scholarly journals Fuzzy Logic in Carbonate Reservoir Quality Assessment: A Case Study from Tarim Basin, China

2017 ◽  
Vol 10 (1) ◽  
pp. 195-203
Author(s):  
Weifu Liu
Keyword(s):  
Fuzzy Logic ◽  
Quality Assessment ◽  
Tarim Basin ◽  
Carbonate Reservoir ◽  
Carbonate Reservoirs ◽  
Reservoir Quality ◽  
Pore Throat ◽  
Throat Radius ◽  
Single Well ◽  
Factor Set

Introduction: To address reservoir quality assessment in highly complex and heterogeneous carbonate reservoirs, a methodology utilizing fuzzy logic is developed and presented in this paper. Based on carbonate reservoir characteristics, three parameters reflecting the macroscopic and microscopic of storage abundance, permeability, and median of pore throat radius were selected to establish the factor set and the evaluation criteria. After analysis of core and test data, a membership function is constructed by semi-drop trapezoid method and the weight formula is also determined by reservoir factor sub-index. The developed method then is used to evaluate a carbonate reservoir in the Tarim Basin in China. Based on the result of single well evaluation, the plane classification map of the carbonate reservoir quality is constructed. Results obtained from reservoir quality assessment in the K32 well show that I-level, II-level, and III-level reservoir qualities account for 58%, 37%, 5% of the reservoir, respectively. The results are consistent with the actual production data demonstrating reliability of the proposed method for reservoir quality assessment practices in usually very complex and heterogeneous carbonate reservoirs. Background: Carbonate reservoirs are complex and heterogeneous and this makes their evaluation a difficult task. Objective: To overcome the uncertainties associated with evaluation of complex carbonate reservoirs a reliable method to accurately evaluate carbonate reservoirs is presented. Methods: Fuzzy logic is used to evaluate a carbonate reservoir from Tarim Basin in China. Based on carbonate reservoir characteristics, three parameters reflecting the macroscopic and microscopic of storage abundance, permeability, and median of pore throat radius are selected to establish the factor set and to evaluate the criteria of carbonate reservoir. After the analysis of core and test data, a membership function is reasonably constructed by semi-drop trapezoid method and the weight formula is also determined by reservoir factor sub-index. Results: An effective methodology for the evaluation of reservoir quality in carbonate reservoirs is established by using fuzzy logic. In addition, an example reservoir from China is used to demonstrate the applicability of the developed method. Conclusion: Based on the result of single well evaluation, the plane classification map of the carbonate reservoir is constructed. Favorable zones in the reservoir are also delineated. Evaluation results are consistent with the actual production data of gas and oil which proves that the proposed method is instrumental in reservoir quality assessment.

Polymer Injection to Unlock Bypassed Oil in a Giant Carbonate Reservoir: Bridging the Gap Between Laboratory and Large Scale Polymer Project

2021 ◽  
Author(s):  
Clement Fabbri ◽  
Haitham Ali Al Saadi ◽  
Ke Wang ◽  
Flavien Maire ◽  
Carolina Romero ◽  
...  
Keyword(s):  
High Salinity ◽  
Water Injection ◽  
Cross Flow ◽  
Carbonate Reservoir ◽  
Carbonate Reservoirs ◽  
Laboratory Work ◽  
High Permeability ◽  
Polymer Injection ◽  
Single Well ◽  
Pilot Design

Abstract Polymer flooding has long been proposed to improve sweep efficiency in heterogeneous reservoirs where polymer enhances cross flow between layers and forces water into the low permeability layers, leading to more homogeneous saturation profile. Although this approach could unlock large volumes of by-passed oil in layered carbonate reservoirs, compatibility of polymer solutions with high salinity - high temperature carbonate reservoirs has been hindering polymer injection projects in such harsh conditions. The aim of this paper is to present the laboratory work, polymer injection field test results and pilot design aimed to unlock target tertiary oil recovery in a highly heterogeneous mixed to oil-wet giant carbonate reservoir. This paper focuses on a highly layered limestone reservoir with various levels of cyclicity in properties. This reservoir may be divided in two main bodies, i.e., an Upper zone and a Lower zone with permeability contrast of up to two orders of magnitude. The main part of the reservoir is currently under peripheral and mid-flank water injection. Field observations show that injected water tends to channel quickly through the Upper zone along the high permeability layers and bypass the oil in the Lower zone. Past studies have indicated that this water override phenomenon is caused by a combination of high permeability contrast and capillary forces which counteract gravity forces. In this setting, adequate polymer injection strategy to enhance cross-flow between these zones is investigated, building on laboratory and polymer injection test field results. A key prerequisite for defining such EOR development scenario is to have representative static and dynamic models that captures the geological heterogeneity of this kind of reservoirs. This is achieved by an improved and integrated reservoir characterization, modelling and water injection history matching procedure. The history matched model was used to investigate different polymer injection schemes and resulted in an optimum pilot design. The injection scheme is defined based on dynamic simulations to maximize value, building on results from single-well polymer injection test, laboratory work and on previous published work, which have demonstrated the potential of polymer flooding for this reservoir. Our study evidences the positive impact of polymer propagation at field scale, improving the water-front stability, which is a function of pressure gradient near producer wells. Sensitivities to the position and number of polymer injectors have been performed to identify the best injection configuration, depending on the existing water injection scheme and the operating constraints. The pilot design proposed builds on laboratory work and field monitoring data gathered during single-well polymer injection field test. Together, these elements represent building blocks to enable tertiary polymer recovery in giant heterogeneous carbonate reservoirs with high temperature - high salinity conditions.

SILICA DIAGENESIS AND PORE DEVELOPMENT IN PERMIAN SANDSTONES, SOUTHERN COOPER BASIN

1992 ◽  
Vol 32 (1) ◽  
pp. 325
Author(s):  
P.R. Tingate ◽  
P. Luo
Keyword(s):  
Reservoir Quality ◽  
Pore Throat ◽  
Throat Radius ◽  
Petrophysical Analysis ◽  
Reservoir Stimulation ◽  
Variable Permeability ◽  
Silica Diagenesis ◽  
Different Types ◽  
Primary Porosity ◽  
Cooper Basin

As the Cooper Basin is a mature petroleum province, more work is being directed towards further understanding the characteristics of the main reservoirs to maximise exploitation and recovery.To investigate the reservoir quality of Permian sandstones in the Cooper Basin, a study of the diagenesis and pore geometry has been carried out on the Toolachee and Patchawarra Formations in the Daralingie, Moomba and Della Fields. Following detailed petrography, scanning electron microscopy and cathodoluminescence observations, representative samples were selected for petrophysical analysis via mercury injection. The diagenetic studies show that early silica diagenesis has had a major impact on reservoir quality. Early quartz cement has helped rocks resist compaction so that primary porosity is preserved and allowed later porosity enhancement via dissolution.From petrophysical analysis, pores of different origin can be recognised and classified into three groups: inter-granular pore, kaolin framework pore and micropore groups. These groups can be distinguished quantitatively by their controlling pore throat radii. The radii for the various groups are ≥ 2.5 (µm (inter-granular), 2.5 − 0.5(µm (kaolin framework) and In the samples studied the relationship between the controlling pore throat radius (rpk) and permeability (k) is approximatelyk=rpk2Using this relationship, the calculated permeability associated with rocks containing only microporosity is less than 0.25 mD, making them unsuitable reservoirs. Permeability associated with the kaolin framework pore group ranges from approximately 0.25 to 6.25 mD, showing that it offers significant effective storage space for hydrocarbons, especially gas. The inter-granular pore group has variable permeability, ranging from near 6 to over 2000 mD. The causes for this variability are mainly diagenetic and include variable quartz cementation and different types of dissolution.Using the pore group division outlined above, different types of reservoirs can be distinguished. In addition, the results emphasise the importance of porosity within kaolin aggregates in Cooper Basin reservoirs and stress the need for adequate testing of initially unpromising horizons and careful choice of reservoir stimulation methods.

A Case Study of Complex Carbonate Reservoir Connectivity Analysis, Tarim Basin, China

2021 ◽  
pp. 1-41
Author(s):  
Zhangwu Meng ◽  
Zandong Sun ◽  
Guofa Li
Keyword(s):  
Tarim Basin ◽  
Seismic Data ◽  
Seismic Reflection ◽  
Carbonate Reservoir ◽  
Carbonate Reservoirs ◽  
Connectivity Analysis ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Diffraction Imaging ◽  
Reservoir Connectivity

The connectivity of complex carbonate reservoirs has an essential impact on the exploration and development of these reservoirs. From geological genesis, the connectivity of complex carbonate reservoirs is mainly controlled by faults and dissolution. Therefore, accurate identification of faults and karst caves is the key to studying reservoir connectivity. The Ordovician carbonate reservoir in the Hudson Oilfield of the Tarim Basin is used for the reservoir connectivity analysis study. Firstly, we calculate the coherence and curvature attributes and then merge the two attributes using a neural network algorithm. Finally, we use the ant tracking method to track the faults for the merged data. The results show that the approach substantially enhances deterministic faults that can be seen directly on the seismic data, and the subtle faults can also be identified. For reservoir identification, we use the diffraction imaging method to describe the karst reservoir in this study area. The results show that diffraction imaging can identify small-scale caves that cannot be well recognized on the seismic reflection data. Furthermore, the caves connected on the diffraction seismic data are isolated from each other on the seismic reflection data, making the connection between caves clearer. Based on the results of faults and caves identification, we analyze the reservoir connectivity of the study area using the oil pressure and daily production data. It indicates that the NNW and near-NS faults probably play a role in the connection of the reservoirs, while the NEE faults tend to block the connection of the reservoirs.

scholarly journals Relationship between pore throat and permeability of porous carbonate reservoir in the Middle East

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Lv Miaomiao ◽  
Song Benbiao ◽  
Tian Changbing ◽  
Mao Xianyu
Keyword(s):  
Quantitative Analysis ◽  
Carbonate Rocks ◽  
Carbonate Reservoir ◽  
Accurate Estimation ◽  
Poor Correlation ◽  
Pore Throat ◽  
Throat Radius ◽  
Pore Networks ◽  
Porosity And Permeability ◽  
Pore Types

AbstractA significant behavior of carbonate reservoirs is poor correlation between porosity and permeability. With the same porosity, the permeability can vary by three orders of magnitude or more. An accurate estimation of permeability for carbonate reservoir has been a challenge for many years. The aim of this study was to establish relationships between pore throat, porosity, and permeability. This study indicates that pore throat radius corresponding to a mercury saturation of 20% (R20) is the best permeability predictor for carbonates with complex porous pore networks. Quantitative analysis was made to achieve three different patterns of pore throat for 417 carbonate samples which cover all pore types of carbonate rocks. Different relationships between porosity, pore throat radius, and permeability have been identified in different patterns, which are utilized to predict more accurate permeability by different pore throat patterns.

scholarly journals A reservoir quality evaluation approach for tight sandstone reservoirs based on the gray correlation algorithm: A case study of the Chang 6 layer in the W area of the as oilfield, Ordos Basin

2021 ◽  
pp. 014459872199851
Author(s):  
Yuyang Liu ◽  
Xiaowei Zhang ◽  
Junfeng Shi ◽  
Wei Guo ◽  
Lixia Kang ◽  
...  
Keyword(s):  
Quality Evaluation ◽  
Comprehensive Evaluation ◽  
Ordos Basin ◽  
Reservoir Quality ◽  
Pore Throat ◽  
Tight Sandstone ◽  
Evaluation Approach ◽  
Correlation Algorithm ◽  
Gray Correlation ◽  
Sandstone Reservoir

As an important type of unconventional hydrocarbon, tight sandstone oil has great present and future resource potential. Reservoir quality evaluation is the basis of tight sandstone oil development. A comprehensive evaluation approach based on the gray correlation algorithm is established to effectively assess tight sandstone reservoir quality. Seven tight sandstone samples from the Chang 6 reservoir in the W area of the AS oilfield in the Ordos Basin are employed. First, the petrological and physical characteristics of the study area reservoir are briefly discussed through thin section observations, electron microscopy analysis, core physical property tests, and whole-rock and clay mineral content experiments. Second, the pore type, throat type and pore and throat combination characteristics are described from casting thin sections and scanning electron microscopy. Third, high-pressure mercury injection and nitrogen adsorption experiments are optimized to evaluate the characteristic parameters of pore throat distribution, micro- and nanopore throat frequency, permeability contribution and volume continuous distribution characteristics to quantitatively characterize the reservoir micro- and nanopores and throats. Then, the effective pore throat frequency specific gravity parameter of movable oil and the irreducible oil pore throat volume specific gravity parameter are introduced and combined with the reservoir physical properties, multipoint Brunauer-Emmett-Teller (BET) specific surface area, displacement pressure, maximum mercury saturation and mercury withdrawal efficiency parameters as the basic parameters for evaluation of tight sandstone reservoir quality. Finally, the weight coefficient of each parameter is calculated by the gray correlation method, and a reservoir comprehensive evaluation indicator (RCEI) is designed. The results show that the study area is dominated by types II and III tight sandstone reservoirs. In addition, the research method in this paper can be further extended to the evaluation of shale gas and other unconventional reservoirs after appropriate modification.

scholarly journals Injection-production optimization of carbonate reservoir based on an inter-well connectivity model

2021 ◽  
pp. 014459872199465
Author(s):  
Yuhui Zhou ◽  
Sheng Lei ◽  
Xuebiao Du ◽  
Shichang Ju ◽  
Wei Li
Keyword(s):  
History Matching ◽  
Water Injection ◽  
Field Application ◽  
Carbonate Reservoir ◽  
Production Optimization ◽  
Oil Field ◽  
Carbonate Reservoirs ◽  
Utilization Rate ◽  
Production Volume ◽  
Connectivity Model

Carbonate reservoirs are highly heterogeneous. During waterflooding stage, the channeling phenomenon of displacing fluid in high-permeability layers easily leads to early water breakthrough and high water-cut with low recovery rate. To quantitatively characterize the inter-well connectivity parameters (including conductivity and connected volume), we developed an inter-well connectivity model based on the principle of inter-well connectivity and the geological data and development performance of carbonate reservoirs. Thus, the planar water injection allocation factors and water injection utilization rate of different layers can be obtained. In addition, when the proposed model is integrated with automatic history matching method and production optimization algorithm, the real-time oil and water production can be optimized and predicted. Field application demonstrates that adjusting injection parameters based on the model outputs results in a 1.5% increase in annual oil production, which offers significant guidance for the efficient development of similar oil reservoirs. In this study, the connectivity method was applied to multi-layer real reservoirs for the first time, and the injection and production volume of injection-production wells were repeatedly updated based on multiple iterations of water injection efficiency. The correctness of the method was verified by conceptual calculations and then applied to real reservoirs. So that the oil field can increase production in a short time, and has good application value.

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