bluuebunny/crossref_metadata_2025 huggingface dataset:
Reservoir Fluid Sampling and Characterization—Key to Efficient Reservoir Management
Authors: Nagarajan N. R. , Honarpour M. M. , Sampath K.
Published: December 2007

Reservoir fluid properties play a key role in the design and optimization of production processes and facilities for efficient reservoir management. Inaccurate and unreliable fluid characterization leads to high uncertainties in in-place hydrocarbon volume estimates, negatively impacting ultimate recovery predictions and hence the asset value. Obtaining reliable PVT properties of reservoir fluids starts with the acquisition of adequate volumes of representative fluid samples followed by PVT data measurement and phase behavior modeling. Subsequent laboratory analysis should be monitored through established quality control procedures to provide high quality data. The fluid characterization methodology should employ best-practice techniques to model fluid behavior as functions of pressure, temperature, and fluid composition. In this paper, we discuss key steps in sampling and fluid characterization for a wide spectrum of fluid types ranging from extra-heavy oils to lighter gas-condensates including complex near-critical fluids. Using several field examples, sampling tool design and procedures for obtaining representative samples are discussed. Laboratory fluid analysis strategies for various fluid types are highlighted with an emphasis on employing quality control and quality assurance procedures. The importance of special PVT tests to capture fluid behavior under different production strategies ranging from simple depletion to complex tertiary recovery is emphasized. Application of recommended fluid modeling techniques such as C7+ characterization and Gibb's energy minimization are demonstrated through field examples.
Study of Methane Solubility in Organic Emulsions Applied to Drilling Fluid Formulation and Well Control
Authors: Monteiro E. N.
Published: December 2007

The study of the interaction between the formation gas and the drilling fluid during offshore operations is essential to safely and economically drill each phase of the well. The environmental regulatory issues and the peculiar technical aspects involved in deep and ultradeep waters require low toxicity organic drilling fluids. The main objective of this study was to understand the PVT behavior of those fluids by the experimental determination of thermodynamic properties such as: bubble pressure, solubility, specific gravity and formation volume factor of the fluid. Those properties have a direct impact on kick detection and circulation out of the well that should be addressed in well control planning. The experimental data were obtained from a PVT cell pressurized by mercury injection with an operating capacity of 350 °F and 10 kpsia. The gas used was methane and the liquids were n-paraffin emulsions, tested at 158 °F and 194 °F. The influence of the emulsion composition has been analysed and the experimental data for solubility and formation volume factor have been compared with predictions considering the additivity hypothesis.
Remote Well Surveillance at an Adco Field
Authors: Al-Hosani Ameen
Published: December 2007

This paper describes the capability of an oil well surveillance system to perform real time individual well surveillance with minimum costs and modifications to the existing plant. The paper gives an overview of as to a well surveillance system installed at a gathering station can reduce wells downtime and minimize oil production loss.

It also describes the concepts and elements used to integrate a well surviellance system with the existing wells and the hardware designed for the trial. The goal of the trial was to have simple and expandable well surveillance system. While concluding, the overall performance of the system during the trial phase is presented.
Integration of Sonic-VSP-Seismic Data for Reservoir Elastic Properties Evaluation
Authors: Tikhonov A. A. , Dobrynin S. V. , Kerusov I. N. , Glebov A. F. , Petrov E. I.
Published: December 2007

Exploration and production geoscientists use a number of characteristics reflecting such properties of reservoirs under study as structure, lithology, porosity, permeability, etc. Reliability of estimating these parameters defines effectiveness of reservoir development actions. Measuring elastic properties of formation allows computation of a number of parameters characterising reservoir's lithological properties and filtration characteristics. The information about distribution of elastic properties allows estimation of reservoir structure and elaboration of the optimal strategy for reservoir development.

Certainty and reliability of the geoinformation may be dramatically increased using integration of methods, studying elastic properties of reservoir in different frequency bandwidths using seismic waves of different types – longitudinal, shear, converted.

From this point of view, the integration of fullwave sonic log, multiwave VSP and surface seismic data may provide the effective solution for the task of investigating reservoir elastic properties. Integration of information obtained using these methods allows building of a single model that includes features of different ranks.

Observations, which use elastic waves of different types, make it possible to additional calculate such integrated parameters as Poisson ratio and to increase certainty of estimation of such characteristics as lithology and porosity.

Seismoacoustic measurements data, supplemented by log interpretation results, core analysis, hydrodynamic study results, provide a means to dramatically increase quality and certainty of the study.
Further Investigation of Drainage Height Effect on Production Rate in Vapex
Authors: Yazdani A. J. , Maini B. B.
Published: December 2007

Efficient recovery of heavy oil and bitumen is still very challenging and remains a subject of ongoing researches all around the world. Thermal recovery methods are generally accepted as viable and several successful field projects based on CSS or steam flooding or SAGD have been reported. However, these processes are not universally applicable and there are many problematic heavy oil reservoirs that are not good candidates for thermal processes.

Solvent based non-thermal heavy oil recovery methods are relatively new and still under development. The central idea in such techniques is to rely on solvent dissolution for viscosity reduction instead of heating. The viscosity reduction effect of solvents is comparable to that of steam. Among the solvent based methods, Vapex appears to be the most promising. Vapex is the solvent analogue of the SAGD process and uses essentially the same well configuration. A solvent vapor is injected instead of steam and the viscosity reduction occurs due to the dissolution and diffusion of the solvent in the oil. In thin heavy oil and bitumen reservoirs, where the thermal processes are likely to fail due to excessive heat losses, Vapex can be more successful. Nonetheless, the economic viability of Vapex remains uncertain due to much lower oil production rates predicted by scale-up of observed laboratory model results using the transmissibility based scaling criteria developed by Butler1.

In our previously reported experimental work, it was shown that the currently used scaling methods under-predict the increase in oil production rate with increasing drainage height. A bigger height dependency of the oil rates than the square root functionality proposed by the Butler's model1 was found experimentally. This observation was based on physical models of four different sizes, the largest of which was only 60 cm tall.

In this paper, the results of a new set of Vapex experiments are presented. This set of experiments has been carried out in a newly designed very large physical model, which to the best of authors’ knowledge is the largest Vapex experimental model ever fabricated. The results are, interestingly, in very good agreement with the trend of the previous experiments with the smaller models. The previously proposed scale-up relationship2 adequately predict the results obtained with the new physical model. The new results have been used to improve the previously reported empirical scale up correlation for the Vapex process. Conducting the experiments with different sand packs also reconfirms square root functionality of the dead oil production rate to the permeability.
Dual Porosity Equations from Effective Medium Theory
Authors: Berg C. R.
Published: December 2007

Aguilera's1 dual porosity model for fractures and matrix porosity was developed because fractures tend to lower the porosity or cementation exponent (m) of rocks. An assumption in the derivation of the dual porosity model was that fracture systems are parallel with the current direction, i.e. that fracture m (mf) is equal to 1.0. A new equation derived from effective medium theory allows mf higher than 1.0. The new relationship agrees closely with two models by Aguilera which allow mf greater than 1.0. In addition to the dual porosity equation, a new relationship is derived for calculating mf based on fracture orientation relative to current flow.

In the past, dual porosity models for vuggy porosity have mainly used the physical model of resistors in series with the inherent assumption that the vugs were non-touching. A new equation to calculate the effect of vugs on m is derived from effective medium theory. At low total porosity, calculations are very similar to those of the series model, but at higher porosities the results differ, eliminating the need to distinguish between connecting and non-connecting vugs. In addition, vug m (mv) can be varied on the basis of the shape and orientation of the vugs. When mv is raised to high values, the results are equivalent to the dual porosity series vug model.

A triple-porosity method is developed that utilizes adjustable mf and mv from new dual porosity relationships. The model works by first calculating a new, composite m for the bulk porosity and vugs and then it uses that composite value along with mf to calculate a triple-porosity m. When mf is equal to 1.0, the results resemble those of the triple porosity model of Aguilera and Aguilera2, but with increasing values of mf, the effects of fractures on triple-porosity m is dampened.
The Hydrogen Economy: Economics of Hydrogen Production From Natural Gas
Authors: Seddon D.
Published: December 2007

Hydrogen is a principal fuel for high efficiency fuel cell vehicles which produce zero emissions. Hydrogen fuel cell vehicles can be fueled competitively with conventional fossil fuel vehicles if the hydrogen is produced in large central facilities with access to low price gas. For many economies the price of gas is dependent on the price of crude oil (US). In times of high oil price, the production cost of hydrogen should be broadly comparable to the price of petroleum fuels in these economies. In economies in which the price of gas to large industrial users is not strongly linked to the price of oil (e.g. Australia), hydrogen production could be competitive with oil priced at $50/bbl.

The imposition of carbon taxes would impact unfavorably on the production cost of hydrogen from gas and, all other things being equal would require the imposition of additional taxes on fossil fuels to make hydrogen an economic alternative.

Although improvements to the technology of production are being researched, breakthroughs will not make a major difference to the production costs. A great unknown is the cost of reticulation of hydrogen and the distribution pressure required. This cost may make or break the production of hydrogen from gas as a viable technology for transport fuel. Improvements to conventional fuel vehicles, particularly the introduction of hybrids could erode any competitive position of hydrogen fuel cell vehicles.
Analytical Modeling of Chemical Flooding: One-Dimensional Two-Phase Flow Accounting for Ion Exchange
Authors: Pires A. P. , Ribeiro P. M. , Bedrikovetsky P. G.
Published: December 2007

Among different Enhanced Oil Recovery (EOR) methods, the injection of chemical solutions plays an important role in mature fields additional recovery. Analytical models for 1-D displacement of oil by water with chemical compounds have been developed since the 1960's. The interfacial activity and mobility control of a chemical flooding process are affected by the concentrations of the ionic species that are present in the water. This problem involves complex physical-chemical processes of interphase mass transfer, phase transition and transport properties changes. The one-phase displacement solution has been already developed and it is a well-known problem. However, its application is limited to already water flooded reservoirs. In this paper the solution of the two-phase problem is presented. A flow potential associated with the conservation of water phase is introduced and used as a new independent variable instead of time. This technique permits splitting the system of equations into a thermodynamic system and one transport equation. It is possible to show from analytical modelling of multi-component polymer/surfactant flood that the concentration "part" of the solution is completely defined by adsorption isotherms (thermodynamic part, called auxiliary system) and does not depend on relative permeabilities and phase viscosities. The number of auxiliary equations is less than the number of equations in the compositional model by one. Once the multi-component adsorption problem is solved, the 2-phase flow behavior can be predicted. This work shows analytical solutions of 1-D oil displacement by water containing two adsorbing cations and one anion for different salt concentrations in injected and formation waters. Electroneutrality and Gapon equilibrium equation are considered. One of the most important applications of these solutions is design of chemical flooding regardless of the water saturation.
Characterization of Multilayer Reservoir Properties Using Production Logs
Authors: Poe B. D. , Atwood W. K. , Kohring J. , Brook K.
Published: December 2007

This paper presents the results of an investigation concerning the development of a reliable and accurate technique for establishing the stabilized deliverability performance of multi-layer commingled systems using multirate production log measurements. Both linear and non-linear systems are addressed in this paper, providing a basis for the analysis of reservoirs exhibiting Darcy and non-Darcy flow, respectively.

Extension of the conventional Selective Inflow Performance analysis is also presented in this paper to obtain estimates of the formation and well completion properties such as effective permeability, radial flow steady state damage /stimulation skin effect, and non-Darcy flow coefficient. In the specific case where the deliverability performance of a vertically fractured well is considered, estimates of the effective fracture half-length and average fracture conductivity may be derived from the analysis. In cases where the multirate deliverability tests are performed under boundary dominated flow conditions, conventional deliverability analysis techniques may also be employed to derive estimates of the reservoir drainage area in addition to the well and reservoir parameters that can be obtained in a transient flow analysis. Applications of the analyses reported in this paper demonstrate the use of the analyses to evaluate the inflow performance measurements of commingled multi-layer reservoirs obtained using multi-rate production logs.
Production Performance Design Criteria for Hydraulic Fractures
Authors: Poe B. D. , Marique J. F.
Published: December 2007

This paper presents the results of an investigation of the design and analysis of the boundary-dominated flow production performance of a vertically fractured well located in a closed rectangularly bounded reservoir. The solution for dimensionless productivity index of a finite-conductivity vertically fractured well in a closed rectangularly bounded reservoir and the corresponding pseudosteady state shape factor of this type of well and reservoir completion under boundary-dominated flow conditions has been developed and utilized in this study.

The mathematical model described in this paper has been used to develop predictive and analysis graphical design charts of the dimensionless productivity index and pseudosteady state shape factors for use in improved hydraulic fracture stimulation design and evaluation. Example applications of the dimensionless productivity index and pseudosteady state shape factor solutions developed in this work are provided for fracture stimulation design. A production optimization strategy is presented in this paper based on the dimensionless productivity index solution for a vertically fractured well under pseudosteady state flow conditions.
Underbalanced Drilling Experience in PDO
Authors: Al-Saadi Anwar , Al-Bahlani Salah , Al-Mahrooqi Salima , Al-Riyamy Moutaz , Carrera Mariano , Bowling John , Al-Balushi Ahmed
Published: December 2007

In July 2004 a Northern Oman Carbonate reservoir asset team embarked on an Underbalanced Drilling (UBD) campaign after a detailed feasibility study. The main objectives of the UBD campaign were to improve the Productivity Index (PI) and test the validity of real time reservoir characterizations (RTRC) in UBD operations.

To date 16 wells have been successfully drilled UBD resulting in almost double the PI and better initial well production with a decline trend better or comparable to the offset conventional wells in the area.

Real time reservoir characterizations (RTRC) helped identifing the features contributing to water production and enabled real time decision making to optimize well path and sometimes extension of the well length by correlating real time resistivity data with real time production. RTRC also enabled optimum completion selection to maximize production as well as ESP sizing and installation of proper water shut off mechanisms (the preferred water shut off method is expandable Open Hole Clad "OHC"). Reservoir and geological models were updated in accordance with this analysis.

Other benefits seen from the UBD campaign include eliminating the need for stimulation, TLC logging (i.e. MPLT, FMI, etc…) and curing losses while drilling the reservoir section along with technology maturation of improved Down Hole Isolation techniques and the running of the OHC in UB situation.

A key success factor was the assimilation of a multidisciplinary integrated team comprising of the asset team, well engineering, new technology, drilling and UBD contractors. They all contributed to the success of UBD campaign which resulted in new oil delivery ahead of time and within budget.

As a result of the high success of the UBD campaign in 2004/2005 the asset team decided to drill all its oil producers underbalanced.

However, the challenges that have arisen are mainly in the cost of UBD packages and services as well as improving the reliability of some of the well control tools such Down Hole Isolation Valves (DHIV) and the application of contingencies in case of their failure.
3D Field-Scale Automatic History Matching Using Adjoint Sensitivities and Generalized Travel-Time Inversion
Authors: Daoud A. M. , Vega L.
Published: December 2007

Conditioning geologic models to production data is generally done in a Bayesian framework. The commonly used Bayesian formulation and its implementation have difficulties in three major areas, particularly for large scale field applications. First, the CPU time increases quadratically with increasing model size, thus making it computationally expensive for field applications with large number of parameters; second, the sensitivity coefficients that define the relationship between reservoir properties and the production response typically depend on either the number of model parameters or the number of data points; and third, the calculation of the prior covariance matrix (or its inverse) can be time consuming and memory intensive.

We propose a fast and robust adaptation of the Bayesian formulation for inverse modeling that overcomes much of the current limitations and is well suited for large-scale field applications. Our approach is based on a generalized travel time inversion and utilizes the adjoint method for computing the sensitivity of the travel time with respect to reservoir parameters such as porosity and permeability. The sensitivity calculations depend on the number of wells integrated which can be orders of magnitude less than the number of data points or the model parameters. The adjoint sensitivities can be computed from the pressure and water saturation distribution that is readily available from the numerical simulator. For solving the inverse problem, we utilize an iterative minimization algorithm based on efficient singular value decomposition. Prior information is incorporated using an approximation of the square root of the inverse of the prior covariance calculated using a numerically-derived stencil applicable to a wide class of covariance models. Our proposed approach is computationally efficient and more importantly the CPU time scales linearly with respect to model size making it particularly well-suited for large-scale field applications.

We demonstrate the power and utility of our approach using synthetic and field examples. The synthetic examples show the robustness and efficiency of this algorithm. The field example is from the Goldsmith San Andres Unit (GSAU) in West Texas and includes multiple patterns consisting of 11 injectors and 31 producers. Using well log data and water-cut history from producing wells; we characterize the permeability distribution, thus demonstrating the feasibility of our approach for large-scale field applications.
Investigation into Strengthening Methods for Stabilizing Wellbores in Fractured Formations
Authors: Soroush H. , Sampaio J. H. B.
Published: December 2007

Over the last decades, drilling through fractured and unstable formations has proven to be challenging, specially in terms of wellbore instability. Stability of boreholes in these scenarios requires a careful consideration of in-situ stresses, rock strength, pore pressure, wellbore fluid pressure and drilling fluid characteristics. This issue is more critical and complex in fractured rocks, because of the need to consider more parameters than in other kinds of rocks. In fractured formations, fractures play an important role and rock wedges movement controls the instability. Also, fractures fillings are of paramount importance. In spite of this fact, there are only a few studies on stability of fractured rocks and their strengthening methods.

The present paper aims to provide insights into wellbore stabilization in fractured rocks. A broad literature review was conducted on existing formation strengthening methods and their effectiveness for fractured formations. The work concludes with some recommendations for these kinds of formations and proposed topics for additional research and development.
Designing Hydraulic Fractures in Russian Oil and Gas Fields to Accommodate Non-Darcy and Multiphase Flow-Theory and Field Examples
Authors: Dedurin Andrey V. , Majar Vadim A. , Voronkov Andrey A. , Zagurenko Alexey G. , Zakharov Alexander Y. , Palisch Terry , Vincent M. C.
Published: December 2007

Non-Darcy and multiphase flow effects in hydraulic fractures have been well documented during the last several years. The pressure losses due to these phenomena are widely accepted to be of great significance in most gas well completions in the United States and elsewhere. While the importance in gas wells is evident, the authors pose the question of whether non-Darcy and multiphase flow effects are of concern in typical oil wells in Russia.

For the analysis, the authors evaluate three primary categories of Russian production wells: gas wells, oil wells producing above the bubble point, and oil wells producing below the bubble point. For each category, the authors describe the significance of non-Darcy and multiphase flow effects using fracture flow theory as well as state-of-the-art fracture production models. This paper will illustrate that non-Darcy and multiphase flow effects can substantially decrease the production potential of gas wells, as well as many of the oil wells found in Russia that are producing below the bubble point.

Historically, Russian oil wells have been intentionally operated above the bubble point. However, more aggressive well designs have recently been shown to increase production by over three-fold. The authors explore the economics of producing these wells below the bubble point and show that for these more aggressive strategies, the effects of non-Darcy and multiphase flow can be significant and should be accommodated during fracture design.

The authors propose solutions for mitigating these effects through various modifications to the fracture design including the impact of proppant selection on performance. Several operators within Russia have already successfully accounted for these phenomena in their fracture designs, and new field examples are explored, analyzed and presented in the paper. Recent field results are presented for Gazpromneft's Achimovskoya formation BV8 in Tomsk region (Western Siberia) and BP-TNK's field near Buzuluk in the Orenburg region (Volga-Urals). The results found here are compared to published results from the Achimovskoya sandstone in the Kalchinskoye oilfield, the BP12 formation of the Vyngayakhinskoe field, the Priobskoye and Sugmutskoe oilfields, and Gazprom's Yamburskoe gas condensate development.
Integrated Flow Assurance Modeling of Angola Block 18 Western Area Development
Authors: Watson M. J. , Hawkes N. J. , Pickering P. F. , Elliott J. , Studd L. W.
Published: December 2007

As oilfield developments become more technically and economically challenging, Flow Assurance has become crucial to the feasibility of projects. Consequently, Flow Assurance issues, such as hydrates or wax deposition must now be considered early in concept selection. Modern numerical methods, coupled with the latest software engineering techniques, now allow the rigorous calculation of multiphase thermal-hydraulic behaviour in an integrated asset model (IAM) on timescales acceptable for concept selection. The paper describes the application of a new IAM tool to analyse options for the development of fields in the Western part of BP's Angolan deepwater Block 18. Novel aspects include the embedding of field scheduling rules such that the drilling schedules were predicted automatically from the model. In addition, different field architectures were considered, including tubing and pipeline sizes, looping of pipelines and subsea multiphase boosting, and the impact on production rates and drilling schedules was quantified. Furthermore, the option to tie back to the planned Greater Plutonio FPSO was also modelled with the forecast ullage profile being imposed on production from the new fields. All calculations were performed using rigorous multiphase thermal-hydraulic models allowing Flow Assurance constraints to be analysed simultaneously.
History Matching Considerations of an Analogue Reservoir Model (ARM)
Authors: Montague E. T. , Sherlock D. H. , Santoso E.
Published: December 2007

This paper describes a research program at the Australian Resources Research Centre (ARRC) to establish and use an analogue model to gain insight into issues of uncertainty in numerical reservoir simulation. Reported in this paper are the initial findings from history matching the production response of an Analogue Reservoir Model (ARM) and its numerical representation in a finite difference simulation model. The ARM is a large-scale physical model comprising two intersecting synthetic sandstone channels encased within an impermeable acrylic matrix. The initially oil-saturated model was waterflooded via the upper channel and the injected water was dyed blue to allow the displacement process to be recorded on video. Production rates, pressures, water cuts, etc were recorded and used to history match the reservoir simulation model.

The simulation model was built using Roxar's Nextwell software, and populated with the rock and fluid properties of the ARM. The initial history matching attempt did not yield a good match. The model was unable to match the preferential flow of water along the lower channel. It was discovered later that the lower channel had become inadvertently fractured during fabrication of the model. Although incorporating the fracture system into the simulation model significantly improved the quality of the history match, the character of the water cut development was dependant upon the relative permeability curve used. It has been well documented that different relative permeability curves are used to model fluid flow through porous media as opposed to fracture and fracture-matrix flow This ARM provides a unique opportunity to test the applicability of published fracture relative permeability models by using these in history matching the production response between the reservoir simulation model and the physical model.
Modeling of Coupled Reservoir and Multifractured Horizontal Well Flow Dynamics
Authors: Vicente R. , Ertekin T.
Published: December 2007

A fully implicit numerical model coupling reservoir and multifractured horizontal well flow dynamics has been developed to investigate the flow behavior and predict the productivity of such systems. The simulator solves simultaneously for pressure distribution within the reservoir and horizontal well domains, while taking into account the friction losses along the wellbore for laminar and turbulent flow conditions. Fractures with distinct properties are placed perpendicular to the wellbore axis and can intersect the well at arbitrary locations. The model is unconditionally stable and can be used to analyze the early transient period as well pseudo- and steady-state conditions.

The use of multifractured horizontal wells has been gaining popularity in tight reservoir systems; however, the existing design protocols do not consider wellbore hydraulics that can have a governing role in the performance of the system. The appropriate design of a multifractured well has a definite impact on its performance. The numerical model presented in this paper can be utilized as a design tool towards the optimization of the number, position and penetration lengths of the fractures connected to a horizontal well.

The calculated influx and pressure distributions along the wellbore show that solutions can deviate dramatically from the actual behavior if infinite conductivity idealization is used to represent flow dynamics in the horizontal well, and this discrepancy becomes more pronounced with an increase in reservoir permeability. Parametric studies are conducted to evaluate the influence of the number of the fractures in the flow behavior and productivity of the system. The observations and analyses presented in this paper will provide the much needed guidance to engineers who face the daunting task of designing a cost-effective optimum fracturing scheme in horizontal wells completed in formations with different flow characteristics.
A New Asymmetrical Array Induction Logging Tool
Authors: Xiao J. , Buchanan J. , Bittar M. , Davis E. , Sanmartin L. , Hu G. , Zannoni S. , Morys M. , Liu W.
Published: December 2007

While array induction tools are fast approaching the 20 year mark for commercial service, a few nagging questions persist in the minds of induction tool designers. These questions relate to some of the compromises in hardware design and data processing that were necessary in the previous generation of tools. These compromises can give rise to various uncertainties in the data that ultimately degrade log responses. A new array induction tool has been designed that addresses these issues.

All array induction tools promise radial resistivity curves with focal depths ranging from 10 inches up to 120 inches. However, few users are familiar with the potential uncertainty that stems from the design of the fundamental sub-arrays. In the new tool, dedicated sub-arrays are closely associated with each computed radial curve. By doing so, the new tool produces radial curves with a minimum of extrapolation. The payoff for the user is more accurate radial resistivity curves and a higher fidelity description of the formation and the near wellbore environment.

This paper also describes the progress made in calibration methods and correction for thermal effects. While these subjects typically receive little attention in the literature, they are critical to the accuracy and repeatability of array induction measurements. The rigorous calibration method described in this paper assures accuracy across a large population of tools and also insures insensitivity to the calibration environment. The complexity and magnitude of thermal effects on array induction tools is examined alongside a robust, thermodynamic method for correcting them.

Finally, several other methodologies are highlighted. A skin effect correction method uses only the in-phase signal measurements and corrects for the skin effect in the aspect of the apparent conductivity value and in the aspect of geometric factors as well. A real time borehole correction method computes the borehole effect with adaptively inverted borehole size, tool eccentricity, and mud resistivity. A new inversion methodology improves the efficiency and stability of the realtime radial inversion.
Treatment of Seawater With Cartridge Filtration—A Field Trial
Authors: Lee J. M. , Frankiewicz T. , Walsh J.
Published: December 2007

In offshore operations, seawater is often injected to maintain reservoir pressure for enhanced oil recovery. A sulfate reducing membrane (SRM) is typically used to reduce the sulfate content in the seawater from 2900 mg/l to less than 50 mg/l to prevent souring of the reservoir by sulfate reducing bacteria and formation of barium and strontium sulfate scale when seawater is mixed with formation water. A two cartridge in series filtration pilot unit installed on a deepwater platform in the Gulf of Mexico has demonstrated that cartridge filtration can be used upstream of the SRM to pretreat seawater to meet the SRM feed seawater specification of SDI<5 and NTU<1. Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) was used to determine the composition of the material deposited on the surface of a used cartridge filter. From the SEM/EDS results, it was concluded that the filters were blocked predominantly by coccoliths (calcium compounds), diatoms (silicon compounds), iron oxide corrosion products, and broken, crushed marine debris, that formed a fine grained membrane cake on the filters. It was found that a two filter in series configuration is a better seawater filtration system than just using one single filter if seawater with an SDI < 3.5 is required. With the installation of a 50 micron nominal filter upstream of a 10 micron absolute filter, the service life of a 10 micron filter was increased by 20 times.
Snohvit and Beyond—Setting New Standards for Subsea to Shore Developments
Authors: Witting Fredrik
Published: December 2007

This paper discusses the area of long subsea tie-back developments, and what the limiting factors and related technology barriers are related to this area. The paper starts by providing a brief overview of the Snohvit subsea development in the Barents Sea, which holds the current world record in tie-back distance, from an all-subsea development back to shore. On the basis of the technical solutions for the Snohvit development, the paper goes on to discuss what the technical implications would be if the tie-back distance was extended to a level of about three times that of the Snohvit development, thereby making the system able to accommodate ultra-long step-out distances, including even some of the most remote E&P prospects currently known to the industry.

The paper concludes that step-out distances of these magnitudes would be technically feasible, based on use of technology solutions from the Snohvit development and more or less conventional subsea technology building blocks. An important exception from this, however, would relate to the area of providing high levels of subsea electrical power over long distances. For many all-subsea developments with long step-out distances, subsea high voltage power distribution will be required to provide sufficient power to support subsea gas compression schemes. The required power levels and transmission distances far exceed the current capabilities of the industry in this regard. Therefore, the feasibility of such field development concepts will necessitate development and implementation of technological solutions to meet this challenge.
Well Engineers Deserve a Seat at the Exploration Table: The Role of Mechanical Earth Modeling in the Early Exploration Process
Authors: Goodman H. E.
Published: December 2007

Consideration of the full cycle asset development plan from appraisal through abandonment reduces the risk of missed future opportunities caused by well systems design constraints. For example, reservoir pressure depletion and subsidence can impact borehole stability to the extent that complex well designs are necessary to fully exploit the asset. Well placement not only depends on the subsiding reservoir section, but also on the reaction of the overlying geological section that must be drilled through to reach the reservoir. For land-based operations, the consequences of well complexity may be more easily addressed, the downside being a poor estimate of field recovery that can either rob opportunities for outlying prospects or, in the worst case, cause the asset to be uneconomic. For major capital projects (MCPs) such as deepwater subsalt fields, the capital outlays are immense, with single wells costing up to $100,000,000. For these deepwater MCPs, fewer wells are required to produce reliably for longer periods.

The capability to characterize rock mechanical properties from the standard P-wave acoustic datasets, either seismic or openhole log derived, enables well planners to link the Explorationist and Well Engineer's visions using mechanical earth modeling technology. The accurate assessment of formation rheology, or stiffness, and architecture (distribution and structure), allows the asset team to optimize well systems design, considering placement and production management practices over time.

The presentation will introduce acoustics-based rock mechanics concepts, describe the acoustics-based rock property prediction technique, and present field applications that demonstrate the impact of the subsurface model to the corresponding well systems design.
Environmental Challenges of Heavy Crude Oils: Management of Liquid Wastes
Authors: Neff Jerry M. , Hagemann Randi
Published: December 2007

Large volumes of produced water are generated during production of heavy crude oil and large volumes of surface water often are needed to produce, transport, and upgrade heavy crude oils and bitumens. The most important alternatives for managing produced and process waters include volume minimization, underground injection, discharge to surface waters, and beneficial reuse. Produced and process waters often contain high concentrations of inorganic salts, metals, hydrocarbons, and organic acids. They may cause ecological damage if discharged untreated to surface waters or soils. Salts harm terrestrial vegetation and naphthenic acids and polycyclic aromatic hydrocarbons are toxic to aquatic organisms. Most produced water is either reinjected into a non-producing formation or used for enhanced oil recovery (EOR) technologies, such as cyclic steam stimulation (CSS) and steam-assisted gravity drainage (SAGD), or bitumen transport and upgrading by slurry pumping and alkaline extraction. Before use or discharge to surface waters, the produced water must be treated to remove dissolved salts, organic acids, hydrocarbons, and suspended solids. Wastes from cold heavy oil production with sand (CHOPS) usually are pumped to stock tanks where the gas, water, oil, and solids are separated and the produced water is piped to a disposal well. The solids are stored in tailings ponds. Wastes produced during processing oil sands bitumen from surface mining with hot alkaline water also are stored in tailings ponds. Water may be decanted from the tailings ponds and reused or reinjected into a non-producing formation. Tailings ponds containing mature fine tailings may be reclaimed as lake basins. Several new technologies are being developed to remove salts, organic acids, and hydrocarbons, and to break stable heavy oil-water emulsions so that produced and process waters can be reused without damaging production equipment and producing formations or discharged without harming the environment.
Integrating Seismic-Derived Porosity Into a Geocellular Model—A Case Study
Authors: Mercado Gary , Ikawa Hidemasa , Elhami Mohamed , Belgaid Adel
Published: December 2007

The goal of this study was to create a 3D seismic based porosity volume for specific carbonate reservoirs zones and integrate this derived porosity into a geocellular model containing 257 points of well control porosity. The 3D marine OBC seismic data covered a 1500 km2 area of a super-giant Middle East oil field. The Late Cretaceous reservoirs in the field consists of limestone and dolomitic limestone and target zones are subdivided into 3 alternating porous and dense zones. The porous zones range from 30-40 feet thick.

The data was inverted to pseudo acoustic impedance using a well-driven model based technique. Sixty two wells were used to create the initial impedance model for the seismic inversion mainly to provide low frequency trend which tied the log data to the seismic data. A neural network process was applied that utilized the seismic inversion data with several other seismic-derived attributes, in order to maximize the correlation values in reservoir zones and minimized PHIE prediction error in the created porosity volume in time domain.. The seismic based porosity information was depth converted and read into a geocellular model and used as trend data.

Geostatistical methods are commonly used to integrate seismic derived porosity, since it honors well data as well as the degree of correlation between seismic pseudo-porosities and log porosities. This method can create a 3D model that takes advantage of the well log data's fine vertical resolution and the seismic attribute's lateral resolution. The geostatistical method used to achieve this is collocated cokriging. Collocated cokriging can be utilized with two methodologies: kriging (interpolation) and conditional simulation. The first approach is a deterministic method, whereas the latter approach attempts to honor the spatial variability of the conditioning data and also provides multiple realizations.

The lateral distribution of the porosity, controlled by the seismic data in between the wells enable an accurate estimate the inter-well petrophysical properties which had a great impact on the uncertainty in the volumetric calculations of these reservoirs. Validation of this approach was blindly tested by the new drilling locations in the field.
Enhancement of Leakoff-Tests Values in Plastic Clays by Mud Additives— A Case Study in Deepwater Wells in the Krishna Godavari Basin Offshore India
Authors: Singh Raj K. , Holasek Fred R. , Gulati S. C. , Ratan Vijay , Thyagaraju B. A.
Published: December 2007

Common characteristics of deep water wells are narrow separation between pore pressures and fracture gradients along with, comparatively with onland, lower values for the latter. Well designing for such scenario is always been a challenge for drilling engineers. To win over this situation, often-inevitably, wells are designed with multiple casing plans leading to higher cost for already cost intensive deepwater projects. Drilling with manageable losses has been employed as a tool to reach target depths set for sections of the well. Drilling fluid additives are also effectively being used and promoted as LOT enhancers or formation-break-down-pressure improvers based on tests carried out in laboratories.

The paper presents a study of demonstration and evaluation of the performance of a mud additive (sulphonated asphaltic resins) based on extended leak-off-test values.

The paper reports results from an extensive case study carried out in a major ONGC deep water project involving several deep water wells in Krishna-Godavari Basin offshore, India.

The results presented are the demonstration of the role of mud additive in enhancing LOTs in deepwater wells as well as the validation of the technique applied for evaluations as the study incorporates sample and control well strategy for this purpose.

The drilling fluid additive was successfully employed for improving leak-off-test values/break-down-pressure in the deepwater project.

Performance of mud additive for improving LOTs by extended leak-off-test method employing digital data was evaluated and the same may be used for general application.
Underbalanced Drilling in Saudi Arabia-Start Up Experience
Authors: Muqeem M. A. , Al-Jeffre A. M. , Jarrett C. M. , Al-Khanferi N. M. , Killip D. R. , Abdul H. J.
Published: December 2007

This paper describes Saudi Aramco’s initial experience introducing Underbalanced Drilling (UBD) technology in the Ghawar field. The intention was to prove that a step change in performance could be achieved by the application of this technology. Thus the intent was to optimize well design that will result in reduced unit well cost. The reasoning for applying this technology in power water injection wells (PWI) was the low risk involved in drilling these wells. The primary objective of drilling wells underbalanced was to eliminate formation damage and improve injectivity, thereby eliminating the need for acid stimulation. Further, increased rate of penetration (ROP) will result in reduction in drill time and cost. A major campaign was implemented in the Ghawar field to evaluate UBD in Saudi Arabia. Injection rates were dramatically improved and the need for acid stimulation was eliminated. ROP increased significantly when compared to conventional PWI wells. By the time this paper was completed, three oil wells had been drilled underbalanced. The drilling operations and some of the safety issues only will be highlighted. The operations and results are still being evaluated and hopefully will be presented in the near future.