Large Sag Research Articles

Reconstructing early sedimentation patterns of the lower Codó Formation (Early Cretaceous, NE Brazil): Evidence of marine influence and the onset of an alkaline hypersaline lake

The upper Aptian lower Codó Formation is an attractive stratigraphic unit within the Parnaíba and São Luís basins, northeastern Brazil, formed during the break-up of Western Gondwana. Located in a large sag basin, the formation records a dynamic depositional history of deltaic, lacustrine, and sabkha environments. This sedimentary evolution is reflected in a diverse lithological succession characterized by intermittent terrestrial input, episodic marine incursions, and restricted lacustrine phases culminating in sulfate evaporite precipitation. While the later stages of the formation have been extensively studied, the initial sedimentary processes and environmental conditions remain poorly understood. This research aims to reconstruct the depositional paleoenvironments during the initial stages of Codó sedimentation, elucidating the onset of the alkaline hypersaline lake environment and the earlier marine incursions in the study region. To achieve this, it was conducted a high-resolution facies analysis using core descriptions, trace fossil analysis, petrography, various types of X-ray fluorescence, scanning electron microscopy, X-ray diffractometry, and isotope analyses (δ1³C, δ1⁸O, and ⁸⁷Sr/⁸⁶Sr) on a ∼63-m-thick succession from borehole 2-TV-1-MA. Thirteen facies were recognized and grouped into brackish lake, prodelta, delta front, and alkaline hypersaline lake facies successions. The lower Codó Formation exhibits cyclic sedimentation, indicating fluctuating water dynamics associated with shifts between open and closed drainage systems controlled by paleoclimate. Tectonic subsidence drove the basin's evolution from a brackish lacustrine-deltaic environment with an incipient marine influence (balanced-fill basin stage) to a restricted system with the establishment of an alkaline hypersaline lake (underfilled basin stage).

Scale-Up Investigation of a Pilot and Industrial Scale Semi-Autogenous Mill Using a Particle Scale Model

A particle scale model based on a full two-way coupling of the Discrete Element Method (DEM) and Smoothed Particle Hydrodynamics (SPHs) methods is applied to SAG mills. Motion and collisions of resolved coarser particles within an SAG mill are performed by the DEM component. Fine particles in the feed combine with the water to form a slurry, which is represented by the SPH component of the model. Slurry rheology is controlled by solid loading and fine particle size distribution for each volume of slurry. Transport, dispersion, and grinding of the slurry phase particle size distribution are predicted by solving additional coupled advection–diffusion equations in the SPH component of the model. Grinding of the finer particles in the slurry due to collisions and shear of the coarser particles (rocks and grinding media) is achieved via the inclusion of population balance terms in these equations for each SPH particle. This allows prediction of the transport of both coarser and finer material within the grinding and pulp chambers of an SAG mill, including the discharge performance of the mill. This particle-scale model is used to investigate the relative performance (throughput, product size distribution, resident particle size distribution, net power draw, wear) for an SAG mill at a pilot scale and a 36 ft industrial scale. The 36′ SAG mill considered is a geometrically scaled-up version of the 1.8 m Hardinge pilot scale mill but with a longer belly length, reflecting current SAG mill design preferences. The belly lifters are scaled to a lesser degree with a larger number of lifters used (but still many fewer liners than would typically be used in a large SAG mill based on conventional liner selection rules). The model shows that despite reasonable qualitative similarities, many aspects of the charge structure, slurry transport, coarse particle and slurry discharge through the grates, and the collision energy spectra vary in important ways. This demonstrates that a near purely geometric scale-up of an SAG mill is not sufficient to produce a comparable performance at the two physical mill scales.

Asymmetry and evolution of craton-influenced rifted margins

Abstract Rifting can result in asymmetric conjugate margins. In numerical models with laterally homogeneous lithosphere, the polarity of the asymmetry is random and results from spontaneous strain localization on a dominant fault/shear zone. However, along the central South Atlantic, margin width is well correlated to the proximity of the rift to a craton during rifting. To understand the evolution of rifting close to a craton, we used numerical experiments that included a thick craton lithosphere adjacent to a thinner, mobile-belt lithosphere. When rifting starts close to the craton, i.e., ≤ 100 km, deformation focuses along a fault/shear zone dipping toward the craton, leading to cratonward asymmetric asthenospheric uplift and rift migration. This results in a narrow margin on the craton side and a wide margin on the mobile-belt side. Craton-related asymmetry results in the wide margin subsiding more than the narrow one, inducing the formation of large synrift sag basins in the wide conjugate, as in the South Atlantic. This differential subsidence is preserved for ~100 m.y. after breakup and may partly explain the present-day higher dynamic topography close to cratons in the central South Atlantic. Mantle flow during asymmetric rifting leads to weakening of the craton lithosphere, partial intermixing, and recycling into the convective mantle, as interpreted for this sector of the South Atlantic ridge. Thus, rifting adjacent to a craton may have wide-ranging tectonic, stratigraphic, and compositional consequences that affect not only margin architecture, but also the development of subsequent dynamic topography and the spreading system.

Organic facies variability and paleoenvironmental characterization of the Codó and Itapecuru formations (Aptian-Albian) of Parnaíba Basin, Brazil

The Aptian-Albian sedimentary record of the Parnaíba Basin (NE Brazil), represented by the Codó and Itapecuru formations, is characterized by near-shore, shallow marine, and fluvio-lacustrine clastic sediments deposited in a large shallow sag basin that developed during the breakup of northwestern Gondwana associated with the early opening stages of the South Atlantic. This study aims to precisely characterize the nature, variability, paleoenvironmental significance and preservation conditions of the organic matter of the Aptian-Albian succession of the 2-TV-1-MA borehole (270 m). With these premises, organic petrographic and geochemical techniques were applied for the definition of the organic facies, allowing a better understanding of the Parnaíba Basin evolution during the Aptian-Albian interval. The 2-TV-1-MA borehole presents, at the base, a lacustrine system, with a high contribution of continental components deposited in a high energy, oxic environment, with incipient marine influence. This is intercalated by periods of restriction, with deposition occurring in a dysoxic-anoxic, low energy environment, with high contribution of higher plants. To the top, a relative decrease in the water-column leads to an increase in restriction, the emplacement of a stratified water-column, and the development of microbial mats. This is topped by a return to a high energy, oxic environment, with marine influence, and dominance of higher plants organic components.

A nonlinear finite element framework for static and dynamic analysis of structural cables with deviating supports

Structural cables are important load-bearing members in many light-weight and slender structures. The mechanical behaviour of tension cables is complex as it is dominated by geometric nonlinearities, complex support conditions and uncertainties arising from the composition of the cable cross section. Numerous models to describe static and dynamic cable behaviour were developed, differing in the model assumptions and the simplifications made. Most common are geometrical linearisation, dimensional reduction, and the disregard of localised support and stiffness effects. Some models take a combination of some geometric nonlinearities, cable bending stiffness and certain boundary effects into account. This paper first presents a literature review aimed at systematically categorising cable force identification models. Based on this, the paper proposes a novel numerical cable modelling framework that allows for accurate predictions of static and dynamic cable response, e.g. for the use in the inverse system identification techniques of Structural Health Monitoring. The saddled cable model is based on a nonlinear Finite Element formulation to account for the geometric and mechanical effects of deviating supports on structural cables even for very large sag cables. After validation with analytical solutions, the models show that the effect of self-weight distribution and cable bending stiffness considerably affects the identified internal force distribution, contact length on the saddle and cable form. Further, the model is used to predict the tension force based on the identified natural frequencies of an external tendon installed on a bridge. Compared with the actual tension force, the saddled cable model provided very high prediction accuracy, even when compared with other cable models. Therefore, it is shown to be very accurate and can be used to determine force-response relationships used in system identification techniques when increased accuracy is needed for such complex cable arrangements.

Late Permian siliceous hot springs developed on the margin of a restricted epeiric sea: Insights into strata-confined silicification in mixed siliciclastic‑carbonate successions

Hot springs are sources of carbonate minerals in modern settings; however, few fossil structures are recorded in successions older than the Quaternary due to their enhanced erosional potential. >4500 siliceous mounds are recognized in a well-defined level from the upper part of the Permian Teresina Formation (Paraná Basin, SE Brazil). Additionally, a new mound level is here reported for the first time about 15 m below the main occurrence. Remarkable lithological, mineralogical, paleontological and geochemical features characterize the mounds of both levels, pointing to a hydrothermal origin. Therefore, these structures are here called as hot springs. These were originated subaerially, on the margins of a closing epeiric sea developed on a large intracontinental sag basin. Hydrothermal fluids were sourced from deep circulating basin waters that erupted through intraplate deep-rooted faults. Our data suggests that these hot springs were active during distinct cycles of base level variations. Strata-confined silicification was enhanced during periods of high evaporation and hydrothermal exudation. Finally, the vertical and lateral facies associations of the Permian hot spring succession are compared with modern sites, and implications for the recognition of syn-depositional hydrothermally precipitated silica in ancient sedimentary basins are discussed.

Ultra-precision turning method efficient for optical freeform surfaces with a hybrid slow-fast tool servo.

The machining of freeform surfaces is a current research hotspot: A slow tool servo (STS) has limitations in machining accuracy and efficiency for large steep freeform surfaces. Most fast tool servo (FTS) tools are limited by their stroke and cannot manufacture freeform surfaces with a large sag. We propose a hybrid slow-fast tool servo method that combines STS and FTS to machine large steep freeform surfaces by decomposing the freeform surfaces and simultaneously turning efficiently with STS and FTS. Experimental studies were undertaken to fabricate a saddle surface. Meanwhile, a variable feedrates tool path was designed and applied to further improve the machining efficiency. The results show that this method can improve the processing efficiency by 47.5%. The arithmetic mean of surface roughness (Ra) is 2-4 nm, and the peak-to-valley (PV) value is 0.4780 µm at the hollows and 0.3884 µm at the swells.

Deep-Water Oil and Gas Exploration in Northern South China Sea: Progress and Outlook

Strengthening exploration and development of oil and gas is crucial for mitigating China’s reliance on oil and gas supply from foreign countries and ensuring national energy security. Since the 11th Five-Year period, fundamental research on the deep-water area of the northern South China Sea has been strengthened, along with the acceleration of technological innovation and increase in exploration investment. As a result, a series of major exploration discoveries were found. This paper presents five major learnings regarding the theories of exploration geology and two achievements in the innovation of exploration technology. It also discusses the new challenges and coping strategies for oil and gas exploration in deep-water areas, and prospects the exploration potentials of three major exploration fields—medium-deep layers, buried hills, and lithologic traps—in the deep-water area of the northern South China Sea. Our research shows that the detachment of the continental margin in the deep-water area of northern South China Sea controls the formation of large sags in the Pearl River Estuary Basin and the Qiongdongnan Basin. Three sets of large-scale source rocks were developed from lacustrine, terrestrial-marine transitional, and marine sedimentary facies. High yet variable subsurface temperature controls the rapid hydrocarbon generation from the source rocks in the sags. In addition, three different hydrocarbon accumulation modes were established: accumulation mode of large axial canyon channel in the deep-water area of the Qiongdongnan Basin, late natural gas accumulation mode of deep-water fan in the deep-water area of Baiyun Sag, and differential hydrocarbon accumulation mode jointly controlled by fault and ridge. Meanwhile, the broadband seismic acquisition and processing technology for three-dimensional source triggering and plow-like cable receiving was independently developed. Guided by several geological theories and innovative technologies, a series of large- and medium-sized gas fields represented by “Deep Sea No. 1” (LS 17-2) were discovered, which are of great significance to ensuring the energy supply of the Guangdong-Hong Kong-Macao Greater Bay Area, facilitating the green development of energy in the Hainan Free Trade Zone (Port), and promoting the increase of oil and gas reserves and production in China.

Voltage-Based Segmented Control of Superconducting Magnetic Energy Storage for Transient Power Fluctuation Suppression in Island DC Microgrid

Voltage stability is one of the critical factors for the stable operation of DC microgrids (MG). For the communication free DC MG, the DC voltage is more vulnerable due to the DC voltage deviation caused by the droop characteristics. When facing the transient power fluctuation caused by multiple electric vehicles (EVs) connected to the grid, PV shedding, etc., the DC bus will have a large voltage sag. The voltage quality degradation will bring adverse effects to the DC MG. However, most energy storage systems like battery energy storage systems (BESS) are not suitable for suppressing transient large power fluctuation. In this paper, the SMES is introduced to a DC MG to form a power regulation system. A voltage-based segmented (VBS) control is designed for the SMES-based power regulation system to suppress transient large power fluctuation in the DC MG. The voltage deviation caused by power distribution can be tolerant by VBS controlled SMES. Meanwhile, the dynamic recovery capability of the DC voltage is improved. The control method of SMES is independent of other devices in DC MGs, hence it is not dependent on communication. The control strategy of the SMES is further verified by simulation results.

A general framework for sliding cable analysis with elastic catenary equation

Sliding cables are widespread in engineering applications. Most of the existing sliding cable models are developed basing on conventional straight truss element, which is not applicable for many engineering applications where structures possess long-span and large sag effects. To effectively analyze this kind of system, this paper proposes a multi-node sliding catenary cable element. Due to the usage of analytic form of elastic catenary equation, the proposed element has the capability to accurately analyze both very taut and very sagged cables with minimum degrees of freedom. The formulation is developed within both dynamic relaxation approach and fully implicit approach. Effective numerical strategies in the nonlinear iteration, as well as the related tangent matrices are rigorously given. In particular, the multi-loop strategy permits to integrate the very complex nonlinear element into general finite element procedure, without needing to introduce any additional variable in the system. Multiple examples are presented to demonstrate the validity of the proposed framework. The numerical results also emphasize that sliding effects have a significate influence on the mechanical behavior of the catenary cable system, while can be easily addressed by using the methodology developed in this work.

Starting of induction motor fed with stand-alone DFIG

This paper presents dynamic simulation and control of stand-alone doubly fed induction generator (DFIG) loaded with 3-phase induction motors (IMs). The study reveals that direct on-line starting of large IMs causes a large voltage sag across the generator terminals as the starting current drawn reaches up to 8-9 times the rated load current. Traditionally, this problem has tackled by oversizing of the generator or employment of special starters, under the pretext of mitigating voltage sag. This work explores ways that the starting current can be reduced economically by applying constant V/f control side by side with indirect field-oriented control (FOC) applied on the rotor side converter of the DFIG. This methodology enables starting of larger IMs and mitigation of voltage sag that occurs during the start-up period. Two different rating of IMs loaded with speed-squared mechanical torque are mainly considered. Simulation results of the system behavior under study confirm the capability of the proposed control.

A giant lacustrine flood‐related turbidite system in the Triassic Ordos Basin, China: Sedimentary processes and depositional architecture

AbstractTurbidites have been regarded as an important sedimentary infilling component in both oceans and lakes, but limited studies have been performed on the mechanisms governing the initiation and development of lacustrine turbidite systems. The present study offers unique insight into the controls and potential extent of ancient lacustrine turbidite systems by an investigation of the Triassic Ordos Lake, where a large turbidite system had been traced across >25 653 km2. This article shows by comparison that the Triassic Ordos Lake turbidite system is larger than all known modern and ancient lacustrine counterparts. The exceptionally large intracontinental sag basin provided a relatively unconfined environment for the development of the turbidite system, explaining its vast extent. Extraordinary flood events formed during the Carnian Pluvial Episode facilitated continuous sediment supply into the turbidite system, supporting its accumulation. Lacustrine flood‐related turbidity currents travelled as sediment‐laden turbulent flows, showing an increase in the proportion of suspended‐load deposits and a decrease in the proportion of bed‐load deposits downstream from the river mouth. Five architectural elements have been revealed, reflecting a distinctive assemblage of erosional bedforms and depositional bedforms in channel‐lobe systems, and their recognition criteria were established. This study changes the traditional understanding of lacustrine turbidite systems, generally interpreted as having smaller sizes, and demonstrates likewise in the lacustrine realm, that extreme flood events can generate a world‐class deep‐water turbidite system, which can even be comparable with its submarine counterparts. This study also confirms that the combination of low‐gradient slopes and a long‐lived, mixed‐load, prograding fluvial feeder system can produce exceptionally large‐scale deep‐lake flood‐related turbidites. Furthermore, it has implications for the prediction of facies and reservoir quality in ancient lacustrine turbidite systems.

Parameter Optimization of Large Sag Mill Liner Based on DEM and Kriging Model

Parameter Optimization of Large Sag Mill Liner Based on DEM and Kriging Model

Lithospheric Strength and Rift Migration Controls on Synrift Stratigraphy and Breakup Unconformities at Rifted Margins: Examples From Numerical Models, the Atlantic and South China Sea Margins

AbstractSynrift stratigraphy and the distribution of breakup‐related erosional unconformities vary vastly between passive margins and cannot be explained by classical rifting models. Here we use numerical modeling to predict their spatiotemporal distribution. We show that synrift stratigraphy mimics rift architecture, which is controlled by lithospheric strength. Basinward rift migration during extension produces (1) oceanward younging, syntectonic and posttectonic sequences, (2) rift migration unconformities, RMUs, predating breakup, and (3) a breakup unconformity, BU, that only extends over the outermost margins, since breakup is not linked with a sudden stress drop. With small synrift sedimentation, the RMUs and BU laterally merge to form a margin‐wide unconformity. In symmetric, wide conjugate margins, which arise for weak lithospheres such as the South China Sea, a long phase of distributed deformation with little subsidence results in early synrift sediment over most of the margins. RMUs merge into a single event that marks the subsequent focusing of deformation into a narrow breakup area, which experiences short‐lived intense thinning and subsidence. In asymmetric conjugate margins, lateral rift migration transports shallowly deposited, early synrift sediments from the narrow to the wide, hyperextended margin, leading to a condensed syntectonic sequence and a single BU in the narrow margin and a series of RMUs in the wide one. For very weak lower crusts, lateral rift migration generates large synrift sag basins in the wide margin, as in Angola and Congo margins. Our models resemble the observed margins tectonic diversity and may be used as templates for interpreting their distal, unexplored areas.

Investigation on multi-body dynamics based approach to the toolpath generation for ultraprecision machining of freeform surfaces

This article presents an innovative approach to toolpath generation for ultraprecision machining of freeform optic surfaces based on the principle of Automatic Dynamics Analysis of Mechanical Systems. As components with freeform surfaces often have non-rotational symmetry, there are potential challenges facing their ultraprecision machining through single-point diamond turning, such as the projected points in complex large sag surfaces, which likely find it difficult to communicate with the control system and, thus, do not perform successfully. In ultraprecision machining, to achieve the highest performance in freeform surface resolution, the factors of dynamics, material and mechanical stiffness, frictions, tooling and accuracy of the servo component should be considered. The investigation is focused on an integrated approach and the associated scientific understanding of precision engineering design, ultraprecision machining and metrology of freeform surfaces as well as their application perspective. In this approach, the toolpath for very complex freeform surfaces can be generated using the Newton–Raphson method to solve the kinematics and dynamics equations of motion. The effect of friction and contact force are also investigated for accurate toolpath curve generation. Moreover, the Gear stiff (GSTIFF)/ Wielenga stiff (WSTIFF) integrator for solving the non-linear equations of motion is employed, and the result shows the time step size, playing a critical role in generating toolpath curves with a higher accuracy and resolution.

Chrna2-OLM interneurons display different membrane properties and h-current magnitude depending on dorsoventral location.

The hippocampus is an extended structure displaying heterogeneous anatomical cell layers along its dorsoventral axis. It is known that dorsal and ventral regions show different integrity when it comes to functionality, innervation, gene expression, and pyramidal cell properties. Still, whether hippocampal interneurons exhibit different properties along the dorsoventral axis is not known. Here, we report electrophysiological properties of dorsal and ventral oriens lacunosum moleculare (OLM) cells from coronal sections of the Chrna2-cre mouse line. We found dorsal OLM cells to exhibit a significantly more depolarized resting membrane potential compared to ventral OLM cells, while action potential properties were similar between the two groups. We found ventral OLM cells to show a higher initial firing frequency in response to depolarizing current injections but also to exhibit a higher spike-frequency adaptation than dorsal OLM cells. Additionally, dorsal OLM cells displayed large membrane sags in response to negative current injections correlating with our results showing that dorsal OLM cells have more hyperpolarization-activated current (Ih ) compared to ventral OLM cells. Immunohistochemical examination indicates the h-current to correspond to hyperpolarization-activated cyclic nucleotide-gated subunit 2 (HCN2) channels. Computational studies suggest that Ih in OLM cells is essential for theta oscillations in hippocampal circuits, and here we found dorsal OLM cells to present a higher membrane resonance frequency than ventral OLM cells. Thus, our results highlight regional differences in membrane properties between dorsal and ventral OLM cells allowing this interneuron to differently participate in the generation of hippocampal theta rhythms depending on spatial location along the dorsoventral axis of the hippocampus.

Impact of cable sag on the efficiency of an inertial mass damper in controlling stay cable vibrations

Passive negative stiffness dampers (NSDs) that possess superior energy dissipation abilities, have been proved to be more efficient than commonly adopted passive viscous dampers in controlling stay cable vibrations. Recently, inertial mass dampers (IMDs) have attracted extensive attentions since their properties are similar to NSDs. It has been theoretically predicted that superior supplemental damping can be generated for a taut cable with an IMD. This paper aims to theoretically investigate the impact of the cable sag on the efficiency of an IMD in controlling stay cable vibrations, and experimentally validate superior vibration mitigation performance of the IMD. Both the numerical and asymptotic solutions were obtained for an inclined sag cable with an IMD installed close to the cable end. Based on the asymptotic solution, the cable attainable maximum modal damping ratio and the corresponding optimal damping coefficient of the IMD were derived for a given inertial mass. An electromagnetic IMD (EIMD) with adjustable inertial mass was developed to investigate the effects of inertial mass and cable sag on the vibration mitigation performance of two model cables with different sags through series of first modal free vibration tests. The results show that the sag generally reduces the attainable first modal damping ratio of the cable with a passive viscous damper, while tends to increase the cable maximum attainable modal damping ratio provided by the IMD. The cable sag also decreases the optimum damping coefficient of the IMD when the inertial mass is less than its optimal value. The theoretically predicted first modal damping ratio of the cable with an IMD, taking into account the sag generally, agrees well with that identified from experimental results, while it will be significantly overestimated with a taut-cable model, especially for the cable with large sag.

Measurement and Analysis of the Stepwise Curved Surface of Diffractive Optical Elements by a Constant Speed Confocal Probe

Diffractive optical elements (DOEs) play an important role in improving imaging quality and reducing system volume. The measurement of DOE surface topography is of great significance to the evaluation of DOE quality and the optimization of its manufacturing process. However, there are still some difficulties in measuring the large curvature and the large sag of curve-based DOEs. In this paper, considering the geometrical feature information and measurement problems of curve-based DOEs, a measurement method based on a confocal measurement principle for DOE measurement is proposed. The proposed measurement data processing method is verified by a high-precision motion axis system and the stability of an ultra-precision lathe. The results show that the proposed measurement method can reconstruct and accurately evaluate the three-dimensional surface topography of DOEs.

Post-Buckling Analysis of a Uniform Self-Weight Beam with Application to Catenary Riser

This paper focused on a simply supported beam under uniform self-weight, subjected to an axial force at the roller end. The principle of virtual work-energy was used to formulate the equation for the nonlinear deformation of the beam, which involves the bending strain energy, the virtual work due to self-weight, and the virtual work of the axial force applied at the free-sliding roller end. The work–energy functional was expressed in terms of the arc-length coordinate. The functional vanished, yielding the static equilibrium configuration of the beam — a highly nonlinear problem. Finite element and Newton–Raphson iterative methods were used to solve the problem. The beam theory was extended to large sag analysis of a catenary riser. With this, some interesting features of the various configurations of the catenary riser under various end forces were evaluated.

Reservoir forming conditions and key exploration technologies of Lingshui 17-2 giant gas field in deepwater area of Qiongdongnan Basin

On September 15, 2014, China National Offshore Oil Co., Ltd announced that a high production of oil and gas flow of 1.6 × 106 m3/d was obtained in Well LS17-2-1 in deepwater area in northern South China Sea, which is the first great oil and gas discovery for self-run deepwater exploration in China sea areas, and a strategic breakthrough was made in natural gas exploration in deepwater area of Lingshui sag in Qiongdongnan Basin. Under the combined action of climax of international deepwater exploration, high oil prices, national demands of China, practical needs of exploration, breakthroughs in seismic exploration and testing technologies, innovations in geological cognition and breakthroughs in deepwater operation equipment, Lingshui 17-2 gas field is discovered. Among these factors, the innovation in reservoir forming geological cognition directly promotes the discovery. The quality of seismic data in the early time is poor, so key reservoir forming conditions such as effective source rocks, high quality reservoirs and oil-gas migration pathways are unable to be ascertained; with support of new seismic acquisition and processing technology, some researches show that Lingshui sag is a successive large and deep sag with an area of 5000 km2 and the maximum thickness of Cenozoic stratum of 13 km. In the Early Oligocene, the Lingshui sag was a semi-closed delta-estuarine environment, where the coal-measure and marine mudstones in Lower Oligocene Yacheng Formation were developed. The Lingshui sag is a sag with high temperature, and the bottom temperature of source rocks in Yacheng Formation can exceed 250 °C, but the simulation experiment of hydrocarbon generation at high temperature indicates that the main part of this set of source rock is still in the gas-generation window, with resources of nearly 1 trillion cubic meters, so the Lingshui sag is a hydrocarbon-rich generation sag. In the Neogene, the axial canyon channel from the Thu Bon River in Vietnam passed through the Lingshui sag, and five stages of secondary channels were developed in the axial canyon channel, where four types of reservoirs with excellent physical properties including the axial sand, lateral accretion sand, natural levee sand as well as erosion residual sand were developed, and lithologic traps or structural-lithologic traps were formed. The diapiric zone in the southern Lingshui sag connects deep source rocks in Yacheng Formation and shallow sandstones in the channels, and the migration pattern of natural gas is a T-type migration pattern, in other words, the natural gas generated from Yacheng Formation migrates vertically to the interior of the channel sandbody, and then migrates laterally in the channel reservoirs and forms the reservoirs. Innovations of geophysical exploration technologies for complicated geological conditions of deepwater areas are made, such as the detuning comprehensive quantitative amplitude hydrocarbon detection technology, which greatly improves the success rate of deepwater exploration; key technologies of deepwater safety exploratory well testing represented by the platform-dragged riser displacement technology are developed, which greatly reduces the drilling test cost. The above key exploration technologies provide a strong guarantee for the efficient exploration and development of Lingshui gas field.