bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Experimental Investigation of Spontaneous Imbibition in Gas Shales
Authors: Roychaudhuri B. , Tsotsis T. , Jessen K. 
Published: October 2011

Abstract
Multi-stage horizontal wells play an important role in the development of domestic shale-gas resources. The completion strategy for shale-gas wells commonly includes hydraulic fracturing that utilizes large volumes of fresh (and recycled water) complimented by the addition of assorted chemicals. A general observation from the completion of shale-gas wells is that a large fraction of the injected water remains in the formation after flowback, and that the fluid loss from any single well can exceed 50% of the original injected volume. In this work, we study spontaneous imbibition of water into shale samples from the Appalachian Basin in order to explore the role of capillarity in the fluid-loss mechanism. We investigate the imbibition characteristics for a range of shale samples encompassing the mineralogy and petrophysical properties that can be observed along the vertical column of a gas play.
Imbibition experiments are performed on shale cubes, whereby one face of the sample is exposed to water in order to mimic the invasion characteristics of the fracturing fluid from the main hydraulic fracture through the micro-fracture network into the shale matrix. In most of the experiments we observe a distinct transition from an initial linear rate (vs. square root of time) to a much slower imbibition rate at later times. This transition is attributed to the complex, multi-porosity nature of the shale samples which are characterized by a micro-fracture network imbedded in the sample matrix. Based on a scaling argument, we demonstrate that the fluid loss during hydraulic fracturing can be explained, at least in part, by the imbibition processes.
Validation Process for Human Factor in Complex Upstream Oil and Gas Operations
Authors: Ershaghi Iraj , Luna Dennis R. 
Published: October 2011

Abstract
During drilling, completion and production operations, engineers and work crew often encounter critical situations requiring rapid decision making with insufficient information about their root causes while facing unknown consequences. Of concern is their experience and training to handle crisis management and in meeting the appropriate standards of care for the health and welfare of the workers and as well as their social and business responsibilities. The petroleum industry has been keen to exercise and mandate zero tolerance in oilfield accidents. Major operators, most large size independent and national oil companies have each adopted in-house standards and certification of their engineers and workers. In spite of these efforts, the industry continues to receive criticism when it comes to human and environmental safety issues. The nature of oil industry is becoming such that one act of mishandling of a crisis situation by any size company can have a drastic impact on the entire industry. We discuss the necessity of step changes in adopting universal standards for validation of the experience and training to successfully manage a crisis situation using advances in Information Technology as a means of enhancing trustworthiness of global upstream operations.
Practical Aspects of In-situ Ball Seat Milling
Authors: Halvorsen Helge , Arnskov Michael Macdonald 
Published: October 2011

Abstract
A ball seat placed deeply in one of the wells in the North Continental Shelf (NCS) had to be removed as part of a reconfiguration work-over. To achieve this, a milling operation scheme was devised. As this was the first time a ball seat of this type had to be removed by milling in the NCS the operation was rehearsed and evaluated onshore.
An identical setup with two sizes of seats and balls was established in an almost horizontal pipe setup onshore and the toolstring consisting of a conveyance tractor mounted with a milling device fitted with a tungsten carbide bit was driven into the pipe. The milling was carried out with different levels of weight on bit by adding back-tension on the cable as well as using different numbers of drive sections on the tractor. Then the results were evaluated. Additional tests were carried out with parts of a milled ball dropped down hole on the ball seat to ensure that milling could be done. The tests showed that the tool-string as configured could mill out the ball seats in one operation. This was later confirmed as the actual seat situated at 12.647 ft. measured depth was removed in one run. The paper provides a detailed account of the preparations and actual milling operation, including the lessons learned and how the objectives were achieved.
A Workflow Concept To Characterize Core Samples From The Microscale To The Nanoscale
Authors: Lemmens Herman , Butcher Alan 
Published: October 2011

Abstract
Increased interest in shale and tight gas reservoir characterization has sparked the adoption of novel techniques to go down to the nanometer scale. Typically, the smaller the features of interest are that can be resolved, the smaller the field of view becomes. This inevitably leads to concerns about representativity and upscaling.
Estimating reservoir quality in gas shale for example requires a good understanding of pore structure and pore connectivity. Gas shales are known to contain finely-dispersed porous organic matter within an inorganic matrix. The porosity within the organic phase has pore and pore throat dimensions typically below 100 nanometers and even down to just a few nanometers. For direct visualization of the pore network, FIB/SEM is the only technology with nanometer resolution in three dimensions. Field of view typically is only 10 to 20 microns.
Mineral characterization at the micron scale by Automated Petrography based on SEM/EDX analysis can image the full core surface; but lacks the resolution to visualize the small pores. Large area imaging creates images the size of the EDX maps but with the resolution used in the FIB/SEM dataset. Smart choice of the FIB/SEM location can be done on these images to obtain statistically relevant 3D datasets.
An example is presented of a piece of Marcellus shale imaged at different length scales.
Analysis of Transient Well Tests Affected by Wellbore Storage, Skin, and Short Injection/Production Time
Authors: Fuentes-Cruz Gorgonio , Camacho-Velázquez Rodolfo , Vásquez-Cruz Mario 
Published: October 2011

Abstract
The well test analysis techniques of falloff and buildup tests usually assume that at the end of the period of injection or production, the wellbore storage effect is negligible; nevertheless, this assumption is not always valid in impulse tests due to the short duration of the flow time. This situation is important in low mobility reservoirs, where the wellbore storage effects may last hours or days.
In this work, impulse tests are studied for the cases in which the period of injection/production is dominated by the wellbore storage effect. New equations are presented and it is demonstrated that the conventional expressions, existing for decades in the technical literature, must be modified since it is not feasible to apply them under these operational conditions.
Based on the results presented in this work it is concluded that in general, the pressure response of the unit slope period observed at early shut-in times, depends not only on wellbore storage coefficient and rate, but also on the formation transmissibility, skin factor, injection/production time, and the parameters that intervene in the definition of the dimensionless wellbore storage coefficient. In addition, guidelines are proposed for the impulse tests analysis, which combine the use of the shut-in pressure change, the superposition time pressure derivative, and the second drawdown derivative response.
With the aim to illustrate the validity of the new approximations, several cases of tests with short time of injection/production are shown, in such a way that it is possible to identify situations for which the classical expressions of well test analysis are not valid and must be substituted by the equations introduced in this work.
Stimulating a Barefoot Completion with Multiple Sand Fracture Treatments Using an Inflatable Packer Straddle System
Authors: Campbell C. , Brooks R. T. , Davis T. 
Published: October 2011

Abstract
A new method to create multiple fractures in a barefoot completion with a sand fracture treatment has been successfully deployed in Canada. This new method, utilizing an inflatable packer straddle system, has allowed all potential pay intervals to be effectively stimulated, as compared with traditional methods. This new approach of stimulating the open hole, without having permanent packers and frac sleeves or a cemented liner has resulted in reduced completion costs and improved production results.
In an effort to effectively, efficiently, and affordably stimulate these wells proven technology was modified to perform sand fracture treatments without depending on a liner. The system can be deployed on jointed pipe or coil tubing. The Bakken Formation in Southeast Saskatchewan and Southwest Manitoba was a prime candidate for trial testing due to the low treatment pressures and sand volumes.
Most recently the two typical completion methods in the Canadian Bakken use either open hole mechanical packers with ball activated frac sleeves, or cemented liner and hydrajet perforations placing the fracture treatment with coil tubing.
One of the primary concerns about the conventional liner methods is assurance of knowing where the fracture is being placed. There is no way to determine that there was adequate annular isolation to ensure where any of the planned fracture treatments were placed. Using a straddle system with a five meter (16.4 feet) interval allows the operator to know exactly where the fracture was placed in the reservoir.
Knowing the location of the fracture can provide clarity when analyzing production results. Producing as a barefoot completion may add incremental production from naturally fractured intervals that otherwise would have been sealed off with cement. Additionally, a barefoot completion provides flexibility for interventions or adding additional laterals since there is no liner that creates a restriction.
Main considerations of how the tool was developed to resist erosion and how the tool operates will be discussed. Case histories will be presented highlighting the job procedure as well as the economic advantage of using the inflatable packer straddle system. Reductions in completion and stimulation costs of 40% less than a liner completion have been achieved.
Practical Justification for an Empirical Approach to Probabilistic Undeveloped Reserve Bookings In Resource Plays
Authors: Dobson M. L. , Lupardus P. D. , Lee W. John 
Published: October 2011

Abstract
This paper is the third paper in a three part series which collectively presents a new practical method for probabilistic reserve evaluation under the recently released Modernization of Oil and Gas Reporting Rules by the Securities and Exchange Commission (SEC) (SEC 2009). This paper is focused on a methodology to validate the new stochastic booking method outlined in the first two papers of the series. When major changes are contemplated for key systems within a company it is critical to evaluate those changes prior to implementation. Moving to a new method of reserve evaluation and reporting could potentially have major implications for almost any oil and gas company. Internal uses of the reserve report as well as legal requirements of disclosure to regulatory agencies and governing bodies elevates the need to understand the scope of the modifications before they are adopted.
This paper presents an approach wherein the evaluator can test the proposed probabilistic methods against the actual field data. The test is used to predict the repeatability and reliability of the results. In essence, it applies an empirical approach to insure the technique meets the SEC requirement to be considered a reliable technology. When this approach is conducted over independent units of time and distinct spatial areas the repeatability of the answers supports the robustness and confidence needed to meet the requirements of the Modernized Rules.
Theoretical Proved Undeveloped (PUD) bookings were created using the new stochastic method for specific locations for a prior time period; those results were compared to actual post production proved developed producing (PDP) well estimated ultimate recovery (EUR) results for the same locations. Results for a specific case history are presented. The PDP results are in aggregate slightly greater than the aggregated PUD bookings. The new method constitutes a reliable technology and this paper outlines an approach to test the method prior to implementation in a company's work flow.
Theoretical and Experimental Modeling of Residual Gel Filter Cake Displacement in Propped Fractures
Authors: Ouyang Liangchen , Yango Takwe , Zhu D. , Hill A. D. 
Published: October 2011

Abstract
Fracture fluid damage caused by residual polymer gel in propped fractures results in low fracture conductivity and short effective fracture length, sometimes severely reducing the productivity of a hydraulically fractured well. The residual gels are concentrated in the filter cakes built on the fracture walls and have much higher polymer concentration than the original gel. The residual gel exhibits a higher yield stress, and is difficult to remove after fracture closure.
In this work we studied polymer gel behavior in hydraulic fracturing theoretically and experimentally. We developed a model to describe the flow behavior of residual polymer gel being displaced by gas in parallel plates. We developed analytical models for gas-liquid two-phase stratified flow of Newtonian gas and non-Newtonian residual gel to investigate gel cleanup under different conditions. The concentrated gel in the filter cake was modeled as a Herschel-Buckley fluid, a shear-thinning fluid following a power law relationship, but also having a yield stress.
The model developed shows that three flow regimes may exist in a slot, depending on the gas flow rate and the filter cake yield stress. At low gas velocities, the filter cake will be completely immobile. At higher gas velocity, the shear at the fracture wall exceeds the yield stress of the filter cake, and the gel is mobile, but with a plug flow region of constant velocity near the gas-gel interface. Finally, at high enough gas velocity, a fully developed velocity field in the gel is created.
The parameters for the gel displacement model were evaluated by experiments. We examined the filter cake formation by pumping the fracture fluid through a conductivity cell, allowing leakoff to build the filter cake, measuring the cake thickness, and flowing gas through the cell to simulate the cleanup process. The results show that the yield stress of the residual gel plays a critical role in gel cleanup.
New Mixer System Enhances Saudi Aramco GOSP Crude-Water Separation Performance
Authors: Boudi Adnan A. , Linga Harald , Al-Johar Zaki A. , Al-Yousef Khaled K. 
Published: October 2011

Abstract
The paper concerns the achievement in separation performance by using a new mixer device for the injection and mixing of the demulsifier into the crude-water flow.
The target for the injection of the demulsifier into the crude-water flow is to modify the surface properties of the crude-water interfaces such that the conditions for droplet-droplet coalescence for the dispersed phase within the two liquid bulk phases are improved. The costs for such production chemicals may become significant at the same time as the impact on the crude-water separability may be non-satisfactory. Facing this, Saudi Aramco has installed and field-tested a new mixer system, denoted ProMix, for more efficiently distributing the demulsifier into the crude-water flow, targeting lower consumption and improved separability.
The operational performance and results for the full scale 20" mixer installation at UGOSP-4 (Uthmaniyah Gas-Oil Separation Plant), normal operating flow rate 275,000 BPD, has been recorded both for winter and summer conditions.
Compared to the existing mixing valve, the ProMix mixer device has served to;
Reduce the demulsifier consumption Improve the crude oil produced water separation Reduce the pressure drop across the mixer installation to typical 1-2 psi Improve operational robustness
The annually averaged reduction in demulsifier consumption has been estimated to 20 %. In addition the oil-inwater content for the water separated from the dehydrator has dropped significantly by the use of the new mixer system, allowing for improved operation of the crude-water interfacial level for the dehydrator. For the operational robustness the introduction of the new mixer system has also served to minimize the dehydrator electrostatic grids failures during the winter conditions.
The reduced pressure drop and improved separability also allows for higher crude flow production in addition to reduced demulsifier consumption. As the ProMix is a compact flange mounted spool piece unit it can easily replace an existing choke or globe valve mixer in order to debottleneck existing separation trains, in addition to serve as mixer units for grass-root installations.
The United Nations Framework Classification for Fossil Energy and Mineral Reserves and Resources 2009
Authors: MacDonald D. , Lynch-Bell M. , Ross J. , Heiberg S. , Griffiths C. , Klett T. 
Published: October 2011

Abstract
Effective resource management in a globalizing economy requires accurate assessments of fossil energy and minerals resources. The recoverable quantities must be described and categorized in a manner that is consistent with scientific and social/economic information describing the economy as well as with the information describing the projects to recover them. A number of different standards have evolved over time in response to various professional needs
Under a mandate given by the United Nations Economic and Social Council, the United Nations Economic Commission for Europe (UNECE) has cooperated with Governments, regulatory agencies, industry, international organizations, and professional organizations (including Committee for Mineral Reserves International Reporting Standards (CRIRSCO), the Society of Petroleum Engineers (SPE), the American Association of Petroleum Geologists (AAPG), and the Society of Petroleum Evaluation Engineers (SPEE)), as well as with outstanding experts, to define a global classification for extractive activities (including oil, gas, heavy oil and bitumen extraction) that reflects the principal concerns of existing petroleum and mineral classifications.
The United Nations Framework Classification for Fossil Energy and Mineral Reserves and Resources-2009 (UNFC-2009) aims to serve the following four principal needs:
The needs in international energy and mineral studies to formulate robust and long-sighted policies. The needs of governments in managing their resources accordingly, allowing market prices to be transferred to the wellhead with as little loss as possible. The industries’ needs for information while deploying technology, management and finance to secure energy supplies and capture value efficiently within the established frameworks to serve its host countries, shareholders and stakeholders. The financial community's need for information to allocate capital appropriately, providing reduced costs and improved long-sightedness through the application of lower risk-compensated discount factors.
The projects are categorised with respect to economic and social viability, project feasibility and maturity and uncertainty with respect to the quantities addressed. The categorisation of projects rather than of accumulations provides coherence with other critical management information such as production, cash flows, value and demand for various input factors.
This key aspect of UNFC-2009 reflects the critical relationship between the quantities that can be recovered economically and the recovery processes (projects) that must be implemented to achieve those recoveries. It facilitates the recognition of potential wastage of resources through flaring or inefficient recovery processes and therefore also the potential for improvement.
Nonlinear Gas Well Test Problems: A Generalized Perturbative Solution Applied to a Vertical Well near a Sealing Fault
Authors: Barreto Abelardo Borges 
Published: October 2011

Abstract
In transient real gas flow in porous media the fluid properties are pressure-dependent which makes the diffusivity equation nonlinear. The gas well testing literature shows few attempts to derive exact solutions that handle the nonlinearities analytically. Most of the published articles approach the gas well testing problem by finite difference schemes. More than 40 years has passed since the introduction of the pseudo pressure function that became the standard procedure to analyze field data from gas wells. The pseudo pressure function, however, do not completely linearize the flow equation, as it fails to account for the variation on the gas viscosity-compressibility product. Such variation is very often ignored without justification by assuming it constant during the time range of interest. Recently, a new generalized solution based on a perturbation technique, that properly takes into account all the nonlinearities, was derived. In this work, this general solution is applied to obtain an analytical expression for a vertical gas well near a sealing fault. It is shown that the characteristic doubling of the slope of the pressure versus time semilog plot observed for constant fluid properties also appears on drawdown test for gas reservoirs. The results obtained by this new solution procedure are compared to a finite difference model showing close agreement.
Statistical Evaluation of Reservoir Rock Type in a Carbonate Reservoir
Authors: Abedini Ali 
Published: October 2011

Abstract
Reservoir rock type determination is one of the main parameters for simulation and prediction of the hydrocarbon reservoir behavior. Hence, it is of great importance to use a method which is capable of determining the rock type accurately. In this study, some of the most useful methods such as capillary pressure, Leverett dimensionless J-function, Winland R35 method, Flow Zone Indicator (FZI) and Discrete Rock Type (DRT) were applied to samples from a carbonate reservoir to determine the various reservoir rock types. The sample set consisted of 265 routine core data and 18 data sets of capillary pressure versus initial water saturation; all were analyzed using the aforementioned determination methods. Results of this study showed that both capillary pressure and Winland R35 were not accurate enough to determine rock types for this carbonate reservoir, mainly because of the high heterogeneity in the reservoir rock properties. For the same reason, the Leverett J-function method was found to be problematic in normalizing all the capillary data into one unique curve. However, FZI and DRT methods successfully classified all data into four discrete rock types while satisfying the relationships between permeability and porosity for each of them. The calculated permeability data for each rock type classified by FZI and DRT methods were in good agreement with core permeability data.