Reservoir Geological Model Research Articles

Experimental and numerical evaluation of CO2 huff-n-puff processes in Bakken formation

Experimental and numerical techniques have been developed to evaluate performance of CO2 huff-n-puff processes for unlocking resources from the Bakken tight oil formations. Experimentally, a series of coreflooding tests have been conducted by using core samples collected from the Bakken tight formation with a permeability range of 0.27–0.83mD. The performance of four recovery schemes (i.e., waterflooding, immiscible CO2 huff-n-puff, near-miscible CO2 huff-n-puff, and miscible CO2 huff-n-puff processes) has been comparatively evaluated. Theoretically, numerical simulation is performed to match the experimental measurements and then extended for evaluating field-scale CO2 huff-n-puff performance in the Bakken formation. Once the history matching on either the experimental measurements or the field geological model is completed, the tuned numerical model is then employed to optimize the injection pressure, soaking time, and production pressure, respectively. It is experimentally found that the waterflooding process leads to a higher oil recovery factor of 51.5% in comparison with the immiscible CO2 huff-n-puff process, while both the near-miscible and miscible CO2 huff-n-puff processes result in a higher recovery efficiency with the final recovery factors of 63.0% and 61.0% of OOIP, respectively. As for the history matched reservoir geological model, either a higher injection pressure or a lower production pressure usually results in better recovery performance but lower than the corresponding experimental measurements, while recovery factor can be optimized if soaking time of 15days is applied in this study.

Natural fracture distribution and a new method predicting effective fractures in tight oil reservoirs in Ordos Basin, NW China

Abstract Based on core, imaging logging, and thin section data, the distribution features of natural fractures in the tight oil reservoirs of the Ordos Basin are examined. The tight reservoirs in the Ordos Basin are rich in natural fractures, the fractures are mainly high-angle structural shear fractures in continuous step arrangement. Affected by rock mechanical anisotropy and present stress field, the NE trending fractures are the dominating seepage flow direction. These fractures feature high angle, small cutting depth, small aperture and short extension, controlled by rock lithology and single layer thickness in development degree, natural fractures are most developed in fine siltstone, most undeveloped in mudstone. The thinner the single layer, the more developed the natural fractures will be. Based on distribution features of natural fractures and quantitative evaluation of natural fracture characteristic parameters, by using reservoir matrix and natural fracture geologic modeling, a comprehensive reservoir geologic model considering natural fractures was built, by using reservoir numerical simulation modeling inversion, the plane distribution of effective natural fractures was found out, and the contribution of natural fractures to single well production was quantitatively evaluated at around 30.0%−50.0%. The research results are of great significance for well-pattern deployment and optimization of development technical policies of similar reservoirs.

Geological Model of Khasib Reservoir- Central Area/East Baghdad Field

The Geological modeling has been constructed by using Petrel E&P software to incorporate data, for improved Three-dimensional models of porosity model, water saturation, permeability estimated from core data, well log interpretation, and fault analysis modeling.
 Three-dimensional geological models attributed with physical properties constructed from primary geological data. The reservoir contains a huge hydrocarbon accumulation, a unique geological model characterization with faults, high heterogeneity, and a very complex field in nature.
 The results of this study show that the Three-dimensional geological model of Khasib reservoir, to build the reservoir model starting with evaluation of reservoir to interpretation of well log by using IP software for 14 wells, defining and divided the layers based on the GR Log and Resistivity log to nine layers and then maintained the fault model for a divided central area to four regions. Compared porosity log with porosity core to estimate correction porosity and enter this value to predict the permeability value for each layer by using FZI, and RQI method. The model Containing faults, horizons, zones, and layers depending on this data to make gridding by using pillar gridding.
 This paper presents a geological modeling and an uncertainty analysis for stock-tank original oil in place. The distribution of the faults is also discussed.

A comparison of statistical emulation methodologies for multi-wave calibration of environmental models.

Expensive computer codes, particularly those used for simulating environmental or geological processes, such as climate models, require calibration (sometimes called tuning). When calibrating expensive simulators using uncertainty quantification methods, it is usually necessary to use a statistical model called an emulator in place of the computer code when running the calibration algorithm. Though emulators based on Gaussian processes are typically many orders of magnitude faster to evaluate than the simulator they mimic, many applications have sought to speed up the computations by using regression‐only emulators within the calculations instead, arguing that the extra sophistication brought using the Gaussian process is not worth the extra computational power. This was the case for the analysis that produced the UK climate projections in 2009. In this paper, we compare the effectiveness of both emulation approaches upon a multi‐wave calibration framework that is becoming popular in the climate modeling community called “history matching.” We find that Gaussian processes offer significant benefits to the reduction of parametric uncertainty over regression‐only approaches. We find that in a multi‐wave experiment, a combination of regression‐only emulators initially, followed by Gaussian process emulators for refocussing experiments can be nearly as effective as using Gaussian processes throughout for a fraction of the computational cost. We also discover a number of design and emulator‐dependent features of the multi‐wave history matching approach that can cause apparent, yet premature, convergence of our estimates of parametric uncertainty. We compare these approaches to calibration in idealized examples and apply it to a well‐known geological reservoir model.

Sedimentological and diagenetic controls on reservoir properties in the Permian–Triassic successions of Western Persian Gulf, Southern Iran

The Permian–Triassic intervals in the Arabian Plate, namely the Khuff Formation and its equivalents, Dalan and Kangan formations, are among the most important gas reserves in the word. In Iran, they were the subject of several studies, which mainly focused on the supergiant South Pars Field. This study provides informations on the facies characteristics, diagenetic features and reservoir properties of these intervals in the western Persian Gulf (Golshan Field). As well, characteristics of the lower Dalan Member were evaluated for the first time from the Iranian sector of the Persian Gulf. Results of this study revealed the combined effects of depositional processes and diagenetic overprints on the reservoir quality of these intervals. Among the various diagenetic processes, anhydrite and calcite cementation has intense destructive effects on the reservoir quality of precursor porous facies. On the other hand, dolomitization has different effects on the reservoir quality. It has a positive effect, if it is not concomitant with overdolomitization and anhydrite cementation. Results of this study reveal that there is a close relationship between the depositional facies and diagenetic processes in the Dalan–Kangan sequences. Therefore, different reservoir/non-reservoir units of these intervals can be traced in a sequence stratigraphic framework. In order to constructing a sequence stratigraphic model, as a basis for geological reservoir model, various orders of sequences (third to fifth/sixth) were differentiated and correlated across the giant Golshan Field and supergiant South Pars Field.

Pattern-based conditional simulation with a raster path: a few techniques to make it more efficient

Mass transport is known to depend on heterogeneity in geological formations. This entails geological bodies with complex geometries. The major interest of multiple-point simulation is its ability to reproduce such geological features through the use of a training image. The idea behind the training image is to describe a geological concept with the expected geological architecture. Its structural content is then used to infer multiple-point statistics. This yields a database with a variety of possible patterns or events. In this paper, we present a hybrid algorithm combining geostatistical multiplepoint and texture synthesis techniques for simulating geological reservoir models constrained to hard data. The proposed algorithm is a two steps process, involving first analysis with the building of an organized database from the training image content, and second synthesis with the simulation of a realization. Various tests are performed to investigate the potential of the algorithm in terms of computation time and ability to properly reproduce the shapes and connectivity features of the objects represented in the training image. We also propose a few improvements to make the algorithm more efficient. Last, six examples are presented based upon different kinds of training images depicting large-scale channelized and fractured media as well as fine-scale porous media.

A review of three geostatistical techniques for realistic geological reservoir modeling integrating multi-scale data

Abstract This paper discusses new methodologies and workflows developed to generate geological models (1) that look more realistic geologically speaking and (2) that respect the well and seismic data characterizing the studied area. Accounting simultaneously for these two constraints is challenging as they behave the opposite way. The more realistic the geological model, the more difficult the integration of data. A first powerful approach is based upon the non-stationary plurigaussian simulation method. In this case, the available geological and seismic data make it possible to compute the 3D probability distributions of facies proportions, which are then used to truncate the Gaussian functions. A second method is rooted in the Bayesian sequential simulation. Recent developments have been proposed to extend this method to media including distinct facies. We suggest an improved variant to better account for the resolution differences between sonic logs and seismic data. This yields a more robust framework to integrate seismic data. A third innovative approach reconciles geostatistical multipoint simulation with texture synthesis principles. Geostatistical multipoint methods provide models, which better reproduce complex geological features. However, they still call for significant computation times. On the other hand, texture synthesis has been developed for computer graphics: it can help reduce computation time, but it does not account for data. We then envision a hybrid multi-scale algorithm with improved computation performances and yet able to respect data

A stochastic modeling study of H56 block in Daqingzijing oilfield

After years of water injection, the underground movement of oil and water in Daqingzijing oilfield is becoming more and more complex, and the distribution of reservoir parameters between wells and remaining oil is difficult to predict. The reservoir geological model of H56 block in Daqingzijing oilfield is established with the support of numerous data by applying stochastic modeling techniques; it effectively reproduces the reservoir heterogeneity and distributes parameters in uncertain area between wells. A sequential indicator simulation algorithm is used to simulate the sedimentary facies, and facies-controlled reservoir characteristics have been performed including the reservoir petrophysical parameters and variability in the wells. In order to verify model accuracy, a comparison of porosity and permeability between model data and actual data is essentially made, the fitting of reserves and the original reserves were compared, and the whole field and the single well between the model and the history data were compared; the model shows consistency that gives confidence in using the model for numerical simulation purposes.

Three-dimensional carbonate reservoir geomodeling based on the digital outcrop model

Abstract To better know the spatial distribution and architecture of carbonate reservoirs, three-dimensional carbonate reservoir geologic modeling based on the digital outcrop model (DOM) is proposed. Based on the traditional geologic study of outcrops, combined with digitizing the outcrop walls by utilizing the advanced instrument (LIDAR, RTK-GPS, GPR, Gigapan, etc), DOM is built, from which geological information based on measured sections and samples (litho-facies, porosity, permeability, sonic velocity) is extracted and used to build the 3-D outcrop reservoir geologic model by modeling software. Eventually the 3-D reservoir geologic model of outcrop is used to guide the subsurface research. The DOM-based 3-D reservoir geologic model for oolitic reservoirs of Triassic Feixianguan Formation in Yudongliang outcrop, NW Sichuan Basin, reveals more realistic spatial distribution of litho-facies, porosity and permeability, and their relationship, consequently providing more reliable evidence for seismic data interpretation and reservoir prediction of subsurface reservoirs with similar geological conditions.

Towards process-based geological reservoir modelling: Obtaining basin-scale constraints from seismic and well data

Forward stratigraphic modelling aims at representing the spatial distribution of lithology as a function of physical processes and environmental conditions at the time of deposition so as to integrate geological knowledge into the reservoir modelling workflow, thus increasing predictive capabilities of reservoir models and efficient exploitation of hydrocarbons. Application of process-based models in inverse mode is not yet well-established due to our limited insight into the information content of common subsurface data and the computational overhead involved.In this paper we examine inverse modelling of stratigraphy by using a typical dataset acquired in the hydrocarbon industry, which consists of seismic data and standard logs from a limited number of wells. The approach is based on the use of a forward model called SimClast, developed at Delft University of Technology, to generate facies distribution and architecture at the regional scale. Three different goodness of fit functions were proposed for model inversion, following an inference approach. A synthetic reservoir unit was used to investigate the impact of the uncertainty affecting the input parameters and the information content of seismic and well data.The case study showed that the model was more sensitive to the initial topography and to the location of the sediment entry point than to sea level. The depth of the seismic reflector corresponding to the top-reservoir surface was the most informative data source; the initial and boundary conditions of the simulation were constrained by evaluating the depth of this reflector across the whole basin area. In the reservoir area, where the seismic-to-well tie was established, the depth of the reservoir top does not give enough information for constraining the model parameters. Our results thus indicate that evaluation of basin-scale data permits reduction of uncertainty in (geostatistical) reservoir models relative to the current workflow, in which only local data are used. Effective use of well data to generate reservoir models conditioned to basin-scale scenarios requires post-processing methods to downscale the output of the forward model used in the experiments.

Mapping-While-Drilling System Improves Well Placement and Field Development

Technology Update Safety, efficiency, and accuracy are fundamental goals of well construction. But as the search for new oil and gas resources pushes into deeper waters and increasingly complex reservoirs, meeting these goals has become more challenging. A better understanding of the subsurface is one of the most efficient ways to mitigate drilling risk and optimize operations’ performances. The ability to map the reservoir in real time, while drilling, contributes to step change, such as understanding sweep efficiency in horizontal wells, landing and maximizing the length of drain within the optimal zone of the reservoir, and avoiding timeconsuming sidetracks or pilot holes. While the industry has several bedboundary mapping tools and services to delineate the reservoir as a well is drilled, their depth of investigation is limited. The best of these systems can map to a distance of 15 to 20 ft (4.6 to 6.1 m) from the borehole. These limitations have made it difficult to improve directional drilling within narrow pay zones or complex reservoirs containing faults, unconformities, and injected or channel sands. As a result, wellbore positioning may be suboptimal and drilling may be less efficient. Real-Time Reservoir Mapping Schlumberger’s GeoSphere reservoir mapping-while-drilling technology was developed to improve the operator’s understanding of the reservoir beyond the first few feet from the wellbore. The system employs an array of multiple subs in the bottomhole assembly to transmit deep directional resistivity measurements that map multiple reservoir layers with resistivity contrasts in real time (Fig. 1). The multispaced receiver array extends the radial depth of investigation to 100 ft (30 m) from the tool, revealing subsurface bedding and fluid-contact details at a true reservoir scale. The significant improvement in depth of investigation provides a reservoir- scale view, enabling operators to optimize landing, reduce drilling risk, and maximize reservoir exposure. By integrating real-time reservoir maps with seismic surveys, the interpretation of reservoir structure and geometry can be confirmed and refined, enabling a step transformation of field development strategy. The system provides a wealth of realtime reservoir knowledge that improves well construction by helping the operator accurately land a well in its target zone and steer the drill bit to keep the wellbore away from reservoir boundaries, dips, and fluid contacts. The real-time mapping data obtained also helps the operator refine the structural and geological reservoir models, thus optimizing plans for recovery and improving development strategies for the entire field. A Smooth Landing The ability to land the wellbore accurately into the reservoir’s target zone of interest is a critical first step in delivering a well that achieves its long-term production potential. Although pilot holes may provide good local information about the reservoir geology, they are often ineffective in predicting lateral geological variability—a critical factor when drilling into long horizontal pay zones. Similarly, well-to-well correlation alone cannot accommodate various structural shifts inherent in many downhole environments. The reservoir mapping-while-drilling technology’s extended depth of investigation, which is enabled by deep directional electromagnetic measurements, helps mitigate the risk of shallow or deep landings. The system supports the identification of large- or local-scale depth shift of the reservoir, providing a precise localization in true vertical depth (TVD) of the top of the reservoir and thus eliminating the cost of drilling a pilot hole. By providing a clear, real-time view of formation boundaries and fluid contacts, the system also avoids the risk of losing lateral exposure and creating sumps.

Study on the Temperature Distribution of High Pour Point Oil by Integrated Method Based on Well Log, Geological Data and Experiment

High pour point oil reservoir contains various typical properties; such as a kind of high freezing point, high paraffin content and high cloud point temperature reservoir, while the temperature is regarded as high sensitive parameter for oil reservoirs. The current research aim is to develop and assess the effect by cold water flooding, the structure and properties model was built with the combination method of reservoir geological modeling and simulation. Various degrees of cold damage have deep relation with paraffin deposition and reservoir channel plug due to decline of temperature below the cloud point temperature. Precipitated paraffin has changed the rheological properties of crude oil, which can increase filtration resistance and reducing the oil displacement efficiency. Furthermore, model simulation analysis results compared under two different conditions cold and hot water flooding and predicted the inter well temperature field distribution belongs to reservoir through the model numerical simulation. Present study depicts that the integrated method base on log, geological data and experiment can predict and analysis the temperature variation efficiently, while thermal displacement method has efficiently improved the high pour-point oil reservoir development effect, increasing oil mobility and enhancing oil recovery.

Varying prior information in Bayesian inversion

Bayes' rule is used to combine likelihood and prior probability distributions. The former represents knowledge derived from new data, the latter represents pre-existing knowledge; the Bayesian combination is the so-called posterior distribution, representing the resultant new state of knowledge. While varying the likelihood due to differing data observations is common, there are also situations where the prior distribution must be changed or replaced repeatedly. For example, in mixture density neural network (MDN) inversion, using current methods the neural network employed for inversion needs to be retrained every time prior information changes. We develop a method of prior replacement to vary the prior without re-training the network. Thus the efficiency of MDN inversions can be increased, typically by orders of magnitude when applied to geophysical problems. We demonstrate this for the inversion of seismic attributes in a synthetic subsurface geological reservoir model. We also present results which suggest that prior replacement can be used to control the statistical properties (such as variance) of the final estimate of the posterior in more general (e.g., Monte Carlo based) inverse problem solutions.

The Integrative Establishment of a Three-Dimensional Structure Model of Changling Gas Field in Changling Fault Depression

The three-dimensional (3D) geological modeling technique which is considered as an important skill of fine reservoir description has been gaining more and more attention. On one hand, it can efficiently promote the transformation of reservoir description from two-dimensional (2D) to 3D, and from qualification to quantification as well. The 3D reservoir geological model can be used as basic geological knowledge in terms of adjusting well patterns and indicating remaining oil distribution, through reflecting the spatial distribution characteristics and the variation of the reservoir physical property. On the other hand, the 3D modeling technique specializes in the representation of local micro features in comparison of regular ways. This article aims at subtly describing the structural modeling of Changling gas field of Changling fault depression. The result of this case study shows that the establishment of structural model is consistent with the understanding of fault development which was proved during the process of producing gas, thus the structural model has high reliability. Therefore, the structural model is of great guiding significance for the design of new well and the well patter optimization.

3D Microfacies Modeling of Tight Gas Reservoir: A Case from Changling Block, Jilin Oilfield

Reservoir geological model is actually used to characterize the reservoir structure and the spatial distribution of reservoir parameters and variations, thus, the prediction of reservoir parameters between wells is the core of geological modeling. In order to improve the accuracy of geological modeling, traditional cycle correlation and sequence stratigraphy method are combined to classfy the sub zones into single sand sections according to the sedimentary characteristics of Changling gas field. The study area has experienced many years of development. On one hand, researchers has a certain understanding of its underground geological characteristics. On the other hand, the well pattern is almost perfect, only the edge of study area needs a certain prediction. Therefore, deterministic and stochastic modeling methods are combined in microfacies modeling and a 3D regional microfacies model of Changling gas field is established finally.

Integrated Study of 3D Gas Reservoir Geological Modeling of North in Su11 Block

As the reservoir heterogeneity causes that the production accumulation of gas well has the large differences among gas wells and the gas production of a few wells decline fast, the 3D gas reservoir modeling is used for the reservoir heterogeneity characterization. By the 3D gas reservoir modeling of integrating the geological facies information into the facies modeling, a reasonable model of He8 and Shan1 formation was built, which includes the structural model, the facies model, and the reservoir properties model. Based on the model analysis, the gas sandstone belt distribution lies along the direction of from north to south. The gas sandstone in the 4, 5, 6 small layers of He8 and the 8 small layer of Shan1 is better than others. The horizontal well positions were proposed in the study area with better gas sandstone in the 3D gas reservoir model.

Application of Reservoir Geological Modeling in the Wang Longzhuang Block

Wang Longzhuang Block has entered the middle or later stage of high water cut and high recovery, quantity of remaining oil still remain in the reservoirs. The paper establishes the fine three-dimensional geological modeling on the basis of reservoir description of Wang Longzhuang Block, including the structure modeling, sedimentary microfacies modeling, reservoir parameter modeling and liquid distribution modeling, which forming the fine reservoir description of three dimensional visualization, and those provide evidences for the studies of the distribution of remaining oil in Wang Longzhuang Block.

Three-Dimensinal Structure Modeling of Lishui Depression, East China Sea Basin

Fine reservoir description plays an important role in oil and gas exploration and development, reservoir geological modeling is the core of fine reservoir description and the new technology developed in recent years of quantitatively characterizing reservoir as well. Petrel can be used to build three-dimensional visualization of quantitative reservoir by simulating and forecasting the reservoir characteristics and properties of parameters .And the reservoir unit is the targets of system modeling used to guide the re-awareness and tapping of the potential reservoir. This article describes three-dimensinal structure modeling of Lishui Depression East China Sea Basin with the help of powerful 3D visualization capabilities and integrated functional modules of the exploration and development, and results of case study show that the three-dimensinal structure model consists with its actual geological information, thus providing strong support for exploration and development of decision-making.

Reservoir Geological Model of Reef-Bank Carbonate Rocks of Ordavician in Tazhong Area, Tarim Basin, NW China

The reservoir of Lianglitage formaton mainly distribute in the Liang 1~Liang 2 section, and slight amount distribute in Liang 3 section. The microfacies are abundant and, and they apparently affect the development of the reservoir. Based on the geologic feature, we propound the concept:"microfacies combination". It is composed by two or several microfacies, and each microfacies have similar reservoir conditions. Using the seismic facies interpretation, combining the methods of deterministic modeling and stochastic modeling, the "microfacies combination" model is established. Appling the method that "microfacies combination" controls the modeling course, taking the wave impedance which has good corresponding relationship with reservoir as secondary variable, small layer application of stochastic modeling method based on the porosity model is finally established through the stochastic modeling method layer and layer. Considering the crack influence on permeability, the first step is establishing the fracture distribution model, then the permeability model is established taking the fracture distribution as secondary variable, which improves the practicability of permeability model.

Low-velocity Non-Darcy Flow Numerical Simulation of the Da45 Reservoir, Honggang Oilfield, Jilin, China

A newly developed low-velocity non-Darcy flow numerical simulator is applied to the Fuyu formation. The three-dimensional geological model of subject reservoir was established and 9 well plans were designed to obtain the optimal well adjustment plan. Additionally, the formation pressure gradient distributions were provided and the flow regions were divided to study the adaptability of different well adjustment plans. The numerical simulation of Da45 reservoir is an excellent opportunity to: (1) put the non-Darcy flow numerical simulator into application, (2) provide guidance for the Da45 reservoir, and (3) provide reference to the non-Darcy flow numerical simulation technique.