bluuebunny/crossref_metadata_2025_split huggingface dataset:
Advancing Multi-Stage Fracturing Using Horizontal JITP and Autonomous Completion Systems
Authors: Benish Tim , Angeles Renzo , Tolman Randy , Entchev Pavlin , Kumaran Krishnan 
Published: May 2016

Abstract
The execution and optimization of multi-stage fracturing treatments remains one of the most critical steps in the economic development of unconventional resources. Two recently developed and field tested technologies offer a step-change in fracturing operations: Horizontal Just-In-Time Perforating (JITP) and Autonomous Completion Systems. While JITP is a well-established technique (extensively used in the Piceance basin, Colorado), its application to horizontal wells is relatively new and promises improved single-zone stimulation, significantly less use of horsepower, reduced number of frac plugs, and added flexibility in water management. In addition, ExxonMobil is actively progressing its proprietary Autonomous Completion Systems that maximize surface equipment utilization by removing the need for umbilical intervention (wireline, coiled tubing, or tractors), which also eliminates the need for lubricators, lifting equipment, additional personnel and vehicles, and improves safety.
This paper presents the latest milestones achieved in the development of these completion technologies. The application of JITP to horizontal wells was recently successfully confirmed with a comprehensive pilot program that included more than 30 wells and over 1400 single-zone treatments. Likewise, Autonomous Completion Systems entail broader applications beyond perforating systems. The key enabler for this technology is the frangible downhole navigation system which is undergoing field testing. In addition, the autonomous completion components are fully friable and do not require additional retrieval runs. The use of these technologies is anticipated to create new opportunities in equipment utilization efficiency and operational flexibility to the multi-stage fracturing methods available in the industry today.
Assessing E&P and Drilling Risks With Seismic Uncertainty Analysis
Authors: Osypov Konstantin , Ivanova Natalia , Yang Yi , Fournier Aime , Nichols Dave , Bachrach Ran , Yarman Can Evren , Nikolenko Dmitry 
Published: May 2016

Abstract
Exploration and Production (E&P) business faces uncertainty of our knowledge about the Earth at all stages of the aggregated workflow. Every stage uses ambiguous input and generates ambiguous output that becomes input to the next stage. Thus, understanding, quantifying and tracking uncertainty across stages and disciplines are essential for the ultimate uncertainty that impacts decision-making. In particular, the structural uncertainty is derived from the model uncertainty as a result of seismic depth imaging. Whilst the underlying ambiguity can never be fully eradicated, a quantified measure of these uncertainties provides deeper understanding of the risks and leads to more informed decision making. In the past decade, with the advancement of sensor and computer technology, the seismic industry has made great improvements in data-acquisition designs as well as depth-imaging and model-building algorithms. However, the cost/benefit justification for the value of information (VoI) obtained by utilization of these technologies remains mainly qualitative. The same limitation applies to geoscience knowledge. This paper discusses how uncertainty analysis can lead to quantifying VoI and also how application of probabilistic assessment of our geoscience knowledge can lead to investment decision-making based on probabilistic appraisal. We demonstrate that uncertainty is a good metric for the value of knowledge and serves also as a unifying language for translating, transmitting, and enhancing knowledge as one E&P stage transitions to another and as one discipline communicates with another. The paper discusses a stochastic technique of this translation through evaluation of different appraisal parameters (gross rock volume, original oil in place, net primary production) as an extended application of seismic-based imaging and structural uncertainty derived from velocity model building.

Introduction and Motivation
The overall business value within an operating energy company is generated through a long chain of multi-disciplinary sub-businesses. The bigger the company and the more sub-businesses it contains, the more challenging it becomes to dissect and quantify the value of each particular sub-business, technology, and individual. Furthermore, lack of communication between different sub-business and individuals significantly hampers the overall company value. Human nature circumvents this issue as each individual tends to emphasize his or her contribution. Each sub-business represents a certain stage of the generalized E&P process and has its own discipline language and necessary inputs and outputs. These inputs and outputs might be links to different sub-businesses and disciplines with different languages. Therefore, the overall value can be easily lost or diminished in translation.
Increasing Production by Applying Simple, Field Proven Slug Control Technology
Authors: Fong Y. , Yaw S. , Groote G. , Haandrikman G. 
Published: May 2016

Abstract

Description
Large fluctuations in gas and/or liquid production can lead to major disruptions on the topside facilities. These fluctuations are caused by the fluid composition, geometrical layout and operating conditions of the production system. With the current trends of: Producing marginal gas/condensate and oil fields to existing facilities with subsea tie-backs, Developing more deepwater fields, Producing from existing production facilities towards the end of field life cycle, irregular production or slugging pipeline systems are observed more frequently. Therefore, slug mitigation techniques may achieve significant value impact on the business. The most recent technology in Shell for slug control is the Smart Choke. This technology consists of a single control valve that is installed between the riser top and the first stage separator. It is an active slug control device acting on gas and liquid surges without the requirement of phase separation upstream of the control valve. The basic control mechanism maintains a constant total volumetric flow at the system outlet. Furthermore, a detection algorithm is incorporated, which detects 'liquid only' or 'gas only' production. Based on this, the controller will switch between the different control modes for slug control. Additional to this flow controller, a slow valve position controller and a differential pressure override controller is used to ensure that the output of the volumetric flow controller remains in the range of the normal (or desired) operating valve position.
Using Diffusion Maps for Latent Space Analysis on Seismic Waveforms of Incised Valleys in the Anadarko Basin, Oklahoma, USA
Authors: Bratberg Ivar , Wallet Bradley C. , Davogustto Oswaldo 
Published: May 2016

Abstract

Summary
In this work we present a new method for latent space mapping based upon inter-point similarities. This method, diffusion maps, has a number of nice qualities compared with previous methods including the fact that it is based upon inter-point similarities rather than a Euclidean space. We then demonstrate application of this approach to mapping an incised valley system from the Anadarko Basin, Oklahoma, USA.

Introduction
Multi-dimensional data is commonly encountered in attribute analysis where the desire is to combine several attributes with complementary properties. As geophysicists, we tend to view attribute spaces higher than four dimensional as being undesirable as they cannot be visualized using common color models such as ARGB space. Furthermore, mathematical considerations such as the Curse of Dimensionality (Bellmann, 1957) make working in lower dimensional space necessary.
(Guo, Marfurt, Liu, & Dou, 2006) discussed an unsupervised learning method for doing dimensionality reduction of attributes using Principal Component Analysis (PCA). While this method has been shown to be useful in a broad range of applications, they are limited in their ability to capture non-linear structure in multidimensional attribute space. Retaining this non-linearity is important as data sets generally present a heterogeneous mix of latent processes that, taken as a whole, are unlikely to be well represented by a single low-dimensional linear manifold.
A number of non-linear methods of manifold learning have been applied to seismic attributes and waveform modeling (Wallet & Marfurt, 2008). Self organizing maps (SOM) is the best known of these approaches, and it is available in a number of commercial products. (Wallet & Perez, 2009) also demonstrated the use of a statistical method, generative topographical maps (GTM).
(Wallet & Perez, 2009) applied diffusion maps to the problem of modeling well log data. They noted that the high computational demands of diffusion maps was an impediment to scaling to reasonable sized seismic problems. In this paper, we present an estimation method that deals with this problem.
Coiled Tubing and Well Testing Experiences on Sichuan Horizontal Shale Gas Wells
Authors: Stolte Chris , Wu Chris , Carroll Darryrl , Shiqian Wang 
Published: May 2016

Abstract
Shell China, in partnership with PetroChina Southwest began horizontal completions in its Sichuan shale gas project in 2012. By the end of 2012, two vertical and three horizontal wells were drilled and completed in the Lower Longmaxi Hot Shale interval. Performance has continuously improved throughout the implementation of the completions program1 and significant technical and operational challenges were overcome.
The three horizontal wells were drilled with progressive horizontal lengths. On the third and longest well in the sequence, difficulties were encountered when attempting to mill plugs in the horizontal section. Well pressures were in excess of coiled tubing limits and the plugs could not be milled. As a result, the well was produced with flow-through plugs in place until the well pressure could be reduced and a higher pressure coiled tubing reel was available. Due to the high well pressures observed, additional measures were taken to reduce operational risk during the coiled tubing millout and ensure a successful operation. The flowback package design was improved by utilizing hydraulic chokes in place of manual chokes and a dual-plug catcher system was installed in the flowback package. In addition to improving the flowback package for millout operations changes were made to the flare system. After the coiled tubing millout was completed, difficulties were encountered during the full phase well test requiring the horizontal flare to be replaced with a vertical flare due to HSE concerns. The challenges experienced during this operation and the improvement aspects gained will be utilized in the completions planning and execution of the next phase of horizontal wells.
This paper highlights the coil tubing millout, flowback, and well test learning experiences gained during the completion operations of the second and third horizontal wells.
Geological Reservoir Modelling in an Unconventional Play Setting: Appraisal of the JinQiu Block, Sichuan Basin, China
Authors: Mueller Dietmar , Rolph Alan , Ha Kwong Tak , Zhao Da Hua , Carl Brian S. , Liao Xi , Xu Long 
Published: May 2016

Abstract
Fluvial-lacustrine deposits of the Xujiahe Formation are the primary reservoir target for an ongoing appraisal project in the northwest Sichuan basin. The late Triassic clastics are comprised of six members T3×1 to T3×6. The amalgamated channel sandstone sections of the T3×2 and T3×4 members may form an "inefficient" Basin-Centered gas play charged from downdip source rock while the calcarenites, coaly shale, and calcareous siltstones of the T3×3 and T3×5/6 are possibly charged by local source rock.
Static modelling helped to improve understanding of production history for un-fracced vintage wells and early production behavior of newly drilled appraisal wells. Well sector models (scale of ~1×1 km) were created for this purpose.
The ability to predict areas with low water production is crucial for the economic feasibility of Xujiahe development. Water saturation versus porosity cross plots provided key input to saturation models in static models. The cross-plot method tentatively helps predict well productivity but further calibration is necessary.

Introduction
The Xujiahe formation consists of sequences of coaly calcareous siltstones and shales alternating with high Net/Gross (N/G) quartzo-feldspathic arenites. In the study area, the Xujiahe Formation ranges from 900–1300m in thickness, deepening and decreasing in N/G towards the NW. These changes reflect a facies change from stable platform in the SE Sichuan basin to a foredeep to the NW.
The Xujaihe formation is stratigraphically subdivided into six members T3×1 to T3×6 across the Sichuan basin. In the study area the uppermost T3×5 and T3×6 members consist of interbedded shales, thin coals, calcareous silstones and calcarenite sandstone. Although separated elsewhere in the basin, in the study area the T3×5/6 are combined because no clear boundary is recognizable. Xujiahe members T3×3, T3×2Lower and T3x1–3 are similar in lithology to the T3×5/6. The depositional environment of these coaly intervals is interpreted as shallow lacustrine/marsh environment with ephemeral meandering rivers. Calcarenite sandstones occur as isolated 10–50m thick intervals and are difficult to correlate. Calcarenites are interpreted to erode underlying shales, siltstones and thin coals, an assertion supported by limited 3D seismic. Calcarenite log porosity ranges from &lt;3–5%. Calcarenite sandstone intervals do not contain observable wet zones.
Improved Methods and Workflows for Multi-Zone Stimulation
Authors: Nygaard Kris , Gosavi Shekhar , Entchev Pavlin , Zhou Fuping , El-Rabaa Wadood , Shuchart Chris 
Published: May 2016

Abstract
Economic production from many low permeability unconventional reservoirs has been enabled by the ability to propagate multiple stimulation treatments per well and from multiple wellbores located on a single pad or platform. A variety of design procedures and mechanical means have been developed to create improved connections to the reservoir, reflecting ongoing innovation in improving stimulation effectiveness while enabling reliable treatment placement and completion cost reduction. Both modeling and interpretation tools have been developed to predict, assess, and optimize stimulation treatment design and placement.
Successful multi-zone stimulation requires evaluation and selection of many options - ranging from rock property design assumptions to methods of zonal isolation and fluid diversion to the efficient use of water and equipment deployment. Hence it is essential to incorporate strategies to integrate multi-disciplinary technology, operational data, and economic optimization in the workflows to achieve the best results. These strategies also require the flexibility to adapt various existing and emerging technologies within the unconventional reservoirs and account for the local operating environment and conditions.
This paper examines the fundamental elements driving multi-zone stimulation effectiveness based on integration of extensive field experience and research in reservoirs requiring multi-zone stimulation to unlock their economic potential. Tools and workflows will be illustrated that have improved multi-zone stimulation effectiveness, enabled significant operational efficiencies, and have led to enhanced well performance and resource recovery.

Introduction
Worldwide, substantial oil and gas resources are contained in low permeability formations. Many of these resources are characterized by thick intervals and/or multiple reservoir targets. In addition, some form of stimulation such as matrix acidizing, proppant fracturing, or acid fracturing is required to effectively and optimally produce these resources. However, the increased geologic and reservoir heterogeneities present in these resources can lead to substantial complications to the stimulation treatment operations, and reduction in stimulation effectiveness. To address these issues and enable more efficient resource recovery, during the last decade, ExxonMobil has focused on developing fit-for-purpose design methods, completion systems and procedures to enable optimization of stimulation treatments.
Study on Physical Simulation Experimental Technology of Ultra-low Permeability Large-scale Outcrop Model
Authors: Zhengming Yang , Xuewei Liu , Xuan Xu , Yapu Zhang , Xuewu Wang 
Published: May 2016

Abstract
Ultra-low permeability reserves have accounted for a very large proportion of China's proven reserves and undeveloped reserves at present, so it is very urgent to deeply study the seepage flow law of ultra-low permeability reservoirs. This paper proposed a rock screening criterion for large outcrop models. Meanwhile, encapsulation and saturation methods, pressure and flow field test methods for large outcrop models were developed according to the reservoir characteristics and fluid seepage flow characteristics of ultra-low permeability oilfields in each oil region. Based on those new experimental technologies, the 2D nonlinear seepage flow law of ultra-low permeability reservoirs has been studied with the large outcrop models. Experimental results indicate during the fluid seepage flow in a large outcrop model, there is a non-flow area, a nonlinear seepage flow area, and a quasi-linear seepage flow area on plane; in addition, the variation law of pressure gradient field and flow with different displacing pore volumes has been analyzed, thereby laying a substantial foundation for establishing the evaluation methodology for the effective driving pressure system of ultra-low permeability reservoirs.

Introduction
Ultra-low permeability reserves have accounted for a very large proportion of China's proven reserves and undeveloped reserves and developed ultra-low permeability oilfields have become more and more in recent decades[1]. Therefore, it is very urgent to deeply study the seepage flow law of fluids in ultra-low permeability porous media for providing guidance to reasonable development of ultra-low permeability oilfields. At present, all analyses and theoretical studies of the seepage flow law of ultra-low permeability reservoirs are based on one-dimensional physical simulation experiments and microtubule flow experiments[2,3,4] instead of fluid seepage flow experiments on ultra-low permeability plate models, so the corresponding research findings can neither be applied in real ultra-low permeability reservoirs to a relatively large extent nor indicate the nonlinear plane seepage flow law of ultra-low permeability reservoirs.
Experimental studies of domestic and foreign large plate models[5,6,7] focus on EOR, the models are basically sand-packed models, and there are rare large outcrop models used to study the seepage flow law of ultra-low permeability reservoirs. Therefore, this paper has analyzed and studied large outcrop models in terms of rock screening, model making, physical simulation experiment unit, pressure and flow field test methods, fluid seepage flow law in large outcrop models, etc. so as to form a physical simulation experiment technology of ultra-low permeability large outcrop models and lay a substantial foundation for establishing the evaluation methodology for the effective driving pressure system of ultra-low permeability reservoirs.
Performances of 3D Frequency-Domain Full-Waveform Inversion Based on Frequency-Domain Direct-Solver and Time-Domain Modeling: Application to 3D OBC Data from the Valhall Field
Authors: Brossier Romain , Etienne Vincent , Hu Guanghui , Operto Stephane , Virieux Jean 
Published: May 2016

Abstract
This study addresses the performances of different approaches to tackle 3D frequency-domain Full Waveform Inversion (FWI). FWI is becoming an appealing method to build high resolution velocity models from wide-azimuth seismic data. Three-dimensional frequency-domain solutions of the wave-equation for frequency-domain FWI can be computed with several methods. In the frequency domain, direct or iterative solvers can be used to solve the linear system resulting from the discretization of the wave equation. Alternatively, frequency responses can be computed by time-domain modeling coupled with discrete Fourier transform or phase-sensitive detection method. For a large number of seismic sources, the computational time of all of the methods scale along similar lines to the size of the problem, although the performances of the direct-solver approach is hampered by the limited scalability and the memory demand of the lower-upper decomposition of the forward-problem operator.
We implement the direct-solver and the time-domain modeling approaches in 3D acoustic frequency-domain FWI, which is applied to real 3D wide-azimuth OBC data from the Valhall field, North Sea, at low frequencies (&lt; 5 Hz). We show, for this case study, that even if less flexible for high-performance computing, the direct-solver approach is one order of magnitude more efficient in computing time/resources that the time-domain approach, if the signal-to-noise ratio in the data is sufficiently-high to limit the inversion to few frequencies. We finally discuss the performances, pros and cons of both methods, which depend on the wave physics (acoustic versus visco-acoustic, anisotropy, extension toward elastic or visco-elastic), the acquisition geometry (streamer-like versus fixed-spread acquisitions) and the computing architectures (small versus large amount of memory per computing node).