Reservoir Geological Model Research Articles

Reconstructing a Three-Dimensional Geological Model from Two-Dimensional Depositional Sections in a Tide-Dominated Estuarine Reservoir: A Case Study of Oil Sands Reservoir in Mackay River, Canada

A tide-dominated estuarine reservoir is an important oil reservoir. However, due to the force of bidirectional water flow, its internal structure is complex, and the heterogeneity is serious. Accurately establishing the tide-dominated estuarine reservoir model is a great challenge. This paper takes the Mackay River oil sands reservoir in Canada as the research object to establish the elaborate geological model of a tide-dominated estuarine reservoir. Through the meticulous depiction of core data, 14 kinds of lithofacies and nine kinds of architectural elements are identified, and the lithological and electrical response in sedimentary architectural elements is established. On this basis, the plane and vertical distribution of architectural elements, as well as the spatial superimposition patterns, are depicted and characterized through well seismic combination and plane and section interaction, and the representative plane and section architecture maps are obtained as 2D training images (TIs) for multi-point statistical modeling. The 2D TI is scanned by 2D data template to obtain the multi-point statistical probability of the 2D spatial architectural pattern. Then, the 2D multi-point probability is fused to generate three-dimensional (3D) multi-point statistical probability by the probabilistic fusion. Finally, Monte Carlo sampling is used to predict the spatial distribution of architectures, and an elaborate geological model of a tide-dominated estuarine reservoir is established. Compared with the traditional sequential indication modeling method, the point-to-point error of the model section based on the 2D section reconstruction method is only 25.92%, while the sequential indication modeling method is as high as 58.52%. Even far from the TI, the point-to-point error of the 2D section model is 33.13%. From the cross-validation, the average error of the 2D section is 11%, while the sequential indicator modeling error is 23.1%, which indicates that the accuracy of 2D reconstruction of the estuarine reservoir model is high, and this method is suitable for the establishment of the tide-dominated estuarine reservoir model.

Integrated Optimization of Hybrid Steam-Solvent Processes in a Post-CHOPS Reservoir with Consideration of Wormhole Networks

Abstract In this paper, an integrated technique has been developed to evaluate and optimize performance of hybrid steam-solvent processes in a post-cold heavy oil production with sand (CHOPS) reservoir with consideration of wormhole networks. A reservoir geological model is developed and calibrated by history matching reservoir pressure with oil, gas, and water production rates as the input constraints, while its wormhole network is characterized with a newly developed pressure-gradient-based (PGB) sand failure criterion conditioned to sand production. Once calibrated, the reservoir geological model incorporated with the wormhole network is then employed to evaluate and optimize performance of hybrid steam-solvent processes under various conditions, during which the net present value (NPV) is maximized with an integrated optimization algorithm by taking injection time, soaking time, production time, and injected fluid composition as controlling variables. It is found that a huff-n-puff process imposes a positive impact on enhancing oil recovery when wormhole network is fully generated and propagated. Addition of alkane solvents into CO2 stream leads to a higher oil recovery compared with that of the CO2 only method, while all hybrid steam-solvent injection achieve high oil recovery by taking advantage of both thermal energy and solvent dissolution. It is found that the NPV reaches its maximum value when the steam temperature is 200 °C for the optimized hybrid steam-solvent scenario.

3D Geological Modelling for Asmari Reservoir In Abu Ghirab Oil Field

Building a geological model is an essential and primary step for studying the reservoir’s hydrocarbon content and future performance. A three-dimensional geological model of the Asmari reservoir in Abu- Ghirab oil field including structure, stratigraphy, and reservoir petrophysical properties, has been constructed in the present work. As to underlying Formations, striking slip faults developed at the flank and interlayer normal. Abu Ghirab oilfields are located on the eastern anticlinal band, which has steadily plunged southward. 3D seismic interpretation results are utilized to build the fault model for 43 faults of the Asmari Formation in Abu Ghirab Oilfield. A geographic facies model with six different rock facies types are developed. This new modelling system should be capable of more clearly reflecting the connectivity of the oil body and the heterogeneity of the reservoir. To represent the vertical and horizontal heterogeneity and create a framework for the Asmari reservoir in the Abu Ghirab oil field, the Petrel software has been used to create a reservoir in a 3D model. This model was constructed using data from 55 wells located across the Asmari formation. The model demonstrates accurate estimations (porosity, saturation, and net to gross). These reservoir models directly impact the facies model’s computation of each layer of the net pay thickness of the reservoir. The final goal of the present work is to determine the initial oil in place (IOIP), which is found to be 269*106 sm3.

Lithology prediction method of coal-bearing reservoir based on stochastic seismic inversion and Bayesian classification: a case study on Ordos Basin

Abstract The Upper Palaeozoic coal measures in the Ordos Basin are rich in unconventional natural gas resources; however, the reservoir heterogeneity is relatively strong, which majorly restricts the accuracy of lithology prediction. Stochastic seismic inversion can synthesize the geological–geophysical information and establish high-resolution reservoir models based on geostatistical theory to obtain good inversion results; moreover, it can characterize reservoir lithology and fluid-bearing properties. The present study aimed to propose a high-precision lithology classification method for coal-bearing strata in the Ordos Basin, using Bayesian classification and stochastic seismic inversion. Initially, the reservoir geological model was established on the basis of the sequential Gaussian simulation algorithm, and stochastic seismic inversion was performed in combination with rock physics analysis, thereby obtaining a high-resolution elastic parameter data volume. Thereafter, the probability density function (PDF) and the probability density confusion matrix (PDF confusion matrix) were introduced to quantitatively analyse the ability of sensitive elastic parameters to distinguish lithology. Eventually, a logging lithology-fluid classification template was established based on the Bayesian classification technology; furthermore, a 3D lithology-fluid prediction was completed in combination with the inversion results. The prediction results are in good accordance with the logging data, which verifies the feasibility and effectiveness of the method.

Numerical simulation of productivity improvement of natural gas hydrate with various well types: Influence of branch parameters

The depressurization method and its modified scheme may be the best way to efficiently recover marine natural gas hydrate (NGH) from the reservoir. However, the capacity of existing engineering tests still poses considerable challenges to the industrial development of NGH. The complex structure wells can effectively promote the NGH contact area to enhance the exploitation efficiency, but the influence of branch parameters on gas production performance is not well sorted out for reference when performing well type optimization. Therefore, a geological model of an ideal hydrate reservoir and 65 wellbore models were established based on the geological data from station AT1 in Nankai Trough to analyze the influence of different branch parameters on the production capacity for various well types. Results indicate that the open hole section length is heavily constrained by the size of the reservoir for a single well. Compared to the corresponding single well, the multi-branch vertical wells can increase productivity by about 2.12%–51.18%, the multi-branch horizontal wells by about 0.99%–29.75%, and the cluster horizontal wells by about 54.36%–250.66% well. Moreover, the correlation coefficients of various branch parameters were analyzed as a reference when optimizing the well type and show that the cluster horizontal well has the highest sensitivity to branch parameters, which can significantly promote gas production efficiency, and is expected to break the threshold of industrial development.

Integrated Geologic Modeling of Fault-Block Reservoir: A Case Study of Ss Oil Field

The Ss oil field is found in the Turpan-Hami Basin’s Taipei Sag’s arc structural belt. This reservoir has a complicated character that has a significant impact on reservoir modeling and production prediction. This is a fault-block reservoir with ultralow permeability and low porosity that is divided by 57 faults. A static model was constructed by Petrel software based on reinterpretation of original log and core data and seismic information so as to clarify the spatial distribution of oil and water in the reservoir and to fit the development history of the later simulated reservoir. The integrated geological modeling approach is described in this work using the Ss reservoir as an example. A 3D structural model was built based on the spatial cutting relationship between the layer model and the fault, and the model’s quality was improved by breakpoint data, which more correctly depicted the structural properties of the research area. The lithofacies model was built within the restrictions of sedimentary facies using the sequential Gaussian simulation (SGS) stochastic modeling approach, which is paired with variogram data analysis to achieve the range value. To obtain the porosity and permeability model, the empirical formula of porosity and permeability, the SGS method, and the variation range value was input into the lithofacies model. It is important to note that the input lithofacies and property models have values of the same range. To gain the water saturation model, the distinct S w function formulas of the S 1 ~ S 4 layer derived from the J S w function were fed into the software. The NTG model was created according to the lower limit of porosity, which is 11%. The merging of detailed reservoir description and simulation led to the establishment of the Ss reservoir geological model. In the plane, the scale of the geological model has reached the meter level and decimeter level in the longitudinal direction. It also offers a framework for optimum reservoir modeling for complex fault-block reservoirs. This method improves the accuracy and precision of the model by reflecting the reservoir’s heterogeneity and the oil-water distribution. It could provide more details for future reservoir research such as fine reservoir simulation.

Numerical investigation on the long-term production behavior of horizontal well at the gas hydrate production site in South China Sea

The gas hydrates-bearing shaly silt reservoirs have the characteristics of high reserves and low permeability. The trial production test in South China Sea in 2020 shows that horizontal well has broad prospects for exploiting this kind of hydrate reservoir. However, due to the short trial production time, the long-term gas production behavior is still unknown and needs further investigation. Based on the trial production data, the geological model of multi-layer hydrate reservoir and multi-physical field coupling mathematical model are established. The influence of optimization of depressurization scheme and optimization of reservoir selection on the improvement of gas production efficiency and the influence of compaction effect on attenuation of gas production rate and reservoir stability are investigated. The results show that the pressure drop gradient and constant pressure duration are the key factors affecting step-wise depressurization. The constant pressure duration of single-stage depressurization is more appropriate between 5 and 10 days. When the pressure drops below the equilibrium pressure of hydrate phase, the pressure drop gradient of 0.2 MPa/d is the best for long-term stable gas production. On the other hand, the low permeability of HBL inhibits pressure drop propagation and heat transfer in this sublayer, keeping the gas production rate at a low level in the later stage of production. Further simulation shows that HBL with hydrate saturation of 19% ∼ 25% should be selected for the target reservoir in order to improve gas production efficiency. In addition, the compaction effect in the hydrate decomposition zone is obvious. Compared with the 30 days, the near-well effective permeability drops by more than 30% at 720 days, which is an important reason for the decrease of gas production rate in the later stage of production. Finally, the formation subsidence increases with the expansion of hydrate decomposition radius. The maximum formation subsidence is 0.31 m after 720 days of exploitation.

A proposal for reservoir geostatistical modeling and uncertainty analysis of the Curimã Field, Mundaú Sub-Basin, Ceará Basin, Brazil

Geological modeling represents one of the most important phases in reservoir characterization, in terms of workload, uncertainties and impact on final results. Modeling of oil reservoirs consists of the construction of the structural, stratigraphic, and petrophysical models; the calculation of the volume of oil in place; and the analysis of uncertainties. This study integrates reservoir data obtained from a variety of disciplines (geophysics, petrophysics, sedimentology, geology, and engineering), with the purpose to build a reliable geological reservoir model. To better represent the reservoir heterogeneities and integrate geological concepts and observations, geostatistical principles were applied to geological modeling. Therefore, the main objective of this study is to characterize the geometry and petrophysical properties of the Curimã Field, a deltaic reservoir in the Paracuru Formation of the Mundaú sub-Basin (Ceará Basin), using advanced geostatistics in order to evaluate the uncertainties of the reservoir volume. The integration of reliable data using geostatistical techniques to simulate reservoir properties provided a reliable geological model that matches, in terms of original volume in place, with that published by the Brazilian National Agency of Oil, Natural Gas and Biofuels (ANP). In addition, the sensitivity and uncertainty analysis of the variables used to build the geological model allowed to rank them according to their impact on the volume calculation - thus, from greatest to the lowest impact: i) the porosity cutoff for the NTG calculation; ii) the mean porosity value for sandstones; iii) the depth of water-oil contact. The final results were based on the analysis of 500 simulation runs and generated pessimistic and optimistic probabilistic scenarios (P10, P50, and P90) of the volume in place. These results will aid a detailed dynamic assessment of the exploitation potential of the Curimã Field.

Using geostatistics to generate a geological model of a sandstone petroleum reservoir in southern California

A variogram-based two-point geostatistical approach was applied to generate a geological model of a petroleum reservoir. The geology consists of a sandstone formation with uniformly inclined rock strata of equal dip angle structurally trapped by surrounding faults. Data exploration of electrical well logs using univariate/bivariate statistical tests and data transformation tools demonstrated the data to be statistically suitable for ordinary kriging and sequential Gaussian simulation. Three directions were defined as part of the variogram and the data were interpolated resulting in a 3D subsurface representation. Validation included performing a leave-one-out cross-validation for each well and statistical comparison of multiple realizations generated from a computed stochastic model. The results display a reliable geological model which indicate a direct causation of the continuity trends from the bedding attitude of the regional fault trap.

Геологическая модель строения рифейского карбонатного коллектора Юрубчено­Тохомского месторождения

In the article, based on the example of the Riphean sediments of the Yurubcheno-Tokhomskoye field, a version of the geological model of a carbonate reservoir is presented, aimed at identifying zones of improved reservoirproperties of cracks and caverns, based on the integration of geological data and core studies, prior to processing geophysical well survey data and interpretation of seismic data (scattered waves extraction).

Construction of Comprehensive Geological Model for an Iraqi Oil Reservoir

The paper generates a geological model of a giant Middle East oil reservoir, the model constructed based on the field data of 161 wells. The main aim of the paper was to recognize the value of the reservoir to investigate the feasibility of working on the reservoir modeling prior to the final decision of the investment for further development of this oilfield. Well log, deviation survey, 2D/3D interpreted seismic structural maps, facies, and core test were utilized to construct the developed geological model based on comprehensive interpretation and correlation processes using the PETREL platform. The geological model mainly aims to estimate stock-tank oil initially in place of the reservoir. In addition, three scenarios were applied based on sensitivity and uncertainty of five variables to determine an accurate estimation of stock-tank oil initially in place of the reservoir. The oil-water contact appeared to be the major uncertain parameter for stock-tank oil initially in place estimation because the available geological and field data was not enough to demonstrate it confidently, and only 13% of the total wells have penetrated the water zone in the Mishrif formation. The results of all scenarios indicate that the reservoir has huge stock-tank oil initially in place. The importance of developing this oilfield is validated by its very high stock-tank oil. This is where the value of this study becomes obvious.

Study of the Influence of Change in the Sandstone and Aleurolite Collector Properties on the Geological Modeling Quality

The initial data when creating both geological and hydrodynamic reservoir models can lead to errors in the modeling results and the subsequent distortion of the economic assessment and prospects of an oil or gas field. In order to improve the predictive reliability of reservoir hydrodynamic models, a core material study for the Tula object of four fields at the Babkinskaya anticline was carried out. The ratio analysis of porosity (Kp), rock density () and permeability (Kperm) for sandstones and aleurolites was carried out. Using a statistical core sampling based on porosity, density and permeability parameters, a separation by sedimentation processes was carried out for all considered lithological differences. For aleurolite and sandstone, we could talk about the differentiation of characteristics in the process of reservoir properties formation. The values of the parameters Kp, and Kperm, determined from laboratory core studies, were combined into a single statistical sample for the possibility of developing a methodology that would be aimed at describing Kperm using the integrated laboratory studies, namely by adding rock to the analysis. As a result of statistical analysis, it was found that permeability in intervals with low reservoir properties was controlled with the same significance degree by both porosity and rock density for all lithological differences. At the same time, the presence of highly permeable reservoirs for sandstones and their practically absence for aleurolites were noted. For all lithological differences, relationships were established between the permeability coefficient not only with porosity, but also with rock density. The methodology for constructing statistical models for calculating permeability from the values of porosity and rock density was implemented separately for the fields of the eastern and western parts of the Babkinskaya anticline. The described approach to taking into account the influence of rock density on permeability made it possible to determine the differentiated influence of lithotypes on the filtration characteristics of the reservoir. When modeling a reservoir, it is necessary to move from linearity to nonlinearity and take into account that the problem of permeability distribution in the reservoir being solved is somewhat more complicated: in different areas, sometimes the permeability is not controlled by porosity in principle, but somewhere only this parameter prevails. The methodical approach was recommended for 3D modeling. Revealing the relationships between the parameters was most important when developing a methodology for tuning the model in the interwell space. The development of a reliable estimate of permeability for the vast majority of wells will significantly improve the efficiency of hydrodynamic modeling. At the same time, it is necessary to comprehensively take into account the identified relationships between the petrophysical characteristics of production layers. The use of the approach to the analysis of petrophysical characteristics will allow obtaining a more reliable and less subjective hydrodynamic model of the formation.

Prediction and modeling of petrophysical parameters of deep-buried, low permeability glutenite reservoirs in Yubei area, Turpan-Hami Basin, China

The reservoir geological model can provide detailed reservoir characterizations for oil and gas development, thereby addressing the problems of sparse well patterns and lack of data for deep-underground reservoirs in the Yubei area. In this study, stochastic simulations based on geostatistical analyses with seismic attribute constraints were used to predict the physical properties of the Wutonggou Formation reservoirs and establish a fine 3D geological model. Log interpretation models were established to represent the longitudinal distribution of petrophysical parameters. Next, the structural framework of the strata was constructed based on seismic interpretations, and seismic attribute analysis was subsequently performed. Genetic inversion and neural network algorithms were used to obtain acoustic impedance data and predict petrophysical parameters. The planar distribution characteristics of the parameters were then clarified. Finally, petrophysical models were established using Gaussian random function simulation under the control of the facies model, which in turn was simulated via sequential indicator simulation. The model results were evaluated based on the well and production data, and the model parameters exhibited distribution patterns similar to the well data. The model parameters also corresponded well with production data, exhibiting a compliance rate of 90.98%. The model shows that the study area has a large range of reservoir depths and is generally oriented NW-SE. The Wutonggou Formation mainly developed oil-bearing reservoirs of different depositional types at the bottom of the third and first members, and the thickness of the depositions increased significantly with depth. The reservoirs, as a whole, are characterized by medium-low porosity and low permeability. Furthermore, compaction has led to significant reductions in porosity and the formation of microcracks in the glutenite of deep-buried reservoirs, which play important roles in improving reservoir permeability and hydrocarbon flow properties.

Geological Modeling Technology and Application Based on Seismic Interpretation Results under the Background of Artificial Intelligence

The development of seismic technology has made seismic data to be widely used in the interpretation of stratigraphic sequence frames, reservoir identification, fluid detection, and other research fields involved in reservoir description. The 3D technology reservoirs have always been the focus, as well as difficulty, of research. With the rapid development of information technology and the continuous improvement of seismic exploration level, people have put forward higher requirements for the accuracy of seismic data interpretation results. Aiming at the large number of structural and unstructured data in seismic, logging, geology, and other disciplines involved in seismic interpretation, how to effectively organize and coordinate analysis to discover the hidden reservoir structure and oil and gas distribution information has always been a geological and important topic for information processing technicians. This thesis is aimed at the current high-water-phase development of Shengtuo Oilfield reservoir and the problems existing in geological research. Based on seismic structural interpretation and attribute analysis, this paper analyzes the reservoir structural characteristics, sedimentary characteristics, and reservoir physical parameter characteristics based on geology, logging interpretation, core analysis, drilling, and seismic interpretation. Using the kriging method with external drift can cooperate with seismic variables to establish a reservoir geological model to study the Shengtuo Oilfield reservoir. We combine artificial intelligence technology with geological modeling technology of seismic interpretation results to explore the best method for predicting earthquakes. The research results in this paper show that the relative error of the model established by the kriging method in the article is relatively small for thinning wells, mainly concentrated around 1%. Examination of the thinning wells of 45 wells shows that the model established is basically good and the example has high accuracy. The research results in this paper have a guiding study of distribution and tapping potentials in the study area, formulating reasonable development and adjustment plans and improving oil recovery.

Updating a reservoir geological model in order to optimize waterflooding when extracting residual oil reserves from stagnant zones

Background. In the Russian Federation, as well as in many other oil and gas producing countries, waterflooding technology is frequently used as a secondary method of oil production. This technology is aimed, on the one hand, at reservoir pressure maintenance (RPM), and, on the other, at enhancing oil recovery and intensifying oil production. The negative consequences of non-stationary waterflooding can be the premature watering of the produced wells and the imbalance of the reservoir pressure maintenance system, as well as the formation of stagnant and weakly drained zones of the reservoir with residual reserves of hard-to-recover oil.Aim. To improve the efficiency of non-stationary waterflooding under the conditions of high geological and anthropogenic heterogeneity of oil and gas reservoirs in a floating oil reservoir propped up by edge and bottom waters.Materials and methods. We used geological and field information collected on the site of the AB1-2 development object of the Kechimovskoye field in the Western Siberian region. A new methodological approach to optimizing the process of non-stationary waterflooding under complicated conditions of geological and anthropogenic heterogeneity is proposed, including the construction of an improved geological model and the solution of a number of experimental problems using the Hurst method, the Pareto distribution principle and the theory of catastrophes.Results. Using a new version of the geological model of the area of the AB1-2 development object of the Kechimovskoye field and the available geological and field information, we clarified the position of the oil-water contact (OWC) and the correlation of the well section, taking into account the working intervals of production and injection wells. Geological and technical measures were formulated to improve the efficiency of the object under development.Conclusions. An effective development of the geologically complex AB1-2object of the Kechimovskoye field is impossible without updating its geological model. Such updating should be aimed at determining the location of residual reserves in the area and section of the reservoirs, identifying the regularities of the mechanism of oil reserve recovery, assessing the efficiency of the reservoir pressure maintenance system, and developing complex geological-technological measures for achieving the approved value of the final oil recovery factor. The expected efficiency of the proposed optimization methodology provides for additional oil production, a reduction in the flow rate of injected and withdrawal of produced water.

Construction of carbonate reservoir knowledge base and its application in fracture-cavity reservoir geological modeling

To improve the efficiency and accuracy of carbonate reservoir research, a unified reservoir knowledge base linking geological knowledge management with reservoir research is proposed. The reservoir knowledge base serves high-quality analysis, evaluation, description and geological modeling of reservoirs. The knowledge framework is divided into three categories: technical service standard, technical research method and professional knowledge and cases related to geological objects. In order to build a knowledge base, first of all, it is necessary to form a knowledge classification system and knowledge description standards; secondly, to sort out theoretical understandings and various technical methods for different geologic objects and work out a technical service standard package according to the technical standard; thirdly, to collect typical outcrop and reservoir cases, constantly expand the content of the knowledge base through systematic extraction, sorting and saving, and construct professional knowledge about geological objects. Through the use of encyclopedia based collaborative editing architecture, knowledge construction and sharing can be realized. Geological objects and related attribute parameters can be automatically extracted by using natural language processing (NLP) technology, and outcrop data can be collected by using modern fine measurement technology, to enhance the efficiency of knowledge acquisition, extraction and sorting. In this paper, the geological modeling of fracture-cavity reservoir in the Tarim Basin is taken as an example to illustrate the construction of knowledge base of carbonate reservoir and its application in geological modeling of fracture-cavity carbonate reservoir.

Performance Evaluation of Hybrid Steam-Solvent Processes in a Post-CHOPS Reservoir With Consideration of Wormhole Network

Abstract In this paper, techniques have been developed to evaluate performance of steam, solvents, and hybrid steam-solvent processes in a post-CHOPS reservoir with consideration of wormhole network. With the experimentally determined properties of injected gases and reservoir fluids, history matching is accomplished for the reservoir geological model conditioned to the fluid and sand production profiles together with pressure. Meanwhile, the wormhole network is characterized with the pressure gradient-based (PGB) sand failure criterion. Once the history matching is finished, the calibrated reservoir geological model can be used to quantify the contributions of steam, solvents, and hybrid steam-solvent processes under various conditions. The results show that huff-n-puff processes have a very good performance on oil production and recovery when wormhole network is fully generated and propagated. Among all the solvent-based methods, a pure CO2 huff-n-puff process has been proven to be more efficient than flue gas, while the addition of alkane solvents is also beneficial to oil recovery compared with CO2 only method. Since the addition of C3H8 and n-C4H10 will significantly decrease the heavy oil viscosity and enhance the swelling factor, all hybrid steam-solvent injection achieves high oil recovery by taking the advantage of both hot steam and solvents injection.

Efficient Visualization Method and Implementation of Reservoir Model Based on WPF

In view of the slow speed and poor effect of real-time rendering of large-scale reservoir geological grid model, a new grid model hidden algorithm is proposed by analyzing the Eclipse reservoir grid model storage format, grid model representation, and cell sorting rule, which optimizes the original grid data and improves the rendering speed of reservoir grid model. The algorithm in this paper eliminates hidden points and faces according to the topological relationship of the grid, and finally, only the visible point and face data are extracted as the final visual input data. Through the realization of 3D visualization software of reservoir geological model and well trajectory, the correctness and efficiency of the hidden algorithm are verified. In the software, firstly, the number of display grids is effectively reduced by preprocessing, and the 3D graphics technology of WPF and helix is adopted to realize the high-efficiency display of reservoir grids. The comparison test of different scale reservoir models shows that the method can reduce the point and surface data by more than 85% and shows that the speed optimization effect is significant. The 3D display function realizes the interactive functions such as roaming, zooming, and viewpoint switching of the reservoir model, truly reveals again the geological environment and borehole information of underground drilling, which is helpful for drilling interpretation and decision-making, provides a reasonable drilling tracking geological target drilling scheme for the drilling process, and realizes the seamless connection of geological engineering integration.

Fracture system in shale gas reservoir: Prospect of characterization and modeling techniques

The quality and production of shale gas are directly dependent on the development of fractures. Especially in large-scale fracturing development, natural and hydraulic fractures play significant roles. Consequently, there is a growing demand for the quantitative characterization of shale gas reservoir fractures and the development of geological modeling technology. Structured and non-structural fractures make up mainly of natural fractures in shale gas reservoirs. External factors such as tectonic stress control the former, while internal factors such as rock and mineral composition control the latter. Fractures of different scales have a variety of primarykey characterization parameters and prediction techniques. Natural fracture models for shale gas reservoirs are predominant on large-scale and mesoscale fractures. In the numerical simulation, hydraulic fracture modeling is explored in greater detail. This paper discusses the design and explains the main directions of natural and hydraulic fracture modeling in shale gas reservoirs from the aspects of the multi-information application, multi-technology integration, and multi-disciplinary crossing considering the current and potential technology and production requirements. Natural fractures require fusion characterization and modeling on a multi-scale and multi-method basis. Hydraulic fracturing necessarily involves the fusion of multiple information constraints of forwarding and inverse simulation. Furthermore, using the principle of geology-engineering integrated modeling, this paper describes the inner relationship and development of the geological model of a shale gas reservoir from three aspects of model type, data integration, and model fusion to guide the efficient development of shale gas reservoirs.

Real-time updating method of local geological model based on logging while drilling process

The updating of reservoir geological models has become a research hotspot. Nevertheless, two difficulties continue to hinder the development of reservoir geological model updating techniques. First, logging while drilling (LWD) is used mainly to guide geosteering operations and effectively identify the lithology; few scholars have researched the interpretation of reservoir physical characteristics while drilling, which is the basis of updating geological models. Second, interpretation results are difficult to transmit to geological models in real time. Based on the LWD technique, this paper uses logging interpretation, machine learning, computer science, and reservoir geological modeling theories and methods to conduct the research of real-time geological model updating around the well. First, based on effective logging data, two machine learning algorithms which are random forest (RF) and extreme gradient boosting tree (XGBoost) are used to establish interpretation models of the reservoir lithology, porosity, and permeability. The parameters of each model are optimized through cross-validation method, and LWD data are interpreted in real time by interpretation models. Second, based on the convenience of the Ocean secondary development platform and the functionality of Petrel software, a real-time transmission plug-in for the current well trajectory and reservoir interpretation results is compiled, and an automatic updating module for the geological model is established. A case study is performed with data from the Sulige gas field in the Ordos Basin, China. For the real-time interpretation of reservoir characteristics while drilling, after 228 trials, the XGBoost algorithm is chosen to establish reservoir lithology, porosity, and permeability interpretation models. For the real-time updating of the geological model around the well, given the consistent probability distributions and the agreement between adjacent wells, we obtain relative errors between the simulated and real values of the lithofacies, porosity, and permeability of 3.90%, 4.50%, and 7.60%, respectively. Therefore, this paper provides a new method for the real-time modification and updating of reservoir geological models, which preliminarily resolved the contradiction between accuracy and real time of geological model real-time updating.