Pressure-Transient Analysis of Multiwing Fractures Connected to a Vertical Wellbore

SPE Journal ◽  
2014 ◽  
Vol 20 (02) ◽  
pp. 360-367 ◽  
Author(s):  
Luo Wanjing ◽  
Tang Changfu
Keyword(s):  
Flow Regime ◽  
Asymmetry Factor ◽  
Strong Interactions ◽  
Transient Pressure ◽  
High Fracture ◽  
Multiple Fractures ◽  
Pressure Derivative ◽  
Linear Flow ◽  
Type Curves ◽  
Vertical Well

Summary The principal focus of this work is on transient-pressure behaviors of multiwing fractures connected to a vertical wellbore. The vertical well is fractured with multiple-fracture wings with varied intersection angle, length, and asymmetry factor (AF). In the case of equally spaced fractures connected to a vertical wellbore, three flow regimes may be observed: bilinear-flow regime, formation linear flow, and pseudoradial-flow regime. With the increase of fracture numbers, the interaction of fractures becomes stronger and a “hump” occurs on the curves of pressure derivative for low and moderate fracture conductivities. For an anisotropic formation, the fracture may grow at a specific azimuth, and a fracture cluster develops. Because of the strong interactions among fracture clusters, the end of bilinear flow occurs earlier, and the formation linear flow will not be observed even for high fracture conductivities. In some extreme case in which a vertical well is intercepted with highly asymmetrically distributed fracture clusters, its transient performances of pressure and pressure-derivative curves may deviate from the conventional type curves totally. In addition, it is found that the complexity of multiple fractures near the wellbore can enhance the recovery of oil and gas.

scholarly journals Pressure Analysis for Volume Fracturing Vertical Well considering Low-Velocity Non-Darcy Flow and Stress Sensitivity

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Zhongwei Wu ◽  
Chuanzhi Cui ◽  
Japan Trivedi ◽  
Ning Ai ◽  
Wenhao Tang
Keyword(s):  
Flow Regime ◽  
Stress Sensitivity ◽  
Darcy Flow ◽  
Transition Flow ◽  
Low Velocity ◽  
Pressure Derivative ◽  
Threshold Pressure Gradient ◽  
Vertical Well ◽  
Dimensionless Pressure ◽  
Volume Fracturing

In general, there is stress sensitivity damage in tight reservoirs and fractures. Furthermore, the flow in tight reservoirs is the low-velocity non-Darcy flow. Currently, few researches of pressure analysis for volume fracturing vertical well are conducted simultaneously considering the low-velocity non-Darcy flow and stress sensitivity. In the paper, a novel flow model of a volume fractured vertical well is proposed and solved numerically. Firstly, the threshold pressure gradient, permeability modulus, and experimental data are, respectively, utilized to characterize the low-velocity non-Darcy flow, matrix stress sensitivity, and fracture stress sensitivity. Then, a two-region composite reservoir is established to simulate the vertical well with volume fracturing. After that, the logarithm meshing method is used to discrete the composite reservoir, and the flow model is solved by the method of finite difference and IMPES. Finally, the model verification is conducted, and the effects of the low-velocity non-Darcy flow and stress sensitivity on the pressure and pressure derivative are analyzed. The six flow regimes are identified by the dimensionless pressure and pressure derivative curve. They are, respectively, the fracture linear flow regime, early transition flow regime, radial flow regime, crossflow regime, advanced transition flow regime, and boundary controlling flow regime. The stress sensitivity and threshold pressure gradient have a great effect on the dimensionless pressure and pressure derivative. With the increase of reservoir stress sensitivity, the pressure and pressure derivative are upward at the advanced transition flow and boundary controlling regimes. However, the pressure and pressure derivative are downward at the advanced transition flow and boundary controlling regimes when the fracture sensitivity increases. An increase in the threshold pressure gradient results in a high dimensionless pressure and pressure derivative. This work reveals the effects of low-velocity non-Darcy flow and stress sensitivity on pressure and provides a more accurate reference for reservoir engineers in pressure analysis when developing a tight reservoir by using the volume fracturing vertical well.

scholarly journals Transient-Flow Modeling of Vertical Fractured Wells with Multiple Hydraulic Fractures in Stress-Sensitive Gas Reservoirs

2019 ◽  
Vol 9 (7) ◽  
pp. 1359 ◽  
Author(s):  
Ping Guo ◽  
Zhen Sun ◽  
Chao Peng ◽  
Hongfei Chen ◽  
Junjie Ren
Keyword(s):  
Hydraulic Fracture ◽  
Transient Flow ◽  
Superposition Principle ◽  
Pressure Profile ◽  
Stress Sensitivity ◽  
Hydraulic Fractures ◽  
Transient Pressure ◽  
Gas Reservoirs ◽  
Type Curves ◽  
Vertical Well

Massive hydraulic fracturing of vertical wells has been extensively employed in the development of low-permeability gas reservoirs. The existence of multiple hydraulic fractures along a vertical well makes the pressure profile around the vertical well complex. This paper studies the pressure dependence of permeability to develop a seepage model of vertical fractured wells with multiple hydraulic fractures. Both transformed pseudo-pressure and perturbation techniques have been employed to linearize the proposed model. The superposition principle and a hybrid analytical-numerical method were used to obtain the bottom-hole pseudo-pressure solution. Type curves for pseudo-pressure are presented and identified. The effects of the relevant parameters (such as dimensionless permeability modulus, fracture conductivity coefficient, hydraulic-fracture length, angle between the two adjacent hydraulic fractures, the difference of the hydraulic-fracture lengths, and hydraulic-fracture number) on the type curve and the error caused by neglecting the stress sensitivity are discussed in detail. The proposed work can enrich the understanding of the influence of the stress sensitivity on the performance of a vertical fractured well with multiple hydraulic fractures and can be used to more accurately interpret and forecast the transient pressure.

Performance Evaluation of a Horizontal Well With Multiple Fractures by Use of a Slab-Source Function

SPE Journal ◽  
2015 ◽  
Vol 20 (03) ◽  
pp. 652-662 ◽  
Author(s):  
Daoyong Yang ◽  
Feng Zhang ◽  
John A. Styles ◽  
Junmin Gao
Keyword(s):  
Horizontal Well ◽  
Source Function ◽  
Early Stage ◽  
Pressure Response ◽  
Multiple Fractures ◽  
Fracture Conductivity ◽  
Linear Flow ◽  
Type Curves ◽  
Semianalytical Method ◽  
Reservoir Simulator

Summary A novel slab-source function was formulated and successfully applied to accurately evaluate performance of a horizontal well with multiple fractures in a tight formation. More specifically, such a slab-source function in the Laplace domain has assigned a geometrical dimension to the source, whereas pressure response of a rectangular reservoir with closed outer boundaries can be determined. A semianalytical method is then applied to solve the newly formulated mathematical model by discretizing the fracture into small segments, each of which is treated as a slab source, assuming that there exists unsteady flow between the adjacent segments. The newly developed function was validated with numerical solution obtained from a reservoir simulator and then its application was extended to a field case. The pressure response together with its corresponding derivative type curves was reproduced to examine effects of number of stages, fracture conductivity, and fracture dimension under various penetration conditions. The fracture conductivity is found to mainly influence early-stage bilinear-/linear-flow regime, whereas a smaller conductivity will force more fluid to enter the toe of the fracture than its heel. The penetrating ratio will impose a significant impact on the pressure response at the early stage, forcing the bilinear/linear flow to become radial flow.

Performance Evaluation of A Horizontal Well with Multiple Fractures Using A Slab Source Function

2015 ◽  
Author(s):  
Daoyong Yang ◽  
Feng Zhang ◽  
John A. Styles ◽  
Junmin Gao
Keyword(s):  
Horizontal Well ◽  
Source Function ◽  
Early Stage ◽  
Pressure Response ◽  
Multiple Fractures ◽  
Fracture Conductivity ◽  
Linear Flow ◽  
Type Curves ◽  
Reservoir Simulator ◽  
Adjacent Segments

Abstract A novel slab source function has been formulated and successfully applied to accurately evaluate performance of a horizontal well with multiple fractures in a tight formation. A semi-analytical method is then applied to solve the newly formulated mathematical model by discretizing the fracture into small segments, each of which is treated as a slab source, assuming that there exists unsteady flow between the adjacent segments. The newly developed function has been validated with numerical solution obtained from a reservoir simulator and then extended its application to a field case. The pressure response together with its corresponding derivative type curves has been reproduced to examine effects of number of stages, fracture conductivity, and fracture dimension under various penetration conditions. The fracture conductivity is found to mainly influence early-stage bilinear/linear flow regime, while a smaller conductivity will force more fluid to enter the toe of the fracture than its heel. Penetrating ratio will impose a significant impact on the pressure response at the early stage, forcing the bilinear/linear flow to the radial flow.

The Effects of Reservoir Area Extent on the Performance of a Vertical Well in a Reservoir Subject to Bottom Water Drive

2015 ◽  
Vol 752-753 ◽  
pp. 790-795
Author(s):  
I. Eiroboyi ◽  
P.O. Obeta
Keyword(s):  
Steady State ◽  
Bottom Water ◽  
Maximum Pressure ◽  
Large Area ◽  
Pressure Derivative ◽  
Type Curves ◽  
Reservoir Area ◽  
Vertical Well ◽  
Flow Equations ◽  
Dimensionless Pressure

Reservoir performance can be understood from system type curves. The type curve gives vivid information about maximum pressure drops, magnitude of near wellbore effects, reservoir fluid and wellbore properties needed to ascertain the strength of available drive mechanism, maximum withdrawal rates and remaining fluid in real time. This paper investigates the effects of reservoir area extent on the performance of a reservoir, subject to active bottom water, when it is completed with a vertical well. Type curves of dimensionless pressures and dimensionless pressure derivatives were produced for various dimensionless values of area extent of the reservoir. These type curves were developed from solutions to flow equations using relevant source and Green’s functions. From the results, it can be observed that the larger the reservoir area extent, the larger the dimensionless pressure drop, the longer the time it takes to attain steady state. This is validated from the pressure derivative curve, which shows that reservoirs with large area extent are characterized by longer period of radial flow and subsequently delay in the attainment of steady state, thus prolonging the arrival of bottom water.

Effects of Non-Darcy Flow and Penetrating Ratio on Performance of Horizontal Wells With Multiple Fractures in a Tight Formation

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Feng Zhang ◽  
Daoyong Yang
Keyword(s):  
Mathematical Model ◽  
Pressure Drop ◽  
Flow Regime ◽  
Darcy Number ◽  
Pressure Response ◽  
Darcy Flow ◽  
Multiple Fractures ◽  
Linear Flow ◽  
Relative Minimum ◽  
Tight Formation

A novel slab source function has been formulated and successfully applied to examine effects of non-Darcy flow and penetrating ratio on performance of a horizontal well with multiple fractures in a tight formation. The Barree–Conway model is incorporated in the mathematical model to analyze non-Darcy flow behavior in the hydraulic fractures, while the pressure response under non-Darcy flow is determined by two dimensionless numbers (i.e., relative minimum permeability (kmr) and non-Darcy number (FND)). A semi-analytical method is then applied to solve the newly formulated mathematical model by discretizing the fracture into small segments. The newly developed function has been validated with numerical solution obtained from a reservoir simulator. Non-Darcy effect becomes more evident at a smaller relative minimum permeability (kmr < 0.05) and a larger non-Darcy number (FND > 10). The non-Darcy number is found to be more sensitive than the relative minimum permeability, resulting in a larger pressure drop even at a larger kmr. In addition, the non-Darcy flow is found to impose a significant impact on the early-stage bilinear/linear flow regime, resulting in an additional pressure drop that is similar to lowering the fracture conductivity. The pressure response can be classified into two categories by a penetrating ratio of 0.5. When the penetrating ratio is decreased, the early bilinear/linear flow regime occurs, followed by an early radial flow regime.

Type Curves Analysis for Asymmetrically Fractured Wells

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Lei Wang ◽  
Xiaodong Wang
Keyword(s):  
Asymmetry Factor ◽  
Fracture Conductivity ◽  
Linear Flow ◽  
Type Curves ◽  
Starting Time ◽  
Wellbore Storage ◽  
Constant Rate ◽  
Pressure Depletion ◽  
Storage Effects ◽  
New Type

In this paper, a new constant rate solution for asymmetrically fractured wells was proposed to analyze the effect of fracture asymmetry on type curves. Calculative results showed that for a small wellbore storage coefficient or for the low fracture conductivity, the effect of fracture asymmetry on early flow was very strong. The existence of the fracture asymmetry would cause bigger pressure depletion and make the starting time of linear flow occur earlier. Then, new type curves were established for different fracture asymmetry factor and different fracture conductivity. It was shown that a bigger fracture asymmetry factor and low fracture conductivity would prolong the time of wellbore storage effects. Therefore, to reduce wellbore storage effects, it was essential to keep higher fracture conductivity and fracture symmetry during the hydraulic fracturing design. Finally, a case example is performed to demonstrate the methodology of new type curves analysis and its validation for calculating important formation parameters.

Characteristics of Dimensionless Pressure Gradients and Derivatives of Horizontal and Vertical Wells Completed within Inclined Sealing Faults

2021 ◽  
Author(s):  
A V Ogbamikhumi ◽  
E S Adewole
Keyword(s):  
Pressure Drop ◽  
Horizontal Well ◽  
Superposition Principle ◽  
Early Time ◽  
Pressure Gradients ◽  
Vertical Wells ◽  
Pressure Derivative ◽  
Vertical Well ◽  
Dimensionless Pressure ◽  
Horizontal And Vertical Wells

Abstract Dimensionless pressure gradients and dimensionless pressure derivatives characteristics are studied for horizontal and vertical wells completed within a pair of no-flow boundaries inclined at a general angle ‘θ’. Infinite-acting flow solution of each well is utilized. Image distances as a result of the inclinations are considered. The superposition principle is further utilized to calculate total pressure drop due to flow from both object and image wells. Characteristic dimensionless flow pressure gradients and pressure derivatives for the wells are finally determined. The number of images formed due to the inclination and dimensionless well design affect the dimensionless pressure gradients and their derivatives. For n images, shortly after very early time for each inclination, dimensionless pressure gradients of 1.151(N+1)/LD for the horizontal well and 1.151(N+1) for vertical well are observed. Dimensionless pressure derivative of (N+1)/2LD are observed for central and off-centered horizontal well locations, and (N+1)/2 for vertical well are observed. Central well locations do not affect horizontal well productivity for all the inclinations. The magnitudes of dimensionless pressure drop and dimensionless pressure derivatives are maximum at the farthest image distances, and are unaffected by well stand-off for the horizontal well.

scholarly journals New Understanding of Transient Pressure Response in the Transition Zone of Oil-Water and Gas-Water Systems

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Wenbin Xu ◽  
Zhihui Liu ◽  
Jie Liu ◽  
Yongfei Yang
Keyword(s):  
Transition Zone ◽  
Outer Boundary ◽  
Water System ◽  
Pressure Response ◽  
Transient Pressure ◽  
Type Curves ◽  
Boundary Type ◽  
Study Results ◽  
Effective Mobility ◽  
Oil Water

Well test analysis requires a preselected model, which relies on the context input and the diagnostic result through the pressure logarithmic derivative curve. Transient pressure outer boundary response heavily impacts on the selection of such a model. Traditional boundary-type curves used for such diagnostic purpose are only suitable for single-phase flow in a homogeneous reservoir, while practical situations are often much more complicated. This is particularly true when transient pressure is derived during the field development phase, for example, from permanent down-hole gauge (PDG), where outer boundary condition such as an active aquifer with a transition zone above it plays a big role in dominating the late time pressure response. In this case, capillary pressure and the total mobility in the transition zone have significant effect on the pressure response. This effect is distinctly different for oil-water system and gas water system, which will result in the pressure logarithmic derivatives remarkably different from the traditional boundary-type curves. This paper presents study results derived through theoretical and numerical well testing approaches to solve this problem. The outcome of this study can help in understanding the reservoir behavior and guiding the management of mature field. According to the theoretical development by Thompson, a new approach was derived according to Darcy’s law, which shows that pressure response in the transition zone is a function of total effective mobility. For oil-water system, the total effective mobility increases with an increase in the radius of transition zone, while for gas-water system, the effect is opposite.

Sign in / Sign up

Export Citation Format

Share Document