Sequence Stratigraphy Theory Research Articles

Cycles of fine-grained sedimentation and their influences on organic matter distribution in the second member of Paleogene Kongdian Formation in Cangdong Sag, Bohai Bay Basin, East China

According to the theory of sequence stratigraphy based on continental transgressive-regressive (T-R) cycles, a 500 m continuous core taken from the second member of Kongdian Formation (Kong 2 Member) of Paleogene in Well G108-8 in the Cangdong Sag, Bohai Bay Basin, was tested and analyzed to clarify the high-frequency cycles of deep-water fine-grained sedimentary rocks in lacustrine basins. A logging vectorgraph in red pattern was plotted, and then a sequence stratigraphic framework with five-order high-frequency cycles was formed for the fine-grained sedimentary rocks in the Kong 2 Member. The high-frequency cycles of fine-grained sedimentary rocks were characterized by using different methods and at different scales. It is found that the fifth-order T cycles record a high content of terrigenous clastic minerals, a low paleosalinity, a relatively humid paleoclimate and a high density of laminae, while the fifth-order R cycles display a high content of carbonate minerals, a high paleosalinity, a dry paleoclimate and a low density of laminae. The changes in high-frequency cycles controlled the abundance and type of organic matter. The T cycles exhibit relatively high TOC and abundant endogenous organic matters in water in addition to terrigenous organic matters, implying a high primary productivity of lake for the generation and enrichment of shale oil.

High frequency sequence stratigraphic framework and sedimentary characteristics of P oil layer in the southern part of A area

Based on the high resolution sequence stratigraphy theory, 42 wells and 2745 well logging curves are used to study the evolution of all levels of base level cycles and the development pattern of high-resolution sequence in the P reservoir in the southern part of Songfangtun area. The results show that the 4 sequence interface of the grape flower beds in the Songfangtun area can be divided into 2 medium-term, 5 short term and 12 ultra short term sequences. On this basis, the sedimentary microfacies type and distribution evolution law have been carried out. It is considered that the shallow water delta depositional system is developed in P reservoir in the Songfangtun area. The main development of delta front subfacies is to identify 8 kinds of microfacies such as subwater distributary channel, inter channel, inter channel, slime, overflow sand, mouth fan, estuarine dam, far sand bar and mat sand. The underwater distributary channel sandbodies are widely developed at the front of the delta. Due to frequent bifurcations and diversions, the underwater distributary channel sandbodies cut and overlap each other, forming branches and striped sand bodies. The sandbody reservoir has good physical property and is the main reservoir sand body with oil and gas enrichment. The detailed study of sedimentary microfacies provides a reference for further exploration and development of lithologic reservoirs in this area.

Development characteristics of the third-order sequence of Upper Devonian–Lower Carboniferous shore-mixed shelf in Tarim Basin, NW China

Based on the study of stratigraphic sedimentary facies of the prototype sedimentary basin formed in the Late Devonian to Permian Period in the Tarim Basin, the prototype sedimentary basin are divided into five order sequences according to the theory of sequence stratigraphy. It is considered that the Upper Devonian–Lower Carboniferous shore-mixing shelf in the lower part of the prototype sedimentary basin is a typical third-order sequence and a sequence development model is established. The third-order sequence is actually a transgression systems tract and highstand systems tract cycle assemblage, and the type I sequence (no lowstand systems tract) is a typical developmental mode of the third order sequence, and the identification mark is the existence of huge mudstone and limestone wedges from sea to land. The fifth-order parasequence is the basic sequence, which is a single cycle sequence. The thin layer limestone isochronous sediments, which are easy to be identified in the mixed shelf areas, are the isochronous sediments of the largest or secondary marine-flooding surface. The mixed shelf area belongs to the equilibrium sedimentary profile of internal and external sediments, and there is no condensed section. The inclined deposition phenomenon of extraneous source sediments in the sea area weakens or disappears in the mixed shelf area. The paleogeomorphology at the bottom of the third-order sequence is a terrace-slope break zone. This paleogeomorphological feature is not only the main reason for the sedimentary diachronism of Donghe sandstone, but also the main reason for the formation of the transgression-highstand fourth-order cyclic sequences of the Donghe sandstone section and its upper gravel-bearing sandstone section.

Sequence Division and Sedimentary characteristics of Shahezi formation in Northwest Xujiaweizi fault depression

In the light of the unclear current conditions of the sequence stratigraphic framework division and sedimentary for Shahezi Formation in Northwest Xujiaweizi fault depression. Based on single well, well logging and seismic data,the stratigraphic sequences of the formatio n are confirmed with the help of Vail sequence stratigraphy theory. Based on the single well facies and source supply, the sedimentary facies types and the distribution characteristics of the Northwest of Xujiaweizi are analyzed. The studies show that Northwest Shahezi Formation can be divided into one second-class sequences and furthermore it can be classified into four third-class sequence; Fan delta sedimentary facies is developed in the west of study area, braided river delta sedimentary facies is developed in the east of study area, lacustrine facies is developed in the central sag; In the Northwest of the Shahezi formation, the area of the lake basin in the early stage of the sedimentary basin is small, and the latter is gradually enlarged, lake facies is the main one and the fan is mainly developed in the East and the West in this area.

Sedimentary Characteristics and Lithological Trap Identification of Distant Braided Delta Deposits: A Case on Upper Cretaceous Yogou Formation of Termit Basin, Niger

Lithological trap identification in thin sand and thick shale layers is still a challenge for hydrocarbon exploration. Based on the high-resolution sequence stratigraphy theory and the establishment of high resolution sequence stratigraphy framework with seismic-well tie, the dynamic deposition process of braided river delta sands on late Cretaceous Yogou formation has been analyzed on 62 wells in passive rift Termit basin with multi-stages depressions and reversals. (1) Six kinds of sedimentary microfacies and three major reservoir sands with multi-stages stacking and lateral migration are in Yogou formation; (2) Based on Accommodation space/Sediments supply change and the deposition progress, sedimentary facies distribution in each member of YS3 sub-formation has been done according to sands thickness statistics of sedimentary micro-facies, narrow-time seismic attributes and slices analysis, multi-sources braided river delta depositional model has been concluded; (3) Based on source rock and caprock evaluation, with reservoir sands distribution and faults impact on Yogou formation of Termit basin, four types of traps, including structure-lithology, Structure-strata, stratigraphic and lithology are concluded. Traps influencing factors, i.e., structure geometry, sands distribution, paleotopography, stratigraphy cycling, sand/shale lateral connection, reservoir quality and so on, have different impacts on these traps, and different lithologic-stratigraphy traps have different exploration risks. Structure geometry and sands distribution are very important for the structure-lithology traps; structure geometry and paleotopography are the key factors in Structure-strata traps. Sands distribution and reservoir quality can be focused on lithology traps. Moreover, paleotopography and sand/shale lateral connection are significant on stratigraphic traps. Therefore, different hydrocarbon accumulation types of lithological traps have been established.

Sedimentary Characteristics and Lithological Trap Identification of Distant Braided Delta Deposits: A Case on Upper Cretaceous Yogou Formation of Termit Basin, Niger

Lithological trap identification in thin sand and thick shale layers is still a challenge for hydrocarbon exploration. Based on the high-resolution sequence stratigraphy theory and the establishment of high-resolution sequence stratigraphy framework with seismic-well tie, the dynamic deposition process of braided delta sands on late Cretaceous Yogou formation has been analyzed on 62 wells in passive rifting Termit basin with multi-stages depressions and reversals. (1) Six kinds of sedimentary microfacies and three major reservoir sands with multi-stages vertical stacking and lateral migration are in late Cretaceous; (2) Based on accommodation space/Sediments supply change and depositional progress, sedimentary facies distribution evolution has been done according to sands thickness statistics of sedimentary micro-facies, and narrow-time seismic attributes and slices analysis, multi-sources braided delta depositional model has been concluded; (3) Based on source rock and caprock evaluation, with reservoir sands distribution and faults impact on Yogou formation of Termit basin, four types of traps, including structure-lithology, Structure-strata, stratigraphic and lithology are concluded. Traps influencing factors, i.e., structure geometry, sands distribution, paleotopography, stratigraphy cycling, sand/shale lateral connection, reservoir quality and so on, have different impacts on these traps, and different lithologic-stratigraphy traps have different exploration risks. Structure geometry and sands distribution are very important for the structure-lithology traps; structure geometry and paleotopography are the key factors in Structure-strata traps. Sands distribution and reservoir quality can be focused on lithology traps. Moreover, paleotopography and sand/shale lateral connection are significant on stratigraphic traps. Therefore, different hydrocarbon accumulation types of lithological traps have been established.

Characteristics of tidal action sedimentary system and distribution of favorable sand bodies of Silurian in Tazhong area, Tarim basin, NW China

The 3rd upper sub-member of the Silurian Kepingtage formation has developed marine clastic sediments and is an important petroleum exploration and development set in Tazhong area, Tarim basin, NW China, of which the sedimentary system and favorable reservoir distribution have been researched in detail based on the drilling, logging, seismic, experimental data and the theory of sequence stratigraphy. The results show that it was overlap and edge away layer by layer from northwest to southeast. On the background of marine transgression, the depositional systems of tidal flat, estuary and tidal reformation delta were developed and controlled by palaeogeomorphology, while different types of sand bodies and sedimentary formations were developed owing to the difference of types and energies of main action water bodies. In the sedimentary system of tidal flat, the main types of sand bodies are subtidal tidal channels which show significantly banded distribution vertical to the coast with a complete three-tier structure. The sand bodies of tidal bars are common in the estuary sedimentary system and extend far parallel to the axis of the estuary with thin layers of mudstone. The sand bodies of underwater distributary channels are developed with upward-finning positive rhythm and large erosion surfaces in the tidal delta sedimentary system and distributed like a bird-foot shape. By above research, the depositional mode of tidal flat-estuary-delta in Tazhong area has been established and the distribution of favorable reservoirs has been predicted.

四川盆地中二叠统层序地层格架下岩相古地理特征

随着对四川盆地碳酸盐岩储层的重视和大力勘探，中二叠统发育的滩相储层也构成了盆内有利的含气层位之一。本文根据岩心观察、野外剖面实测、镜下岩石薄片鉴定分析和其它测试资料，结合岩石学、古生物、沉积构造等沉积相标志的综合研究，认为研究区中二叠世主要发育浅水型碳酸盐岩台地沉积，细分为碳酸盐岩台地和台地前缘斜坡相及若干亚相和微相。以经典层序地层学理论为指导，通过以岩性–岩相转换界面为主的层序界面识别，确定中二叠统发育5个II型三级层序，每个层序划分出TST和HST两个沉积体系域。在沉积相和层序地层学分析的基础上，以各层序体系域作为编图单元和“单因素分析综合作图法”为技术方法，编制了各体系域的岩相古地理图并对其演化特征进行了分析。结合各相带储集物性特征，认为台缘滩和台内滩为最有利储集相带，尤以SQ2-HST和SQ4-HST沉积期形成的滩相颗粒灰岩经过白云石化作用改造后更具储集意义。 With the recognition and vigorous exploration of carbonate reservoirs in Sichuan Basin, bank facies reservoir developed in middle Permian Maokou and Qixia Formation also constitute beneficial layer of the basin where new gas source can be discovered. According to core observation, field profile measurement, microscopically rock thin section identification, and other testing data, combining the research of sedimentary facies signs such as petrology, paleontology, sedimentary structure, etc., the area develops sedimentary model as shallow-water carbonate platform in middle Permian, further classifies as the sedimentary facies of carbonate platform, platform margin slope and several subfacies and microfacies. We apply Vail’s classical sequence stratigraphy theory as guidance and identify stratigraphic sequence boundaries as lithology-lithofacies convert interface, so determine that Middle Permian develops five Ⅱ-type third degree sequence, and each sequence is divided into two depositional system tracts as TST and HST. Base on sedimentary facies and sequence stratigraphy analysis, we take each sequence systems tract as the mapping unit and the “single-factor analysis and comprehensive mapping method” as the technical methods and compose lithofacies paleogeography map of each sequence system tract and describe its evolution character. Associated with reservoir physical property character of each phase belt, the platform edge shoals and inner platform shoals that are considered the most beneficial reservoir facies, especially shoal facies grain limestone in SQ2 HST and SQ4 HST which was dolomitisated has more reservoir significance.

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.

Analysis of High-Frequency Sequence Stratigraphy Architecture of Putaohua Oil Layer in Sanzhao Sag of Songliao Basin

Using high-resolution sequence stratigraphy theory and its technology, based on 22 well cores and 4 256 logging data, interface types and characteristics of different grades the base-level cycle in Putaohua oil layer of Sanzhao Sag was systematically analyzed, and Putaohua oil layer is divided into 1 medium-term base level cycle, 4 short-term base level cycles, 8 super-short-term base level cycles, established high-resolution sequence strata framework, and proposed sequence stratigraphy model of middle super-short-term base level cycles meridionally grado-thin and up to vanish with syndepositional structure lifting control in the south of Putaohua oil layer. Sandstone is offlap Pinch-out in the upper of Putaohua oil layer, and Sandstone is onflap Pinch-out in the under of Putaohua oil layer from north to south.

Gulong Oilfield Putaohua Oil Layer in the Gu 83 Block Sequence and Sandstone Characteristics Research

Gu 83 wellblock is the center of the Gulong reserves, the well test oil yield is high, the oil-bearing area shall, as reserves and production increase nine oil production company of Daqing oil field replacement area. On the basis of high resolution sequence stratigraphy theory, strata as the instruction, the trunk section and the well combination method is used to contrast layer and multiple well profile compared to small layer, establish high resolution stratigraphic framework. The Putaohua reservoir is divided into three sandstone under the group, which, subdivided three eight small layers for sandstone. Through well combine to determine the sequence division of the interface, divided into Putaohua reservoir. Considering lithology, curve characteristics of shaft vibration, even the well profile correlation research area according to the principle, method, sequence division division, in the Putaohua oil layer, three sets of sandstone under the group; On the segmentation, each group sandstone, upper sandstone will eventually set is divided into two layers of P11, P12; middle sandstone is divided into P13, P14, P15 three small layer; under sandstone under group is divided into P16, P17, P18 three small layer.

Research on Sedimentary Microfacies of Sandstone Group I in Putaohua Oil Reservoir of Gu83 Block in Gulong Oilfield

The oil and gas reserves of Gu83 block in Gulong oilfield is very abundant, but the development is very difficult because the sand bodies are thin, scattered and lack of horizontal continuity. Guided by the theory of sequence stratigraphy and reservoir sedimentology, using drilling core, logging and seismic data, the researcher found that the interest area belongs to delta front subfacies deposition, which can be mainly classified by four miscrofacies types including underwater distributary channel, mouth, sheet sand and bay between distributary. The plane distribution of sedimentary microfacies are mainly controlled by the west and north provenance, the two source collected in the middle east of the work area.

Sedimentary Characteristics in Zhalainuoer Group in Cano Depression Hailaer Basin

Based on the theory of sequence stratigraphy, sequence stratigraphy framework of is established in this paper by comprehensively search of core, logging and 3-D seismic data. Zhalainuoer group in Cano Depression is divided into 5 3rd-order sequences: Sq1、Sq2、Sq3、Sq4、Sq5 from down to up. Based on the division and comparison of sequence formation, the sedimentary facies and the depositional system are proposed to study in the paper, and the main depositional systems are detailed explained. The distribution of these depositional systems is controlled by the sequence framework.

Application of sequence stratigraphy to Triassic terrestrial strata in Tahe area of Tarim Basin

Based on a synthetic geological study of drilling, well logging and seismic data, core observations and geochemical analysis, it is recognized that Triassic sedimentary facies in the Tahe area of Tarim Basin include braided river deposits filling erosional valleys, and sublacustrine fan, canyon and delta facies. Braided river deposits filling erosional valleys are dominated by coarse-grained lithic quartz sandstone with oblique bedding, and represent the most important sedimentation type of sandstone in the study area. Sublacustrine fan and canyon facies are mainly distributed in the Middle Oil Member. Most delta sediments are deposited in highstand system tract (HST). Because of frequent changes in base level, delta sediments are commonly eroded and rarely preserved. Sedimentary cycles are clearly reflected by lithology, sedimentary structures and well logging data, and are closely related to the changes in lacustrine level. In accordance with the basic principle of sequence subdivision, seven type-I boundaries can be recognized in Triassic strata and six type-I sequences are subdivided correspondingly. In general, lowstand system tract (LST) is well developed within stratigraphic sequences and forms the main body of reservoir sandstone in this area; highstand system tract (HST) and transgressive system tract (TST) are often eroded by upper sequences or missed. Although various factors have different influences on terrestrial sequence stratigraphy, the classical sequence stratigraphy theory proposed by VAIL can be applied to terrestrial strata.

Geophysical signature and detection of shallow water flow in the deepwater basin of the northern South China Sea

With the development of deepwater drilling, deepwater geohazards have become a challenge. Shallow water flow (SWF) is one type of the most serious geohazards in deepwater drilling. SWF hazards are only met in deepwater regions and SWF sands have the properties of low density, low velocity and high V(p)/V(s). Based on the theory of Sequence Stratigraphy, the deepwater channel depositional system was identified in Baiyun depression, Pearl River Basin. With the result of AVA inversion, fullwave inversion and poststack inversion, the region with low density, low velocity and high V(P)/V(S)(>9) value were refined in which the SWF may happen.

A Climatic Sequence Stratigraphic Model in the Terrestrial Lacustrine Basin: A Case Study of Green River Formation, Uinta Basin, USA

Abstract:In recent years, with the development of terrestrial sequence stratigraphy, more attention has been focused on the study of the terrestrial lacustrine sequence stratigraphic model globally. Different viewpoints are preferred by researchers. Under the guidance of the theory of sequence stratigraphy, the findings of this paper indicate that climate is a major factor controlling the formation of the fourth‐order sequence, based upon the study of the sequence stratigraphy in the Green River Formation of the Uinta basin in the USA. It also divides the fourth‐order sequence in the terrestrial lacustrine basin into two system tracts: the wet (rising) half‐cycle and the dry (falling) half‐cycle, establishing a new‐style fourth‐order sequence stratigraphic model for the terrestrial lacustrine basin, that is, the climate‐genetic sequence stratigraphic model. As a result, the theory of sequence stratigraphy is greatly enriched.

Millennial-scale sea-level control on avulsion events on the Amazon Fan

The Late Quaternary Amazon deep-sea fan provides a modern analogue to ancient fan systems containing coarse-grained hydrocarbon reservoirs. Sand lenses deposited within the Amazon Fan, due to abrupt shifts in channel pathways called avulsion events, were drilled as part of ODP Leg 155. The hemipelagic sediment directly on top of the avulsion sands was dated using primarily AMS radio carbon dating. This dating shows that these large sand lobes (∼1 km 3) are triggered by relatively small, millennial scale changes in marine transgression and regression (±5–10 m). Relative sea level also controls the architecture of the Channel–levee distributive systems within the Amazon Fan. For example prior to 22 k calendar years BP there is a tripartite channel system. After 22 ka there is only one active Channel–levee system. Transitions between the multi-channel and single channel configurations are related to variations in the volume of sediment supply resulting in aggradation or erosion of channel floor and levee growth in the canyon-channel transition area. The sensitivity of the Amazon deep-sea Fan sedimentation to relatively small changes in sea level supports one of the central assumptions of the theory of Sequence Stratigraphy. In addition this study demonstrates how traps for hydrocarbons may have been formed in ancient fan systems.

Subtle traps prediction using sequence stratigraphy and 3D seismic technology: A case study from Qikou depression in Huanghua basin

Forecasting subtle traps by sequence stratigraphy and 3D seismic data is a sensitive topic in hydrocarbon exploration. Research on subtle traps by geophysical data is the most popular and difficult. Based on the sufficiently drilling data, log data, core data and 3D seismic data, sediment sequence of Qikou depression, Huanghua basin was partitioned by using sequence stratigraphy theory. Each sediment sequence system mode was built. Sediment faces of subtle traps were pointed out. Dominating factors forming subtle traps were analyzed. Sandstone seismic rock physics and its response were studied in Tertiary System. Sandstone geophysical response and elastic modulus vary laws with pressure, temperature, porosity, depth were built. Experimental result and practice shows that it is possible using seismic information forecasting subtle traps. Integrated using geology, log, drilling data, special seismic processing technique, interpretation technique, high precision horizon calibration technique, 3D seismic visualizing interpretation, seismic coherence analysis, attribute analysis, logging-constrained inversion, time frequency analysis, subtle traps object is identified and interpreted. Finally, advantage object of subtle trap in this area was determined. Bottomland sand stratigraphic and lithologic reservoirs in Qinan slope zone have been founded by means of high resolution 3D seismic data field technique, high resolution 3D seismic data processing technique and seismic wave impedence inversion technique.

Sequence Stratigraphic Features of Weathered Carbonate Residuum Reservoirs

Studies on the sequence stratigraphic features of carbonate weathered residuum reveal that the key factor which makes the karstification possible is the permeability paths that occurred, controlled by the exposure events which resulted from drops in the sea level. The formation of carbonate weathered residuum was diagenetically associated with different interfaces of syndepositional sequences. Studies on the weathering degree (diagenetic maturation) of the parasequences in the sedimentary systems have come to the conclusion that the development maturation of the weathered residuum basically represents the increase or decrease of accommodation space. Ideally, a relevant model between sequence stratigraphy and weathered residuum is established. Introducing the theory of sequence stratigraphy into the study of the carbonate reservoirs within the weathered residuum led to the belief that sequence stratigraphic feature analysis of the carbonate weathered residuum is actually a relationship between the different interface natures and reservoir physical properties. By comparing relevant information all over the world, the authors hold that parasequences of neritic carbonates usually represent a small part of sedimentation, and the exposure period makes up about half the period of cycling. Weathered residuum reservoirs occurred dominantly within two temporal ranges: 30–120 Ma, corresponding to megasequences or mesosequences; and 0.01–0.5 Ma, corresponding to parasequences.