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Shale gas plays a crucial role in the national energy supply. However, fast pressure drop, production decline, and water resources pollution caused by well interference and fracture hits become more severe in multi‐layer mining shale gas fields. Such as, it is urgent to evaluate the interference of multi‐stage fracturing horizontal wells (MFHWs) between the upper and lower gas layers in Chinese Jiaoshiba shale gas field. Therefore, we put forward a comprehensive method to analyze the MFHW interference in this paper. The method contains bottom‐hole pressure response analysis (BHPRA) during neighboring well fracturing, BHPRA of well interference test, and production dynamic analysis. Our study indicates that longitudinal pressure interference exists between the Jiaoshiba upper and lower gas layers upon the apparent interference pressure response in a multi‐well test. However, MFHW interferences occur in the corresponding fracturing stages with shorter distance, and the interference strength is related to both well distance and fracturing scales. The Jiaoshiba upper gas layers can be developed to increase the gas production performance, but it is necessary to maintain a reasonable well spacing to avoid severe interference during the development.
Dapeng Gao; Yuewu Liu; Songqi Pan; Jue Wang; Xinmao Zhou. Longitudinal interference analysis of shale gas multi‐stage fracturing horizontal wells upon high‐precision pressure test. Energy Science & Engineering 2020, 8, 2387 -2401.
AMA StyleDapeng Gao, Yuewu Liu, Songqi Pan, Jue Wang, Xinmao Zhou. Longitudinal interference analysis of shale gas multi‐stage fracturing horizontal wells upon high‐precision pressure test. Energy Science & Engineering. 2020; 8 (7):2387-2401.
Chicago/Turabian StyleDapeng Gao; Yuewu Liu; Songqi Pan; Jue Wang; Xinmao Zhou. 2020. "Longitudinal interference analysis of shale gas multi‐stage fracturing horizontal wells upon high‐precision pressure test." Energy Science & Engineering 8, no. 7: 2387-2401.
After the large-scale horizontal well pattern development in shale gas fields, the problem of fast pressure drop and gas well abandonment caused by well interference becomes more serious. It is urgent to understand the downhole transient pressure and flow characteristics of multi-stage fracturing horizontal well (MFHW) with interference. Therefore, the reservoir around the MFHW is divided into three regions: fracturing fracture, Stimulated reservoir volume (SRV), and unmodified matrix. Then, multi-region coupled flow model is established according to reservoir physical property and flow mechanism of each part. The model is numerically solved using the perpendicular bisection (PEBI) grids and the finite volume method. The accuracy of the model is verified by analyzing the measured pressure recovery data of one practical shale gas well and fitting the monitoring data of the later production pressure. Finally, this model is used to analyze the effects of factors, such as hydraulic fractures’ connectivity, well distance, the number of neighboring wells and well pattern arrangement, on the transient pressure and seepage characteristics of the well. The study shows that the pressure recovery double logarithmic curves fall in later part when the well is disturbed by a neighboring production well. The earlier and more severe the interference, the sooner the curve falls off and the larger the amplitude shows. If the well distance is closer, and if there are more neighboring wells and interconnected corresponding fracturing segments, the more severe interference appears among the wells. Moreover, the well interference may still exist even without interlinked fractures or SRV. Especially, severe interference will affect production when the hydraulic fractures are connected directly, and the interference is weaker when only SRV induced fracture network combined between wells, which is beneficial to production sometimes. When severe well interference occurs, periodic well shut-in is needed to help restore the reservoir pressure and output capacity. In the meanwhile, the daily output should be controlled reasonably to prolong the stable production time. This research will help to understand the impact of well interference to gas production, and to optimize the well spacing and achieve satisfied performance.
Dapeng Gao; Yuewu Liu; Daigang Wang; Guofeng Han. Numerical Analysis of Transient Pressure Behaviors with Shale Gas MFHWs Interference. Energies 2019, 12, 262 .
AMA StyleDapeng Gao, Yuewu Liu, Daigang Wang, Guofeng Han. Numerical Analysis of Transient Pressure Behaviors with Shale Gas MFHWs Interference. Energies. 2019; 12 (2):262.
Chicago/Turabian StyleDapeng Gao; Yuewu Liu; Daigang Wang; Guofeng Han. 2019. "Numerical Analysis of Transient Pressure Behaviors with Shale Gas MFHWs Interference." Energies 12, no. 2: 262.
Pressure communication between adjacent wells is frequently encountered in multi-stage hydraulic fractured shale gas reservoirs. An interference test is one of the most popular methods for testing the connectivity of a reservoir. Currently, there is no practical analysis model of an interference test for wells connected by large fractures. A one-dimensional equation of flow in porous media is established, and an analytical solution under the constant production rate is obtained using a similarity transformation. Based on this solution, the extremum equation of the interference test for wells connected by a large fracture is derived. The type-curve of pressure and the pressure derivative of an interference test of wells connected by a large fracture are plotted, and verified against interference test data. The extremum equation of wells connected by a large fracture differs from that for homogeneous reservoirs by a factor 2. Considering the difference of the flowing distance, it can be concluded that the pressure conductivity coefficient computed by the extremum equation of homogeneous reservoirs is accurate in the order of magnitude. On the double logarithmic type-curve, as time increases, the curves of pressure and the pressure derivative tend to be parallel straight lines with a slope of 0.5. When the crossflow of the reservoir matrix to the large fracture cannot be ignored, the slope of the parallel straight lines is 0.25. They are different from the type-curves of homogeneous and double porosity reservoirs. Therefore, the pressure derivative curve is proposed to diagnose the connection form of wells.
Guofeng Han; Yuewu Liu; Wenchao Liu; Dapeng Gao. Investigation on Interference Test for Wells Connected by a Large Fracture. Applied Sciences 2019, 9, 206 .
AMA StyleGuofeng Han, Yuewu Liu, Wenchao Liu, Dapeng Gao. Investigation on Interference Test for Wells Connected by a Large Fracture. Applied Sciences. 2019; 9 (1):206.
Chicago/Turabian StyleGuofeng Han; Yuewu Liu; Wenchao Liu; Dapeng Gao. 2019. "Investigation on Interference Test for Wells Connected by a Large Fracture." Applied Sciences 9, no. 1: 206.
Coalbed Methane (CBM) has become an important gas resource in recent decades. The brittle property of coal matrix and overactive operation make the migration of coal fines inevitable. Blockage by coal fines that plugs flow paths is a non-negligible issue that results in a significant decline in gas production. By setting different experimental conditions with the following factors—coal fines concentration of the mixture displacing fluids, constant flow pump rate, inlet pressure, outlet pressure and confining pressure—six experimental schemes were designed to investigate the two-phase water and coal fines flow in natural core samples. When the differential pressure and flooding flow reach a pseudo-steady status, the equivalent permeability of coal samples can be approximately calculated considering coal fines migration. Furthermore, the influences of coal fines migration on the cleat opening and permeability variation are analyzed in the porous coal medium. The study will benefit CBM development and save pump maintenance costs. In this work, we found that maintaining the differential pressure for a longer period may result in new cleat openings and severe coal rock damage during the single-phase water flooding process. While coal fines may plug some natural cleats and pores, especially in the core samples with micro-cleats during the two-phase flooding stage, coal fines migration significantly reduces the equivalent permeability and dewatering ability of the coal rock in the earlier flooding. While enlarging the differential pressure in two-phase water and fines flooding, breakthrough of coal fines from the samples contributes to widened cleats. While coal fines are difficult to flood into the core pores for low-permeability core samples, coal fines gather in the inlet, and it is also difficult to reach the pseudo-steady status even under higher differential pressure. The damage to permeability mainly occurs in the early stage of coal fines migration, and an abrupt increase in the flow velocity can damage reservoirs and induce substantial coal fines generation. Thus, maintaining a stable effective strength and a controlled depressurization rate during drainage can effectively constrain coal fines output and decrease permeability damage within coal reservoirs.
Dapeng Gao; Yuewu Liu; Tianjiao Wang; Daigang Wang. Experimental Investigation of the Impact of Coal Fines Migration on Coal Core Water Flooding. Sustainability 2018, 10, 4102 .
AMA StyleDapeng Gao, Yuewu Liu, Tianjiao Wang, Daigang Wang. Experimental Investigation of the Impact of Coal Fines Migration on Coal Core Water Flooding. Sustainability. 2018; 10 (11):4102.
Chicago/Turabian StyleDapeng Gao; Yuewu Liu; Tianjiao Wang; Daigang Wang. 2018. "Experimental Investigation of the Impact of Coal Fines Migration on Coal Core Water Flooding." Sustainability 10, no. 11: 4102.
Pore compressibility is an important parameter in reservoir engineering. However, its variation from laboratory core analysis or logging data can be large. Moreover, laboratory core analysis cannot identify the influence of macroscopic fractures on pore compressibility. The geological reserves obtained with the commonly used flowing material balance (FMB) method are significantly impacted by the accuracy of the pore compressibility. Therefore, a new form of the FMB method is proposed in this study which can determine the pore compressibility and geological reserves at the same time. For gas wells, the new method uses the material balance equation and the FMB equation including the pore compressibility. For oil wells, new forms of the material balance equation and the FMB equation were established which have the same form as the corresponding equations for gas wells. A new linear expression of the material balance equation is employed for the analysis. Simulation results indicate that the new method can provide more precise predictions of both the pore compressibility and the geological reserves. Furthermore, the new method also considers the influence of formation fractures because it uses well production data. Sensitivity analysis indicates that the error in the pore compressibility has a significant influence on the determination of the geological reserves.
Guofeng Han; Yuewu Liu; Liang Sun; Min Liu; Dapeng Gao; Qi Li. Determination of pore compressibility and geological reserves using a new form of the flowing material balance method. Journal of Petroleum Science and Engineering 2018, 172, 1025 -1033.
AMA StyleGuofeng Han, Yuewu Liu, Liang Sun, Min Liu, Dapeng Gao, Qi Li. Determination of pore compressibility and geological reserves using a new form of the flowing material balance method. Journal of Petroleum Science and Engineering. 2018; 172 ():1025-1033.
Chicago/Turabian StyleGuofeng Han; Yuewu Liu; Liang Sun; Min Liu; Dapeng Gao; Qi Li. 2018. "Determination of pore compressibility and geological reserves using a new form of the flowing material balance method." Journal of Petroleum Science and Engineering 172, no. : 1025-1033.
Lots of multi-layer heterogeneous sandstone reservoirs have reached extreme high water content and high recovery after long-time water-flooding development, and their low-permeability thin oil layers (LPTOLs) have gradually been the main potential reserves. Therefore, taking the geology of LPTOLs into account, an independent water-flooding development (IWD) method with stratified hydraulic fracturing (SHF) for LPTOLs is put forward. The method combines undeveloped LPTOLs as an individual strata series in one injection-production system, and the HPTOLs even with low water content are abandoned in order to reduce the reservoir vertical heterogeneity. To realize economic benefits, mature stratified hydraulic fracturing is necessary to increase production. The key of IWD is selecting and combining appropriate LPTOLs in an individual strata series. Two development modes, OW-OL and WW-OL, are designed by different wells' perforations and the oil layers' distribution. The difference between these two modes mainly depends on whether the oil-wells perforate the HPTOLs connected with the LPTOLs. Upon an embedded fracture model for simulating hydraulic fractures, the oil production and water content of one LPTOL are calculated with different physical factors of reservoir and fractures. According to the cumulative oil production under different factors, their impact degrees are evaluated by gray relative analysis method. Permeability, oil layer thickness and oil viscosity are three main factors influencing the development of LPTOLs, and flow coefficient is a comprehensive index composed of these three factors. Therefore, the flow coefficient variation degree is a core indicator to evaluate the vertical heterogeneity of an individual strata series, and IWD will get better water-flooding effect with lower flow coefficient variation degree. In order to analyze the effect of IWD, 30 cases are designed with different flow coefficient variation degree, different thickness of HPTOL and different IWD modes. Oil production and water content variation of two development modes are studied by simulation. OW-OL mode is superior to the WW-OL mode on water-flooding recovery. That is because the oil is mainly produced from layered-LPTOLs with less water content, the vertical water-flooding efficiency is higher at the production side, and the whole displacement is more balanced in the whole OW-OL strata series. IWD of LPTOLs is not only suitable for Chinese sandstone oilfields, but also has a general significance for other multi-layer sandstone reservoirs owing high-potential LPTOLs.
Gao Dapeng; Ye Jigen; Wang Tianjiao; Zhao Liang; Pan Songqi; Sun Zhenglong. An independent fracturing water-flooding development method for shallow low-permeability thin oil layers in multi-layer sandstone reservoirs. Journal of Petroleum Science and Engineering 2018, 167, 877 -889.
AMA StyleGao Dapeng, Ye Jigen, Wang Tianjiao, Zhao Liang, Pan Songqi, Sun Zhenglong. An independent fracturing water-flooding development method for shallow low-permeability thin oil layers in multi-layer sandstone reservoirs. Journal of Petroleum Science and Engineering. 2018; 167 ():877-889.
Chicago/Turabian StyleGao Dapeng; Ye Jigen; Wang Tianjiao; Zhao Liang; Pan Songqi; Sun Zhenglong. 2018. "An independent fracturing water-flooding development method for shallow low-permeability thin oil layers in multi-layer sandstone reservoirs." Journal of Petroleum Science and Engineering 167, no. : 877-889.
Different from the conventional gas reservoir, coalbed methane is developed mainly by water drainage, which leads methane desorption after reservoir pressure drop. Water drainage at a reasonable speed in the early development stage is the key for enhancing later gas performance. Therefore, the investigation radius, which reflects the pressure drop region scale, is studied by deconvolution well-test to find the reasonable water drainage speed in the early period. First, the early production data (well-bottom pressure and water rate) are processed by deconvolution algorithm, and then the pressure data under unit rate is obtained to invert the comprehensive reservoir permeability and investigation radius. This deconvolution method can save the cost of the conventional well-test, and avoid reservoir damage caused by frequent well shut-off. The feasibility of the deconvolution test method is verified by comparing its interpretation results with those of the conventional pressure drop/build-up test. For a field application, the 29 wells’ comprehensive permeability are inverted by the deconvolution well-test using early water production data of Hancheng block. Furthermore, their investigation radius and pressure drawdown gradient are calculated, and the performance optimization is determined by relationship analysis between working fluid level and steady gas production rate. We find that well-bottom pressure and reservoir pressure should decrease steadily in the early development stage, with the working fluid level declining less than 1 m/d (1 m per day) in wellbore, and the pressure drawdown gradient declining less than 2.8 MPa/100 m.
Dapeng Gao; Yuewu Liu; Zhidong Guo; Jun Han; Jingde Lin; Huijun Fang; Hailing Ma; Sang-Bing Tsai. A Study on Optimization of CBM Water Drainage by Well-Test Deconvolution in the Early Development Stage. Water 2018, 10, 929 .
AMA StyleDapeng Gao, Yuewu Liu, Zhidong Guo, Jun Han, Jingde Lin, Huijun Fang, Hailing Ma, Sang-Bing Tsai. A Study on Optimization of CBM Water Drainage by Well-Test Deconvolution in the Early Development Stage. Water. 2018; 10 (7):929.
Chicago/Turabian StyleDapeng Gao; Yuewu Liu; Zhidong Guo; Jun Han; Jingde Lin; Huijun Fang; Hailing Ma; Sang-Bing Tsai. 2018. "A Study on Optimization of CBM Water Drainage by Well-Test Deconvolution in the Early Development Stage." Water 10, no. 7: 929.
While the introduction of a high speed rail (HSR) provides passengers with another more environmentally friendly, convenient, and time-saving transport option, it also disrupts the existing passenger transport market. This study adopts time series analysis to model the dynamic competition in a regional passenger transport market when an HSR is introduced. The analyses include examining the long-run equilibrium and causal relationships, and the short-run causality and dynamic relationships between transport modes. In addition, based on the model we conduct impulse response tests and variance decomposition tests to further interpret the interactions between two transport modes. An empirical study is carried out, and the findings indicate that the HSR has a negative impact on conventional rail and air transport in the long-run. In the short-run dynamics, the air passenger transport volume could be regarded as a good predictor of HSR passenger volume. In turn, the HSR passenger volume could be used to predict conventional rail transport volume. The operations of HSR and conventional rail are complementary in the short term. From the short-run market viewpoint, the HSR and conventional rail meet different kinds of passenger demand. Therefore, a previous increased passenger volume for the HSR implies an overall increasing demand for regional transport. Consequently, the past increased HSR passenger volume could be used to predict the growth of conventional rail transport. Through the impulse response test, we can further track the responses of the three transport modes to the shocks from themselves and each other.
Ching-Chih Chou; Chien-Wen Shen; Dapeng Gao; Yang Gao; Kai Wang; Sang-Bing Tsai. Modelling the Dynamic Impacts of High Speed Rail Operation on Regional Public Transport—From the Perspective of Energy Economy. Energies 2018, 11, 1151 .
AMA StyleChing-Chih Chou, Chien-Wen Shen, Dapeng Gao, Yang Gao, Kai Wang, Sang-Bing Tsai. Modelling the Dynamic Impacts of High Speed Rail Operation on Regional Public Transport—From the Perspective of Energy Economy. Energies. 2018; 11 (5):1151.
Chicago/Turabian StyleChing-Chih Chou; Chien-Wen Shen; Dapeng Gao; Yang Gao; Kai Wang; Sang-Bing Tsai. 2018. "Modelling the Dynamic Impacts of High Speed Rail Operation on Regional Public Transport—From the Perspective of Energy Economy." Energies 11, no. 5: 1151.
Jianping Yang; Qi Li; Fangfang Chen; Yuewu Liu; Jian Zhang; Dapeng Gao. Study on Interference Testing of Fractured-Vuggy Carbonate Reservoirs. Proceedings of the Advances in Materials, Machinery, Electrical Engineering (AMMEE 2017) 2017, 1 .
AMA StyleJianping Yang, Qi Li, Fangfang Chen, Yuewu Liu, Jian Zhang, Dapeng Gao. Study on Interference Testing of Fractured-Vuggy Carbonate Reservoirs. Proceedings of the Advances in Materials, Machinery, Electrical Engineering (AMMEE 2017). 2017; ():1.
Chicago/Turabian StyleJianping Yang; Qi Li; Fangfang Chen; Yuewu Liu; Jian Zhang; Dapeng Gao. 2017. "Study on Interference Testing of Fractured-Vuggy Carbonate Reservoirs." Proceedings of the Advances in Materials, Machinery, Electrical Engineering (AMMEE 2017) , no. : 1.
Lixin Chen; Yuewu Liu; Zhongqian Zhu; Dapeng Gao; Wen Cao; Qi Li. The Discrete Numerical Models and Transient Pressure Curves of Fractured-Vuggy Units in Carbonate Reservoir. Proceedings of the Advances in Materials, Machinery, Electrical Engineering (AMMEE 2017) 2017, 1 .
AMA StyleLixin Chen, Yuewu Liu, Zhongqian Zhu, Dapeng Gao, Wen Cao, Qi Li. The Discrete Numerical Models and Transient Pressure Curves of Fractured-Vuggy Units in Carbonate Reservoir. Proceedings of the Advances in Materials, Machinery, Electrical Engineering (AMMEE 2017). 2017; ():1.
Chicago/Turabian StyleLixin Chen; Yuewu Liu; Zhongqian Zhu; Dapeng Gao; Wen Cao; Qi Li. 2017. "The Discrete Numerical Models and Transient Pressure Curves of Fractured-Vuggy Units in Carbonate Reservoir." Proceedings of the Advances in Materials, Machinery, Electrical Engineering (AMMEE 2017) , no. : 1.