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.

Optimizing the Number of Fractures in a Horizontal Well

SPE Journal ◽  
2019 ◽  
Vol 24 (03) ◽  
pp. 1364-1377 ◽  
Author(s):  
Vyacheslav Guk ◽  
Mikhail Tuzovskiy ◽  
Don Wolcott ◽  
Joe Mach
Keyword(s):  
Horizontal Well ◽  
Horizontal Wells ◽  
Optimal Number ◽  
Hydraulic Fractures ◽  
Single Fracture ◽  
Multiple Fracture ◽  
Multiple Fractures ◽  
Type Curves ◽  
Fracture Width ◽  
Technical Potential

Summary Horizontal wells with multiple hydraulic fractures have become a standard completion for the development of tight oil and gas reservoirs. Successful optimization of multiple-fracture design on horizontal wells began empirically in the Barnett Shale in the late 1990s (Steward 2013; Gertner 2013). More recently, research has focused on further improving fracturing performance by developing a model-derived optimum. Some researchers have focused on an economic optimum on the basis of multiple runs of an analytical or numerical model (Zhang et al. 2012; Saputelli et al. 2014). With such an approach, a new set of model runs is necessary to optimize the design each time the input parameters change significantly. Running multiple simulations for every optimization case might not always be practical. An alternative approach is to develop well-performance curves with dimensionless variables on the basis of the performance model. Such an approach was the basis for unified fracture design (UFD) for a single fracture in a vertical well (Economides et al. 2002). However, a similar systemized method to calculate the optimum for a horizontal well with multiple hydraulic fractures was missing. The objective of this study was to develop a rigorous and unified dimensionless optimization technique with type curves for the case of multiple transverse fractures in a horizontal well—an extension of UFD. The mathematical problem was solved in dimensionless variables. Multiple fractures include the proppant number (NP), penetration ratio (Ix), dimensionless conductivity (CfD), and aspect ratio (yeD) for each fracture, which is inversely proportional to the number of fractures. The direct boundary element (DBE) method was used to generate the dimensionless productivity index (JD) for a given range of these parameters (28,000 runs) for the pseudosteady-state case. Finally, total well JD was plotted as a function of the number of fractures for various NP. The effect of minimum fracture width was studied, and the optimization curves were adjusted for three cases of minimum fracture width. The provided dimensionless type curves can be used to identify the optimized number of fractures and their geometry for a given set of parameters, without running a more complicated numerical model multiple times. First, the proppant mass (and hence, NP) used for the fracture design can be selected on the basis of economic or other considerations. For this purpose, a relationship between total JD and NP, which accounts for the minimum fracture width requirement, was provided. Then, the optimal number of fractures can be calculated for a given NP using the generated type curves with minimum width constraints. The following observations were made during the study on the basis of the performed runs: For a given volume or proppant, NP, total JD for multiple fractures increases to an asymptote as the number of fractures increases. This asymptote represents a technical potential for multiple fractures and for high proppant numbers (NP≥100), with a technical potential of 3πNP. Below this asymptote, the more fractures that are created for a fixed NP, the larger the JD. In practice, minimum fracture width constrains the fracture geometry, and therefore maximum JD. For the case when 20/40 sand is used for multiple hydraulic fracturing of a 0.01-md formation with square total area, the optimal number of factures is approximately NP25. Application of horizontal drilling technology with multiple fractures assumes the availability of high proppant numbers. It was shown mathematically that the alternative low proppant numbers (NP≤20 for the previous case) are impractical for multiple fractures, because total JD cannot be significantly higher than JD for an optimized single fracture in the same area. This means that low formation permeability and/or high proppant volumes are needed for multiple fracture treatments.

scholarly journals A Novel Radial-Composite Model of Pressure Transient Analysis for Multistage Fracturing Horizontal Wells with Stimulated Reservoir Volume

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Yunpeng Hu ◽  
Xiaoling Zhang ◽  
Ziyun Cheng ◽  
Wei Ding ◽  
Liangchao Qu ◽  
...  
Keyword(s):  
Horizontal Well ◽  
Storage Capacity ◽  
Radial Flow ◽  
Horizontal Wells ◽  
Outer Zone ◽  
Middle Zone ◽  
Linear Flow ◽  
Type Curves ◽  
Stimulated Reservoir Volume ◽  
Reservoir Volume

In the process of stimulated reservoir volume of tight reservoir, horizontal well can form three zones, the inner zone is multistage fracturing zone, the middle zone is skin damage zone, and the outer zone is undamaged zone. In this paper, a transient well test analysis model of multistage fracturing horizontal well in three area composite reservoir is proposed. Based on Laplace transformation, point source integration, and superposition principle, the infinite conductivity multifracture model of three area composite reservoir is obtained. The linear equations of finite conductivity multifracture in Laplace space are established by using the equal conditions of flow and pressure at the fracture wall. Gauss-Newton iteration method and Stehfest number are used to obtain the solution of wellbore pressure. The accuracy of the results is verified by numerical simulation. Then, the flow characteristics of multistage fracturing horizontal wells in three area composite reservoirs are analyzed by type curves. The flow is divided into ten stages, which are the bilinear flow, the linear flow, the first radial flow stage, the inner zone linear flow, the inner zone radial flow, the middle zone linear flow, the middle zone radial flow, the outer zone linear flow, the outer zone radial flow, and the boundary dominated flow. The pressure derivative curves show different characteristics in different flow stages. The influences of fracture conductivity, fracture spacing, radius ratio of the middle zone to inner zone, radius ratio of the outer zone to the middle zone, permeability ratio of inner zone to the middle zone, permeability ratio of inner zone to outer zone, storage capacity ratio of inner zone to the middle zone, and storage capacity ratio of inner zone to outer zone on type curves are analyzed. Finally, the application and reliability of the proposed model are verified by a case example.

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.

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.

Improving Proppant Placement Success in Horizontal Wells in Layered Reservoirs in the Sultanate of Oman

2021 ◽  
Author(s):  
Andrew Boucher ◽  
Josef Shaoul ◽  
Inna Tkachuk ◽  
Mohammed Rashdi ◽  
Khalfan Bahri ◽  
...  
Keyword(s):  
Horizontal Well ◽  
Complex Geometry ◽  
Horizontal Wells ◽  
Vertical Position ◽  
Sultanate Of Oman ◽  
Vertical Wells ◽  
Multiple Fractures ◽  
Initiation Point ◽  
Interval Selection ◽  
Geological Units

Abstract A gas condensate field in the Sultanate of Oman has been developed since 1999 with vertical wells, with multiple fractures targeting different geological units. There were always issues with premature screenouts, especially when 16/30 or 12/20 proppant were used. The problems placing proppant were mainly in the upper two units, which have the lowest permeability and the most heterogeneous lithology, with alternating sand and shaly layers between the thick competent heterolith layers. Since 2015, a horizontal well pilot has been under way to determine if horizontal wells could be used for infill drilling, focusing on the least depleted units at the top of the reservoir. The horizontal wells have been plagued with problems of high fracturing pressures, low injectivity and premature screenouts. This paper describes a comprehensive analysis performed to understand the reasons for these difficulties and to determine how to improve the perforation interval selection criteria and treatment approach to minimize these problems in future horizontal wells. The method for improving the success rate of propped fracturing was based on analyzing all treatments performed in the first seven horizontal wells, and categorizing their proppant placement behavior into one of three categories (easy, difficult, impossible) based on injectivity, net pressure trend, proppant pumped and screenout occurrence. The stages in all three categories were then compared with relevant parameters, until a relationship was found that could explain both the successful and unsuccessful treatments. Treatments from offset vertical wells performed in the same geological units were re-analyzed, and used to better understand the behavior seen in the horizontal wells. The first observation was that proppant placement challenges and associated fracturing behavior were also seen in vertical wells in the two uppermost units, although to a much lesser extent. A strong correlation was found in the horizontal well fractures between the problems and the location of the perforated interval vertically within this heterogeneous reservoir. In order to place proppant successfully, it was necessary to initiate the fracture in a clean sand layer with sufficient vertical distance (TVT) to the heterolith (barrier) layers above and below the initiation point. The thickness of the heterolith layers was also important. Without sufficient "room" to grow vertically from where it initiates, the fracture appears to generate complex geometry, including horizontal fracture components that result in high fracturing pressures, large tortuosity friction, limited height growth and even poroelastic stress increase. This study has resulted in a better understanding of mechanisms that can make hydraulic fracturing more difficult in a horizontal well than a vertical well in a laminated heterogeneous low permeability reservoir. The guidelines given on how to select perforated intervals based on vertical position in the reservoir, rather than their position along the horizontal well, is a different approach than what is commonly used for horizontal well perforation interval selection.

Sign in / Sign up

Export Citation Format

Share Document