bluuebunny/crossref_metadata_2025 huggingface dataset:
Imaging Injected Water flood Fronts between Wells in a Complex Carbonate Reservoir: Designing Completions to Optimize Image Resolution
Authors: Bhatti Zahid , Shuaib Mohamed , Wilt Michael , Levesque Cyrille
Published: December 2007

In the paper, we will briefly review the pilot design and demonstrate the utility of applying the EM imaging to the pilot. We will also show the benefit of the optimized casing material on the resolution of the crosswell EM resistivity images and describe the methods employed for monitoring the fluid flow and show preliminary results of the modeling process. This crosswell EM technique which has been successfully employed and proven in other geographical areas is being implemented first time in UAE.

The EMI technology is being deployed in southern part of a complex carbonate reservoir in the middle-east where an uneven flood front advance has been observed in different reservoir units. It has been observed that water front has advanced much faster in the highly permeable upper reservoir units as compared to lower reservoir units. In order to understand the horizontal and vertical fluid flow behavior, an inverted 5-spot water injection pilot pattern is being implemented. The pilot will address the issues of the uneven sweep efficiency, bypassed oil and effectiveness of stylolites across different units. The pilot results and observed data will be used in the simulation to design an optimum development scheme for the lower reservoir units in the southern part of the field.

The current dynamic simulations predicted that the injected water will reach producers after 7 to 10 years. However, the decision on field developments have to be taken early enough to avoid the slumping of water from upper to lower units and loss of reserves in the lower units. Early imaging of the injected water from the injection well into the reservoir is paramount in assessing the success of the pilot and future field development issues.

It is anticipated that this tomographic Cross-well Electro-magnetic (EM) resistivity technique will provide sufficient imaging information to track the water flood movement between wells. The most favorable conditions to acquire reliable formation resistivity distribution information, EMI require at least one kilometer distance or separation between wells.

Prior to the field deployment, simulations were run to confirm the applicability of the technique and define the parameters for the survey with objectives; 1) to check the sensitivity of EM technique to the reservoir conditions and injected fluids, and 2) to carry out actual EM tool simulation and check the quality of tool response. The study concluded; 1) cross-well EM resistivity technique is well suited for tracking the water front in the current reservoir conditions, 2) the injected fluids create enough resistivity contrast to be easily picked up by the technique, and 3) the flood front progress can be captured by conducting the surveys in a time-lapse mode.

As part of this project, lab tests were conducted to choose a material that would limit the attenuation at high frequency as much as possible at source and receiver locations.
Fieldwide Reservoir Characterization Based on a New Technique of Production Data Analysis: Verification Under Controlled Environment
Authors: Mata D. , Gaskari R. , Mohaghegh S.
Published: December 2007

Intelligent Production Data Analysis – IPDA, is a new methodology for Reservoir Characterization based only on monthly production rate data. This technique combines conventional methods of production data analysis (decline curve analysis, type curve matching and history matching) with intelligent systems. The study targets the validation of this methodology under a controlled environment, attempting three main objectives: Identifying Sweet Spots, Forecasting Reserves and recognizing under-performer wells.

The study investigates the behavior of five different reservoirs, modeled using a commercial simulator. The structure, parameters and heterogeneity of each configuration was inspired by existing formations. Records of production rate data were generated from the simulated fields (both single and multi-layer formations) and used as input to perform an "Intelligent Production Data Analysis".

The findings highlight strength of this technique in tracking the fluid movement in the reservoir as a function of time. Furthermore, this study identifies some limitations and circumstances under which the analysis may not result in correct recommendations.
Advances in Measuring Porosity and Permeability from Drill Cuttings
Authors: Lenormand R. , Fonta O.
Published: December 2007

Drill cuttings can provide quick and useful information for reservoir characterization, especially when cores are not available. So far, several petrophysical properties can be determined from cuttings: porosity, permeability and T2 NMR distributions (directly related to the pore size distribution) Several laboratories are working to improve the techniques of measurements and also the drilling tools to minimize the damage to the rock. In this paper, we present new results for porosity and permeability measurements down to cuttings of diameters around 0.5 mm and the application to a field test.

The methods for measuring the porosity on cuttings are the same as for cores when the sizes are larger than 3mm. For smaller cuttings (most of cases), the best results are obtained using a centrifuge or a porous plate to remove the interstitial liquid with a controlled capillary pressure. With this method, porosities were measured within 1-2 PU (Porosity Units), even for the flat cuttings with diameter around 1mm and thickness around 0.5 mm collected during the field case.

For permeability, we used the technique developed by IFP based on the diffusion of a pressure wave in a viscous liquid saturating the cuttings. The results were improved by a better choice of the viscosity of the liquid used to saturate the cuttings. The suitable viscosity must satisfy two opposite constrains: high viscosity for a relaxation time large enough to be measured (larger than 0.2 second), and low viscosity to allow spontaneous imbibition in a short time. The results of the study are presented in a diagram, showing the viscosity to be used as a function of cuttings sizes and permeability. Porosity and permeability methods have been tested on synthetic cuttings obtained by crushing cores of known parameters.

Finally, the methods were tested on real cuttings sampled especially for this study every 20 cm in a carbonate formation (125 samples). The results are discussed and compared to porosity logs obtained in the same well. The porosities measured on cuttings agree with the log value for values larger than 5 PU. The T2 NMR relaxation times (peaks) are also in good correlation with the amount of clay given by the gamma ray log. However, the porosities and the sizes of cuttings are two small for permeability determination. Both porosities and T2 relaxation times give a good depth matching prediction with log less than 1 meter.
Experimental and Modeling Requirements for Compositional Simulation of Miscible CO2-EOR Processes
Authors: Shtepani E.
Published: December 2007

In order to design a successful miscible CO2 gas injection-EOR project, it is important to understand the physics and mechanisms by which the CO2 displaces oil in porous medium.

CO2 gas, under proper conditions of pressure and temperature, and in the presence of favorable reservoir oil composition, can become miscible with reservoir oil, helping remobilize and produce the oil remaining in the reservoir. The development of miscibility between the injected CO2 gas and the reservoir oil is through in-situ composition changes that occur from multiple fluid contacts and mass transfer between the reservoir oil and CO2 gas.

Trapping and mobilization of fluids in a porous medium are known to depend on (i) Pore Structure, (ii) Fluid/Fluid Interaction (reflected in interfacial tension (IFT) and mobility), and (iii) Fluid/Rock Interaction (related to wettability). Trapping and mobilization mechanism is related to the above factors in a complex way which can be described by complex interactions between viscous, gravity and capillary forces. EOR processes from fields typically involves altering the relative importance of these forces.

This paper discusses several aspects of miscible CO2 flooding and describes how these relate to the experimental and modeling studies required for a successful compositional simulation of miscible CO2-EOR processes.

The phase behavior experiments and EOS modeling of CO2-reservoir fluid system, as critical factors for an accurate performance prediction for miscible CO2-EOR projects, are reviewed.

In addition to PVT experiments, special coreflood experiments and numerical coreflood simulations to determine the micro-scale conformance of the CO2 displacement, identify CO2 breakthrough characteristics and longitudinal dispersion coefficient, are discussed in detail.

Finally, the importance of water injection and other factors related with CO2 injection, which could extend the miscible CO2-EOR technology to a broader range of oil reservoirs, has been given considerable attention.
Waterflood Conformance Study for a Carbonate Reservoir
Authors: Al-Anzi Khalaf , Kumar Rajendra , AL-Rashidi Tahani , Cumming John , Mckean Howard , McKie Calum
Published: December 2007

Mature fields of the Middle East have some of the longest production histories and richest data sets of any oilfields in the world. Waterfloods in fields that have operated for many years are reaching a stage in which better understanding of the reservoir’s response to water injection is critical for optimal field management going forward. A common approach, however, is that existing data sets are often used only by individual technical disciplines for relatively narrow purposes, such as well performance diagnoses.

An integrated, multidisciplinary study of a carbonate reservoir in the Minagish Field was implemented to better evaluate the conformance and integrity of current water injection operations, and make recommendations for improvement. A secondary objective was to establish a solid interdisciplinary workflow to support periodic reevaluation and update of the study.

A joint team of reservoir engineers and geoscientists was formed from KOC’s West Kuwait Asset Team and Halliburton’s Landmark group. Using a Common Visualization Environment (CVE) (Figure 1), the team integrated the Minagish Field history with all available static and dynamic data into a single, consistent data set.

A detailed geologic model with compartmentalization and layering schemes was established which was most likely to control fluid movements within the reservoir. This was validated and a more consistent model was developed by incorporating dynamic field data. The revised model based on flow units was further validated by cross-sectional reservoir simulation models in selected areas of the field.

This study suggests KOC can produce the Minagish Field at significantly higher offtakes in the future without negatively impacting recovery.
Sequence Stratigraphy-Based Geological Modeling of the Upper Thamama (Lower Cretaceous) Reservoirs of a Giant Abu Dhabi Oil Field, United Arab Emirates
Authors: Strohmenger C. J. , Al-Dayyani T. , Clark A. B. S. , Ghani A. , Hafez H. H.
Published: December 2007

Important hydrocarbon accumulations occur in platform carbonates of the Lower Cretaceous Kharaib (Barremian and Early Aptian) and Shuaiba (Aptian) formations (Upper Thamama Group) of Abu Dhabi. A new, sequence stratigraphy-keyed static (geological) model has been built for the Upper Thamama (Lower Cretaceous) Kharaib and Shuaiba formations. The Kharaib Formation contains two reservoir units (Lower Kharaib Reservoir Unit and Upper Kharaib Reservoir Unit). The overlying Shuaiba Formation is separated from the Kharaib Formation by the Upper Dense Zone (Hawar) and contains two reservoir units (Lower Shuaiba Reservoir Unit and Upper Shuaiba Reservoir Unit) only partly separated by dense intervals.

Core and well-log data of a giant onshore oil field in Abu Dhabi, as well as outcrop data from Wadi Rahabah (Ras Al-Khaimah) were used to establish a sequence stratigraphic framework and a lithofacies scheme; applicable to all four reservoir units and the three dense zones.

Six third-order composite sequences are composed of twenty-six fourth-order parasequence sets that form the basic building blocks of a new generation static model.

On the basis of faunal content, texture, sedimentary structures, and lithologic composition, fourteen reservoir lithofacies and ten non-reservoir (dense) lithofacies are identified from core. Reservoir units range from lower ramp to shoal crest to near back shoal open platform environments.

A new static (geological) model has been built to provide a more detailed reservoir description to the dynamic model to further optimize the field development plan.
Nested Stochastic Simulations: A New Approach in Assessing Spatial Distribution of Carbonate Sedimentary Facies and Associated Diagenetic Overprints
Authors: Labourdette R. , Meyer A. , Sudrie M. , Walgenwitz F. , Javaux C.
Published: December 2007

A major challenge today is the development of carbonate reservoirs. They represent the most significant reservoir formation in the middle-east gulf region.

In carbonate reservoirs, heterogeneity is usually driven by both depositional and diagenetic patterns. The complex diagenetic history which prevails in these reservoirs influences the final static and dynamic reservoir properties. Dolomitisation is one of the most crucial diagenetic phases because of the way in which it constrains the permeability behaviour of the field. Detailed diagenetic research has shown that various genetic dolomite types exist, including evaporative, mixed evolved sea-water - freshwater and late thermobaric. Defining static rock-type can therefore be problematic due to the highly imbricate diagenetic phases and their various distributions and extensions. A further major difficulty is the spatial distribution of rock-types in reservoir models, each linked to different sedimentological and diagenetic processes and each with their own, but interdependent, geometrical characteristics.

In order to optimise the current production of reservoirs as well as future field development plans it is therefore necessary to understand the main diagenetic phases and develop approaches which effectively incorporate them into the static reservoir model.

This paper presents a synthetic modelling workflow applied to a large oolitic ramp derived from outcrop and field observations. This new approach is based on nested stochastic simulations, geologically-driven and derived from the relationships between dolomite type, stratigraphic position, palaeogeographic position, depositional facies, and proximity to fault/fracture zones. In addition to the initial depositional model, three diagenetic phases are modelled successively in order to restore the complex spatial relationship existing between diagenetic alterations.

The outcome of this modelling workflow, after a stage testing coherence with PC and Kr values and dynamic rock-typing definition, is fed into a dynamic simulator in order to assess the potential impact on field behaviour, production profiles and well productivity.
A Simulation Study of Performance Miscible Diplacement in El Gassi Field, Algeria
Authors: Tiab D. , Zhu T. , Merdaci C. , Bhangale A. Y.
Published: December 2007

El Gassi is a volatile oil field located in the Algerian desert. The field has produced about 62 MMSTB oil since 1959, through primary depletion. Due to the heterogenity of producing formation, the total recovery during 45 years is only about 11%. The implementation of water-flood project was avoided due to low achievable water injection rate. A miscible gas injection project is examined in this study. The purpose of gas injection is to maintain reservoir pressure and improve the microscopic efficiency to increase the overall recovery in the field. A laboratory study revealed that the miscibility could be achieved with a pressure of about 241.4 bars (i.e. 3500 psia), which is below the reservoir average pressure in El Gassi field. Typical reservoir heterogeneities encountered in El Gassi field were incorporated into the simulation model. The study includes history matching of past reservoir performance, investigation of different injection scenarios, optimization of injection well number, optimization of gas injection and oil production rates, and the benefit of drilling infill wells. Edge line gas injection appeared to be promising.
Two Phase Flow Properties of Brine-CO2 Systems in Carbonate Core: Influence of Wettability on Pc and kr
Authors: Chalbaud C. , Lombard J. -M. , Martin F. , Robin M. , Bertin H. , Egermann P.
Published: December 2007

The design of a CO2 injection project mainly depends on the results of reservoir models. Nevertheless, it is recognized that these models generally lack physico-chemical data. This issue becomes more important for storage options, such as deep saline aquifers, for which economically driven data collection and archiving have not been performed. Among these physico-chemical data, fluid/fluid and rock/fluid interactions have been long recognized to govern fluid distribution and behavior in the porous media. This paper focuses on rock/fluid interactions with the host formation, by means of the wettability, which is one of the controlling parameters of the remaining fluid saturations, capillary pressure and relative permeability; hence conditioning the performance of any CO2 operation.

The first part of this paper presents CO2 and N2 injection experiments in a carbonate core sample. Two different wettability conditions were investigated: water-wet and intermediate-wet. Thermodynamic conditions (pressure, temperature and water salinity) are representative of storage conditions and were the same for the entire core flooding experiments. Multirate experiments were conducted with in-situ saturation monitoring and enhanced interpretation workflow (heterogeneous approach) of the production curves in order to obtain relevant and complete sets of kr and Pc data. The second part is devoted to visualization experiments. CO2 injections were performed in glass micromodels, under the same conditions, in order to track the fluids distribution as a function of the thermodynamic and the wettability conditions.

Using this approach, we showed, on the one hand, that at the core (carbonate) and pore (micromodels) scale the CO2 does not wet the solid surface when the porous media is water-wet. On the other hand, if the porous media presents an intermediate wettability, the CO2 partially wets the substrate having significant effect on water mobility (krw). In all cases the results at the core scale were consistent with those at the pore scale.

Finally, we discuss the consequences of such CO2 wetting behavior in terms of fluids distribution in the porous media, injectivity level and seal efficiency of the caprock since all these mechanisms have a direct impact on CO2 storage capacity and sustainability of any prospect site.
A Model for Completion Selection for Multilateral and Multibranched Wells
Authors: Idiodemise E. J. , Dosunmu A.
Published: December 2007

With increasing demand for optimal production and reserve recovery, more fields are currently being developed using multilateral well technology. However, the success of a multilateral well depends strongly on the completion program, use of appropriate well architecture, optimal equipment selection and Junction selection. Well completion selection decisions rely on the use of various well decision criteria including reservoir consideration, equipment selection and technology, risk, as well as economic criteria. These criteria have been explained by [1] using flowcharts, a screen matrix and a risk model. In this study a new model was developed to aid completion selection for multilateral well applications. The method applied a modified Suglyama matrix for well selection, a junction screen matrix for junction selection, a sand completion selection model for sand control and other matrices developed in the course this study. The model considers different aspects of the well completion selection process. A user-friendly visual basic software was then developed to simplify the use of the models.

Using the software developed, two case studies were analyzed. The cases are reservoir with high mobility ratio [Case A] and another with low mobility ratio [Case B] Sensitivity analysis was then performed for the different reservoir parameters to determine their variation with well production. The advantage of this software is that it is cheap, proactive and aid in completion selection.
Prediction of the Viscosity of a Water-Base Mud Treated with Cassava Starch and Potash at Varying Temperatures Using Factorial Design
Authors: Okumo I. , Isehunwa S. O.
Published: December 2007

In order to monitor and control the properties of drilling fluids, measurements are routinely made at the surface. However, these surface measurements may not be representative of down-hole properties where the desired functions of hole cleaning and other related issues are critical to the success of the drilling operations. Consequently, it is important to make necessary adjustments of the fluid properties obtained at ambient conditions to give estimate of properties at high temperatures and pressures.

The principle and method of factorial design have been used to develop a model, which makes possible the prediction of drilling fluid viscosity at varying temperatures. Cassava starch and potassium carbonate were used as local additives in a water based bentonic drilling fluid after running a quality check. 23 full factorial design experiments which consider temperature, starch and potash as factor variables and viscosity as the response variable were conducted.

The main effects as well as the interaction effects were determined and examined. The results were analyzed and a predictive model was obtained. Viscosity values obtained using the model were compared with the experimental results and it was observed that the model has an accuracy of 93.6%.

This method makes possible the prediction of the viscosity of drilling fluids at varying temperatures, hence the treatment of mud systems can be determined ahead of time.
Convergence in Gas Pricing: What It Might Mean for Nigeria
Authors: Hunziker R. N.
Published: December 2007

The world's demand for gas is expected to increase at a faster rate than any other energy source; and, many traditional supply sources are approaching maturity. Many industry pundits call for an increasingly converging global market in natural gas. What are the possible implications and opportunities for Nigeria, which is well-endowed with natural gas resources and possesses a large latent energy demand of its own?

The paper illustrates some of the signposts of the trends behind growth in natural gas market convergence. Nigeria is well-known for its gas resources; so, the paper will move-on from a review of the commercial frameworks to some of the implications and opportunities for Nigeria. Finally, the paper concludes with references to the Theme for NAICE 2007: "Optimization of Oil & Gas Potentials."
Calibration of the Elemental Capture Spectroscopy Tool Using the Niger Delta Formation
Authors: James Egbe Samuel , Omole O. , Diedjomahor Jacob , Crowe John
Published: December 2007

The Elemental Capture Spectroscopy tool (ECS) is calibrated for improved formation evaluation in "Hot sands ’ of the Niger Delta. This is done by combining the tools signal (Capture gamma ray spectrum) obtained from well # XD1 in the Niger Delta and concentrations of elements derived from the analysis of a core sample obtained from well # XD1, to produce calibration equations for the various elements measured by the tool.

The Window's method of spectral analysis was used in this study rather than the well known Yield's method. This is because the Window's method has great precision over the Yield's method at the tool's logging speed (1800ft/hr), and spectral energy resolution at operating temperatures in the borehole.

The calibration equations were validated by using spectral data obtained from a given depth in well #XD1 to predict the known elemental concentrations at that given depth. Predicted average elemental concentrations correlated very well with known average elemental concentrations.
Maximizing the Potential of Decline Curve Analysis
Authors: Aitokhuehi I.
Published: December 2007

The data most collected within the oil industry is the rate-time data. This data is analyzed with decline curve to primarily determine well/reservoir remaining reserves. However, rate-time data, which is a form of extended well testing, can also be used to estimate other reservoir parameters such as permeability and/or relative permeability curve.

In this paper, we utilized Masoner's decline derivation to show that estimates of the relative permeability curve can be obtained from a well under voidage rate control in a solution gas drive system. For a well under pressure control in a solution gas drive reservoir, however, we show that the decline is exponential and obtain an expression for the permeability. The results were applied to data from solution gas drive simulation models and are presented. Application to field data is also presented.
Analytical Method for Diagnosing and Predicting Pressure Response with Injection in Waterflood Reservoirs using Net Voidage Curve.
Authors: Okoro I. C. , Okojie S. E. , Umurhohwo J. O.
Published: December 2007

A critical component of waterflood management is the ability to proactively determine the impact of injection rates on the reservoir pressure and the capacity to diagnose injection anomalies. The most reliable means of doing this is through the use of numerical models. However, these models may be expensive to build and difficult to maintain. Therefore, a simpler and less expensive method to forecast the impact of injection rates on reservoir pressures, under various injection and production scenarios, is of immense benefit.

The method presented in this paper was developed and used by a team of Engineers managing the Meren field waterflood project to diagnose pressure response anomalies and provide estimates of injection targets to achieve any expected pressure response for the project reservoirs without the use of numerical models. It uses the slopes of the cumulative net voidage curve and the measured change in pressure response to define reservoir specific relationships between injection and pressure response. Case study on application of method for diagnosing pressure response anomalies was presented. Also, example pressure prediction calculations were performed on a project reservoir. These examples clearly establish the method as a valid tool for the early identification of injection anomalies and prediction of reservoir pressure changes. Comparison of actual pressure survey data and those predicted with the analytical model indicated that both were on the same trend.
Quantitative Mineralogy of Reservoir Rocks Using Fourier Transform Infrared Spectroscopy
Authors: Ballard Bryce D.
Published: December 2007

An inversion scheme was modified to quantitatively determine the mineralogy of reservoir rock samples using transmission Fourier transform infrared spectroscopy (FTIR). This inversion scheme adds apatite and aragonite to the previous inversion and is now capable of recognizing 16 minerals. The other minerals include quartz, calcite, dolomite, illite, smectite, kaolinite, chlorite, pyrite, orthoclase, oligoclase, mixed clays, albite, anhydrite, and siderite. The inversion predicts the mineral concentrations with an average error of +/- 1.1 wt % and within a standard deviation of +/- 2.1 wt %. It also found that 97 % of mineral concentrations are accurately predicted within +/- 5 wt %. These prediction errors are similar to published values for error associated with X-ray diffraction (XRD) which has become the industry standard for mineralogy analysis. The addition of apatite allows rapid and accurate quantification of mineralogy in gas shale reservoirs which have become a major play in U.S. natural gas exploration.
Heavy Fraction C7+ Characterization for PR-EOS
Authors: Sancet Gastón Fondevila
Published: December 2007

A compositional simulator uses an Equation of State (EOS) to predict the pressure-volume-temperature (PVT) behavior of gas and crude oil fluids, which are very complex hydrocarbon mixtures.

In a hydrocarbon mixture, the critical properties (critical pressure "Pc", critical temperature "Tc" and accentric factor "ω") must be given for each component. These properties are well known for pure compounds (like methane, ethane, etc.), but nearly all naturally occurring gas and crude oil fluids contain some heavy fractions that are not well defined. These heavy fractions are lumped and called the "plus-fraction" (C7+). There arises the need of adequately characterizing these undefined plus fractions in terms of their critical properties.

This work presents a correlation for the critical properties of the plus-fraction C7+ needed in the characterization of crude oil fluid samples for a compositional simulator using Peng-Robinson's1 EOS. The correlation is a function of the fraction's molecular weight (MW).

Twenty (20) PVT laboratory tests made in black oil fluid samples taken from fields of the Neuquén Basin (Argentina) were utilized for the adjustment of the bubble point (Pb), gas-oil ratio (GOR), constant composition expansion pressure-volume relation (PV) and differential expansion curves (Rs, Bo and ρo) of the compositional simulator.

A comparative study was performed against the Riazi-Daubert's2 correlation. The correlation here presented gives better results than those of Riazi-Daubert's correlation and also gives excellent liquid density predictions when there are high MW hydrocarbons present in the fluid.
Streamline-Based Reservoir Model Calibration to Three-Phase Production Data
Authors: Oyerinde Adedayo
Published: December 2007

Streamline-based assisted and automatic history matching techniques have shown great potential in reconciling high resolution geologic models to production data. However, a major drawback of these approaches has been incompressibility or slight compressibility assumptions that have limited applications to two-phase water-oil displacements only. Recent generalization of streamline models to compressible flow has greatly expanded the scope and applicability of streamline-based history matching, in particular for three phase flow. In our previous work, we calibrated geologic models to production data using the generalized travel time inversion (GTTI) technique. For field applications, however, the highly non-monotonic profile of the gas/oil ratio data often presents a challenge to this technique. In this work we present a transformation of the field production data that makes it more amenable to GTTI. Further, we generalize the approach to incorporate bottom-hole flowing pressure during three-phase history matching. We examine the practical feasibility of the method using a field application. The field case is a highly faulted, west-African reservoir with an underlying aquifer. The reservoir is produced under depletion with three producers, and over thirty years of production history. The simulation model has several PVT and SCAL regions and over a hundred thousand cells. The GTTI is shown to be robust because of its quasi-linear properties as demonstrated by the water-cut and GOR match for a period of 30 years of production history.
Water Saturation Evaluation in Shaly Sand Reservoirs Using Advanced X-ray Diffraction and Cation Exchange Capacity Measurements
Authors: Ugbo Justin
Published: December 2007

Interpretation problems are commonly associated with calculating water saturation in non-homogenous shaly sand reservoirs. Recent studies on the electrical anisotropy of shaly sands have shown that the level of our understanding our ability to correctly and accurately evaluate complex shaly sand reservoirs can be greatly improved.

The model ("Total Expansible Clay Model") developed in this work is similar in form to the recent shaly sand Dual Water Model, except that the clay effect have been defined by a volume-conductivity transform rather than the usual volume-porosity transform.

The model is experiment-based and designed to quantify the effects of the mineralogical and electrical properties of clay minerals on well log signatures.

The Total Expansible Clay Model evaluates these effects via direct measurement of independent mineralogy and cation exchange capacity of the clay minerals within the reservoir sands.

The model integrates the following as an effective basis for characterizing shaly sand reservoirs:

Rietveld based siroquant assay for quantitative X-ray diffraction (XRD) used in determining mineral percentages from standard XRD trace patterns, Cation exchange capacity (CEC) used to determine the quantity of cations involved in the exchange at the shale-water interface, Porosity, permeability, density and resistivity measurements,

Overall, the correlations drawn from this model yield improved results for total water saturation (especially in low porosity and highly shaly formations), which appear consistent with those calculated earlier using well known water saturation models (Dual Water and Juhasz). A total of 23 core plugs from two wells in the Cliff Head Field, Perth Basin, were analyzed for this study.
Deepwater Driven Advancements in Well Control Equipment and Systems
Authors: Vigeant Shawn P.
Published: December 2007

The recent surge of deepwater drilling activity throughout the world, and in particular the US Gulf of Mexico has prompted oil companies, drilling contractors and equipment manufacturers alike, to develop and implement a wide variety of technologically advanced systems designed to overcome the adversities associated with the harsh environment of today's extreme water depths. In particular well control equipment and related systems have undergone the greatest transformations and made the most significant technological gains.
A Closed Circulating System for Air Drilling
Authors: Rusnak Jerry A.
Published: December 2007

Current practice while air or air/mist drilling in the Arkoma Basin is to exhaust all fluids and cuttings into an earthen waste pit. A system has been developed to eliminate the waste pit without otherwise changing the basic drilling process and conditions.
Development and Application of an Underbalanced Drilling Simulator
Authors: Bijleveld A.F. , Koper M. , Saponja J.
Published: December 2007

A part of the planning of underbalanced operations is to estimate drilling and production related parameters. Wellbore pressure and fluid phase velocity profiles, hydrocarbon production management mechanisms and injection gas requirements are necessary for designing underbalanced drilled wells. A steady state underbalanced drilling software tool has been developed by Shell to assist their well engineers in planning and executing underbalanced operations. The simulator has been validated and its accuracy proven with field data comparisons. The accuracy was within the range of the intended area of application and has indicated less than 10% difference in measured wellbore pressures. The objective of the software development is to release the simulator to the industry. Concurrently the model will be developed further and its accuracy improved. A concern at the moment, is the limited number of wells drilled underbalanced with sufficient data gathered to allow extensive simulator comparison.

To obtain an overview of capabilities and applicability of presently on the market available simulators, a thorough comparison between models is recommended.

P. 113
The First Coiled Tubing Sidetrack in Norway, Gullfaks Field
Authors: Gaaso R. , Gjerde K. , Samsonsen B.
Published: December 2007

Statoil has recently completed a sidetrack drilled with coiled tubing. The sidetrack, the first on the Norwegian Continental Shelf of its type, is 254 m and was drilled from the Gullfaks A platform.

The objectives of the project were to drain a small reservoir pocket and to qualify the coiled tubing drilling technique. Staking out a course for further development of the CTD technology was also part of the job.

This paper will describe how Statoil successfully achieved these objectives with a small project team, intensive experience gathering, dedicated contracting strategy, short project planning phase, continuos dialogue with the authorities and a drilling program based on simple and field proven solutions.

The sequence of operations started with removing the completion string tail-pipe with ID-restrictions. This was followed by isolating the existing perforations in the motherwell and installing a through tubing retrievable whipstock. A window was milled in the 7" liner and a 3 3/4" hole drilled to TD with a build-up rate of 25 degrees per 30 m and a tangent section at 93 degrees. The reservoir was logged using coiled tubing. A 2 7/8" liner was run to TD and cemented. The reservoir was perforated in underbalance.

The well has produced at a rate of 400 5m3/day >50 % water- cut) from one of many oil bearing reservoir pockets in the Gullfaks field.

P. 123
The Effect of PDC Cutter Density, Back Rake, Size, and Speed on Performance
Authors: Sinor L.A. , Powers J.R. , Warren T.M.
Published: December 2007

This paper evaluates the effect of cutter density, back rake angle, size, and speed on the steady state wear rate and performance of Polycrystalline Diamond Compact (PDC) cutters. The analysis is based on laboratory and controlled field testing results at Amoco's Catoosa Test Facility.

P. 131
Drill Bit Seismic: A Drilling Optimization Tool
Authors: Meehan R.J. , Nutt L. , Dutta N. , Menzies J.
Published: December 2007

In recent years a new drilling optimization technique has emerged. Drill bit seismic uses the acoustic energy radiated by a working drill bit to provide time-to-depth and look-ahead information while drilling. This information, available in real time at the wellsite, significantly reduces uncertainty. It enables the depth to casing and coring points to be more precisely defined, leading to elimination of some casing strings and ensuring vital horizons are cored. Integrating the data with other measurements can help in monitoring pore pressure trends, with obvious implications for safety. The technique requires only surface sensors, and does not interfere with the drilling process, hence no rig time is lost.

This paper aims to give a complete picture of the drill bit seismic technique. The deployment of the sensors and methodology for data acquisition are described in some detail. An overview of the signal processing techniques is given, illustrated with real data from both onshore and offshore rigs. The benefits drill bit seismic can bring are demonstrated by means of several field examples, showing how the data can be used to reduce drilling costs and improve efficiency. The current limitations of the technique are also discussed, and possible directions for future development proposed.

P. 177
New Gas Hydrate Inhibitors for Deepwater Drilling Fluids
Authors: Halliday William , Clapper Dennis K. , Smalling Mark
Published: December 2007

Low density gas hydrate suppressive drilling fluids have been developed for deepwater applications. These fluids utilize low molecular weight organic compounds for gas hydrate inhibition. Fluid densities as low as 9. 11b/gal can be designed for fluids with gas hydrate suppression greater than 30 F relative to water. These fluids are especially suited for use when low fracture gradients are encountered while drilling intervals where gas hydrate formation in the drilling fluid is possible. In addition, these additives provide greater gas hydrate suppression to drilling fluids than that provided by conventional thermodynamic gas hydrate inhibitors.

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Shock Sub Performance Tests
Authors: Warren T.W. , Oster J.H. , Sinor L.A. , Chen D.C.K.
Published: December 2007

Shock subs are often used when drilling hard rock to reduce the affect of axial vibrations created by roller cone bits, but their affect on lateral vibrations is not well known, thus a series of downhole experiments were conducted at Amoco's Catoosa Testing Facility to evaluate commonly used shock sub designs. Hard rock was drilled with a roller cone bit and each shock sub was tested at two different locations in the BHA under a wide variety of WOB's and rotary speeds. The performance of the shock subs were measured with two downhole vibration sensors (3 axis accelerations), one below and the other above the shock sub to determine the affect of the shock sub on both axial and lateral vibrations.

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Application of Steerable Rotary Drilling Technology to Drill Extended Reach Wells
Authors: Colebrook M. A. , Peach S. R. , Allen F. M. , Conran G.
Published: December 2007

A steerable rotary drilling system (SRD system) has been used on several extended reach wells at the Wytch Farm oilfield in southern England.

Recently the SRD system successfully drilled the 8½" hole section of the first well ever to have a step out of more than 10km. The record breaking well, M11SPZ/SPY, has a measured depth of 34,967ft [10,658m] and a horizontal departure of 33,181ft [10,113m]. The reservoir section required rotary drilling techniques to be used. Improvements in drilling operations and reductions in cost were made in drilling the reservoir section. This section was geosteered throughout the reservoir with the SRD system giving control of both the inclination and azimuth.

The 95/8" casing was set from surface to 28,986ft. The SRD system drilled from 29,337ft (MD) to TD at 34,967ft (MD). The SRD system drilled a total of 7,680ft in 44 days (this included a side-track for geological reasons) against the plan of 5,548ft in 49 days. This improvement against the plan was achieved largely by the elimination of the requirement to slide a steerable motor in order to steer the well. Continuous rotation of the drillstring helped reduce drillstring torque and drag and improved hole cleaning. This led to more efficient weight transfer to the bit and allowed higher average penetration rates.
New Information Systems Promise the Benefits of the Information Age to the Drilling Industry
Authors: Close D.A. , Stelly O.V.
Published: December 2007

The Information Highway, although now ubiquitous in the workplace and many homes, has been slow to pave its way to drilling rigs. The levels of networked efficiency that other industries and academia currently enjoy are migrating to upstream oil and gas industry operations. Once these connections are made, meaningful information can be networked to all appropriate parties involved in the well drilling program. The resulting real-time improvement in well knowledge can dramatically improve the efficiency of wellsite operations.

Some progress has already been made as telecommunications, e-mail and even teleconferencing now appear on some of the larger platforms and drilling rigs. The latest information technology advances increase communication efficiency from the rig to the office, but fall short of the potential benefit that could be achieved with the implementation of real-time well site networking. This paper explores the possibilities of cost effective, real-time networking between the wellsite and all interested parties involved in the optimization of the well construction process.

The paper first sets the scene by revisiting and discussing current and prior efforts to increase drilling efficiency using information systems.

The authors then comment on industry barriers that are currently stifling information system proliferation in the exploration and drilling arenas, and explore possible ways to overcome these barriers. The paper then details a newly implemented information system which uses existing rig monitoring systems and intranet technologies, and thus offers a cost effective and intuitive information analysis network for the drilling operation.

The paper concludes by describing the revolution that awaits the industry as information technologies re-engineer the drilling operation, as we know it today.

P. 337
DP and Operability Capabilities of the Dynamically Positioned Drillship Ocean Clipper
Authors: Webb David L.
Published: December 2007

Sea trials and DP trials were conducted on the Ocean Clipper during June and July of 1997. This paper presents a description of the trials procedure and the results of the sea trials and DP trials. In addition, the instrumentation and data gathering techniques used will be discussed.

DP performance is presented in the form of predicted capability plots. It was hoped to be able to define "maximum" environments directly based on the results of the trials, however, extremely mild weather was encountered throughout the entire sea trials period.

Operability performance, as it pertains to the performance of three different drilling related functions, drilling, setting casing and raising/lowering the BOP, will be discussed. The operability predictions present percent down tine for the three operations for a specific location in the Gulf of Mexico. The expected effectiveness of the Flume anti-roll tanks in reducing vessel motion and therefore increasing operability will be discussed.

P. 373
An Instrumented Bit: A Necessary Step to the Intelligent BHA
Authors: Leseultre A. , Lamine E. , Jonsson A.
Published: December 2007

Downhole vibrations is still a problem to solve because models have failed to be predictive and surface measurements do not reproduce downhole phenomena precisely.

The paper describes the instrumentation of PDC bits with accelerometers, strain gauges and contact sensors. From these sensors it has been possible to produce direct measurements in lime domain and frequency domain of: instantaneous RPM, accelerations along the three axis, downhole WOB, downhole torque, power dissipated at the bit, eccentricity of hole, bit center trajectory, also indirect measurements of downhole estimated ROP, wear, specific energy. Military type micro electronics of the latest technology have been used to integrate evervthing in the bit shank.

With these measurements dynamics can be analyzed : stick slip and whirl are clearly identified. Lab tests have been performed with promising results. Three campaigns have been done in the field to confirm the lab results with different bit profiles in France and UK. Some of the recorded results compare well to the results of existing BHA models. The paper discusses these results and outlines the future developments.

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