Stratigraphic Modified Lorenz Plot Research Articles

Flow unit classification and characterization with emphasis on the clustering methods: a case study in a highly heterogeneous carbonate reservoir, eastern margin of Dezful Embayment, SW Iran

Previous attempts to classify flow units in Iranian carbonate reservoirs, based on porosity and permeability, have faced challenges in correlating the rock's pore size distribution with the capillary pressure profile. The innovation of this study highlights the role of clustering techniques, such as Discrete Rock Type, Probability, Global Hydraulic Element, and Winland's Standard Chart in enhancing the reservoir's rock categorization. These techniques are integrated with established flow unit classification methods. They include Lucia, FZI, FZI*, Winland R35, and the improved stratigraphic modified Lorenz plot. The research accurately links diverse pore geometries to characteristic capillary pressure profiles, addressing heterogeneity in intricate reservoirs. The findings indicate that clustering methods can identify specific flow units, but do not significantly improve their classification. The effectiveness of these techniques varies depending on the flow unit classification method employed. For instance, probability-based methods yield surpassing results for low-porosity rocks when utilizing the FZI* approach. The discrete technique generates the highest number of flow unit classes but provides the worst result. Not all clustering techniques reveal discernible advantages when integrated with the FZI method. In the second part, the study creatively suggests that rock classification can be achieved by concurrently clustering irreducible water saturation (SWIR) and porosity in unsuccessful flow unit delineation cases. The SWIR log was estimated by establishing a smart correlation between porosity and SWIR in the pay zone, where water saturation and SWIR match. Then, the estimated saturation was dispersed throughout the reservoir. Subsequently, the neural network technique was employed to cluster and propagate the three finalized flow units. This methodology is an effective recommendation when conventional flow unit methods fail. The study also investigates influential factors causing the failure of flow unit classification methods, including pore geometry, oil wettability, and saturation in heterogeneous reservoirs.

Geophysical investigation of aquifer flow unit characteristics in northern parts of Akwa Ibom State, Southern Nigeria

The heterogeneous nature of the aquifer system poses significant challenges to both aquifer delineation into hydraulic flow units (HFUs) and the assessment of groundwater flow efficiency. This heterogeneity leads to changes in aquifers’ hydraulic parameters, which include porosity, flow and storage capacities, permeability, flow Zone Indicator (FZI) and aquifer quality index (AQI). Thus, the key aim of this study is to examine aquifer flow unit characteristics in Ikot Ekpene and Obot Akara municipalities by categorizing the units into distinctive HFUs via the combined application of the electrical resistivity technology (ERT), Stratigraphic Modified Lorenz Plot (SMLP) and Flow Zone Indicator (FZI) techniques. The area is shown to comprise successions of three to four sandy layers with minor clay interbeddings at few locations from the ERT results. The aquifer units are found in layers two and three respectively at depths of between 1.6 and 30.2 m with 30.2–89.0 m thickness. The results of the FZI technique identify two distinct HFUs in the area with respective discrete rock typing (DRT) values of 14 and 15 whereas that of the SMLP method reveal 5 unique HFUs, each characterised by similar flow characteristics. The delineated flow units from the SMLP results are classified as conductors with a fair efficiency ranking. This ranking seems to correlate with the DRT results for the delineated unconsolidated sandy and gravelly sand aquifers, which are shown to be perfectly heterogeneous. These findings from this maiden study in the area are very promising and provide useful insights on groundwater flow characteristics in the area to assist groundwater resource regulating authorities and policy makers in making decisions on appropriate location of new water boreholes to satisfy the mushrooming water needs of the local population.

Pore-Type Characterization and Reservoir Zonation of the Sarvak Formation in the Abadan Plain, Zagros Basin, Iran

Carbonate reservoirs are characterized by their complex depositional–diagenetic history and, consequently, intricate pore networks. In this study, pore types and reservoir zones of the Sarvak Formation, which is the second most important oil reservoir in Iran, are investigated by integrating core, thin-section, porosity–permeability, scanning electron microscopy (SEM), and mercury injection capillary pressure (MICP) data. Depositional, diagenetic, and fracture pores are identified in macroscopic to microscopic scales. Frequency analysis of pore types revealed that diagenetic pores, including vuggy, moldic, intercrystalline, and fracture pores, formed the majority of pore spaces of the Sarvak Formation. They are dominantly recorded in the regressive systems tracts of both the Cenomanian and Turonian sequences, just below the paleoexposure surfaces. Away from the disconformities, there are two general trends regarding the pore-types distribution: (a) grain-supported facies of shoal and talus settings with dominant primary (depositional) pores including interparticle, intra-skeletal, and growth-framework pores, which are concentrated in the middle part of the formation, and (b) microporous mud-dominated facies with various types of primary and secondary pore types in the TSTs of third-order sequences, especially in the lower part of the Sarvak Formation. Stratigraphic modified Lorenz plot differentiated reservoir, speed, barrier, and baffle zones in this formation. Depositional–diagenetic characters, petrophysical properties, and dominant pore types are defined for each zone in a sequence stratigraphic framework.

Application of improved stratigraphic modified Lorenz plot and flow zone indicator in discriminating the Igbo-Etiti aquifer into hydraulic flow units, eastern Nigeria

Discriminating the Igbo-Etiti aquifer sequence into hydraulic flow units was carried out employing integrated method. The method demonstrated an excellent potentiality in delineating and classifying the aquifer into hydraulic flow units (HFU). Results of electrical resistivity survey identified five geoelectric layers in the study area. The fourth layer with the aid of the layer's geologic unit characteristics and borehole lithology was delineated as the aquifer layer. Results from improved stratigraphic modified Lorenz plot (ISMLP) identified the slope, angle and percentage contributions of the established HFUs to range from 0.0029 to 3.1455, 0.1660° to 72.364° and 1.3–76.2% respectively. ISMLP result analysis delineated a total of five (5) classes of hydraulic flow units. These classes of HFUs based on efficiency ranking and classification, range from barrier unit with tight flow capacity efficiency to super conductive unit with good flow capacity efficiency. Results of ISMLP delineated group 4 HFU (G4 HFU) with a total flow capacity percentage contribution of 5.6% as a super conductor unit and the best flow capacity efficiency unit in the study area. G2 HFU described to be a conductor unit was identified as the dominant class of HFU in the study area with a total flow capacity contribution of 76.2% to the overall aquifer flow capacity. Results from flow zone indicator (FZI) method revealed a total of five (5) hydraulic flow units with FZI unique values of 16, 17, 18, 19 and 20. FZI results, identified HFU3 and HFU4 as the most occurring HFU in the aquifer layers, with HFU1 and HFU2 outlined as the least occurring HFU. The integrated approach successfully and uniformly identified five (5) classes of HFUs in the study area. Dykstra-Parson's coefficient of 0.618 revealed very high heterogeneous aquifer layers.

Scale, origin, and predictability of reservoir heterogeneities in shallow-marine carbonate sequences: A case from Cretaceous of Zagros, Iran

This study presents an integrated reservoir heterogeneity analysis of an Iranian carbonate oil reservoir (Sarvak Formation) in the Zagros region. Both static and dynamic aspects of reservoir heterogeneities are considered by integration of routine–special core data and geological attributes (i.e., depositional facies and textures, diagenetic alterations, pore types, and sequence stratigraphic positions). Core porosity and permeability, mercury injection capillary pressure, and scanning electron microscopy data are used along with the results of petrographic studies to define petrographic rock types, pore types, hydraulic flow units, and reservoir to non-reservoir (baffle or barrier) zones in the studied reservoir. Spatial facies distribution (facies variability) and development of disconformable surfaces (sequence boundaries) controlled the large-scale reservoir heterogeneities. On the other hand, variations in microscopic characteristics of depositional facies (i.e., textures and structures) and diagenetic features (e.g., intensity of dissolution, cementation and compaction) formed the small-scale reservoir heterogeneities. The best productive zones of this reservoir are meteorically-dissolved reef-talus and shoal facies, accumulated within the regressive systems tracts of third-order sequences. Intensively compacted and cemented facies formed the effective vertical barrier/baffle zones in this reservoir, especially within the transgressive systems tracts and around the maximum flooding surfaces. Results of this study revealed that the stratigraphic modified Lorenz plot (SMLP) is a useful tool for the discrimination of large-scale reservoir heterogeneities, while hydraulic flow units and Winland rock typing approaches are applicable for the identification of small-scale heterogeneities. This study indicated that the large-scale heterogeneities of carbonate reservoirs are predictable in a sequence stratigraphic framework, especially in the third-order scale. Such a heterogeneity model calibrated in the sequence stratigraphic framework provides a reliable basis for reservoir modeling of heterogeneous carbonate reservoirs in the field-to regional scales.

Aquifer flow unit analysis using stratigraphic modified Lorenz plot: a case study of Edem, eastern Nigeria

The present study aimed at evaluating aquifer flow unit of Edem by means of stratigraphic modified Lorenz plot (SMLP) employing vertical electrical sounding. The results from the vertical electrical sounding field data analysis shows that resistivity and thickness of the aquifer layer ranges from 34.8 to 67561.2 Ωm and 29.7 to 147.6 m respectively having an average aquifer thickness value of 70.248 m. Aquifer layer permeability and fractional porosity range from 1.5942 to 1657444 mD and 0.2558 to 0.3265 respectively. Results from stratigraphic modified Lorenz plot delineated a total of eight flow-units, FU1, FU2, FU3, FU4, FU5, FU6, FU7, and FU8 for the aquifer units and three different process speeds. Aquifer flow units FU1, FU3, and FU8 fall within the speed zone, flow units FU5 and FU7 are associated with the baffle zone, while flow units FU2, FU4, and FU6 make up the barrier zone of the process speeds. The aquifer flow unit speed ranges from 265406.4 to 5076424 mD with an average value of 826310.2 mD. The contour maps generated revealed the western part of the study area as characterized with high values of aquifer storage capacity and aquifer flow capacity with the highest storage and flow capacities delineated along the northwestern part of the study area. The Dykstra-Parsons coefficient of 0.99 revealed an extremely heterogeneous aquifer in the study area. This flow unit analysis will serve as a guide in accurate design and management of the aquifers.

A Novel Energy Lifting Approach Using J-Function and Flow Zone Indicator for Oil Fields

The X field is located in the southwestern part of block NX89 of Kentan Basin in Libya. This field is produced from Hailan multilayer consolidated sandstone with moderate rock property and a relatively low energy supplying. The reserve of subsurface energy sources is declining with years. Therefore, techniques were combined to achieve the energy optimization and increase hydrocarbon recovery. In order to understand the subsurface formation of the reservoir and facilitate oil production, global hydraulic element technique was used to quantify the reservoir rock types. In addition, stratigraphic modified Lorenz plot was used for reservoir layering. Reservoir heterogeneity was identified using stratigraphic modified Lorenz plot and Dykstra-Parsons coefficient. Leverett J-function was used to average the 13 capillary pressure curves into four main curves to represent the whole reservoir based on flow zone indicator values. Capillary pressure was calculated and plotted with normalized water saturation; a single average curve was defined to represent the rest of the curves. Water saturation was calculated using single and multiple J-functions and compared with the available logs. With multiple J-functions, the matching results were good for both high and low-quality layers, whereas using a single J-function, the match was poor, especially for low FZI layers such as H4c and H6a. Four rock types were identified for this reservoir ranging from medium to good reservoir quality and six different layers were obtained. The reservoir was heterogeneous with a Lorenz coefficient value of approximately 0.72 and a Dykstra-Parsons value of 0.70. All approaches used in this paper were validated and showed improved hydrocarbon recovery factor.

Reservoir zonation in the framework of sequence stratigraphy: A case study from Sarvak Formation, Abadan Plain, SW Iran

Located in the northeast of the Arabian Plate, Zagros Basin hosts some of the most significant hydrocarbon reservoirs in Iran, including the Sarvak Formation. It has been dated back to the Middle Cretaceous and exhibits a dominantly carbonate lithology. In this study, petrographic and petrophysical data of the Sarvak Formation were analyzed. The results of the petrographic study showed that the formation was deposited in a homoclinal carbonate-ramp depositional environment and exposed to diagenetic processes in three depositional environments: marine, meteoric, and deeply buried environments. The stratigraphic modified Lorenz plot (SMLP) method was used to distinguish between the reservoir and non-reservoir zones. By integrating the petrographic and petrophysical findings, stratigraphic relationships among the identified zones were assessed. Accordingly, three third-order sedimentary sequences were identified on the Middle Cenomanian-to-Middle Turonian section within the studied formation. Two disconformities were detected in the Upper Sarvak, namely Cenomanian-Turonian disconformity (CTD) and Middle Turonian disconformity (MTD). The highest-quality reservoir zones were related to the CTD. The porosity resulted from the karstification, meteoric diagenesis, and significant dissolution beneath the CTD was found to have greatly increased the reservoir quality. Later on, however, the sediments were overmatured under the impact of the MTD, which is known to take a long time to occur, with their porosity largely decreased, ending up with a much lower reservoir quality. In general, the sedimentary facies were found to be the most important factors controlling the distribution of the reservoir zones across the Sarvak Formation, followed by the diagenetic processes. The findings provided an insight into the factors controlling the reservoir quality in the Sarvak Formation within the study area and the Arabian Plate.

GAWPS: A MRST-based module for wellbore profiling and graphical analysis of flow units

Several graphical methods have been developed to understand the stratigraphy observed in wells and assist experts in estimating rock quality, defining limits for barriers, baffles, and speed zones, and in particular, delineating hydraulic flow units. At present, there exists no computational tool that bundles the main graphical methods used for defining flow units. This paper introduces an add-on module to the MATLAB Reservoir Simulation Toolbox that contains computational routines to carry out such graphical analyses, both qualitatively and quantitatively. We also describe a new secondary method defined as the derivative of the stratigraphic modified Lorenz plot, which we use to classify depth ranges within the reservoir into barriers, strong baffles, weak baffles, and normal units, based on flow unit speed over those depths. We demonstrate the capabilities of the “Graphical Analysis for Well Placement Strategy” module by applying it to several case studies of both real and synthetic reservoirs. Cited as: Oliveira, G.P., Rodrigues, T.N.E., Lie, K.-A. GAWPS: A MRST-based module for wellbore profiling and graphical analysis of flow units. Advances in Geo-Energy Research, 2021, 6(1): 38-53. https://doi.org/10.46690/ager.2022.01.04

Implementation of a Petrographical and Petrophysical Workflow Protocol for Studying the Impact of Heterogeneity on the Rock Typing and Reservoir Quality of Reefal Limestone: A Case Study on the Nullipore Carbonates in the Gulf of Suez

AbstractThis study focuses on the heterogeneity of the middle Miocene syn‐rift Belayim nullipore (reefal) marine sequences in the Gulf of Suez and its impacts on reservoir quality. The sequences consist of coralline algal reef limestones with a highly complex dual‐porosity system of primary and secondary porosities of widely varying percentages. To achieve a precise mathematical modeling of these reservoir sequences, a workflow protocol was applied to separate these sequences into a number of hydraulic flow units (HFUs) and reservoir rock types (RRTs). This has been achieved by conducting a conventional core analysis on the nullipore marine sequence. To illustrate the heterogeneity of the nullipore reservoir, the Dykstra‐Parsons coefficient (V) has been estimated (V = 0.91), indicating an extremely heterogeneous reservoir. A slight to high anisotropy (λk) has been assigned for the studied nullipore sequences. A stratigraphic modified Lorenz plot (SMLP) was applied to define the optimum number of HFUs and barriers/baffles in each of the studied wells. Integrating the permeability‐porosity, reservoir quality index‐normalized porosity index (RQI‐NPI) and the RQI‐flow zone indicator (RQI‐FZI) plots, the discrete rock types (DRT) and the R35 techniques enable the discrimination of the reservoir sequences into 4 RRTs/HFUs. The RRT4 packstone samples are characterized by the best reservoir properties (moderate permeability anisotropy, with a good‐to‐fair reservoir quality index), whereas the RRT1 mudstone samples have the lowest flow and storage capacities, as well as the tightest reservoir quality.

زون‌بندی مخزنی بر اساس داده‌های پتروگرافی و پتروفیزیکی (مطالعه موردی: بخش بالایی سازند سروک در یکی از میدان‌های نفتی ناحیه دشت آبادان، جنوب غربی ایران)

Summary In this study, results of microscopic studies on thin sections, core porosity data, and petrophysical charts along a well were used to evaluate the reservoir quality of the upper part of the Sarvak Formation in one of the oil fields in Abadan Plain. This research showed that SMLP-based zonation can be applied on a field scale as it could appropriately represent the heterogeneity of the Sarvak reservoir at a large scale. Introduction The main purpose of the study is to investigate the reservoir quality of the upper part of Sarvak Formation in an oilfield within Abadan Plain by analyzing the facies and sedimentary environment, pore system, diagenetic processes, electrofacies, and flow units. To this end, a set of microscopic thin section data, core porosity data, and well logs were employed as input data. The main advantages of the proposed methodology include its ability to predict and justify changes in reservoir quality, its contribution to reservoir modeling and reservoir zonation, and the resultant reduction of the drilling cost in the studied oilfield. Methodology and Approaches The set of input data used in this study included 269 m of drilling cores, 694 thin sections prepared from the cores, porosity-permeability data from 548 core plug samples, and petrophysical logs including gamma, neutron, sonic, density, and resistivity reading at a key well in an oilfield within Abadan Plain, southwestern Iran. Results of petrographic studies (i.e., sedimentary texture, facies belts, diagenetic processes, and pore systems) and electrofacies were incorporated into a framework for identifying the zones introduced by SMLP, and the relationship between them was examined and interpreted. Results and Conclusions Based on the microscopic studies, it was found that the formation was composed of 5 facies belts, namely tidal flat zone, lagoon, shoal, middle ramp, and outer ramp facies were deposited. Dissolution, fracturing, cementation, compaction, and dolomitization were identified as the most important diagenetic processes affecting the reservoir quality in Sarvak Formation. Electrofacies (EF) were determined based on well charts and hierarchical clustering analysis. Using two petrophysical methods, namely, flow zone index (FZI) and stratigraphic modified Lorenz plot (SMLP), we ended up detecting 5 and 7 flow units, respectively. Finally, microscopic analysis of thin sections and investigation of electrofacies and hydraulic flow units in the framework of reservoir zonation by using the SMLP were devised to review the zonations and interpret them appropriately. As a result, the grain-supported facies related to the shoal and the middle ramp environments and the diagenetic processes enhancing the reservoir quality (e.g., dissolution and fracturing) were found to lead to the best-reservoir quality zones. On the other hand, the poor reservoir quality zones were found to be a result of the mud-supported facies of the middle and outer ramp, tidal flat, and lagoon environments, and adverse diagenetic processes such as cementation, compaction, and dolomitization. Results of this study showed that reservoir zonation using the SMLP can be of help in the interpretation of reservoir heterogeneities in the upper part of the Sarvak Formation at the field scale.

Delineation of sandstone reservoirs of Pletmos Basin offshore South Africa into Flow Units using Core Data

AbstractThe present study is focused on the comparison of petrophysical rock typing and zonation methods of the Valanginian age sandstone in the Pletmos Basin offshore South Africa, to produce a zonation scheme for the low-permeability shaly sandstone reservoirs from core porosity and permeability data. The Valanginian age sediments of the Lower Cretaceous consist predominantly of a shallow marine sequence with interbeds of siltstone, claystone, generally fine-grained sandstone, and glauconitic, with varying amounts of an argillaceous matrix. A core description report was used in conjunction with a gamma-ray log to group rock types into different facies based on texture and grain size. Three different facies were identified as facies 1, a moderately sorted fine to medium-grained glauconitic sandstone; facies 2, a fine to very fine-grained glauconitic sandstone, moderately sorted; facies 3, a very fine sandstone to siltstone, laminated, argillaceous and bioturbated. Three independent reservoir zonation methods (Winland r35 pore throat, Hydraulic Flow Unit, and Stratigraphic Modified Lorenz Plot) were applied to three wells (SW1, SW2, and SW3) for which wireline logs, core porosity, and permeability data are available. Results were analyzed and compared with facies used as a context for the identification of rock types and zones. The results revealed eleven zones, grouped as moderate, very-low, and tight zones. The moderate flow zone is the best reservoir quality rock composed of macroporous rock type, ranked, as good rock type associated with facies 1. Three very-low flow zones were identified, which are of a microporous rock type, ranked as poor quality rock, associated with facies 2. Eight tight zones were revealed, which are of nanoporous rock type ranked as an impervious rock. The tight flow zone is the most reduced rock quality associated with facies 3. This study has developed a zonation scheme that will be used to locate other flow zones as well as to investigate whether the units/zones identified extend to other parts of the field.

Reservoir Flow Unit Analysis of Akos Field in Niger Delta

In this study, the flow units of reservoirs of Akos field have been computed with the Stratigraphic Modified Lorenz plot. Cumulative flow capacity and cumulative storage capacity were used for constructing the Stratigraphic Modified Lorenz Plot (SMLP). The flow capacity and storage capacity are functions of calculated permeability and porosity values considering their sampling depth. The porosity and permeability were obtained from composite well logs of eight oil wells in the study area. Two reservoirs A and B were delineated from the well logs. The stratigraphic Modified Lorenz Plots (SMLP) revealed a total of one hundred and twelve (112) Flow units (FU) in the two observed reservoirs A and B. Reservoir A has a total of 53 FU (25 speed zones, 18 baffle zones and 10 barrier zones) and reservoir B has a total of 59 FU (29 speed zones, 16 baffle zones and 14 barrier zones) which cut across all the wells. The flow units in both reservoirs fall within the speed zones, baffles and barrier unit categories. The speed zone units with equal flow and storage capacities are the dominant flow units in both reservoirs. This is an indication that the sediments have good reservoir qualities. The baffle zones have more storage capacity than the speed zones. The barrier zones within the reservoirs are acting as a seal to the flow of fluid.

KLASIFIKASI PETROFISIKA TIPE BATUAN UNTUK MEMPREDIKSI KUALITAS RESERVOAR PASIR SERPIHAN PADA FORMASI TALANG AKAR, CEKUNGAN ONWJ

Hydrocarbons were accumulated in reservoir, the reservoir has a lot of types depending on the geological conditions and the constituent mineral. In ONWJ basins, sub-basins Arjuna, Talang Akar Formation is sand splintersreservoir type. The presence of clay in a reservoir will reduce the resistivity and increase thesaturation, so it takes a multimineral analysis and the reservoir qualityclassification. In this study, physical properties (porosity, permeability, Rw, and saturation) and the quality of the reservoir can be identified through petrophysical analysis by utilizing log data and core analysis, and the rocktypeprediction(using R35 Winland or HFU method). In this study 5 wells (IX-A1, IX-13, IX-4, IX-7 and IX-8)used and found eight hydrocarbon zones, 6 are validated by the DST (drill steam test)data, androck type method that suitable is the method of HFU (hydraulic flow units) due to the coefficient of correlation between porosity and permeability shows a value of 0.75, based on the calculations, the eight types of rock is conclude, where the dominance of the rock typeis the type 12 with a pore size between 5-10 microns, type reservoir rocks in this study belong to the lithofacies distributary channel and mouthbar sand. By knowing the petrophysical property values, it can determine reservoir productivity and determine the zone eligible to be produced or not, by using curve SMLP (Stratigraphic Modified Lorenz Plot).

Application of integrated rock typing and flow units identification methods for an Iranian carbonate reservoir

During the exploration phase of any oil and gas field, recognition of borehole type, its completion approach, and understanding of the future reservoir performance are directly interrelated to identification of the reservoir's rock types and flow units. Identifying different geological events, lithofacies characteristics, diagenetic processes, and level of heterogeneity can be the first step for knowing rock types and consequently flow units in its reservoir layers. These result in an acceptable dynamic model of a field development and relatively reliable production forecasts.Focus of this paper is on rock typing and flow unit classification for a carbonate reservoir of a green field. Four petrophysical methods including Rock Fabric Number (RFN), Winland porosity-permeability plot (R35), Reservoir Quality Index/Flow Zone Indicator (RQI/FZI), and Bulk Volume Water (BVW) were implemented on four exploration wells. At the next step graphical tools (Stratigraphic Modified Lorenz Plot (SMLP), Modified Lorenz Plot (MLP) and Stratigraphic Flow Profile (SFP) were used to locate established flow units and rock types within the reservoir column. Lastly, variation and frequency of defined flow units have been used to achieve a satisfactory understanding of the level of heterogeneity and the possible effect on well production.Integration of defined flow units by different methods inferred a high level of heterogeneity in the studied reservoir and the BVW was chosen as the best method of rock typing for feeding to the static model. The BVW method assists in considering main variation of reservoir properties meanwhile avoid complexity of models. During modelling, choosing an optimum number of rock types for fine-grid model with small dimensions cells (50 m*50 m*1 m) can help to separate different layers vertically without necessity of dividing them to many distinct subzones. Usually, groping numerous subzones during up scaling is confusing and complicate; likewise, in a coarse grid may omit or mix some frequency of thin seal and productive subintervals in reservoir zones. Comparing achieved flow unit classification with outcomes of production test showed in this reservoir with high level of heterogeneity an adequate type of well is vertical and highly deviated ones, moreover, dual completion can be the best type of production which separate high and low productive zones.

Chemical compaction features as potential barriers in the Permian-Triassic reservoirs of Southern Iran

Chemical compaction features are important diagenetic imprints that generally interrupt reservoir quality in most carbonate reservoirs. In the Permian-Triassic reservoirs of South Pars Field, they are recorded in various types and intensities. High- to low amplitude stylolites and solution seams are concentrated within the K1–K4 units of the upper Dalan and Kangan formations, depending on their facies characteristics, diagenetic alterations and dominant lithology. In these units, there are some meaningful trends between the chemical compaction zones and sequence stratigraphic positions including the systems tracts of third-order sequences. Control of chemical compaction on reservoir characteristics is evaluated by using the results of petrographic studies, petrophysical logs and core poroperm measurements. Internal reservoir architecture of the studied reservoirs is determined using the both hydraulic flow units and stratigraphic modified Lorenz plot approaches. Identified baffle and barrier units show close correspondence with chemically-compacted zones. This indicates that zones with high concentration of stylolites and solution seams can be considered as small-scale vertical flow barriers in the Permian-Triassic reservoirs of South Pars Field.

Determination of Flow Units in Carbonate Reservoir With Multiscale Karst Morphology

The Tahe reservoir, one of the largest scale carbonate reservoirs in western China, has very special cavities and fractures. The size of the cavities ranges from millimeter to meter scale, and the size of the fractures ranges from hundreds micrometers to millimeters scale. The length of some cavities can even reach kilometers. However, based on views of core testing results, there is insignificant flow in the rock matrix. This paper introduces a new and refined method to determine flow units in such Karst carbonate reservoirs. Based on fractal theory, fluid flow patterns can be divided into three types by using production data of the Tahe reservoir. Through porosity and permeability statistics of production layers on the established geological model, flow boundaries of different flow patterns were proposed. Flow units were classified in terms of the flow boundaries. As for refined flow units, subcategory flow units were determined by three graphical tools: the limit of dynamic synthesis coefficient (DSCL) method, modified flow coefficient (MS1 and MS2, which are derived by the Forchheimer equation) curve, and the stratigraphic modified Lorenz plot (SMLP). All the parameters of graphical tools help to reconcile geology to fluid flow by illustrating the important link between geology, petrophysics, and reservoir engineering. The use of this technique is illustrated with data from a specific block of the Tahe reservoir.

A geological based reservoir zonation scheme in a sequence stratigraphic framework: A case study from the Permo–Triassic gas reservoirs, Offshore Iran

Reservoir zonation can lead to an insight about the lateral and vertical distribution of reservoir and non–reservoir zones from bore hole to regional scales. Based on available data sets, scale of study and purposes, there are various reservoir zonation schemes, but correlatability is crucial in any reservoir zonation procedure. In this study, it is attempted to create a reservoir zonation scheme based on geological attributes in the Permo–Triassic successions of the eastern Persian Gulf area, which can be used to inter–field (regional) investigation and correlation. Then, the applicability of two routinely used reservoir zonation procedures including hydraulic flow units (HFU) and flow units based on a stratigraphic modified Lorenz plot was examined. The petrophysical based HFUs were not correlatable between the studied wells and fields. The larger scale flow units were correlatable at the field and to some extent inter–field scales. But, the identified geological reservoir zones (GRZs) were correlatable at both intra– and inter–field scales in a sequence stratigraphic framework. GRZs were defined based on sharp changes in depositional facies, diagenetic features or both and also any meaningful accompaniment in diagenetic features and pore types, which show similar sequence stratigraphic positions. This indicates a close relationship between the depositional sequences and post–depositional diagenetic processes, and therefore GRZs are linked to a sequence stratigraphic framework. The GRZ concept may be applicable to reservoir characterization of the Permo-Triassic successions in the Persian Gulf and adjacent areas. However, this concept can only be applied if the combined depo-diagenetic processes and the resulting reservoir quality are controlled by sequence stratigraphic position without pervasive and non-facies related late diagenetic overprints.

Identification of Barriers and Productive Zones Using Reservoir Characterization

The most common complication faced by petroleum engineers is the description of a reservoir, both accurately and efficiently. Inadequate and insufficient reservoir characterization lead most enhanced oil recovery and secondary recovery projects to fail and also makes it difficult to deal with heterogonous reservoir. An accurate description of a reservoir is vital to the reservoir management and achieving maximum oil recovery. Reservoir characterization plays a very important role in descripting the storage and flow capacity of a reservoir and also plays a decisive role in reservoir simulation. The main objective of this research is to identify reservoir barriers and productive zone using reservoir characterization, in this study some of the most useful methods such as Flow Zone Indicator (FZI), Discrete Rock Type (DRT), Winland R35 methods were applied to 4 different wells to identify the rock types and flow units developing a static reservoir characterization model. To achieve the objective of this research the static model is transformed into a dynamic model by introducing graphical method such as stratigraphic flow profile (SFP), stratigraphic modified Lorenz plot (SMLP) and modified Lorenz plot (MLP) to easily quantify reservoir flow units based on physical structure, storage capacity, flow capacity, rock type and reservoir process speed. The physical structure permits the flow units to be interpreted in a stratigraphic model arrangement, determining well-to-well correlation schemes; the main aim of understanding the flow unit's characterizations is to identify the barriers, speed zones and baffles.

Flow-units verification, using statistical zonation and application of Stratigraphic Modified Lorenz Plot in Tabnak gas field

The relationship between two main reservoir parameters being porosity and permeability, in the carbonate rocks is very complex and obscure. To get a better understanding on flow behavior, the relationship of porosity and permeability of reservoir units, reservoir zonation and flow units were defined. The significance of dividing the sedimentary intervals into flow units reflects groups of rocks that have similar geologic, physical properties and depositional environment that affect fluid flow. Variations in rock properties result from depositional, diagenetic and post-depositional changes. A flow unit is a volume of a reservoir rock that is continuous laterally and vertically and has similar averages of those rock properties that affect fluid flow. Different methods exist for the zonation of reservoirs based on petrophysical data and well logs; among them are: Permeability–Porosity cross plot, Pickett and Soder and Gill methods. In this study, the flow units are determined in Tabnak gas field in South of Iran based on Testerman Zonation Technique and Stratigraphic Modified Lorenz Plot (SMLP) methods. For determining these units, conflation of petrophysical data and comparing porosity and permeability of cores are done for verification three wells. By comparing flow-units derived from two methods, it was realized that in permeable zones they have a relatively valid correlation.