Sequence Stratigraphic Division Research Articles

Sequence Stratigraphic Analysis of the Volcanic Rock–Evaporite–Clastic Rock Symbiotic Zone in the Fourth Member of the Shahejie Formation in the South of Laizhou Bay

Laizhou Bay Sag is a typical continental rift lake basin, which is affected by strike–slip activity, salt rock activity, volcanic activity, and paleoclimate change in the Tanlu fault zone, where three major lithologies—volcanic rock, clastic rock, and evaporite—mainly develop. In order to determine the sequence correspondence between the different lithologies in the study area based on drilling, logging data, and seismic data, it is determined that the fourth member of the Shahejie Formation in the southern Laizhou Bay mainly develops three types of sequences: clastic rock type sequences, salt lake type sequences, and volcanic rock/clastic rock type sequences. Two second-order sequence boundaries (SBs3L, SBs4L) and one third-order sequence boundary (SBs4U) were identified, and the principle of three divisions of system tracts (LST, TST, HST) and sedimentary processes in different types of sequences were determined by analyzing the stacking patterns of different sequences. Compared with the previous research results, this study provides a more detailed analysis of the sequence boundary definition of different blocks and different lithologic strata, and it improves the previous general sequence stratigraphic division method. Based on the study of distinct types of sequences, a unified stratigraphic framework is established in the whole zone, and the stratum thickness distribution of the fourth member of Shahejie Formation is smaller in the southwest and larger in the northeast. The study area is generally filled with pyroclastic rocks–evaporite–clastic rocks, changing from fan delta–saline lake filling to braided river delta–freshwater lake–fan delta filling from bottom to top. A sequence stratigraphic model for the comparison of steep slope–gentle slope differences is established to provide guidance for future oil and gas field exploration and development.

Sedimentary facies, lithofacies paleogeography, and an evaluation of the Ordovician sequences in the Sichuan Basin, southwest China

Ordovician strata in the Sichuan Basin occur in formations of varying thicknesses. Deposited in intracratonic and craton margin depressions of the Yangtze Block, these strata are rarely exposed in the basin with poorly described facies types and multiple controversies in sequence stratigraphy, which can lead to inaccurate interpretations of depositional settings and paleogeography. We studied outcrops, samples, and thin sections, and conducted interpretations of the environment of deposition and sequence stratigraphy as well as the lithofacies paleogeographic characteristics of different depositional stages of Ordovician units. Macroscopic facies (08) and their associated microfacies (14) were identified from outcrops and thin sections. The depositional environments of the carbonate rocks were interpreted using the standard microfacies types (SMF) of Flügel (2010) as a reference. The Ordovician units in the Sichuan Basin were divided into three 2nd-order sequences, including two complete cycles (SSQ1 and SSQ2) and one semi-cycle (SSQ3), and further subdivided into ten 3rd-order sequences (SQ1-SQ10). Ordovician units were partitioned into seven formations: the Tongzi, Honghuayuan, Meitan, Shizipu, Baota-Linxiang, and Wufeng formations. Based on the variation characteristics of the carbon-13 isotope (δ13C) curve, two large cycles of sea-level rise and fall were detected in the study area. An extensional rifting event occurred in the basin during the first cycle (Lower Tongzi Formation to Early/Middle Meitan Formation). The basin was in a compressive stage during the second cycle (Late Meitan Formation to Late Wufeng Formation). The Early Ordovician Tongzi and Honghuayuan formations were deposited in shallow water. During the deposition of these units, shoal facies occurred in the platform margin. Afterward, rimmed carbonate platforms occurred in the platform margin with a fauna mainly composed of brachiopods, echinoderms, trilobites, bryozoans, and algae. The Middle Ordovician Meitan Formation is characterized by increased clastic components deposited in continental shelf environments with graptolite and trilobite fossils. The Late Ordovician Baota Formation is marked by the development of slope facies deposited in carbonate ramp environments with cephalopod and trilobite fragments. The Late Ordovician Wufeng Formation was deposited in deep water shelf settings characterized by graptolite fossils. Tectonic activities and relative sea-level change mainly controlled the paleogeographic pattern and the evolution of the Sichuan Basin. The results presented in this study provide valuable insights and fill a significant gap in facies analysis, sequence stratigraphic division, and paleogeography of Ordovician units in the Sichuan Basin.

Channel Evolution under the Control of Base-Level Cycle Change and the Influence on the Sustainable Development of the Remaining Oil—A Case in Jiang Ling Depression, Jiang Han Basin, China

The extension of river channels is one of the key factors in determining the remaining oil distribution. Different sedimentary facies and bedding types of oil layers will form specific characteristics of remaining oil distribution after water injection development. Using massive drilling, core, logging, seismic, and production data, on the basis of sequence stratigraphy base-level cycle change, the river records and development history are restored, and the fine connectivity of reservoirs and the configuration relationship of production wells are studied. The following conclusions are drawn: (1) A sequence stratigraphic division scheme is established. In the established sequence framework, the types and characteristics of reservoir sand bodies are analyzed. The 2nd and 6th members of Yu yang formation can be divided into 2 long-term base level cycles, 5 medium-term base level cycles, and 17 short-term base level cycles. The evolution of the second and sixth members of the Yu yang formation shows a pattern of base level rising, falling and rising again; (2) the vertical sedimentary evolution sequence is underwater distributary channel distributary channel meandering channel distributary channel flood plain. The types of channel sand bodies developed from little overlap to more vertical or lateral overlap and then gradually changed to isolated type; (3) according to the structural location and development sequence, different types of reservoirs are identified. Combined with the statistics of the drilled data of Yu yang formation k2y4 in Fu I fault block, it is found that the connectivity rate of oil layer thickness (the ratio of oil layer connectivity thickness to total thickness of sand layer) within the oil-bearing area is 84.4%, and the connectivity rate of the number of layers (8) is 60%. The connectivity condition is relatively good.

The Sequence Stratigraphic Division and Depositional Environment of the Jurassic Yan’an Formation in the Pengyang Area, Southwestern Margin of the Ordos Basin, China

Coal and organic-rich shale in the Yan’an Formation in the southwestern margin of the Ordos Basin are widely developed, which is an important fact for oil and gas exploration in China that has been widely explored for a long time. In this paper, detailed sequence division and sedimentary environment analyses of the Yan’an Formation in the Pengyang area on the southwestern margin of the Ordos Basin were conducted using field outcrops, drilling cores, logging, wavelet transform and organic geochemistry. The results showed that the succession consists of some units with distinctly different characteristics. Based on the petrographic assemblage and transform wavelet characteristics, the Yan’an Formation in this area can be divided into a long-term cycle, five medium-term cycles, and eleven short-term cycles, among which coal and carbonaceous shale were mainly developed in the short-term cycles I2, III1, III2, V1 and V2. Coal and organic-rich mud shale have been developed in the Yan’an Formation and plant debris in mudstone and coal is common, indicating the development of swamps and shallow water-covered depressions in this area. The sandstones showed parallel bedding, cross-bedding and scours, thus indicating fluvial deposits. The saturated hydrocarbon gas chromatographic parameters of mud shale showed that the pristane/phytane (Pr/Ph) ratio is 2.24–6.22, the Ph/nC18 ratio is 0.15–0.93, and the Pr/nC17 ratio is 0.97–2.78, supporting the finding that the organic matter has mainly originated from terrestrial sources.

Early and middle Jurassic sequence stratigraphic division of M coalfield in Xinjiang

The coal accumulation in the M coalfield occurred in the Early-Middle Jurassic. There are three main coal-bearing strata in the M coalfield, the Early Jurassic Talicike Formation, the Yangxia Formation and the Middle Jurassic Kizilenur Formation. Based on the sequence stratigraphic division and sedimentary environment analysis of 85 Jurassic wells in the Kubai Basin, and the compilation of sequence stratigraphic correlation profiles for 20 well-connected wells, this paper comprehensively studies the drilling, logging, outcrop, core and paleontological data. This paper establishes the isochronous sequence stratigraphic correlation framework of the Jurassic in the Kubai Basin with third-order sequences as units. Finally, this paper studies the sequence stratigraphic characteristics and lithofacies paleogeography of each Jurassic sequence in the M coalfield.

Intelligent identification of sequence stratigraphy constrained by multipopulation genetic algorithm and dynamic time warping technique: A case study of Lower Cretaceous Qingshuihe Formation in hinterland of Junggar Basin (NW China)

AbstractThe division and correlation of sequence stratigraphy are one of the essential steps in petroleum exploration. To comprehensively utilize the sequence stratigraphic information implied in multiple wireline well logs and improve the accuracy and reliability of sequence stratigraphic division, based on the edge detection, optimal partition, and natural evolution theories, and realizes the information fusion (formed one ‘chromosome’) of multiple wireline well logs (named as ‘genes’) which can reflect the feature information of sequence stratigraphy by using multipopulation genetic algorithm (MPGA) based on Fisher algorithm, in this study, geophysical data (wireline well logs and 3D seismic data) were used for spectral trend attribute analyses (wavelet transform, maximum entropy spectrum, time‐frequency analyses, and integrated prediction error filter). Since the seismic reflection characteristics of K1q were difficult to identify and considering subjective factors in conventional methods, a MPGA was also used to intelligently identify the sequence stratigraphy framework of the Lower Cretaceous Qingshuihe (K1q) Formation. Since the MPGA is an optimization algorithm, the code was run 10 times for accuracy with changes in the dividing layers. The optimal parameters in the process of data fusion (gene combination process) are selected. The sequence boundaries (SBs) searched by the MPGA matched those of the spectral trend attribute analyses, confirming that the MPGA was an effective, fast, and user‐friendly tool for defining the main SBs. MPGA can provide an optimal layering scheme (‘elite population’) through simultaneous searching at multiple depth ranges (‘multipopulation’), recording the optimal SBs (‘elite individuals’) of each population and making the results more convinced. Although simulation solutions may not be unique, the MPGA still provides us a chance to gain some insights into the details of the stratigraphy. Based on this intelligent identification, the maximum flooding surface, two first flooding surfaces (FFS), and three SBs were defined in K1q. The cyclic patterns (prograding, aggrading, and retrograding) were identified. They showed the relationship between accommodation space (related to tectonic subsidence of the Chemo paleo‐uplift) and sediment supply. In addition, dynamic time warping (DWT) technique was used for sequence discrimination and correlation on the integrated prediction error filter analyses curve. A massive pebbly sandstone set, named ‘bottom sandstone,’ was identified in the lowstand system tract of SQ1 (K1q1), constrained by SB1 and FFS1, which was a favourable hydrocarbon exploration target.

Sequence stratigraphic division of the Shisanlitai Formation of Neoproterozoic in Southern Liaoning, China

Sequence stratigraphy is the most important prediction theory in the field of petroleum exploration, and is hailed as a theoretical revolution in geology. At present, countries around the world have begun to pay attention to the study of marine carbonate rocks. The Shisanlitai Formation in Dalian, Liaoning is an important Neoproterozoic stratum in China, with a large number of carbonate rocks. Through comprehensive analysis of the field measured profiles, the sequence stratigraphy of the Shisanlitai Formation was studied. A total of 4 sequence boundary were identified, and 3 sequence, 7 para-sequence sets and 20 para-sequences were divided. It is considered that the Shisanlitai Formation is a platform marginal sedimentary facies. The regional geotectonic and astronomical cyclic methods are used to discuss the environmental evolution of the Ganjingzi Formation. Platform marginal beach → platform marginal slope → platform marginal reef evolution process, and summarized that there were 4 short exposures from the end of the Majiatun period to the Shisanlitai Formation period in the Dalian area affected by the low-amplitude tectonic ups and downs in the late Yangtze cycle 4 sequence boundary and 3 sequences are formed. Through comprehensive and systematic analysis of the sequence stratigraphy and sedimentary evolution of the Shisanlitai Formation, it provides a basis for exploring the oil and gas resources in southeastern Liaoning.

High Resolution Sequence Stratigraphic Division and Isochronous Framework Establishment in Wuerxun-baer Sag

High-resolution sequence stratigraphy and related technical methods have been widely used in the analysis of complex and changeable continental petroliferous basins in China in recent years. At present, the main fields of oil and gas exploration in Hailaer Basin have been transferred to lithologic reservoirs, so it is very important to find lithologic traps and analyze the favorable formation conditions of lithologic traps. The tectonic evolution, sequence stratigraphic framework and tectonic control over the sedimentary system of Nantun Formation have been studied in depth by predecessors. However, the division accuracy of Nantun Formation can only reach the level of system tract, and the distribution characteristics of sand bodies and source-reservoir allocation under high-resolution sequence framework are seldom studied. Therefore, on the basis of predecessors’research, the author synthetically uses the related technology and methods of high-resolution sequence stratigraphy, and according to the sequence boundary characteristics reflected by drilling, core, seismic and logging data, establishes the high-resolution sequence stratigraphic framework through fine division and correlation of base-level cycles at various levels. The distribution law of sand body under its control and the source-reservoir allocation relationship favorable to lithologic trap formation are studied in order to have important guiding significance for further tapping the potential of lithologic reservoir.

Sedimentary facies and sequence stratigraphy in the Lower Triassic Jialingjiang Formation, Sichuan Basin, China

The Lower Triassic Jialingjiang Formation is an important oil and gas exploration target in the Sichuan Basin. The lithofacies mainly consists of clastic rocks, carbonates, and evaporates, which represents a transition from continental to marine depositional environment. The Jialingjiang Formation of the Sichuan Basin is a typical epeiric carbonate platforms. The study area contains four types of facies, including mixed tidal flat facies, open platform facies, restricted platform facies, and evaporitic platform facies. Based on the analysis of cores and logging data, two types of type II sequence boundaries were identified, which are, respectively, local exposure unconformity boundary and lithology and lithofacies transformation boundary. The Jialingjiang Formation is divided into three third-order sequences and six system tracts. Thus, we establish a connected multi-well sequence stratigraphic framework based on typical single-well sequence stratigraphic division. The sedimentary evolution of the Jialingjiang Formation was divided into three major sedimentary periods and six stages, with rising and falling of the sea level, mixed tidal flat, open platform, and restricted platform prograded first, and then restricted platform and evaporitic platform retrograded. It also shows that the open platform shoal and restricted platform tidal flat have oolitic limestone and algal dolomite with good-quality physical properties and are the favorable reservoir facies belt for hydrocarbon exploration and development.

An application of sedimentation simulation in Tahe oilfield

The braided river delta develops in Triassic low oil formation in the block 9 of Tahe oilfield, but its sedimentation evolution process is unclear. By using sedimentation simulation technology, sedimentation process and distribution of braided river delta are studied based on the geological parameters including sequence stratigraphic division, initial sedimentation environment, relative lake level change and accommodation change, source supply and sedimentary transport pattern. The simulation result shows that the error rate between strata thickness of simulation and actual strata thickness is small, and the single well analysis result of simulation is highly consistent with the actual analysis, which can prove that the model is reliable. The study area belongs to braided river delta retrogradation evolution process, which provides favorable basis for fine reservoir description and prediction.

Characteristics of Sedimentation Evolution Based on the Sequence Stratigraphic Frameworks in Shahezi Formation of Southern Xujiweizi Fault Depression

Many scholars in China introduced the theory of sequence stratigraphy,applying to Chinese continental fault depression lake, they have made a lot of achievements in scientific research. However, there are still a lot of controversy according to the establishment in Shahezi group of sequence stratigraphic framework in Xujiaweizi fault depression.Sequence boundary identification method in this paper is based on the “instruction of Vail’s sequence stratigraphy theory, identification of seismic unconformity, verification by using logging methords”. And, following the principle of isochronous ,sequence stratigraphic framework of this region is established clearly. The southern Xujiaweizi fault depression in Shahezi group is divided into 1 second grade sequence, in the interior distributed SQ1-SQ4 4 third grade sequences from the bottom. Developmental stages at the bottom of SQ1 and the top of SQ4, basin is small and water is shallow. However, Developmental stages in SQ2 and SQ3,water enters the lake basin continuously, formed a sedimentary background of “wide basin and deep water”. In addition, each of the three grade sequence has split structure, the lake transgressive domain and lake regression domain two system tracts. Besides, the reversed order para-sequence sets caused by the lake regression and progradation set on the positive para-sequence sets caused by the lake transgression and retrogradation. On the basis of sequence stratigraphic division and correlation, conbined with the regional construction and the supply of provenance ,the sedimentary sequence framework of evolution characteristics are studied.That fan delta,braided river delta, lacustrine are the main facies types in study area. Characteristics of sedimentary evolution there are like this: the characteristics of sedimentation evolution show framework controls sand, succession of evolution, separated-source sedimentary, contiguously distribution.

葡西油田葡萄花油层高分辨率层序地层格架建立

随着勘探开发过程的不断深入，对沉积时间单元划分的精细程度也要求越来越高，长时间尺度的层序地层划分已经不足以满足油田的开发需求，而高分辨率层序地层格架的研究方法具有高度精细和准确的特征，是层序地层学的新发展方向。结合测井、岩心、地震和露头等资料，明确高分辨率层序地层格架的划分原则并且给出合理划分方案，建立封闭骨架剖面，由标准井出发，首先完成骨干剖面上井的层位对比，再把非骨干剖面井对比到与其相邻的骨干剖面井上，这样既保证了全区对比具有统一的标准，又确保了对比的精细程度。 As the exploration and development deepening, the requirement on the classificational accuracy of deposition time units becomes higher and higher, and the sequence stratigraphic division of long-time scales is not enough to meet the demand of development. But the research methods of high-resolution sequence stratigraphic framework have highly detailed and accurate characteristics, so it is a new developing direction of sequence stratigraphy. Combining logging, core, seismic and outcrop data, clearing the classification principles of high-resolution sequence stratigraphic framework and giving a reasonable plan, close skeleton section is established. From the standard well, firstly the strata contrast of the wells in backbone profile is accomplished, and then the wells out of backbone and the backbone of the adjacent sections are compared. This method not only ensures a unified standard of the contrast in the region, but also ensures the high resolution of the contrast.

Application of Wavelet Transform in High-Resolution Sequence Stratigraphic Division

In this paper, the method and effect of logging curves wavelet transform in high-resolution sequence division are discussed, taking the middle oil sequence stratigraphic of DU-432 oil well in north-Songliao basin as an example. Using Wavelet Transform to GR logging curves, the relationship between logging curve signals and depth is transformed to the relationship between the depth and the scale domain, so that the wavelet curves in different scale are obtained. Then the relationship between the periodic oscillation characteristics of the wavelet curves under the best optimal scale factor and the sequence. Comparing the Sequence Stratigraphic Division by wavelet transform with the manual division, Results show that the Division by Sequence Stratigraphic wavelet transform is more objective and more effective and the Division provides a new way to high-resolution sequence stratigraphy.

High-Resolution Sequence Stratigraphic Division and Monosandbody Isochronic Correlation of Meandering River Delta of Fuyu Oil Layer in the Northern Honggang

By using the cores, drilling and logging data, Fuyu oil layer in the northern Honggang is divided into 2 long-term base level cycle, 4 medium-term base level cycles, 20 short-term base level cycles, and monosandbody high-resolution sequence strata framework is established, monosandbody isochronic correlation is achieved in Isochronic strata framework at the same time. Through high--resolution sequence stratigraphic analysis, sedimentary evolution, monosandbody distribution, sand geometry and distribution characteristics of reservoir are controlled by base-level changes in Fuyu oil layer of the northern Honggang. The lower Fuyu oil layer is dereliction prograding sequence stratigraphic modes in fall range of base-level. Space stacked form of the sand body is controlled by A/S ratio or base level changes. The symmetry of cyclic changes with the geographical location and distance from the sedimentary source.

High-resolution sequence stratigraphic division and distribution of tidal deposits in the Zhuhai Formation, Huizhou Sag, Pearl River Mouth Basin, South China Sea

AbstractThe Zhuhai Formation of the Huizhou Oilfield has been interpreted as being deposited in a tide-dominated estuarine setting. This paper uses stratigraphic principles, cores and logging data to analyse the facies changes of tidal sedimentation in response to the base level cycle. We conclude that the mud flat progradational allocycle is the result of a long-term base level fall, while the fining-upwards autocycle is in response to a short-term base level fall. Region-wide mud layers of supratidal zones and scour surfaces of subtidal zones are stratigraphic surfaces of tidal sedimentation. By integrating high-resolution stratigraphic correlations with seismic attributes extracted from the stratal slicing of 3-D data volumes, we use an attribute map of RMS (root mean square) amplitude to image the distribution and evolution of tidal deposits in the study area. Intertidal zones and the upper parts of the tidal cycle are favourable areas for prospecting and oil reserves and thus provide a basis for petroleum exploration and development.

Seismic sequence and depositional evolution of slope basins in mid-northern margin of the South China Sea

As one of the biggest marginal seas in the western Pacific margin, the South China Sea (SCS) experienced continental rifting and seafloor spreading during the Cenozoic. The northern continental margin of the SCS is classified as a passive continental margin. However, its depositional and structural evolution remains controversial, especially in the deep slope area. The lack of data hindered the correlation between continental shelf and oceanic basin, and prevented the establishment of sequence stratigraphic frame of the whole margin. The slope basins in the mid-northern margin of SCS developed in the Cenozoic; the sediments and basin infill recorded the geological history of the continental margin and the SCS spreading. Using multi-channel seismic dataset acquired in three survey cruises during 1987 to 2004, combined with the data of ODP Leg 184 core and industrial wells, we carried out the sequence stratigraphic division and correlation of the Cenozoic in the middle-northern margin of SCS with seismic profiles and sedimentary facies. We interpreted the seismic reflection properties including continuity, amplitude, frequency, reflection terminals, and 15 sequence boundaries of the Cenozoic in the study area, and correlated the well data in geological age. The depositional environment changed from river and lake, shallow bay to open-deep sea, in correspondence to tectonic events of syn-rifting, early drifting, and late drifting stages of basin evolution.

Sequence Stratigraphic Division and Associated Cement Distribution: Upper Jurassic Fulmar Formation, Central North Sea, UKCS: ABSTRACT

The Fulmar Formation is an important reservoir interval in the Central North Sea, UCKS. Because of the highly bioturbated nature of the sediments, primary sedimentary structures are rare. This has limited previous sequence stratigraphic interpretations. Detailed and integrated ichnofabric analysis allows the development of a superior sequence stratigraphic interpretation in which a relatively predictable distribution of early diagenetic cements is observed. Within the cored intervals examined, five recurring ichnofabric associations are recognized, and these reflect a range of environments, from offshore transition to lower shoreface. In the two fields studied, a series of sharp-based sandstones are recognized. Analysis of the ichnofabrics associated with these sharp-based sandstones indicates an abrupt shallowing, typically with a change from offshore transition to a proximal lower shoreface environment. The base of each sandstone is marked by an erosional surface commonly with a shell/pebble lag. A common ichnofabric expression of such an abrupt shoaling is the superimposition of clean sandstones with Ophiomorpha on silty sandstones with Cylindrichnus. Internally, the sandstones display a progradational stacking pattern. Ichnofabric analysis therefore suggests that these abrupt basinward shifts in facies represent deposition in response to punctuated falling sea-level i.e. forced regression. Within this sequence stratigraphic framework, abundant carbonate and pyritemore » cements are observed. Although the sedimentological relationship of these cements is unclear, their distribution is relatively systematic, being best developed at the tops of parasequences. This evidence suggests that they are related to minor flooding surfaces, and has important implications for predicting reservoir heterogeneity.« less