New Analytical Approach to Operational Assessment of Fractured Well Productivity with Variable Permeability

2021 ◽  
Author(s):  
Evgeniy Viktorovich Yudin ◽  
George Aleksandrovich Piotrovskiy ◽  
Maria Vladimirovna Petrova ◽  
Alexey Petrovich Roshchektaev ◽  
Nikita Vladislavovich Shtrobel
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Free Parameter ◽  
Numerical Solutions ◽  
Analytical Models ◽  
Productivity Index ◽  
Finite Conductivity ◽  
Well Productivity ◽  
Fracture Conductivity ◽  
Variable Permeability

Abstract Requirements of targeted optimization are imposed on the hydraulic fracturing operations carried out in the conditions of borderline economic efficiency of fields taking into account geological and technological features. Consequently, the development of new analytical tools foranalyzing and planning the productivity of fractured wells, taking into account the structuralfeatures of the productive reservoir and inhomogeneous distribution of the fracture conductivity, is becoming highly relevant. The paper proposes a new approach of assessing the vertical hydraulic fracture productivityin a rectangular reservoir in a pseudo-steady state, based on reservoir resistivity concept described in the papers of Meyer et al. However, there is a free parameter in the case of modeling the productivity of a hydraulic fracture by the concept. The parameter describes the distribution of the inflow along the plane of the fracture. This paper presents a systematic approach to determining of the parameter. The resulting model allows to conduct an assessment of the influence of various complications in the fracture on the productivity index. During the research a method of determining the free parameter was developed,it was based on the obtained dependence of the inflow distribution on the coordinate along the fracture of finite conductivity. The methodology allowed to refine existent analytical solution of the Meyer et al. model, which, in turn, allowed to assess the influence of different fracture damages in the hydraulic fracture on the productivity index of the well. The work includes the cases of the presence of fracture damages at the beginning and at the end of the fracture. A hydraulic fracture model was built for each of the types of damages, it was based on the developed method, and also the solution of dimensionless productivity ratio was received. The results of the obtained solution were confirmed by comparison with the numerical solutions of commercial simulators and analytical models available in the literature. The advantage of the methodology is the resulting formulas for well productivity are relatively simple, even for exotic cases ofvariable conductivity fractures. The approaches and algorithms described in the paper assume the calculation of the productivity of a hydraulic fracture with variable conductivity and the presence of other complicatingfactors.The methodology of the paper can be used for analysis and diagnosis problems with formation hydraulic fracturing. The efficiency of the calculations allows using the presented methodology to solve inverse problems of determining the efficiency of the hydraulic fracturing operation.

scholarly journals Productivity analysis for a horizontal well with multiple reorientation fractures in an anisotropic reservoir

2020 ◽  
Vol 75 ◽  
pp. 80
Author(s):  
Mingxian Wang ◽  
Zifei Fan ◽  
Lun Zhao ◽  
Guoqiang Xing ◽  
Wenqi Zhao ◽  
...  
Keyword(s):  
Horizontal Well ◽  
Productivity Index ◽  
Finite Conductivity ◽  
Productivity Analysis ◽  
Well Productivity ◽  
Fracture Conductivity ◽  
Fracture Angle ◽  
Fracture Spacing ◽  
Anisotropic Factor ◽  
Anisotropic Reservoir

Reorientation fractures may be formed in soft and shallow formations during fracturing stimulation and then affect well productivity. The principal focus of this study is on the productivity analysis for a horizontal well with multiple reorientation fractures in an anisotropic reservoir. Combining the nodal analysis technique and fracture-wing method, a semi-analytical model for a horizontal well with multiple finite-conductivity reorientation fractures was established to calculate its dimensionless productivity index and derivative for production evaluation. A classic case in the literature was selected to verify the accuracy of our semi-analytical solution and the verification indicates this new solution is reliable. Results show that for a fixed fracture configuration the dimensionless productivity index of the proposed model first goes up and then remains constant with the increase of fracture conductivity, and optimal fracture conductivity can be determined on derivative curves. Strong permeability anisotropy is a negative factor for well production and the productivity index gradually decreases with the increase of anisotropic factor. As principal fracture angle goes up, horizontal well’s productivity index increases correspondingly. However, the effect of reoriented fracture angle on the productivity index is not as strong as that of principal fracture angle. When reoriented fracture angle is smaller than principal fracture angle, reoriented factor should be as low as possible to achieve optimal productivity index. Meanwhile, well productivity index rises up with the increase of fracture number and fracture spacing, but the horizontal well has optimal reorientation fracture number and fracture spacing to get the economical productivity. Furthermore, the influence of the rotation of one central reorientation fracture on productivity index is weaker than that caused by the rotation of one external reorientation fracture. In addition, the asymmetrical distribution of one or more reorientation fractures slightly affects the productivity index when fracture conductivity is high enough.

Comparison of analytical models for hydraulic fracture conductivity

2019 ◽  
Vol 12 (15) ◽  
Author(s):  
Yuxuan Liu ◽  
Dilin Wen ◽  
Xin Wu ◽  
Jianchun Guo ◽  
Jiandong Wang
Keyword(s):  
Hydraulic Fracture ◽  
Analytical Models ◽  
Fracture Conductivity

Pressure Transient Analysis for a Finite-Conductivity Fractured Vertical Well Near a Leaky Fault in Anisotropic Linear Composite Reservoirs

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Junjie Ren ◽  
Yangyang Gao ◽  
Qiao Zheng ◽  
Delong Wang
Keyword(s):  
Numerical Solutions ◽  
Superposition Principle ◽  
Analytical Models ◽  
Finite Conductivity ◽  
Vertical Wells ◽  
Pressure Behavior ◽  
Linear Composite ◽  
Composite Models ◽  
Multiple Reservoir ◽  
Almost All

Abstract Geologic discontinuities usually exist in subsurface permeable formations, where multiple reservoir regions with distinct properties are separated by linear leaky faults. This kind of heterogeneous reservoir is usually called a linear composite reservoir. Although many analytical/semi-analytical linear composite models have been established to investigate the pressure behavior for linear composite reservoirs, almost all of these models were aimed at vertical wells without hydraulic fracturing and there are few analytical/semi-analytical models of fractured vertical wells in linear composite reservoirs. This paper first derives the Laplace-space point source solution for anisotropic linear composite systems separated by a partially communicating fault. Then, superposition principle and fracture discrete scheme are employed to acquire the semi-analytical solution for finite-conductivity fractured vertical (FCFV) wells in anisotropic linear composite reservoirs with a fault. The proposed solution is validated against numerical solutions under different reservoir scenarios. The characteristic of the pressure behavior for an FCFV well in anisotropic linear composite reservoirs with a fault is discussed in detail. The proposed model can be employed to obtain accurate pressure response with high computational efficiency. It is a good start to further develop analytical/semi-analytical models for other complex well types in an anisotropic linear composite reservoir with a fault.

Evaluation of Fracture Asymmetry of Finite-Conductivity Fractured Wells

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
Djebbar Tiab ◽  
Jing Lu ◽  
Hung Nguyen ◽  
Jalal Owayed
Keyword(s):  
Hydraulic Fracturing ◽  
Production Rate ◽  
Radial Flow ◽  
Asymmetry Factor ◽  
Hydraulic Fractures ◽  
Finite Conductivity ◽  
Asymmetry Ratio ◽  
Pressure Derivative ◽  
Fracture Conductivity ◽  
The Asymmetry

Nearly all commercial hydraulic fracture design models are based on the assumption that a single fracture is initiated and propagated identically and symmetrically about the wellbore, i.e., the fracture growth and proppant transport occurs symmetrically with respect to the well. However, asymmetrical fractures have been observed in hundreds of hydraulic fracturing treatments and reported to be a more realistic outcome of hydraulic fracturing. The asymmetry ratio (length of short fracture wing divided by length of long wing) influenced the production rate adversely. In the worst case, the production rate could be reduced to that of an unfractured well. Several authors observed asymmetrically propagated hydraulic fractures in which one wing could be ten times longer than the other. Most pressure transient analysis techniques of hydraulically fractured wells assume the fracture is symmetric about the well axis for the sake of simplicity in developing mathematical solution. This study extends the work by Rodriguez to evaluate fracture asymmetry of finite-conductivity fracture wells producing at a constant-rate. The analysis presented by Rodriguez only involves the slopes of the straight lines that characterize the bilinear, linear and radial flow from the conventional Cartesian and semilog plots of pressure drop versus time. This study also uses the Tiab’s direct synthesis (TDS) technique to analyze the linear and bilinear flow regimes in order to find the asymmetry factor of the fractured well. With the fracture conductivity estimated from the bilinear flow region, dimensionless fracture conductivity and the asymmetry ratio are calculated. A technique for estimating the fracture asymmetry ratio from a graph is presented. An equation relating the asymmetry ratio and dimensionless fracture conductivity is also presented. This equation assumes that the linear and/or bilinear flow regime is observed. However, using the TDS technique, the asymmetry ratio can be estimated even in the absence of bilinear or linear flow period. It is concluded that the relative position of the well in the fracture, i.e., the asymmetry condition, is an important consideration for the fracture characterization. A log-log plot of pressure derivative can be used to estimate the fracture asymmetry in a well intersected with a finite-conductivity asymmetric fracture. The analysis using pressure derivative plot does not necessarily require the radial flow period data to calculate the asymmetric factor.

scholarly journals Hydraulic Fracturing Designs For Low Permeability Gas Condensate Reservoirs Having Lean and Rich Condensate Compositions

2017 ◽  
Vol 3 (3) ◽  
pp. 9
Author(s):  
Karanthakarn Mekmok ◽  
Jirawat Chewaroungroaj
Keyword(s):  
Hydraulic Fracturing ◽  
Gas Condensate ◽  
Dew Point ◽  
Well Productivity ◽  
Fracture Conductivity ◽  
Gas Condensate Reservoirs ◽  
Point Pressure ◽  
Condensate Blockage ◽  
Dew Point Pressure ◽  
Saturation Profile

Gas condensate reservoirs have been challenging many researchers in petroleum industry for decades because of their complexities in flow behavior. After dew point pressure is reached, gas condensate will drop liquid out and increase liquid saturation near wellbore vicinity called condensate banking or condensate blockage. Hydraulic fracturing in horizontal direction has been proved to be a reliable method to mitigate condensate blockage and increase productivity of gas condensate well by means of pressure redistribution in the near wellbore vicinity. In this paper the parameters of dimensionless fracture conductivity and Stimulated Reservoir Volume (SRV) designs of lean and rich condensate compositions are studied. Well productivity and saturation profile of each design had been observed. The results from this study indicate that the higher dimensionless fracture conductivity gives the higher well productivity in every studied parameter in lean condensate composition. However, in rich condensate composition shows different trend of results because it has higher heavy ends (C7+) that drop into liquid easier once pressure falls below dew point pressure. The maximum number of fracture and fracture permeability can be recognized in the study of rich condensate. In the study of SRV indicates that number of fracture is superior to fracture width in both gas and condensate productivity. Moreover, performing hydraulic fracturing can decrease pressure drawdown, production time and liquid dropout which leads to the mitigation of condensate banking near wellbore that can be recognized in the study of condensate saturation profile.

Practical Applications of Water Hammer Analysis from Hydraulic Fracturing Treatments

2021 ◽  
Author(s):  
Nguyen Dung ◽  
Cramer David ◽  
Danielson Tom ◽  
Snyder Jon ◽  
Roussel Nico ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Decay Rate ◽  
Hydraulic Fracture ◽  
Screening Method ◽  
Water Hammer ◽  
Unconventional Reservoirs ◽  
Fluid Injection ◽  
Well Productivity ◽  
Flowing Fluid ◽  
Fracture Intensity

Abstract Water hammer is oscillatory pressure behavior in a wellbore resulting from the inertial effect of flowing fluid being subjected to an abrupt change in velocity. It is commonly observed at the end of large-scale hydraulic fracturing treatments after fluid injection rate is rapidly reduced or terminated. In this paper, factors affecting treatment-related water hammer behavior are disclosed, and field studies are introduced correlating water hammer characteristics to fracture intensity and well productivity. A simulator based on fundamental fluid-mechanics concepts was developed to model water hammer responses for various wellbore configurations and treatment characteristics. Insight from the modeling work was used to develop an optimal process of terminating fluid injection to obtain a consistent, identifiable oscillatory response for evaluating water hammer periodicity, decay rate, and oscillatory patterns. A completion database was engaged in a semi-automated process to evaluate numerous treatments. A data screening method was developed and implemented for enhancing interpretation reliability. Derived water hammer components were correlated to fracture intensity, well productivity and in certain cases, loss of treatment confinement to the intended treatment interval. Using the above process, thousands of hydraulic fracturing treatments were evaluated, and the results of that work are included in this study. The treatments were performed in wells based in Texas, South America, and Canada and completed in low permeability and unconventional reservoirs. The water hammer decay rate was determined to be a reliable indication of the system friction (friction in the wellbore and hydraulic fracture network) that drains energy from the water hammer pulse. In unconventional reservoirs characterized by small differences in the minimum and maximum horizontal stresses, high system friction correlated positively with fracture intensity/complexity and well performance. Results were constrained with instantaneous shut-in pressure (ISIP) and pressure falloff measurements to identify instances of direct communication with previously treated offset wellbores. The resulting analyses provided: – identification of enhanced-permeability intervals – indications of hydraulic fracture geometry – assessment of treatment modifications intended to enhance fracture complexity – identification of loss of treatment confinement to the intended interval – location of associated points of failure in the wellbore Topics covered in the paper include: Introduction  Joukowsky Equation  Period and Boundary Conditions Review of Prior Work on Water Hammer Analysis Shut-In Pressure Data, Analysis, and Model  Data collection frequency  Data issues and requirements  Water Hammer Analytical Method  Water Hammer Model Effects on Water hammer signature  Fluid properties  Step-down rate change and duration  Perforation friction Applications  Identification of Boundary Condition  Identification of Treatment Stage Isolation  Identification of Casing Failure Depth  Identification of Excess Period (Excess Length) Case Study – Water Hammer Data in an Unconventional Reservoir  Interpretation of frac geometry and friction in the fracture  Relationship to well productivity

State of the Art in Characterization of Frac Stage Geometry and Conductivity Using Pressure Leakoff

2021 ◽  
Author(s):  
Mohamed Ibrahim Mohamed ◽  
Erdal Ozkan
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Transient Analysis ◽  
State Of The Art ◽  
Low Cost ◽  
Pressure Data ◽  
Pressure Transient Analysis ◽  
Fracture Conductivity ◽  
Pressure Transient ◽  
Half Length

Abstract Pressure-transient analysis (PTA) is widely used in the industry to estimate fracture half-length, height, and skin due to hydraulic fracturing as well as reservoir parameters. PTA studies focus on pressure data from long shut-in periods and diagnostic fracture injection tests (DFITs), while analyzing the pressure data recorded during the hydraulic fracture treatment has been overlooked. This paper details the state-of-the-art in applying pressure transient analysis to better estimate hydraulic fracture conductivity and dimensions and improve treatment designs stage by stage. The initial portion of this paper describes the application of a novel and low-cost diagnostic method for post-fracture analysis. The bulk of the paper is dedicated to present case histories that illustrate the PTA of the recorded pressure data during treatment to obtain estimates of fracture dimensions and conductivity. The pressure recorded during each stage is processed to ensure the proper data quality and the pressure falloff at the end of the stage is filtered out. The pressure is then analyzed for multi-cluster, finite-conductivity fractures, to obtain the fracture half-length, conductivity, and leakoff. Calculated parameters from each stage are compared to provide insights into the hydraulic fracture design and confirm the adequacy of the treatment design along the well. The results from stage leakoff pressure analysis are very valuable in confirming relative fracture conductivity and providing a qualitative measure of fracture length and height. The total stimulated reservoir area (SRA) calculated using the proposed method yields comparable values to SRA obtained from buildup analysis. The information provided is as valuable and comparable as that from direct near-wellbore diagnostics, such as radioactive traces, temperature logging, real-time micro-seismic monitoring, and production logging. The paper proposes a novel, low-cost analytical PTA method for estimating fracture dimensions, skin, and leakoff coefficient. We illustrate – with several field cases – that conventional post-fracture techniques can be integrated with the stage by stage PTA analysis to provide not only a more consistent and systematic analysis but also a more accurate assessment of treatment effectiveness. The findings of this paper help improve the efficiency of multistage hydraulic fracturing stimulation of horizontal wells.

Influence of Finite Hydraulic-Fracture Conductivity on Unconventional Hydrocarbon Recovery With Horizontal Wells

SPE Journal ◽  
2017 ◽  
Vol 22 (06) ◽  
pp. 1790-1807 ◽  
Author(s):  
Deming Mao ◽  
David S. Miller ◽  
John M. Karanikas ◽  
Ed A. Lake ◽  
Phillip S. Fair ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Horizontal Wells ◽  
Normal Derivative ◽  
Unconventional Reservoirs ◽  
Analytical Models ◽  
Hydraulic Fractures ◽  
Multiple Fractures ◽  
Hydraulic Stimulation ◽  
Fracture Conductivity ◽  
Hydrocarbon Recovery

Summary The classic plots of dimensionless fracture conductivity (CfD) vs. equivalent wellbore radius or equivalent negative skin are useful for evaluating the performance of hydraulic fractures (HFs) in vertical wells targeting conventional reservoirs (Prats 1961; Cinco-Ley and Samaniego-V. 1981). The increase in well productivity after hydraulic stimulation can be estimated from the “after fracturing” effective wellbore radius or from the “after fracturing” equivalent negative skin. However, this earlier work does not apply to the case of horizontal wells with multiple fractures. A revision of the diagnostic plots is needed to account for the combination of the resulting radial-flow regime and the transient effect in unconventional reservoirs with ultralow permeability. This paper reviews and extends this earlier work with the objective of making it applicable in the case of horizontal wells with multiple fractures. It also demonstrates practical application of this new technique for fracture-design optimization for horizontal wells. The influence of finite fracture conductivity (FC) on the HF flow efficiency is evaluated through analytical models, and it is confirmed by a 3D transient numerical-reservoir simulation. This work demonstrates that a redefined dimensionless fracture conductivity for horizontal wells CfD,h = 4 is found to be optimal by use of the maximum of log-normal derivative (subject to economics) for HFs in horizontal wells, and this value of CfD,h can provide 50% of the fracture-flow efficiency and 90% of the estimated ultimate recovery (EUR) that would have been obtained from an infinitely conductive fracture for the same production period. This new master plot can provide guidance for hydraulic-fracturing design and its optimization for hydrocarbon recovery in unconventional reservoirs through hydraulic fracturing in horizontal wells.

Non-Darcy Flow in Wells With Finite-Conductivity Vertical Fractures

1982 ◽  
Vol 22 (05) ◽  
pp. 681-698 ◽  
Author(s):  
K.H. Guppy ◽  
H. Cinco-Ley ◽  
H.J. Ramey ◽  
F. Samaniego-V.
Keyword(s):  
Hydraulic Fracturing ◽  
Turbulent Flow ◽  
High Flow ◽  
Darcy Flow ◽  
Finite Conductivity ◽  
Gas Wells ◽  
Fracture Conductivity ◽  
Flow Rates ◽  
Vertical Fracture ◽  
Constant Rate

Abstract Several methods have been proposed in the literature for analyzing drawdown data for the determination of fracture conductivity of vertically fractured wells. These techniques have paved accurate, but in some cases the fracture conductivity calculated is much smaller than anticipated. This study shows that producing fractured wells at high flow rates will cause nondarcy effects in the fracture, resulting in a pessimistic fracture conductivity.Numerical and semianalytical models were developed to analyze the unsteady flow behavior of finite conductivity fractures producing at high flow rates. Two methods are presented for determining the true fracture conductivity when drawdown data are available at two different flow rates. The amount of turbulent effects also is quantified by the techniques. Examples are presented to illustrate the solution methods. Introduction The increasing use of hydraulic fracturing as a means of improving the productivity of oil and gas wells in low-permeability formations has resulted in many research efforts aimed at increasing fracturing capabilities as well as evaluating the characteristics of the fracture in the postfracturing period. With the advent of the massive postfracturing period. With the advent of the massive hydraulic fracturing (MHF) treatment in recent years, the need for new solutions for evaluating these systems has increased. The problem with the older solutions was the need for many assumptions to arrive at a simple solution. One of the more common assumptions made in these systems was the use of linear flow to describe the flow within the fracture. In gas wells with finite-conductivity fractures producing at high flow rates, the non-Darcy effect is created within the fracture. Hence, new solutions must be developed for these systems. The objective of this paper is to present a new semianalytical solution to this problem that can be applied both to the linear and to the nondarcy flow regimes within the fracture.Over the years. several methods have been developed to analyze postfracture data. Gringarien et al. first solved the fracture system analytically for three special cases: infinite-conductivity vertical fracture, uniform flux vertical fracture, and horizontal fracture. At that time, its application became quite useful. But since not all systems behaved in this manner, the need for further solutions was warranted. Cinco-L. et al. investigated the general case of finite-conductivity vertical fractures, which included the above solution. as well as fracture conductivities as low as 0.1. This research also led to the need to analyze short-time data to obtain unique solutions. Similar results were obtained by Agarwat et al., who presented a finite-difference solution to this problem, considering both the constant rate as well as the problem, considering both the constant rate as well as the constant pressure cases.One of the first papers written on the effects of non-Darcy flow in fractured systems was by Wattenbarger and Ramey. They investigated the effects of non-Darcy flow in the formation and concluded that these effects cannot be felt if the fracture is long or intermediate in size. They further concluded that the effects of turbulent flow within the fracture were more significant.Holditch and Morse investigated the effect of turbulent flow in a fracture and analyzed the transient behavior of specific conductivities (low, medium, and high), giving a qualitative approach to the solution. They stressed the need for greater detail on these solutions and showed that there was indeed a large reduction in the fracture conductivity when non-Darcy flow was included. Although Holditch and Morse gave a detailed descriptive insight into the flow regime problem, they did not develop any general methods for determining the actual conductivity of the fracture. SPEJ P. 681

Workflow to Optimize Cluster Spacing Design of Horizontal Multistage Fractured Well in Unconventional Source Rock

2021 ◽  
Author(s):  
Rabah Mesdour ◽  
Moemen Abdelrahman ◽  
Abdulbari Alhayaf
Keyword(s):  
Hydraulic Fracturing ◽  
Source Rock ◽  
Unconventional Reservoirs ◽  
Analytical Models ◽  
Sensitivity Analyses ◽  
Reservoir Modeling ◽  
Hydraulic Fractures ◽  
Reservoir Model ◽  
Well Productivity ◽  
Horizontal Drilling

Abstract Horizontal drilling and multistage hydraulic fracturing applied in unconventional reservoirs over the past decade to create a large fracture surface area to improve the well productivity. The combination of reservoir quality with perforation cluster spacing and fracture staging are keys to successful hydraulic fracturing treatment for horizontal wells. The objective of this work is to build and calibrate a dynamic model by integrating geologic, hydraulic fracture, and reservoir modeling to optimize the number of clusters and other completion parameters for a horizontal well drilled in the source rock reservoir using simulation and analytical models. The methodology adopted in this study covers the integration of geological, petrophysical, and production data analysis to evaluate reservoir and completion qualities and quantify the heterogeneity and the perforation clusters number required within a frac stage. Assuming all perforation clusters are uniformly distributed within a stage. The hydraulic planer fracture attributes assumed and the surface production measurement together with the production profile were used to calibrate the reservoir model. The properties of the Stimulated Reservoir Volume "SRV" were defined after the final calibration using reservoir model including hydraulic fractures. The calibrated reservoir model was used to carry out sensitivity analyses for cluster spacing optimization and other completion parameters considering the surface and reservoir constraints. An optimum cluster spacing was observed based on the Estimated Ultimate Recovery "EUR" of the subject well by reservoir properties. The final results based on 70% of perforation clusters contribution to production observed from PLT log, and the results of this study were implemented. Afterwards, another study has been undertaken to increasing the stimulation effectiveness and maximizing the number of perforation clusters contributing to productivity as an area for improvement to engineering the completion design. The methodology adopted in this study identifies the most important parameters of completion affecting well productivity for specific unconventional reservoirs. This study will help to engineer completion design, improve cluster efficiency, reduce cost and increase well EUR for the development phase.

Sign in / Sign up

Export Citation Format

Share Document