bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crosswell Electromagnetic Tomography in Unconventional Well Geometries
Authors: Wilt Michael , Zhang Ping , Safdar Muhammed 
Published: October 2011

Abstract
Crosswell Electromagnetic (EM) Tomography is a recently developed technology for interrogating the interwell formation resistivity from measurements in boreholes. The tomography data is used for reservoir characterization and for time lapse monitoring of waterflood and EOR processes. Measurements are normally made in vertical wells that encompass the target of interest and collected data are interpreted via computer based inversion.
Modern oil fields often use highly deviated and horizontal wells because they offer improved production and reservoir contact characteristics. These are difficult to use for tomography due to access and sensitivity issues. In addition, the models are in general 3D. In this paper we explore the extension of crosswell EM tomography to non vertical wells. In particular we examine tomography from horizontal wells (HH) and a horizontal-vertical (HV) well combination. Using examples from carbonate oil fields in the middle east we show that the horizontal tomography is an effective method so long as the reservoir has significant thickness compared to the interwell spacing. HV tomography is particularly interesting near horizontal injection wells to track reservoir conformance of the injectate. Numerical models show that this configuration has a good sensitivity to a variety of structures and processes but that the method is only effective for a limited distance along the horizontal well
The Effects of Fluid Hammer Tools on the Efficiencies of Coiled Tubing Plug Milling - A Comparative Best Practices Study
Authors: Schneider Christopher , Craig Steven , Castañeda Juan Carlos , Castro Luis 
Published: October 2011

Abstract
Horizontal fracture stimulated completions remain the de facto method of producing from shale formations. The vast majority of wells are completed using the "Plug and Perf’ fracturing technique which later requires either a drill string or coiled tubing (CT) with a positive displacement motor (PDM) to remove the composite plugs. An estimated 6,000 to 8,000 wells are completed each year, with between 100,000 to 140,000 composite plugs installed in them in the U.S. alone. In extended reach horizontal completions, plug removal using CT becomes less efficient since end load forces transmitted to the PDM from the coiled tubing decrease as well depth increases.
Currently many operators rely on ‘word of mouth’ to design and perform extended reach CT jobs, resulting in ‘non-engineered’ and poorly executed plug milling operations. However, one new method to extend the operating envelope of efficient coiled tubing plug milling utilizing a water hammer tool has gained significant momentum. Several water hammer tools are in common use and there is significant anecdotal evidence that their application has improved job efficiencies.
This paper reviews plug milling efficiencies and general best practices from milling operations conducted in shale formations across the US (Eagle Ford, Bakken, Haynesville, Barnett and the Marcellus). The scope will cover operations completed with three different fluid hammer tools and base cases conducted without these tools.
The paper will also discuss milling efficiencies, number of stalls, stuck pipe incidents, speed and frequency of wiper trips and fluid selection associated with plug milling operations. The authors believe that the information presented in this paper will provide relevant analytical data to assist operators in improving the overall efficiency of the completion process.
In-Line Water Extraction from Crude Oil using Compact Separation Technology
Authors: Wordsworth Carl , Beg Najam 
Published: October 2011

Abstract
Conventional bulk oil-water separation is usually undertaken using gravity separators, where the phases are allowed to separate over time using gravity. One consequence of this technique is that in order to allow a sufficient residence time for the two phases to separate, gravity separators, tend to be large vessels. The step change alternative to this traditional approach is to consider using a compact separator where a high centrifugal force is impacted on the two phases to bring about separation and in doing so reducing the residence time needed to separate the fluids. As a consequence of this approach not only are the separators size and weight significantly reduced but correspondingly its safety features are considerably enhanced due to the lower hydrocarbon inventory and design codes used.
Caltec have developed an in-line cyclonic separator that is designed to separate water from a water continuous oil-water mixture, the devices are capable of recovering up to 60% of the total water at a quality of 1000ppm or less. They are designed to pipeline or process pipework code; can be installed in-line; have a large turn down ratio; have enhanced separation of fluids if gas is present; can separate the fluids at full pipe line pressure and are a fraction of the size and weight of a conventional gravity separators.
Caltec's Water Extraction (Wx) technology has been extensively tested in its own laboratories at Cranfield, and at TUV NEL's multiphase test facilities in Glasgow. Work has also been undertaken both onshore and offshore but this data will not be published in this paper, but will be reported at a later date. This paper describes the water extraction technology and reviews the results of the trials undertaken. This paper also examines potential applications where compact in-line separation technology can be used in future developments.
A Modern Method for Using Databases to Obtain Accurate Solutions to Complex Reservoir Characterization Problems
Authors: Freedman R. , Anand V. , Zhou T. , Rose D. , Beekman S. 
Published: October 2011

Abstract
Many problems in reservoir characterization require the formulation and solution of an inverse problem. The definition of the inverse problem is the prediction of reservoir properties from measurements made on the reservoir. The most familiar example of an inverse problem is well log interpretation. Well logging involves the acquisition of various kinds of data for the purpose of predicting reservoir properties of the earth formations near the borehole.
Conventional inverse methods used in the industry today typically involve the constrained minimization of a weighted sum of the squared deviations between a set of measurements and a forward model equation or equations. The forward model equations are either empirically or theoretically derived equations. These equations relate the reservoir property to be predicted (e.g., saturation, permeability, etc.) to measurements (e.g., resistivity, T2 distributions, porosity, etc.). Adjustable parameters in the forward model equations are determined using a "calibration database" of laboratory measurements made on a suite of representative samples. This traditional methodology suffers from fundamental limitations that reservoir rocks and fluids are too complex to be accurately described by the simple idealized equations that are used today as forward models. Additionally, the forward models contain adjustable parameters which can vary over a wide range, thereby leading to additional inaccuracies in reservoir properties.
Our paper discusses a new model-independent inversion method that overcomes the limitations and inaccuracies of the conventional method. The new inversion method predicts reservoir properties without the need to use idealized model equations or to solve minimization problems. The new method divides the calibration database into input measurements (e.g., used for the predictions) and outputs (e.g., the reservoir properties to be predicted). The outputs are mapped to the inputs using model-independent mapping functions constructed from Gaussian radial basis functions (RBF). The RBF mapping functions are accurate representations of the functional relationship between the database inputs and outputs. The coefficients of the mapping function can be uniquely determined using the database. Once the coefficients are determined, there are no adjustable parameters.
The new method is applicable to a wide variety of reservoir characterization problems. The construction of the mapping functions is presented in detail. We apply the method to a challenging problem in nuclear well logging — accurate predictions of formation thermal neutron capture cross sections (sigma) from well logging data. Logs of formation sigma predicted using the conventional regression method and the new method are compared and discussed.
First Successful Field Utilization of Cuttings Re-Injection (CRI) in the Offshore Field of Saudi Arabia as an Environmentally Friendly and Cost Effective Waste Disposal Method
Authors: Ezell R. , Quinn F. , Chima J. , Baim A. 
Published: October 2011

Abstract
Environmental regulations for oil and gas companies have become increasingly stringent with particular focus on remote areas and environmentally sensitive terrestrial and marine locations and the preservation of natural habitats and resources. With this in mind, many regulatory agencies have adopted "zero discharge" policies requiring monitored disposal of all wastes generated from drilling operations. For designated drilling operations, the various waste streams include: drill cuttings, excess drilling fluid, contaminated rainwater, produced water, scale, produced sand, and even production and cleanup waste. Traditional practices range from onsite pit burial to temporary box storage and hauling of the waste products to a final disposal site. Environmental risks from accidental releases and gas emissions result in higher operating costs and present concerns and liabilities as disposal sites are often several kilometers (km) from the generation source.
Cuttings re-injection (CRI) is a safe and cost-effective alternative that provides permanent and contained disposal of drilling cuttings in an engineering-determined subsurface formation. CRI provides a reliable method for achieving "zero discharge" by injecting slurrified cuttings and associated fluids into hydraulically created fractures up to several thousand meters below the surface. This disposal technique helps mitigate environmental risks and future liabilities associated with potential surface contamination.
This paper outlines the first successful application of CRI technology in the offshore areas of Saudi Arabia as a cost-effective and environmentally friendly waste management technique. Details of CRI theory as well as best practices, challenges and lessons learned are presented in detail from initial engineering design to case study utilization. This high pressure CRI work was the first of its kind in the MENA region.
How Do We Achieve Sub-Interval Fracturing?
Authors: Augustine Jody R. 
Published: October 2011

Abstract
To achieve multiple transverse fractures in a horizontal well, ball-actuated stimulation-sleeve completions were developed as an operationally faster alternative to plug-and-perforate completions. However, ball-actuated stimulation sleeves have reached a physical limit for the maximum number that can be used in a well. Horizontal wells can be divided into approximately 20 independent intervals. The actual maximum number of intervals is dependent on several variables. The goal is to achieve an independent transverse (normal to the wellbore axis) fracture for each interval. Each interval is pumped separately.
To attain more transverse fractures per well, multi-entry stimulation sleeves were developed to subdivide the intervals. An interval consists of one traditional ball-actuated stimulation sleeve and one or more multi-entry stimulation sleeves located upstream of the traditional stimulation sleeve. Multi-entry stimulation sleeves are actuated, or opened, with a specific-diameter ball, and then the ball is released and lands on a traditional stimulation sleeve. Each interval is still pumped separately, and the fluid flows in parallel through each sub-interval (sleeve within the interval). The question to be answered is how can sub-interval fracturing be achieved while pumping through multi-entry sleeves in parallel? The ultimate goal is to achieve one transverse fracture per sub-interval.
Analysis results are presented that address several issues, specifically, the role of annular isolation between sub-intervals, methods to achieve sub-interval fracturing, and scenarios that result in only one fracture per interval.
Several options for the verification of sub-interval fracturing are discussed. Currently, plug-and-perforate completions with multiple clusters are used. The perforation clusters are pumped in parallel. However, there is more to be done to help ensure sub-interval fracturing or verify the effectiveness of the multiple clusters. Strengths and weaknesses of the verification methods for both multiple-cluster plug-and-perforate completions and multi-entry stimulation-sleeve completions are discussed.
Total Organic Carbon and Formation Evaluation with Wireline Logs in the Green River Oil Shale
Authors: Herron Michael M. , Grau James A. , Herron Susan L. , Kleinberg Robert L. , Machlus Malka , Reeder Stacy Lynn , Vissapragada Badarinadh , Burnham Alan K. , Day Roger L. , Allix Pierre 
Published: October 2011

Abstract
A well drilled in the Green River formation in Colorado on the Bureau of Land Management RD&D lease of American Shale Oil LLC (AMSO), provides an opportunity to compare core measurements and log-derived properties in a unique unconventional resource reservoir. The core was analyzed for matrix density, Fischer Assay, total organic carbon (TOC), mineralogy, and 58 inorganic elemental concentrations. Logs include neutron, density, gamma ray, resistivity, magnetic resonance, and inelastic and capture nuclear spectroscopy. The data from this well are used to demonstrate new methodologies to estimate the TOC content and Fischer Assay oil yield.
The TOC content is estimated in three ways. The first is a multitool petrophysical evaluation. The second is an estimation of kerogen from the difference between density and magnetic resonance (MR) porosities where MR porosity corresponds to the water-filled porosity and density porosity to the sum of kerogen-and water-filled porosity. The third method combines inelastic and capture nuclear spectroscopy log data to compute elemental concentration logs of total carbon, inorganic carbon, and TOC.
For comparison of core mineralogy and chemistry with log data, over 200 intervals of core from this well were sampled as 2-ft-long slabs that were ground and homogenized, approximating the vertical resolution of log responses. The agreement between the logs and core values for total carbon, total inorganic carbon, and TOC is very good. The TOC log is used to activate empirical relationships such as Fischer Assay oil shale grade from TOC, again with good results.
Casing-Running Analysis in Riserless Topholes
Authors: Samuel Robello , Gradishar John 
Published: October 2011

Abstract
Riserless drilling poses numerous operational challenges that adversely affect the efficiency of the drilling process. These problems include increased torque and drag, buckling, increased vibration, poor hole cleaning, tubular failures, poor cement jobs, and associated problems during tripping operations. Riserless drilling in deep and ultra-deep water, as well as drilling to deeper depths, requires improved models and comprehensive analyses, especially when larger-diameter casings are run and cemented in a deviated or directionally drilled tophole environment. Current methods that lack proper modeling will severely overestimate hookload values when casing strings are run in and underestimate in the pick-up load estimates.
A new modeling approach is proposed to calculate appropriate hookload values, as well as torque and drag. This method can model situations in which the drillstring/casing string is in open water or in openhole under various operating conditions. Both soft- and stiff-string models are used in the hookload estimates and in the wellhead side-loading calculations. Hookload calculations and buckling limitations for the scenarios in which casing and inner strings are run with drilling mud inside the inner string, seawater in the outer string, and pad mud in the hole below the mudline, are presented. The study indicates that the results are influenced by various parameters, including depth of the mud line, offset of the wellhead from the rig center, wellbore inclination, curvature, wellbore torsion, and angle of entry into the wellhead, as well as by the complexity arising from wind, wave forces, and ocean currents. This study compares simulated predictions with actual well data from wells from Angola and the North Sea and describes the accuracy and applicability of the model. It also presents several examples of surface casing-string failure.
Application of a Torsional Impact Hammer to Improve Drilling Efficiency
Authors: Deen Aron , Wedel Ryan , Nayan Abhijeet , Mathison Shaun , Hightower Greg 
Published: October 2011

Abstract
Several phenomena that negatively affect drilling efficiency are still commonly observed in practice. These phenomena can often be linked directly to the high torque required for a PDC bit to aggressively shear formation, and the difficulty of effectively transmitting such torque consistently to the bit. In highly transitional or conglomerate formations, the depth of cut and subsequent torque required for the bit to continuously shear formation fluctuates greatly, leading to the buildup and release of torsional energy in the drill string, commonly known as stick/slip. High speeds and vibration during the slip phase, combined with the heterogeneous and/or hard nature of the environment can cause damage to PDC cutters and other drill string components, resulting in reduced bit and tool life as well as poor rate of penetration (ROP).
A proprietary torsional impact hammer was tested in applications in Western Oklahoma and in the Southeast Arabian Peninsula where drilling efficiency was believed to be much lower than the theoretical limit. These applications were identified by high cost per foot drilling with roller cone and diamond impregnated bits, as well as known and expected high vibrations accompanying unsuccessful and inconsistent PDC testing. The case studies reveal the strengths and weaknesses of applying such a solution, and introduce a discussion on selection of applications where this solution is advisable. The balance of this paper will also describe how this solution has reduced drilling costs and changed the economics of drilling applications in Western Oklahoma and the Southeastern Arabian Peninsula over the course of the cases studied.
Characterization of Gas Dynamics in Kerogen Nanopores by NMR
Authors: Kausik Ravinath , Minh Chanh Cao , Zielinski Lukasz , Vissapragada Badarinadh , Akkurt Ridvan , Song Yiqiao , Liu Chengbing , Jones Sid , Blair Erika 
Published: October 2011

Abstract
The Nuclear Magnetic Resonance (NMR) response of gas in gas shale nanopores is different from that of bulk gas, where relaxation is dominated by spin rotation and diffusion is unrestricted. Gas shales are characterized by very low porosity and ultra low permeabilities. Their porosity is dominated by nanometer-scale pores in the organic kerogen that restricts diffusional motion, in addition to having very high surface-to-volume ratios that enhance surface relaxation. At high pressure, the gas exists as an adsorbed phase on the pore surface and as free gas phase in the pore interior. Thus, relaxation and diffusion properties of gas in gas shales are controlled by the combined effects of adsorption, enhanced surface relaxation, restricted diffusion and molecular exchange between the adsorbed and free phases. One of the biggest challenges is the understanding of such effects in order to determine the quantity of free and adsorbed gas from NMR data, and to devise novel techniques to log these unconventional plays. Proper estimation of fluid volumes also requires the knowledge of the hydrogen index for the gas restricted in the gas shale nanopores, which is yet another challenge.
The NMR responses of methane gas in Haynesville shale plugs cored from a well in East Texas, USA were studied in laboratory experiments using a 2 MHz NMR spectrometer at elevated pressures up to 5 kpsi. The effects of adsorption, surface relaxation and restricted diffusion have been characterized, and the hydrogen index of the gas has been measured. Mineralogy, elemental analysis and Brunauer-Emmett-Teller (BET) experiments have also been carried out on the same plugs to understand the formation characteristics. In the samples studied, faster relaxation modes (few tens of milliseconds) and slower apparent diffusion coefficients (an order of magnitude less than their bulk values) for the confined gas molecules in comparison to their bulk properties have been observed for the first time with the help of 2D-NMR experiments at high pressure.
It has been observed that the relaxation spectra for bound water and the gas in the small pores overlap. Additional information is required to resolve these two fluids. Subsequently, the diffusion dimension is investigated to resolve the various fluids in the nanopores. We formulate new relaxation and diffusion models for the interpretation of the dynamics of gas restricted in gas shale and propose that multi-dimensional NMR logging with pulse sequences optimized for gas shales be further tested in the field, to help quantify the total gas in place.