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01 August 2024, Volume 45 Issue 4 Previous Issue    Next Issue

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OIL AND GAS EXPLORATION

Research Progress and Trend of Ultra-Deep Strike-Slip Fault-Controlled Hydrocarbon Reservoirs in Tarim Basin WANG Qinghua, CAI Zhenzhong, ZHANG Yintao, WU Guanghui, XIE Zhou, WAN Xiaoguo, TANG Hao 2024, 45 (4):  379-386.  doi: 10.7657/XJPG20240401 Abstract ( 385 )   HTML ( 33 )   PDF (4805KB) ( 500 )   Save Ultra-deep strike-slip fault-controlled hydrocarbon reservoirs have been discovered as a new frontier for exploration and development in the Tarim basin. However, the complexity of these reservoirs poses a significant challenge for profitable development, necessitating enhanced foundational geological research. The strike-slip fault-controlled hydrocarbon reservoirs are commonly characterized by strong heterogeneity, intricate reservoir and fluid distribution, significant variations in hydrocarbon production, and low recovery. The great differences in faulting, reservoir characteristics, hydrocarbon accumulation, and fluid dynamics of these reservoirs between different areas present a series of exploration and development challenges. A series of models for strike-slip fault zones of different genesis and their controls on reservoirs have been established, and the mechanisms of reservoir formation along strike-slip fault zones including combined reservoir control by microfacies, strike-slip fault and dissolution, and contiguous, differential and extensive development have been revealed. Furthermore, the strike-slip fault-controlled reservoir models with “source-fault-reservoir-caprock coupling” and “small reservoir but large field” are constructed, unveiling the mechanisms of the hydrocarbon accumulation and preservation of ultra-deep strike-slip fault-controlled reservoirs. This research breaks through the limitations in theory that weak strike-slip faults in cratonic basins are difficult to form large-scale strike-slip fault-controlled reservoirs and large oil/gas fields. Finally, the genesis of large-scale strike-slip fault systems, the differential reservoir formation mechanisms within strike-slip fault zones, and the hydrocarbon enrichment patterns in cratonic basins have been clarified. Figures and Tables | References | Related Articles | Metrics

Multilayer Superimposition Patterns of Strike-Slip Fault Zones and Their Petroleum Geological Significance in Platform Area, Tarim Basin YANG Haijun, NENG Yuan, SHAO Longfei, XIE Zhou, KANG Pengfei, YUAN Jingyi, FU Yonghong 2024, 45 (4):  387-400.  doi: 10.7657/XJPG20240402 Abstract ( 210 )   HTML ( 16 )   PDF (33226KB) ( 233 )   Save In recent years, with the progress of oil and gas exploration in the Tarim basin, large-scale strike-slip fault systems have been discovered in the Paleozoic strata of the platform area in the basin and a new type of fault-karst reservoir has been identified. Due to multiple tectonic movements in the basin, these strike-slip faults exhibit multilayer structures featured with multiple phase superimposition. Based on high-quality 3D seismic data, drilling data, and petroleum geological data, the multilayer superimposition of large-scale strike-slip faults in the basin and its controls over hydrocarbon accumulation were investigated. The research results show that the strike-slip fault zones in the platform area of the Tarim basin primarily develop five structural layers in the Paleozoic: Lower Cambrian pre-salt structural layer, Middle Cambrian salt structural layer, Upper Cambrian-Middle Ordovician carbonate structural layer, Upper Ordovician-Carboniferous clastic structural layer, and Permian magmatite structural layer. Affected by multiple tectonic movements and strike-slip fault activities, these layers exhibit characteristics of banded spatial distribution, vertical superposition, and differential superimposition. The superimposition patterns can be broadly categorized into four types: connection, overlapping, inverse superimposition, and inverse reformation. These superimposition patterns have significant impacts on hydrocarbon accumulation, and three types of reservoirs such as TypeⅠ (Ordovician carbonate reservoirs), Type Ⅱ (Ordovician carbonate, Silurian clastic, and Permian magmatite reservoirs), and Type Ⅲ (Cambrian pre-salt dolomite reservoirs) are formed. Figures and Tables | References | Related Articles | Metrics

Ordovician Differential Deformation Mechanism of Northern Section of FⅠ17 Strike-Slip Fault, Tarim Basin CAI Zhenzhong, LI Bing, LUO Xiao, LI Huiyuan, LI Mengqin, LI Zhengyang, WANG Qinghong 2024, 45 (4):  401-408.  doi: 10.7657/XJPG20240403 Abstract ( 177 )   HTML ( 12 )   PDF (7545KB) ( 140 )   Save To understand the role of strike-slip faults in hydrocarbon accumulation in carbonate reservoirs, based on 3D seismic data, the development characteristics and tectonic deformation processes of the northern section of the FⅠ17 strike-slip fault in the Tarim basin were analyzed, and a sandbox physical simulation was performed on the formation and evolution of strike-slip faults by using geological modeling. The FⅠ17 strike-slip fault is divided into two sections. The southern section, nearly NE-SW trending, is characterized by en echelon faults, with the Yijianfang formation showing a uplifting feature and significant vertical deformation during the Ordovician period. The northern section, nearly NNE-SSW trending, is dominated by linear strike-slip faults, with the Yijianfang formation exhibiting weak deformation and slight subsidence in local areas during the Ordovician period. Sandbox physical simulation results show that a series of uplift zones formed along the main displacement zone of linear strike-slip faults, while the deflected strike-slip faults formed a series of uplift zones in the southern section and presented strata subsidence in the northern section. Under identical stress conditions, differences in the initial strikes of strike-slip faults lead to the changes in the stress put on the faults, thereby influencing their evolution processes. The southern section of the FⅠ17 strike-slip fault is found with more concentrated stress in compressional uplift zone and more developed fractures and vugs locally, containing richer hydrocarbons. The southern section is expected to be superior in exploration to the northern section. Figures and Tables | References | Related Articles | Metrics

Segmented Structural Characteristics and Growth Mechanism of Transtensional Strike-Slip Fault Zone in Tazhong Uplift BAI Bingchen, WU Guanghui, MA Bingshan, ZHAO Xingxing, TANG Hao, SHEN Chunguang, WANG Xupeng 2024, 45 (4):  409-416.  doi: 10.7657/XJPG20240404 Abstract ( 212 )   HTML ( 9 )   PDF (5426KB) ( 267 )   Save In the Tarim basin, transpressional strike-slip faults are developed under oblique compression in the Ordovician carbonate rocks, but a series of transtensional strike-slip faults have been discovered in the Tazhong uplift, significantly controlling the hydrocarbon accumulation. Using the 3D seismic data from the western Tazhong uplift, as well as the attributes such as coherence and curvature, the kinematic parameters of the strike-slip faults were statistically analyzed. Through structural analysis of the strike-slip faults, the FⅡ21 strike-slip fault zone in the Tazhong uplift was optimally selected for segmented modeling, and its growth mechanism was investigated. The results show that the FⅡ21 strike-slip fault zone is segmented horizontally and stratified vertically. Various structural forms such as linear, en echelon, horsetail, wingtip, braided, and overlapping structures are found at the top of the Ordovician carbonates. The characteristics of altitude differences of the fault zone reveal segmentation and tail-end expansion as the growth mechanisms, elucidating its role as a transform fault that regulates the reverse contraction deformation on either side of the strike-slip fault zone, and clarifying its evolution process including stages of en echelon fracturing, growth and linkage, and reactivation. Figures and Tables | References | Related Articles | Metrics

Segmentation of Strike-Slip Faults and Its Controls on Hydrocarbon Accumulation in Tarim Basin: A Case Study of FⅠ17 Strike-Slip Fault Zone XIONG Chang, SHEN Chunguang, ZHAO Xingxing, ZHAO Longfei, LI Shengqian, ZHOU Jie, PAN Tiancou 2024, 45 (4):  417-424.  doi: 10.7657/XJPG20240405 Abstract ( 206 )   HTML ( 7 )   PDF (7182KB) ( 150 )   Save In the Ordovician carbonate rocks in the Tarim basin, there are extra-large oil and gas oilfields controlled by strike-slip faults. However, the distributions of carbonate reservoirs and hydrocarbons along the fault zones is extraordinarily complex, posing challenges for well deployment and efficient petroleum development. Taking the FⅠ17 hydrocarbon-rich strike-slip fault zone as an example, a fine structural analysis was conducted by using high-resolution seismic data. Coupling with core, logging and production data, the reservoir distribution and its controls on hydrocarbon accumulation were investigated. The results show that the FⅠ17 strike-slip fault zone can be divided into five segments from south to north: parallel en echelon segment, linear segment, superimposed segment, oblique superimposed segment, and horse-tail segment. The distribution, scale, and type of strike-slip faults govern the reservoir distribution and development. From the parallel en echelon segment to the oblique superimposed segment, the fault development intensifies, resulting in larger and more interconnected reservoirs. Conversely, the horse-tail segment in the north features reservoirs distributed along branch faults with poor connectivity. The fault-controlled hydrocarbon reservoirs in the FⅠ17 strike-slip fault zone can be classified into four types: linear fixed-volume, connected superimposed, superimposed fault-block, and tail-end dispersed. The type and scale of strike-slip faults control the reservoir types and hydrocarbon enrichment levels, necessitating targeted drilling strategies for different fault-controlled reservoir types. Figures and Tables | References | Related Articles | Metrics

Differential Controls of Strike-Slip Faults of Different Orders on Carbonate Reservoirs DU Zhongyuan, LI Xiangwen, LI Qinglin, SUN Chong, LI Mohan, ZHANG Guanqing, DAN Guangjian 2024, 45 (4):  425-431.  doi: 10.7657/XJPG20240406 Abstract ( 179 )   HTML ( 6 )   PDF (8025KB) ( 134 )   Save Differential spatial structures of the fault-controlled karst reservoirs constrain the efficient development of these reservoirs. The pore structure has been substantially studied for high-order strike-slip fault-controlled reservoirs, but rarely for low-order strike-slip fault-controlled reservoirs. Taking the Fuman oilfield in the northern depression of the Tarim basin as an example, different orders of strike-slip fault-controlled reservoirs were analyzed from the aspects of stress, depositional environment, and lithology, to compare their genesis and differences of pore structure, and the origins and exploration potentials of low-order strike-slip faults were examined. It is found that high-order strike-slip faults underwest strong faulting, resulting in an inverted triangular fracture pattern in the reservoir, with a decreasing scale from top to bottom. In contrast, low-order strike-slip faults experienced relatively weaker tectonic stress, leading to a normal triangular fracture pattern in the reservoir, with an increasing scale from top to bottom. The fracturing scale induced by low-order strike-slip faults is limited; however, a densely developed fracture network can lead to extensive reservoir fracturing. The primary factors influencing reservoir development are the depositional environment and lithology. The deep-seated low-order strike-slip faults in the Fuman oilfield can be divided into three zones from west to east, showing significant exploration potential. Figures and Tables | References | Related Articles | Metrics

Types and Distribution of Grain Shoals in Yijianfang Formation of Fuman Area, Tarim Basin ZHU Yongfeng, ZHANG Yanqiu, YANG Xinying, YANG Guang, PENG Debing, HAN Yu, WANG Zhenyu 2024, 45 (4):  432-441.  doi: 10.7657/XJPG20240407 Abstract ( 211 )   HTML ( 9 )   PDF (11635KB) ( 126 )   Save To clarify the types and distribution of grain shoals in the Middle Ordovician Yijianfang formation in the Fuman area of the Tarim basin, the sedimentary facies and distribution were studied using the core, rock thin section, carbon isotope, logging, and seismic data. The sedimentary facies of the Yijianfang formation in the study area can be categorized into slope-basin, platform margin, and open platform, with the latter two being the principal zones for grain shoal development. The grain shoals which include psammitic shoal, oolitic shoal, bioclastic shoal, and transitional types, generally account for over 80% of the formation thickness, or even over 90% in some well blocks. The distribution of these shallow grain shoals are primarily under the control of sedimentation processes represented by lateral migration in the setting of rapid marine transgression and gradual marine regression. The psammitic shoals and bioclastic-psammitic shoals extensively distributed in the open platform indicates excellent reservoir quality, and they will be significant targets for future petroleum exploration. Figures and Tables | References | Related Articles | Metrics

Establishment of Geological Model of Ancient Pockmarks in Fuman Oilfield, Tarim Basin LI Mohan, LI Xiangwen, DU Zhongyuan, ZHANG Yintao, JIN Meng, WANG Ziao 2024, 45 (4):  442-450.  doi: 10.7657/XJPG20240408 Abstract ( 159 )   HTML ( 12 )   PDF (17755KB) ( 78 )   Save For the pockmarks between major faults and in deep marginal-platform beaches in the Fuman oilfield, a seismic geological model was established based on the detailed interpretation of 3D seismic data and the analysis of the drilling and seismic data in the oilfield. This model enabled a simulated analysis of the variations in seismic response characteristics of the ancient pockmarks in the oilfield by altering the factors such as pockmark scale and fracture density. Consequently, seismic-based pockmark identification models were proposed, along with an understanding of the distribution, genesis and hydrocarbon potential of the pockmarks. The study results provides a foundation for the effective prediction of Ordovician ancient pockmark reservoirs in the Fuman oilfield, Tarim basin. Figures and Tables | References | Related Articles | Metrics

RESERVOIR ENGINEERING

Oil-Water Two-Phase Flow Behaviors in Fracture-Cavity Carbonate Reservoirs With Fluid-Solid Coupling LIU Qiang, LI Jing, LI Ting, ZHENG Mingjun, XU Mengjia, WANG Xuan, WU Mingyang 2024, 45 (4):  451-459.  doi: 10.7657/XJPG20240409 Abstract ( 191 )   HTML ( 10 )   PDF (4788KB) ( 265 )   Save To enhance the recovery of fracture-cavity carbonate reservoirs and investigate the oil-water two-phase flow behaviors under fluid-solid coupling effect, a Darcy-Stokes two-phase flow model was established based on the fluid flow patterns in different media. According to the principles of effective stress and the generalized Hooke’s law, an oil-water two-phase Darcy-Stokes coupled mathematical model suitable for fracture-cavity carbonate reservoirs was developed. Macroscopic and microscopic simulations of oil-water two-phase flows were conducted for carbonate reservoirs with and without fluid-solid coupling effect. The results show a significant difference in oil-water two-phase flow behaviors within the matrix zones of reservoirs with and without fluid-solid coupling effect, but a small difference within cavities. Water injection rate greatly influences oil-water flows in fracture-cavity carbonate reservoirs. Figures and Tables | References | Related Articles | Metrics

Dynamic Model and Sensitivity Analysis of High-Pressure Water Injection for Capacity Expansion of Fractured-Vuggy Reservoirs ZHANG Rujie, CHEN Lixin, YUE Ping, XIAO Yun, WANG Xia, LYU Yuan, YANG Wenming 2024, 45 (4):  460-469.  doi: 10.7657/XJPG20240410 Abstract ( 190 )   HTML ( 9 )   PDF (964KB) ( 206 )   Save High-pressure water injection for capacity expansion is an effective method to enhance the recovery of fractured-vuggy reservoirs. However，the injection-production process during high-pressure water injection remains unclear. In this paper，three modes of high-pressure water injection for capacity expansion were proposed. Based on a dynamic model of high-pressure water injection for capacity expansion，the impacts of sensitivity parameters on the injection-production process during high-pressure water injection were simulated. The three modes of high-pressure water injection for capacity expansion were analyzed using actual wells drilled in the fractured-vuggy reservoirs in Halahatang oilfield. The high-pressure water injection for capacity expansion conforms to three modes：far-end low-energy，flow barrier，and near-end small reservoir. All three modes can realize effective production of far-end reservoirs to improve recovery efficiency. Flow barrier mode has the optimal EOR effect. The size of the near-end reservoir affects the time at which the water-injection indicator curve inflects，and the size of the far-end reservoir influences the difficulty degree of water injection after the water-injection indicator curve inflects. The fluid exchange index in the water injection process is greater than that in the production process，which indicates that the high-pressure water injection for capacity expansion is effective. The smaller the fracture closure pressure and stress sensitivity coefficient，the earlier the water-injection indicator curve inflects，and the higher the cumulative liquid production. Figures and Tables | References | Related Articles | Metrics

Enhanced Recovery in Middle and Late Stages of Depletion Development of Condensate Gas Reservoirs With Oil Ring HUANG Zhaoting, LI Chuntao, WANG Bin, QIAO Xia, FU Ying, YAN Bingxu 2024, 45 (4):  470-474.  doi: 10.7657/XJPG20240411 Abstract ( 236 )   HTML ( 10 )   PDF (549KB) ( 186 )   Save The depletion development of Y5 condensate gas reservoir in the Tarim basin encounters the challenges such as rapid decline in both reservoir pressure and well productivity, gradual decrease in produced gas-oil ratio, increase in condensate oil density and viscosity, and fast downgrading of development performance. Combining performance analysis and reservoir fluid component evaluation, the Y5 condensate gas reservoir was redefined as a layered condensate gas reservoir with oil ring and edge water and the thickness of the oil ring was determined through numerical simulation. To improve the development performance and enhance the condensate oil/gas recovery, a systematic investigation was conducted on the mechanism of enhanced recovery in the middle and late stages of depletion development of the condensate gas reservoir with oil ring. It is found that optimizing the well pattern and implementing cyclic gas injection can significantly improve oil and gas recovery. Gravity-assisted gas drive is recommended, with CO2 being the optimal injection medium, followed by reservoir gas. Based on reservoir type and enhanced recovery mechanism, a scheme of cyclic gas injection for enhancing the recovery of Y5 condensate gas reservoir was developed, with an expected oil recovery 29.96% higher than that of depletion development alone. Under this scheme, a cumulative gas volume of 0.19×108 m3 was injected, the reservoir pressure restored by 4.31 MPa, and the well productivity increased by 3.09 times compared to that before the scheme was implemented. The research results provide valuable reference for enhancing recovery in the middle and late development stages of similar reservoirs. Figures and Tables | References | Related Articles | Metrics

APPLICATION OF TECHNOLOGY

Seismic Identification of Strike-Slip Fault Damage Zones Based on Structure Tensor Analysis: A Case Study of Ultra-Deep Carbonate Rocks in Fuman Oilfield WANG Rujun, SUN Chong, YUAN Jingyi, LIU Ruidong, WANG Xuan, MA Yinglong, WANG Xupeng 2024, 45 (4):  475-482.  doi: 10.7657/XJPG20240412 Abstract ( 199 )   HTML ( 7 )   PDF (4592KB) ( 329 )   Save Abundant hydrocarbon resources have been discovered in the ultra-deep Ordovician carbonate strike-slip fault damage zones of the Tarim basin. However, these zones cannot be accurately characterized due to the low resolution of seismic data obtained from the ultra-deep layers, thereby restricting the efficient evaluation and target selection of the strike-slip fault-controlled hydrocarbon reservoirs. According to the seismic responses of the strike-slip fault damage zones in the Fuman oilfield, and based on the structure-oriented filtering, the eigenvalues and eigenvectors were calculated by using the structure tensor method, and the projection energy along the fault direction was enhanced by selecting appropriate time windows and stacking vertical thicknesses, which accentuates the strike-slip fault damage zones, enabling a clearer delineation of their boundaries and intensities. The results show that this method provides a clearer depiction of strike-slip fault distribution, allows for the identification of smaller-scale faults, and effectively delineates the width and intensity of ultra-deep carbonate strike-slip fault damage zones, which can be used to evaluate the development degree of the strike-slip fault damage zones. This method can be employed in trap evaluation, well placement, trajectory design, and well monitoring, which will improve drilling success rates and individual well productivity. Figures and Tables | References | Related Articles | Metrics

Application of Multi-Attribute Constrained Prestack Wide-Azimuth Fracture Prediction in Yingmai-2 Area ZENG Yongjian, GAO Hongliang, GUAN Baozhu, AI Mingbo, CAI Quan, LI Fei, WANG Zhangheng 2024, 45 (4):  483-488.  doi: 10.7657/XJPG20240413 Abstract ( 173 )   HTML ( 10 )   PDF (10109KB) ( 111 )   Save The Yingmai-2 area is situated on the Yingmai-2 structure in the southern part of the Yingmaili low bulge of the Tabei uplift, Tarim basin. Affected by tectonic movements and magmatic intrusion, a large number of directionally-aligned high-angle fractures were developed on the structure. The reservoirs are mainly fractured. Due to the deep burial depth and strong heterogeneity of the reservoirs in the Yingmai-2 area, predicting these fractured reservoirs using post-stack fracture prediction techniques like coherence, curvature, and ant-tracking proves challenging. Based on the pre-stack wide-azimuth offset vector tile (OVT) domain gather data from the Yingmai-2 area, well-controlled optimization processing of pre-stack OVT domain gather was implemented by employing techniques such as pre-stack denoising and anisotropy time difference correction to yield high-quality pre-stack wide-azimuth gather data. Subsequently, pre-stack facies-controlled fracture prediction was conducted under the constraints of post-stack multiple attributes that can represent fractured-vuggy reservoirs, including gradient structure tensor, amplitude curvature, and residual wave impedance. This methodology can effectively predict fractures in ultra-deep fractured-vuggy carbonate reservoirs, and offer valuable insights for the exploration and development of fractured reservoirs in the Tarim basin. Figures and Tables | References | Related Articles | Metrics

3D Seismic Imaging Technology and Its Application in GCD Work Area of Tarim Basin CHEN Keyang, ZHOU Hui, WANG Cheng, LIU Yang, LIU Jianying, WANG Yangyang, LIU Jishun 2024, 45 (4):  489-498.  doi: 10.7657/XJPG20240414 Abstract ( 165 )   HTML ( 7 )   PDF (30192KB) ( 115 )   Save The GCD work area of the Tarim basin is covered by desert, where the acquired seismic data are superimposed with high-energy sand dune resonance noise due to the loose and thick dune structures, hampering the accurate imaging of the Ordovician marine reef-beach reservoir. Conventional imaging methods are disadvantageous due to low resolution, defocusing and other defects. On the basis of fidelity-based seismic processing, a three-step method for substantial attenuation of the sand dune resonance noise was incorporated. The 3D frequency space domain pre-stack random noise suppression technology was adopted to enhance the signal-to-noise ratio (SNR) of pre-stack preprocessing gathers. Furthermore, vertical seismic profile velocity, logging data, and interpreted horizons were combined to enable a multi-information-constrained grid tomography modeling and anisotropic reverse time migration. The results show that the sand dune resonance noise is effectively attenuated, and the SNR of pre-stack seismic data is significantly improved as compared to conventional denoising methods. The residual random seismic noise in pre-stack gathers is effectively suppressed, and the post-processing energy in velocity spectra of the gathers is more focused, facilitating precise velocity model establishment. Based on the high-density seismic imaging gathers, depth-domain model inversion where the inversion grid is gradually refined from coarse to fine was performed, and the established velocity model can accurately characterize the Ordovician marine reef-beach reservoirs. Anisotropic reverse time migration accurately relocated the complex wavefields of the Ordovician marine reef-beach reservoirs, enhancing resolution and focusing. The research results provide a support for optimizing the design of the sidetracking trajectory for Well G1 in the GCD work area, which was validated by actual drilling results. These techniques can provide a robust technical support for high-precision imaging and processing of seismic data in desert areas of the Tarim basin. Figures and Tables | References | Related Articles | Metrics

Dynamic Reserves Calculation Method for Fault-Controlled Carbonate Reservoirs GENG Jie, YUE Ping, YANG Wenming, YANG Bo, ZHAO Bin, ZHANG Rujie 2024, 45 (4):  499-504.  doi: 10.7657/XJPG20240415 Abstract ( 258 )   HTML ( 11 )   PDF (960KB) ( 278 )   Save Fault-controlled carbonate reservoirs are highly heterogeneous, with interweaving development of pores, fractures, and vugs of various sizes. For this kind of reservoirs, the dynamic reserves calculated using conventional material balance methods may be larger than the static reserves. By incorporating water-oil ratio and considering rock compressibility coefficients for different pore-fracture-vug media, a comprehensive compressibility coefficient suitable for the fault-controlled reservoirs was derived. On this basis, a new flow material balance equation was established for the fault-karst reservoir, and its accuracy and applicability were verified using numerical simulation. The research results show that the dynamic reserves calculated by the new equation have an error of only 0.1099% with the static reserves obtained from numerical simulation, confirming the new equation’s reliability and accuracy. In the Halahatang area, the relative error between the dynamic reserves calculated using the new equation and the static reserves derived from geological modeling for multiple wells ranged from -4.82% to -0.15%, which is significantly lower than that calculated using the conventional material balance equation. The results obtained from the new equation are closer to actual conditions, making it more suitable for calculating the reserves of the fault-controlled carbonate reservoirs in the Halahatang area. Figures and Tables | References | Related Articles | Metrics