bluuebunny/crossref_metadata_2025 huggingface dataset:
Recovery of a Damaged Jackup Following Hurricane Rita
Authors: Stonor R.W. P. , Hoyle M.J. R. , Brekke J. N. , Keaton C.
Published: December 2007

The paper describes the analyses and procedures used to recover a jack-up which had been hit by Hurricane Rita and though still standing took on a tilt of three degrees and suffered some leg damage. Initial recovery attempts resulted in further leg damage at which stage it was decided to apply temporary leg strengthening and undertake a more detailed evaluation and analysis of the best methods of recovering the unit. The strength of the soils was found to be providing restraint which helped to support the tilted configuration but was also having the effect of resisting the leveling of the unit and thereby causing further leg damage. The analysis identified the need for a hold-back force during the recovery procedure to prevent further bracing damage in the legs and avoid a complete collapse mechanism developing. A suitable barge pull-back system was developed and in December the operation to recover the unit took place successfully.
Application of Small Vibration Logging Tool Yields Improved Dynamic Drilling Performance
Authors: Perez Daniel , Lockley Russ , Clarke Alan J. , Hanley Chris M.
Published: December 2007

The oil industry is increasingly interested in drilling dynamics as a primary cause of drilling inefficiency. It has become ever more important to be able to both accurately predict and detect downhole vibration/instability throughout the entire drill string. The drill bit is often assigned as the cause, and frequently bears the scars of dynamic drilling problems. Historically bit manufacturers have used a combination of dull grades and surface data to speculate on cause and effect of downhole events with insufficient attention to what may be occurring in between.

A small vibration logging tool has been employed in hundreds of applications worldwide. This paper discusses the implementation of this device and its flexibility for placement of multiple tools in various locations, such as specific built subs and/or existing tools, within the drillstring. The versatility of this tool design offers the possibility to be run with any type of bit, fixed cutter or roller cone, regardless of manufacturer thus making it transparent to drilling operations throughout the entire drilling assembly.

Specific field cases will be presented including; validation of pre-run dynamics modeling software, rotary steerable tools, concentric and eccentric hole opening tools, and response of different BHA configurations. This type of data is important to further the understanding of drill bit, drillstring component, and overall drillstring dynamic performance.
Integrating Safety Leadership and Cultural Change
Authors: Siokos George , Karish John
Published: December 2007

Getting to a position of an incident free workplace requires a multi-faceted approach that involves investment in ensuring the integrity of equipment, systems and people's behaviour.

Consistent leadership that embraces the need to address the above is a pre requisite for success. Moreover, a consistent leadership philosophy, supported by a clear vision and values for success is also required.

Experience suggests that most people in leadership positions want to do the right thing in relation to achieving a safe workplace. Perhaps the real issue is not ‘how’ to make this happen.

This paper focuses on the work done by ENSCO International, Inc., a major international offshore drilling contractor, to enhance its culture through a Corporate Safety, Health & Environmental (SHE) Leadership Development Program and strategy designed to develop leaders who are able and willing to make a difference in safety.

What makes this work different?

Firstly, the Program and strategy integrates prescribed leadership competencies aligned with the organization's vision, values, strategies and safety management system.

Secondly, it involves the top 150 operations leaders in the organization, as a way of giving depth and spread of the safety culture it wants to create.

Thirdly, there is focused follow up to assist leaders put into place changes required for effective safety outcomes.

Fourthly, the leadership strategy is linked to other local business unit safety leadership programs to ensure alignment and synergy.

Fifthly, the SHE Leadership Development Program challenges participants with personal feedback on their SHE leadership competencies and behaviors and encourages the development of a personal leadership development action plan that supports the safety culture demanded by the organization.

This strategy has already delivered observable and valued results.
A Literature Review on Smart-Well Technology
Authors: Gao Changhong , Rajeswaran T. , Nakagawa Edson
Published: December 2007

Smart well technology is one of the most significant breakthroughs in production technologies during recent years. It enables operators to actively monitor, remotely choke or shut selected zones with poor performance without intervention. During early stages of development, electrical control systems and electronic sensors were applied. However, the service companies abandoned these earlier systems due to their poor reliability. Recently, innovation in fiber optic sensors and hydraulic control systems has significantly improved the reliability, and the market adoption of this new technology is accelerating. This paper describes the typical components of smart well systems from the major service providers. Several typical field applications are reviewed, including cases in North Sea, offshore England, and offshore Brunei.
Sensitivity Study on the Main Factors Affecting a Polymeric RPM Treatment in the Near-Wellbore Region of a Mature Oil-Producing Well
Authors: Vazquez O. , Singleton M. , Sorbie K. S. , Weare R.
Published: December 2007

This paper describes a sensitivity study on the main factors affecting a polymeric Relative Permeability Modifier (RPM) treatment in the near wellbore region of a mature oil producing well. The study is divided into several parts where various factors, which affect the application of RPM technology in a chosen field base case well, are studied. These factors include the effects of instantaneous vs. kinetic adsorption for the treatment and the further influence of treatment properties, reservoir fluid properties and the reservoir formation. From the sensitivity study, we can conclude that the most influential factors in the treatment response, i.e. the water cut reduction, are the combination of polymer adsorption type (kinetic or equilibrium) with method of application of the resistance factors (threshold or variable), resistance factor ratio, reservoir fluid properties and reservoir layout. On the other hand, the polymer viscosifying effect is not such an influencing factor, and neither are the shear stress, salinity, hardness and pH that subsequently affect this property.

The sensitivity study was carried out using a model capable of describing RPM treatments in the near wellbore region. The model is a radial, isothermal, two-phase, multi-component and multi-layer mathematical model. The model considers the immiscible displacement of the oil and water phases along with polymer transport in the aqueous phase. The various phenomena that describe polymer flow through a porous medium are also considered and modelled. For each of the various physical phenomena (e.g. adsorption, fluid rheology, resistance factor, etc.), we must then make decisions about its behaviour, which is simulated by choosing certain models and the parameters in these models. For multi-layer systems, the model considers no vertical communication between layers, thus the pressure drop across the various layers remains equal. The model includes kinetic adsorption and the application of resistance factors based on a polymer adsorption threshold, which are not normally available in other models. The model has been verified by comparison with both analytical solutions and Eclipse 100 results and novel observations of kinetic and equilibrium adsorption in radial coordinates are described.
A Detailed Comparison of Experimental and Numerical Data on Hydraulic Fracture Height Growth Through Stress Contrasts
Authors: Jeffrey R. G. , Bunger A. P.
Published: December 2007

This paper compares height, length, width, and pressure data from a laboratory experiment to predictions from a planar 3D hydraulic fracture model for the case of a fracture propagating in a lower stress payzone region bounded by two symmetric higher stress barrier regions. A laboratory method that creates step-like stress changes on an interface between two transparent PMMA blocks is described. A fracture is propagated along this interface while measuring fracture geometry and full-field fracture width (opening) by analysis of the light intensity in images of the growing fracture. The fracture grew in overall height to 1.7 times the pay height and in half-length to 3 times the pay height. Results from a planar 3D numerical model match closely to the experimental data for overall fracture shape, height growth, and injection pressure. The data are presented so that other numerical models can compare with these detailed measurements.
New Experience in Water Wells Aquifer Section Drilling With Saturated Sized Salt Fluid System on Kharyaga Oilfield, Timan-Pechora Region of Russia
Authors: Bulgachev R. V. , Pouget P.
Published: December 2007

Drilling water wells on Kharyaga oilfield, Timan-Pechora region of Russia, often resulted into poor water production due to aquifer formation plugging with weighting materials and drilled solids and insufficient filter cake removal.

Bentonite-based drilling fluids have been traditionally used for water wells drilling in this area. Bentonite particles invasion into the unconsolidated sand water-bearing horizons is almost impossible to prevent and cure, so in most of the cases actual water production rates achieved proved to be lower than estimated ones. Also, when the wells were put on production considerable sand control related issues often occured. During the drilling phase, when passing through unconsolidated sands, borehole instability problems due to sands washout and hole sloughing have been frequently experienced.

In order to avoid considerable formation damage, borehole instability and increase water production, saturated sized salt drilling fluid system has been proposed for two water wells drilling.

Saturated sized salt drilling fluid has been formulated by water saturation with sodium chloride salt following by treatments with modified sized salt of appropriate grade and additions of alkalinity, filtration, viscosity and foaming control agents. The system showed very stable properties throughout operations with tight LPLT filtration, good thin and smooth filter cake and perfect rheological characteristics. Drilling and coring operations in sand and clay formations have been performed with no problems, neither several days of stand-by had any influence on wellbore stability. Electric logs have shown perfect in-gauge hole.

After the section has been drilled and liner with filter screens has been run to bottom, the filter cake was easily removed by displacing and circulating hole with fresh water to dissolve sized salt particles.

When the water wells were put on production, both of them have shown very good production rates in comparison with other water wells drilled in the field and in comparison with estimated production rates for these two wells also. No signs of sand/fines control related issues have been either experienced during more than two years of water production.
A New Model for Matching Fracturing Fluid Flowback Composition
Authors: Gdanski Rick , Weaver Jim , Slabaugh Billy
Published: December 2007

Recovery of fracturing fluid is considered a critical aspect for achieving production performance that meets the expectations of fracture treatment designs. Fluid recovery is often described simply as a percentage of load recovery on a volume basis, without consideration of the composition of the recovered water. Some of this water may in fact be formation water and not original load water at all. Analysis of the ionic composition of the water can determine whether the recovered water is formation water or treatment water. This paper describes a new model that embodies the physics of flow during back-production of a fracturing treatment and incorporates a chemistry "layer" that allows for matching fracturing fluid flowback compositions. The model accommodates formation water having a separate composition from the fracturing fluid. The movements of sodium, potassium, chloride, sulfate, carbohydrate, boron, etc. are modeled during shut-in and production. The compositions of the produced water calculated by the simulator were compared to field production samples.

The process of matching the produced water analyses after the fracturing treatment first required a good match of the produced water rates as a function of both time and the produced gas rates. Reservoir and fracture properties were optimized to match the water production. The ionic composition of the flowback water was then matched by adjusting various parameters that might affect how the water was recovered from the reservoir. The information obtained by adjusting these parameters includes relative permeability curves, capillary pressure curves, and some fracture structure details. Deviations of the model from the observed return profiles indicated areas where the understanding of fluid chemistry and physics of flow might be improved.
Event-Targeting Model Calibration Used for History Matching Large Simulation Cases
Authors: Selberg Stig , Schulze-Riegert Ralf , Stekolschikov Konstantin
Published: December 2007

Large simulation models with excessive simulation time are traditionally a challenge for the reservoir engineer. This paper introduces a new concept of Event Targeting Model Calibration used for History Matching and Uncertainty Quantification in Reservoir Simulation. It is shown that the history matching process of large reservoir simulation models can be significantly improved by coupling different experimental design, optimization and analysis techniques.

Assisted history matching techniques using stochastic and direct search methods have already proven to outperform manual workflows on small and moderate size simulation models. The application of the same techniques and methodology when confronted with the largest simulation models (defined by long simulation times) have proven challenging. A more sophisticated use of the assisted history matching tool box is necessary to utilize CPUs for multiple simulation models as efficient as possible even if distributed computing capabilities are available.

The paper describes a workflow employing assisted history matching techniques to handle ‘monster’ simulation models. An Event Targeting Model Calibration work process is introduced which focuses on key historical events and divides the production history into main time periods. The optimization algorithms usually used in assisted history matching studies are replaced by experimental design methods to investigate the different time periods. Analysis techniques like a newly implemented cluster analysis is used to identify alternative history matched models in a multi-objective optimization formulation. Optimization algorithms are finally used for fine-tuning purposes. In this framework, a remarkable improvement of both the history matching process and uncertainty quantification is possible. This is a significant break through, improving the capability of understanding reservoir uncertainties for large field developments.

This paper summarizes experiences from several different complex history matching studies and outlines guidelines to apply state-of-the-art optimization techniques in combination with experimental design methods to the problem of History Matching and Uncertainty Quantification of large simulation cases.
The Mythical Second Fracture and Its Optimal Placement for Maximizing Production
Authors: Surjaatmadja Jim B.
Published: December 2007

Placing a fracture in a formation is obviously well understood in our industry and has been practiced successfully for quite some time. Recently this capability was refined to enable initiation of a fracture into a specific direction through the introduction of super-high-energy jetting. Despite the developments and experience in fracturing technology and know-how, it has still not been possible to know where a far-field fracture goes—we know it will go to the local minimum stress direction—but we do not know what direction that will be. It is most probable that the far-field fracture will go to a less-than-desired area in the formation and result in only an "acceptable" improvement in production.

Recently, it has been shown that refracturing actually creates new fractures in the formation, rather than simply reopening old fractures, as was commonly thought. Even reopened fractures are now known to result in new areas being reached by the fractures. It is the opinion of this paper that these new fractured areas are not substantially different from the areas reached by the first fracture because local depletion enhances the effects of the original stress regime.

This paper discusses the generation of multiple, consecutive fractures created in a way that enables them to reach formations in a manner not reached before using conventional means. In this scheme, the first fracture achieves "acceptable" production goals. If the process stopped at that point, the expense for this "mediocre" production increase would be high. However, in the new process, a second fracture is quickly initiated to take advantage of the stress modification created from the first fracture, allowing the second fracture to reach more productive rock not accessible to the first fracture. This paper will present field data that supports the feasibility of this concept. Various situations where this approach could reap substantial benefits are also presented.
Parallelization on Unstructured Grids
Authors: Usadi Adam , Mishev Ilya , Shaw Jason , Wiegand Klaus
Published: December 2007

We describe experiences with parallelizing real models using an unstructured reservoir simulator on shared memory machines. Using ExxonMobil's proprietary reservoir simulator, EMpowerTM, which contains an object oriented data hierarchy which describes a fully unstructured mesh, a fully integrated well and surface facility network, and a highly flexible, user specified well management capability, we will show how parallelization is performed at a high level through several variants of data partitioning adapted to the specific algorithmic needs. Property calculations, Jacobian construction, matrix solution methods, and well management may use a variety of different data structures, partitioning, and parallel execution schemes. We discuss mechanisms for addressing problems encountered.
Staircase Lifting of Oil Using Venturi Principle: A New Artificial-Lift Technique
Authors: Gupta Siddhartha
Published: December 2007

Artificial lift systems are now being considered of extreme importance as the reserves across the globe are depleting and the wells are unable to flow naturally. Over the years a number of artificial lift techniques have evolved as a result of extensive research and ground work. All the systems have proven their worth by increasing the productivity of the field by many folds. But each of these artificial lift systems has economic and operating limitations that eliminate it from consideration under certain operating condition. However all the conventional artificial lift systems have a common feature. The energy added to the lift the fluid from the wellbore is lost in the process and cannot be utilized for some other operation. This paper describes a new technique of artificial lift which uses the concept of venturi to lift the fluid to the surface. A high velocity power fluid is used to create drawdown at the throat of a surface venturi and this pressure drawdown is transmitted downhole by pressure tappings. The drawdown lifts the fluid through the production tubular in a stepwise manner. The power fluid coming out from the other end of the venturi is used to drive a turbine which generates power as a result. This power is used to operate the inlet compressor thus the cycle being completed. After startup, effectively, no energy is used up to keep operating the system.

The system is of immense economic benefit as the operating expenditures are low. Also this system uses zero-cost air as power fluid. It is a space efficient package which can be used on offshore locations as well.

The paper describes the individual components of the system and the calculations involved therein. The economic and technical comparison of this system with the conventional methods is also enlisted.
The Importance of Hole Quality for Effective Image Log Interpretation Clearly Demonstrated in an Eight Well Program in Kuwait
Authors: Jumah Saud , Saleh Khaled , Al-Mayyan Haitham I. , Turner Mike
Published: December 2007

The objective of supplying real time LWD or FE information (Logging While Drilling and Formation Evaluation) should be to enable the client to make quick, accurate decisions on the formations being drilled, thus reducing and minimizing the geological uncertainty and maximizing or increasing the well bore exposure in the desired structure. During the course of drilling an 8 well Horizontal drilling program for the Kuwait Oil Company (K.O.C.) in the Burgan Field, Kuwait it became apparent that there was a need for clearer and better quality real time log information to enable the Drilling team to make quick decisions on were to place the well within the structure. This short paper will show the step change bought about in 3 of the wells drilled and the success and benefits realized by using long gauge PDC bits combined with a specialized short bearing pack motors, not only in the quality of the real time and recorded logs but in the over all bore hole quality as well.
Effects of Frictional Geological Discontinuities on Hydraulic Fracture Propagation
Authors: Zhang X. , Jeffrey R. G. , Thiercelin M.
Published: December 2007

This paper presents numerical results for a hydraulic fracture interacting with a frictional geological discontinuity in layered sedimentary rocks. A 2D hydraulic fracture model has been developed that can consider the details of the interaction and includes elastic rock deformation coupled to both fluid flow and frictional slippage. The interaction can result in fracture blunting, crossing or entering the interface, depending on modulus and stress contrasts, as well as the shear strength of the discontinuity. The numerical results are compared to experimental and field observations. When hydraulic fractures interact with long geological discontinuities, fracture growth can be stopped or retarded by the process. Treating pressure is increased by the large pressure gradients generated at offsets in the fracture path. Proppant transport can be impeded by such offsets because of the associated narrowing of fracture width. In some cases, the hydraulic fracture cannot easily enter frictional discontinuities when the interfaces have low frictional strength. In addition, pre-existing flaws are likely to serve as sites for re-initiation, allowing further hydraulic fracture growth into the intact side of the discontinuity. A higher closure stress acting in the intact rock favors arrest of the hydraulic fracture at the discontinuity, e.g., when a fracture attempts to cross a soft-to-stiff bedding plane. As a part of the interaction, the main hydraulic fracture will typically also lose fluid into cross-cutting frictional discontinuities.
Efficient and Robust Reservoir Model Updating Using Ensemble Kalman Filter With Sensitivity-Based Covariance Localization
Authors: Devegowda Deepak , Arroyo-Negrete Elkin , Datta-Gupta Akhil , Douma S. G.
Published: December 2007

Recently Ensemble Kalman Filtering (EnKF) has gained increasing attention for history matching and continuous reservoir model updating using data from permanent downhole sensors. It is a sequential Monte-Carlo approach that works with an ensemble of reservoir models. Specifically, the method utilizes cross-covariances between measurements and model parameters estimated from the ensemble. For practical field applications, the ensemble size needs to be kept small for computational efficiency. However, this leads to poor approximations of the cross-covariance matrix, resulting in loss of geologic realism. Specifically, the updated parameter field tends to become scattered with a loss of connectivities of extreme values such as high permeability channels and low permeability barriers, which are of special significance during reservoir characterization.

We propose a novel approach to overcome this limitation of the EnKF through a ‘covariance localization’ method that utilizes sensitivities that quantify the influence of model parameters on the observed data. These sensitivities are used in the EnKF to modify the cross-covariance matrix in order to reduce unwanted influences of distant observation points on model parameter updates. In particular, streamline-based analytic sensitivities are easy to compute, require very little extra computational effort and can be obtained using either a finite difference or streamline-based flow simulator.

We show that the effect of the covariance localization is to increase the effective ensemble size. But key to the success of the sensitivity-based covariance-localization is its close link to the underlying physics of flow compared to a simple distance-dependent covariance function as used in the past. This flow-relevant conditioning leads to an efficient and robust approach for history matching and continuous reservoir model updating, avoiding much of the problems in traditional EnKF associated with instabilities, parameter overshoots and loss of geologic continuity. We illustrate the power and utility of our approach using both synthetic and field applications.
Successful Breaker Optimization for Polyacrylamide Friction Reducers Used in Slickwater Fracturing
Authors: Carman P. S. , Cawiezel K. E.
Published: December 2007

To pump a high-rate fracture stimulation with fresh water or brines, a friction reducer must be employed. Most friction reducers used in slickwater fracture stimulation are high-molecular-weight polyacrylamide emulsions. Since these friction reducers are typically pumped at low concentrations (0.5 to 2 gpt), the industry belief has been that these polymers are causing minimal damage to the formation. There has also been a perception that the polyacrylamide polymer is difficult to degrade. However, fracture stimulations in areas such as the Barnett Shale use very large quantities of water with several stages per well which introduces large volumes of friction reducer into the formation. Because these large treatments are now widely used, several production companies have recently expressed concerns about the possible fracture and formation damage caused by these friction reducers. For this reason, a study was undertaken to find suitable breakers to effectively reduce the size (or molecular weight) of the polyacrylamide polymer chains and, therefore, reduce fracture and formation damage. Several conventional oxidizers were chosen and screened to determine if they could effectively reduce the viscosity of the polyacrylamide polymer. The molecular weight degradation of the polymer was then measured using a molecular weight cut-off (MWCO) filtration technique to determine the size and percentage of polymer fragments. Surprisingly, most of the breakers tested showed some reduction in viscosity and in molecular weight. Additional laboratory testing was then conducted to ensure that the addition of breaker to the friction reducer did not adversely affect polymer hydration or friction-reduction performance. This study reports on the results of the testing and shows which breakers were most effective in reducing the molecular weight of the polyacrylamide polymers used as slickwater friction reducers.
A New Approach to Automatic History Matching Using Kernel PCA
Authors: Sarma Pallav , Durlofsky Louis J. , Aziz Khalid , Chen Wen H.
Published: December 2007

Efficient history matching of geologically complex reservoirs is important in many applications, but it is central in closed-loop reservoir modeling, in which real-time model updating is required. Within the context of closed-loop reservoir modeling, the two approaches receiving the most attention to date are ensemble Kalman filtering and gradient-based methods using Karhunen-Loeve representations (eigen-decomposition) of the permeability field. Both of these procedures are technically appropriate only for random fields (e.g., permeability) characterized by two-point geostatistics (multi-Gaussian random fields). Realistic systems are much better described by multipoint geostatistics, which is capable of representing key geological structures such as channels. History matching algorithms that are able to reproduce realistic geology provide enhanced predictive capacity and are therefore more suitable for use with field optimization. In this work, we apply a new parameterization, referred to as a kernel principal component analysis (kernel PCA or KPCA) representation, to model permeability fields characterized by multipoint geostatistics. Kernel PCA enables preserving arbitrarily high order statistics of random fields, thereby providing the capability to reproduce complex geology. The KPCA representation is then combined with an efficient gradient-based history matching technique. The linkage of KPCA for modeling geology with gradient-based history matching is very natural as the KPCA representation is differentiable and gradients with respect to geological parameters can be readily computed. The overall procedure is then applied to several example cases, including synthetic models and a model of a real reservoir. The approach is shown to better reproduce complex geology, which leads to improved history matches and better predictions, while retaining reasonable computational requirements.
Understanding Formic Acid Decomposition as a Corrosion Inhibitor Intensifier in Strong Acid Environments
Authors: Cassidy Juanita M. , McNeil Robert I. , Kiser Chad E.
Published: December 2007

For many years formic acid has been used to intensify, or aid in, the performance of acid corrosion inhibitors in hydrochloric acid-based fluids used for stimulation procedures in the oilfield industry. Even so, the picture of how formic acid accomplishes this and under what conditions it functions is incomplete.

One theory for how formic acid aids in inhibition is that it undergoes a dehydration reaction to form water and carbon monoxide (CO), a known corrosion inhibitor.HCOOH→CO+H2O

This paper confirms that CO is produced by decomposition of formic acid in strong acids under downhole conditions. In addition, the conditions for the release of CO were found to be dependent on several variables, including temperature, acid strength, and alloy. Delineation of these conditions is important for effective implementation of formic acid as a corrosion inhibitor intensifier.
Simulating Gravity Drainage and Reinfiltration With a Subdomain-Dual-Permeability Hybrid Fracture Model
Authors: Rubin Barry
Published: December 2007

In this paper we describe how we have used finely gridded single porosity reference models to simulate the behavior of gravity drainage in fractured secondary gas caps/gas invaded zones with and without block to block reinfiltration.

These models were used as reference solutions in the development of the Subdomain-Dual Permeability Dual Continua model (SD-DK model). This extension of the classic Subdomain model 1 can simulate gravity drainage flow due to both direct matrix flow (capillary continuous) and matrix to matrix reinfiltration from fractures without the use of pseudo functions.

The behavior of the SD-DK model compares well with the fine grid single porosity reference models in situations where vertical oil drainage with capillary continuity between vertical matrix blocks is assumed or where vertical oil drainage is assumed to occur entirely due to reinfiltration.

In addition the model has been extended (heuristically) to allow it to model both drainage mechanisms occurring simultaneously (capillary continuous gravity drainage and reinfiltration).

The paper includes the details of the formulation as well as examples comparing the SD-DK technique to reference solutions and existing models.
Adaptive Multiscale Streamline Simulation and Inversion for High-Resolution Geomodels
Authors: Stenerud V. R. , Kippe V. , Datta-Gupta A. , Lie K. -A.
Published: December 2007

A particularly efficient flow solver can be obtained by combining a recent mixed multiscale finite-element method for computing pressure and velocity fields with a streamline method for computing fluid transport. This multiscale-streamline method has shown to be a promising approach for fast flow simulations on high-resolution geologic models with multimillion grid cells. The multiscale method solves the pressure equation on a coarse grid while preserving important fine-scale details. Fine-scale heterogeneity is accounted for through a set of generalized, heterogeneous basis functions that are computed numerically by solving local flow problems. When included in the coarse-grid equations, the basis functions ensure that the global equations are consistent with the local properties of the underlying differential operators. The multiscale method offers a substantial gain in computation speed, without significant loss of accuracy, when the multiscale basis functions are updated infrequently throughout a dynamics simulation.

In this paper we propose to combine the multiscale-streamline method with a recent ‘generalized travel-time inversion’ method to derive a fast and robust method for history matching high-resolution geologic models. A key point in the new method is the use of sensitivities that are calculated analytically along streamlines with little computational overhead. The sensitivities are used in the travel-time inversion formulation to give a robust quasilinear method that typically converges in a few iterations and generally avoids much of the subjective judgments and time-consuming trial-and-errors in manual history matching. Moreover, the sensitivities are used to control a procedure for adaptive updating of the basis functions only in areas with relatively large sensitivity to the production response. The sensitivity-based adaptive approach allows us to selectively update only a fraction of the total number of basis functions, which gives a substantial savings in computation time for the forward flow simulations.

We demonstrate the power and utility of our approach using a simple 2D model and a highly detailed 3D geomodel. The 3D simulation model consists of more than one million cells with 69 producing wells. Using our proposed approach, history matching over a period of 7 years is accomplished in less than forty minutes on an ordinary workstation PC.
A New Method of Calculating Water Invasion for Heavy-Oil Reservoir by Steam Injection
Authors: Dou Hongen , Chen Chuangchun , Chang Yuwen , Wang Xiaolin , Yu Jun , Wang Fenglan
Published: December 2007

Heavy oil production methods included the cyclic steam stimulation (CSS), steam flooding and steam assistant gravity drainage (SAGD). It is well known, when water invasion occurs in heavy oil reservoirs with edge/bottom water, for a long time, how much of the produced water comes from the steam injection process as oppose to edge/bottom water invasion? Reservoir engineers do not clearly understand the process, because after the steam condenses a part of the condensation comes to the surface and another part is stored within the reservoir itself. This is the problem that still gives reservoir engineers trouble. Through studying the production data of thermal recovery at the Liaohe oilfield, in China, for the first time, this paper reveals a new theory and calculation method that shows how to calculate water invasion from the bottom/edge water reservoir, therefore, a new concept of conversion rate was presented and a new parameter of steam-water ratio was defined, as k. new equations of calculating produced water invasion and water invasion of the remaining formation with bottom/edge water were derived according to the new parameter k. In addition, an estimation method of breakthrough time of bottom/edge is presented in this paper. The methods have been used to calculate and analyze the production performance of heavy oil with steam injection in Liaohe oilfield. The calculation results accord well with actual situation of heat-recovery reservoirs. Therefore, this method will be recommended to optimize production performance parameters of thermal recovery.
Parallel Unstructured Solver Methods for Complex Giant Reservoir Simulation
Authors: Fung Larry S. K. , Dogru Ali H.
Published: December 2007

The major issues for parallel solver in a modern reservoir simulator are robustness, scalability, efficiency, and flexibility. There is significant interest in running fast field-scale simulation for complex giant Middle-East reservoirs which will require tens to hundreds of millions of grid cells to give reasonable resolution. At the same time, significant geologic complexity will require the treatment of dual permeability regions, faulting and fractures, and high variations of reservoir and fluid properties. Of course, the methods should also work well for extracted sector simulation with local grid refinements in both the structured and unstructured discretization. The preconditioning methods considered in this work include both the single-stage and multistage frameworks. In the single-stage framework, a novel method in addition to the well-known variants of incomplete LU factorizations [ILU0, ILU(k), and ILUT] is considered. The new method is a highly parallel method which in this paper will be referred to as the unstructured line solve power series (LSPS) method. The method will be discussed and contrasted in light of key issues for parallel linear solvers. The unstructured LSPS has certain interesting properties in the parallel construct which makes it a highly effective component.

The multistage method researched in this work is of the constraint pressure residual (CPR) framework. The method uses approximate pressure solve as the first stage preconditioning to the full system preconditioning. A number of original adaptations based on this concept were researched. Here, the use of the parallel algebraic multigrid (AMG) method and other single-level methods mentioned above in combinations within the multistage CPR framework were explored. Certain methods constructed in this way are found to be highly efficient, scalable, and robust. The methods developed will be discussed and several test problems included in this paper.
A New Technical Standard Procedure to Measure stimulation and Gravelpack Fluid Leakoff under Static Conditions
Authors: Asadi M. , Penny G. S. , Ainley B. R. , Archacki D. J. , Bas van der F. , Bern P. A. , Brannon H. D. , Cobianco S. , Ghalambor A. , McElfresh P. M. , Milton-Tayler D. , Parker M. A. , Shah S.
Published: December 2007

A group of industry experts have compiled their years of experiences in developing a new technical standard to measure stimulation and gravel-pack fluid leakoff under static conditions. This method details step-by-step procedure for making fluids and measuring leakoff under static conditions. Stimulation and gravel-pack fluids are defined for the purpose of this technical standard as fluids used to enhance production from oil and gas wells by fracturing or acidizing and fluids used to place filtration media to control formation sand production from oil and gas wells, respectively. The procedure considers filter paper medium, natural core and synthetic core as the three filtering options. The paper also includes step-by-step example calculations of viscosity controlled leakoff coefficient and wall building coefficient.
How To Move From Excellent to Extraordinary Safety
Authors: Russell Larry
Published: December 2007

Excellent safety performance protects an organization's employees and assets. Extraordinary safety performance leverages excellent safety to create a high-functioning organization. Why is it that some companies can achieve the first level of performance but not be able to move toward the second? What does extraordinary safety performance really take and what can organizations do to get there? Finally, how does best-in-class safety correlate to high-performance in other areas?

Conventionally, the solution to accelerating safety performance has been to add to the existing infrastructure. Our experience of the past 20 years, however, has shown us that this approach can be counterproductive. Many large companies and corporations are already "swimming" in safety processes and systems. These organizations benefit not so much from adding assets but rather from learning how to strategically leverage the ones they already have.

Safety, because of its intrinsic value, is an ideal medium for improving overall organizational culture. Extraordinary safety performance is related to an organization's ability not just to maintain a healthy work environment and avoid serious events such as fatalities, but also to its ability to sustain performance at a world-class level across the board.

This talk examines the differences between excellent and extraordinary safety and presents ways that organizations can move toward best-in-class safety and organizational performance. This talk also covers the importance of creating extraordinary safety performance, its implications for organizations, and principles that make it possible.
The 200th Horizontal Openhole Gravel-Packing Operation in Campos Basin: A Milestone in the History of Petrobras Completion Practices in Ultradeep Waters
Authors: Marques L. C. C. , Paixão L. C. A. , Barbosa V. P. , Martins M. O. , Calderon A. , Pedroso C. A. , Fernandes L. H. C. , Melo J. A. , Chagas C. M. , Denadai N. J.
Published: December 2007

The paper presents an overview of the evolution of Petrobras open hole gravel packing operational practices after the 200th well has been successfully completed with this technique in Campos Basin (CB): a milestone in the history of Petrobras completion practices in deep and ultra-deepwaters.

The paper also presents a comprehensive description of the main steps taken to improve our horizontal open-hole gravel packing (HOHGP) practices towards a best-in-class status in unconsolidated oil-bearing turbidites. Since the first HOHGP job done in 1988 we had to move progressively from shallow to ultra-deepwater completion scenarios. Along this path a series of innovations has been incorporated to our sand face completion practices due to the ever-growing-complexity of the wells geometry, longer intervals to be completed, heavier oil reserves to be developed, rock mechanics restraints (ever-lowering fracture gradients) and the necessity of damage-free-, high-performance-wells to cope with the skyrocketing capital expenditures which is a general rule for offshore ultra-deepwaters nowadays.

Petrobras strategy conceived to continuously enhance its HOHGP completion efficiency index encompasses, the following interrelated subjects: -a comprehensive long-term plan to deal with the problem, -a multi-disciplinary team-work approach, -a strong cooperation with gravel packing tools & screens suppliers, -improvement of operational procedures and guidelines against which to measure well performance and -research & investment in cutting-edge technologies.

Discussions on the challenges envisioned for HOHGP operations in ultra-deepwaters in the years to come are also presented.
Application of Pressure-Transient and Production-Data Analysis for Hydraulic-Fracture-Treatment Evaluation
Authors: Economides Michael J. , Ehlig-Economides Christine A. , Tosic Slavko
Published: December 2007

The Unified Fracture Design (UFD) concept provides a mechanism to determine the optimal hydraulic fracture design for a given amount of a selected proppant, while modern hydraulic fracture treatment execution offers the potential to achieve the optimal design. The proppant number is a ratio of the proppant permeability and proppant volume product to the formation permeability and reservoir volume product. The cost of the hydraulic fracture treatment is directly related to the quality and quantity of proppant injected and successful achievement of the optimal fracture treatment easily offsets this cost when appropriate economics and physical and logistical constraints are considered in the job design. Pressure transient and production data analyses are described in terms of fracture length and conductivity and do not address parameters important to the UFD evaluation. A previous paper described the use of post-treatment analysis to evaluate the effectiveness of the treatment in terms of dimensionless productivity index, dimensionless fracture conductivity, and the proppant number.

With more and more permanent gauge installations, opportunities for pressure buildup analysis may occur under normal operating conditions without a specific test design. In this case both pressure transient and production data analysis may be available. The analysis addresses both single-phase oil and gas primary production and oil production under pressure maintenance or waterflood. Also, non-ideal fractures with height growth beyond the producing formation thickness and fracture skin are considered. Field examples will include both hard rock and soft rock fracturing case studies.

The importance of this analysis is paramount for operators trying to optimize high value hydraulic fracture treatments.
Estimating Fracture Reorientation Due to Fluid Injection/Production
Authors: Zhai Zongyu , Sharma Mukul M.
Published: December 2007

The injection or production of large volumes of fluid into or from a reservoir can result in significant changes to the effective in-situ stress distributions. Field evidence of this has been provided in the past by mapping refracturing treatments in tight gas sands and micro-seismic monitoring of injection wells in water-flooded reservoirs.

A poro-elastic model is presented to show how the extent of fracture reorientation can be estimated under different conditions of fluid injection and production. The extent of fracture reorientation is a function of the in-situ stresses, the mechanical properties of the rock and the pore pressure gradients. In reservoirs where the pore pressure gradients are complicated due to multiple injection and production wells, fracture reorientation is sensitive to the net pore-pressure gradients. Fractures tend to reorient themselves towards the injection wells and away from production wells, if the pressure gradients are comparable to the in-situ stress contrast.

While far-field principal stress orientations are impacted only by in-situ stresses and pore-pressure gradients, near-wellbore in-situ stress orientation is also impacted by the hoop stress and the wellbore pressure. These can have a significant effect on near-wellbore fracture reorientation. The results of our model are compared with field observations obtained from micro-seismic monitoring of water injection wells. The implications of the results to refracturing operations and candidate well selection are discussed.