Is That Interference? A Work Flow for Identifying and Analyzing Communication Through Hydraulic Fractures in a Multiwell Pad

SPE Journal ◽  
2016 ◽  
Vol 21 (05) ◽  
pp. 1554-1566 ◽  
Author(s):  
A.. Awada ◽  
M.. Santo ◽  
D.. Lougheed ◽  
D.. Xu ◽  
C.. Virues
Keyword(s):  
Numerical Models ◽  
Work Flow ◽  
Hydraulic Fractures ◽  
Use Of Data ◽  
Well Spacing ◽  
Production Scheme ◽  
Fracture Fluid ◽  
Fluid Production ◽  
Horn River Basin ◽  
Rigorous Procedure

Summary The topic of interwell communication in unconventional reservoirs has received significant attention because it has direct implications for well-spacing considerations. However, it has been the observation of the authors that interference is often inferred without direct evidence of its occurrence, or without an understanding of the various mechanisms of interference. Some common discussions on interference among engineers refer to fracture “hits” and fracture-fluid production that suddenly appears at offset producing wells. These are indications of communication, but do not necessarily imply that a strong connection will be maintained throughout the life of the wells. This paper presents a rigorous procedure for correctly identifying interference by use of data acquired during a typical multiwell-pad-production scheme. First, the various mechanisms of interference are defined. Next, analytical simulations are run to reveal the expected behavior for interference through fractures and reservoir matrix. Data provided from an eight-well pad in the Horn River basin are then scoured, revealing evidence of interference between at least two wells. Through this exercise, a procedure is developed for identifying interference by searching for changes in buildup trends while wells are staggered on/off production. Finally, the data are history matched with numerical models to confirm the interference mechanism. The procedure in this paper is designed to help production analysts diagnose interference and avoid common pitfalls. The work flow is generalized and can be applied to other multiwell-pad completions.

Modelling Thousands of Fractures Using Analytic Elements

2021 ◽  
Author(s):  
Erik Toller ◽  
Otto Strack
Keyword(s):  
Exact Solution ◽  
Plane Strain ◽  
Numerical Models ◽  
Element Model ◽  
Global Scale ◽  
Hydraulic Fractures ◽  
Infinite Domain ◽  
Novel Approach ◽  
Analytic Elements ◽  
Kolosov Functions

<p>Understanding and modelling hydraulic fractures and fracture networks have a fundamental role in mapping the mechanical behaviour of rocks. A problem arises in the discontinuous behaviour of the fractures and how to accurately and efficiently model this. We present a novel approach for modelling many cracks randomly using analytic elements placed under plane strain conditions in an elastic medium. The analytic elements allow us to model the assembly computationally efficiently and up to machine precision. The crack element is the first step in the development of a model suitable for investigating the effect of fissures on tunnels in rock. The model can be used to validate numerical models and more.The solution for a single hydraulic pressurized crack in an infinite domain in plane strain was initially developed by Griffith (1921). We demonstrate that it is possible, by using series expansions in terms of complex variables, based on the Muskhelisvili-Kolosov functions, to generalize this solution to the case of an assembly of non-intersecting pressurized cracks. The solution consists of infinite series for each element Strack & Toller (2020). The expressions for the displacements and stress tensor components approach the exact solution, as the number of terms in the series approaches infinity.We present the case where two cracks approach each other orthogonally to less than 1/2000th of the cracks length. We show the effect of increasing the number of terms in the expansion and how this influences the precision, demonstrating that the result approaches the exact solution. We also present a case with 10,000 cracks; the coefficients are determined using an iterative solver. By using analytic elements, we can both present the corresponding stress and deformations field for the global scale and for small scales in the close proximity of individual cracks.ReferencesGriffith, A. A. (1921). The phenomena of rupture and flow in solids. Philosophical Transactions of the Royal Society of London. Series A, Containing Papers of a Mathematical or Physical Character, 221(582-593):163–198.Strack, O. D. L. and Toller, E. A. L. (2020). An analytic element model for highly fractured elastic media, manuscript submitted for publication in International Journal for Numerical and Analytical Methods in Geomechanics.</p>

Adaptive finite element–discrete element analysis for stratal movement and microseismic behaviours induced by multistage propagation of three-dimensional multiple hydraulic fractures

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yongliang Wang
Keyword(s):  
Finite Element ◽  
Numerical Models ◽  
Three Dimensional ◽  
Fracture Propagation ◽  
Discrete Element ◽  
Hydraulic Fractures ◽  
Adaptive Finite Element ◽  
Fracture Networks ◽  
Content Type ◽  
Microseismic Events

Purpose Optimized three-dimensional (3D) fracture networks are crucial for multistage hydrofracturing. To better understand the mechanisms controlling potential disasters as well as to predict them in 3D multistage hydrofracturing, some governing factors, such as fluid injection-induced stratal movement, compression between multiple hydraulic fractures, fracturing fluid flow, fracturing-induced microseismic damaged and contact slip events, must be properly simulated via numerical models. This study aims to analyze the stratal movement and microseismic behaviours induced by multistage propagation of 3D multiple hydraulic fractures. Design/methodology/approach Adaptive finite element–discrete element method was used to overcome the limitations of conventional finite element methods in simulating 3D fracture propagation. This new approach uses a local remeshing and coarsening strategy to ensure the accuracy of solutions, reliability of fracture propagation path and computational efficiency. Engineering-scale numerical models were proposed that account for the hydro-mechanical coupling and fracturing fluid leak-off, to simulate multistage propagation of 3D multiple hydraulic fractures, by which the evolution of the displacement, porosity and fracture fields, as well as the fracturing-induced microseismic events were computed. Findings Stratal movement and compression between 3D multiple hydraulic fractures intensify with increasing proximity to the propagating fractures. When the perforation cluster spaces are very narrow, alternate fracturing can improve fracturing effects over those achieved via sequential or simultaneous fracturing. Furthermore, the number and magnitude of microseismic events are directly proportional to the stratal movement and compression induced by multistage propagation of fracturing fracture networks. Originality/value Microseismic events induced by multistage propagation of 3D multiple hydraulic fractures and perforation cluster spaces and fracturing scenarios that impact the deformation and compression among fractures in porous rock matrices are well predicted and analyzed.

scholarly journals Numerical Investigation of Injection-Induced Fracture Propagation in Brittle Rocks with Two Injection Wells by a Modified Fluid-Mechanical Coupling Model

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4718
Author(s):  
Song Wang ◽  
Jian Zhou ◽  
Luqing Zhang ◽  
Zhenhua Han
Keyword(s):  
Fracture Propagation ◽  
In Situ Stress ◽  
Hydraulic Fractures ◽  
Fracture Networks ◽  
Breakdown Pressure ◽  
Injection Wells ◽  
Mechanical Coupling ◽  
Stress Shadow ◽  
Well Spacing

Hydraulic fracturing is a key technical means for stimulating tight and low permeability reservoirs to improve the production, which is widely employed in the development of unconventional energy resources, including shale gas, shale oil, gas hydrate, and dry hot rock. Although significant progress has been made in the simulation of fracturing a single well using two-dimensional Particle Flow Code (PFC2D), the understanding of the multi-well hydraulic fracturing characteristics is still limited. Exploring the mechanisms of fluid-driven fracture initiation, propagation and interaction under multi-well fracturing conditions is of great theoretical significance for creating complex fracture networks in the reservoir. In this study, a series of two-well fracturing simulations by a modified fluid-mechanical coupling algorithm were conducted to systematically investigate the effects of injection sequence and well spacing on breakdown pressure, fracture propagation and stress shadow. The results show that both injection sequence and well spacing make little difference on breakdown pressure but have huge impacts on fracture propagation pressure. Especially under hydrostatic pressure conditions, simultaneous injection and small well spacing increase the pore pressure between two injection wells and reduce the effective stress of rock to achieve lower fracture propagation pressure. The injection sequence can change the propagation direction of hydraulic fractures. When the in-situ stress is hydrostatic pressure, simultaneous injection compels the fractures to deflect and tend to propagate horizontally, which promotes the formation of complex fracture networks between two injection wells. When the maximum in-situ stress is in the horizontal direction, asynchronous injection is more conducive to the parallel propagation of multiple hydraulic fractures. Nevertheless, excessively small or large well spacing reduces the number of fracture branches in fracture networks. In addition, the stress shadow effect is found to be sensitive to both injection sequence and well spacing.

Grid-Sensitivity Analysis and Comparison Between Unstructured Perpendicular Bisector and Structured Tartan/Local-Grid-Refinement Grids for Hydraulically Fractured Horizontal Wells in Eagle Ford Formation With Complicated Natural Fractures

SPE Journal ◽  
2016 ◽  
Vol 21 (06) ◽  
pp. 2260-2275 ◽  
Author(s):  
Jianlei Sun ◽  
David Schechter ◽  
Chung-Kan Huang
Keyword(s):  
Horizontal Wells ◽  
Work Flow ◽  
Hydraulic Fractures ◽  
Grid Refinement ◽  
Fracture Networks ◽  
Structured Grids ◽  
Local Grid Refinement ◽  
Production Behavior ◽  
Local Grid ◽  
Fractured Horizontal Wells

Summary In the context of modeling fractured horizontal wells, unstructured grids have been applied to generate simulation meshes for complex fracture networks. It is necessary to investigate how to choose an unstructured mesh to accurately simulate production performance. In this paper, a new unstructured gridding and discretization work flow is proposed to handle nonorthogonal and low-angle intersections of extensively clustered fractures with nonuniform apertures. The work flow is then validated with two models in terms of production behavior and central-processing-unit (CPU) performance: a synthetic model with one horizontal well and orthogonal intersected hydraulic fractures built by tartan grid, and a field-scale local-grid-refinement (LGR) model with three horizontal wells and irregular hydraulic fractures in a slightly dipping reservoir created by a commercial software plug-in. Good-quality matches are obtained between unstructured and structured grids in both pressure and production behavior. Sensitivity analysis of the meshing parameters suggests that refinement in the vicinity of fractures has improved both early and late production of a well, whereas background density has a dominant effect on the late production. Background-grid type and orientation have less influence as long as they have the same grid density. Fewer cells can be achieved by increasing reservoir-background size and size-progression ratio, replacing unstructured-background grids with structured grids, and reducing the complexity of the fracture networks without loss of the accuracy, resulting in improved CPU performance. This study applies unstructured grids to simulate multiple horizontal wells with complicated fracture networks, and provides detailed comparisons between unstructured and structured grids. Most importantly, it resolves the question regarding how to choose an appropriate mesh to yield both accurate results and high-quality CPU performance.

scholarly journals Adaptive Finite Element-Discrete Element Analysis for Microseismic Modelling of Hydraulic Fracture Propagation of Perforation in Horizontal Well considering Pre-Existing Fractures

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Yongliang Wang ◽  
Yang Ju ◽  
Yongming Yang
Keyword(s):  
Finite Element ◽  
Hydraulic Fracture ◽  
Horizontal Well ◽  
Numerical Models ◽  
Fracture Propagation ◽  
Discrete Element ◽  
Hydraulic Fractures ◽  
Adaptive Finite Element ◽  
Naturally Fractured ◽  
Hydraulic Fracture Propagation

Hydrofracturing technology of perforated horizontal well has been widely used to stimulate the tight hydrocarbon reservoirs for gas production. To predict the hydraulic fracture propagation, the microseismicity can be used to infer hydraulic fractures state; by the effective numerical methods, microseismic events can be addressed from changes of the computed stresses. In numerical models, due to the challenges in accurately representing the complex structure of naturally fractured reservoir, the interaction between hydraulic and pre-existing fractures has not yet been considered and handled satisfactorily. To overcome these challenges, the adaptive finite element-discrete element method is used to refine mesh, effectively identify the fractures propagation, and investigate microseismic modelling. Numerical models are composed of hydraulic fractures, pre-existing fractures, and microscale pores, and the seepage analysis based on the Darcy’s law is used to determine fluid flow; then moment tensors in microseismicity are computed based on the computed stresses. Unfractured and naturally fractured models are compared to assess the influences of pre-existing fractures on hydrofracturing. The damaged and contact slip events were detected by the magnitudes, B-values, Hudson source type plots, and focal spheres.

Proxy-Based Assisted History Matching and Well-Spacing Optimization in Shale Gas Field

2021 ◽  
Vol 73 (04) ◽  
pp. 56-57
Author(s):  
Chris Carpenter
Keyword(s):  
Shale Gas ◽  
History Matching ◽  
Work Flow ◽  
University Of Texas ◽  
Matrix Permeability ◽  
Reservoir Volume ◽  
Well Spacing ◽  
Assisted History Matching ◽  
The University ◽  
Half Length

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 200466, “Proxy-Based Assisted History Matching and Well-Spacing Optimization in Shale Gas Development of a Real Field Case,” by Chuxi Liu, The University of Texas at Austin; Wei Yu, Sim Tech and The University of Texas at Austin; and Cheng Chang, PetroChina, et al., prepared for the 2020 SPE Improved Oil Recovery Conference, originally scheduled to be held in Tulsa, 18–22 April. The paper has not been peer reviewed. A robust, reliable work flow for well-spacing optimization in a shale reservoir development incorporating various types of uncertainties and detailed economics analysis is necessary for achieving sustainable unconventional production. In the complete paper, the authors describe a novel well-spacing-optimization work flow based on the results of assisted history matching and apply it to a real shale gas well, incorporating uncertainty parameters such as matrix permeability, matrix porosity, fracture half-length, fracture height, fracture width, fracture conductivity, and fracture water saturation. Introduction The work of well-spacing optimization is significant because it will subsequently dominate the planning of the drilling job and completion job and ultimately will affect recovery efficiency. The purpose of well-spacing optimization serves to maximize either capital revenue or ultimate recovery. The greatest challenge for well-spacing optimization is how to interpret the uncertainties associated with unconventional reservoirs. Stimulated reservoir volume and external reservoir volume, effective fracture half-length vs. propped half-length, matrix permeability, and complex structural geology are examples of such challenges. Therefore, developing an efficient and trustworthy work flow for optimizing well spacing in any shale reservoir is critical. Previous work on unconventional shale well-spacing optimization includes operator data analysis and numerical and analytical simulation. However, almost all previous studies ignored the effects of uncertainties. In addition, most studies require input information regarding the reservoir of interest. One method to obtain such information is to history match the production data, and a few history-matching methods have been explored and analyzed. Nevertheless, traditional history-matching methods could not overcome the problem of high-dimensional uncertainty space, as is commonly seen in unconventional development. Because of this, more- stochastic approaches have been developed and applied. These methods use the concept of proxy to minimize simulation runs and are also able to obtain as many, or more, history-matching realizations. Furthermore, Markov-chain Monte Carlo (MCMC) algorithms usually are coupled with the proxy model in assisted history matching. This method could be helpful in finding the complex posterior distributions of multiple uncertainty variables with ease.

Insights from pressure transients at observation wells near hydraulically fractured wells in a domestic shale play

2016 ◽  
Vol 4 (4) ◽  
pp. T567-T576 ◽  
Author(s):  
Chris Griffith ◽  
Mark McClure
Keyword(s):  
Principal Stress ◽  
Volatile Oil ◽  
Hydraulic Fractures ◽  
Minimum Principal Stress ◽  
Production Wells ◽  
Fluid Production ◽  
Pressure Changes ◽  
Observation Wells ◽  
The Relationship

We integrate microseismic data and pressure measurements at far-field observation wells to characterize the relationship between deformation and fluid flow during hydraulic fracturing and production in four horizontal wells in an unconventional shale play. The microseismicity qualitatively delineated, where injection fluid traveled during stimulation. However, there was one clear example of the Kaiser effect, in which a strong pressure signal propagated aseismically over hundreds of feet through fractures that had recently been stimulated around a neighboring well. Analysis suggested that poroelastic pressure changes caused by fracture deformation were minimal because of the high compressibility of the volatile oil formation fluid. Therefore, the pressure changes at the observations wells were likely caused by flow of the injection fluid. Based on this hypothesis, the pressure signals in the observation wells were roughly categorized based on whether the pressure response exceeded the magnitude of the minimum principal stress. The relationship between pressure and the minimum principal stress can be used to identify whether fluid traveled through newly forming hydraulic fractures or through stimulated natural fractures. However, the interpretation was significantly complicated by uncertainty in the magnitude of the stress caused by the prior depletion of the observation wells. In some observation wells, the pressure entered a gradual decline over time, indicating that significant long-term fluid production occurred in the neighborhood of the wellbore. But in the more distant observation wells and in depth intervals more vertically separated from the production wells, long-term depletion was not observed, indicating that significant reservoir depletion did not occur. These pressure gauges were sharply pressurized during stimulation, which implies that injection fluid reached these wells during fracturing, but proppant was not transported to the wells and the unpropped fractures subsequently closed and lost their conductivity.

scholarly journals Shallow Formation Hydrofracture Mapping Experiment

1978 ◽  
Vol 100 (1) ◽  
pp. 24-27
Author(s):  
L. J. Keck ◽  
C. L. Schuster
Keyword(s):  
Diagnostic Techniques ◽  
Small Scale ◽  
Hydraulic Fractures ◽  
Tight Gas ◽  
Gas Reservoirs ◽  
Model Calculations ◽  
Gas Recovery ◽  
Electrical Potentials ◽  
Fracture Fluid ◽  
Production Company

Geophysical diagnostic techniques are being developed to characterize the massive hydraulic fractures that are being utilized for the enhanced gas recovery from the Western tight gas reservoirs. Sandia Laboratories is developing a system based on the measurement of surface electrical potentials. Model calculations indicate that the electrical potentials produced by direct electrical excitation of the fracture well and the fracture fluid can be used to determine the direction and asymmetry of a massive fracture. A small scale, shallow formation hydrofracture experiment was conducted by the AMOCO Production Company in an attempt to better correlate theoretical and experimental data.

Forecasting the propagation paths of fluid-driven fractures, particularly dikes and inclined sheets

2020 ◽  
Author(s):  
Agust Gudmundsson ◽  
Kyriaki Drymoni ◽  
Mohsen Bazargan ◽  
Kayode Adeoye-Akinde
Keyword(s):  
Numerical Models ◽  
Volcanic Eruptions ◽  
Pyroclastic Flows ◽  
Propagation Path ◽  
Normal Faults ◽  
Hydraulic Fractures ◽  
Pure Mode ◽  
Field Observations ◽  
Least Action ◽  
Propagation Paths

<p>It is of great importance in many fields to be able to forecast the likely propagation paths of fluid-driven factures. These include mineral veins, human-made hydraulic fractures, and dikes/inclined sheets. The physical principles that control the propagation of all fluid-driven fractures are the same. Here the focus is on dikes and inclined sheets where the selected path determines whether, where, and when a particular dike/sheet reaches the surface to erupt. Here we provide analytical and numerical models on dike/sheet paths in crustal segments (including volcanoes) that include layers of various types (lava flows, pyroclastic flows, tuff layers, soil layers, etc) as well as mechanically weak contacts and faults. The modelling results are then compared with, and tested on, actual data of two types. (a) Seismic data on the paths of dikes/sheets as well as human-made hydraulic fractures, and (b) field data on the actual propagation paths of dikes/sheets in layered and faulted rocks</p><p>The numerical results show that, particularly in stratovolcanoes, the paths are likely to be complex with common deflections along layer contacts, in agreement with field observations.  Also, some dikes/sheets may use existing faults as parts of their paths, primarily steeply dipping and recently active normal faults. The propagation path is thus not entirely in pure mode I but rather partly in a mixed mode. The energy required to propagate the dike/sheet is mainly the surface energy needed to rupture the rock, to form two new surfaces and move them apart as the fracture propagates. The energy available to drive the fracture is the stored elastic energy in the hosting crustal segment.</p><p>From its point of initiation in the magma-chamber roof, a dike/sheet can, theoretically, select any one of an infinite number of paths to follow to its point of arrest or eruption. It is shown that the eventual path selected is the one of least action, that is, the path along which the time integral of the difference between the kinetic and potential energies is an extremum (normally a minimum) relative to all other possible paths with the same endpoints. If the kinetic energy is omitted, and there are no constraints, then least action becomes the minimum potential energy, which was postulated as a basis for understanding dike propagation by Gudmundsson (1986). Here it is shown how this theoretical framework can help us make reliable forecasts of dike/sheet paths and associated volcanic eruptions.</p><p>Gudmundsson, A., 1986. Formation of dykes, feeder-dykes, and the intrusion of dykes from magma chambers. Bulletin of Volcanology, 47, 537-550.</p><p>Gudmundsson, A., 2020. Volcanotectonics: Understanding the Structure, Deformation, and Dynamics of Volcanoes. Cambridge University Press, Cambridge.</p><p>Drymoni, K., Browning, J. Gudmundsson, A., 2020. Dyke-arrest scenarios in extensional regimes: insights from field observations and numerical models, Santorini, Greece. Journal of Volcanology and Geothermal Research (in press).</p><p> </p>

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