bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lessons Learned in Permian Gas-Lift Shale Wells: Dynamic Production Analysis With Downhole Gauge
Authors: Gonzalez L. E. , Chokshi R. N. , Gonzales R. O. , Adams T.. 
Published: May 2016

Abstract
Unconventional shale wells involve dynamic flow environments, which can be challenging to artificial lift systems required to produce these wells. Early-stage production from these wells is characterized by rapid production declines. Additionally, these wells experience significant production rate and phase fluctuations. Gas lift is a method of choice for producing gas-dominant assets, and it is commonly used early in the life cycle of liquid-dominant assets when production rates are higher. The design, the operation, and the general production management for shale wells requires a completely different approach and mindset than for conventional wells.
Production systems analysis, usually referred to as nodal analysis3, is a design and optimization technique used to evaluate a variety of current and future production scenarios under the assumption of steady state. Well test data, downhole gradient surveys, or production logging surveys are periodically sampled and provided as boundary conditions for the production systems analysis. The future reservoir conditions, typically obtained from reservoir simulations, are also used as boundary conditions. After performing the systems analysis, operators validate outcomes and determine the correct actions to take by using sporadic measurements. Operators are recognizing that the lower measurement frequency and resulting slower and offline analysis techniques provide incomplete, if not inaccurate, snapshots of the dynamic production environments of shale assets. To address that situation, several operators have started deploying downhole pressure/temperature gauges to understand and manage dynamic production behavior. There is a need for dynamic production modeling tools that analyze field conditions with realtime data and that provide real-time suggestions for corrective production improvement. This paper presents a dynamic production analysis methodology using real-time downhole measurements and its implementation in a software tool.
The presentation provides results from two shale wells produced using gas-lift technology in a Permian asset. Both wells are instrumented with permanent electronic downhole gauges below the operating orifice valve to measure pressure and temperature in the casing-tubing annulus and in the tubing. The real-time data from gauges is visualized and analyzed in real time to diagnose artificial lift performance, including gas-lift valve behavior. More importantly, the analysis-inferred reservoir static pressure and instantaneous productivity index can be compared to the numerical reservoir simulations.
Real-time downhole data coupled to dynamic production analysis is presented for the first time. This approach leads to more accurate production forecasting as well as optimization of highly dynamic shale wells.
Brittleness Analysis: A Methodology to Identify Sweet Spots in Shale Gas Reservoirs
Authors: Rojas L. Fernandez , Peña Y. Quintero , Carrillo Z. H. 
Published: May 2016

AbstractThe purpose of this paper is to propose a methodology based on analyze the impact of the brittleness index in hydraulic fracturing on shale gas reservoirs worldwide, and thereby define parameters to identify fraccable feasible sweet spots in shale plays prospects.A literature review was made so as to gather the largest amount of mechanical, petrophysical and geochemical data from shale gas reservoirs from countries all over the world such as United States, China, Argentina, Holland, Norway, Denmark and Sweden. Once available the data, different methods were used to calculate the brittleness index of each study case considering the effect of the mineralogical composition and elastic moduli such as Young's modulus and Poisson's ratio, both static and dynamic.The relation between the brittleness index at depth and the total organic carbon allowed to identify possible sweet spots within each prospect reservoir. Additionally, the analysis of brittleness index and mechanical behavior of those reservoirs permitted to establish what kind of fracturing fluid should be used in case of a hydraulic fracturing at those sweet spots, in order to achieve the most effective stimulation process.Integrated analysis of mechanical, petrophysical and geochemical properties is a practical methodology that allows to identify shale gas prospects by establishing analogies with known productive shale reservoirs, especially in countries where unconventional resources potential have not been estimated yet.
Gas Lift-Jet Pump Hybrid Completion Reduces Nonproductive Time During Unconventional Well Production
Authors: Pino O. A. , Pugh T. S. , Hubbard J.. 
Published: May 2016

Abstract
Gas lift is a preferred lifting method to produce unconventional wells across the world. During specific stages of the well life, however, it might happen that water percentage raises enough to make the tubing flow gradient too high for lifting with the maximum operating pressure and rate of injection gas. This results in unplanned nonproductive time. A slickline-deployable jet pump can be a cost-effective alternative to effectively unload the well and resume production with gas lift.
The addition of a sliding sleeve door (SSD) to the tubing string, installed between the deepest gas lift mandrel and the annular packer, will allow the deployment of a slickline-set jet pump. The backup jet pump provides a valuable and cost-effective alternative in three potential scenarios: when unloading fracking fluids before beginning gas-lift production, when restoring production after an unpredicted shutdown of the gas-lift compression system, and when the producing water cut becomes higher than expected.
An operator in Logan County, Oklahoma, installed the gas lift-jet pump hybrid completion in five wells. The completion was basically designed for gas lift with a standard "X" profile SSD installed between the packer and the operating gas-lift valve. The dual-purpose tubing string was installed in each well in one trip. To produce fracking fluids left in the wellbore, standard-flow jet pumps were set in the SSD, mobile hydraulic-lift surface units were hooked up to the Christmas tree and jet pump production operation started. On average, fracking water was produced 66% faster than by swabbing and rod pumping, and 33% faster than with nitrogen lift. Upon recovery of the fracking fluids, the wells were producing enough gas to successfully start the gas lift systems in approximately 6 days.
This simple but ingenious dual-purpose completion approach has already proved to solve the problem of unconventional well production load-up during the early production stage of gas lifted systems. The information provided in this paper will help operators plan, design, deploy, and operate a dual-purpose gas lift-jet pump well completion.
Comprehensive Determination of the Far-Field Earth Stresses for Rocks With Anisotropy in Tectonic Environment
Authors: Frydman M.. , Pacheco F.. , Pastor J.. , Canesin F. C. , Caniggia J.. , Davey H.. 
Published: May 2016

Abstract
Geomechanics has become an important tool for engineers and geologists, with classical applications in wellbore stability, sand management, and hydraulic fracturing. However, unconventional shale reservoirs cannot be evaluated with traditional models or on the basis of simple relationships between isotropic elastic properties, far-field stresses, and reservoir and mechanical properties. These plays are geologically complex and the reservoirs are heterogeneous in nature. Wells need to be hydraulically fractured for stimulation and, in a complex tectonic environment, the rock fabric and in situ stress strongly influence this process. We discuss a new methodology developed for stress modeling, taking into account the tectonic environment. We present a case study for the Vaca Muerta formation in Argentina. The obtained results contribute to the understanding of stress distribution in unconventional reservoirs.
Pressure Transient Analysis of Complex Fracture Networks in Shale Gas Reservoirs With Multiple-Porosity Transport Mechanisms
Authors: Teng W.. , Jiang Y.. , Jiang R.. , He J.. , Gao X.. , Liu Z.. 
Published: May 2016

AbstractShale gas flow is controlled by multiple mechanisms and multi-stage hydraulic fracturing often creates complex fracture networks. It is very challenging to incorporate various migration mechanisms of shale gas and accurately simulate the complex fracture networks in shale gas reservoirs. In this work, we present a semi-analytical model to study the pressure behavior in shale gas reservoirs. Multiple migration mechanisms are considered, which contain diffusion of dissolved gas in kerogen bulk, desorption from the surface of kerogen bulk and clay particles, slippage flow simultaneously from both organic pores and inorganic pores into natural fracture system and Darcy flow in natural fractures and hydraulic fracture network system. Line source function, Laplace transformation and the principle of superposition are employed to analytically describe flow behavior in reservoir system and a numerical discrete method is adopted to simulate the complex fracture networks. Main fractures and secondary fractures within the fracture networks are divided into elements with equal length. Gauss elimination method and Stehfest inversion algorithm are employed to calculate the pressure responses. We perform three case studies which contain multistage transverse fracture, orthogonal fracture network and un-orthogonal fracture network. Type curves are plotted and possible flow regimes are identified. With its rapid computational speed, yet capturing the physics of shale gas flow, this semi-analytical approach provides an efficient tool for people from multiple disciplines to perform pressure transient analysis of complex fracture networks in shale gas reservoirs.
Optimization of Enhanced Coalbed Methane Recovery With C02 Injection
Authors: Temizel C.. , Betancourt D. J. , Tiwari A.. , Zhang M.. , Aktas S. S. , Quiros F.. 
Published: May 2016

Abstract

Objectives/Scope
Coalbed methane (CBM) has become an important source of clean energy in the recent decades worldwide including the US, China, Australia, India and Russia with more than 60 countries having different degrees of promising coal reserves. CBM reservoirs are distinguished from conventional reservoirs due to the major difference in the mechanism of gas storage and production of water. In CBM reservoirs, pores act as the major storage mechanism as gas is trapped and stored there and produced by means of dewatering and thus lowering the reservoir pressure. Free gas forms as the pressure is lowered leading to increased gas permeability of coal and thus increasing recovery. Microbial activity and thermal maturation of organic compounds are the main mechanisms of methane generation in lower-and-higher rank coals, respectively. Even though methane is an abundant and clean energy source, there are certain operational, technical and economic challenges involved in its production due its unique nature outlined above. Thus, a strong understanding of the parameters and uncertainties that influence the recovery is crucial.

Methods, Procedures, Process
Due to the fact that the organic materials that make up coals generally have a stronger affinity for CO2 than for methane, CO2 is used as an enhanced recovery method to displace methane as an enhanced coalbed methane recovery (ECBM) method. While there is no current comprehensive optimization study on the effects of such factors, ECBM has a very significant role in the future of energy as it means more energy out of natural gas while eliminating the adverse effects of greenhouse gases.

Results, Observations, Conclusions
In this study, a standard SPE reservoir simulation model is used to study the factors influencing the recovery in coal bed methane reservoirs by investigating the significance of parameters including but not limited to porosity, adsorption capacity, fracture permeability along with coal density and irreducible water saturation.

Novel/Additive Information
The optimization results obtained by means of coupling a full-physics commercial numerical reservoir simulator with an optimization/uncertainty tool are presented outlining the different degrees of significance of these factors on production and ultimate recovery for better understanding of the phenomenon that will lead to more robust reservoir management decisions.
Comparison of Numerical vs Analytical Models for EUR Calculation and Optimization in Unconventional Reservoirs
Authors: Moinfar A.. , Erdle J. C. , Patel K.. 
Published: May 2016

Abstract
Analytical models available in Rate-Transient-Analysis (RTA) packages are widely used as tools for history matching and forecasting production in unconventional resources. There has also been an increasing interest in the use of numerical simulation of unconventional reservoirs. In this study, we use both methods to history match the production of hydraulically fractured unconventional wells, followed by forecasting future production to establish a well's EUR (Estimated Ultimate Recovery) for reserves determination purposes. This study's goal is to quantify the differences one might expect to encounter in a well's EUR when using analytical model-based RTA vs numerical simulation-based workflows in unconventional reservoirs.
First, we consider an undersaturated shale oil reservoir as a base model for this study. The base case also satisfies all assumptions inherent to analytical solution-based methods such as homogenous reservoir properties and fully-penetrating planar fractures. An excellent match between results of both methods for the base model validates the numerical simulation approach. We then impose a series of real-world deviations from RTA assumptions and investigate reliability of EUR predictions made by both approaches. In all cases, historical data and reference EURs are derived from finely-gridded numerical simulations.
Example results show that, in the presence of real-world deviations from RTA assumptions, analytical models can still match the historical production data; however, key reservoir and fracture parameters need to be modified drastically to compensate for the lack of sufficient physics in the analytical models. Results show that the analytical solution-based history-matched models are not predictive for future production, and somewhat surprisingly provide pessimistic EURs in all real-world scenarios investigated in this work. For the cases presented in this study, analytical models under-predict EURs by 6-17% when two years of production history is available for matching. The underestimation of EUR increases drastically (up to 60%) as the length of available historical data decreases from 2 years to 3 months.
For all cases, we also apply an efficient numerical simulation-based workflow for probabilistic forecasting of EURs. This workflow provides multiple history-matched models that are constrained by historical production data. The probabilistic forecast method employed in this work provides P90 (conservative), P50 (most likely), and P10 (optimistic) values for EUR. In all examples, the range of P90 to P10 EUR values includes the reference EUR, and the P50 values are within 2.2% of the reference EUR.
Optimized Completions Design With Integrated LWD and Well Site Geochemistry for Petrophysical Analysis and Enhanced Well Placement
Authors: Crosby Z. S. , Mejia C.. , Langford C.. , Nardi G.. , Heard S. T. , Mainali P.. , Galindo J.. 
Published: May 2016

AbstractDuring the evolution of developing unconventional resources, large variability in production has pushed the industry to look at combining key petrophysical factors to gain insight into the production contributions of each stage in a completion design. Along the wellbore, petrophysical variabilities are minimized while the completions operation and design are optimized by placing the well in the target zone with minimal wellbore tortuosity.Landing point identification and horizontal well placement using inorganic and organic elemental data acquired from drill cuttings and advanced mud-gas analysis at the wellsite, combined with LWD gamma ray spectroscopy enhances well placement decisions by providing a comprehensive near real-time chemostratigraphic interpretation. This is achieved while also maximizing petrophysical integration efficiency for well completion designs.
An Effluent Stream Treatment and Analysis System to Counteract Water Availability & Usage Issues for Unconventional Oil & Gas Resources
Authors: Alkhawaja A. A. , Hashem M. H. , Fernandes M. O. , Raheem N. O. 
Published: May 2016

AbstractAs production from unconventional (shale) oil and gas rises, large volumes of water are produced as a by-product. These water streams contain a variety of contaminants including: Total Dissolved Solids (TDS), Total Suspended Solids (TSS), Naturally Occurring Radioactive Material (NORM), heavy metals. Treating this water incurs additional costs. Moreover, abiding by environmental regulations set by authorities is the responsibility of the operator. In addition, hydraulic fracturing (fracking) operations consume a lot of water.This paper proposes the use of an online monitoring system to evaluate the water quality, which can be linked to a downstream program to evaluate the profitability of treating this water further. The Water Economic Feasibility Indicator (WEFI) program was also developed to help operators make decisions on the adequate water treatment technologies to employ based on economic parameters.A case study is presented to evaluate the program, which involved using water production data from a field. The results showed that introducing Multi-Effect Distillation (MED) and Vapor Compression Distillation (VCD) technologies to treat the water further yields favorable outcomes. Graphs were plotted, demonstrating the associated costs of MED and VCD. Moreover, the cumulative net present value (NPV) of profit generated from sales of potable water is higher for VCD than MED.Another possible use of this water is agriculture and livestock watering. This lowers the water stress in the region. Findings indicate that it is profitable to process the water to a potable/irrigation level using VCD equipment than to dispose of it, thereby providing net monetary, social, and environmental benefits.
Two-Phase Flow Model and Well Testing Analysis for Multi-Stage Fractured Horizontal Well in Shale Gas Reservoirs
Authors: Xie W.. , Yang H.. , Wu J.. , Feng X.. , Zhang X.. , Zheng M.. 
Published: May 2016

Abstract
Two-phase flow in shale gas reservoirs is caused by water flowback after multi-stage fractured, this paper presents a two-phase pressure transient analysis model of multi-stage fractured horizontal well in shale gas reservoirs. With the new mathematics model, the two-phase flow characteristics and well testing analysis for early production period can be described.
The two-phase flow model is established by material balance law, Langmuir isotherm law and Fick diffusion law. Accurate solution to this flow model is obtained by source function theory, Laplace transform, three-dimensional eigenvalue method and orthogonal transformation. According to the solution, bilogarithmic type curve of the two-phase flow model is illustrated, the pressure transient performance under the effects of hydraulic fractures and shale gas reservoir properties are discussed.
It is found that there are seven different flow regimes which have been identified on the type curve of two-phase flow model, initial gas-water saturation, storage ratio and fractured stages have deeply impacted the type curve; absorption index, skin factor and interporosity flow coefficient have lower influence to the curve shape. According to the research results and field data of Lower Paleozoic shale in China, improved well testing analysis and dynamic monitoring have been provided. The research of this paper can make optimization design for the parameters selection of drilling and hydrofracture in shale gas reservoir.
Successful Dynamic Closure Test Using Controlled Flow Back in the Vaca Muerta Formation
Authors: Varela R. A. , Maniere J. L. 
Published: May 2016

Abstract
The Vaca Muerta formation is a shale oil and gas reservoir under active tectonics created by the Andes which are compressing the basin in an east to west direction and creates a varying stress regime both in horizontal and vertical directions. Additionally, this formation is composed of alternating layers of three litho-types with contrasted mechanical properties. These are organic shale, carbonate and ash beds. Slippage or debonding at weak-strong interfaces separating laminations is suspected to further contribute to the development of horizontal fracture components or T-Shape fractures during hydraulic fracturing when the fracturing pressure reaches the overburden (Zhang et al. 2007).
Selecting the proper landing position of horizontal wells in these compressive environments depends not only on the reservoir quality but also in selecting a layer which combines lower stress with sufficient vertical connectivity, thus minimizing detrimental effect from T-Shape propagation behavior.
Closure pressure can be obtained by performing a Dynamic in Situ Stress Test by force-closing the fracture (Nolte 1979; Raaen and Brudy, 2001). To this effect, YPF initiated in 2015 a campaign of in situ stress measurements across the Quintuco-Vaca Muerta system in vertical exploration and pilot wells. The objective was not only to predict a more accurate mud weight window to drill through the Vaca Muerta but mostly to measure as best as possible the difference between the overburden and the minimum horizontal stress to build a mechanical earth model accurate enough to help select better landing points for horizontal wells.
There are 3 scales at which dynamic closure tests are performed. At the smallest scale, a micro-fracture is created by pumping a little amount of drilling fluid at few liters/minute in 1m open hole isolated between straddle packers. At the largest scale, in a cased-hole perforated well, the dynamic closure test is performed as part of fracturing data acquisition before fracture operation: at this scale the test involves tens of bbls pumped at 5-10 bpm. Finally stress can be measured during Extended Leakoff Test (ELOT or XLOT) acquired in open hole at the casing shoe. After a literature review of the development of the flow back method this paper presents extensive details and operational procedure recommendations that were obtained from successful XLOT combining multiple cycles with injection, forced flow back and reopening sequence in the Neuquén basin.
On Construction of Bit-Interleaved Coded Modulation Systems with Iterative Decoding
Authors: Mai Quoc Khanh , Dinh The Cuong , Hashimoto Takeshi 
Published: May 2016

A new construction of Bit-Interleaved Coded Modulation systems with Iterative Decoding (BICM-ID) is proposed to achieve the best performance over white additive Gaussian noise (AWGN) channels, assuming that the ideal feedback (IF) holds for iterative decoding. For a class of so-called regular IF mappings, new upper bounds for error probabilities are presented for both cases of BICM-ID systems using overall and in-line interleaving. Search results for component Recursive Systematic Convolutional (RSC) codes with and without puncturing are reported for 4-PSK and 8-PSK signal sets.
Improving the Behavior of an Electro-Optic Modulator by Controlling Its Temperature
Authors: Bui Dang Thanh , Nguyen Lam Duy , Journet Bernard 
Published: May 2016

The purpose of this paper is to present the improvement of the stability of an electro-optic modulator obtained from its temperature control. A digital system based on PSOC microcontroller and a small power amplifier has been developed. The behavior of the modulator can be observed by the way of its nonlinear properties. Thanks to the improved thermal stability, it is possible to reduce significantly the drift of the electro-optic modulator.