bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unsteady-State Water Influx in Elliptic and Anisotropic Reservoir/Aquifer Systems
Authors: Kucûk Fikri , Brigham William E. 
Published: December 2007

Abstract
This work investigates the behavior of elliptical and anisotropic aquifers. Solutions for the dimensionless cumulative water influx and rate of water influx are presented for a range of ae/be ratios (ae/be = ratio of the half-length of major to minor axes of the internal boundary ellipse). Tabular and graphical forms of the dimensionless cumulative water influx and influx rate are presented as a function of the dimensionless time for various internal boundary geometries ranging from ae/be = 1, which corresponds to a circle, to a ae/be = ∞, which corresponds to a line (linear system). It is shown also that, for long times, an elliptical aquifer/reservoir system can be treated as a radial system by using the effective radius presented here as a function of the ae/be ratio.
Integration of Multiphase Flowmetering, Neural Networks, and Fuzzy Logic in Field Performance Monitoring
Authors: Alimonti C. , Falcone G. 
Published: December 2007

SummaryThe usual approach to the interpretation of producing wells is based on mechanistic models for the simulation of steady-state and transient flow regimes. However, there are significant reservations about convergence problems, computational limits, the need for extensive tuning on field data, the instability of boundary conditions, the limited applicability of existing multiphase flow models, and the uncertainties associated with choke-valve models. The current industry standards are critically reviewed within this framework.The real-time monitoring of producing wells is recognized as the best way of optimizing field performance. Monitoring a producing well implies the ability to track any changes in fluid composition, flow rates, or pressure and temperature profiles in real time. Multiphase flowmetering (MFM) plays a key role in this scenario. Such information, combined with the critical analysis of historical data from the well itself or from analog wells, allows diagnosis of the system and prediction of future trends. However, field data per se do not necessarily generate knowledge. This is particularly true for large databases, which are difficult to manipulate to provide suitable inputs for wellbore simulators.This paper suggests how MFM, knowledge discovery in databases (KDD), and fuzzy logic (FL) can offer an alternative approach to analyzing producing wells. KDD is the automated extraction of patterns representing knowledge implicitly stored in large information repositories. Distributed, ad hoc field measurements (including MFM and downhole measurements) can be processed by means of data cleaning, data integration, data mining, artificial intelligence (AI), and pattern evaluation. FL can then manage the resulting information in terms of flow assurance and production optimization.The same techniques can also be extended to the reservoir and production network for an integrated approach to production-system analysis.
Optimized Design of Pipe-in-Pipe Systems
Authors: Hausner M. , Dixon M. 
Published: December 2007

Summary
Deepwater subsea developments must address flow-assurance issues, and these increasingly form a more critical part of the design. Pipe-in-pipe (PIP) systems, one of the options available in the designers’ toolbox for overcoming these problems, are recognized as thermally efficient, reliable, and proven technology for insulated, subsea transportation of wellbore fluids. Although extremely low U values are achievable, PIP systems come at a cost, with increased weight as a penalty for use in deepwater developments.
By applying an "inside-out" optimization process for the design of PIP systems, the top-tension loading on the surface vessel (installation or production) can be reduced significantly while minimizing procurement expenditure on raw materials. Specifically, the design optimization of each component reduces steel volumes as well as the overall outer diameter (OD) of the system.
This paper presents the methodology for optimized design of PIP systems and illustrates the potential cost savings in terms of raw materials and installation through a case study for a typical large west African field. Commercial savings related to surface platform hull costs also are presented for a case in which the development employs PIP in catenary risers.
Developing New Fields Using Probabilistic Reservoir Forecasting
Authors: Kabir C. S. , Chawathé A. , Jenkins S. D. , Olayomi A. J. , Aigbe C. , Faparusi D. B. 
Published: December 2007

SummaryLimited and uncertain geologic and engineering data at the onset of any new field development are the bane of reservoir characterization and simulation. The problem stems from the uncertainty in various model-input variables, such as reservoir connectivity, fluid viscosity, and endpoint saturations, to name a few. Given this scenario, an ad hoc, one-factor-at-a-time approach to earth and flow-simulation modeling cannot possibly yield unbiased information for making objective business decisions.This study presents three field cases in which both engineering and earth-model variables were varied in a systematic way to assess reservoir performance by use of the experimental design (ED) approach.Results of the field cases show that well requirements (both producers and injectors) turned out to be fewer than anticipated. Equally important, one case study showed that laboratory measurements could minimize uncertainty surrounding oil viscosity and endpoint saturations. At the same time, we learned that the preferred horizontal-well orientation was marginally superior to vertical wells in light of high reservoir anisotropy. In another case, stratigraphy, gas/oil contact (GOC), and aquifer strength became the primary variables for the full-factorial design after the initial screening. Here, we proved that the project could proceed because it met the minimum reserves criterion. Perhaps most importantly, all studies showed how to obtain unbiased information in far fewer flow-simulation runs than one would do using an ad hoc approach.
PDC Bit Classification According to Steerability
Authors: Menand S. , Sellami H. , Simon C. 
Published: December 2007

SummaryWith the emergence of rotary steerable systems (RSSs), the technical issue concerning bit design for a specific directional application has reappeared. Today, a bit must be specifically designed for use with a particular directional system: rotary bottomhole assembly (BHA), steerable mud motor, or RSS. The reason is that the bit must have the ability to respond properly and rapidly to a side force applied by the steering system to initiate a deviation. To do so, the bit must have a predetermined steerability compatible with the directional system to provide the optimum dogleg potential.The new generation of directional-drilling systems differentiates "pointing the bit" from "pushing the bit." As a consequence, the bit's directional response is a key factor that operators and directional drillers need to know to make a good adaptation between the bit and the BHA. However, at the moment there is no standard method for classifying bits by steerability and walking tendency.On the basis of a comprehensive analysis of the directional behavior of polycrystalline diamond compact (PDC) bits (numerical simulation and pilot and field tests), a simple methodology has been developed that defines and evaluates their steerability and walking tendency. This methodology is used to classify the PDC bits defined with their IADC bit profile codes.Because PDC bit steerability is mainly a function of the bit profile, the gauge cutters, and the gauge pad, some design recommendations are given concerning these three parts. For each IADC bit profile code, the bit steerability and walking tendency are estimated through some formulas linking only the heights and lengths of the cutting profile. Some guidelines are also given about the gauge-pad length and gauge-cutter characteristics to achieve improved steerability.This simple method based on geometrical criteria allows quick estimation of not only the PDC bit steerability but also the maximum dogleg potential achievable by the bit when it is coupled with the steering system.
A Generalized Wellbore and Surface Facility Model, Fully Coupled to a Reservoir Simulator
Authors: Coats B. K. , Fleming G. C. , Watts J. W. , Ramé M. , Shiralkar G. S. 
Published: December 2007

SummaryThe formulation of a black-oil or compositional fully coupled surface and subsurface simulator is described. It is based on replacing the well model in a conventional reservoir simulator with a generalized network model of the wells and facilities. This allows for representation of complex wellbore geometry and downhole equipment. The method avoids the inefficiencies and/or inaccuracies of other coupled models, in which wells and facilities are treated as separate domains or in which the global system is not solved simultaneously. Example cases demonstrate the performance of the model for cases with simple and segmented wellbores (with and without facilities).
Productivity Preservation Through Hydraulic Propped Fractures in the Eldfisk North Sea Chalk Field
Authors: Cook C. C. , Brekke K. 
Published: December 2007

Summary
The Eldfisk oil field is a high-porosity, low-permeability reservoir of soft chalk in the Norwegian North Sea. Commercial oil production from the Eldfisk field is dependent on well stimulations. To date, pseudolimited-entry acid stimulation (PLEAS) has been the standard completion technique. This technique initiates relatively high (5,000 BOPD) individual-well oil-production rates. Over time, however, many of the Eldfisk wells have experienced rapidly declining oil production characterized by wellbore skin increase and fracture closure. Solids production and casing collapse have also been problematic. In late 1997, an alternative completion technique involving four hydraulic propped-fracture stages was successfully executed in an Eldfisk horizontal well. This paper presents a simple methodology to evaluate sustained productivity enhancement of propped fractures vs. acid stimulations in soft chalk formations based on the use of analytical modeling in combination with empirical production-data analysis.
Effect of Oil Composition on Miscible-Type Displacement by Carbon Dioxide
Authors: Holm LeRoy W. , Josendal Virgil A. 
Published: December 2007

Abstract
This paper presents additional data related to the correlation between minimum miscibility pressure (MMP) for CO2 flooding and to the composition of the crude oil to be displaced. Yellig and Metcalfe have stated that there is little or no effect of oil composition on the MMP. However, their conclusion was based on experiments with one type of reservoir oil that was varied in C1 through C6 content and in the amount of C7+ present but not varied in composition of the C7+ fraction. We have found that the Holm-Josendal correlation, which is based on temperature and C5+ molecular weight, predicts the general trend of the MMP's required for CO2 flooding of various crude oils. MMP's were predicted with this correlation and then tested for several crude oils using oil recovery of 80% at CO2 breakthrough and 94% ultimate recovery as the criteria. We now have data showing that miscible-type displacement is also correlatable with the amount of C5 through C30 hydrocarbons present in the crude oil and with the solvency of the CO2 as indicated by its density. Variations from such a correlation are shown to be related to the C5 through C12 content and to the type of these hydrocarbons.
The MMP data were obtained from slim-tube floods with crude oils having gravities between 28 and 44°API (0.88 and 0.80 g/cm3) and C5 + molecular weights between 171 and 267. The crude oils used varied in carbon residue between 1 and 4 wt% and in waxy hydrocarbon content between 1 and 17%. The required MMP for these crude oils at 165°F (74°C) varied between 2,450 and 4,400 psi (16.9 and 30.3 MPa) for an oil recovery of 94% OIP. The MMP was found to be a linear function of the amount of C5 through C30 hydrocarbons present and of the density of the CO2.
Compositional Effects on Displacement Mechanisms of the Micellar Fluid Injected in the Sloss Field Test
Authors: Gupta Surendra P. 
Published: December 2007

AbstractThe performance of the micellar/polymer flood conducted in the Sloss reservoir did not follow predictions by a streamtube model. The model assumed that micellar flood displaces oil and water in a piston-type miscible manner with a final oil saturation of 5% PV, and sulfonate retention based on short-term laboratory adsorption tests. This paper, in conjunction with a complementary paper,1 describes process mechanisms needed to model the flood performance.The results of laboratory studies show higher sulfonate retention caused by ion-exchange effects, which result in partitioning of sulfonate into the oil phase and higher adsorption caused by long contact times. Long-term aging of the Sloss micellar fluid at the high reservoir temperature (93.3°C [200°F]) does not reduce oil recovery. The results of laboratory studies also show that the final oil saturation after micellar flooding is capillary-number dependent. A higher final oil saturation can be the result of reduced injectivity/productivity, increased interfacial tension (IFT), and/or decreased viscosity.This paper demonstrates that ion exchange, hardness, and sulfonate partitioning can significantly affect micellar-flood performance. The paper presents an experimental plan that provides information for optimizing the design of micellar/polymer floods. This plan, when applied to a specific flood, allows an investigator to examine effects of adsorption, ion exchange, hardness, and partitioning on flood performance. Specifically, phase studies and sulfonate requirements must encompass effects of in-situ-generated calcium ions as a result of sodium/calcium ion exchange. Sulfonate itself can increase the calcium content of the fluids because of a calcium/micelle association. High calcium concentrations can increase sulfonate requirements. Sulfonate adsorption requirements for micellar flood design are sensitive to the experimental procedures employed. The paper outlines improved procedures encompassing ion exchange and time effects and demonstrates that a favorable ion-exchange process can be used to reduce adsorption requirements.
A Comparison of Two-Phase Inflow Performance Relationships
Authors: Gallice Frederic , L. Wiggins Michael 
Published: December 2007

SummaryPetroleum engineers are routinely required to predict the pressure/ production behavior of individual oil wells. These well-performance estimates assist the engineer in evaluating various operating conditions, determining the optimum production scheme, and designing production equipment and artificial-lift systems.In this paper, commonly used empirical, inflow performance relationships for estimating the pressure/production behavior during two-phase flow are investigated. Relationships studied include those proposed by Vogel; Fetkovich; Jones, Blount, and Glaze; Klins and Majcher; and Sukarno and Wisnogroho. Each method is described briefly, and the methods used to develop the relationship are discussed.On the basis of actual vertical-well data, the relationships are used to predict performance for 26 cases. The predicted performance is then compared to the actual measured rate and pressure data. The variation between the predicted and measured data is analyzed, and from this analysis, an assessment is made on the use of inflow performance relationships and of the quality of the performance estimates.
A Closed-Form Hydraulics Equation for Aerated-Mud Drilling in Inclined Wells
Authors: Guo Boyun , Sun Kai , Ghalambor Ali , Xu Chengcai 
Published: December 2007

SummaryAccurate prediction of shut-in and flowing bottomhole pressures (BHPs) in inclined holes presents a challenge in aerated-mud drilling. It is highly desirable to develop a simple and accurate hydraulics equation for this purpose. This paper fills the gap.A closed-form hydraulics equation was developed in this study on the basis of recent experiments on multiphase flow in an inclined-well model. The newly developed hydraulics equation is a four-phase model that considers injected liquid, injected gas, formation-fluid influx, and cuttings entrained at the bottom of the hole during drilling. It degenerates to the Poettman and Bergman equation when terms for friction loss, cuttings weight, gas weight, and temperature variation are neglected.The equation was first calibrated with the data measured from a full-scale research borehole. It was then tested with two field cases covering a deep (7,403 ft vertical depth) and a shallow (697 ft vertical depth) horizontal well drilled with aerated muds. The results show 3.42 and 0.8% error of the equation in BHP prediction for the deep and shallow wells, respectively. The equation was also compared with two commercial software packages (S1 and S2) using the measured BHP from another well. It indicates that the flowing BHP calculated by the equation is comparable to that from S1 and much more accurate than S2. Sensitivity analyses with Eq. 7 show that the gas-injection rate affects "static" pressure more than flowing pressure in the annular space for the tested data range. The sensitivity analyses also indicate very high equivalent circulating density (ECD) and low equivalent mud weight (EMW) in shallow depths near the surface.
Inflow Performance Relationship for Perforated Horizontal Wells
Authors: Yildiz Turhan 
Published: December 2007

SummaryThis paper presents an investigation of perforated horizontal-well performance in areally anisotropic reservoirs. Theoretical investigation is based on a 3D analytical IPR model. The analytical IPR model considers an arbitrary distribution of perforations along the completed segments. Changes in flow rate, pseudosteady-state productivity, and cumulative production can be computed using the solution.The analytical IPR model was compared with the models available in the literature and verified. It was then used to investigate the effects of well and reservoir parameters on the inflow performance of perforated horizontal wells.
Productivity of Horizontal Wells Completed With Screens
Authors: Yildiz Turhan 
Published: December 2007

SummaryAn integrated flow model is developed to simulate the flow into horizontal wells with screens. The model is composed of a multisegment horizontal-well model and a near-wellbore model. The multisegment horizontal-well model predicts the pressure losses in a bounded reservoir. The near-wellbore model simulates the fluid flow through the damaged/collapsed zone around the wellbore, the mudcake, the wellbore/screen interface, the gravel-packed annulus, and the screen itself.Using the model, we investigated the effects of degree of screen damage, nonuniform damage removal, mudcake properties, and blank-pipe insertion on horizontal-well productivity. We examined and compared the long-term horizontal-well performance in terms of rate decline and cumulative production as a function of time.
The Effective Compressibility of Reservoir Rock and Its Effects on Permeability
Authors: McLatchie A.S. , Hemstock R.A. , Young J.W. 
Published: December 2007

Abstract
Results and experimental procedures are presented covering a preliminary laboratory investigation of the compaction of reservoir rocks and its effect on porosity and permeability.
"Effective" compressibility was measured by subjecting core material to an overburden load and reducing pore pressure. Preliminary results showed relatively high effective compressibilities which varied from 1.8 × 10(–6) pore volume/pore volume/lb/in. for limestones to 7.7 × 10(–6) pore volume/pore volume/lb/in. and even higher for sandstone reservoirs containing large amounts of fine clay material. It appeared from the initial results that the effective compressibility of the material could not be correlated directly with porosity and that other factors, such as the amount of clay material present might have to be taken into account. The work to date has indicated that effective compressibility factors will have to be measured for the particular reservoirs being studied.
Oil permeability of core material was measured under various effective overburden loads from 0 to 8,000 psi. It has been found that reduction of permeability in clean sands was relatively small and the results agreed with published data. For sandstones containing large amounts of clay, preliminary tests indicated very large reductions in permeability with increasing effective overburden pressures. It is planned to continue laboratory work on this phase because of its importance in low-permeability reservoirs.

Introduction
During the past few years increasing interest has been shown in the differences obtained between conventional laboratory measurements on cores at atmospheric pressure and those when reservoir conditions are simulated. Since these data are used as the basis for calculations and the prediction of reservoir behavior, their evaluation under reservoir conditions is most important.
The effect of the compressibility of the rock upon the reservoir behavior, as fluid pressure declines, is an important subject which has been insufficiently studied. The total pressure on any plane through a reservoir is the result of the grain-to-grain rock pressure due to the overburden and the pressure of the interstitial fluid on the plane.
Finite Element Model Simulations Associated With Hydraulic Fracturing
Authors: Advani Sunder H. , Lee J. K. 
Published: December 2007

Abstract
Recently emphasis has been placed on the development and testing of innovative well stimulation techniques for the recovery of unconventional gas resources. The design of optimal hydraulic fracturing treatments for specified reservoir conditions requires sophisticated models for predicting the induced fracture geometry and interpreting governing mechanisms.
This paper presents methodology and results pertinent to hydraulic fracture modeling for the U.S. DOE's Eastern Gas Shales Program (EGSP). The presented finite-element model simulations extend available modeling efforts and provide a unified framework for evaluation of fracture dimensions and associated responses. Examples illustrating the role of multilayering, in-situ stress, joint interaction, and branched cracks are given. Selected comparisons and applications also are discussed.