bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Improved Model for Predicting High-Rate Cased-Hole Gravel-Pack Well Performance
Authors: Unneland Trond 
Published: December 2007

Abstract
In this paper, an improved analytical model for predicting high-rate gravel-packed well performance is presented. The recommended model is based on serial flow through the perforation tunnels filled with formation sand and gravel, and has been calibrated with field data from three major oil fields in the Norwegian sector of the North Sea. The effective tunnel permeability is found to be a function of original formation permeability and gravel size. A new correlation for the high-velocity coefficient as a function of effective tunnel permeability is also given. The model, combined with the new correlations, gives a satisfactory match between measured and calculated pressure drop. A guideline for predicting pressure drop in high-rate cased-hole gravel-packed wells is presented, aiming at improving the tools for performance prediction for future wells. With these tools, specific targets can be identified for improvements in wells, thereby ultimately increasing well production and field profitability.
Observed Variations in Hydrocarbon Reservoir Bacterial Populations with Temperature: A First Step in Modeling the Bacterial Populations of Hydrocarbon Reservoirs.
Authors: Wood Jonathan M. , Spark Iain S. C. 
Published: December 2007

Abstract
Anaerobic bacteria have been isolated from hydrocarbon reservoirs, varying in depth of burial from 3500ft to 15000ft, at temperatures up to 150°C. These bacteria can be introduced in to the reservoir as a result of drilling operations and/or injection water; however in many cases the bacteria are indigenous to the oilfield reservoir. These bacterial populations have been shown to vary with changes in temperature, affecting their type and bacterial by-products such as pyrite, biopolymer and hydrogen sulphide gas. Using this thermal information, it is possible to construct a model from the incubation of preserved oilfield core samples in various growth media at selected temperatures to determine those areas at high risk of microbial formation damage. This is only a simple first step model as there are many other factors, some only poorly understood, that can affect the growth rate of bacterial populations in a hydrocarbon reservoir such as nutrient availability, sulphide, nitrate, sulphur, hydrogen and phosphate content for example.
External Filter Cake Properties During Injection of Produced Waters
Authors: Ochi J. , Detienne J-L , Rivet P. , Lacourie Y. 
Published: December 2007

Abstract
The re-injection of produced waters for pressure maintenance becomes more and more attractive in the industry since the environmental regulations for rejection (sea, rivers, deep aquifers) are more constraining associated with increasing surface treatment costs. One important difficulty in this re-injection process is the ability to predict the impact of water qualities on well injectivities. This is mainly due to the poor knowledge in the mechanisms of porous media damage by mixtures of micronic solid particles and oil droplets which are the main components of produced waters. In a first attempt this paper does not deal with the matrix internal filter cake formation. It focuses on the external filter cake build-up and flow properties which are believed to have the larger impact on well injectivity over most of the well life. It is shown that the injection of micronic dispersed oil leads to compressible filter cakes with very low permeabilities in the micro-darcies range. The retention on the filter is amplified by oil agglomeration while oil passing through the filter is dispersed in particles smaller than the filter pore throats. They become finer and finer as the pressure increases and are able to migrate deeply within the reservoir without adverse internal injectivity effects. These results on synthetic oil emulsions are compared to a real produced water behavior.
The Redevelopment of a Mature Waterflood Through the Application of Horizontal Multilateral Drilling Technology in Preparation for Tertiary CO2 WAG Operations
Authors: Dollens Kimberly B. , Larson Dana C. , Anthony Terry L. , Howell David A , Jones Tim A. 
Published: December 2007

Abstract
Multi-lateral horizontal drilling technology has been employed since late 1996 in the mature carbonate waterflood of the Ratherford Unit, Greater Aneth Field, San Juan County, Utah, in preparation for the implementation of a CO2 Water-Alternating-Gas (WAG) tertiary recovery project, planned for initiation in 2000. The program of multi-lateral reentries of 21 existing producers and 24 existing injectors over a two-year period (late-1996 through late-1998) was comprised of 100 laterals targeting the highly-stratified layers of the Upper Desert Creek.
Miscible flooding of the low-permeability Pennsylvanian Upper Desert Creek Zone I has been shown by analysis of the adjacent McElmo Creek Unit to be economic only through increased vertical/areal sweep efficiencies and processing rate enhancements obtained by the application of horizontal injector-producer pairs. The results of this study were confirmed by the 1994 - 1995 Ratherford Unit horizontal injection well drilling program, the 1996 Ratherford Unit multi-lateral production well drilling program, and the 1995 horizontal CO2 pilot pattern in the adjacent McElmo Creek Unit.
This paper will review the basic geologic and engineering concepts behind the application of horizontal drilling technology within the Ratherford Unit, detail the multi-lateral techniques employed and process improvements made through time, and summarize the actual field results.
Integrating Core Porosity and Sw Measurements with Log Values
Authors: Weiss W. W. , Wo S. , Balch R. S. , Roe J. , Fagrelius K. , Kendall R. 
Published: December 2007

Abstract
Well logs and cores are used to define formation thickness, porosity, and water saturation. These data are required to design well completions and to prepare workover and reservoir management plans. The presence of shale (clay) in the pay zone complicates log interpretation. This paper presents a methodology utilizing a neural network to reconcile the differences between density log effective porosity and plug core total porosity values in a shaly, laminated Cretaceous sandstone.
Core plug measurements are typically taken in the better pay intervals and generally do not include the shale laminations evident in core photographs. Log measurements do include the heterogeneity that is evident in core photographs, but the log measurements represent an average of a 6-to-36-in. section that does not reflect the small scale variability. A multivariable correlating technique was used to associate gamma ray, density, and shallow and deep resistivity logs with core plug porosity measurements.
Core water saturation values were used to tune a shaly sand water saturation model. The sw model was used to choose between plug core porosity, density log porosity, or neural network porosity as the preferred measurement to use with induction log resistivity to estimate water saturation. The porosity and water saturation values were then used to construct bulk volume oil and bulk volume water logs that were combined to identify productive zones.
A case history format is used to explain the approach developed to correlate the four dependent variables measured by the logs with the core porosity and water saturation measurements. The subject field is an 80-well Gallup pool located on the southwest flank of the San Juan Basin of northwest New Mexico.
The high clay content of the Muddy Formation in the Powder River Basin is known for contributing to errors in water saturation estimates. If modern logs capable of resolving thin beds are not available, this methodology can be applied to the Muddy, the Gallup and other Cretaceous reservoirs in the Rockies that contain thin shale laminations.
Gas Condensate Well Test Analysis Using a Single-Phase Analogy
Authors: Xu Shaosong , Lee W. John 
Published: December 2007

Abstract
This paper shows that a simple, single-phase analogy using a standard dry gas pseudopressure transformation in interpreting transient buildup pressure data from a gas condensate well gives a good estimation of permeability. Under certain conditions, this method gives good estimates of damage skin, too. These results are not affected by average reservoir pressure.
We used a commercial fluid PVT package and an EOS-based compositional simulator to characterize the phase behavior of retrograde gases during reservoir depletion, to compare gas and condensate PVT properties in situ and at lab conditions, and to model a vertical well under varying conditions. Then we analyzed the simulated buildup transient pressure by using a single-phase analogy incorporating a radially composite model and compared the results with reservoir simulator inputs and outputs.
The numerical experiments using three actual fluid samples show that, during reservoir depletion, the vapor properties in situ are a function of pressure only, and correlate very well with z factor, gas molar density and viscosity obtained in lab constant composition expansion (CCE). The condensate PVT properties in situ depend on pressure, production mode and reservoir properties. But the effects of variables other than pressure are usually small and are constrained within a certain pressure range. As a rule, the leaner the retrograde gas, the smaller the deviations. As a practical matter, the correlations between condensate oil PVT properties obtained from lab CCE and the values in situ are also quite acceptable.
Our reservoir simulation showed that the pressure buildup responses can be classified into two types. In the first type, the shape of the pressure derivative suggests a well in a radially composite two-zone reservoir. In the second type, the pressure derivative suggests a well in a radial three-zone reservoir.
Our interpretation of 30 simulated cases using a radially composite two-zone model shows that a single-phase analogy gives a good estimation of permeability but underestimates condensate bank size. We cannot estimate damage skin from the first type of pressure response, but the estimation from the second type is acceptable.
Pore-Scale Modeling of Multiphase Flow in Fractures and Matrix/Fracture Transfer
Authors: Hughes Richard G. , Blunt Martin J. 
Published: December 2007

Abstract
We use pore-scale network modeling to simulate imbibition in fractures and the matrix/fracture interaction. We represent the fracture as a two-dimensional lattice of conceptual pores and throats. We allow flow in connected wetting layers that occupy roughness and crevices in the pore space. We model piston-like advance with a capillary pressure that accounts for the curvature of the meniscus due to the fracture aperture, as well as the curvature of the wetting front in the fracture plane. We show that the model gives results that are insensitive to the resolution or pore spacing of the network. To account for viscous forces, the wetting phase pressure is computed assuming a fixed conductance in wetting layers. This pressure, in combination with the local capillary pressure, is used to determine the displacement sequence. A matrix is incorporated by surrounding the two-dimensional fracture plane by a three-dimensional network of pores and throats.
We model multiphase flow in a real fracture using an aperture distribution obtained from CT scanning. The simulated saturation distributions agree with those measured using in situ imaging. We also study the matrix/fracture transfer in a large three-dimensional network.
Up-scaling of Multiphase Flow Functions Using a Steady State Flow Model
Authors: Virnovsky G. A. , Friis H. A. , Lohne A. , Skauge A. 
Published: December 2007

Abstract
A concept of multiphase up-scaling based on steady-state flow approach was introduced in Ref. 2. It enables efficient calculation of effective properties through a numerical solution of steady-state 2-phase flow equation in 1D. The extension of this concept, i.e. steady-state multiphase flow, on 2 and 3 space dimensions, is studied below.
We present a model for efficient direct up-scaling in 2 and 3D. The developed numerical model simulates steady-state multiphase flow in heterogeneous reservoirs with account for viscous, capillary and gravity forces at a given external pressure drop. We utilize the developed model to directly compute effective properties in 2D, and present examples that show the dependence of effective relative permeabilities and capillary pressure on the magnitude of the external pressure drop, and also study the convergence of the effective relative permeabilities and capillary pressures towards the viscous limit functions.
Experiments and Modeling of High-Velocity Pressure Loss in Sandstone Fractures
Authors: Skjetne E. , Klov Statoil, T. , Gudmundsson J. S. 
Published: December 2007

Abstract
In this study we measured high-velocity pressure loss over Bentheimer sandstone fractures with varying fracture widths. Direct measurements of the roughness showed that the fractures were self-affine. The new results support the rough fracture high-velocity pressure loss model. The high-velocity pressure loss was described by a Forchheimer equation with a dominating square term. The square term is a power law in fracture width, and the power is given by a roughness exponent. For low velocities the pressure loss was not described by the Forchheimer equation. In agreement with theory, there exists a weak inertia flow regime, which separates the Darcy flow regime from the Forchheimer flow regime. An expression for the incremental high-velocity skin of a pinched-out hydraulic fracture was derived. The skin is a power law in fracture width.
Oil Recovery in a Fracture of Variable Aperture with Countercurrent Imbibition: Experimental Analysis
Authors: Lee Jaehyoung , Kang Joo M. 
Published: December 2007

Abstract
A parallel plate model is widely used to simulate flow in a fracture due to simplicity of idealizing the fracture. However, a real fracture has characteristics of variable aperture in nature. To assess the effect of variable aperture in water flooding, we performed water injection tests through fractured samples initially saturated with oil.
A casting method is employed to obtain aperture distribution of real fractures. From these results, we represented the morphology of the fractures using statistical parameters such as mean, coefficient of variation (Cv), skewness (S), and an anisotropy ratio. Water is injected into unfractured sandstone samples with constant rate and into artificially fractured sandstones with an increasing flow rate.
We interpreted cumulative oil recovery curves from the fractured rocks using corresponding statistical parameters in the results. The results show that morphology of a fracture has a significant effect on oil recovery as well as water injection rate. As Cv and S increase, overall efficiency of oil recovery decreases. Anisotropy ratio affects the breakthrough time of injected water and overall oil recovery as significant as Cv. At lower anisotropy ratio such as less than one, early breakthrough and poor oil recovery have occurred. The effect of the statistical parameters is pronounced as injection rate increases. We observed a point where imbibition rate shows identity regardless of fracture morphology, if both flow rate of injected water and matrix characteristics are the same.
Truncation De-noising in Transient Pressure Tests
Authors: González-Tamez Federico , Camacho-Velázquez Rodolfo , Escalante-Ramírez Boris 
Published: December 2007

Abstract
Truncation noise affects the interpretation of transient pressure tests when the total pressure change is very small compared to the total measurement scale of the tool. There are situations, mainly in high permeability reservoirs, where the maximum pressure variation is of the order of one thousandth of the total scale of the probe. Noise greater than one thousandth of the total pressure change hides pressure signals related to the characteristics of the reservoir; even when the accuracy of the tool could achieve one part by million of the total scale. This situation makes almost impossible the interpretation with the logarithmic derivative.
It is demonstrated in this paper that the frequency spectrum of noise is in the same frequency band that frequencies associated to the reservoir signal. By using a fitting procedure and wavelets, the signal-noise ratio (SNR) of pressure tests with truncation noise is improved in most of the cases up to 8 dB. This situation is equivalent to measure the maximum pressure change of the reservoir with a tool of one bit of additional effective resolution. Greater improvements can be obtained when only Gaussian white noise is present in the pressure signal. This result offers the possibility to reuse old noisy derivative data logs, especially pressure tests from high permeability reservoirs. This contribution will permit to utilize derivative interpretation techniques in a more appropriate way.
The efficiency of the proposed filtering technique is demonstrated with synthetic and field data pressure tests.
Application of Tracers to Monitor Fluid Flow in the Snorre Field: A Field Study
Authors: Dugstad Ø. , Aurdal T. , Galdiga C. , Hundere I. , Torgersen H. J. 
Published: December 2007

Abstract
This paper discusses the applications of gas and water tracers in the Central Fault Block (CFB) of the Snorre Field in the North Sea. An extensive tracer program was initiated in 1993 to improve the understanding of the flow dynamics in the field.
The CFB of Snorre has been produced by WAG injection since 1994. The tracer program has involved 3 injectors and 4 producers. Tracers applied were perfluorinated hydrocarbons (PFCs) and SF6 as gas tracers. As water tracers tritiated water (HTO), chemical SCN− and radioactive S14CN− have been applied in addition to the new tracer 4-fluoro benzoic acid (4-FBA).
Results from this integrated tracer study have improved the understanding of fluid flow and WAG injection efficiency in the reservoir. The tracer program will be continued and will also be expanded to other fault blocks.
Investigation and Modeling of Complex Water Influx Into the Sandstone Reservoir, Khafji Oil Field, Arabian Gulf
Authors: Nishikiori Nobuo , Hayashida Yasuyuki 
Published: December 2007

Abstract
This paper describes the multi-disciplinary approach to investigate and model complex water influx into the water driven sandstone reservoir, which takes into account vertical water flux from the lower reservoir as suspected supplemental source.
The Khafji oil field is located offshore in the Arabian Gulf and two underlying Middle Cretaceous sandstone reservoirs are investigated to understand the water movement during production. Both reservoirs are supported by a huge aquifer and had the same original oil-water contact. The reservoirs are separated by a thick and continuous shale so that the upper reservoir is categorized as edge water drive while the lower reservoir as bottom water drive. However, water production was observed at the central up-structured wells of the upper reservoir in the period much earlier than expected, which makes the modeling of water influx complicated as it is difficult to explain this phenomenon only by edge water influx.
In this study, engineered reservoir description was first performed to investigate water influx into the upper reservoir. Pressure and production history was comprehensively reviewed, which diagnosed that there existed anomalous higher pressure area in the upper reservoir. Moreover, anomalous temperature profiles were observed in some wells in the same area. At the same time, watered zones were trailed through TDT time-lapse analysis by which front of watered zone and its thickness were evaluated by both qualitative and quantitative manner. In addition, 3-D seismic survey has been conducted recently for the field and faults passing through the two reservoirs were recognized. Therefore, as results of data review and subsequent investigation, conductive faults as supplemental fluid conduits from the lower reservoir were suspected. Pulse test was then designed and suspected communication between two sandstone reservoirs and conductivity of a fault are currently under investigation.
Finally, an improved full-scale numerical reservoir model was constructed to model complex water movement, which includes suspected peculiar water from the lower reservoir. Employment of two kinds of water influx -one is conventional edge water and another is supplemental water invasion from the aquifer of the lower reservoir through conductive faults-achieved water breakthrough match. Furthermore, complex nature of water movement in the reservoir was accurately modeled by use of precise classification of rock type and adoption of pseudo relative permeability accounting for upward increasing or decreasing trend of permeability.
Tidal-Force-Influenced Pressure Transients for Estimating Compressibility in a Fractured Reservoir
Authors: Chang Eric , Firoozabadi Abbas 
Published: December 2007

Abstract
Total compressibility in a fractured reservoir is estimated using the pressure response due to gravitational potential variations. Both the moon and the sun gravitational potentials are accounted for using the full expression by inclusion of longer-period components. The semi-diurnal and diurnal pressure data show substantial long-term variations. The gravitational potential also contains the same variation trend; the ratio between the potential and pressure has a fairly uniform value over successive cycles. The computed total compressibility is also fairly constant and independent of the cycle. Results show the effects of the time interval over which the pressure measurements are performed as well as the location.
Utilizing Acoustic Standoff Measurements to Improve the Accuracy of Density and Neutron Measurements
Authors: Minette Daniel C. , Molz Eric 
Published: December 2007

Abstract
An improved method of determining and reducing the impact of borehole size and standoff on the measurement of formation density and neutron porosity has been developed. The use of standoff based binning in the density tool provides the first simultaneous measurement of density and compensation at several different standoffs.
In addition to providing standoff binning for the density, the three axis caliper provides a robust measure of the borehole size. This borehole size is used to calculate both the borehole size correction and standoff correction for the neutron tool. Techniques for accurately making these corrections while rotating and while sliding will be given.
The advantages of this technique are observed in both laboratory and downhole formations. The laboratory work will include the techniques used to make the standoff measurement. They will also include comparisons of measurements made with and without standoff based binning. Once the response in the lab is established, field test logs will be considered. Densities obtained at different standoffs as well as the optimized density will be presented to provide a quantitative measure of the effects of standoff, as well as to demonstrate the accuracy of the optimized density measurement. The comparison of MWD neutron logs with wireline neutron logs provides a measure of the accuracy of corrections while sliding and while rotating. In this manner we will see several independent measures of the improvement in the accuracy of the density and neutron measurements afforded by the use of standoff based binning and the three axis acoustic caliper.