bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fully Coupled Analysis of Well Responses in Stress-Sensitive Reservoirs
Authors: Chin L.Y. , Raghavan R. , Thomas L.K. 
Published: December 2007

Abstract
A fully-coupled geomechanics and single-phase, fluid-flow model is developed to evaluate the combined effects of stress, fluid flow and reservoir property changes on well performance. In particular, we pay particular attention to the interpretation of pressure buildup tests and to changes in the production characteristics of wells. In general, for weak hydrocarbon reservoirs that exhibit nonlinear, elastic and plastic constitutive behaviors and stress-dependent properties such as permeability and porosity, the coupling effect may not be ignored in well test analysis. The coupled interaction between geomechanics and reservoir fluid production markedly affects the stress state and reservoir properties. Because we are using a coupled, numerical model, we evaluate the consequences of using simplified relationships (e.g., permeability as a function of pressure). Numerical analyses are performed to quantitatively assess the impact of reservoir stress-sensitivity on practical well test problems. The key variables investigated in the study, that are important in evaluating stress-sensitive reservoirs, include permeability, porosity, and constitutive behaviors of reservoir rock including hysteresis and loading conditions. The development of high-stress regions around wellbores and its consequences on well performance are considered. The numerical results from the study indicate that for analyzing highly stress-sensitive reservoirs, a fully-coupled geomechanics and fluid- flow modeling approach is necessary and the developed model employed in this study provides such a tool.
P. 127
Incorporation of Two-Phase Production Data into Reservoir Characterization
Authors: Ates Harun , Kelkar Mohan 
Published: December 2007

Abstract
In this study, two-phase production history data is incorporated into reservoir characterization by inverse modeling. As a first step, an analytical method has been developed to compute sensitivity coefficients for two-phase flow conditions. These equations are independent of flow simulators, and can be incorporated to any finite difference or streamline simulators. They only require one simulation run to compute the sensitivities for all time steps. In this study, we have chosen streamline simulation, which is order of magnitude faster than finite difference simulations. In the second step, a dual loop iteration technique is employed which uses conjugate gradient relaxation in order to bypass the explicit construction of the sensitivity coefficient matrix and the inversion of the product of sensitivity coefficient matrix and its transpose. Thus, a substantial reduction in the computational cost for solving the inverse problem is achieved, including the help of streamline simulation. Finally, this technique was validated using synthetic as well as field cases. The field case study was conducted on a sandstone reservoir.
P. 151
Sedimentary Interpretation of A Multilayered Clastic Oil Reservoir: Impact on Development Plans for the Zubair Reservoir, Raudhatain Field
Authors: Nemcsok S. , Morrison N.H. , Carruthers A. , Abdullah Sh. 
Published: December 2007

The Lower Cretaceous Zubair reservoir is a major producing horizon in the Raudhatain Field of North Kuwait. The reservoir comprises a number of isolated vertical major sandstone units. With plans to significantly boost production through waterflooding, a major studies program has been conducted. A major sedimentology and reservoir description review has defined controls on reservoir quality, heterogeneity, and architecture. A new layering scheme has been established to honor the sedimentological boundaries and the associated dynamic reservoir behaviour.
Deposited primarily as estuarine channel sands, the Zubair reservoir shows a preferred west-east channel-fill geometry across a north-south paleo-shoreface. The understanding of this geometry is crucial in the selection of future drilling locations to meet both injection and production constraints. Four main flooding events during clastic deposition define the main producing units in a sequence stratigraphic framework. Four reservoir quality sandstones are present within the nine lithotypes identified. Channel incisions down into the underlying section by up to sixty feet create strong vertical connectivity in the main producing horizon in the Upper Zubair.
Integration of the static model, incorporating recently acquired 3D seismic, with the dynamic data has enabled an optimized development plan which incorporates both uncertainty and risk reduction. This plan will develop the field with peripheral water injection, supplementing the natural aquifer in some intervals. Dual wells will be used to maximize value. Historic gas injection and units at or around saturation pressure complicate the reservoir development. The occurrence of tar mats, identified by Iatroscan techniques, presents a further control on the selection of drainage and injection points.
P. 177
Integrating Seismic and Well Log Data. A Case Study from the Misoa Formation, Lake Maracaibo, Venezuela
Authors: Diyashev Iscander R. , Ayers Walter B. , Martin Ronald B. , Lopez Alejandro , Escorcia Florangel 
Published: December 2007

Abstract
This paper presents methods and results of the integration of 37km2 of 3D seismic data and 38 well logs from the VLE 196/Lamar Field, Block V of Lake Maracaibo. The goal of the study was to develop a geologic model using integration of seismic and well log data. Specifically we mapped reservoir properties using both seismic and well log data in the area that has good well control, and extrapolated porosity and thickness eastward, to encompass the area required for reservoir modeling but lacking well control, using seismic data alone.
P. 189
An Evaluation and Design Approach to Gravel-Pack Treatments in the Gullfaks field
Authors: Karlstad Simen , Sherlock-Willis Terri , Rajan Surya , Samsonsen Bianc , Monstad Per Arild 
Published: December 2007

Abstract
Wells in the Gullfaks field, situated in the Norwegian sector of the North Sea, are characterized by long, highly deviated producing intervals. Cased hole completions with 177.8 mm production liners are dominant, but since 1994 several wells have been completed as open hole in one or two intervals. The Gullfaks field is producing from a reservoir that consists of a multitude of high permeability loosely consolidated sandstone formations. Formation permeability varies from 50 md to as much as 10 darcies, while reservoir pressure ranges from 220 bar to 320 bar. Sand production from the loosely consolidated formations is prevented with traditional gravel-packs. Internal gravel-packs in the Gullfaks field are performed with under-balanced snubbing, thereby eliminating the need to kill the well at any stage of the operation. Leakoff in the different formation sands is well defined by log permeability and reservoir pressure; high choke pressure during the under-balanced operation aids in controlling the pre-determined return rate throughout the job.
This paper describes an approach where gravel-pack treatments pumped in the Gullfaks field have been designed and evaluated using a pseudo three-dimensional gravel placement simulator. With reservoir pressure given as a range rather than a specific value, a sensitivity study yielded the best estimate for reservoir pressure. Following verification of reservoir parameters and simulator capabilities, new jobs were optimally designed using the simulator so that potential pitfalls in traditional designs could be avoided. Designs were modified to achieve a successful annular pack, also permitting a priori knowledge of safe operational limits. This further allows better control over fluid selection, rate determination, tool position and other parameters that are critical to achieving a successful outcome of the treatment. Post-job evaluation of gravel-pack treatments using this approach confirms the validity of the designs.
Three wells in the Gullfaks field operated by Statoil, serve as the basis for the case studies presented in this paper. Recommendations are made on how to extend the technique to similar fields.
P. 149
Ultrasonics Technology: Creating a New Approach to Drill Cuttings Disposal
Authors: Glansbeek J.H.B. , Avern N.R. , Simpson D.T. 
Published: December 2007

Abstract
The use of ultrasonic technology to assist with the disposal of drill cuttings has been assessed as part of a larger environmental study. Ultrasonic technology allows particle sizes to be reduced, suitable to create a stable homogenous suspension which can be re-injected locally or easily conveyed and transported for disposal to another site. The significant size reduction achieved by ultrasonics also enables the dispersion of cuttings naturally into the water column when employing suitable biodegradable drilling fluids.
The results obtained from this project firstly demonstrate the size reduction capabilities (below 300 m) of ultrasound with various rock lithologies, different solids fluid loadings and the length of exposure time to the sonic waves. Secondly it showed that a stable slurry can be maintained enabling drill cuttings to be handled and transported to other disposal sites (onshore or offshore, legislation permitting) in suspension. This new approach compared to handling dry cuttings unlocks new opportunities with regards to cuttings re-injection and creates new dimensions for handling and transportation drill cuttings.
P. 199
The First Cuttings Injection Operation Worldwide in a Subsea Annulus: Equipment and Operational Experience
Authors: Saasen Arild , Bale Arthur , Corneliussen Rune , Kristiansen Per Bjarne , Oftedal Bjorn 
Published: December 2007

Abstract
The first cuttings re-injection operation in a subsea annulus is presented. A discussion of some important formation fracturing aspects is presented. The necessary equipment is described. This includes a description of the modified well head design for cuttings re-injection and description of a flexible hose transporting the re-injection slurry from the platform to the well head. A short description of the cuttings re-injection operation is given where cuttings were re-injected into the same well as being drilled.
P. 207
Handling, Treatment, and Disposal of Produced Water in the Offshore Oil Industry
Authors: Khatib Zara I. 
Published: December 2007

Abstract
Several liquid/liquid hydrocyclones and disc-stack centrifuges were evaluated to determine their performance in removing dispersed oil and to establish the domain of their operation. Results of pilot tests at the Westhollow Technology Center and the full-scale field trials in GOM are summarized. Based on these results, flow diagrams to integrate hydrocyclones and disc-stack centrifuges into a production separation facility are recommended. Best practices are also outlined to handle, treat, and dispose of produced water effectively.
Dehydration Field Tests on Draugen
Authors: Polderman H.G. , Hartog F.A. , Knaepen W.A.I. , Bouma J.S. , Li K.J. 
Published: December 2007

Abstract
Tests were carried out to investigate the potential of new Zeta Dynamics internals for the optimisation of the water handling capacity of the Draugen primary separators. To this end these new internals were installed in the Draugen test separator and an assessment was made of its separation performance before as well as after the installation.
Since the production at Draugen is still practically dry, the advent of water production was simulated by flowing heated seawater through the separator. The tests were carried out on the wellstream of one of the horizontal platform wells, and water was injected upstream of the choke valve using the high mixing intensity in the valve to disperse the water in the crude. The tests consisted of varying the crude and water flow, and measuring the distribution of water and oil upstream, inside and downstream of the separator, via sampling and radiological techniques.
It could be concluded that the modification of the separator internals has not led to an obvious breakthrough in separation performance. The new internals improve the flow distribution, as claimed by the vendor. This appears from the sharper interfaces in the tests after the modification, and from the reduced spread in the residence time distributions. However, the new inlet internal has a negative effect on the phase distribution of the incoming feed. This appears from the increasing mixing of gas, crude and water in the separator with increasing flowrate, this despite the simultaneously decreasing stability of the crude/water dispersion and the existing gas/liquid stratification at the inlet. It can be conjectured that the originally installed Shell 'Schoepentoeter' inlet gives less resistance to the flow and may even favour coalescence and preseparation due to centrifugal acceleration.
The test results show that the size of the water droplets at the inlet is correlated with the water concentration and the pressure drop over the choke valve. However, the correlation is different from the one established from laboratory experiments, which is probably due to the different degree of premixing in both cases.
The density profiles in the separator give evidence for the presence of a dispersion band, varying in size with process conditions. The predictions of separation efficiency as a function of flow rate and feed droplet size according to the SRTCA dispersion band expansion model (ref. SPE 38816) are in agreement with the test results.
Finally the future dehydration capacity of the Draugen installation was estimated by combining the validated separation efficiency correlations with calculations of the droplet size expected at the prevailing operating conditions.
P. 121
Modeling Heavily Faulted Reservoirs
Authors: Heinemann Z. E. , Heinemann G. F. , Tranta B. M. 
Published: December 2007

Abstract
The gap between a geological reservoir model and its numerical simulation model increased rapidly in the last decade. Due to 3D seismic and other highly sophisticated techniques the geological model can now account for normal and reverse slanted faults, high permeability channels, discontinuities, etc. down to a resolution of 10x10x1 feet. The reservoir can be represented by 100 million grid points and include accurate positioning of 3D faults and other surfaces. In a simulation grid the faults are conventionally represented by the Cartesian, corner point or curvilinear grid block boundaries. In this way only few faults can be handled and even then, they are inaccurately modeled. It is therefore not possible to model a heavily faulted reservoir with conventional methods.
The paper presents a new concept and a fully developed solution to this problem. The fundamental difference between this method and all previous ones is that the faults are regarded as inner boundaries and the flow equation will not be used to calculate the fluid transfer through these surfaces but instead it will be handled by boundary conditions. The concept allows the automatic alignment of the grid in a heavily faulted reservoir. The location of the grid points is not changed and only the shape of grid blocks along the fault traces is modified. The method is applicable for Cartesian as well as kPEBI (perpendicular bisection grid with full permeability tensor) grids. The mathematical basis of the gridding and the fault construction methods were already published1,2,3. This paper presents the implementation in industrially used simulator(s) and shows the advantages of the new method. The practical applicability is demonstrated by 2 case studies. The first one is the 2000 km2 Aderklaa conglomerate containing several oil and gas fields. The second is a slanted well traversing several reverse faults.
Field Simulation of Naturally Fractured Reservoirs Using Effective Permeabilities Derived From Realistic Fracture Characterization
Authors: Jensen C.L. , Lee S.H. , Milliken W.J. , Kamath J. , Narr W. , Wu H. , Davies J.P. 
Published: December 2007

Abstract
In this paper, we describe field application of our recently published boundary element and simulation methods to account for flow in naturally fractured reservoirs. We apply our methods to modeling Carter Knox and Rangely Fields, both onshore fractured reservoirs in North America. Carter Knox is a tight-gas reservoir undergoing primary depletion, and Rangely is a mature reservoir undergoing tertiary oil recovery.
Our method uses explicit and complex fracture geometries generated for the entire field area of interest. Effective permeability tensors at the grid-block scale are generated by accurately calculating coupled matrix and fracture flow. The effective permeabilities reflect the enhanced and directional flow effects created by the presence of fractures that may not be oriented orthogonally to the simulation grid. A finite-difference reservoir simulator, enhanced to account for tensor permeability input, is used to model field performance.
Because the model includes all available geologic and well features (such as natural and induced fractures), ad hoc changes to original geological input during history matching are reduced. Using this improved history-match model allows for improved prediction of reservoir performance. P. 157
Effects Of Discontinuous Shales On Multi-zone Steamflood Performance In The Kern River Field
Authors: Williams L. Lee , Fong William S. , Kumar Mridul 
Published: December 2007

Abstract
Steamflood performance of the Monte Cristo I lease in the Kern River field was analyzed in this study. A detailed, 18-pattern, heterogeneous model incorporating all reservoir zones was developed to simulate over 21 years of field response and predict future performance. Results were used to improve reservoir management, quantify the impact of discontinuous shales on oil recovery from individual zones, determine inter- zone gravity drainage, and identify bypassed oil zones for future infill drilling.
Results show that detailed modeling provides a more realistic description of actual performance and that small, pattern- element or single-sand models used in previous steamflood studies are inadequate for such reservoirs. Calculated oil recovery and temperature profiles compare well with field data. Discontinuous shales allow significant oil drainage to occur from the upper to the lower sands. As a result, the upper. unsteamed zones contain less reserves than expected. On the other hand, the lower zones continue to produce long after steam injection into the zone has stopped, giving high apparent recovery. The multi-pattern, heterogeneous model may be also used to identify bypassed zones for future in-fill drilling.
P. 267
Geostatistical Analysis of Petrophysical Data and Modeling of Fluid-Flow Effects in
Authors: Jennings James W. , Ruppel Stephen C. , Ward W. Bruce 
Published: December 2007

Abstract
Permeability data from Permian dolomitized shallow-water platform carbonate outcrops in West Texas and New Mexico document extreme, short-range variability, vertical inter-bed average permeability contrasts, 140–180 ft [42–54 m] lateral periodicities, and up to 2,700-ft [810-m] lateral trends. The short-range heterogeneities can be modeled with K-Bessel semivariograms having asymptotic power-law behavior at the origin. The periodicities can be modeled with "hole-effect" J-Bessel semivariograms. Most of the variance within single grainstone units is concentrated in the first few feet [1 or 2 m]. Variabilities within grainstone beds are larger than contrasts in average permeability between beds.
Stochastic 2-D areal and vertical cross-section models explore the effects of these heterogeneities. Simple tracer simulations demonstrate that some long-range features control overall flow behavior even when short-range variability composes most of the variance. The short-range heterogeneities produce local smearing of tracer fronts.
P. 305
E & P; Old and New Forecasting Issues
Authors: Soendenaa E. , Haldorsen H.H. 
Published: December 2007

Abstract
A production forecast is real enough, but making it is still 'real magic'. Why? Because when making it, we still have to quantify rocks we have not measured properly and assume, or even ignore a large number of future events (oil price, technology development, etc) which may later affect it ('magic'). Hence, concepts like uncertainty, risk, grisk (= the possibility of exceeding expectations) and probability are introduced to be able to communicate about uncertain forecasts with a quantitative language.
25 years of North Sea forecasting has given oil companies and exploration and production (E&P) -professionals invaluable experience. A large number of surprises, both positive and negative have educated everyone involved. This paper will address some of the lessons learnt and the dramatic improvements in E&P-tools and work processes over the years.
Communication and co-operation among disciplines, projects, companies etc. are discussed from the viewpoint of 1) passing on error bars, 2) learning, 3) the value of diversity and 4) optimal decision-making to achieve success (success = 'running well' (high production regularity) on 'well-chosen roads' (development concept)).
Lastly, future forecasting challenges and 'new' forecasting issues are discussed; anticipating new technology, smaller, deeper and more complex fields, deep-water fields, new types of wells, etc.
In general, without production forecasts, the E&P-industry comes to a grinding halt. Without reliable forecasts, no optimal decisions can be made. Some of the best minds in the nation devote their talent to E&P forecasting under uncertainty. Top management is totally dependent on their creativity, competence and good judgement. For this reason, the 'technical ladder' should be a real and attractive career alternative. Predicting the unpredictable is a job, which demands considerable respect. Some say its pure luck if we are spot on with our forecasts. The funny thing is that the more we practice and the more experience we gain the 'luckier' we seem to get!
P. 157
Simulation with a Full Tensor Coefficient velocity Field Recovered From a Diagonal Tensor Solution
Authors: Edwards Michael G. 
Published: December 2007

Abstract
Commercial simulators generally assume that the pressure equation always has a diagonal tensor permeability field. However, cases that involve the use of non-Cartesian grids, cross-bedding or upscaling (or any combination there-of) will give rise to a full tensor coefficient velocity field. Discretization of a full tensor increases the scheme stencil, simulation cost, and complexity of implementation. The focus of this paper is on the development of fully implicit finite volume schemes that can allow full tensor fluxes while retaining standard matrix inversion.
P. 383
Laboratory Design and Field Implementation of Microbial Profile Modification Process
Authors: Lee Hae Ok , Bae Jae H. , Hejl Keith , Edwards Aimee 
Published: December 2007

Abstract
A microbial profile modification process consisting of sequential injection of spores and nutrient was designed and field tested in Eunice Monument South Unit, a carbonate reservoir, in Lea County, New Mexico. Laboratory work involved testing of microbial activity in reservoir brine, nutrient optimization, and design of spore and nutrient concentration and size. An 80-acre, inverted five-spot pattern was used in this field trial. The pre-treatment injection profile in the central injector showed the presence of two thief zones, which were taking 42% and 58% of injected water. 16,000 barrels of spore suspension in the concentration of 108 cfu/mL (colony forming unit per mL) was injected for 16 days, followed by the injection of 14,000 barrels of nutrient solution. Prior to microbial treatment, the water injection rate was 1000 bbls/day at 30 psi at the header, whereas the post treatment injection rate was 500 bbls/day at 650 psi. Several post-treatment injection profiles up to 8 months after the treatment, showed almost complete fluid diversion and good stability of the in-situ formed biofilm. P. 393