Application of General Fractal Dimension to Coupling Fault Diagnosis

This paper presents the coucept of general and sensitive dimension, and also proposes the calculation formula of the general dimension least squares method. By calculating and analyzing the power spectrum and general dimension from the fault sample, the relationship is achieved between sample status and the general dimension from vibration signals of the equipment so as to provide reference to fault diagnosis. Furthermore, a correlation function of general dimension is proposed, and calculations are carried out for a monitor signal and samples signal. The diagnosis method based on fractal theory is effective through the concrete examples of the steam electric generating set fault diagnosis, and the correlation coefficient of general dimension between a monitor signal and samples signal can improve the accuracy for fault diagnosis.

Coupled Faults Analysis and Evaluation M ethods Based on Cellular Automata

The reliability analysis of coupled faults may be difficult due to its properties of multiple and intermittent. The challenge is to find the rule and depict of the cross-linking relationship by mathematical model. The method in this study was developed around the Cellular Automata( CA) with a novel neighborhood definition and the structure of network model to build the failure cellular automata. And the simulation of the coupled faults influence combined with the importance evaluation method of network node to find the most critical faults which were beneficial to improve the design,without consuming massive computational overhead.

Safety prognostic technology in complex petroleum engineering systems: progress, challenges and emerging trends

Oil and gas facilities used in the petroleum industry can be considered as complex dynamic systems in that they require different types of equipment with various causal relationships among components and process variables under monitoring.As the systems grow increasingly large,high speed,automated and intelligent,the nonlinear relations among these process variables and their effects on accidents are to be fully understood for both system reliability and safety assurance.Failures that occur during the process can both cause tremendous loss to the petroleum industry and compromise product quality and affect the environment.Therefore,failures should be detected as soon as possible,and the root causes need to be identified so that corrections can be made in time to avoid further loss,which relate to the safety prognostic technology.By investigation of the relationship of accident causing factors in complex systems,new progress into diagnosis and prognostic technology from international research institutions is reviewed,and research highlights from China University of Petroleum（Beijing） in this area are also presented.By analyzing the present domestic and overseas research situations,the current problems and future directions in the fundamental research and engineering applications are proposed.

Relationship between seismic structures and the diverse rupture processes of the 2023 Türkiye earthquake doublet

Recent geodetic and seismological observations of two major earthquakes in southeastern Türkiye in February 2023 have revealed complex rupture initiation,propagation,and segmentation along the East Anatolian Fault Zone(EAFZ)and surrounding regions.However,the role of upper crust structures along the EAFZ in determining the diverse rupture processes of this earthquake doublet remains unclear.To further investigate this,we employed double-difference location and seismic tomography techniques to determine high-resolution seismic velocities(V_(P),V_(S))and Poisson’s ratio(σ)structures using a multiparameter joint tomographic algorithm.Our dataset includes 100,833 high-quality source-receiver travel-time pairs of P-and Swaves.We find that the unique rupture processes of this earthquake doublet were primarily influenced by contrasting crustal seismic structures and localized geological settings.The M_(w)7.8 mainshock was initiated within a transitional edge zone characterized by a rigid part(asperity)of the seismogenic zone with sharp contrast variations in rock strength ranging from low to high along the EAFZ.In comparison,the M_(w)7.6 rupture originated in a ductile belt featuring fluid saturation with low-VP,low-VS,and high-σvalues that extended parallel to the Cardak Fault.The pronounced contrast structures observed along the former rupture can be attributed to the oblique collision system between the weakened section of the east Anatolian plateau and the brittle Arabian platform,while the latter rupture was initiated within the ductile structure associated with fluid intrusion caused by the northward subduction of the Cyprus slab and subsequent detachment.Furthermore,the occurrence of the first earthquake(E1)serves to alleviate shear stress on the second earthquake(E2)fault,potentially impeding the initiation of an E2 rupture.On the contrary,this event also significantly reduces the normal stress acting on the E2 fault due to a double left-lateral strike-slip system within a triangular region.This reduction not only results in a decrease of fault friction force and an increase in rock porosity but also induces lower strain drops and the redistribution of Coulomb stress,thereby contributing to the initiation of the E2 event.The proposed rupture pattern exceeds the conventional model that governs individual earthquake ruptures,offering new insights for mitigating potential seismic disasters in Türkiye.The lessons learned from this doublet event can contribute to reevaluating the ongoing risk of damaging earthquakes in China’s South-North Seismic Zone or other regions worldwide with comparable geological conditions.

Formation and characteristics of large-medium buried-hill hydrocarbon reservoirs in Bohai Sea

There had been a long history of the buried-hill hydrocarbon reservoirs exploration operation in Bohai Sea.Between 1970s and 1990s,based on the onshore exploration experiences in eastern China,many boreholes were drilled in order to detect large-scale carbonate buried-hill hydrocarbon reservoirs in Bohai Sea,but no prominent discoveries was achieved.In-depth re-evaluation and examination were conducted upon these exploration failures,a new understanding that Bohai Sea had unique geological characteristics of buried hills was concluded.Bedrocks on the uplifts of Bohai oil province were mainly granites and migmatitic granites of Archean,Proterozoic and Mesozoic,as well as minor Lower Paleozoic carbonates.Proterozoic algae dolomite was most favorable for buried-hill hydrocarbon reservoirs however which were not developed in Bohai Sea.A large number of faults in Bohai oil province were developed and faults activities were intense in the late period.Thus,conventionally,reservoirs and preservation conditions of the buried hills were believed to be poor in Bohai Sea,and were not favourable for formation of large-scale buried-hill hydrocarbon reservoirs.Through the long-term practices and deep analyses,the coupling between granites,migmatitic granites and intense bedrock faults was favorable for buried-hill reservoirs with high test production and relatively low core recovery rate.Geophysical data could be used for accurate predictions of bedrock lithology and faults.The monadnock buried hills on the low uplifts adjacent to hydrocarbon-rich sags were covered by shallow to semi-deep lacustrine shale,which was favorable for buried-hill hydrocarbon reservoirs.Under the guidance of a series of innovative understandings,the re-exploration of buried hills in Bohai Sea achieved two largest granite buried-hill oil and gas fields with 100 million tons of reserves.The understanding and practice processes might also inspire exploration of other areas.