Investigation of Parent-Well Production Induced Stress Interference in Multilayer Unconventional Reservoirs

2022 ◽  
Author(s):  
Yanli Pei ◽  
Kamy Sepehrnoori
Keyword(s):  
Unconventional Reservoirs ◽  
Well Production ◽  
Induced Stress

Efficient Modeling of Depletion Induced Fracture Deformation in Unconventional Reservoirs

2021 ◽  
Author(s):  
Yanli Pei ◽  
Kamy Sepehrnoori
Keyword(s):  
Unconventional Reservoirs ◽  
Well Performance ◽  
Coupled Flow ◽  
Fracture Conductivity ◽  
Well Production ◽  
Closure Stress ◽  
Fracture Deformation ◽  
Fracture Closure ◽  
Stress Changes ◽  
Bottomhole Pressure

Abstract The change of fracture conductivity during reservoir depletion significantly affects the well performance and stress evolution in unconventional formations. A common practice is to model fracture deformation using the traditional finite element method with very dense unstructured grids representing complex fracture geometries. However, the associated computational cost is high, so previous studies mainly use empirical correlations to catch the fracture conductivity loss or neglect fracture deformation during the production period. This work proposes a novel coupled flow and geomechanics model with embedded fracture methods to capture the fracture deformation accurately yet efficiently in unconventional reservoirs. Under a single set of structured grids, an embedded discrete fracture model (EDFM) is employed to characterize fluid flow through discrete fractures by introducing non-neighboring connections, and an extended finite element method (XFEM) is applied to simulate discontinuities over fracture walls by adding phantom nodes. In addition, a modified proppant model is incorporated to represent interactions between proppants and hydraulic surfaces, and an iterative coupling scheme is implemented to link the fracture-related fluid flow and solid mechanics. Being validated against the classical benchmark problem, the coupled model is used to investigate the impacts of proppant strength, closure stress, and bottomhole pressure on fracture deformation, well production, and in-situ stresses. Numerical results indicate that weaker proppant support induces more fracture aperture and production losses, resulting in greater stress changes and higher residual pressure in the depletion region. In comparison, the fracture deformation for a well-propped scenario is modest and barely affects the well performance and stress redistribution. Less stressed formation corresponds to lower closure stress on fracture walls, which triggers limited fracture closure and stabilizes well production. Moreover, a moderate bottomhole pressure decline rate avoids significant fracture closure while preserves relatively high initial production rates. The coupled flow and geomechanics model with embedded fracture methods resolves computational difficulties in modeling complex fracture deformations and delivers more insights on production forecast and stress changes crucial to refracturing and infill operations.

The Influence of Development Target Depletion on Stress Evolution and Infill Drilling of Upside Target in the Permian Basin

2021 ◽  
pp. 1-20
Author(s):  
Yanli Pei ◽  
Wei Yu ◽  
Kamy Sepehrnoori ◽  
Yiwen Gong ◽  
Hongbing Xie ◽  
...  
Keyword(s):  
Stress State ◽  
Stress Field ◽  
Unconventional Reservoirs ◽  
Fracture Model ◽  
Stress Evolution ◽  
Permian Basin ◽  
Well Production ◽  
Infill Drilling ◽  
Reservoir Geomechanics ◽  
Parent Child

Summary The extensive depletion of the development target triggers the demand for infill drilling in the upside target of multilayer unconventional reservoirs. However, such an infill scheme in the field practice still heavily relies on empirical knowledge or pressure responses, and the geomechanics consequences have not been fully understood. Backed by the data set from the Permian Basin, in this work we present a novel integrated reservoir-geomechanics-fracture model to simulate the spatiotemporal stress evolution and locate the optimal development strategy in the upside target of the Bone Spring Formation. An embedded discrete fracture model (EDFM) is deployed in our fluid-flow simulation to characterize complex fractures, and the stress-dependent matrix permeability and fracture conductivity are included through the compaction/dilation option. After calibrating reservoir and fracture properties by history matching of an actual well in the development target (i.e., third Bone Spring), we run the finite element method (FEM)-based geomechanics simulation to model the 3D stress state evolution. Then a displacement discontinuity method (DDM) hydraulic fracture model is applied to simulate the multicluster fracture propagation under an updated heterogeneous stress field in the upside target (i.e., second Bone Spring). Numerical results indicate that stress field redistribution associated with parent-well production indeed vertically propagates to the upside target. The extent of stress reorientation at the infill location mainly depends on the parent-child horizontal offset, whereas the stress depletion is under the combined impact of horizontal offset, vertical offset, and infill time. A smaller parent-child horizontal offset aggravates the overlap of the stimulated reservoir volume (SRV), resulting in more substantial interwell interference and less desirable oil and gas production. The same trend is observed by varying the parent-child vertical offset. Moreover, the efficacy of an infill operation at an earlier time is less affected by parent-well depletion because of the less-disturbed stress state. The candidate infill-well locations at various infill timings are suggested based on the parent-well and child-well production cosimulation. Being able to incorporate both pressure and stress responses, the reservoir-geomechanics-fracture model delivers a more comprehensive understanding and a more integral solution of infill-well design in multilayer unconventional reservoirs. The conclusions provide practical guidelines for the subsequent development in the Permian Basin.

Incorporation of Physics into Machine Learning for Production Prediction from Unconventional Reservoirs: A Brief Review of the Gray-Box Approach

2021 ◽  
pp. 1-12
Author(s):  
Hui-Hai Liu ◽  
Jilin Zhang ◽  
Feng Liang ◽  
Cenk Temizel ◽  
Mustafa A. Basri ◽  
...  
Keyword(s):  
Machine Learning ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Complex Problem ◽  
Unconventional Reservoirs ◽  
Future Research ◽  
Gas Industry ◽  
Well Production ◽  
Determination Of Parameters ◽  
Production Prediction

Summary Prediction of well production from unconventional reservoirs is often a complex problem with an incomplete understanding of physics and a considerable amount of data. The most effective way for dealing with it is to use the gray-box approach that combines the strengths of physics-based models and machine learning (ML) used for dealing with certain components of the prediction where physical understanding is poor or difficult. However, the development of methodologies for the incorporation of physics into ML is still in its infancy, not only in the oil and gas industry, but also in other scientific and engineering communities, including the physics community. To set the stage for further advancing the use of combining physics-based models with ML for predicting well production, in this paper we present a brief review of the current developments in this area in the industry, including ML representation of numerical simulation results, determination of parameters for decline curve analysis (DCA) models with ML, physics-informed ML (PIML) that provides an efficient and gridless method for solving differential equations and for discovering governing equations from observations, and physics-constrained ML (PCML) that directly embeds a physics-based model into a neural network. The advantages and potential limitations of the methods are discussed. The future research directions in this area include, but are not limited to, further developing and refining methodologies, including algorithm development, to directly embed physics-based models into ML; exploring the usefulness of PIML for reservoir simulations; and adapting the new developments of how the physics and ML are incorporated in other communities to the well-production prediction. Finally, the methodologies we discuss in the paper can be generally applied to conventional reservoirs as well, although the focus here is on unconventional reservoirs.

Application of Micro-Proppant to Enhance Well Production in Unconventional Reservoirs: Laboratory and Field Results

2015 ◽  
Author(s):  
Jeff Dahl ◽  
Philip Nguyen ◽  
Ron Dusterhoft ◽  
James Calvin ◽  
Shameem Siddiqui
Keyword(s):  
Unconventional Reservoirs ◽  
Well Production

Forecasting of Horizontal Gas Well Production Decline in Unconventional Reservoirs using Productivity, Soft Computing and Swarm Intelligence Models

2018 ◽  
Vol 28 (3) ◽  
pp. 717-756 ◽  
Author(s):  
Eric Thompson Brantson ◽  
Binshan Ju ◽  
Yao Yevenyo Ziggah ◽  
Perpetual Hope Akwensi ◽  
Yan Sun ◽  
...  
Keyword(s):  
Swarm Intelligence ◽  
Soft Computing ◽  
Unconventional Reservoirs ◽  
Gas Well ◽  
Well Production ◽  
Intelligence Models

Consequences of rock layers and interfaces on hydraulic fracturing and well production of unconventional reservoirs

Geophysics ◽  
2018 ◽  
Vol 83 (6) ◽  
pp. MR333-MR344
Author(s):  
Seounghyun Rho ◽  
Roberto Suarez-Rivera ◽  
Samuel Noynaert
Keyword(s):  
Hydraulic Fracturing ◽  
Surface Area ◽  
Homogeneous Model ◽  
In Situ Stress ◽  
Unconventional Reservoirs ◽  
Rock Properties ◽  
Hydraulic Fractures ◽  
Shear Stresses ◽  
Principal Stresses ◽  
Well Production

Hydraulic fracturing is a fundamental condition for economic production of hydrocarbons from unconventional reservoirs. Hydrocarbon production is proportional to the propped surface area that is in contact with the reservoir and remains connected to the wellbore. Yet, the propped surface area controlling production appears to be considerably smaller than the surface area created during pumping. Somehow hydraulic fractures are disconnected, truncated, and reduced during production. One important mechanism causing this segmentation is the shear displacement of weak interfaces between rock layers. Shear stresses are generated in response to abrupt changes in material properties and changes in bed orientation, in relation to the orientation of the existing principal stresses. If the layered rocks are strongly laterally heterogeneous, they provide a high potential for shear failures and fracture segmentation along the interfaces between layers. The induced shear stress and shear slip also depend on the current geologic structure and following in situ stress loading, the stress alteration and fluid leakoff during hydraulic fracturing, and the existence of wells. We conducted numerical simulations using the finite-element method on layered and discontinuous rocks, and specifically in organic-rich mudstones and carbonate sequences. Our work was part of a field study. Three different layered rock models were simulated and compared: laterally homogeneous, laterally heterogeneous, and strongly laterally heterogeneous. For the latter, the heterogeneity was introduced by randomly varying the elastic rock properties of each layer. Our results indicate that localized shear stresses develop along interfaces between materials with contrasting properties and along the wellbore walls. This includes the generation of localized shear in planes that were principal in the homogeneous model. It was also seen that rock shear and slip, along interfaces between layers, may occur when the planes of weakness are pressurized (e.g., during hydraulic fracturing).

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