Fracturing Well Production Dynamic Simulation in Fractured Tight Sandstone Gas Reservoir

2013 ◽  
Vol 457-458 ◽  
pp. 410-415
Author(s):  
Chao Yang Xie ◽  
Yong Quan Hu ◽  
Xing Chen ◽  
Ying Chao Ma ◽  
Jin Zhou Zhao ◽  
...  
Keyword(s):  
Flow Coefficient ◽  
Production Performance ◽  
Natural Fracture ◽  
Inverse Transformation ◽  
Hydraulic Fractures ◽  
Fractured Reservoir ◽  
Tight Sandstone ◽  
Gas Reservoir ◽  
Sandstone Reservoir ◽  
Effective Development

The tight sandstone formation usually has natural fracture, which is the foundation of effective development using hydraulic fracturing. The conventional reservoir productivity simulation method don't adapt to it. In this paper, Warren & Root model was used for describing infinity tight fractured reservoir model with vertical hydraulic fractures. Then, assuming the fracture length and the width does not vary with time and formation pressure, fracture seepage equation was obtained in base of the one-dimensional flow Darcy percolation equation and continuity equation. By Stehfese, a method of numerical inverse transformation, production performance simulation model was established for natural fractured tight sandstone reservoir. Taking for actual example from Daqing oilfield, affection of characteristics of natural fractures and artificial fracture parameters on productivity of natural fractured tight sandstone reservoir were analyzed. Elastic storability ratio has a greater influence than interporosity flow coefficient. It was the core technique for the gas reservoir to effective development by large amount of fluid and low sand ratio.

Predicting Hydraulic Fracturing in a Carbonate Gas Reservoir in Abu Dhabi Using 1D Mechanical Earth Model: Uncertainty and Constraints

2015 ◽  
Author(s):  
Manhal Sirat ◽  
Mujahed Ahmed ◽  
Xing Zhang
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Natural Fracture ◽  
Abu Dhabi ◽  
Hydraulic Fractures ◽  
Gas Reservoir ◽  
In Situ Stresses ◽  
Tight Carbonate ◽  
Different Depths

Abstract In-situ stress state plays an important role in controlling fracture growth and containment in hydraulic fracturing managements. It is evident that the mechanical properties, existing stress regime and the natural fracture network of its reservoir rocks and the surrounding formations mainly control the geometry, size and containments of produced hydraulic fractures. Furthermore, the three principal in situ stresses' axes swap directions and magnitudes at different depths giving rise to identifying different mechanical bedrocks with corresponding stress regimes at different depths. Hence predicting the hydro-fractures can be theoretically achieved once all the above data are available. This is particularly difficult in unconventional and tight carbonate reservoirs, where heterogeneity and highly stress variation, in terms of magnitude and orientation, are expected. To optimize the field development plan (FDP) of a tight carbonate gas reservoir in Abu Dhabi, 1D Mechanical Earth Models (MEMs), involving generating the three principal in-situ stresses' profiles and mechanical property characterization with depth, have been constructed for four vertical wells. The results reveal the swap of stress magnitudes at different mechanical layers, which controls the dimension and orientation of the produced hydro-fractures. Predicted containment of the Hydro-fractures within the specific zones is likely with inevitable high uncertainty when the stress contrast between Sv, SHmax with Shmin respectively as well as Young's modulus and Poisson's Ratio variations cannot be estimated accurately. The uncertainty associated with this analysis is mainly related to the lacking of the calibration of the stress profiles of the 1D MEMs with minifrac and/or XLOT data, and both mechanical and elastic properties with rock mechanic testing results. This study investigates the uncertainty in predicting hydraulic fracture containment due to lacking such calibration, which highlights that a complete suite of data, including calibration of 1D MEMs, is crucial in hydraulic fracture treatment.

A Comprehensive Approach for Fracability Evaluation in Naturally Fractured Sandstone Reservoirs

2018 ◽  
Author(s):  
Zhaozhong Yang ◽  
Rui He ◽  
Xiaogang Li ◽  
Zhanling Li ◽  
Ziyuan Liu
Keyword(s):  
Large Scale ◽  
Evaluation Model ◽  
Gas Production ◽  
Natural Fracture ◽  
Tight Sandstone ◽  
Gas Reservoir ◽  
Related Factors ◽  
Gas Field ◽  
Tight Gas Reservoir ◽  
Naturally Fractured

The tight sandstone gas reservoir in southern Songliao Basin is naturally fractured and is characterized by its low porosity and permeability. Large-scale hydraulic fracturing is the most effective way to develop this tight gas reservoir. Quantitative evaluation of fracability is essential for optimizing a fracturing reservoir. In this study, as many as ten fracability-related factors, particularly mechanical brittleness, mineral brittleness, cohesion, internal friction angle, unconfined compressive strength (UCS), natural fracture, Model-I toughness, Model-II toughness, horizontal stress difference, and fracture barrier were obtained from a series of petrophysical and geomechanical experiments are analyzed. Taking these influencing factors into consideration, a modified comprehensive evaluation model is proposed based on the analytic hierarchy process (AHP). Both a transfer matrix and a fuzzy matrix were introduced into this model. The fracability evaluation of four reservoir intervals in Jinshan gas field was analyzed. Field fracturing tests were conducted to verify the efficiency and accuracy of the proposed evaluation model. Results showed that gas production is higher and more stable in the reservoir interval with better fracability. The field test data coincides with the results of the proposed evaluation model.

Study on Production Performance Simulating the Low Permeability Dual Media Gas Reservoirs Pre and Post Fracturing

2011 ◽  
Vol 287-290 ◽  
pp. 86-91
Author(s):  
Li Ying Wang ◽  
Shu Sheng Gao ◽  
Wei Xiong ◽  
Hua Xun Liu
Keyword(s):  
Early Stage ◽  
Cross Flow ◽  
Flow Coefficient ◽  
Production Performance ◽  
Natural Fracture ◽  
Low Permeability ◽  
Gas Reservoirs ◽  
Penetration Ratio ◽  
Order Of Magnitude ◽  
Porosity And Permeability

Mathematical model of dual media reservoir fracturing wells was established and the corresponding numerical calculation program was developed based on the special relationship between porosity and permeability of dual media low permeability gas reservoirs. Through comparative analysis of numerical results of production performance pre and post fracturing, effects of cross flow coefficient and fracture penetration ratio were well studied. The results show that: after a period of production, pressure decline of the gas well decreases linearly with time, whether fracturing or not, showing pseudo-steady-state characteristics; in the early stage, pressure drop in the vertical well pre-fracturing is an order of magnitude larger than the post-fracturing well in the logarithmic coordinate; the less developed the natural fracture is, the smaller the cross flow coefficient is, and the more significant role the fracturing plays in yield increasing; when the fracture penetration ratio is between 0.25~0.50, it has less impact on production, so it is suggested that the fracture penetration ratio is controlled at about 0.25 in actual dual media dense gas reservoirs.

Analysis of Tight Gas Reservoir Forming Condition in Gulong-Changjiaweizi Region, Northern Songliao Basin

2013 ◽  
Vol 652-654 ◽  
pp. 2478-2483
Author(s):  
Xue Juan Zhang ◽  
Shuang Fang Lu ◽  
Wei Huang ◽  
Lei Zhang
Keyword(s):  
Source Rock ◽  
Songliao Basin ◽  
Tight Gas ◽  
Tight Sandstone ◽  
Gas Reservoir ◽  
Gas Accumulation ◽  
Gas Source ◽  
Geological Conditions ◽  
Tight Gas Reservoir ◽  
Sandstone Reservoir

This paper makes systematic analysis of geological factors of natural gas accumulation in Denglouku formation of Gulong-Changjiaweizi region, including reservoir characteristics, gas source condition, source-reservoir relationship, structural condition, etc. It turned out that K1d2 in Gulong-Changjiaweizi region is generally typical tight sandstone reservoir with low porosity and permeability due to the poor physical properties. The gas source rock of K1d2 formation has larger gas producing capacity.The relationship between source rock and reservoir shows as interbed interfinger or directly contiguity contact, which is beneficial for large-area gas accumulation. The gas generation area of source rock in this region is always in the center and slow downdip direction of Gulong depression with a smaller dip angle on the adjacent tight sandstone reservoir, where faults are rare. The result of comprehensive analysis shows that K1d2 formation in Nothern Songliao Basin and its neighboring layers could be considered as a favorable target of the tight gas reservoir study in Northern Songliao Basin due to its favorable geological conditions of deep basin tight gas reservoir generation, such as tight reservoir, sufficient gas source, communicating source-reservoir relationship and constant flattened structure.

Case Study: 4D Coupled Reservoir/Geomechanics Simulation of a High-Pressure/High-Temperature Naturally Fractured Reservoir

SPE Journal ◽  
2018 ◽  
Vol 23 (05) ◽  
pp. 1518-1538 ◽  
Author(s):  
Xiangtong Yang ◽  
Yuanwei Pan ◽  
Wentong Fan ◽  
Yongjie Huang ◽  
Yang Zhang ◽  
...  
Keyword(s):  
Hydraulic Fracture ◽  
Natural Fracture ◽  
Hydraulic Fractures ◽  
Fracture System ◽  
Fractured Reservoir ◽  
Natural Fractures ◽  
Well Integrity ◽  
3D Geomechanical Model ◽  
Naturally Fractured ◽  
Reservoir Geomechanics

Summary The Keshen Reservoir is a naturally fractured, deep, tight sandstone gas reservoir under high tectonic stress. Because the reservoir matrix is very tight, the natural-fracture system is the main pathway for gas production. Meanwhile, stimulation is still required for most production wells to provide production rates that sufficiently compensate for the high cost of drilling and completing wells to access this deep reservoir. Large depletion (and related stress change) was expected during the course of the production of the field. The dynamic response of the reservoir and related risks, such as reduction of fracture conductivity, fault reactivation, and casing failure, would compromise the long-term productivity of the reservoir. To quantify the dynamic response of the reservoir and related risks, a 4D reservoir/geomechanics simulation was conducted for Keshen Reservoir by following an integrated work flow. The work started from systematic laboratory fracture-conductivity tests performed with fractured cores to measure conductivity vs. confining stress for both natural fractures and hydraulic fractures (with proppant placed in the fractures of the core samples). Natural-fracture modeling was conducted to generate a discrete-fracture network (DFN) to delineate spatial distribution of the natural-fracture system. In addition, hydraulic-fracture modeling was conducted to delineate the geometry of the hydraulic-fracture system for the stimulated wells. Then, a 3D geomechanical model was constructed by integrating geological, petrophysical, and geomechanical data, and both the DFN and hydraulic-fracture system were incorporated into the 3D geomechanical model. A 4D reservoir/geomechanics simulation was conducted through coupling with a reservoir simulator to predict variations of stress and strain of rock matrix as well as natural fractures and hydraulic fractures during field production. At each study-well location, a near-wellbore model was extracted from the full-field model, and casing and cement were installed to evaluate well integrity during production. The 4D reservoir/geomechanics simulation revealed that there would be a large reduction of conductivity for both natural fractures and hydraulic fractures, and some fractures with certain dip/dip azimuth will be reactivated during the course of field production. The induced-stress change will also compromise well integrity for those poorly cemented wellbores. The field-development plan must consider all these risks to ensure sustainable long-term production. The paper presents a 4D coupled geomechanics/reservoir-simulation study applied to a high-pressure/high-temperature (HP/HT) naturally fractured reservoir, which has rarely been published previously. The study adapted several new techniques to quantify the mechanical response of both natural fractures and hydraulic fractures, such as using laboratory tests to measure stress sensitivity of natural fractures, integrating DFN and hydraulic-fracture systems into 4D geomechanics simulation, and evaluating well integrity on both the reservoir scale and the near-wellbore scale.

scholarly journals The Effect of Hydraulic-Natural Fracture Networks on the Waterflooding Development in a Multilayer Tight Reservoir: Case Study

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Gang Hui ◽  
Shengnan Chen ◽  
Youjing Wang ◽  
Fei Gu
Keyword(s):  
Spatial Distribution ◽  
Natural Fracture ◽  
Hydraulic Fractures ◽  
Sand Layer ◽  
Natural Fractures ◽  
Fracture Networks ◽  
Tight Sandstone ◽  
Water Breakthrough ◽  
Sand Bodies

An integrated hydraulic fracturing followed by waterflooding was conducted in a heterogeneous sandstone formation in the Northern Shanxi Slop of Ordos Basin in Western China. Water breakthrough quickly occurred, and the underlying mechanism of water breakthrough has not been well understood. Such mechanism needs to be investigated comprehensively from the spatial connectivity of multilayer sand bodies and characterization of hydraulic-natural fracture networks. Here, an integrated approach is proposed to tap the remaining oil in the individual sand layer during the late-stage development of tight sandstone reservoirs. A case study is utilized to demonstrate the applicability of the integrated method. It is found that the six sand layers could be further divided within the target oil layers. These sand layers have a variety of physical and mechanical properties, leading to the asymmetric spatial distribution of hydraulic fractures after performing the integrated fracturing of whole oil layers. The spatial difference of sand bodies conforms to the features of the multiperiod superimposed channel in the sedimentary environment of fan delta front. The natural fractures were generated from the tectonic movement in the Mesozoic period with a dominant orientation of approximately NE 67°. The asymmetric hydraulic fractures propagated and connected with the preexisting natural fractures, forming the intricate natural-hydraulic fracture networks. The water breakthrough pattern in each sand layer is primarily ascribed to the spatial distribution of the hydraulic-natural fracture networks and sedimentary microfacies. The refracturing operations based on the remaining oil distribution in sand layers are proven to be effective in further developing the formation. The average oil production of related wells increased from 0.61 t/d to 2.18 t/d. This practical development strategy provides insights for further development of likewise heterogeneous tight sandstone reservoirs.

scholarly journals Effect of Complex Natural Fractures on Economic Well Spacing Optimization in Shale Gas Reservoir with Gas-Water Two-Phase Flow

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2853
Author(s):  
Cheng Chang ◽  
Yongming Li ◽  
Xiaoping Li ◽  
Chuxi Liu ◽  
Mauricio Fiallos-Torres ◽  
...  
Keyword(s):  
Shale Gas ◽  
Two Phase Flow ◽  
Natural Fracture ◽  
Hydraulic Fractures ◽  
Phase Flow ◽  
Natural Fractures ◽  
Gas Reservoir ◽  
Two Phase ◽  
Shale Gas Reservoir ◽  
Well Spacing

At present, investigation of the effects of natural fractures on optimal well spacing of shale gas reservoirs from an economic perspective has been lacking. Traditional frameworks of fracture characterization, such as local grid refinement, make it unfeasible and inaccurate to study these effects of high-density natural fractures with complex geometries on well spacing. In this study, the non-intrusive EDFM (embedded discrete fracture model) method was presented to characterize fractures fast and accurately. The non-intrusiveness of EDFM removed the necessity of accessing the codes behind reservoir simulators, which meant it could simply create associated keywords that would correspondingly modify these fracture properties in separate files without information regarding the source codes. By implementing this powerful technology, a field-scale shale gas reservoir model was set up, including two-phase flow. The effective properties of hydraulic fractures were determined from the history matching process, and the results were entered into the well spacing optimization workflow. Different scenarios of natural fracture (NF) distributions and well spacing were designed, and the final economic analysis for each case was explored based on simulated productions. As a result, one of the findings of this study was that optimal well spacing tended to increase if more natural fractures were presented in the reservoir.

scholarly journals Factors influencing gas well productivity in fractured tight sandstone reservoir

2021 ◽  
Author(s):  
Bin Zhao ◽  
Hui Zhang ◽  
Haiying Wang ◽  
Zhimin Wang
Keyword(s):  
Principal Stress ◽  
Maximum Principal Stress ◽  
Natural Fracture ◽  
Fracture Density ◽  
Tight Sandstone ◽  
Gas Well ◽  
Well Productivity ◽  
Factors Influencing ◽  
Sandstone Reservoir ◽  
Central Factors

AbstractThere are many factors which influence the absolute open flow potential (AOFP) of gas well. One of them is the angle between maximum principal stress direction and natural fracture strike in gas reservoir. In order to find out how the angle influences the AOFP of gas well. A lot of data related to gas well productivity of 14 wells located in gas reservoir T were collected and collated. Influential intensity of each factor on the AOFP before and after reservoir modification was investigated through grey relation analysis method. Results indicated that the AOFP of gas well before and after reservoir modification was governed by 10 factors. The five central factors influencing the initial AOFP are natural fracture density, porosity, permeability, elevation of geological top surface, and gas saturation, respectively. The five central factors influencing the AOFP of hydraulically fractured gas well are porosity, gas saturation, elevation of geological top surface, minimum principal stress, and permeability, respectively. Angle between maximum principal stress direction and natural fracture strike was not the central factor influencing gas well productivity. Reservoir modification can greatly improve gas well productivity in fractured tight sandstone reservoir. Natural fracture density was the strongest influencing factor of the initial AOFP. Minimum principal stress was one of the central factors influencing the AOFP of hydraulically fractured gas well. Research results can be used to guide well deployment and gas productivity investment projects of fractured tight sandstone reservoir.

scholarly journals A New Simulation Approach to Model Complex Fracture Networks in the Shale Formation Considering Gas Desorption

2016 ◽  
Author(s):  
Xinfang Ma
Keyword(s):  
Shale Gas ◽  
Horizontal Wells ◽  
Production Performance ◽  
Natural Fracture ◽  
Fracture System ◽  
Gas Reservoir ◽  
Fine Grid ◽  
Stimulated Reservoir Volume ◽  
Shale Gas Reservoir ◽  
Reservoir Volume

Hydraulic fracturing in shale gas reservoirs has usually resulted in complex fracture network. The results of micro-seismic monitoring showed that the nature and degree of fracture complexity must be clearly understood to optimize stimulation design and completion strategy. This is often called stimulated reservoir volume (SRV). In the oil & gas industry, stimulated reservoir volume has made the shale gas exploitation and development so successful, so it is a main technique in shale gas development. The successful exploitation and development of shale gas reservoir has mainly relied on some combined technologies such as horizontal drilling, multi-stage completions, innovative fracturing, and fracture mapping to engineer economic completions. Hydraulic fracturing with large volumes of proppant and fracturing fluids will not only create high conductivity primary fractures but also stimulate adjacent natural fractures. Fracture network forming around every hydraulic fracture yields a stimulated reservoir volume. A model of horizontal wells which was based on a shale gas reservoir after volume fracturing in China was established to analyze the effect of related parameters on the production of multi-fractured horizontal wells in this paper. The adsorbed gas in the shale gas reservoir is simulated by dissolved gas in the immobile oil. The key to simulate SRV is to accurately represent the hydraulic fractures and the induced complex natural fracture system. However, current numerical simulation methods, such as dual porosity modeling, discrete modeling, have the following limitations: 1) time-consuming to set up hydraulic and natural fracture system; 2) large computation time required. In this paper, the shape of the stimulated formation is described by an expanding ellipsoid. Simplified stimulated zones with higher permeability were used to model the hydraulic fracture and the induced complex natural fracture system. In other words, each primary fracture has an enhanced zone, namely SRV zone. This method saves much developing fine-grid time and computing time. Compared with the simulation results of fine-grid reference model, it has shown that this simplified model greatly decreases simulation time and provides accurate results. In order to analyze the impacts of related parameters on production, a series of simulation scenarios and corresponding production performance were designed. Optimal design and analyses of fracturing parameters and the formation parameters have been calculated in this model. Simulation results showed that the number of primary fractures, half length, SRV half-width and drop-down have great effects on the post-fracturing production. Formation anisotropies also control the production performance while the conductivity of the primary fractures and SRV permeability do not have much impact on production performance. The complexity of stimulated reservoir volume has strong effect on gas well productivity. Fracture number mainly affects the early time production performance. The increase of SRV width cannot enlarge the drainage area of the multi-fractured horizontal wells, but it can improve the recovery in its own drainage region. Permeability anisotropies have much effect on production rate, especially the late time production rate. The results prove that horizontal well with volume fracturing plays an irreplaceable role in the development of ultra-low permeability shale gas reservoir.

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