important part of the digital grid architecture. The purpose is to solve the information interaction obstacles between heterogeneous systems on the basis of making full use of the old system. This paper analyzes the development stage of digital power grid information integration from the perspective of information integration, and points out that the information integration of current digital power grid is mainly data-oriented integration. Based on the characteristics of digital power grid information integration, this paper puts forward a digital power grid information Integration solution combining horizontal information integration and vertical information integration, designs the overall architecture of digital power grid information integration, and elaborates the horizontal integration and vertical integration respectively

Investigation of Multiscaled Pore Structure of Gas Shales using Nitrogen Adsorption and FE-SEM Imaging Experiments

Nanopore in shales is the place for hydrocarbon accumulation and migration. However, there is a lack of understanding of the nanopore structure with regard to their ultratight and multiscaled nature. Here, the porous morphology of gas shales from the Sichuan Basin of China was investigated using field emission-scanning electronic microscopy (FE-SEM) with high resolution. Low-pressure nitrogen adsorption experiments at 77 K were conducted to obtain the adsorption-desorption isotherms, BET-specific surface area, pore size distribution, pore volume, and average pore diameter values. Research results show that pores of the studied shales are at the nanometer scale, and the average pore diameter is between 3 and 5 nm. The pore structure of these shales is complicated, which is not only predominately mesopores (pore diameter at 2–50 nm) but also some micropores (pore diameter50 nm). The specific surface area of shales ranges from 13 to 30 m2/g. The micropore volume and mesopore volume occupy the total pore volume highly up to 77%–92%, which indicates that micropores and mesopores are the main storage place for shale gas. Through the analysis of adsorption isotherms and hysteretic loops, there are mainly two kinds of pores in shales, including ink-bottle-like pores and slit pores. Micropores of these shales are mainly related to organic matter, while macropores are mainly related to clay minerals. The estimation about porosity using the combined physical model shows that organic matter and clay minerals contribute about 50% and 33% to the porosity of these shales, respectively

Genesis of Bedding Fractures in Ordovician to Silurian Marine Shale in Sichuan Basin

The effective utilization of shale bedding fractures is of great significance to improve shale gas recovery efficiency. Taking the Wufeng–Longmaxi Formation shale in Sichuan Basin as the research object, the formation process and mechanism of bedding fractures in marine shale are discussed, based on field observation and description, high-resolution electron microscope scanning, fluid inclusion detection, and structural subsidence history analysis. The results show that the formation of bedding fractures is jointly controlled by sedimentary characteristics, hydrocarbon generation, and tectonic movement: the development degree of bedding (fractures) is controlled by the content of shale organic matter and brittle minerals, and bedding fractures formed in the layers with high organic matter; tectonic movement created stress environment and space for bedding fractures and promoted the opening of bedding fractures; the time for calcite vein to capture fluid is consistent with the time of oil-gas secondary pyrolysis stage. The formation of the calcite vein is accompanied by the opening of fractures. The acid and oil-gas generated in the hydrocarbon generation process occupied the opening space and maintained the bedding fractures open. The study of the formation process of bedding fractures is helpful to select a suitable method to identify bedding fractures, and then effectively use it to form complex fracture networks in the fracturing process to improve shale oil and gas recovery

Lamellation Fractures in the Paleogene Continental Shale Oil Reservoirs in the Qianjiang Depression, Jianghan Basin, China

Based on the data of cores, thin sections, well logs, and test experiments, the characteristics and main controlling factors of lamellation fractures in continental shales of the third and fourth members of the Paleogene Qianjiang Formation in the Qianjiang Depression, Jianghan Basin, are studied. Lamellation fractures mainly develop along laminas in shales. They have various morphological characteristics such as straightness, bending, discontinuity, bifurcation, pinching out, and merging. Lamellation fractures with high density show poor horizontal continuity and connectivity characteristics. The average linear density of the lamellation fractures is mainly between 20 m-1 and 110 m-1, and the aperture is usually less than 160 μm. The density of lamellation fractures is related to their apertures. The smaller the apertures of lamellation fractures are, the higher the density is. The development degree of lamellation fractures is mainly controlled by mineral composition, type, thickness, density of lamination, contents of organic matter and pyrite, lithofacies, structural position, etc. Lamellation fractures develop well, especially under the conditions of medium dolomite content, large lamination density, small lamination thickness, and high total organic carbon (TOC) and pyrite contents. The influences of lithofacies on the lamellation fractures are complex. The lamellation fractures are most developed in carbonaceous layered limestone dolomite and carbonaceous layered dolomite mudstone, followed by stromatolite dolomite filled with carbonaceous pyroxene. The fractures in the massive argillaceous dolomites and carbonaceous massive mudstones are poorly developed. No fractures can be found in the carbonaceous dolomitic, argillaceous glauberites or salt rocks with high glauberite content. Structure is also an important factor controlling lamination fractures. Tectonic uplifts are beneficial to the expansion and extension of lamellation fractures, which increases fracture density. Therefore, when other influence factors are similar, lamellation fractures develop better in the high part of the structure than in the low part