Fault Block Research Articles

Structural geometry of the Urumqi foreland thrust system, northern Tian Shan: Insights into the seismotectonics of the 2013 M 5.1 Urumqi earthquake and deformation pattern in the Urumqi area

In foreland thrust systems, the complex structural geometry creates greater difficulties in constraining the seismotectonics of moderate magnitude earthquakes without pronounced surface ruptures and in assessing future seismic risk. The 2013 M 5.1 Urumqi earthquake was a moderate event that occurred in the Urumqi foreland thrust system. Based on surface investigations, geological mapping, and interpretations of deep seismic reflection profiles, we suggest that the Urumqi foreland thrust belt is a typical active wedge thrust system. Two connected fault segments of the gently south-dipping blind fault ramp and the north-dipping Xishan back-thrust fault merge at a depth of ~11 km and bound the wedge-shaped fault block. Analyses of the focal mechanism and aftershock distribution indicate that the seismogenic fault responsible for the M 5.1 Urumqi event is the south-dipping Xishan fault ramp with a dip angle of ~10–30°, which highlights the potential seismic hazards of the unruptured north-dipping Xishan back-thrust ramp. The four fault branches on the hanging wall of the Xishan fault are interpreted as flexural-slip thrusts. Our results indicate that multiple surface ruptures over a 6 km-wide area may form if a large earthquake occurs along the Xishan fault system.

Fine Geological Modeling of Complex Fault Block Reservoir Based on Deep Learning

Nowadays, people’s demand for underground mineral resources is increasing, and geological disasters have occurred frequently in recent years. Geological disasters refer to geological effects or geological phenomena that are formed under the action of natural or man-made factors, causing loss of human life and property, and damage to the environment; such as landslides, collapses, mudslides, and ground subsidence. Under such a background, people must accelerate the exploration of complex geological structures. This paper is aimed at using the methods and concepts of deep reinforcement learning. Deep learning is to learn the inherent laws and representation levels of sample data. The information obtained during these learning processes is of great help to the interpretation of data such as text and images. In this way, the fine geology of complex fault-block reservoirs is modeled and studied. Geological structures and phenomena are discussed through convolutional neural network models and computer techniques. At the same time, the multitask bird recognition network is used to extract and classify geological images, so as to construct geological model maps with different spatial structures. Finally, the quality of the fault reconstruction model, the calculation of reservoir geological simulation reserves, and the evaluation of the water injection development effect of complex fault blocks are analyzed. In the evaluation of the development effect of water injection in complex fault blocks, comparing the relationship curve between the actual comprehensive water content and the oil recovery factor with the standard curve, the comprehensive water content of the initial block increased rapidly. Through timely and dynamic water allocation and comprehensive management, the water cut rising speed is controlled. The current comprehensive water cut of the reservoir is between 60% and 80%, the actual curve is between 25% and 35%, and the estimated waterflooding recovery is about 30%.

A Detailed Review of MMC Circuit Topologies and Modelling Issues

MMC is a promising technology for MTDC systems and would transform into the concept of Supergrids in the near future. The salient features of MMC are modularity, reduced dv/dt and di/dt stress on switches, voltage and power scalability, inherent fault blocking capacity, transformerless operation, and improved power quality. However, there are some technical issues and challenges to be critically analysed and addressed. There is room for development of novel and enhanced MMC based on SM configurations to enable higher efficiency, improved power quality, compactness, and DC fault blocking capacity. Moreover, development of efficient and accurate models is required for the studies of MTDC grids during steady-state and transient conditions. Literature review suggests a need for studying and comparing different MMC modelling approaches because no modelling technique can be best suited for all applications. The main contribution of this paper is to provide a comprehensive review of recent developments in MMC in terms of SM configurations. This paper also presents an in-depth review of systematic comparison of different models of MMC, which can enable appropriate selection of model based on target studies and desired accuracy and efficiency. Finally, the associated research challenges and future trends are presented.

Salt dissolution tectonism and origin of lacustrine carbonate beds: Mn‐Fe‐calcite and Mn‐siderite micro‐spherulite fabrics of the Lower Cretaceous McMurray Formation, Athabasca Oil Sands deposit, western Canada

AbstractSeveral lacustrine carbonate beds, each a metre‐thick interval of densely packed Mn‐rich sideritic micro‐spherulites or Mn‐rich ferroan calcite micro‐spherulites, are recorded for the first time within strata of the Lower Cretaceous McMurray Formation of the northern Athabasca Oil Sands deposit, western Canada. A lower McMurray lacustrine carbonate deposit is characterised by a metre‐thick bed fabric of Mn‐rich siderite micro‐spherulites. The middle and upper interval McMurray beds developed fabrics of Mn2+‐rich ferroan calcite micro‐spherulites. These carbonate beds represent saline lacustrine depositional environments that resulted from the lake bottom sediments ingressed from below by Mn2+‐Fe2+‐rich carbonate‐saturated brines. These up‐section migrations of Devonian formation water were sourced from dissolution trends developed in limestone and halite‐anhydrite beds of the underlying Devonian Prairie Evaporite during Cordilleran deformation of the Alberta Basin foreland. These brines ascended to the overlying McMurray Formation sediments along dissolution‐collapse structures such as breccia pipes, sinkholes and margins of differentially subsided Upper Devonian fault blocks. The up‐section migration of a sulphate‐saturated Fe2+ and Mn2+‐rich brine resulted in the ingress of a lower McMurray lacustrine bottom sediment at a site associated with the development of a peat mire terrain. Microbial redox of the lake bottom sediment resulted in a carbonate bed of micro‐spherulitic fabrics of Mn‐rich siderite interwoven with pyrite laminae. Subsequent salt dissolution events and up‐section migrations of Devonian brine during deposition of the middle and upper McMurray intervals resulted in similar carbonate‐saturated but sulphate‐poor chemistry. These saline flows also ingressed lacustrine bottom sediments below, and resulted in limestone beds of densely packed spherulitic fabrics of Mn‐ferroan calcite, not siderite. These deposits provide insight into largely unknown dispositions of voluminous brine resulting from salt dissolution trends below the Athabasca Oil Sands and further our understanding of controversial McMurray depositional processes.

Carbazoles in Oils, and Their Application in Identifying Oil Filling Pathways in Eocene Syn-Rift Fault Blocks in the Dongpu Depression, Bohai Bay Basin, East China.

Carbazoles and dimethyl carbazoles (DMCs) are important nitrogen heterocyclic aromatic compounds in oils and sedimentary rock extracts. Based on both migration fractionation effects and differences in the thermal stability of their isomers, carbazoles can be used to trace oil migration orientations and filling pathways. Molecular biomarker compositions indicate that all oils and oil-bearing sand extracts in the Eocene fault-blocked reservoirs of the Huzhuangji area (Western Slope Belt) of the Dongpu Depression (Bohai Bay Basin, East China) belong to a single oil population. In this study, four geochemical indicators relating to carbazoles, namely (a) 1,8-/2,7-dimethyl carbazoles (1,8-/2,7-DMC); (b) 1,8-/2,5-dimethyl carbazoles (1,8-/2,5-DMC); (c) 1,8-/N-exposed dimethyl carbazoles (1,8-/N-exposed DMC); and (d) G1 N-shielded %, were applied to trace oil migration orientations and filling pathways. The results show that these parameter values gradually increase toward the Hu-5 fault block at the structural high. The measured values from the subsurface are consistent with the results calculated from the molecular adsorption modeling. Therefore, it is concluded that the relative parameters of dimethyl carbazoles are practical molecular indicators for tracing oil migration orientations and filling pathways in syn-rift fault-blocked reservoirs.

Secondary faulting plays a key role in regulating the Cenozoic crustal deformation in the northeastern Qinghai‐Tibet Plateau

AbstractIn this study, channel steepness and main divide migration analysis were conducted on the Qinghai Nanshan to confirm the activity and evolution of the range. The results showed that the broad and gently dipping northern limbs correspond to relatively low steepness values, while the narrow and steeply dipping southern limbs are characterized by higher steepness distribution. In addition, main divide of the range is currently stable, despite its tendency migrating northward. Based on previous numerical simulations and our geomorphological results, we suggested that the Qinghai Nanshan thrust Fault is tectonically active. The sustained thrust activities of the fault have uplifted the Qinghai Nanshan, driven southward migration of the main divide and caused obvious regional crustal shortening and thickening. Given the same landscape characteristics as the Qinghai Nanshan, the Gonghe Nanshan was found to have appreciable influence on regional crust deformation. Secondary active tectonics (e.g. the Qinghai Nanshan and Gonghe Nanshan) could subdivide rigid blocks into smaller ones and promote the slip transferring and strain regulation between boundary strike‐slip faults. In summary, we concluded that continuous crustal deformation within the northeastern Qinghai‐Tibet Plateau is implemented through strain assimilation by minor faults in minor blocks.

Fault Ride-Through Capability of MMC Based Wind Power Plant Integrated Under a DC-Link Fault

This paper presents a novel fault ride-through (FRT) capability with the use of active converters (Vienna rectifier-I and five-level three-phase modular multilevel converter (MMC)) integrated with permanent magnet synchronous generator (PMSG) supplying AC load. The DC-link fault is controlled with the use of fault blocking diode and MMC sub-module (SM) based wind power plant (WPP). A 16 kW, 60 Hz, PMSG and wind turbine (WT) integrated with the machine-side converter (MSC), and grid-side converter (GSC) are utilized as wind farm components, along with direct current (DC) transmission grid. This topology contributes to the stability and reliability of the system by ensuring continuous output power under transient fault conditions. The functional response of the system is presented using power simulator (The PowerSim, Rockville, USA) software to demonstrate the performance of the proposed controller.

Mechanism Study of Hydrocarbon Differential Distribution Controlled by the Activity of Growing Faults in Faulted Basins: Case Study of Paleogene in the Wang Guantun Area, Bohai Bay Basin, China

Abstract Mechanisms that lead to different quantities of hydrocarbon accumulation in complex fault blocks are a major subject that impacts further development plans of oil and gas fields. To better understand such mechanisms, fault activity has been interpreted along with existing electron micrographs from the fault zone, petrophysical data, and the occurrence of the seismic pump. This enabled us to investigate the controlling mechanisms of the growth faults and other associated faults with the main growth fault in the Wang Guantun area that could have impacted hydrocarbon distribution. The results showed that the activity of Kongdong growth fault is periodic and intermittent, which produced strong seismic pumping action. Furthermore, a series of secondary faults were generated in adjacent strata due to the fault activity, which could have led to the formation of a secondary seismic pump source. A combination of these two incidents is believed to influence the differential distribution of hydrocarbons in the area, in fault-associated reservoirs. Ultimately, we correlated the activity of the growth fault to the strength of the pumping force causing the distribution of hydrocarbons in the active parts of the faults (pump source position) on the horizontal plane and vertically located reservoirs to be more dominant.

Sediment deformation atop the Lomonosov Ridge, central Arctic Ocean: Evidence for gas-charged sediment mobilization?

We have used a hovercraft platform drifting with the sea ice to acquire the first digitally recorded seismic reflection data transects across the Canada/Greenland (89°N-85°N) section of the Lomonosov Ridge, central Arctic Ocean. The flat-lying, laterally uniform Cenozoic sediment package on top of the ridge at 87°N, 60° W shows at least four sites with local seismic amplitude anomalies. The common feature is a column (<600 m wide) of partly discontinuous or chaotic bright reflection events at the center of a <1.5 km wide dome (amplitude <25 m) terminating at the seabed in a 8–12 m deep depression. The amplitude anomalies are interpreted as gas-charged fluid escape pipes marked by a pockmark at the seabed. Gas and fluids introduced from below have mobilized the overlying high porosity, low density Eocene bio-siliceous ooze causing the doming. The gas and fluids appear to originate from the top of rotated fault blocks and sub-basalt sediments of Mesozoic or older age deposited when the Lomonosov Ridge was part of the pre-Late Cretaceous continental margin north of Franz Josef Land.

Application of depth learning in prediction of glutenite reservoir

Sedimentary facies of gravel reservoir has the characteristics of multiple sources and short flow. Sand body thickness changes rapidly in plane and space. Model-based multi-attribute regression seismic reservoir prediction method often results in unreasonable inter-well prediction results because of insufficient generalization ability of the model. For this reason, a deep learning reservoir prediction method based on fault blocks is proposed. Within a fault block range (regardless of wells outside the fault block), the seismic attributes extracted from the sliding time window of the isochronous sedimentary surface are used as input, and the sandstone thickness data of the target layer of the well point are used as expected output to train the depth neural network model of the multi-layer perceptor. Then, the trained model is used to predict the sandstone thickness distribution in the well distribution area. The application of actual data in A oilfield shows that the predictive coincidence rate of sandstone thickness in known wells is more than 95%, and the drilling occurrence rate of sandstone in horizontal section after completion of a posterior horizontal well is more than 80%. This method has high prediction accuracy and good generalization ability.

Study on oil-water interface of Budate fracture reservoir in each block of Suderte Oilfield

It is well known that in addition to bound water in the reservoir, formation water mainly exists in the form of edge water and bottom water. Fractured buried hill metamorphic rock reservoirs are generally bottom-water reservoirs. In fractured reservoirs, rock blocks are cut by fractures and oil and water are distributed in fractures. Due to the low capillary pressure of fractures, the oil-water transition zone is also small. In the same fault block, there is relatively uniform oil-water interface. And oil-water interface to judge correctly or not will directly related to the determination of oil-bearing area and effective thickness division and well placement, thus correctly determine the position of the oil-water interface of oil field development is of great significance, through the variation of oil-water interface also presumably or some guidance on the seismic section can't precisely divide the small fault.

Main controlling factors and models of tight oil accumulation in Zhaoyuan area

The study block opens up with the already found oil reservation, through the comprehensive analysis to seismic, well logging, well log and core data, collate and stipulate the system of fault, and then make sure the oil source fault; Meanwhile we make use of Geo-Office and Jason multiply technology, to launch micro faces and single sand body spread research. The result shows that, the study block mostly have 4 kinds of oil reservation: fault-lithologic, fault block, fault-screened and lithologic reservoir, the main target layer is Fuyu oil layer of Quantou Formation 3 and 4 part, the reservation and spread of oil is mainly controlled by the distance to the oil source, the space spread which is coordinated to form transportation system by fault concentrated belt and sand body, the high fault block trap. The oil reservation mainly exist in the internal part of fault concentrated belt and the sand body nearby, all in all the spread feature shows that the oil stays above and the water keeps low, and the formations which includes oil becomes less and less from the downstructure location to the updip; The major period for hydrocarbon accumulation is the late period of the Mingshui Formation deposition; Here are the modes of the oil transformation and reservation : the oil goes downward and flow backward and transforms into Fuyu formation, which origins from the source rocks of Qingl member in Sanzhao depression, under the abnormal pressure through the source fault, and then the oil in Fuyu formation of Sanzhao depression transforms to study block under the affect of floatage along the two fault concentrated belt which was linked up by the sand body, at the upstructure location lithology or fault aligns with lithology forms the trap which keeps together to oil reservation.

Feasibility Study for Well pattern Encryption in Complex Fractured Block Reservoirs--Taking the Liu 90 South Fault Block in the Jidong Oilfield as an example

Jidong oilfield belongs to complex fault block reservoir, and the development has now entered into high water-cut stage. when using Well pattern encryption technology to stabilize production, it is necessary to study the feasibility of Well pattern encryption to ensure a better economic benefit. In this paper, we use theoretical analysis method, consider the influence of oil price on the calculation, improve the economic limit Well pattern density calculation formula, calculate the economic limit Well pattern density under different recovery rates, make recovery rate prediction for different Well pattern density scenarios by combining with Sherkachov's formula, and use the curve intersection method to determine the Well pattern density at the break-even point, so as to determine the economic feasibility of Well pattern encryption. The example calculations show that the use of well network encryption alone does not meet the development requirements of the Liu 90 South block and has no significant economic benefits, so a combination of two-three methods is needed to further improve the recovery rate. Numerical simulation prediction results show that the two-three combination method can improve the recovery rate by 14.54%, accumulate 28.88×104t of oil increase and increase revenue by 678,245,000 yuan.

3D Seismic Data Interpretation in Gumry Field, Melut Basin

This work describes interpretation of 3D seismic data of Gumry area which is located in Blocks 3 & 7 in Melut Basin the South of Sudan. The data used in this study was acquired by Blue Nile Geophysical Company (BGC) in 2004. The 3D data was interpreted by the author at the SUDAPET CO. LTD in Khartoum – Sudan, Vertical Seismic Profiling data (VSP) and Check-Shot data of the Gumry-1 well were used. The data quality is good and adequate for the objectives. Geoframe software has been used which enables to display inline, cross line and time slice and also enables checking of the consistency of the interpretation from line to line. Synthetic seismogram has been generated for Gumry _1 well for seismic data tie. Time and depth maps have been generated for the top of Yabus Formation. The 3D data interpretation clarifies that there are many oil structures found in study area such as normal faults, faulted trap, graben, half graben, and faulted anticline. Faults system in Gumry area consists of normal faults, trending NW-SE, with some of them dipping SW and others dipping NE. Gumry oil field prospects are mainly fault block structure, located at the block up thrown side of the normal Fault block.

BAYESIAN NETWORKS FOR RELIABILITY ANALYSIS OF TECHNICAL SYSTEM

The works to provide reliability assurance and enhancement are most effective at the early stages of life cycle. The common requirement is fast and precise performance of reiterated reliability analysis, as far as the system design development and the complete data accumulation on system components reliability. Recently, Bayesian networks has been introduced in reliability engineering. Bayesian networks are a promising tool for reliability analysis. Today, Bayesian networks are actively used to fault diagnosis and reliability estimates. In this article, utilization of the Bayesian networks for reliability analysis at the early stages of life cycle is studied. The reliability can be calculated by converting block diagrams or fault trees into Bayesian networks. Fault trees can easily be converted into Bayesian networks. Therefore, in this article, a perspective approach to combine the Bayesian networks mechanism and Fault tree analysis method is studied for reliability assessment of a technical system. The system is an electronic fire sensor. As a result, the developed model of Bayesian networks provides the estimation of failure probability at the conditions of real-life scenarios of system behavior; the calculation of the probability of no-failure operation of the system under control and its sub-systems; the detection of the elements that contribute the most to the failure probability. The Bayesian networks model can be easily built from the circuit diagram analysis and the FMEA (Failure Modes and Effects Analysis). In general, this method has the best capability in this real instance compared to other methods.

Reducing uncertainty with fault seal analysis: A case study of Jherruck Block, LowerIndus Basin, Pakistan

Faults can be either conduits or baffles for hydrocarbon flow. Assessing the sealing potential of faults plays a vital role in reducing the risks associated with hydrocarbon exploration. The study area is located in Jherruck Block, Lower Indus Basin, Pakistan. Several intervals within the Lower Goru Formation in Lower Indus Basin are proven hydrocarbon reservoirs. The main aim of the study is to predict the cause of failure of 3 wells (Jherruck B-1, Jamali-1, and Jamali Deep-1), and to propose a new well location based on juxtaposition analysis and shale gouge ratio (SGR). The Upper Sands (sandstone) of the Lower Goru Formation (A-Sand, B-Sand, C-Sand, and D-Sand) have reservoir potential in the region including the Jherruck Block. These reservoir sands have been interpreted in seismic sections to generate time and depth surface maps. Using depth surface maps, Allan diagrams have been constructed for juxtaposition and shale gouge ratio analysis. The integration between juxtaposition and shale gouge ratio analysis suggested that the main reason for the failure of these wells was sandstone to sandstone juxtapositions leading to updip hydrocarbon leakage to the adjacent fault block. In addition to this, the shale gouge ratio indicated low shale gouge distribution in the fault zones. Allan diagram and shale gouge ratio analyses helped us to propose a new well location further northwest of Jherruck B-1 well where sands are juxtaposed against impermeable shale lithology of the Goru Formation and SGR ratio is above 80%.

Study on reservoir description technology of complex fault block oilfield——Taking the South 1st member of D sag as an example

The D sag has developed faults, serious erosion and fault loss, developed glutamate, strong heterogeneity, and large formation dip, which makes stratigraphic comparison difficult and unclear understanding of oil reservoir and oil-water relationship during the development process. For this reason, this study was carried out. On the basis of the existing seismic interpretation results, carry out the fine structural interpretation of the main sub-layers in the study area; carry out the study of sedimentary characteristics, divide the sedimentary facies, and clarify the sedimentary characteristics of the main sand bodies; use the core analysis data to establish the interpretation of physical parameters in the study area model, and establish a fine three-dimensional geological model, through the study of oil-water distribution law, carry out potential research, and select favorable well-distributed blocks.

Single-Sourced Double-Stage Multilevel Inverter for Grid-Connected Solar PV Systems

Design challenges for grid-connected solar PV systems related to the power conditioning units are power quality, efficiency, reliability, cost of implementation etc. This paper deals with single dc source-based double LDN high-resolution multilevel inverter topology with the appropriate blend of switches to address most of the practical constraints of central inverter application. A two-stage high-resolution multilevel inverter solution is adapted to double the inverter utilization as well as to increase efficiency. Reactive power handling and fault blocking capability of the system are also demonstrated in this work. The converter is extensively simulated using MATLAB/Simulink. Experimental results from laboratory prototype confirm the usefulness of the proposed concepts.

Reducing uncertainty with fault seal analysis: A case study of Jherruck Block, LowerIndus Basin, Pakistan

Faults can be either conduits or baffles for hydrocarbon flow. Assessing the sealing potential of faults plays a vital role in reducing the risks associated with hydrocarbon exploration. The study area is located in Jherruck Block, Lower Indus Basin, Pakistan. Several intervals within the Lower Goru Formation in Lower Indus Basin are proven hydrocarbon reservoirs. The main aim of the study is to predict the cause of failure of 3 wells (Jherruck B-1, Jamali-1, and Jamali Deep-1), and to propose a new well location based on juxtaposition analysis and shale gouge ratio (SGR). The Upper Sands (sandstone) of the Lower Goru Formation (A-Sand, B-Sand, C-Sand, and D-Sand) have reservoir potential in the region including the Jherruck Block. These reservoir sands have been interpreted in seismic sections to generate time and depth surface maps. Using depth surface maps, Allan diagrams have been constructed for juxtaposition and shale gouge ratio analysis. The integration between juxtaposition and shale gouge ratio analysis suggested that the main reason for the failure of these wells was sandstone to sandstone juxtapositions leading to updip hydrocarbon leakage to the adjacent fault block. In addition to this, the shale gouge ratio indicated low shale gouge distribution in the fault zones. Allan diagram and shale gouge ratio analyses helped us to propose a new well location further northwest of Jherruck B-1 well where sands are juxtaposed against impermeable shale lithology of the Goru Formation and SGR ratio is above 80%.

Study on Development Law of Complex Fluvial Reservoir under Water

The Bozhong oilfield (Hereinafter referred to as BZ oilfield) is a typical representative of complex fluvial reservoirs in the Bohai Sea, located in the southern Bohai Sea, with an average porosity of 30.3% and an average permeability of 643 × 10-3 μm2, belonging to medium high porosity and permeability reservoir, the reservoir has good connectivity, and the average underground crude oil viscosity is 5 mPa·s. There are many plane fault blocks, and the longitudinal oil well section is long, so the oil-water relationship is very complex. With the further development of the oilfield, the vertical and horizontal oil-water movement law, residual oil distribution and potential are unclear, resulting in rapid bottom water coning, unbalanced injection and production in the oilfield, and increasingly prominent contradictions among layers, planes and layers in the oilfield. Through numerical simulation analysis and comparison of displacement law and recovery degree under different influence conditions, this paper studies the development effect of actual sand body under different influence conditions such as different well types, different development methods and well layout positions, and takes appropriate development methods for the oilfield, which is of great significance to improve the development effect of the oilfield.