bluuebunny/crossref_metadata_2025_split huggingface dataset:
Automatic Drilling Dynamics Interpretation Using Deep Learning
Authors: Chen Wei , Yu Yingwei , Shen Yuelin , Zhang Zhengxin , Vesselinov Velizar 
Published: September 2019

Abstract
Severe drilling dynamics of a bottomhole assembly (BHA) causes energy to dissipate into vibrations which undermines drilling efficiency. Dangerous dynamics modes, such as backward whirling and high frequency torsional oscillation, could cause downhole drilling tools to fail prematurely. To mitigate the risk of failure due to these dangerous conditions, it is critical to identify the damaging dynamics modes by interpreting the drilling data. Based on a deep learning approach, a novel method was proposed to automatically identify severe drilling dynamics modes directly from the time-series data.
The drilling dynamics data can be obtained from either a downhole sensor measurement or transient dynamics simulation. First, a deep neural network, which is composed of convolutional and fully connected layers, is employed to explore patterns in the data by generating a feature map of drilling dynamics. Knowledge of drilling dynamics physics can be used to facilitate data clustering in the feature map. Each data cluster can be tagged with the corresponding drilling dynamics mode. Using the tagged dataset, a machine learning classification model can be trained to automatically identify the dynamics modes based on the input of time-series drilling data.
The deep learning approach can be implemented to recognize a collection of dynamics modes of BHA, such as various whirling patterns and high frequency torsional resonance. The most commonly available drilling dynamics data channels, accelerations and collar RPM, were used as the model inputs. The deep neural network was trained to predict the next data sample based on the previous time-series data. One of the hidden layers of the neural network was employed to generate the feature map, in which the dataset forms several clusters. The orbits of BHA movement were plotted on top of the clusters for pattern visualization. After this practice, the simple polygon boundary was drawn between whirling and stable cases, and the dataset was tagged automatically. With the tagged dataset, the classification model was trained to identify various whirling patterns and the stable drilling state. Similar processes can be readily applied to interpret other dynamics modes. Interpreting the drilling dynamics modes provided a high-level description of the data, which offered clues on how to optimize BHA design and drilling practices to improve efficiency.
The automatic interpretation of drilling dynamics data can significantly improve the consistency and efficiency of the existing manual interpretation workflow. The generated feature map enables the exploration of new motion patterns and new vibration modes. This approach eliminates the need to manually tag the data. With minimum human interactions, the dataset can be automatically tagged. The model employs only the raw time series data of basic dynamics channels as inputs, which makes the algorithm universally applicable for various data sources.
Novel Slow-Release Particle Technology for Use in Hydraulic Fracturing Applications
Authors: Yang Chao , Navarrete Reinaldo , Asadi Mahmoud , Karber Lionel , Hagelin Kyle 
Published: September 2019

Abstract
The formation and deposition of solids including mineral scale, paraffin, and asphaltene, may occur at any location of the oil and gas production system, from the bottom of the well to a gathering facility, due to the changes in the physical and chemical conditions associated with production fluids. Depositions can reduce the formation permeability, reservoir transmissibility and have detrimental impact on production rates during oil and gas production. Common practice is to complete the well and then apply a treatment and remediation program as necessary, including squeeze treatments and batch treatments.1
Horizontal, multi-stage hydraulic fracturing is widely used in the industry as stimulation practice.2 A single application providing long-term treatment is financially and operationally beneficial for operators. A solid inhibitor with slow-release active additives can extend the treatment life and reduce subsequent intervention costs attributed to deposition prevention and/or removal.
This paper reports on a new, slow-release particle technology developed for applications in hydraulic fracturing. This new technology does not rely on adsorption, impregnation or any other technology of embedment of additives onto a substrate. The new slow-release particles exhibit improved delayed release profile, high strength, and the capacity to incorporate active components, such as scale or paraffin inhibitor, either singly or in combination.
Surpassing the Challenges of a Robotic Traction System for Movement inside Long Flexible Obstructed Pipes
Authors: Donadel Basso Eduardo , André Perondi Eduardo , Francisco Lisboa Santos Hugo , Augusto Couto Barone Dante , Luis da Silva Júnior Anselmo , Viegas Wentz André , Mendel Henrique 
Published: September 2019

Abstract
The obstruction inside flexible lines with hydrates or paraffins is quite common in offshore production systems. In these cases, in order to perform the clearance of the pipes, many different techniques, usually time consuming and expensive, are currently used. This article presents the development of a new self-propelled robot that is under design to become an alternative solution for this problem, which has been a research challenge by decades.
The use of robots with umbilical cables inside long obstructed pipes with several curves and bends is currently an important challenge in the robotic field, especially due to the increased traction forces that may occur. The main challenge is the force in the umbilical cable caused by the friction between the cable and the inner pipe surface. This force can be theoretically outlined by the capstan Euler-Etelwein equation (usually applied to the case of rounding a capstan with a rope). In an early study, a theoretical model for cable traction was developed and experimentally validated. This model was used to calculate a typical friction force in a standard pipeline. Several in-pipe movement strategies were analyzed and a suitable mechanism was defined as the main element for the robot traction mechanism. Therefore, we show in this study that the traction challenge can be surpassed by a properly cable materials selection composed with a suitable traction system design. A mechanism base in an inchworm-like movement was selected due to its high traction capacity and, based in an extensive study, a hybrid (electric-hydraulic) system was developed. The electric power transmission is provided through the umbilical, and electric motors drive pumps which supply hydraulic power to linear pistons that execute the movement of the mechanical elements, moving the entire system. Previous analysis and tests indicate that the designed system will be suitable to perform the necessary missions.
Integrated Characterization of the Fracture Network in Fractured Shale Gas Reservoirs—Stochastic Fracture Modeling, Simulation and Assisted History Matching
Authors: Wu Yonghui , Cheng Linsong , Killough John E. , Huang Shijun , Fang Sidong , Jia Pin , Cao Renyi , Xue Yongchao 
Published: September 2019

Abstract
The large uncertainty in fracture characterization for shale gas reservoirs seriously affects the confidence in making forecasts, fracturing design, and taking recovery enhancement measures. This paper presents a workflow to characterize the complex fracture networks (CFNs) and reduce the uncertainty by integrating stochastic CFNs modeling constrained by core and microseismic data, reservoir simulation using a novel edge-based Green element method (eGEM), and assisted history matching based on Ensemble Kalman Filter (EnKF).
In this paper, the geometry of CFNs is generated stochastically constrained by the measurements of hydraulic fracturing treatment, core, and microseismic data. A stochastic parameterization model is used to generate an ensemble of initial realizations of the stress-dependent fracture conductivities of CFNs. To make the eGEM practicable for reservoir simulation, a steady-state fundamental solution is applied to the integral equation, and the technique of local grid refinement (LGR) is applied to refine the domain grids near the fractures. Finally, assisted-history-matching based on EnKF is implemented to calibrate the DFN models and further quantify the uncertainties in the fracture characterization.
The proposed technique is tested using a multi-stage fractured horizontal well from a shale gas field. After analyzing the history matching results, the proposed integrated workflow is shown to be efficient in characterizing fracture networks and reducing the uncertainties. The advantages are exhibited in several aspects. First, the eGEM-based Discrete-Fracture Model (DFM) is shown to be quite efficient in assisted history matching of large field applications because of eGEM’s high precision with coarse grids. This enables simulations of CFNs without upscaling the fractures using continuum approaches. In addition, CFNs geometry can be generated with the constraints of core and microseismic data, and a primary conductivity of CFNs can be generated using the hydraulic fracturing treatment data. Moreover, the uncertainties for CFNs characterization and EUR predictions can be further reduced with the application of EnKF in assimilating the production data.
This paper provides an efficient integrated workflow to characterize the fracture networks in fractured unconventional reservoirs. This workflow, which incorporated several efficient techniques including fracture network modeling, simulation and calibration, can be readily used in field applications. In addition, various data sources could be assimilated in this workflow to reduce the uncertainty in fracture characterization, including hydraulic fracturing treatment, core, microseismic and production data.
Transient Performance Behaviors of a Well Intercepting a Uniform-Flux Hydraulic Fracture within a Shale Reservoir — A Fractional Integration Approach
Authors: Valdes-Perez Alex R , Blasingame Thomas A , Larsen Leif 
Published: September 2019

Abstract
The standard modeling techniques for fractured wells were developed for conventional (higher permeability) reservoirs. The application of these techniques in fractal (shale) reservoirs often yield physically-inconsistent results which can cause over/mis-interpretation of the transient data. The purpose of this work is to provide a new modeling scheme using the "fractional integration" solution for hydraulically fractured wells producing from a fractal reservoir. This methodology takes into account the reservoir heterogeneity in the modeling of the fluid flow towards the hydraulic fracture and provides physically consistent diagnostic interpretations and parameters.
We have used the "fractional integration" approach to "couple" the fluid flow from a fractal (reservoir) to a Euclidean object (i.e., the hydraulic fracture). This approach requires rescaling the coordinate axes for the fractal reservoir using power-law relations.
In this work we derive generalized models that can reproduce the classic Euclidean hydraulic fracture scenarios. We studied the constant-rate and constant-pressure cases and found that our proposed models yield the following three flow periods: Period 1: Early Fractal-Formation (EFF) flow. This flow period is analogous to the formation-linear flow for conventional reservoirs. The transient signature of this flow period is only influenced by the conductivity index (reservoir heterogeneity fractal parameter).Period 2: Late Fractal-Formation (LFF) flow. This flow period can also be observed in conventional reservoirs, although its characteristics are not extensively documented in the existing literature. This period is influenced by the fracture length and the reservoir fractal parameters, i.e., the fractal dimension and the conductivity index.Period 3: Pseudo-Fractal (PF) Flow. This is analogous to the pseudo-radial flow regime for conventional reservoirs. The transient performance behavior of this flow period depends on the two reservoir fractal parameters defined in this work.
In performing this work, we provide the following technical contributions: We introduce a physically-consistent modeling scheme for a well with uniform-flux vertical fracture producing from a fractal (shale) reservoir.We show that the transient flow behavior for a well intercepting a uniform-flux vertical fracture can exhibit three distinct flow periods.We provide field demonstration cases which are analyzed and interpreted using the new solutions presented in this work.
Method for Characterizing the Aggregation of Wax Crystals and Improving the Wax Deposition Model
Authors: Wang Zhihua , Zhu Chaoliang , Lou Yuhua , Cheng Qinglin , Liu Yang , Wang Xinyu 
Published: September 2019

Abstract
Wax crystals can aggregate and precipitate when the oil temperature decreases to below the wax appearance temperature (WAT) of waxy crude oil, which has undesirable effects on the transportation of crude oil in pipelines. Thermodynamic models considering the molecular diffusion, shearing dispersion, and shear stripping as well as hydrodynamic models have been developed for predicting the wax deposition in crude oil pipelines. However, the aggregation behavior of wax crystals during crude oil production and transportation is not well understood. The microscopic rheological parameters have not been related to the bulk flow parameters in the shearing field, and the prediction of the wax deposition behavior under complex conditions is restricted by the vector characteristics of the shearing stress and flow rate. A set of microscopic experiments was performed in this study to obtain the basic information from images of wax crystals in shearing fields. A novel method of fractal dimensional analysis was introduced to elucidate the aggregation behavior of wax crystals in different shear flow fields. The fractal methodology for characterizing wax crystal aggregation was then developed, and a blanket algorithm was introduced to compute the fractal dimension of the aggregated wax crystals. The flow characteristics of waxy crude oil in a pipeline were correlated with the shearing stress work, and a wax deposition model focusing on shearing energy analysis was established. The results indicate that a quantitative interpretation of the wax crystal aggregation behavior can be realized using the fractal methodology. The aggregation behavior of the wax crystals is closely related to the temperature and shearing experienced by the waxy crude oil. The aggregation behavior will be intensified with decreasing temperature and shearing effect, and a wider fractal dimension distribution appears at lower temperatures when the same shear rate range is employed. The lower the fractal dimensions obtained at high temperature and strong shear action, the weaker will be the nonlinear characteristics of the wax crystal aggregation structure, and thus, the potential wax deposition will be inhibited during waxy crude oil production and transportation. Furthermore, the improved model provides a method for discussing the effects of the operating conditions on wax deposition. The average relative deviation between the improved model prediction results and experimental results from the literature is 3.01%–5.32%. The fractal methodology developed in this study and the improvement in wax deposition modeling are beneficial for understanding and optimizing flow assurance operations in the pipeline transportation of waxy crude oils, and the results are expected to facilitate a better understanding of the wax crystallization and deposition mechanism.
Elimination of the Sustained Casing Pressure using Self-Healing Cement in Turkmenistan Section of the Caspian Sea
Authors: Nafikova Svetlana , Bugrayev Amanmmamet , Taoutaou Salim , Baygeldiyev Gaygysyz , Akhmetzianov Ilshat , Gurbanov Guvanch , Eliwa Ihab 
Published: September 2019

Abstract
A major operator on the Caspian Turkmen shelf has started to encounter sustained casing pressures (SCP) attributable to insufficient isolation across a hydrocarbon gas zone, due to downhole stresses and other contributing factors. Enhanced placement techniques of conventional cements failed to prevent SCP, confirming the requirement for an alternative cement system that can withstand anticipated stresses and resolve this challenge. An innovative and cost-effective solution was applied and successfully solved the SCP challenge due to its unique self-healing properties.
If cracks or microannuli occur and hydrocarbons reach the cement, the system has the capability to repair itself, restoring integrity of the cement sheath without external intervention. The cement system is placed conventionally in the annulus across or above the hydrocarbon-bearing formation. It then acts as a pressure seal, expanding to accommodate downhole changes and healing if any hydrocarbon reaches it. This technology has been used in four wells in the field with excellent results.
Two wells were used to demonstrate the capabilities of the self-healing cement as a lead cement slurry, which created a cap over the pay zones. The self-healing cement was designed with low Young's modulus for optimum flexibility. To minimize the risk of set cement integrity failure due to microannuli or microdebonding from chemical shrinkage after setting, linear expansion up to 1.2% was incorporated into the design. After cementing, the wells were intentionally exposed to a sequence of high-pressure tests, which induced annular pressures in the wells. However, because of the self-repair capability of this cement, isolation and integrity were effectively restored in the two wells within 1 to 2 weeks without external intervention. As a result, the self-healing cement technology has become the standard for the field for all future wells, and the operator plans to extend the self-healing cement technology to other fields with similar challenges.
This paper clearly demonstrates successful casing pressure remediation without intervention by engineering a flexible, self-healing cement system. The design strategy, execution, evaluation, and results for two wells are discussed in detail and will help to guide future engineering and operations around the world.
Poroelastic Analytical Solution for the Nonlinear Productivity Index of Wells in Stress-Sensitive Reservoir Rocks
Authors: Zhang Wei , Mehrabian Amin 
Published: September 2019

Abstract
Reservoir depletion can induce substantial changes in the stress state of the rock. The coupled interaction between the pore fluid pressure and rock stress will then alter the reservoir permeability, which in turn reversely affects the productivity index of the production well. A new nonlinear analytical solution is developed for the drawdown-dependent productivity index of reservoirs under steady-state flow. Biot's theory of poroelasticity is used to derive the depletion-induced changes in the reservoir rock porosity and permeability. The well-known Mindlin's solution for a Nucleus of Strain in a semi-infinite elastic medium is applied as Green's function and integrated over the depleted volume of reservoir rock to obtain the 3D distribution of stress and volumetric strain distributions. The fluid transport equation is nonlinearly coupled to the solid mechanics solution via the stress-dependent permeability coefficients. A perturbation technique is applied to mathematically treat the described nonlinearity to solve for the coupled equations of pore fluid flow and rock stress under steady-state flow. The good match between the obtained analytical approximations for productivity index and the numerical solutions verifies the correctness and robustness of the proposed model.
Results indicate and confirm the expected strong dependency of the well productivity index to the drawdown magnitude as well as the poroelastic constitutive parameters of the reservoir rock, with the highest sensitivity to drained bulk modulus, followed by the reservoir depth and solid-grain modulus. The lowest PI sensitivity is to the pore fluid modulus and Poisson's ratio. The resulting productivity index is found out to be drawdown-dependent, which can render values substantially different than the productivity index estimate from the conventional flow-only analysis. The presented estimates for the related nonlinear productivity index can be readily used by the practicing engineers.
Application of Downhole Well Integrity Technology in the Petroleum Industry, A Case Study in the Horizontal Wellbore
Authors: Tao Li , Qiang Chen , Qiang Sun , Weiye Han , Shouzhi Huang , Longda Liu 
Published: September 2019

Abstract
Wellbore integrity was a thorny issue in China since hundreds of thousands of wells needed to be repaired annually, leading to cost increase and production delay. This problem became more excruciating in the long horizontal wellbore considering the high risk of downhole tools stuck. So far casing damage in the horizontal wellbore was either chemically plugged or separated by bridge plug, posing huge threat to the reservoir and future operations. Solid expandable tubular was a rising star in the downhole workover programme, its application in the horizontal wellbore would further enrich our technical warehouse to enhance the wellbore integrity.
In this paper, the challenges of horizontal wellbore workover operations were presented; the expandable technology was introduced and then innovated the adapt to the challenges, finally its field operation was described and relevant summaries of lessons were demonstrated.
The results indicated that as the number of horizontal well increased dramatically, problems such as casing damage, sand plugging occurred more frequently, downhole tools usually needed additional force to forward in the horizontal part to finish well logging or other activities, casing integrity was necessary to prevent the stuck of downhole tools.
Solid expandable tubular was a field proven technology, in order to overcome issues like tripping in process, expansion hurdles in the irregular well trajectory, the structure of solid expandable tubular was optimized radically. First the material of tubular was changed to achieve N80 steel grade after expansion, the OD of tubular was adjusted to maximize the annulus space between the casing and the tubular. Second the thread was restructured the further enhance its strength. Finally the rubber outside the tubular was innovated to prevent being worn out as much as possible during its friction with the horizontal wellbore. Field operation was carried out in west China, 18m length of expandable tubular was deliver into the end of 327m horizontal wellbore, expansion process was started and 41MPa expansion force was recorded.
This paper served to enrich our capabilities to deal with workover operation in the horizontal wellbore, its content helped better understand the principle, procedure and potential of this enable technology.