bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of Relative Location Techniques to Induced Microseismicity from Hydraulic Fracturing
Authors: Reyes-Montes J. M. , Pettitt W. S. , Hemmings B. , Haycox J. R. , Andrews J. R. , Young R. P. 
Published: October 2009

Abstract
Microseismic monitoring is routinely used for imaging the fracture network induced by hydrofracture treatments. One of the principal sources of uncertainties in the location of hypocentres is the velocity structure used in the location algorithm, which in most cases is approximated by layered models from sonic logs or estimated from perforation shot arrival times. Hypocentral uncertainties can be reduced by an order of magnitude, and the number of events located significantly increased, by using relative location methods that reduce the location volume to a small region around the seismic source.
Relative location methods are valid provided that the separation between the processed events is small compared to the ray-path lengths between source and receiver. The location is obtained through the inversion of differential travel times with respect to one chosen master event, minimizing the relative moveout residual. In this study, a new step-wise master-event relative-moveout location is applied to microseismic events induced during hydrofracture treatment.
The unique step-wise addition to the technique overcomes the limitations of separation distance by constructing a lattice of master events formed by all available good quality events that are located with a classic location algorithms. The minimization search is extended to the complete fracture volume as defined by the master events, converging to a solution that minimizes the relative moveout residual with respect to any of the available masters within the distance range. The use of arrival time differences with respect to a master event allows the location of events with P- and/or S-wave arrivals. Using the step-wise approach, the increased resolution in seismic location achieved by relative location methods is propagated to the complete set of events in a hydrofracture treatment. Furthermore, the method allows a significantly higher number of events to be located as only one phase (P or S wave) need be identified, assuming the events are in the vicinity of a master event with high quality arrivals.
We provide results from an example data set to illustrate the higher resolution and increase in number of located events that can be obtained through the application of the stepwise relative-moveout location algorithm.
A Robust Measure of Heterogeneity for Ranking Earth Models: The F-PHI Curve and Dynamic Lorenz Coefficient
Authors: Shook G. Michael , Mitchell Kameron M. 
Published: October 2009

Abstract
A new method for estimating heterogeneity in Earth models is presented. The new approach requires running a streamline simulator only a few timesteps, so multi-million cell models are evaluated in minutes. Using streamline time of flight and volumetric flow rate information from the simulation, a flow capacity diagram and sweep efficiency history can be determined. Five different measures of heterogeneity can be obtained from these two diagnostic plots.
We then evaluated each of these measures of heterogeneity for 450 models that were constructed using a wide range of Dykstra-Parsons coefficient and correlation lengths, and 2 different well patterns. The measures of heterogeneity were plotted against discounted oil recovery to determine the best measure of heterogeneity. From this study we conclude the Lorenz coefficient – as determined from dynamic data – is the single best measure of heterogeneity.
The Influence of CO2 Solubility in Brine on CO2 Flooding Simulation
Authors: Yan Wei , Stenby Erling H. 
Published: October 2009

Abstract
The solubility of CO2 in brine is considerable under high pressure where CO2 flooding processes are carried out. The dissolution of CO2 into the large amount of brine/water either initially present in reservoirs or later injected into them is therefore a non-negligible factor in CO2 flooding simulation, especially simulations of CO2 injection into water flooded reservoirs and CO2 water-alternating-gas (WAG) injection. In this work, the Peng-Robinson equation of state (EoS) modified by Søreide and Whitson was further improved to describe the phase equilibrium between CO2 and brine. The EoS model was then combined with a robust multiphase flash subroutine to form the core of a one dimensional slimtube simulator. The simulator provides a flexible description of the phase equilibrium between the water phase and the hydrocarbon phases. Water can be treated as an inert phase, or only dissolving CO2, or both dissolving CO2 and vaporizing to the hydrocarbon phases. The effect of CO2 solubility and water content in hydrocarbon phases on CO2 flooding simulation can therefore be investigated. With the slimtube simulator, a series of one-dimensional continuous CO2 flooding with water initially present in the reservoir were simulated using different phase equilibrium descriptions. The difference caused by different phase equilibrium descriptions was discussed in terms of saturation and composition profiles, final recoveries, minimum miscibility pressure, delay in gas breakthrough time, and CO2 loss to the brine phase. It was also investigated how the difference changes with pressure, temperature, initial water saturation, and brine salinity.
Extraction of Dissolved Methane in Brines by CO2 Injection: Implication for CO2 Sequestration
Authors: Taggart Ian 
Published: October 2009

Abstract
The solubility of CO2 in underground saline formations is considered to offer significant long-term storage capability to effectively sequester large amounts of anthropogenic CO2. Unlike EOR, geosequestration relies on longer time scales and involves significantly greater volumes of CO2. Many geosequestration studies assume that the initial brine state is one containing no dissolved hydrocarbons and therefore apply simplistic two component solubility models starting from a zero dissolved gas state. Many brine formations near hydrocarbons however tend to be close to saturation by methane. The introduction of excess CO2 in such systems results in an extraction of the methane into the CO2 rich phase which in turn, has implications for monitoring of any sequestration project and offers the possibly additional methane mobilization and recovery.
Advanced Automatic Control for Dual-Gradient Drilling
Authors: Breyholtz Øyvind , Nygaard Gerhard , Nikolaou Michael 
Published: October 2009

Abstract
Managed pressure drilling offers unprecedented capabilities for precise pressure control in drilling operations. This capability, created by the availability of new hardware tools, creates the need for tight coordination of such tools, to ensure reliable and safe operation. The use of model predictive control is proposed as a multivariable control framework that can coordinate multiple variables to offer both better performance and higher reliability and safety compared to current practice. A case study on a dual-gradient drilling system is presented to demonstrate how model predictive control can simultaneously control bottomhole pressure and hook position during drill string movement, by simultaneously manipulating the main pump flow rate, seabed pump flow rate, and drill string velocity. Computer simulations show that the proposed approach results in much lower bottomhole pressure deviations during drill string movement that manual control of hook position alone. The implications of this study as well as future directions for integration of additional variables and use of appropriate model predictive control variants are discussed.
Acoustic Logging Techniques for Guiding Casing Recovery Operations in Deepwater Gulf of Mexico
Authors: Donovan Glenn , Fadesere Peter 
Published: October 2009

Abstract
While ultrasonic logging devices have been used in recent years to determine the likelihood that casing strings are unbonded and thus free to be removed in a casing recovery, this application is still under development. The uniqueness of this application lies in the fact that the bonding forces present on the outside of the casing are caused by drilling fluids in varying stages of decomposition as opposed to cement. The fact that the exact composition of these altered fluids is unknown makes it difficult to quantify their compressive strength, leaving no clear method for anticipating an acoustic response. Virtually all of the acoustic devices in use today, when used for any application other than borehole imaging, were developed to quantify the ability of cement in the casing-formation annulus to provide a pressure barrier between zones connected to one another by the wellbore. In every such case, the cement used to provide the isolation is of a known chemical composition and extensive laboratory experiments are conducted to precisely measure its compressive strength and other properties. Since there exists no such opportunity to measure the properties of the material in an uncemented annular space, theoretical solutions have been developed which estimate the extent of adhesion these materials cause. This paper discusses the applicability of such theoretical solutions and substantiates its conclusions with case studies.
Application of Beam Pumping Wells’ Energy-Saving Rebuilding Techniques in Daqing Oilfield
Authors: Wang Fengshan , He Liu , Wanfu Zhou , Guochen Shi , Gang Cao , Ruiqing Chang , Deshi Zhang , Dingming Lin 
Published: October 2009

Abstract
Daqing Oilfield is the largest continental oilfield of China. And beam pumping system was the main artificial lift method of the oilfield. Till the end of 2008, the number of producers has reached more than 48,000 in the whole oilfield, in which 80% wells applied beam pumping system. Statistics indicated that, the averaged efficiency of beam pumping systems was only about 25% for the whole oilfield resulted in large quantity of power waste. Moreover, the power consumption of beam pumping wells was about one third of the total power consumption of the oilfield development which was the largest part of operation cost.
In the past tens years, Daqing Oilfield invested huge funding to improve beam pumping equipments’ energy-saving techniques. And a series of energy saving rebuilding techniques were developed including two innovative beam pump units, three energy-saving motors, and two new control designs. This paper presented these energy saving techniques in details. Application in more than 2,000 producers indicated that the efficiency of beam pumping systems was improved considerably after using these innovative energy-saving rebuilding techniques.
Development and Real Field Application of Two Novel Upscaling Methodologies for Simulating flow in Heterogeneous Reservoirs
Authors: Rai Himansu , Chaudhri Masroor 
Published: October 2009

Abstract
Scale-up techniques are commonly used to coarsen highly detailed geological models with the objective of maintaining near well flow behavior and reservoir connectivity. Existing single phase permeability upscaling methods (ranging from purely Local, Extended Local, Quasi-Global and Global) suffer with limitations in maintaining both near well physics and reservoir connectivity. In this paper we address this challenge by proposing two novel methodologies for single phase permeability and transmissibility upscaling, wherein we combine the individual strengths of purely local and extended local methods in a very practical and efficient manner for capturing the reservoir connectivity and near well region behavior.
The first method is based on calculating the effective coarse scale transmissibility from an extended local method and calculating coarse scale permeability from a local method. The local method derived permeability is used to calculate the well PI and effective transmissibility calculated from extended local method is used as a derived property to override the transmissibility generated from purely local method. The second method is based on calculating the effective coarse scale transmissibility from an extended local method while preserving near well region properties using a LGR (local grid refinement) extracted from the fine scale model. The process of defining LGR around wells is fully automated.
These methodologies are applied to upscale real field simulation models used for well optimization for deepwater reservoirs. The new methods showed considerable improvement over other existing upscaling methods. Also, these methods are highly applicable for any well count and well placement optimization study as there is no need to perform any additional upscaling every time well location changes.
The proposed new upscaling methods provide a practical way of combining different strengths of existing local and extended local methods. They can be easily used in real field well placement and optimization studies as demonstrated, removing a practical limitation of other combination methods of requiring new upscaling to be performed every time well location changes during any well optimization study.
Dynamic Flow Simulation of a Well Clean-up Operation at the Åsgard Field
Authors: Krogh Espen , Mjaaland Svein , Sletfjerding Elling 
Published: October 2009

Abstract
Clean-up operations of oil and gas wells are carried out when newly drilled wells are started up and tested for the first time. An optimal clean-up can be important for the production properties of complex wells. As the clean-up process is highly dynamic in its nature, a conventional steady state approach for simulation is of limited value.
In the current work a clean-up case study of a dual branch long horizontal well at the Åsgard field was undertaken using a commercial transient multiphase flow simulator. Eleven production zones located along the main and lateral horizontal wellbores were modelled in detail with separate zone productivities (obtained from petrophysical data analysis) and different numbers of sand screens with inflow control device (ICD) in each zone. Simulations of different clean-up scenarios were performed prior to the real operation and the results were used to plan the clean-up. The simulations supported the decision to clean-up both the lateral and the mainbore simultaneously in one operation.
The operational data from the clean-up operation were compared to the model results and valuable data for tuning of the model were obtained. After tuning a good match between the simulation results and the operational data was obtained, also quantitatively.
The study confirmed that dynamic simulations can be a useful tool to predict and understand the behaviour of a clean-up operation.
Fracture Mapping in the San Juan Basin, New Mexico
Authors: Estrada Erick , Roberts Neale , Weijers Leen , Riebel Tom , Logan Steven 
Published: October 2009

Abstract
An infill drilling pilot test in the Lewis, Mesaverde and Dakota formations of the San Juan Basin, New Mexico, included microseismic and tiltmeter monitoring of fracture stimulations. This study looks at microseisms from eight stages in two wells using an 18-tool stacked toolstring and surface tiltmeter measurements of 23 stages in six wells, (including the microseismic wells), using a 63-site tiltmeter array. A pressure observation well also situated within the pilot area, provided key information to the interpretation of data from the Lewis fracture stages. Complex (dendritic) fracture growth observed in the Lewis formation may be controllable through modification of the injection rate. Lower injection rates encourage simple planar growth and control fracture-height growth. Shorter fracture half-lengths were observed in the lower Mesaverde stages, leading to a redesign that is currently being tested in the field. The average fracture azimuth measured in this project, N21°E, confirmed the current understanding of the stress orientation in this part of the San Juan Basin and provided confidence regarding additional infill well placement.
The Quest for Energy in the Black Sea
Authors: Antonini Massimo , Kasparian Krikor 
Published: October 2009

Abstract
The quest for hydrocarbons in the Emerging Countries has always been one of the main reasons for the expansion of the Energy Companies.
Areas where opportunities are still to be completely understood, unlocked and exploited are the Countries facing the Black Sea shores, mainly Bulgaria, Romania, Turkey and Ukraine. In the past few years the drilling activity has rejuvenated due to the increase in the energy demand for both the local populations and the growing industry: Energy Authorities have set their goals wanting to become more independent on hydrocarbons supplies from the Russia. In recent years a few small energy companies have started to look into this area of opportunities also with drilling activity supported mainly by economically viable discoveries in the gas field lying under the Black Sea. After years of absence, the Major Companies have also started to look into this area as to become one of their working arenas.
Background political and economical situations dictate the recent moves into the Black Sea: Ukraine is always struggling against the Russian giant to have its energy needs fulfilled, Romania and Bulgaria have joined the Euro-zone in 2008 with the urge of developing their economies having at present dimensions a few folds lower than the most industrialized European Countries; finally Turkey has been for the last two decades a wannabe of the European Community. All four have strong reasons to be energy independent, also for detaching from a long established mark of underdeveloped Countries
Stimulation Results and Completion Implications from the Consortium Multi-well Project in the North Dakota Bakken Shale
Authors: Olsen T. N. , Gomez E. , McCrady D. , Forrest G. , Perakis A. , Kaufman P. 
Published: October 2009

Abstract
Stimulation Results and Completion Implications from the Consortium Multi-well Project in the North Dakota Bakken Shale
After a great deal of success with Bakken open hole horizontal completions in Richland County, Montana between 2002 and 2005, operators began to move to the more aerially extensive, yet heterogeneous North Dakota side of the Bakken play in the Williston Basin. However, the early results in the North Dakota Bakken were much more variable than the Richland County Bakken wells. With the huge resource at stake in North Dakota, it was realized that better understanding of the nature of the formation's transmissibility, completion, and stimulation efficiency could shorten the learning curve on the economic exploitation of this important oil resource. For this reason a consortium was formed with seven operators, a major service company, the state of North Dakota, and the DOE to drill and complete three science wells. Extensive vertical and horizontal log and core data were collected in these wells. Two wells were completed and one well was utilized as a monitoring well. During the stimulation several seismic arrays were deployed to map out the micro seismic events, including the largest seismic array ever deployed in a horizontal well. In addition, multiple radioactive isotope (RA) and fluid chemical tagging were employed.
This paper presents some of the results of this project and the completion analysis that was done with this data as well as other released data in the Williston Basin. In addition, some conclusions are drawn on the nature of fracture initiation along the wellbore and an attempt is made to provide some insight to the completion optimization.
Characterization of Hydraulically-Induced Shale Fracture Network Using an Analytical/Semi-Analytical Model
Authors: Xu Wenyue , Thiercelin Marc , Walton Ian 
Published: October 2009

Abstract
A model describing hydraulic fracture network growth is presented in this paper. The model is fully constrained by accounting for mechanical interactions between injected fluid and fracture walls and among nearby fractures and by satisfying observation data including wellbore pressure and microseismic event distribution. It may be solved analytically or semi-analytically, depending on whether a quasi-steady approximation is made.
The mathematical framework of the model is first discussed to certain detail. The model is then applied to a Barnett Shale case to illustrate the procedures of characterizing a hydraulically induced fracture network via inverse modeling and predicting the growth of the fracture network using forward modeling. Detailed information including fluid pressure, fracture width, fracture permeability, fracture volume and the surface area of fracture walls are also obtained during the course of modeling. It is further applied to carry out parameter sensitivity analysis. Its potential in realtime applications is also discussed.
Design Criteria and Application of High-Density, Brine-Based Fracturing Fluid for Deepwater Frac & Packs
Authors: Qiu Xiaoping (Victoria) , Martch Eddy , Morgenthaler Lee , Adams Jerry , Vu Hiep 
Published: October 2009

Abstract
Completing deepwater Gulf of Mexico (GOM) wells with depths greater than 20,000 ft and high geopressure may require the use of higher-density fracturing fluids to reduce high wellhead treating pressures. In Shell's Deimos field, frac fluid density of up to 12.5 ppg was required. Although the industry has pumped 11.5 ppg NaBr-based borate cross-linked fracturing fluids, a 12.5 ppg NaBr-based borate cross-linked fracturing fluid has not been used until now. There are many challenges when applying a 12.5 ppg NaBr-based borate cross-linked fracturing fluid.
The 12.5 ppg NaBr high-density, brine-based fluid has significantly different rheological behaviors than typical fracturing fluids made with freshwater or low salt concentrations. The high-density, borate cross-linked fluid responds very differently to shear history and recovers much more slowly than does freshwater-based fluid. Breaker efficiency is also very different. The high-density, brine-based fracturing fluid is potentially incompatible with formation crude. Base brine quality was also critical to final fluid quality and quality control procedures had to be better defined.
Shell developed lab and field QA/QC protocols to ensure the fluid met the frac & pack job requirements. With rigorous fluid testing and optimizations, three wells in the Deimos field were successfully completed in 2007.
This paper summarizes the extensive rheology, fluid compatibility, fluid optimization, and fluid QA/QC processes. It also summarizes important aspects in the application of 12.5 ppg NaBr-based fracturing fluids. This paper will also discuss friction pressure, treatment pressure, actual frac & pack job performance, and postjob production data. The fracturing fluid design and test methodology applied in these three Deimos wells are also very beneficial to design and optimization of other kinds of fracturing applications.