bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geostatistical Reservoir Characterization Using Interwell Seismic Data
Authors: Justice J. H. , Woerpel J. C. , Watts G. P. , Waddell W. 
Published: December 2007

Abstract
Geostatistical techniques are currently finding widespread use in reservoir characterization. Most hard data which is available for use in geostatistical procedures is obtained at generally widely spaced production or injection wells. This fact makes estimation of spatial statistics for the reservoir rock difficult since the interwell volume is not directly accessible for measurement.
Interwell borehole seismic imaging technology is now reaching the point where high-resolution maps of seismic shear and compressional wave velocity fields can be constructed in the interwell volume between wells. Biot-Gassmann theory allows us to relate shear and compressional seismic velocities to porosity when additional rock properties are known or can be inferred.
Using data acquired in a shallow-shelf carbonate reservoir in the Permian Basin, as part of a DOE Class II Oil Project, we have used interwell seismic data to infer porosity distribution between wells. Using cross-plots, permeability distributions were also obtained. These were then used to directly estimate azimuthal spatial statistics for porosity and permeability in the reservoir. Geostatistical procedures were then used to build highly detailed 3-D reservoir models, using these spatial statistics. After a period of CO2 injection in the reservoir, similar techniques were used with monitor surveys to generate 3-D volume images of injected CO2 in the project.
A Direct Method for the Identification of the Permeability Field of an Anisotropic Porous Medium
Authors: Zhan Lang , Yortsos Yanis C. 
Published: December 2007

Abstract
In a recent publication1 we proposed a direct method for the inversion of the permeability field of an isotropic porous medium based on the analysis of the displacement of a passive tracer. By monitoring the displacement front at successive time intervals (for example, using a tomographic method), the permeability can be directly obtained from the solution of a non-linear boundary-value problem. In this paper we extend this approach to the case when the porous medium is anisotropic.
When the principal axes of anisotropy are known and fixed, a procedure is proposed, in which the tracer is injected two (or three) consecutive times along the two (or three) principal directions (for the case of a 2-D (or 3-D) problem, respectively). It is shown that the diagonal components can be obtained from the solution of two (or three) coupled boundary-value problems involving the experimentally obtained fields of arrival times. Numerical examples show that the method works well when the permeability variation is not very sharp (for example, for correlated distributions). When the permeability tensor is full and the principal axes vary in space, we propose a procedure involving the injection in three different directions (for the case of a 2-D problem). In principle, the components of the permeability tensor can be determined from the solution of three coupled boundary-value problems. However, the inversion method encounters significant numerical problems. For the case of small off-diagonal components, a practical procedure is proposed to decouple the problems in the inversion method for both 2-D and 3-D.
On the Quest for Ester-Base Mud System Impact on Data Acquisition
Authors: Lugol R. L. , Dodman C. A. , Crowe J. , Louis A. 
Published: December 2007

Abstract
Oil-Base Mud (OBM) systems have been used in the oil and gas industry for many years. Historically OBM systems have contained aromatic compounds. Environmental concerns linked to the use of OBM pushed the industry to develop Synthetic-Base Mud (SBM) systems with no aromatic content. This paper focuses on the use of ester-base mud (EBM). EBM was originally used in the top-hole sections of wells. It is now extensively used to drill the complete range of exploration, development, water source and water injection wells.
This paper will demonstrate that EBM has a significant impact on well measurements (FEWD and wireline logging, mud logging, coring, etc.) when compared to Water-Base Mud (WBM) or traditional OBM. Examples derived from offshore and onshore fields in Nigeria will be presented. Local efforts to investigate the effect of EBM, have been carried out in Nigeria by Oil and Service companies. These results seem to indicate that this effect causes a modification of the mud filtrate invasion profile within the formation and results in a complex interaction with the fluid in place. Adverse effects have been observed which have consequences on formation evaluation data and the subsequent static and dynamic reservoir evaluation. A major concern is that Original Oil In Place (OOIP) calculations are systematically reduced. Therefore, on critical wells where formation evaluation is a key issue, the choice of such mud systems needs to be balanced with the potential loss of geological and petrophysical information and the anticipated reduction in drilling cost.
A comprehensive study, coordinated by a special interest group, needs to be initiated on a larger scale by the companies concerned. The objective of the study would be to understand the physics and chemistry of SBM on rocks and formation and develop corrections for log and core measurements. This study would benefit the worldwide users of SBM drilling fluids. This paper will discuss the observations and propose a program to better understand the phenomenon and improve formation evaluation accuracy.
Integration of Dynamic Data of Pilot Waterflood with Rock Fabric -Implications for the Full Field Waterflood Startup in Mauddud Reservoir, North Kuwait
Authors: Al-Ajmi Hussian Zayed , Mukherjee Raja , Chetri Hom Bahadur 
Published: December 2007

Abstract
The Mauddud limestone of Early Cretaceous is multi-billion barrel depletion drive reservoir undergoing re-development with a planned 260,000 BWPD seawater injection. Injection-production history and dynamic data integration with a static reservoir description of the two waterflood pilots illustrates much of what can be expected in the larger scale waterflood. Detail cross-sections were build incorporating geological, petrophysical, surveillance and production data to understand reservoir performance under water flood.. Geocellular models based on 3-D seismic and detail core sedementology was constructed and simulation was done to facilitate this understanding. Over the two and half years of Pilot life great variety of data were acquired which includes: extensive open hole logs including CMR/NMR, FMI and RFT, Conventional and preserved cores, core sedimentological and fracture study, Geochemical (Iatroscan & Residual Salt Analysis) analysis, Geomechanical & Reservoir stress analysis, interference testing, production and injection profile logs, time lapse pulse neutron logs, static bottom hole pressures and pressure build up surveys. Synergistic integration and interpretation of multidisciplinary pilot wells data, has given a detail insight of the controls of fluid flow in the reservoir and the understanding was carried forward to the full field development of Mauddud reservoir using I-9 spot pattern flooding.
The major controls on the pilot water movements are; 1) Facies variation and thief zones, 2) Injector conformance 3)regional reservoir pressure gradients around the pilots.
The pilots have proven the pressure connectivity on the larger scale (250 acre inverted 9 spot) through surveillance gathered outside the pilot patterns. This adds confidence to the predictions of flood performance success across the development area and confirms that the planned pattern flood is appropriate. Mechanism of water breakthrough was studied and potential sweep efficiencies in the relatively lower permeability facies were analyzed through production and pulsed-neutron logging and by in-fill drilling. The three vertical hydraulic units identified by field RFT data were confirmed by vertical sweep profile. The more depleted upper zone is the target of the existing pilots. These characteristics are expected in the larger scale waterflood and perforation strategy is designed to optimize conformance between injector and producer and to minimize early injection breakthroughs and maximize vertical and areal sweep efficiency. The observed time to water breakthrough, observed vertical and aerial sweep, and the controlling geologic description has been used to refine reservoir simulators allowing them to more accurately predict production and more importantly water-cut profiles and recovery factors for this important redevelopment.
Understanding Coning Performance in a High-Anisotropy Reservoir: The Burgan Reservoir Case Study
Authors: Kabir C. S. , Ma E. D. C. , Dashti Q. , Al-Shammari O. 
Published: December 2007

Abstract
Water cones largely dictate oil recovery in a typical bottom-water situation. Major parameters influencing coning include mobility ratio, producing rate, completion interval, and anisotropy. We conducted a systematic study to understand the influence of these and other parameters on coning. Our aim was to develop producing and completion rules for managing the Greater Burgan’s Third Middle Sand (3MS) reservoir in Kuwait.
The building blocks of our study were: (1) detailed geologic modeling using core and openhole log data, (2) geostatistical modeling for 3D sector modeling, (3) transient-pressure testing, (4) production logs, and (5) cased-hole saturation logs. Singlewell, 2D radial models were built to understand various elements of coning for existing completions. We also explored alternative completions to mitigate coning. The study included the use of single- and dual-lateral wells and cone-reversal techniques. Follow up studies using a 3D-sector model confirmed some of the findings of single-well modeling.
Results show that high anisotropy provides near piston-like displacement and, consequently, completing at the top of the bed appears prudent in a vertical well. High producing rate tends to leave higher remaining oil saturation than those do at moderate rates. A combination of high-anisotropy and low- length-to-thickness ratio makes horizontal completions unattractive in the crestal area of the field.
Effects of Phase Behavior, Dispersion and Gridding on Sweep Patterns for Nearly Miscible Gas Displacement
Authors: Haajizadeh M. , Fayers F. J. , Cockin A. P. 
Published: December 2007

Abstract
In a previous paper, Haajizadeh et al [1] used compositional simulation to investigate the effects of physical dispersion, and short scale heterogeneities with consequent viscous fingering, on rectilinear displacement by nearly miscible gas. It was shown for near-miscible processes that the dispersive/fingering effects of heterogeneities in 2D-rectilinear flows could be matched quite well through use of an appropriately chosen grid size in an equivalent 1D-compositional model.
In the present paper, we extend this work by investigating 2D-areal sweep patterns for two different well configurations, using the same types of phase behavior. It is well known that areal sweep for first contact miscible (FCM) processes is unstable and difficult to compute with finite difference solutions; however, dispersion effects reduce the effective viscosity ratio for multi contact miscible (MCM) processes because of the departure from proper miscibility. Additionally, the presence of heterogeneities with short correlation lengths creates noise effects which also have an independent stabilizing influence. This can augment the benefits of loss of miscibility.
We show that there can be a "best" grid size in 2D-areal configurations to allow partial cancellation of errors associated with omission of short range heterogeneities. The optimum choice of gridding is found to depend on well positions in terms of diagonal or parallel gridding, and the type of phase behavior. In the absence of heterogeneities, fine grid near-miscible solutions with single point upstream weighting display strong grid orientation errors, which are improved by using a 9-point scheme. In the presence of heterogeneities, the grid orientation problem is much reduced and a suitably chosen coarse grid for a homogeneous problem can give an areal sweep shape similar to that from the 9-point fine grid with heterogeneities. We demonstrate that improvement in areal sweep resulting from the presence of heterogeneities can more than offset the loss of local displacement efficiency associated with degraded phase behavior.
We also report on some results for the dispersive nature of short range heterogeneities on vertical sweep pattern for a condensing/vaporizing drive in a vertical cross section, where there is a consequent broadening of the gravity override tongue. This can also improve recovery performance. We show that an appropriate size of gridding in a homogeneous model can again give some compensation for omitted sub-grid heterogeneities. The gravity override behavior is more sensitive to choice of the Δz- than Δx-interval, so there are prospects for choosing "effective" grid sizes to deal with sub-grid heterogeneities in both areal and vertical sweep aspects of a 3D-problem. However, selection of appropriate gridding for vertical sweep will also depend on other factors such as gravity numbers, asymmetry in correlation lengths, use of WAG etc.
A Low-Cost PET System for Use in Flow Experiments of Porous Media
Authors: Haugan Are 
Published: December 2007

Abstract
A low-cost two-dimensional PET system which can visualize tracer flow inside porous media has been constructed. It has thoroughly been tested, and successfully been used to image fingering inside porous media by using 22Na+ as passive water tracer. The system consists of two collimated NaI(Tl) detectors. During a scan the porous media is moved along a line perpendicular to the line between the two detectors with the help of a linear position table, and rotated around an axis perpendicular to the plane set by these two lines. The simplicity of the PET system almost completely eliminates the problems with Compton scattering, random coincidences, radial elongation and individual LOR efficiency. Thus, some of the problems with commercial PET systems are strongly reduced in our PET system. The developed PET system is modular, and consists primarily of components that are common in laboratories performing nuclear measurements. This made it a low-cost system, and may increase the availability of this imaging technique. It is concluded that PET has the ability to become a powerful tool in such studies.
Refracture Reorientation Enhances Gas Production in Barnett Shale Tight Gas Wells
Authors: Siebrits E. , Elbel J. L. , Hoover R. S. , Diyashev I. R. , Griffin L. G. , Demetrius S. L. , Wright C. A. , Davidson B. M. , Steinsberger N. P. , Hill D. G. 
Published: December 2007

Abstract
Refracturing can be used to increase production in poorly fractured wells. A different application of this technology is to refracture wells with strong initial fractures. In this paper, we provide evidence of increased production due to refracturing two tight gas wells having deeply penetrating initial fractures. Surface tiltmeter measurements show refracture orientations at oblique angles to the azimuth of the initial fractures.
Hydraulic Fracture Growth through Offset Pressure-Monitoring Wells and Boreholes
Authors: Jeffrey R. G. , Settari A. 
Published: December 2007

Abstract
The growth of hydraulic fractures through nearby wells and boreholes in which pressure was monitored has been recorded as part of eleven field experiments conducted over the past few years. These direct measurements of fracture growth are compared to one another and to predictions of growth made using numerical models.
The effect of fracturing into an open well, which then acts as a high fluid loss sink, is illustrated by some of the data and through numerical modeling.
Evolution of the Production Semisubmersible
Authors: Lim E. F. H. , Ronalds B. F. 
Published: December 2007

Abstract
Semisubmersibles and FPSOs are the two most common floating production solutions and they compete in many field developments. The first production semisubmersible in 1975 preceded the prototype FPSO by two years. Both concepts were more or less on a par for the next two decades, until the dramatic surge in popularity of the FPSO in the late 1990s. However, the continued adoption of semisubmersibles indicates that they retain advantages over FPSOs in certain situations.
Semisubmersibles have seen application in most petroleum provinces around the world outside Australasia. Traditionally semisubmersibles were converted drilling rigs used for EPS and short field life developments. Many are located in only moderate water depths. However, recent semisubmersibles have been adopted for large production facilities. They have also been used in ultra-deepwater, and several semisubmersibles have held deepwater production records. Many of these developments are off Brazil and Norway. These changes in focus have required new-build semisubmersibles with novel hull forms in comparison with traditional drilling units.
The early popularity of semisubmersibles over FPSOs is related to their advantages in harsh environments. With the development and advancement of internal turrets, FPSOs have recently seen acceptance in severe North Sea conditions. Today, a principal driver for selection between semi-submersibles and FPSOs is the relative importance of workover capability and infield storage. Other key factors include the opportunity for gas export, the number of risers required and the availability of vessels for conversion.
The paper traces the evolution of the production semisubmersible and gives a comprehensive database of applications to date. A comparison of the relative merits of semisubmersibles and FPSOs for different production scenarios is also included.
A Simple Model To Predict Natural Gas Separation Efficiency in Pumped Wells
Authors: Harun A. F. , Prado M. G. , Serrano J. C. , Doty D. R. 
Published: December 2007

Abstract
A new mechanistic model to predict the natural separation efficiency in vertical pumped wells has been developed. The model is based on the combined phase momentum equations and a general slip closure relationship. New drag coefficient correlations have been developed corresponding to the bubbly (i.e. undistorted particle) and churn-turbulent flow regimes. The model indicates that the natural separation efficiency depends strongly on geometry, void fraction and in-situ gas flow rate.
Shale Stabilisation by Pressure Propagation Prevention
Authors: Carminati S. , Del Gaudio L. , Brignoli M. 
Published: December 2007

Abstract
Different commercial shale additives for wellbore stabilisation have been tested to clarify their mechanism of action and rank their performance. Specifically they have been evaluated for their capacity to prevent pressure propagation from the drilling fluid to the formation, and their impact on shale hardness. Pressure propagation experiments have been performed under high pressure-high temperature conditions. For the silicate muds, an ability to reduce pressure propagation was verified; for others, including cloud point glycols which have been suggested to plug shale pores, no strong effect was found. Shale hardness by indentation tests has been evaluated at ambient conditions after ageing at 80°C. Hardness tests give a clear indication that both cationic polymers and silicates increase shale strength, while glycols are effective in increasing shale strength and reducing pressure propagation only when the potassium ion is also present.
A new pore plugging system based on an oil-in-water emulsion has been demonstrated to prevent pressure propagation in laboratory experiments. Its effectiveness depends on the capillary entry pressure of the oil droplets into the shale pores.
Finally a few considerations on how to apply the research results in drilling operations are given.
Significance of the Non-Darcy Behavior on the Fluid Loss into High Permeability Formations
Authors: Civan Faruk 
Published: December 2007

Abstract
The constant property (incompressible) and variable property (compressible) filter cake models considering nonDarcian linear and radial flow conditions are facilitated for estimation of the filter cake thickness and the fluid loss into high permeability formations. These models can be applied for analyses of the filtration problems associated with the drilling, hydraulic fracturing, and workover operations.
The parametric studies demonstrate that nonDarcian flow conditions are more dominant during the build-up of incompressible filter cakes over high permeability formations without involving fine particles invasion and retention. The non-Darcian effects rapidly diminish for compressible cakes undergoing fines deposition within the cake matrix.
Surrogate Modeling-Based Optimization for the Integration of Static and Dynamic Data Into a Reservoir Description
Authors: Queipo Nestor V. , Pintos Salvador , Rincön Nestor , Contreras Nemrod , Colmenares Juan 
Published: December 2007

Abstract
This paper presents a solution methodology for the problem of estimating the distributions of permeability and porosity in heterogeneous and multiphase petroleum reservoirs by matching the static and dynamic data available.
The solution methodology includes, the construction of a "fast surrogate" of an objective function whose evaluation involves the execution of a time-consuming mathematical model (i.e. reservoir numerical simulator) based on neural networks, DACE modeling, and adaptive sampling. Using adaptive sampling, promising areas are searched considering the information provided by the surrogate model and the expected value of the errors.
The proposed methodology provides a global optimization method, hence avoiding the potential problem of convergence to a local minimum in the objective function exhibited by the commonly Gauss-Newton methods. Furthermore, it exhibits an affordable computational cost, is amenable to parallel processing, and is expected to outperform other general purpose global optimization methods such as, simulated annealing, and genetic algorithms.
The methodology is evaluated using two case studies of increasing complexity (from 6 to 23 independent parameters). From the results, it is concluded that the methodology can be used effectively and efficiently for reservoir characterization purposes. In addition, the optimization approach holds promise to be useful in the optimization of objective functions involving the execution of computationally expensive reservoir numerical simulators, such as those found, not only in reservoir characterization, but also in other areas of petroleum engineering (e.g. EOR optimization).