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Naser Golsanami - One of the best experts on this subject based on the ideXlab platform.
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distinguishing fractures from matrix pores based on the practical application of rock physics inversion and nmr data a case study from an unconventional coal Reservoir in china
Journal of Natural Gas Science and Engineering, 2019Co-Authors: Naser Golsanami, Jianmeng Sun, Ying Liu, Weichao Yan, Chen Lianjun, Lishuai Jiang, Huaimin Dong, Chenglin Zong, Haiqing WangAbstract:Abstract Our main scheme in this study was distinguishing between fracture porosity and matrix porosity in Coalbed Methane Reservoirs through a novel approach which is the joint usage of NMR transverse relaxation (T2) measurements and rock physics modeling based on Levenberg-Marquardt (LM) algorithm. For this purpose, NMR T2 relaxation curves of 34 water-saturated coal samples, prepared and processed in the laboratory, were measured and the pore size distribution inside them was investigated. Subsequently, matrix and fracture porosity were separated based on the threshold T2 relaxation time (90–110 ms) which was achieved through our particularly designed fracturing experiments (this is different from the common T2 cutoff). The T2 measurements were performed in the laboratory using our NMR machine. After that, a rock physics scheme based on Levenberg-Marquardt algorithm was applied to independently estimate matrix porosity and fracture porosity from the samples' statistic mechanical properties including compressional wave velocity (Vp), shear wave velocity (Vs), bulk modulus (K), shear modulus (G), Young's modulus (E), and Poisson's ratio (ν) which were all carefully measured in the laboratory. Afterward, both types of the abovementioned porosities were comprehensively characterized and the obtained achievements were listed. Once finished with this step, the 3D structure of the entire Reservoir was extracted using the recorded data inside 32 drilled wells, and then the established models were upscaled and the unique and independent contour maps of fracture porosity and matrix pore porosity were drawn over the entire Reservoir area. The proposed novel approach provides the kind of information about fractures of the media which is not obtainable with either of NMR or rock physics methods when they are used individually. This study established a novel discussion investigating application of rock physics relationships in order to determine fracture porosity of the coal Reservoirs. The approach was used to successfully investigate and characterize pore-only porosity and fracture-only porosity of a Coalbed Methane Reservoir. According to the obtained results, joint usage of rock physics modeling and LM algorithm would be considered as a reliable technique in quick or deeper exploration of unconventional coal Reservoirs.
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distinguishing fractures from matrix pores based on the practical application of rock physics inversion and nmr data a case study from an unconventional coal Reservoir in china
Journal of Natural Gas Science and Engineering, 2019Co-Authors: Naser Golsanami, Chen Lianjun, Lishuai Jiang, Huaimin Dong, Chenglin Zong, Haiqing WangAbstract:Abstract Our main scheme in this study was distinguishing between fracture porosity and matrix porosity in Coalbed Methane Reservoirs through a novel approach which is the joint usage of NMR transverse relaxation (T2) measurements and rock physics modeling based on Levenberg-Marquardt (LM) algorithm. For this purpose, NMR T2 relaxation curves of 34 water-saturated coal samples, prepared and processed in the laboratory, were measured and the pore size distribution inside them was investigated. Subsequently, matrix and fracture porosity were separated based on the threshold T2 relaxation time (90–110 ms) which was achieved through our particularly designed fracturing experiments (this is different from the common T2 cutoff). The T2 measurements were performed in the laboratory using our NMR machine. After that, a rock physics scheme based on Levenberg-Marquardt algorithm was applied to independently estimate matrix porosity and fracture porosity from the samples' statistic mechanical properties including compressional wave velocity (Vp), shear wave velocity (Vs), bulk modulus (K), shear modulus (G), Young's modulus (E), and Poisson's ratio (ν) which were all carefully measured in the laboratory. Afterward, both types of the abovementioned porosities were comprehensively characterized and the obtained achievements were listed. Once finished with this step, the 3D structure of the entire Reservoir was extracted using the recorded data inside 32 drilled wells, and then the established models were upscaled and the unique and independent contour maps of fracture porosity and matrix pore porosity were drawn over the entire Reservoir area. The proposed novel approach provides the kind of information about fractures of the media which is not obtainable with either of NMR or rock physics methods when they are used individually. This study established a novel discussion investigating application of rock physics relationships in order to determine fracture porosity of the coal Reservoirs. The approach was used to successfully investigate and characterize pore-only porosity and fracture-only porosity of a Coalbed Methane Reservoir. According to the obtained results, joint usage of rock physics modeling and LM algorithm would be considered as a reliable technique in quick or deeper exploration of unconventional coal Reservoirs.
Dameng Liu - One of the best experts on this subject based on the ideXlab platform.
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behavior and mechanism of water imbibition and its influence on gas permeability during hydro fracturing of a Coalbed Methane Reservoir
Journal of Petroleum Science and Engineering, 2021Co-Authors: Yanhai Chang, Dameng Liu, Yanbin Yao, Yong Liu, Chao CuiAbstract:Abstract The migration and interaction of water and gas in coal plays an important role in achieving high-performance recovery of Coalbed Methane (CBM). While a significant amount of fracturing fluid is injected into the Reservoir to enhance the production of CBM, the effect of the imbibed liquid on the gas transport process remains poorly understood. To better understand the impact on well productivity after fracturing fluid invasion, we carried out experimental investigations on dynamic imbibition of water, and resulting matrix permeability changes, using core plug samples of coal from the Qinshui, Ordos and Junggar basins in China. The imbibition process is divided into a quick stage followed by a slow stage: the former occurs in seepage pores with a higher imbibition rate and larger imbibition time-exponent than the latter, which occurs in adsorption pores. Capillary and frictional resistance forces control the spontaneous imbibition of coals. Water movement during gas flooding has a similar imbibition rate and imbibition resistance to the slow stage of spontaneous imbibition, suggesting that the water migration process moves from larger seepage pores to smaller adsorption pores, and this is the main reason for a change in gas permeability. Gas permeability can seemingly be reduced because of two combined mechanisms: 1) occupation of the gas flow path by water in seepage pores; and 2) matrix swelling induced by water adsorption in adsorption pores. In contrast, the changing gas slippage factor can lead to an improvement in gas permeability. Coupling these three factors, we propose a modified permeability model that can be used to evaluate the influence of water on gas permeability and then to estimate the change in gas permeability during hydro-fracturing of a CBM Reservoir.
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petrophysics characteristics of Coalbed Methane Reservoir a comprehensive review
Frontiers in Earth Science, 2021Co-Authors: Qifeng Jia, Dameng Liu, Yidong Cai, Xianglong FangAbstract:Petrophysics of coals directly affects the development of Coalbed Methane (CBM). Based on the analysis of the representative academic works at home and abroad, the recent progress on petrophysics characteristics was reviewed from the aspects of the scale-span pore-fracture structure, permeability, Reservoir heterogeneity, and its controlling factors. The results showed that the characterization of pore-fracture has gone through three stages: qualitative and semiquantitative evaluation of pore-fracture by various techniques, quantitatively refined characterization of pore-fracture by integrating multiple methods including nuclear magnetic resonance analysis, liquid nitrogen, and mercury intrusion, and advanced quantitative characterization methods of pore-fracture by high-precision experimental instruments (focused-ion beam-scanning electron microscopy, small-angle neutron scattering and computed tomography scanner) and testing methods (µ-CT scanning and X-ray diffraction). The effects of acoustic field can promote the diffusion of CBM and generally increase the permeability of coal Reservoirs by more than 10%. For the controlling factors of Reservoir petrophysics, tectonic stress is the most crucial factor in determining permeability, while the heterogeneity of CBM Reservoirs increases with the enhancement of the tectonic deformation and stress field. The study on lithology heterogeneity of deep and high-dip coal measures, the spatial storage-seepage characteristics with deep CBM Reservoirs, and the optimizing production between coal measures should be the leading research directions.
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constraining Coalbed Methane Reservoir petrophysical and mechanical properties through a new coal structure index in the southern qinshui basin northern china implications for hydraulic fracturing
AAPG Bulletin, 2020Co-Authors: Yingjin Wang, Dameng Liu, Yidong Cai, Yanbin Yao, Zhejun PanAbstract:Structurally deformed coal (SDC) influences not only gas outbursts during coal mining but also Coalbed Methane (CBM) production. Different SDCs have different mechanical strengths and physical properties. The structurally constrained petrophysical and mechanical properties of a CBM Reservoir from the southern Qinshui Basin (SQB), northern China, have been investigated by using a coal structure index (CSI). The CSI was established as a quantitative criterion for the deformation of SDCs based on surface conditions and blockiness using the data of 783 coring samples from 109 CBM wells. The results show that undeformed coal and slight brittle SDCs are dominant in the SQB, with ductile SDCs distributed locally. Both compressive strength and tensile strength decline exponentially with increasing CSI average (avg.). Coal structure is a crucial factor for coal seam fracturing; with an increasing CSI (avg.), the major fracture length will first increase to the maximum of 266 m at a CSI (avg.) of 45 and then decrease rapidly. However, branch fractures are independent of the CSI (avg.). The major fracture height attained a minimum of 4.39 m at a CSI (avg.) of 40 and then slowly increased. Therefore, slightly brittle SDCs should be beneficial for fracturing, at least for high-rank coals. The presence of variable SDCs can have a considerable impact on CBM Reservoir petrophysical and mechanical properties. Finally, a CSI model that strives to establish the relation between structure deformation and CBM Reservoir physical and mechanical properties in coal is expected to effectively guide hydraulic fracturing.
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pore fractures of Coalbed Methane Reservoir restricted by coal facies in sangjiang muling coal bearing basins northeast china
Energies, 2020Co-Authors: Dameng Liu, Yidong Cai, Qifeng JiaAbstract:The pore-fractures network plays a key role in Coalbed Methane (CBM) accumulation and production, while the impacts of coal facies on the pore-fractures network performance are still poorly understood. In this work, the research on the pore-fracture occurrence of 38 collected coals from Sangjiang-Muling coal-bearing basins with multiple techniques, including mercury intrusion porosimetry (MIP), micro-organic quantitative analysis, and optic microscopy, and its variation controlling of coal face were studied. The MIP curves of 38 selected coals, indicating pore structures, were subdivided into three typical types, including type I of predominant micropores, type Ⅱ of predominant micropores and macropores with good connectivity, and type Ⅲ of predominant micropores and macropores with poor connectivity. For coal facies, three various coal facies were distinguished, including lake shore coastal wet forest swamp, the upper delta plain wet forest swamp, tidal flat wet forest swamp using Q-cluster analysis and tissue preservation index–gelification index (TPI-GI), and wood index–groundwater influence index (WI-GWI). The results show a positive relationship between tissue preservation index (TPI), wood index (WI), and mesopores (102 nm–103 nm), and a negative relationship between TPI, WI, and macropores/fractures. In addition, groundwater level fluctuations can control the development of type C and D fractures, and the frequency of type C and D fractures show an ascending trend with increasing groundwater index (GWI), which may be caused by the mineral hydration of the coal. Finally, from the perspective of the pore-fractures occurrence in CBM Reservoirs, the wet forest swamp of upper delta plain is considered to be the optimization areas for Sangjiang-Muling coal-bearing basins by a comparative study of various coal facies.
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gas content evaluation of Coalbed Methane Reservoir in the fukang area of southern junggar basin northwest china by multiple geophysical logging methods
Energies, 2018Co-Authors: Dameng Liu, Yidong Cai, Yingjin WangAbstract:To study the gas potential of Coalbed Methane (CBM) in the Fukang area, southern Junggar Basin (SJB) of North China, different methods including multiple geophysical logging, the Kim method with proximate analysis data, and Langmuir adsorption were used to evaluate the gas content. Furthermore, the geological controls on gas content were evaluated. One hundred sixteen CBM wells with geophysical logging and 20 with field-measured gas content were adopted to assess the gas content in the Fukang area of SJB, NW China. The results show that the two geophysical logging variables (DEN and CNL) were favorable for evaluating the gas content due to the perfect correlation with the measured gas content. The gas content varies from 4.22 m3/t to 16.26 m3/t, and generally increases with increasing burial depth. The gas content in coal seams along the synclinal axis is significantly higher than that along the synclinal wing in the west zone. In the east zone, the gas content of the westward is higher than that of the eastward because of the fault coating effect by reverse fault. Generally, the gas content of the SJB is in the order of syncline > surrounding reverse fault > slope of syncline > slope of anticline > central of reverse fault, if only geological structure features are considered. The favorable areas for CBM concentration appear to be a composite gas controlling result of multiple geological factors. Two typical geological scenarios with low gas content and high gas content were revealed. In the Fukang area of SJB, the low gas content is mainly due to the normal fault and roof lithology of sandstone. The most favorable area of high gas content for CBM exploration and development is in the northeast, where reversed fault, synclinal axis, mudstone roof lithology, and burial depth coincide with high gas content.
Harendra Singh - One of the best experts on this subject based on the ideXlab platform.
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Coalbed Methane Reservoir characteristics of coal seams of south karanpura coalfield jharkhand india
International Journal of Coal Geology, 2018Co-Authors: Jaywardhan Kumar, Vinod Atmaram Mendhe, Alka Damodhar Kamble, Mollika Bannerjee, Subhashree Mishra, Bhagwan D Singh, Vivek Mishra, Pradeep K Singh, Harendra SinghAbstract:Abstract Coalbed Methane has emerged as a viable natural gas resource in India since 2007. The understanding of gas genesis kinetics, storage mechanisms and the geological controls is vital for exploration and successful recovery of gas in a cost-effective manner. In this respect, a multidisciplinary analytical approach including gas content, stable isotopes (δ13C1), hydrocarbons distribution, reconstruction of original organic matter, chemical properties, sorption kinetics and the role of petrographic constituents have been assessed. The volatile matter content varies from 20.2 to 32.1 wt%; indicating medium volatile to high volatile bituminous rank of coal with the maximum vitrinite reflectance (VRo%) ranging from 0.63 to 0.98%. The studied coals are vitrinite rich and contains vitrinite group macerals in the range of 41–65 vol%. Dendritic micro-fractures are confined to vitrite microlithotype, and secondary mineralization helps preserve fracture connectivity. The average gas content of coal seams is 2.06 cc/g. The increase in gas content values per 100 m is about 0.38 cc/g emphasizing escape and migration of hydrocarbons during restructuring and tectonic activities in the basin. The relationship of C3/C1 and C2/C1 ratios is indicating that the hydrocarbons in desorbed gas originated from the thermogenic process. The large concentration of Methane in desorbed gas and its stable isotope signatures (δ13C1 The gas content compared with sorption capacity reveals the undersaturation of coal seams. The experimental results summarize that the low gas content is a critical issue. Similarly, the low, quality and quantity of CH4 may affect the exploration and recovery of Methane in the long term into this basin. But, the low values of sorption time (0.12–6.65 days) signifies good diffusion characteristics that may support the recovery of gas. Finally, it is concluded that depth of occurrence, maturity and pore/cleats associated with microconstituents control the gas accumulation and transport in coal seam Reservoirs of South Karanpura coalfield.
Shimin Liu - One of the best experts on this subject based on the ideXlab platform.
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Permeability Evolution of Fractured Sorptive Geomaterials: A Theoretical Study on Coalbed Methane Reservoir
Rock Mechanics and Rock Engineering, 2021Co-Authors: Xiang Zhou, Shimin Liu, Yida ZhangAbstract:Fractured sorptive geomaterials (FSG) are ubiquitous in geological systems such as coal, shale and chalk. The solid matrix of FSG can adsorb species in gas or liquid form, the process of which is often accompanied by the deformation and microstructural alternation of the matrix. Such coupling is further obscured by the presence of fracture network, introducing complex fracture–matrix interactions. Predicting the hydromechanical properties of FSG is of particular importance for the production of Coalbed Methane (CBM) which requires the assessment of coal permeability under varying pressure and stress conditions. This study attempts to investigate the interplay between adsorption, deformation, and permeability evolution of coals. The novel concept of adsorption stress popularized in material science research is adopted here to construct a mechanistic theory describing sorption-induced deformation of coals. The constitutive theory is implemented in a finite element (FE) scheme and then adopted for describing coal matrix in a FE model of coal–fracture system. The model is calibrated for San Juan coals and applied to simulate a typical Methane depletion test. It is observed that, depending on the competing effect between desorption-induced fracture opening and poroelastic compaction, the predicted permeability curve may be monotonically increasing (rising type) or decreasing (decline type), or may exhibit reduction first and then increase (rebound type) during gas depletion. Such competition is found to be controlled by the volume ratio, the permeability ratio, and the stiffness ratio between the matrix and the fracture elements. The prediction covers a wide range of permeability data obtained from laboratory tests and field observations.
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Coalbed Methane Reservoir fracture evaluation through the novel passive microseismic survey and its implications on permeable and gas production
Journal of Natural Gas Science and Engineering, 2020Co-Authors: Lin Tian, Shimin Liu, Yunxing Cao, Bin Shi, Jianzhong Liu, Derek ElsworthAbstract:Abstract Fracture networks in Coalbed Reservoirs serve as the primary gas pathway and thus determine the gas production potential for Coalbed Methane (CBM) recovery. However, the characterization of the fracture network is extremely challenging due to the complexity of both the induced and natural fracture system. A microseismic event analysis can be used to locate the fracturing, and determine the orientation, length, complexity, and temporal growth of the induced fracture by using the focal mechanism. In this study, the fracture system of a coal-bearing formation covering 1.2 km2 in the Luan mining area of China is probed via passive microseismic imaging. Focal mechanisms of individual events are used to characterize the gas production potential for the 10 CBM wells in this area. Fracture reactivation modes are of three types - strike slip, dip slip, and extensional modes – with strike slip the most common followed by dip slip and then extensional type as the least likely. In addition, the location of different types of fractures are different, which indicates the difference of the in-situ stress regime. The 10 CBM wells were hydraulically stimulated in December 2017 then dewatered and allowed to produce for 14 months. We show that the microseismic data have a general positive correlation with gas production with a few exceptions - the higher the event count, the higher the gas production. This result is a best embodiment of the mutual control of Reservoir fractures, stress regime, permeable and gas production in CBM development. We suggest passive microseismic imaging as an effective technique in evaluating the potential for gas production.
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evaluation of gas contents for a multi seam deep Coalbed Methane Reservoir and their geological controls in situ direct method versus indirect method
Fuel, 2020Co-Authors: Shimin Liu, Xiaowei Hou, Yanming Zhu, Yun YangAbstract:Abstract Gas content is one of the most important parameters determining the potential resources and recovery of Coalbed Methane (CBM). Extensive field work has been conducted for a perspective CBM field in Qinshui Basin with multi-targeted producing coal seams. The gas content was estimated by both direct and indirect methods based on the canister desorption results and Methane sorption isotherms. Within the studied CBM field, coal seams are well developed at greater burial depth (>1000 m). The #2, #3, #8, #12, and #15 coal seams in Shanxi and Taiyuan formations are the primary and targeted CBM producing formations. By applying the USBM direct method, the in situ gas contents of the main coal seams are then estimated from the analysis of desorption data. It was found that the indirect method depending on sorption isotherm overestimate the gas content in the studied field because it assumes the gas saturated CBM formation. We found that the coal seams are primarily undersaturated and located under CBM weathered and oxidized zone (CH4 > 90%) with good preservation conditions. The in situ gas contents of the #2, #3, #8, #12, and #15 coals range from 5.62 to 19.36 cm3/g, 11.84 to 31.24 cm3/g, 2.96 to 29.28 cm3/g, 10.96 to 31.19 cm3/g, and 7.91 to 27.32 cm3/g, respectively, with increase trends from the marginal to central areas for all tested seams. Coalification directly determines gas adsorption capacity and it significantly influences the in situ gas content. Coupled contributions of higher gas adsorption capacity and Reservoirs pressure lead to higher gas content occur at depth between 1300 and 1550 m. Moreover, high in situ gas content is always associated with roof lithologies with stronger sealing capacity. However, normal faults and groundwater recharge area could promote gas release from the coals. Thus, the internal area of Block II with poor faults development and weak groundwater runoff is a target area for deep CBM preservation.
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supercritical co2 adsorption quantification and modeling for a deep Coalbed Methane Reservoir in the southern qinshui basin china
ACS omega, 2019Co-Authors: Huihu Liu, Shimin Liu, Shuxun Sang, Tianhe Lan, Bo RenAbstract:Accurate depiction of the adsorption capacity of supercritical CO2 (ScCO2) by existing adsorption models is an important focus for deep coal seams in CO2-enhanced Coalbed Methane (CO2-ECBM) recovery. To investigate the applicability of different adsorption models for the adsorption isotherms of ScCO2, the validities of 10 different adsorption models were analyzed, based on analyses of the adsorption characteristics of ScCO2 from deep coal seams of the Southern Qinshui Basin, China. These models include the Langmuir (L) model, two-parameter Langmuir (TL) model, Toth (T) model, Langmuir-Freundlich (LF) model, extended Langmuir (EL) model, double parameter Brunauer-Emmett Teller model, three-parameter BET (TBET) model, Dubinin-Radushkevich (D-R) model, Dubinin-Astakhov (D-A) model, and Ono-Kondo lattice (OK) model. These models were tested for both the excess and absolute adsorption capacities of ScCO2 under various temperatures and pressures. The simulation accuracy of the different adsorption models was analyzed. The optimal models for the adsorption of ScCO2 in deep coal seams were selected based on a comprehensive analysis of the simulation parameters, standard error, and residual sum of squares. There were obvious differences in the validity of the different adsorption models in terms of the excess adsorption capacity and absolute adsorption capacity of ScCO2. The D-A and D-R models are the optimal adsorption models for the adsorption isotherms of the excess adsorption of ScCO2 for the whole tested pressure range. The T, TL, and D-R models are the optimal adsorption models in simulation of the excess adsorption capacity of ScCO2 for the selected adsorption models when the equilibrium pressure is divided into two sections at the point of 8.13 MPa. In simulation of the absolute adsorption capacity of ScCO2, the TBET and LF models are the optimal adsorption models among the selected models when the equilibrium pressure is less than or equal to 8.13 MPa. The linear, exponential, logarithmic, power function, and polynomial adsorption simulation all have good precision in the simulation of the absolute adsorption capacity of ScCO2 when the pressure is beyond 8.13 MPa.
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Coalbed Methane Reservoir stimulation using guar based fracturing fluid a review
Journal of Natural Gas Science and Engineering, 2019Co-Authors: Qiming Huang, Shimin Liu, Gang Wang, Yongzhi ZhangAbstract:Abstract As a greener and efficient energy source, the development and utilization of Coalbed Methane (CBM) can not only increase the energy supply for the State, but also reduce the greenhouse gas (GHG) emission by replacing other carbon-intense energy sources, such as oil and coal. CBM Reservoirs are known as low to ultra-low permeability Reservoir and thus the fracturing stimulation is commonly required for commercial gas production from coal seams. This article reviews the main components, rheology, friction pressure, and proppant transport characteristics of the guar-based fracturing fluid, and its field applications. Meanwhile, both advantage and disadvantage for CBM fracturing treatment were comprehensively analyzed. Guar-based fracturing fluid is composed of guar gel, and various additives, mainly crosslinker and breaker. As a complex mixture, the effectiveness of guar-based fracturing fluid is not only closely related to the concentration of various chemical additives but also influenced by fluid-coal interactions at the in situ Reservoir conditions. The gel residual due to low flowback rate can potentially damage the formation and hinder the effectiveness of gas production. The formation damages include impacts on gas adsorption, diffusion, and transport in CBM Reservoirs. Coal matrix has a strong adsorption capacity for guar-based fluids and is likely to have a sorption induced matrix swelling and reduce the effective permeability. Hence, it is necessary to develop more efficient breakers to increase flowback of guar-based fracturing fluid. The long-term engineering practice shows that the fracturing effect of guar-based fracturing fluid is quite different in field applications at different operation sites. Therefore, the mechanisms of the impact of guar gel on the Methane flow in coal should be further studied, and it is important to determine the applicability and improving performance of the guar-based fracturing fluid for site specified application based on the Reservoir pressure, temperature, hydrological environment, structural geology and other unique Reservoir properties.
Haiqing Wang - One of the best experts on this subject based on the ideXlab platform.
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distinguishing fractures from matrix pores based on the practical application of rock physics inversion and nmr data a case study from an unconventional coal Reservoir in china
Journal of Natural Gas Science and Engineering, 2019Co-Authors: Naser Golsanami, Jianmeng Sun, Ying Liu, Weichao Yan, Chen Lianjun, Lishuai Jiang, Huaimin Dong, Chenglin Zong, Haiqing WangAbstract:Abstract Our main scheme in this study was distinguishing between fracture porosity and matrix porosity in Coalbed Methane Reservoirs through a novel approach which is the joint usage of NMR transverse relaxation (T2) measurements and rock physics modeling based on Levenberg-Marquardt (LM) algorithm. For this purpose, NMR T2 relaxation curves of 34 water-saturated coal samples, prepared and processed in the laboratory, were measured and the pore size distribution inside them was investigated. Subsequently, matrix and fracture porosity were separated based on the threshold T2 relaxation time (90–110 ms) which was achieved through our particularly designed fracturing experiments (this is different from the common T2 cutoff). The T2 measurements were performed in the laboratory using our NMR machine. After that, a rock physics scheme based on Levenberg-Marquardt algorithm was applied to independently estimate matrix porosity and fracture porosity from the samples' statistic mechanical properties including compressional wave velocity (Vp), shear wave velocity (Vs), bulk modulus (K), shear modulus (G), Young's modulus (E), and Poisson's ratio (ν) which were all carefully measured in the laboratory. Afterward, both types of the abovementioned porosities were comprehensively characterized and the obtained achievements were listed. Once finished with this step, the 3D structure of the entire Reservoir was extracted using the recorded data inside 32 drilled wells, and then the established models were upscaled and the unique and independent contour maps of fracture porosity and matrix pore porosity were drawn over the entire Reservoir area. The proposed novel approach provides the kind of information about fractures of the media which is not obtainable with either of NMR or rock physics methods when they are used individually. This study established a novel discussion investigating application of rock physics relationships in order to determine fracture porosity of the coal Reservoirs. The approach was used to successfully investigate and characterize pore-only porosity and fracture-only porosity of a Coalbed Methane Reservoir. According to the obtained results, joint usage of rock physics modeling and LM algorithm would be considered as a reliable technique in quick or deeper exploration of unconventional coal Reservoirs.
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distinguishing fractures from matrix pores based on the practical application of rock physics inversion and nmr data a case study from an unconventional coal Reservoir in china
Journal of Natural Gas Science and Engineering, 2019Co-Authors: Naser Golsanami, Chen Lianjun, Lishuai Jiang, Huaimin Dong, Chenglin Zong, Haiqing WangAbstract:Abstract Our main scheme in this study was distinguishing between fracture porosity and matrix porosity in Coalbed Methane Reservoirs through a novel approach which is the joint usage of NMR transverse relaxation (T2) measurements and rock physics modeling based on Levenberg-Marquardt (LM) algorithm. For this purpose, NMR T2 relaxation curves of 34 water-saturated coal samples, prepared and processed in the laboratory, were measured and the pore size distribution inside them was investigated. Subsequently, matrix and fracture porosity were separated based on the threshold T2 relaxation time (90–110 ms) which was achieved through our particularly designed fracturing experiments (this is different from the common T2 cutoff). The T2 measurements were performed in the laboratory using our NMR machine. After that, a rock physics scheme based on Levenberg-Marquardt algorithm was applied to independently estimate matrix porosity and fracture porosity from the samples' statistic mechanical properties including compressional wave velocity (Vp), shear wave velocity (Vs), bulk modulus (K), shear modulus (G), Young's modulus (E), and Poisson's ratio (ν) which were all carefully measured in the laboratory. Afterward, both types of the abovementioned porosities were comprehensively characterized and the obtained achievements were listed. Once finished with this step, the 3D structure of the entire Reservoir was extracted using the recorded data inside 32 drilled wells, and then the established models were upscaled and the unique and independent contour maps of fracture porosity and matrix pore porosity were drawn over the entire Reservoir area. The proposed novel approach provides the kind of information about fractures of the media which is not obtainable with either of NMR or rock physics methods when they are used individually. This study established a novel discussion investigating application of rock physics relationships in order to determine fracture porosity of the coal Reservoirs. The approach was used to successfully investigate and characterize pore-only porosity and fracture-only porosity of a Coalbed Methane Reservoir. According to the obtained results, joint usage of rock physics modeling and LM algorithm would be considered as a reliable technique in quick or deeper exploration of unconventional coal Reservoirs.