Reservoir Architecture Research Articles

Study on the Reservoir Architecture and Remaining Oil Distribution of Braided Channel

Study on the Reservoir Architecture and Remaining Oil Distribution of Braided Channel

Effect of foam and WAG (water alternating gas) injection on performance of thin oil rim reservoirs

A design of experiment was used to create oil rim models from a wider range of reservoir, operational and reservoir architecture parameters. A response surface model was generated based on a concurrent oil and gas production and a Pareto analysis was conducted to ascertain the significance of the parameters. The models were classified based on the Pareto analysis and due to the low oil recoveries arising from the complexity of oil rims, a series of secondary injection schemes were instigated. The results from the models indicated an optimum 2 cycle WAG up dip injection and WAG down dip injection for thin oil rims. Also the results estimated an incremental oil recovery of 9.2% and 30.1% with respect to base case (no injection) for WAG up dip injection and 10.66% and 6.11% for WAG down dip injection while an incremental recovery of 14.2% and 52.74% for up dip foam injection and 18.19% and 29.73% incremental oil recovery for foam down dip injection for oil rim model ‘3’ with large gas cap and large aquifer and model ‘7’ with small gas cap small aquifer respectively. A case study reservoir from the Niger delta region of Nigeria showed an 8.57% and 8.56% incremental oil recovery for foam up dip and foam down dip injection and incremental oil recovery of 8.35% and 7.94% for WAG up dip and WAG down dip injection. This paper will provide useful information as to the extent of oil recovery in different oil rim models under different foam and WAG injection.

The influence of stratigraphic architecture on seismic response: Reflectivity modeling of outcropping deepwater channel units

The size, shape, stacking patterns, and internal architecture of deepwater deposits control reservoir fluid flow connectivity. Predicting deepwater stratigraphic architecture as a function of position along a deepwater slope from seismic-reflection data is critical for successful hydrocarbon exploration and development projects. Stratigraphic architecture from confined and weakly confined segments of a deepwater sediment-routing system is analyzed in outcrop from the Tres Pasos Formation (Upper Cretaceous), southern Chile. Outcrop observations are the basis of two geocellular models: confined channel deposits at Laguna Figueroa and weakly confined channel and scour deposits at Arroyo Picana. Key stratigraphic surfaces and facies relationships observed in outcrop are forward seismic modeled at high to low resolution to bridge the gap in subseismic scale interpretation of deepwater reservoirs and demonstrate challenges associated with identification of varied reservoir architecture. The outcrop-constrained geometry of architectural elements, their stacking arrangement, and the varied internal distribution of facies each impart a strong influence on seismic reflectivity. Key outcomes from the analysis include (1) stratigraphic architecture transitions down-paleoslope from vertically aligned low-aspect-ratio channel elements to a more weakly confined depocenter characterized by a breadth of laterally offset low- and high-aspect-ratio channel and scour elements. Seismic reflections, down to 30 Hz frequencies, record aspects of these stratigraphic changes. (2) Key seismic reflections are often comprised of multiple outcrop-constrained stratigraphic surfaces. Tuning effects result in composite seismic surfaces that are vertically offset from the known position of sedimentary units; this hinders accurate interpretation of stratigraphic surfaces from seismic-reflection data. This is particularly problematic in the weakly confined system in which shifted stratigraphic surfaces, which bound deposits characterized by numerous similar architectural elements, can alter the interpretability of sandstone connectivity within and across zones. Furthermore, misinterpretation of surfaces is problematic when they are flow barriers draped with debris flows, slumps/slides, or thin-bedded turbidites. (3) Tuning effects also impart significant control on volume-based interpretations from seismic data. In particular, calculations of gross rock volume from seismic reflection data that do not consider the tuning or architectural element stacking pattern can overestimate actual volumes by 10%–50%, with implications for reservoir prediction and hydrocarbon volume estimation.

Channel Sandstone Architecture Characterization by Seismic Simulation

To describe the distribution of sandstone reservoirs between wells finely, this paper takes the sandstone reservoir of Layer Nm Ⅱ -4 in Qinhuangdao 32-6 Oilfield for example, and uses the seismic forward simulation and well loggings to study the channel sandstone reservoir. Under the guidance of the modern rivers and outcrops sandstone distribution pattern, the predicting limitations of the seismic forward simulation about channel sandstone boundaries such as mudstone interlayer between channel sandstone and elevation distance between adjacent channel sandstone are clear. The research shows that the mudstone interlayer can be described by seismic forward simulation seismic when the mudstone interlayer is thicker than 2 m and the channel sandstone is thicker than 10 m because of the appearance of the seismic peak when the main frequency of seismic data is nearly 60 Hz. And the elevation distance between adjacent channel sandstone can be described by the seismic forward simulation when elevation distance is longer than 6 m and the channel sandstone is thicker than 10 m because of the appearance of the seismic peak. And the seismic waveform features of single channel sandstone boundaries such as elevation distance between channels, overbank sandstone and abandoned channels. Under the study mentioned above, the single channel boundaries are described in Layer Nm Ⅱ -4 of Qinhuangdao 32-6 Oilfield, and the predicting boundaries are confirmed by the chemical tracers. The results show that the channel sandstone reservoir architecture characterization can be improved by the seismic forward simulation.

Reservoir architecture and fracture characterization of low-permeability sandstone reservoir: a case study of Biandong oilfield, Jinhu depression, northern Jiangsu Basin, China

Fracture is one of the most important factors through the whole process of low-permeability reservoir development. Biandong oilfield is a typical low-permeability fractured sandstone reservoir, and has stepped into high water cut stage; thus, the waterflooding effect is poor. Therefore, many contradictions such as high moisture content, decreasing production speed, and low recovery efficiency are becoming increasingly prominent, which have seriously hindered the sustainable development, and need to be solved urgently. However, few such studies on reservoir characterization in low-permeability fractured sandstone reservoir have been conducted in China. In this study, through comprehensive analysis on reservoir characterization and sedimentary environment, significant results are achieved. Three types of fracture occurrence are identified; they are high-angle fracture, low-angle fracture, and horizontal fracture, respectively. Two types of reservoir pore (primary porosity and secondary porosity) are recognized based on thin-section observation and analysis. The diagenetic stage of Biandong oilfield are divided into three stages, early A, early B, and late A, respectively. Finally, a regional discrete fracture network model is established with Fisher’s algorithm based on three-dimensional geological model. All the research results presented above can make a significant instructing function for making reservoir development plan and improving recovery efficiency.

Solving a tuff problem: Defining a chronostratigraphic framework for Middle to Upper Jurassic nonmarine strata in eastern Australia using uranium–lead chemical abrasion–thermal ionization mass spectrometry zircon dates

To better predict the architecture of reservoirs and the location of undiscovered resources in fluvial-dominated strata, a sound chronostratigraphic framework is needed. This study reassesses the stratigraphic framework of petroleum-bearing Jurassic fluviolacustrine successions in the Eromanga, Surat, and Clarence–Moreton Basins of eastern Australia. Correlation of the strata is challenging because of the heterolithic facies, the absence of conventional stratigraphic marker beds, and the longevity of palynostratigraphic zones. The abundance of laterally discontinuous volcanic air–fall tuffs and volcanogenic sandstones across the Jurassic of eastern Australia allows for the construction of a new, regional chronostratigraphic framework. High-precision U-Pb zircon chemical abrasion–thermal ionization mass spectrometry (CA-TIMS) dates ranging from 168.07 ± 0.07 Ma to 149.08 ± 0.06 Ma were obtained from 31 samples from 13 wells across 3 basins. Five chronostratigraphic datums were defined and extrapolated to 677 wells within a time interval of 420 ka or less over hundreds of kilometers across eastern Australia. The new chronostratigraphic framework reveals inaccuracies in picking lithostratigraphic units based on lithology and wire-line log characteristics and shows coal-bearing facies of the Walloon Coal Measures to be two episodes of coal (peat) accumulation separated by an unconformity. The study also demonstrates the feasibility of extending chronostratigraphic datums to neighboring basins without tuff beds by dating the youngest zircon in volcanogenic sandstones by U-Pb CA-TIMS following laser ablation–inductively coupled plasma mass spectrometry analysis. The dates provide a substantial revision to the Middle to Upper Jurassic stratigraphy of eastern Australia. The use of precise U-Pb CA-TIMS dates should help elucidate the lithofacies architecture of nonmarine successions in other basins and assist in petroleum development.

High resolution facies architecture and digital outcrop modeling of the Sandakan formation sandstone reservoir, Borneo: Implications for reservoir characterization and flow simulation

Advances in photogrammetry have eased the acquisition of high-resolution digital information from outcrops, enabling faster, non-destructive data capturing and improved reservoir modeling. Geocellular models for flow dynamics with in the virtual outcrop in siliciclastic deposits at different sets of sandstone facies architecture remain, however, a challenge. Digital maps of bedding, lithological contrast, spatial-temporal variations of bedding and permeability characteristics make it more easy to understand flow tortuosity in a particular architecture. An ability to precisely model these properties can improve reservoir characterization and flow modeling at different scales. Here we demonstrate the construction of realistic 2D sandstone facies based models for a pragmatic simulation of flow dynamics using a combination of digital point clouds dataset acquired from LiDAR and field investigation of the Sandakan Formation, Sabah, Borneo. Additionally, we present methods for enhancing the accuracy of outcrop digital datasets for producing high resolution flow simulation. A well-exposed outcrop from the Sandakan Formation, Sabah, northwest Borneo having a lateral extent of 750 m was chosen in order to implement our research approach. Sandstone facies and its connectivity are well constrained by outcrop observations, data from air-permeability measurements, bilinear interpolation of permeability, grid construction and water vector analysis for flow dynamics. These proportions were then enumerated in terms of static digital outcrop model (DOM) and facies model based on sandstone facies bedding characteristics. Flow simulation of water vector analysis through each of the four sandstone facies types show persistent spatial correlation of permeability that align with either cross-bedded orientation or straight with more dispersion high quality sandstone (porosity 21.25%–41.2% and permeability 1265.20–5986.25 mD) and moderate quality sandstone (porosity 10.44%–28.75% and permeability 21.44–1023.33 mD). Whereas, in more heterolithic sandstone (wavy- to flaser-bedded and bioturbated sandstone), lateral variations in permeability show spatially non-correlated patterns over centimeters to tens of meters with mostly of low quality sandstone (porosity 3.4%–12.31% and permeability < 1 mD to 3.21 mD). These variations reflect the lateral juxtaposition in flow dynamics. It has also been resulted that the vertical connectivity and heterogeneities in terms of flow are mostly pragmatic due to the interconnected sandstone rather than the quality of sandstone.

Architecture and reservoir quality of low-permeable Eocene lacustrine turbidite sandstone from the Dongying Depression, East China

Abstract The architecture and quality of lacustrine turbidites that act as petroleum reservoirs are less well documented. Reservoir architecture and multiscale heterogeneity in turbidites represent serious challenges to production performance. Additionally, establishing a hierarchy profile to delineate heterogeneity is a challenging task in lacustrine turbidite deposits. Here, we report on the turbidites in the middle third member of the Eocene Shahejie Formation (Es3), which was deposited during extensive Middle to Late Eocene rifting in the Dongying Depression. Seismic records, wireline log responses, and core observations were integrated to describe the reservoir heterogeneity by delineating the architectural elements, sequence stratigraphic framework and lithofacies assemblage. A petrographic approach was adopted to constrain microscopic heterogeneity using an optical microscope, routine core analyses and X-ray diffraction (XRD) analyses. The Es3m member is interpreted as a sequence set composed of four composite sequences: CS1, CS2, CS3 and CS4. A total of forty-five sequences were identified within these four composite sequences. Sand bodies were mainly deposited as channels, levees, overbank splays, lobes and lobe fringes. The combination of fining-upward and coarsening-upward lithofacies patterns in the architectural elements produces highly complex composite flow units. Microscopic heterogeneity is produced by diagenetic alteration processes (i.e., feldspar dissolution, authigenic clay formation and quartz cementation). The widespread kaolinization of feldspar and mobilization of materials enhanced the quality of the reservoir by producing secondary enlarged pores. In contrast, the formation of pore-filling authigenic illite and illite/smectite clays reduced its permeability. Recovery rates are higher in the axial areas and smaller in the marginal areas of architectural elements. This study represents a significant insight into the reservoir architecture and heterogeneity of lacustrine turbidites, and the understanding of compartmentalization and distribution of high-quality sand reservoirs can be applied to improve primary and secondary production in these fields.

Deepwater slope valley reservoir architecture and connectivity, Brazil

A detailed interpretation was undertaken to improve the description of connectivity and reservoir distribution for a field in the Campos Basin, Brazil. The Miocene reservoir was deposited in a deepwater, channelized turbidite fairway in a slope valley setting. Static pressure data acquired after production start-up indicated communication across the reservoir, but the values varied significantly, implying that the efficiency of communication varies. High-quality 3D seismic in combination with production and well data led to a hierarchical interpretation, from channel element to complex-set scale, which defined key stratigraphic and pressure surfaces. Integration of a high-repeatability 4D monitor survey showed that the 4D response changed at stratigraphic boundaries. The 4D data tied to production indicate that an aquifer is traveling along the base of the reservoir in discrete channels. The use of 4D depth shift data increased confidence in the waterfront interpretation in areas without production data. Aggradational channel complexes in the upper part of the reservoir show baffling at the margins of channel complexes down to the channel element scale. The channel elements are also likely baffled on the margins with greater connectivity downward into the lower, amalgamated unit. The lower unit shows greater lateral continuity in 4D signal, consistent with pressure data that indicate larger depletion over greater distances than the overlying aggradational complexes where producer wells are located. In summary, mapping of reservoir architecture and identification of key stratigraphic surfaces from 3D have reduced uncertainty in reservoir distribution and connectivity. Integration of 4D seismic and production data has provided confirmation of connectivity through the identification of waterfronts and unswept areas of the reservoir.

Process-based modelling of morphodynamics and bar architecture in confined basins with fluvial and tidal currents

Tides affect sediment transport dynamics in many coastal environments. Tidal effects may be particularly large in marine-influenced confined settings due to tidal amplification. Yet, it is largely unknown in what ways the width of confined basins and the strength of tidal currents impact sand deposition, and how this would affect reservoir architecture. This study applies the morphodynamic model Delft3D to systematically test models of bar stratigraphy and preservation in confined basins with mixed fluvial and tidal currents. A unique aspect of the methodology is that morphological as well as subsurface data are considered, thus enabling the tidally-influenced bar morphodynamics to be related explicitly to the associated bar deposits. By systematically varying tidal range in idealized confined basins of varying width, it is shown that bar dimensions are primarily affected by basin width, and that tidal range has a secondary effect. An increase in basin width results in a higher bar braiding index, a larger number of bars as well as longer bars, wider bars and thicker bar deposits. Synthetic architectures that can be compared directly with the sedimentary record show a high degree of stratigraphic complexity within tidally-influenced bars. Statistical distributions, summarizing the internal structure of tidally-influenced bars, provide quantification of the preservation of bars and such approaches will improve their three-dimensional characterization in geo-models of tidally-influenced and confined settings.

Reservoir architecture model of the Nieuwerkerk Formation (Early Cretaceous, West Netherlands Basin): diachronous development of sand-prone fluvial deposits

Abstract The sand-prone fluvial Delft Sandstone Member of the Nieuwerkerk Formation is the main target for geothermal exploitation in the West Netherlands Basin. Uncertainty reduction in the modelling of permeability heterogeneity and connectivity of the sandstone reservoir units is of prime importance in the low-profit geothermal energy market. Lithostratigraphic correlation of the Delft Sandstone Member dates back to the 1970s, and considers the fluvial deposits as Valanginian (140–134 Ma) in age and synchronously deposited throughout the basin. Analysis of newly-acquired palynological data, in combination with well-log correlation and seismic interpretation, enabled the construction of a sequence-stratigraphic framework for the Nieuwerkerk Formation, in which the fluvial sandstones were deposited in a much wider age range than previously believed, from Late Ryazanian to Valanginian (142–134 Ma). The depocentre of fluvial deposition shifted in time from NE to SW across the width of the basin. This diachronous development resulted in a discontinuous spatial arrangement of fluvial sandstones. The new reservoir architecture model will aid in the well placement of geothermal doublets and the assessment of interference risk of adjacent geothermal projects.

Reservoir Fluid Geodynamics: The Chemistry and Physics of Oilfield Reservoir Fluids after Trap Filling

Oilfield reservoirs exhibit a wide array of complexities that have great impact on the efficiency of oil production. Major challenges include delineating overall reservoir architecture and the distributions of the contained fluids. Reservoir crude oils consist of dissolved gases, liquids, and dissolved solids (the asphaltenes); the corresponding compositional variations and phase transitions within reservoirs greatly impact production strategies and economic value. Standard workflows for understanding reservoir (rock) architecture are subsumed in the discipline “geodynamics”, which incorporates the initial rock depositional setting and subsequent alterations through geologic time to yield the present-day reservoir. However, reservoir fluids are not generally treated in such a systematic manner. Petroleum system modeling provides the timing, type, and volume of hydrocarbon fluids that charge into reservoirs. However, there is little treatment regarding how these fluids change after filling the reservoir. A...

Lombardi reservoir, San Ardo field, California: Sequence stratigraphy in a deltaic environment associated with local tectoni

The Lombardi reservoir at San Ardo oil field in California is extremely sand rich (>90%) and appears to be a relatively simple reservoir several hundred feet thick. The purpose of this study is to characterize stratigraphic complexities in the Lombardi reservoir that may affect later production and interpret how changes in stratigraphic architecture are tied to local syndepositional tectonism. Two parasequence sets are present in the Lombardi: the reservoir exhibits clinoform geometries along the western edge of the field and stacking patterns within the reservoir change across the field. Based on stacking pattern, core, and correlation studies, two possible sequence boundaries are recognized in the Lombardi sand. A lower sequence boundary is proposed approximately in the middle of the Lombardi sand, and an upper sequence boundary is proposed at the top of the Lombardi sand. In the southern part of the field, the Lombardi sand consists of two progradational parasequence sets, separated by the mid-Lombardi sequence boundary. The upper sequence boundary clearly truncates underlying folded Lombardi sand. Just a few miles (∼5 km) away, in the northwest part of the field, the Lombardi sand consists of a lower progradational parasequence set and an upper retrogradational parasequence set, separated by the mid-Lombardi sequence boundary. The upper sequence boundary at the top of the Lombardi sand shows little evidence of truncation of underlying units and is recognized by onlapping of younger strata. The difference in reservoir architecture between the south and northwest part of the field, a distance of only a few miles (∼5 km), is interpreted to be related to syndepositional uplift accompanying tectonism in the south. In core, the Lombardi sand consists mostly of homogeneous sand and bioturbated sand, arranged in upward-coarsening successions. The Lombardi sand is interpreted to be the product of deltaic deposition based on (1) the presence of homogeneous and laminated sandstones interpreted to represent mass flow deposits and (2) its restricted geographic distribution within the Salinas basin. No evidence of deposition in a wave-dominated or tidal-dominated shoreline is indicated. The interpretation presented here is that the sediments were deposited on the front of a delta emptying into a wave-protected estuary or bay, with minimal tidal effects. Complexities in stratigraphic architecture along the western edge of the field do not currently affect production but will likely become important during later stages of field development. That is, in the developed part of the field, reservoir continuity is not an issue, because of high sand content and sheet-like geometries. However, at the margins of the field, which will be produced in the future, clinoform geometries and sandstone tongues clearly affect reservoir continuity and will create vertical compartments during draining.

Research on meandering river reservoir deposition architecture and 3D modeling of the Gudao Oil field in the Bohai Bay Basin

The distribution of remaining oil is controlled by internal sand body heterogeneity in the middle and late stages of oil field development. Reservoir architecture analysis has been conducted in the third sand group in the Guantao Formation of the Gudao Oil field. Different scales of reservoir architecture units have been identified, including complex meandering river belt, single meandering river belt, single point bar and inner point bar. Four different single channel signatures have been found in the research area to identify the single channel belt. The single point bar has been distinguished based on point bar development characteristics. The architecture of the inner point bar has been analyzed based on subsurface well data and empirical formulas. The lateral accretion angle of the muddy layer ranges from 5° to 8°, the interspace between lateral accretion muddy layers ranges from 20 to 35 m, and the horizontal width of a single lateral accretion sand body is 55–120 m. Based on the above-mentioned reservoir architecture analysis, a reservoir architecture model has been established using the hierarchical modeling method. A three-dimensional porosity and permeability model has been developed within architecture model constraints and could provide a reliable geological template for oil field development and production.

Quantitative characterization of shales within tidally influenced fluvial valley fill deposits of the Ferron Sandstone, eastern Utah: Implications for hydrocarbon exploration

This study evaluates the proportion, length, and effective properties of thin (0.003 - 0.7 m [0.01 – 2.3 ft.]) shale beds and drapes in tidally-influenced channels within a compound valley fill with a focus on estimating geologically-based effective rock properties. The Cretaceous Ferron Sandstone is an outcrop analog for fluvial-tidal systems with primary reservoirs being deposited as tidally-influenced valley filling point bars. The study outcrops expose three valley systems in Neilson Wash of Utah. Light detection and ranging derived digital outcrop models have been used to characterize shale length, width, thickness and frequency of each valley fill succession. Long, uncommon, and anisotropic shales in Valley-1 (V1) were deposited in a braided setting with little tidal influence. In contrast, shales in Valley-2 (V2) were abundant, short, common, and equidimensional suggesting deposition by more tidally-influenced meandering rivers. Short, frequent, and equidimensional shales in Valley-3 (V3) were deposited in single-thread meandering rivers with less tidal influence. A sandstone-shale model was utilized to estimate the effects of shales on vertical to horizontal permeability ratio (kv/kh). The unique character of each depositional unit was reflected in resultant kv/kh distributions. The valley fill deposits, V1, V2, and V3 had an average kv/kh ratio of 0.11, 0.09 and 0.17, respectively. More tidally-influenced reservoirs such as the studied V2 had short, but frequent shales which resulted in low kv/kh estimates. Estimates of kv/kh for valleys that predominantly contained fluvial point bar deposits with lesser tidal influence (V1 and V3) were higher. The results of this study highlight the link between shale heterogeneity, reservoir architecture, and inferred flow parameters.

Analysis of Reservoir Architecture of Shallow-water Delta Front Based on Process—A Case of S2L410 in Southern 79 Block in Wennan Oilfield

The sand body distribution is relatively limited in this block, the lens-shaped sandbodies are more developed, the change of intergranular sandbody is fast and the internal architecture of the sand body is complex, which results in the difficulties of the arrangement of horizontal wells in the study area and the tapping of remaining oil in high water reservoirs. In this paper, taking an example of S2L410 sandbodies in Wen 79 Southern Block, rich drilling data, core data, logging data and geological research results accumulated over many years in Wennan Oilfield were applied to discuss the anatomical method of the reservoir architecture unit in the underwater distributary channel in the shallow delta front, the hierarchy of the internal architecture of the reservoir and the anatomy of the single sand body. On the basis of this, the sequence of the underwater distributary channel in the composite channel is determined by the cross section and the source profile. Under the guidance of the sedimentology principle, the formation process of the underwater distributary channel is restored and the evolution process of underwater distributary channel is recovered.

Architecture mode, sedimentary evolution and controlling factors of deepwater turbidity channels: A case study of the M Oilfield in West Africa

Turbidity channels have been considered as one of the important types of deepwater reservoir, and the study of their architecture plays a key role in efficient development of an oil field. To better understand the reservoir architecture of the lower Congo Basin M oilfield, semi-quantitative–quantitative study on turbidity channel depositional architecture patterns in the middle to lower slopes was conducted with the aid of abundant high quality materials (core, outcrop, logging and seismic data), employing seismic stratigraphy, seismic sedimentology and sedimentary petrography methods. Then, its sedimentary evolution was analyzed accordingly. The results indicated that in the study area, grade 3 to grade 5 architecture units were single channel, complex channel and channel systems, respectively. Single channel sinuosity is negatively correlated with the slope, as internal grains became finer and thickness became thinner from bottom to top, axis to edge. The migration type of a single channel within one complex channel can be lateral migration and along paleocurrent migration horizontally, and lateral, indented and swing stacking in section view. Based on external morphological characteristics and boundaries, channel systems are comprised of a weakly confining type and a non-confining type. The O73 channel system can be divided into four complex channels named S1–S4, from bottom to top, with gradually less incision and more accretion. The study in this article will promote deeper understanding of turbidity channel theory, guide 3D geological modeling in reservoir development and contribute to efficient development of such reservoirs.

A Study of Architecture of Thin Interlayer within Meandering River Monosandbody of Thick-Bedded Oil Layers

This paper investigates the reservoir architecture of thin interlayer within meandering river monosandbody in the thick-bedded oil layers. The thin interlayer within the monosandbody of the terrestrial reservoir is one of the dominant factors which form the reservoir heterogeneity of fluid motion. It is of equal importance in comparison with the rhythmic distribution of permeability, and it is also the important content of the elaborate representation of reservoirs. However, previous researches of the heterogeneity of reservoir focus mostly on the theory of distribution disparity of the permeability and neglect the influence of thin interlayer on the heterogeneity. Therefore, taking the PⅠ2 individual reservoir at the Putaohua reservoir formation in Daqing oilfield as an example, this paper analyzes the distribution, formation, and the three-dimensional construction of the internal thin interlayer of the monosandbody from a new point of view, on the basis of which a set of cycle research technique about it is put forward. With the method of configuration parameter extraction, which is most important before establishing interlayer configuration in three dimensions, this study clarifies the classification, causes of formation and the differences of distinct monosandbodies. Ultimately, four categories of thin interlayer according to the characteristics of the studied area is divided and two dominate causes for thin interlayer formation is discussed: argillaceous and arenaceous rock interlayer through deposition and interlayer in process of sedimentary diagenesis.For the convenience of the study, here mainly focuses on the thick - thin interlayer. Techniques are taken the use of determining the obliquity of the thin interlayer superface based on the configuration of paired wells and abandoned channel surface. The causes for thin interlayer and their classification, distribution and the three-dimensional construction are entirely revealed, which would possess important geologic meaning for taking affective engineering measures in the aspects of the elaborate representation of oil reservoir, and the research of remaining oil formation and distribution.

Reservoir Computing in Embedded Systems: Three variants of the reservoir algorithm

The rich computational dynamics coupled with simple training in reservoir computing (RC) algorithms makes them a natural choice for spatiotemporal learning systems in embedded platforms. In this article, we study three variants of the reservoir algorithm: the echo-state network (ESN), the liquid-state machine (LSM), and the time-delay reservoirs (TDRs). A digital reservoir architecture is used as a baseline test bed to benchmark for epileptic seizure detection. An average accuracy of 85% is observed across the three variants of the algorithm and the effectiveness of the reservoir is assessed with different metrics.

Distribution of remaining oil based on fine 3-D geological modelling and numerical reservoir simulation: a case of the northern block in Xingshugang Oilfield, China

As the Xingshugang Oilfield is in the late stage of development, a conventional geological model could not meet the needs of further enhancing oil recovery, and the establishment of a fine 3-D geological model, namely the 3-D reservoir architecture model, is urgently required. The 3-D reservoir architecture model has a strong advantage in the detailed characterization of the distribution of various architectural elements and flow baffles and barriers in 3-D space. Based on the abundant data from close well spacing, in combination with the understanding of sedimentary facies and reservoir architecture, this study builds the 3-D reservoir architecture model to show the spatial distribution of different architectural elements and intercalations (mud drapes) under the control of third-, fourth- and fifth-order bounding surfaces. The study then establishes the property model under the control of sedimentary facies (architectural elements). Subsequently, based on the fine 3-D geological model, the distribution of remaining oil is obtained after the numerical reservoir simulation. The remaining oil primarily lies in the port of channel bifurcation, the parts blocked by intercalations and abandoned channels, and the edges of different facies. This observation provides a theoretical basis for further development and adjustment.