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Collaborating Authors
Naturally-fractured reservoirs
First Application of LWD High-Resolution Ultrasonic Imaging in an Unconventional Horizontal Well in the Najmah Formation: Case Study from Kuwait
Al-Naqeeb, Mohamed Nizar (Kuwait Oil Company) | Ghneej, Ali Faleh Abu (Kuwait Oil Company) | Al-Khabbaz, Mohammed (Kuwait Oil Company) | Abdulkarim, Anar (Halliburton)
Abstract The unconventional Jurassic Najmah carbonate-shale formation in northern Kuwait has been tested and found to be a prolific source rock as well as a producer of gas, condensate, and light oil in different wells. The flow-controlling system, given the very low porosity, is highly dependent on the presence of a natural fracture network. The Najmah kerogen member, formally known as the Najmah shale, is the source reservoir composed of highly organic-rich argillaceous and calcareous clay, represented by very high total gamma ray values associated with high uranium on spectral gamma ray logs. Average matrix porosity ranges from 2 to 6%, low permeability from 0.01 to 1.5 mD, and total organic content (TOC) from 7 to 12%. Identification and interpretation of fractures, bed boundaries, and borehole breakout from high-resolution images plays a crucial role in optimizing completion design. Using wireline has been a challenge in horizontal wells, making logging-while-drilling (LWD) acquisition preferable. The case study is from a horizontal exploration well drilled with a rotary steerable system combined with gamma ray and resistivity sensors in the Najmah formation of north Kuwait, where a multi-stage fracking completion was planned. The logging program also included density, neutron porosity, sonic, and high-resolution ultrasonic borehole imaging measurements. To minimize the risk of stuck events, it was decided to use LWD acquisition. Wells in the area are typically drilled in the minimum stress direction (SHmin) to cross natural fractures perpendicularly, to optimize fracking. However, surprisingly, most of the natural fractures were almost parallel to SHmin. Overall, high data quality was achieved, and the results exceeded the end data users’ expectations. In total 96 natural fractures, 16 bed boundaries, and a few breakout intervals were interpreted within a measured-depth interval of 1,610 feet. Some of the fractures could be identified with high confidence on a 1:200 scale log. The new information about fracture orientation will be considered for future well design planning. The results were also used to facilitate the optimization of future field development and completion design. Further field analysis and studies are planned to be performed to confirm the interpreted results.
- Asia > Middle East > Kuwait (1.00)
- Asia > Middle East > UAE > Abu Dhabi Emirate > Abu Dhabi (0.15)
- Geology > Geological Subdiscipline (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.74)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Borehole Seismic Surveying (0.35)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > Abdalli Field (0.99)
- Asia > Middle East > Kuwait > Ahmadi Governorate > Arabian Basin > Widyan Basin > Tayarat Formation (0.99)
- Asia > Middle East > Kuwait > Ahmadi Governorate > Arabian Basin > Widyan Basin > Greater Burgan Field > Wara Formation (0.99)
- (8 more...)
- Well Drilling > Drilling Operations > Directional drilling (1.00)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- (2 more...)
Lower Completions Design and Execution in the Complex ERD Well on Tengiz Oil Field
Rakhmetov, Z. (TCO Drilling Engineer) | Ismukhambetov, A. (TCO Operation Engineering Team Lead) | Sissenov, O. (K&M Sr Drilling Engineer) | Click, C. (TCO Operation Engineering Team Lead) | Morrison, A. (TCO Early Concept Team Lead) | Takhanov, D. (TCO Drilling Design Team Lead) | Simancas, R. Gomez (TCO Completions Advisor) | Gabdulov, T. (TCO Drilling Operations Engineer) | Kabiyev, K. (TCO Drilling Operations Engineer)
Abstract This paper presents a case study of designing a lower completion deployment concept consisting of conformance control liner with up to 25 compartments (packers and sliding sleeves). The horizontal well was planned with the longest lateral section of up to 2,500m in an out-board area of Tengiz field. The reservoir in this area is known to have a modest carbonate matrix reservoir, relatively poorly connected with presence of scattered natural fractures networks. To maximize number of natural fracture intersections and contact with reservoir matrix, Tengizchevroil (TCO) planned to drill a horizontal well with long lateral section, followed by frac and/or matrix stimulation to improve production by connecting to the natural fracture network. One of the main challenges of the well design was the ability to successfully deploy a lower completion to the well total depth (TD). Extended length of the lateral section causes drag accumulation along the string during the run which could lead to inability to run the liner to the desired depth. Generation of excessive compressional loads which could result in liner string buckling and ultimately to lock up was expected at open hole friction factors more than 0.45. Based on friction factors calibration from the other Tengiz offset wells with similar well trajectories which revealed 0.35–0.45 OH FF along with the absence of experience in running long completions strings with up to 25 compartments and lack of good understanding of OH FF in naturally fractured horizontal well, the decision was made to deliberately plan for 0.60 OH FF as design friction factor to establish feasibility. Installation of the liner in this well at higher OH FF required consideration of advanced methods such as a) liner flotation, b) liner rotation, c) running a casing swivel. The detailed analysis of each of the methods revealed that introduction of liner rotation would not only solve the liner running issue on this well with long lateral section but may also allow completion of more extended lateral sections beyond 2,500m.
- Asia > Kazakhstan > Mangystau Oblast > Precaspian Basin > Tengiz Field > Tengiz Formation (0.99)
- Asia > Kazakhstan > Mangystau Oblast > Precaspian Basin > Tengiz Field > Korolev Formation (0.99)
- Well Drilling > Drilling Operations > Directional drilling (1.00)
- Well Completion > Completion Selection and Design (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
Abstract The success of production from unconventionals in North America, encourage Kuwait to focus on Najmah Kerogen and unconventional resources that have value of significant hydrocarbon resource potential in North Kuwait Jurassic Area. Kuwait Oil Company has embarked on a journey to unlock these unconventional resources by screening the subsurface targets in the reservoirs which have potential to contribute to the gas production ambitions of the country. Unconventional field development team has evaluated these difficult reservoirs through an End To End (E2E) hydrocarbon maturation (HCM) framework, with a clear roadmap to appraise and develop these resources to sustain the required plateau of the unique Gas Asset in Kuwait. The reservoirs of focus are a mix of naturally fractured carbonates with conventional "Middle Marat (MM)" reservoirs and tight unconventional reservoirs ("Najmah/Sargelu"&"Kerogen") at a depth of 15000+ ft in a HPHT setting. The E2E-HCM Modules have been used as key building blocks for the economic evaluations. The modules can be flexibly combined as needed to model the economic potential of each of the Common Value Areas (CVAs), where a CVA is defined as an area that has been demonstrated to have common economic metrics based on Play-Based Exploration (PBE), infrastructure, and field development characteristics. Aggregating modelling tools (eg Proviso), using decline curves of 23 conventional volatile oil and gas condensate reservoirs (3D simulation) and five unconventional reservoirs have been used. Long term production forecast is generated by combining these simulation results and flowing through 8 production facilities. An optimized drilling sequence of 500+ wells is worked-out to achieve this production forecast. This exercise also facilitated in screening potential targets for further drilling for meeting and sustaining the promised gas production plateau. In this paper, the methodology and workflow used for unlocking the potential of conventional and unconventional resources of north Kuwait Jurassic reservoirs is highlighted.
- Geology > Rock Type > Sedimentary Rock (0.97)
- Geology > Geological Subdiscipline (0.68)
- Geology > Structural Geology > Tectonics > Compressional Tectonics > Fold and Thrust Belt (0.46)
- Asia > Azerbaijan > Caspian Sea > Apsheron-Pribalkhan Ridge > South Caspian Basin > Azeri-Chirag-Guneshli Field > Azeri Field (0.99)
- Africa > Nigeria > Gulf of Guinea > Niger Delta > Niger Delta Basin > OML 118 > Bonga Field (0.99)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Upper Marrat Formation (0.98)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Sargelu Formation (0.98)
- Well Drilling > Drilling Operations > Directional drilling (1.00)
- Well Completion > Hydraulic Fracturing > Multistage fracturing (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- (5 more...)
Data and Model Base of Customized Hydraulic Fracturing for Continental Shale Oil
Mei, Qiliang (PetroChina Changqing Oil Company) | Ma, Fujian (SLB, China) | Lei, Qihong (PetroChina Changqing Oil Company) | He, Youan (PetroChina Changqing Oil Company) | Luo, Yin (SLB, China) | Wang, Bo (PetroChina Changqing Oil Company) | Niu, Li (SLB, China) | Liu, Yuan (SLB, China)
Abstract The challenges of lacustrine shale oil reservoirs include not only subsurface heterogeneity of reservoir quality and but also the effect of natural fractures on propagation of hydraulic fractures and associated fracture hits. The intercalated sandstone and shale in a gravity deposit setting result in significant variation in the reservoir quality. Meanwhile, the subsurface conditions become even more complicated when the reservoirs are naturally fractured. The objective of this study is to characterize reservoir quality, natural fractures, and completion quality with well, seismic, and fracturing data, eventually to provide a base for a customized fracturing job according to the local geology aiming to enhance reservoir recovery. A geological model and a geomechanical model were built integrating all available data, including logs, core data, and seismic data, and an ant-tracking algorithm was used with variance of the seismic data as the input to delineate natural fractures. The quality check was performed by comparing drilling data, microseismic data, and fracturing data. A distributed fracture network (DFN) model was built with the ant-tracking results. Fracture stability analysis was performed when the natural fracture model and geomechanical model were ready. The fracturing design was customized and optimized with the models mentioned above and understanding obtained from the analyses. Different fracturing strategies were applied to each stage and to each well of the same pad based on the geoscience models. Some wells were completed with large-volume and high-rate fracturing practice to maintain the long-term reservoir pressure. Alternatively, some wells were subject to an intensive staging with low-volume and low-rate fracturing practice to create better near-wellbore flowing conditions. The combination of customized fracturing design and real-time adjustments during execution was approved to be a valid and practical geoengineering approach. The benefit of the workflow includes not only high fracturing efficiency, but also the effects on production performance. Production data measured by multiphase flow metering showed that the customized approach results in a 20% production increase.
- North America > United States > Texas > Dawson County (0.24)
- Asia > China > Shaanxi Province (0.17)
- Asia > Middle East > UAE > Abu Dhabi Emirate > Abu Dhabi (0.15)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.84)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.67)
- Asia > China > Shanxi > Ordos Basin (0.99)
- Asia > China > Shaanxi > Ordos Basin (0.99)
- Asia > China > Inner Mongolia > Ordos Basin > Sulige Field > Ordos Formation (0.99)
- (3 more...)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- (2 more...)
Abstract Microseismic monitoring is a commonly used technique in characterizing hydraulic fractures. However, fracture network reconstruction remains challenging due to the heterogeneity and complex stress field of shale gas reservoirs. An Energy-based 3D Fracture Reconstruction method (EFR3D) is proposed to derive the complex fracture network from microseismic data in a shale gas reservoir. The EFR3D method mainly combines the Propose Expand and Re-Estimate Labels algorithm (PEARL), the Density-Based Spatial Clustering of Applications with Noise algorithm (DBSCAN), and the Alpha-shape algorithm to detect the fracture orientation and fracture shape. This method formulates fracture orientation detection as an energy minimization task to improve reconstruction accuracy. The effectiveness of the proposed method was evaluated by performing a verification procedure against different fracture numbers, fracture orientations, and fracture scales using the Monte Carlo simulation. The results show that the proposed method has good adaptability and high accuracy in various fracture configurations. Furthermore, a field application of six horizontal wells located in the southern Sichuan basin, southwest China, was conducted to illustrate the robustness and practicability of the proposed method. The proposed method can serve as a practical and reliable approach to characterize hydraulic fractures.
- Asia > China (1.00)
- North America > United States > Texas (0.69)
- Geology > Geological Subdiscipline > Geomechanics (0.89)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.82)
- North America > United States > Texas > Fort Worth Basin > Barnett Shale Formation (0.99)
- Asia > China > Sichuan > Sichuan Basin > Southwest Field > Longwangmiao Formation (0.99)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Shale gas (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
Understanding Compressibility Coefficients in Heterogeneous Fractured Rocks and Implications for CSG Reservoir Simulation
Santiago, V. (UQ Centre for Natural Gas, The University of Queensland, Brisbane, Australia) | Rodger, I. (UQ Centre for Natural Gas, The University of Queensland, Brisbane, Australia) | Hayes, P. (UQ Centre for Natural Gas, The University of Queensland, Brisbane, Australia) | Leonardi, C. (School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, Australia) | Deisman, N. (Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Canada)
Abstract A variety of different compressibility terms, including cleat compressibility and bulk compressibility, are used when modelling coal seam gas (CSG) reservoirs. The relationship between different compressibility terms is often theoretically straightforward, but in practice may be much more complex, particularly when considering heterogeneous and/or fractured rocks. This paper outlines experimental work measuring different compressibility terms using printed rock samples, and analysis that demonstrates some of the challenges associated with relating these compressibilities. Three-dimensional printed rock samples with heterogeneity (layers of different stiffness), some of which included planar fractures, were created. The compressibility of these samples was measured based on changes in permeability (as might be used to estimate cleat/fracture compressibility) and also based on volumetric strain. Simple models were history matched to estimate the cleat compressibility, which is then used to calculate a bulk compressibility based on theoretical relationships. This is then compared to the bulk compressibility measurement based on volumetric strain. Initial results indicate that the relationship between the different compressibility terms is much more complex than theory suggests. The theoretical relationship of bulk compressibility with pore compressibility yields values up to one order of magnitude different from that of laboratory measurements. Our study highlights the importance of cleat compressibility in modelling CSG reservoirs and the significance of bulk compressibility in estimating deformation associated with CSG production. We believe our findings will contribute to a better understanding of compressibility terms in CSG reservoir modelling and encourage further research in this area.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (0.34)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Coal seam gas (1.00)
- Reservoir Description and Dynamics > Reservoir Simulation (1.00)
- (2 more...)
Mehdi Matt Honarpour is the CEO and President of the Honarpour Technology Company, HTC, LLC. He currently provides consulting and integrated training for Energy companies. Previously, he was the Principal Reservoir Engineer at BHP, the Global Reservoir Engineering Advisor at Hess Corporation, and a Senior Reservoir Engineering Advisor at ExxonMobil. He has an extensive experience in reservoir characterization and reservoir engineering and their impact on reservoir system performance. He has contributed extensively to the science and practice of rock-fluid characterization, integration of core analysis data, wireline log and well test data for conventional sandstone, naturally fractured carbonates and Unconventional reservoirs.
- Energy > Oil & Gas > Upstream (1.00)
- Education > Educational Technology > Educational Software > Computer Based Training (0.85)
- Reservoir Description and Dynamics > Reservoir Characterization (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (0.61)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Carbonate reservoirs (0.61)
- (2 more...)
Modeling Transient Flow Behavior of Off-Center Fractured Well with Multiple Fractures in Radial Composite Gas Reservoirs
Xu, Youjie (Chongqing University of Science and Technology (Corresponding author)) | Zuping, Xiang (Chongqing University of Science and Technology) | Yu, Mengnan (School of Petroleum Engineering, Chongqing University of Science and Technology)
Summary Vertical hydraulic fracturing is widely used to develop low-permeability gas reservoirs. Uneven distribution of formation permeability and stress leads to multiple-wing hydraulic fractures with different lengths, which results in the wellbore not being the center of the circular stimulated reservoir volume (SRV) region. Therefore, to simulate the wellbore pressure of this phenomenon, a semianalytical model of the off-center multiwing fractured well in radial composite gas reservoirs is presented and the corresponding solution method is shown. The model is verified with the numerical solution, and eight flow regimes can be distinguished under the ideal case, which includes bilinear flow, fracture interference, linear flow, radial flow of inner region, transition flow of inner region, and radial flow of inner region. Compared with the previous model in which the well is at the center of radial composite gas reservoirs, in this paper we present an obvious “step” after the inner region radial flow regime, which is related to the off-center distance and radius of the inner region. In addition, the effects of some important parameters (such as off-center distance, permeability mobility, inner region radius, and fracture distribution) on typical curves are discussed. Finally, field well testing data are used to verify the accuracy of the model.
- North America > United States > Oklahoma > Anadarko Basin > M Formation (0.99)
- Asia > China > Shanxi > Ordos Basin (0.99)
- Asia > China > Shaanxi > Ordos Basin (0.99)
- (2 more...)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- (3 more...)
Summary This paper examines the buildup (BU) pressure response of a vertical well that penetrates an unconventional tight naturally fractured carbonate reservoir in Mexico. Four BUs in the same well over a period of 4 months, with intermediate flow periods, suggest partial closure of natural fractures. Radial flow is dominant in the four BUs. This is recognized in semilogarithmic and pressure derivative crossplots. However, the formulations require a consistent empirical component to match the BU data. The four BU tests are evaluated with a semi-empirical dual porosity model with restricted interporosity flow. The restricted flow between matrix and fractures is the result of partial secondary mineralization (cementation) within the fractures, which can be visualized as a natural positive skin that reduces the oil flow from the matrix to the fractures. The empirical part of the method is provided by a severity exponent (SE), which helps improve the match between the BU semilog and derivative plots. The BU evaluations permit estimating several parameters of interest, including fracture capacity (k2·h), skin, storativity ratio (ω), and the extrapolated pressure (p*). Results suggest that although natural fractures are present, they tend to close once the well goes on production. Thus, the conclusion is reached that the carbonate reservoir is tight and likely stress dependent. The calculated skin goes from an improved condition around the wellbore to slightly damaged conditions, probably due to fracture closure. The value of ω increases continuously, suggesting a tendency of the reservoir to move from dual to single porosity behavior. The reservoir is overpressured (0.87 psi/ft) and the extrapolated pressures (p*) decrease because of the tight characteristics of the reservoir. However, given the large size of the reservoir, the likelihood of depletion is low. The novelty of this study is the development of a new easy-to-use semi-empirical well testing model for matching the BU pressure response of four tests performed in a well that penetrates an overpressured, unconventional, tight, naturally fractured carbonate reservoir. The tests could not be matched with conventional methods currently available in the literature.
- North America > Mexico (1.00)
- North America > Canada > Alberta (0.46)
- North America > United States > Texas (0.28)
- Geology > Petroleum Play Type > Unconventional Play > Fractured Carbonate Reservoir Play (0.80)
- Geology > Rock Type > Sedimentary Rock (0.67)
- North America > Canada > Saskatchewan > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- North America > Canada > Northwest Territories > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- North America > Canada > Manitoba > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- (4 more...)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Carbonate reservoirs (1.00)
Summary The significant quantities of oil contained in fractured karst reservoirs in Brazilian presalt fields add new challenges to the development of upscaling procedures to reduce time on numerical simulations. This work aims to represent multiscale heterogeneities in reservoir simulators based on special connections between matrix, karst, and fracture mediums, both modeled in different grid domains within a single porosity flow model. The objective of this representation is to strike a good balance between accuracy and simulation time. Therefore, this work extends the approach of special connections developed by Correia et al. (2019) to integrate both karst and fracture mediums modeled in different grid domains and block scales. The transmissibility calculation between the three domains is a combination of the conventional formulation based on two-point flux approximation schemes and the matrix-fracture fluid transfer formulation. The flow inside each domain is governed by Darcy’s equation and implicitly solved by the simulator. For proper validation and numerical verification, we applied the methodology to a simple case (two-phase and three-phase flow) and a real case (two-phase flow). For the simple case, the reference model is a refined grid model with (1) an arrangement of large conduits (karsts), which are poorly connected; (2) a well-connected and orthogonal system of fractures; and (3) a background medium (matrix). The real case is a section of a Brazilian presalt field, characterized as a naturally fractured carbonate reservoir. The reference is the geological model. The simulation model consists of a structural model with different gridblock sizes according to the scale of the heterogeneities—small-scale karst geometries, medium-scale matrix properties, and larger-scale fracture features—interconnected by special connections. The results for both cases show a significant performance improvement regarding a dynamic matching response with the reference model, within a suitable simulation time and maintaining the dynamic resolution according to the representative elementary volume of heterogeneities, without using an unstructured grid. In comparison to the reference model, for the simple case and the real case, the simulation time was reduced by 42% and 87%, respectively. The proposed method contributes to a multiscale flow simulation solution to manage heterogeneous geological scenarios using structured grids while preserving the high resolution of small-scale heterogeneities and providing a good relationship between accuracy and simulation time.
- Europe (1.00)
- North America > United States (0.93)
- South America > Brazil (0.69)
- Geology > Rock Type > Sedimentary Rock (1.00)
- Geology > Structural Geology > Tectonics > Salt Tectonics (0.55)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Carbonate reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Simulation (1.00)
- (2 more...)