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Collaborating Authors
Investigation of Fautls Geomechanical Activity and Its Application to Development Program Optimization in Kelasu Gas Field in Tarim Basin
Jiang, Tongwen (Tarim Oilfield Company, Petrochina) | Zhang, Hui (Tarim Oilfield Company, Petrochina) | Wang, Haiying (Tarim Oilfield Company, Petrochina) | Yin, Guoqing (Tarim Oilfield Company, Petrochina) | Yuan, Fang (Tarim Oilfield Company, Petrochina) | Wang, Zhimin (Tarim Oilfield Company, Petrochina)
Abstract The Kelasu gas field located in northern Tarim Basin had experienced four tectonic evolutions, with the most intense deformation between northern margin of the basin and southern Tianshan Mountains. A series of sandstone faulted anticline gas reservoirs were produced after the Himalayan movement. Faults were the main channel to transport natural gas from Jurassic coal-bearing formation to sandstone reservoir in Cretaceous. Simultaneously, the faults play a key role for fluid flow during the development of the gas field, but it is a huge challenge to evaluate the influence of faults on fluid flow quantitatively with depletion. To solve this problem, an integrated research combined geology, geomechanics and gas reservoir engineering was conducted. Firstly, 6 geological factors associated with connectivity and sealing properties of faults was analyzed to determine the critical factors among them. Secondly, based on 4D geomechanical modeling and 3D stress analysis of faults' plane, a calculation model of faults geomechanical activity index (FGAI) was built. Finally, the relationships between faults geomechanical activity and performance of gas field development were investigated to understand the influence of faults' mechanical behavior on production and water invasion during development in Kelasu gas field. It is shown that faults geomechanical activity has profound influence on the performance of Kelasu gas field. ➀The faults geomechanical activity is one of key factors to control permeability, which can indicate the difference of permeability around faults and permeability variation during depletion. ➁With the depletion during exploitation the in-situ stress regime in Kelasu gas field changed from strike slip to normal faulting, and the heterogeneity was also gradually increasing which two resulted in the variety and complicate of faults' geomechanical activity. ➂It is found that there is a good correlation between the faults geomechanical activity and water invasion. The water breakthrough was early and gas-water interface rose fast near the faults with higher geomechanical activity index during depletion. ➃The complex relationship between stress field and faults system resulted in a great difference of faults geomechanical activity index in different location of reservoir. FGAI (Faults geomechanical activity index) is the highest in western reservoir, followed in turn by the eastern, northern, southern, so there is the most rapid uplift of gas-water interface in the western, followed in turn by other parts. Based on evaluation of faults geomechanical activity in this area, this reservoir could be divided into three blocks by different water invasion risk. Areas and gas wells with high risk water invasion were warned in advance. ➅For optimization of well placement, we found that FGAI is relatively low in northwestern reservoir, the fault sealing ability is high, the research provided one of basis for the placement of a new gas well. A fault geomechanical activity index (FGAI) model for the gas reservoir with complex structure and high pore pressure and high in-situ stress was established. And its validity and effectiveness toward development of gas field was proved by production data and information. Based on the quantitative classification and description of faults geomechanical activity to investigate the influence of faults on water invasion, the mechanism of heterogeneous water production was determined in Kelasu gas field. The research provided the sealing evaluation of faults for new wells placement and risk prediction of water breakthrough for gas wells during depletion.
- North America > United States (1.00)
- Asia > China > Xinjiang Uyghur Autonomous Region (1.00)
- Phanerozoic > Cenozoic (0.93)
- Phanerozoic > Mesozoic > Jurassic (0.34)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.89)
- Geophysics > Borehole Geophysics (0.92)
- Geophysics > Seismic Surveying (0.67)
- Asia > Indonesia > Sumatra > South Sumatra > South Sumatra Basin > Palembang Basin > Corridor Block > Suban Field > Talang Akar Formation (0.99)
- Asia > Indonesia > Sumatra > South Sumatra > South Sumatra Basin > Palembang Basin > Corridor Block > Suban Field > Fractured Basement Formation (0.99)
- Asia > Indonesia > Sumatra > South Sumatra > South Sumatra Basin > Palembang Basin > Corridor Block > Suban Field > Durian Mabok Formation (0.99)
- (7 more...)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
Classification and Combination Characteristics of Fractures in Superdeep Tight Sandstone Reservoir with and its Effect on the Control of the Reservoir in Kelasu Structural Belt in Kuqa Depression
Zhou, Lu (PetroChina Tarim Oilfield Company) | Lei, Ganglin (PetroChina Tarim Oilfield Company) | Tang, Yangang (PetroChina Tarim Oilfield Company) | Jin, Xu (PetroChina Research Institute of Petroleum Exploration and Development) | Wang, Zhenhong (PetroChina Tarim Oilfield Company) | Ye, Yu (CNPC USA Corporation) | Jiang, Jun (PetroChina Tarim Oilfield Company) | Zhang, Qi (PetroChina Tarim Oilfield Company)
Structural fractures are widespread with complicated characteristics and distribution, which have large influence on gas production. A lot of effort has been put into the research on the fracture in this area, the research includes refined fracture description on the basis of core and image log data; multi-methods and multi-times fracture distribution pattern prediction. However, the above studies are limited by core availability, seismic data quality, well log data, etc, so the fracture prediction results were not good. Considering the fractures of super-deep tight sandstone reservoirin Kelasu structural belt having the characteristics of multiscale, and the development characteristics, origin and distribution pattern of fractures with different sizes being different, this study defined fracture classes, systematically summarized the development characteristics and distribution patterns of fractures at different scales and their groups, and explored the control effect of fracture system on reservoir. The following understandings are obtained: (1) based on fracture length, aperture, development characteristics, etc, fractures are divided into three classes, namely first order fracture - large fractures, second order fracture - grain penetrating fractures, third order fracture - grain margin fractures; (2) based on fracture length, origin, and combination characteristics, three classes of fracture combinations are recognized, namely first order fracture combination - dominant fracture belt; second order fracture combination - dominant fractures and associated fractures; third order fracture combination - grain margin fracture network; (3) fractures are the main flowing channel in superdeep tight sandstone reservoir, fractures effectively improved reservoir flow property and act as the main contributor of high and stable production in low porosity sandstone reservoir.
- Geophysics > Seismic Surveying (1.00)
- Geophysics > Borehole Geophysics (1.00)
- Asia > China > Xinjiang Uyghur Autonomous Region > Tarim Basin > Keshen Field (0.99)
- Asia > China > Xinjiang Uyghur Autonomous Region > Tarim Basin > Dabei Field (0.99)
- Asia > China > Heilongjiang > Songliao Basin > Daqing Field (0.93)
- 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 > Faults and fracture characterization (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
Decipher Productivity Secret to Optimise Well Stimulation for Keshen Tight Gas Reservoir
Yang, Xiangtong (PetroChina Tarim Oilfield Company) | Xu, Jianhua (Schlumberger) | Zhang, Yang (PetroChina Tarim Oilfield Company) | Wang, Hao (Schlumberger) | Li, Wei (PetroChina Tarim Oilfield Company) | Wang, Lipeng (Schlumberger) | Fan, Wentong (PetroChina Tarim Oilfield Company)
Abstract Keshen Gas Field is part of Kuqa Foreland thrust belt, located in Southern foothill of Tianshan Mountain, northern margin of the Tarim basin, West China. The main pay zone, Cretaceous Bashijiqike (K1bs), has extreme reservoir conditions of ultra-deep (6500-8000 m), high temperature (170-190°C), high pressure (110-120 MPa)(HTHP). Thick salt and gypsum layers with high dip angle above the pay zone also increase safety concerns during drilling and completion. Because of its low porosity (2-7%), low matrix permeability (0.001-0.5 md) and high heterogeneity of nature fractures (NF), well production rates vary largely, ranging from zero to 300,000 m/d. Stimulation has become the only way to enhance single well performance and gain economic production for the long run. Finding controlling factors for well production and effective workflow is the key to realize efficient field development for this tight gas reservoir. In this study, an integrated workflow covering comprehensive reservoir characterization (evaluations of geology, geophysics, geomechanics and reservoir engineering), engineering design and execution (stimulation design and operation) was formulated and conducted to discover main controlling factors which influence production. Firstly, wells were divided in three groups based on their current production rates. Wells in best group have good production in DST tests and higher production after stimulation. Wells in better group have no production in DST tests but obtaining good production after stimulation. Wells in bad group have no production in DST tests, yet very low production after stimulation. Then correlate well production with structure, reservoir property, geomechanics and natural fracture properties to reveal the key controlling factors. Further study was focused on combining multiple parameters to decipher productivity secret based on multi-domain evaluation results. Lastly it was found out that the well performance in this field is controlled by both Stress and NF, i.e. the angle (θ) between NF and the maximum horizontal stress. When θ is small, well productivity is good. Otherwise well productivity is poor. According to this new finding, different stimulation methods were chosen, designed and executed in the field. Through integrated study on different levels, from core analysis to reservoir evaluation, the main factors controlling the tight gas field productivity were deciphered. Together with the understanding of the reservoir, the selection criteria for well stimulation were formulated with the intersection angleθ. After application of study results in stimulation design, gas production shows significant improvement: the average daily production rate increases 50% per well.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.48)
- Geology > Structural Geology > Tectonics > Compressional Tectonics > Fold and Thrust Belt (0.35)
- Geophysics > Seismic Surveying (1.00)
- Geophysics > Borehole Geophysics (0.68)
- Asia > China > Xinjiang Uyghur Autonomous Region > Tarim Basin > Keshen Field (0.99)
- Asia > Thailand > Gulf of Thailand > Western Basin (0.91)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Tight gas (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- (3 more...)
Abstract The Kenshen tight gas field, located on the northern margin of the Tarim basin, western China, has extreme reservoir conditions of an ultra_depth reservoir (6500 to 8000 m) with low porosity (2 to7%), low matrix permeability (0.001 to 0.5 md), high temperature (170 to 190°C), and high pore pressure (110-120 MPa). Those conditions result in high completion costs and a significant difference in individual well production rates; with only one-third of wells drilled meets expectations. Previous studies focused on natural fracture(NF) and attempted to classify reservoir qualities based on the density of NF. Unfortunately, some NFs were closed or cemented by clay or calcite, and it is hard to distinguish open NF from closed NFs using well images in oil-based mud, which is widely used in this tight gas field for reservoir protection. Thereby, no positive correlation between NFs density and productions has been identified, even with the same stimulation treatment. In this study, a comprehensive geological study was conducted to find a new way of characterizing the effectiveness of NF. First, the initial and development stages of NFs were recontructed through a tectonic activity study. Two stages were detected and showed different strikes. Second, petroleum system modeling technology was applied to simulate source rock maturation and gas migration, which revealed that gas generated in the Jurassic source rock migrated to the Cretaceous reservoir formation through faults activated in the same period as the late stage of NFs development. NFs developed earlier were closed or cemented by calcite of later deposition; those at late stage were open and effective for gas charge. Also in this study, Advanced analyses of borehole images indicated an alternative way to delineate NFs developed at different stages using geometry (i.e, crossed NFs shall include those ones developed at later stage). Parallel NFs with its development unidentified can be classified through the intersection angle of fracture strike and maximum stress direction. The smaller the intersection angle is, the easier it is for stimulation and alos the higher for the well production. Based on this study, we have divided reservoirs in the study area into three classes: class 1, reservoir with crossed NFs; class 2, reservoir with fractures of small intersection angle; class 3, reservoir with fractures of large intersection angle. This innovative reservoir classification through NF geometry is currently used in the field to determine formation stimulation method. Class 1 reservoir can benefit from acidizing alone with low completion cost. Class 2 reservoir of should be hydraulically fractured with acid. Class 3 reservoir of should be fractured with sand and proppant sand to achieve economical production. Reservoir classification with NFs geometry had been applied successfully to guide stimulation design in the Keshen tight gas reservoirs. It is a practical and feasible way to choose the most appropriate stimulation treatment method to optimize well performance and avoid restimulation to reduce costs for this extreme type of tight gas field in western China.
- Geology > Structural Geology > Tectonics (1.00)
- Geology > Geological Subdiscipline > Economic Geology > Petroleum Geology (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.71)
- Asia > China > Xinjiang Uyghur Autonomous Region > Tarim Basin > Kuche Basin > Kela Field (0.99)
- Asia > China > Xinjiang Uyghur Autonomous Region > Tarim Basin > Keshen 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)
- (3 more...)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Tight gas (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
Delaying of Bottom-Water-Coning Oriented Hydraulic Fracturing Design and Optimization: Numerical Simulation and Field Case Study
Jv, Liu (CNPC Tarim Oilfield Petroleum China) | Wenjing, Lv (China University of Petroleum) | Hui, Liu (CNPC Tarim Oilfield Petroleum China) | Jianchuan, Li (China University of Petroleum) | Dengfeng, Ren (CNPC Tarim Oilfield Petroleum China) | Qing, Chen (CNPC Tarim Oilfield Petroleum China) | Ben, Li (China University of Petroleum) | Hui, Li (China University of Petroleum) | Yinglin, Hong (CNPC Tarim Oilfield Petroleum China) | Sanfeng, Xu (CNPC Tarim Oilfield Petroleum China)
ABSTRACT Is usually used hydraulic fracturing to enhance the productivity of tight gas sandstone formations. If basal water layers were connected to the upper gas formation via hydraulic fractures, the gas productivity of the stimulated wells would be reduced drastically. It is crucial to postpone the bottom-water-coning effect by meticulous hydraulic fracturing design and operation parameters optimization. Temporary plugging could be a potential solution for controlling hydraulic fracture extension in the vertical direction. This paper proposed a basal water-avoiding hydraulic fracturing design and optimization methodology and procedures to solve this problem. The geological and geo-mechanical models were built based on the characteristics of the gas layer, natural fracture, and basal water layer analysis. Hydraulic fracture propagation simulation conducted pump rate, Hydraulic fracture propagation simulation considered pump rate, frac-fluid volume, frac-fluid viscosity, temporary plugging material volume, proppant concentration, and proppant volume. Hydraulic fracture vertical height and distance to the basal water layer were used as the primary indicators to optimize the frac-fluid volume, pump rate, and temporary plugging material volume. Then simulated fracture area and fracture propped area were used as significant parameters to identify the optimal frac-fluid viscosity, proppant concentration, and proppant volume. KS field is an ultra-deep tight gas sandstone formation with basal aquafers. The fracture propagation model of the KS-X well was established to delay bottom-water-coning-oriented hydraulic fracturing design and optimization. Results showed that the optimal frac-fluid volume, pump displacement, and temporary plugging material quality are 950 m, 4.5 m/min, and 300 kg, respectively. The optimal proppant volumes of 70/140 mesh, 40/70 mesh, and 30/50 mesh ceramic proppant are 6 m, 38 m, and 9 m, respectively. After hydraulic fracturing, the gas production rate of the KS-X well is as high as 290,000 m/day without any water production for one month, indicating the effectiveness of the proposed basal water-avoiding hydraulic fracturing design and optimization methodology. The proposed design and optimization procedures can be further used in other basal aquifer gas fields.
- Asia > China > Sichuan Province (0.28)
- Asia > China > Xinjiang Uyghur Autonomous Region (0.28)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Asia > China > Xinjiang Uyghur Autonomous Region > Tarim Basin > Tazhong Field (0.99)
- Asia > China > Xinjiang Uyghur Autonomous Region > Tarim Basin > Tahe Field (0.99)
- Asia > China > Sichuan > Sichuan Basin > Moxi Block > Longwangmiao Formation (0.99)
- North America > United States > Louisiana > China Field (0.97)