bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Mechanical Constitutive Model on the Coupled Hydro– Geomechanical Analysis of Fault Reactivation
Authors: Guimarães L. J. N. , Gomes I. F. , Valadares J. P. V.
Published: February 2009

Injection and production of fluids cause changes of pressure, temperature and saturation that affect the state of stress in oil reservoirs, resulting in porosity and permeability variations. It is therefore a coupled hydro-geomechanical problem. The fault reactivation problem considers that shear (with dilatancy), tension or compression of filling material may cause changes in hydraulic properties. Reservoir simulation with geomechanical coupling allows realistic modeling of fault reactivation, that can influence in the production of oil due to pressure and fluid loss in the reservoir. A finite element procedure is presented that models fluid flow in a deformable reservoir crossed by a geological fault in a coupled and totally implicit manner. Whether the fault is activated or not is governed by the hydro-mechanical boundary conditions of the problem and by the modeling of the constitutive behavior of involved materials. Two alternative mechanical constitutive models were adopted to represent the behavior of the filling material of the fault: elastoplastic Mohr-Coulomb (dilatancy considered) and continuum isotropic damage model (micro-cracking considered), that lead to different responses of the reservoir-fault system. It was observed that when the continuum damage model is used reactivation chiefly tends to occur inside reservoir. On the other hand, when the Mohr-Coulomb model is used activation propagates through reservoir and adjacent rocks. Simulation of constitutive behavior of sealing faults is essential to the prediction of the possibility of reactivation especially during waterflooding with reservoir pressurization, which may cause economic as well as environmental damages. In oil reservoirs with fault reactivation possibility, definition of maximum bottom hole pressure of the injectors during waterflooding can only be safely conducted based on a coupled hydro-geomechanical analysis tool with realist modeling of the constitutive behavior of the materials.
A General Unstructured Grid, Parallel, Thermal Simulator and its Application for Large Scale Thermal Models
Authors: Shi Xundan , Chang Yih-Bor , Muller Mathieu , Obi Eguono , Lim Kok-Thye
Published: February 2009

We describe the contruction of a general unstructured grid, parallel, fully-implicit simulator for complex physics associated with heavy oil thermal recovery. The primary focus of the simulator is on the physics associated with steam injection and Steam Assisted Gravity Drainage (SAGD) and to simulate such models efficiently using parallel processing. The simulator solves component material balance, energy balance and mass equilibrium equations for component mole fractions, saturation, temperature and pressure using the Newton-Raphson method. External heat sources and sinks are included in source terms to model the energy interaction with over-burden and under-burden rocks. The solution procedure and the treatment of phase transition to achieve stable non-linear iterations are discussed.

The simulator is verified by comparing results from problem No. 3 of the Fourth SPE Comparative Solution Projects and a cyclic steam injection case with other commercial simulators. We also demonstrate the performance and parallel scalability of the simulator via testing a large scale SAGD model with 9 horizontal well-pairs.
Scalable Multi–stage Linear Solver for Coupled Systems of Multi–segment Wells and Complex Reservoir Models
Authors: Jiang Y. , Tchelepi H. A.
Published: February 2009

Wellbore flow and interactions between wells and the reservoir can be complex. Accurate modeling of these behaviors is especially important for advanced (multi-lateral) wells. This paper describes a new scalable linear solver for flow simulation of detailed unstructured models with coupled multi-lateral multi-segment wells. The linear solver accommodates systems associated with both the fully implicit approach and the adaptive implicit method (AIM).

A general-purpose research simulator (GPRS) serves as the computational platform, in which reservoir flow is described with a thermal-compositional AIM formulation, and a multi-segmented well (MsWell) model is used to describe wellbore flow. In the MsWell model, the wellbore is discretized into segments; pressure, velocity, and phase fractions are computed for each segment. Multi-lateral multi-segment wells add a large number of equations and unknowns, which are coupled to the reservoir model.

The new linear solver is a generalized two-stage constraint pressure residual (CPR) preconditioner. The first stage is a global pressure system of equations, where the pressure coupling between the reservoir and the complex wells is represented accurately. This coupled pressure system is obtained algebraically, where the multi-segment wells are reduced to a form similar to that of standard wells. The two-stage scheme serves as the inner loop of a generalized minimum residual (GMRES) iterative solver. Algebraic multigrid (AMG) is used to compute the first-stage pressure solution; a special block-based incomplete lower-upper (ILU) preconditioner with arbitrary levels of fill-in is used for the second stage. This multi-stage solution algorithm was implemented using multi-level, sparse, block-based (MLSB) data structures specially designed for AIM computations on unstructured grids. We demonstrate the superior performance of this new solver compared with state-of-the-art methods using a variety of compositional problems for highly detailed reservoir models with unstructured grids and complex multi-segment wells.
Multiscale Finite Volume Formulation for the Saturation Equations
Authors: Zhou H. , Lee S. H. , Tchelepi H. A.
Published: February 2009

Recent advances in multiscale methods have shown great promise in modeling multiphase flow in highly detailed heterogeneous domains. Existing multiscale methods, however, solve for the flow field (pressure and total-velocity) only. Once the fine-scale flow field is reconstructed, the saturation equations are solved on the fine scale. With the efficiency in dealing with the flow equations greatly improved by multiscale formulations, solving the saturation equations on the fine scale becomes the relatively more expensive part. In this paper, we describe an adaptive multiscale finite-volume (MSFV) formulation for the nonlinear transport (saturation) equations. A general algebraic multiscale formulation consistent with the operator based framework proposed by Zhou and Tchelepi (SPEJ 13:267-173) is presented. Thus, the flow and transport equations are solved in a unified multiscale framework. Two types of multiscale operators, namely restriction and prolongation, are used to construct the multiscale saturation solution. The restriction operator is defined according to the local sum of the fine-scale transport equations in a coarse gridblock. Three adaptive prolongation operators are defined according to the local saturation history at a particular coarse block. The three operators have different computational complexity, and they are used adaptively in the course of a simulation run. When properly used, they yield excellent computational efficiency while preserving accuracy. This adaptive multiscale formulation has been tested using several challenging problems with strong heterogeneity, large buoyancy effects, and changes in the well operating conditions (e.g., switching injectors and producers during simulation). The results demonstrate that adaptive multiscale transport calculations are in excellent agreement with fine-scale reference solutions, but with a much lower computational cost.
Quasi-Positive Multi-Family Continuous Darcy-Flux Approximations With Full Pressure Support on Structured and Unstructured Grids in 3-D
Authors: Zheng Hongwen , Edwards Michael G.
Published: February 2009

New mutli-families of flux-continuous finite-volume methods are presented for the full-tensor pressure equation with general discontinuous coefficients for any cell type in three dimensions. Full pressure continuity that is built into the new methods leads to a quasi-positive formulation that minimises spurious oscillations in discrete pressure solutions for strongly anisotropic full-tensor fields. The multi-family formulation permits maximum flexibility in quadrature yielding improved solution resolution.
Advantages of Using Vertical Stair Step Faults in Reservoir Grids for Flow Simulation
Authors: Gringarten E. , Haouesse A. , Arpat B. , Nghiem L.
Published: February 2009

Conventional reservoir modeling relies on the construction of 3D grids which conform to stratigraphy and whose columns are aligned with faults.

When modeling non-vertical faults, traditional "pillar technology" yields large volume distortions between cells leading to non-orthogonality problems. It is difficult or impossible to construct conventional grids in structurally complex environments: reverse, dying faults, X-, Y-, λ-faults. Modelers can spend days simplifying their model by removing or verticalizing faults. Deciding on which data to alter is cumbersome and results in inaccurate models. This affects connectivity and compartmentalization, impacting significantly reservoir management decisions.

Therefore, it is essential to construct grids that honor the integrity of the complete reservoir structure regardless of its complexity, and yet that are compatible with commercial flow simulators.

A solution, in terms of structured grids, is to consider vertical stair-step faults. They have many advantages: all types of faulting patterns can be accurately represented; columns can be (sub-) vertical; cells are less likely to be distorted and orthogonality can be ensured. These grids are ideal for reservoir flow simulation purposes. However, since it has been difficult to construct them in the past, few engineers have experience with them.

In this paper, a methodology to construct such grids that preserve the integrity of the structure and stratigraphy of reservoirs is presented. Approaches to robust reservoir property modeling and upscaling are also discussed. Test cases are presented, comparing results from conventional pillar grids with grids in which faults are defined as vertical stair-steps. The integration of this type of grid with a high-performance reservoir simulator is also highlighted.
Multi-D Upwinding for Multi Phase Transport in Porous Media
Authors: Kozdon J. , Mallison B. , Gerritsen M. , Chen W.
Published: February 2009

Multidimensional transport for reservoir simulation is typically solved by applying 1D numerical methods in each spatial coordinate direction. This approach is simple, but the disadvantage is that numerical errors become highly correlated with the underlying computational grid. In many real-field applications this can result in strong sensitivity to grid design for the computed saturation/composition fields, but also for critical integrated data such as breakthrough times. To increase robustness of simulators, especially for adverse mobility ratio flows that arise in gas injection and other EOR processes, it is therefore of much interest to design truly multi-D schemes for transport that remove, or at least strongly reduce, the sensitivity to grid design.

We present a new upwind biased truly multi-D family of schemes for multi-phase transport capable of handling counter-current flow arising from gravity. The proposed family of schemes has four attractive properties: applicability within a variety of simulation formulations with varying levels of implicitness; extensibility to general grid topologies; compatibility with any finite volume flow discretization; and provable stability (monotonicity) for multi-phase transport. The family is sufficiently expressive to include several previously developed multi-D schemes, such as the narrow scheme, in a manner appropriate for general purpose reservoir simulation.

A number of water flooding problems in homogeneous and heterogeneous media demonstrate the robustness of the method as well as reduced transverse (cross-wind) diffusion and grid orientation effects.
A Next-Generation Parallel Reservoir Simulator for Giant Reservoirs
Authors: Dogru Ali H. , Fung Larry S. K. , Middya Usuf , Al-Shaalan Tareq M. , Pita Jorge A. , HemanthKumar K. , Su H. J. , James C. T. Tan , Hoy H. , Dreiman W. T. , Hahn W. A. , Al-Harbi R. , Al-Youbi A. , Al-Zamel N. M. , Mezghani M. , Al-Mani T.
Published: February 2009

Giant reservoirs of the Middle East are crucial for the supply of oil and gas to the world market. Proper simulation of these giant reservoirs with long history and large amount of static and dynamic data requires efficient parallel simulation technologies, powerful visualization and data processing capabilities.

This paper describes GigaPOWERS, a new parallel reservoir simulator capable of simulating hundreds of millions of cells to a billion cells with long production history in practical times. The new simulator uses unstructured grids. A distributed unstructured grid infrastructure has been developed for models using unstructured or complex structured grids. Unconventional wells such as maximum reservoir contact wells and fish-bone wells, as well as faults and fractures are handled by the new gridding system. A new parallel linear solver has been developed to solve the resulting linear system of equations. Load balancing issues are also discussed.

A unified compositional formulation has been implemented. The simulator is designed to handle n-porosity systems. An optimization-based well management system has been developed by using mixed integer nonlinear programming. In addition to the core computational algorithms, the paper will present the pre- and post-processing software system to handle large amount of data. Visualization techniques for billions of cells are also presented.
Successful Application of MPD Technique in a HP/HT Well Focused on Performance Drilling in Southern Mexico Deep Fractured Carbonates Reservoirs
Authors: Tellez C. P. , Duno H. , Casanova O. , Colombine W. , Lupo C. , Palacios J. R. , Medina L.
Published: February 2009

The development field Tizon, is located west of Frontera, NE of the Palapa and Luna Fields, Municipality of Centla, in the Coastal Plain of the Southern Gulf of Mexico in Tabasco State. Historic crude oil exploitation targets the Cretaceous and Jurassic formations (5600 to 6300 m TVD). Formation pressure in these naturally fractured carbonates is close to 12000 psi and temperatures ranging between 160 and 180 °C. Managed Pressure Drilling (MPD) techniques were implemented to avoid formation influx and increase the safety of operations (H2S-bearing reservoir) and also, to avoid lost circulation, formation damage and differential sticking due to conventional drilling procedures requiring a highly overbalanced mud weight. The significant risk to drill with conventional techniques was critical enough to consider a full MPD application. This paper describes the experience gained in the planning and execution of the drilling operation of this well; using backpressure at the wellhead and the implementation of a conventional MPD package to improve performance of the operation targeting reducing the Non-Productive-Time. The paper will guide the technical, community over the design, planning and execution process, geological review, pre-engineering study, steady state flow modeling, final drilling program, training, safety and contingencies.
A New Chapter in MPD: Subsea Pumping
Authors: Hinton Andy
Published: February 2009

Subsea pumping systems improve the safety and efficiency of drilling operations in tophole in water depths down to 525m (1720ft). The system collects mud at the seabed and pumps it back to the rig before the rig BOP / riser has been run.

This equipment can be reconfigured to a ‘pumped riser’ mode for use after the riser is run. Drilling mud is pumped from an outlet in the marine riser with a blanket fluid, usually seawater above. Varying the level of heavy mud in the riser compensates for the Annular Pressure Loss. By dropping the level as mud circulation starts, there in no increase in the Bottom Hole Pressure (BHP). The Equivalent Circulating Density (ECD) is the same as the mud weight. There is a constant BHP when drilling, circulating, making connections, tripping, logging etc.

The system is simple to understand and doers not rely on surface pressure or pressurising the marine riser. Connections are likely to be slower than the alternative methods but this is not considered a significant problem. In some ways is reassuring to be able to change conditions slowly and steadily.

Pumped riser systems may also be used to drill surface holes, without any gas, at bottom hole pressures below seawater hydrostatic. This may be done to avoid losses into vugular formations or to improve drill rates in hard formations.

Subsea pumping has also been used in a deepwater 5000ft (1500m) field trial. This proved up deepwater RMR but is a step towards the goal of full Dual Gradient Drilling in deep water.
Pressurized Mud Cap Drilling in Qatar's North Field
Authors: Niznik Michael R. , Elks William C. , Zeilinger Sabine C.
Published: February 2009

This paper discusses the operator's use of pressurized mud cap drilling (PMCD), a form of Managed Pressure Drilling (MPD) technology, to successfully capture reserves in Qatar's North Field that were not accessible with conventional drilling operations. While drilling off one of the platforms, the operator encountered faulting, vugular porosity, and Karst features in one particular carbonate sequence that led to the total loss of returns, which could not be controlled with lost circulation material or cement squeeze operations. After reviewing the drilling alternatives, the operator determined that PMCD was an enabling technology to drill through the problematic lost circulation interval in the 12¼-in. hole section above the reservoir. Risk assessments confirmed that PMCD could be conducted both safely and effectively utilizing a rotating head (RH) rigged up on top of the existing well control package.

The North Field platforms are located in the offshore Arabian Gulf and provide unlimited access to seawater. PMCD requires injection of potentially large volumes of fluid down the drillpipe and by the casing / hole annulus. Since seawater was abundant, it was the consensus fluid of choice. A review of the formations drilled in the 12¼-in. hole section confirmed clays were not present and that borehole instability would not be a concern.

In addition to reducing operational complexity and trouble time, the use of PMCD in this case was also driven by the operator's drilling performance management process which dictates that performance limiters be identified and extended following a specific process. Consequently, this application of PMCD was structured to maximize footage per day rather than only address the lost returns costs. The paper discusses both the lost returns management and the associated efforts to maximize performance gains.

The paper will address PMCD well control and injection equipment requirements as well as the drilling and liner running operations on the first well. The area geology and the field's history with lost returns will also be discussed.
Real-Time Monitoring of Downhole ECDs for Parasite Aeration Using a Simple Spreadsheet Calculation
Authors: Scott Paul D.
Published: February 2009

Monitoring the real-time down hole equivalent circulating densities (ECD) of parasite aeration can be done quite easily and accurately with a simple spreadsheet calculation. The method is described and field examples are presented comparing the results of this using procedure with pressure while drilling (PWD) data. Situations where using this method may not be accurate will also be discussed.

Parasite aeration involves running a small diameter string of tubing down the outside of the casing string and injecting air to aerate the mud column in the casing to drill pipe annulus to reduce bottom hole pressure. Parasitic aeration is a highly effective method for underbalanced drilling operations which has many advantages over down the drill pipe aeration. These include a lower air injection pressure, independent control of the mud and air injection rates, aeration can continue during connections, different dual gradient pressure profile more like the pore pressure profile for high altitude locations, lower pressure surges after trips or connections, and the unique ability to monitor in real-time the down hole pressure with a simple spreadsheet calculation.
Hydraulic Optimization of Aerated Mud Drilling for Maximum Drilling Rate
Authors: Andersen H. , Vigrestad A. , Kuru E.
Published: February 2009

The theory of hydraulic optimization of drilling with conventional (incompressible) drilling fluids is well known and has been widely practiced in the industry. Classical theory of hydraulic optimization for maximum drilling rate calls for either the use of empirical correlations, such as Fullerton charts, Amoco curves, etc., or the use of optimization theory to maximize some arbitrary objective functions, such as maximum bit hydraulic horsepower or jet impact force.

The concept of hydraulic optimization for maximum drilling rate when drilling with aerated mud is not well investigated. Compressible nature of the aerated mud makes the use of conventional optimization theory difficult. The main objectives of hydraulic design when drilling with compressible fluids are to secure underbalanced drilling and ensure efficient cuttings transport. It is generally assumed that drilling with low head compressible fluids increase the drilling rate.

This paper presents a new technique to evaluate the impact of aerated mud hydraulic design on the drilling rate. In this study, classical theory of hydraulic optimization (i.e., maximum bit hydraulic horsepower/ jet impact force criteria) has been re-visited for possible modification and application in hydraulic optimization of aerated mud drilling. As for incompressible fluids, it was found that the parasitic pressure losses for aerated drilling fluids can be treated as a power law function of the total (gas + liquid) fluid flow rate. A new methodology has been suggested to determine optimum gas/liquid injection rates for maximizing drilling rate when drilling with aerated mud.

The new method can easily be used in the field to determine best combination of gas/liquid injection rates and total bit flow area (i.e., jet nozzle sizes) such that maximum drilling rate is achieved.
Key Parameters in Foam Drilling Operations
Authors: Paknejad Amir , Schubert Jerome , Amani Mahmood
Published: February 2009

Although the use of compressible drilling fluids is experiencing growth, the flow behavior and stability properties of drilling foams are more complicated than those of conventional fluids. In contrast with conventional mud, the physical and rheological properties of foam change along the wellbore. The complex flow mechanisms involved in compressible drilling fluid circulation make determination of the optimum combination of controllable drilling parameters very difficult. The accurate determination of the foam properties in circulating wells helps to achieve better estimation of foam rheology and pressure profile in the annulus.

There are some key drilling parameters which would affect the circulating bottomhole pressure. Some of these parameters are controllable at the surface and some are not. The question is how to combine different controllable and uncontrollable parameters in order to obtain optimum cuttings transport performance, pressure distribution, and bit hydraulics.

Using a Finite Difference Method (FDM), a mathematical model and a numerical analysis of the foam hydraulics have been presented earlier. The model has been incorporated into a computer code and has used for processing the data and closely simulate the pressure change along the wellbore during drilling a well.

In this study, based on the developed simulator, a comprehensive sensitivity analysis is performed to determine the effects of important controllable and uncontrollable parameters such as: back-pressure, rate of penetration, gas/liquid injection rates, cuttings concentration, cuttings size, and formation water influx.

Optimum selection of Gas Liquid Ratio (GLR), gas/liquid injection rates, back pressure, and drilling rate is the key issue in hydraulic design in order to achieve the desired circulating pressure. A proper hydraulic design will aid the industry in identifying practices that lead to drill wells more economically and efficiently.
Successful Application of Automated Choke MPD System to Prevent Salt Water Kicks While Drilling in a High-Pressure Tertiary Salt Diapir with OBM in Southern Mexico
Authors: Hernandez J. , Tellez C. Perez , Lupo C. , Scarcelli D. , Salinas N. , Bedino H. , Gallo F. , SehSah O.
Published: February 2009

The field subject of this paper is located in the southern Mexico, 34 km North of Villahermosa, Tabasco. Oil exploitation targets the Cretaceous and Jurassic formations (4500 mts a 5200 mts TVD). The 12 ¼" section of these wells must be drilled through a high pressure tertiary salt diapir which historically has been a high NPT generator due to high pressure salt water kicks and OBM contamination. Drilling strategy is usually oriented to the use of high density inverse emulsion mud with densities normally ranging between 1.95 to 2.27 SG (16.2 to 18.9 ppg). High density mud causes losses in the interfaces above and below the salt diapir and in some cases losses while drilling the salt diapir due to sand intercalations. A close analysis of the offset wells identified the MPD as a possible solution to mitigate the risks confronted in the section. This document describes the first application of the automated choke MPD system in Mexico, in a Sen well, and how the use of automated choke MPD system allowed drilling the section with no major operational events such as influxes, losses, stuck pipe or salt water contamination of OBM. The system helped detecting micro influxes giving tangible added value to this challenging narrow mud window hole section. As a result 938 meters of salt were drilled in only 11 days while field average is around 30 days.
Predicting the Production Capacity During Underbalanced-Drilling Operations in Vietnam
Authors: Nguyen C. , Somerville J. M. , Smart B. G. D.
Published: February 2009

During recent years, interest in underbalanced drilling (UBD) has grown rapidly. As a drilling technique it has gained acceptance because it provides a method of minimizing formation damage, preventing lost circulation risks and increasing penetration rates. One of the most important tasks in UBD design is to estimate how much oil can be produced during the drilling operation. This task is very difficult because of the complex nature of the multiphase flow in the UBD system, especially in the annulus between the drillpipe, collars and the wellbore where water, gas, cuttings and fluid influx from the penetrated formations are present. To accomplish this task, the bottomhole pressure must be calculated. However, the bottomhole pressure, fluid influx flow rates, and fluid properties along the wellbore are interdependent parameters and can only be derived through a combination of iterative and finite differential methods. It is therefore necessary to use a computer program to carry out the work.

This paper presents a method to predict production capacity by coupling drilling parameters and inflow performance parameters such as surface choke pressure, gas injection rates, liquid flow rates and fluid production rates for UBD. A software tool named UBDRILL has been developed which can be used to perform thorough investigations of UBD hydraulic calculations and the estimation of production capacity.

The proposed method and developed software are validated by application examples of UBD in granite basement reservoirs in Vietnam, SE Asia.
Microflux Control and E-CD Continuous Circulation Valves Allow Operator to Reach HPHT Reservoirs for the First Time
Authors: Calderoni Angelo , Girola Giorgio , Maestrami Michele , Santos Helio , Holt Calvin
Published: February 2009

Wells in challenging environments are known for their high cost with targets not reached, and often abandoned. HPHT wells fall in this category and in Lower Mediterranean Sea this was not an exception. After a few wells drilled in an offshore HPHT area, with advanced techniques and alternatives being tried on well after well, Eni through its foreign affiliate decided to use a combination of Eni's continuous circulation (CC) valves, (Eni Circulation Device – E-CD) and the Micro-Flux Control (MFC) method. Eni calls the combination of CC with the precise measurement and control of the flow and pressure from the well, within a closed loop through a rotating control device (RCD), as: Eni-Near-Balanced Drilling (ENBD). With this new drilling method, a well in the HPHT area reached all the targets for the first time.

Wells in this area face the usual kick-loss scenario, with significant non productive time (NPT) and adding hundreds of days to drill a well. The goal for using the E-CD was to avoid pressure and temperature fluctuation while drilling, by maintaining the annulus as stable as possible, and the MFC would provide a clear picture and manage the bottomhole pressure (BHP) within the downhole pressure limits, pore and fracture. Previous attempts to improve drilling were made using just RCD, then a continuous circulation system and later on the E-CD valves were used together with the RCD on other wells, but, even though improvements were seen, those were not enough to ensure reaching the final targets. It was only when the MFC method was added that success was achieved.

The paper describes the operations and results obtained by the ENBD system and its benefits in terms of NPT and kick quantity and size reduction. Comparison with the previous wells where the targets could not be reached clearly shows the significant advantage of using the system, compared to conventional drilling. Reduction in risk and increased control over the entire drilling process, in an environment with extremely narrow margins, were paramount to a successful outcome.
Coiled Tubing MPD for Tight Gas Field Re-Entry Work
Authors: Dietrich Earl , Denton Stewart , Cadena Javier , Ortiz Richard , Ohanian Mike
Published: February 2009

As fields mature and recovery factors reach technical limits, companies continue to search for ways to increase field longevity. The use of coiled tubing drilling (CTD) techniques in Alaska, USA1, Sharjah, UAE2, 3, 4, and other locations proves to be a promising access technology for re-entering old wellbores. BP America identified the Cleveland formation as a viable candidate on which to apply new technologies including CTD.
Choice of Hydraulics Flow Model: A Step towards a Successful High-Pressure MPD Operation in Offshore India
Authors: Mujeer Shaikh Abdul , Boyce Graham Robert , Davis Paul
Published: February 2009

Hydraulic modeling is an integral part of any MPD operation. Engineers rely on hydraulic flow modeling throughout an MPD project; i.e., during the candidate selection for the MPD well, the initial design, and, during the MPD operation. Hence, choosing the correct hydraulics model is critical to the success of an MPD project.

This paper proposes that the correct hydraulics model for a particular well depends on the nature of the reservoir and bottomhole conditions. Although, the data for simulation often comes from offset wells and may not be representative of the target well. Additionally the same hydraulics model may not work for different well conditions; e.g., a model that works for a two-phase drilling fluid may not work successfully for a high-density oil-based mud (OBM). Hence, an engineer should run flow models using different simulators and conclude the best possible model for the specific conditions.

The paper discusses two hydraulic models that were used in offshore India. Calibration of these models was done using data from offset wells. It was found that the models predicted different results with the same inputs. While one gave more realistic results on comparison with the post drilling reports on the offset wells, the other model did not match the results. On further analysis, it was found that the reason for failure of the second model was its inaccuracy in simulating high-density OBM; also, each software handled cuttings transport, geometry, and rheological behaviour differently. The paper compares these differences and discusses the type and range of applications for which each is most applicable.

The results conclude that a hydraulic model is case sensitive. An in-depth analysis of both models, the reasons for failure and success of each, and how using the correct hydraulics model can significantly influence the MPD operation will be presented.
Application of UBD Technology to Maximize Recovery from Horizontal Wells in Naturally Fractured Carbonate Reservoirs
Authors: Salimi Siroos , Naziri Alireza , Ghalambor Ali , Tronvoll Johan
Published: February 2009

This paper describes the results of an investigation of productivity and recovery improvement in naturally fractured reservoirs when using underbalanced drilling (UBD) technology in horizontal wells. A numerical simulator is used to simulate the results in terms of local changes in permeability and saturation of overbalanced and underbalanced wellbore conditions during the drilling operation. A single horizontal well model has been established to predict production rates for both UBD and OBD cases. The naturally fractured reservoir is simulated with a dual porosity, dual permeability model. Fine grids are used to capture dynamic effects of pressure and saturation in the near-wellbore region. To model the formation damage in the near wellbore region, an integrated approach is introduced that combines dynamic reservoir simulation and local formation damage based on dynamic core flood test data. The test results are interpreted to obtain an estimate of filter cake effect on filtration loss and impact of solid invasion on return permeability. The formation damage model is then used to generate a profile of saturation and pressure as initial conditions in the numerical simulator to model the production. The study is summarized as follows

UBD case with influx during drilling OBD case with continuous filtration from the wellbore to the formation UBD case with short time of overbalance condition.

The study results provide a set of criteria, which can be used as a reference and guidelines to consider UBD technology for horizontal well in naturally fractured reservoirs.
Managed-Pressure Drilling: What It Is and What It Is Not
Authors: Malloy Kenneth P. , Stone C. Rick , Medley George H. , Hannegan Don , Coker Oliver , Reitsma Don , Santos Helio , Kinder Joseph , Eck-Olsen Johan , McCaskill John , May James , Smith Kenneth , Sonneman Paul
Published: February 2009

Within the context of broad industry recognition of two drilling technologies, Underbalanced Drilling predates Managed Pressure Drilling (MPD) by at least a decade. While there are some similarities in some of the equipment and possibly in some of the techniques, the applications are different in their intent. This paper will discuss methodologies comparing Conventional, Underbalanced, and Managed Pressure Drilling Operations with respect to objectives, planning, drilling equipment and operations, and well control. The application of Managed Pressure Drilling was specifically created to give it an identity apart from Conventional Drilling and apart from Underbalanced Drilling. There appears to be some confusion with respect to methodology for Managed Pressure Drilling. What constitutes a Managed Pressure Drilling Operation? What constitutes an Underbalanced Drilling Operation? Are they actually the same? Does it matter?

Figure 1 illustrates the general domains of Conventional Drilling Operations, Managed Pressure Drilling Operations, and Underbalanced Drilling Operations.
Closing the Loop Between Reservoir Modeling and Well Placement and Positioning
Authors: Liu N. , Jalali Y.
Published: February 2009

We present a methodology of converting standard reservoir models to maps of production potential for screening regions that are most favorable for well placement. A technique is developed to apply this method to the problem of field development where field production profile moves through successive phases of buildup, plateau, and decline. This results from successive drilling and commissioning of wells at a prescribed frequency (e.g., quarterly) until the total well ‘budget’ for the field is exhausted and eventual termination of wells as they reach prescribed abandonment criteria. This method, in general, results in an irregular well placement pattern, as it attempts to conform to both time-invariant reservoir properties (e.g., permeability field which may be nonuniform) and time-varying properties (e.g., pressure and saturation field). As such it is a well placement strategy governed purely by reservoir drainage objectives rather than infrastructure considerations which may favor a more regular and orderly well spacing pattern.

We illustrate this methodology for the case of a strong water-drive reservoir to be developed by horizontal wells under primary production. Specifically we examine how the field production profile and recovery factor is affected as the irregular well placement approach, driven by drainage objectives, is applied, compared to a fixed spacing approach. For both cases, an identical field footprint is simulated, that is, the same number of wells, type of wells, production programs, and abandonment criteria are applied; also both follow the ‘floor to ceilling’ well placement strategy in the reservoir which field experience suggests is advisable for bottom water-drive reservoirs.

We observe a marked improvement in field recovery factor, as manifested by a higher and/or longer plateau, for the case of irregular well placement. The gain reveals the large impact that may result from the systematic use of automatic history-matching techniques and advanced drilling and measurement technologies, the two pillars for the implementation of the method described in this study.

This method also suggests that the same parametric group used to convert standard reservoir models to maps of production potential, can be used to convert while-drilling measurements to the expected production potential of the well as the well is being drilled. This method has been described in a separate study, but that study was limited to the problem of placing a well in a dedicated drainage area. The current study describes the methodology of sequential well placement across the entire reservoir, therefore complements and completes this prior work.
Genetic Disorders of Surfactant Dysfunction
Authors: Wert Susan E. , Whitsett Jeffrey A. , Nogee Lawrence M.
Published: February 2009

Mutations in the genes encoding the surfactant proteins B and C (SP-B and SP-C) and the phospholipid transporter, ABCA3, are associated with respiratory distress and interstitial lung disease in the pediatric population. Expression of these proteins is regulated developmentally, increasing with gestational age, and is critical for pulmonary surfactant function at birth. Pulmonary surfactant is a unique mixture of lipids and proteins that reduces surface tension at the air-liquid interface, preventing collapse of the lung at the end of expiration. SP-B and ABCA3 are required for the normal organization and packaging of surfactant phospholipids into specialized secretory organelles, known as lamellar bodies, while both SP-B and SP-C are important for adsorption of secreted surfactant phospholipids to the alveolar surface. In general, mutations in the SP-B gene SFTPB are associated with fatal respiratory distress in the neonatal period, and mutations in the SP-C gene SFTPC are more commonly associated with interstitial lung disease in older infants, children, and adults. Mutations in the ABCA3 gene are associated with both phenotypes. Despite this general classification, there is considerable overlap in the clinical and histologic characteristics of these genetic disorders. In this review, similarities and differences in the presentation of these disorders with an emphasis on their histochemical and ultrastructural features will be described, along with a brief discussion of surfactant metabolism. Mechanisms involved in the pathogenesis of lung disease caused by mutations in these genes will also be discussed.
Reactivity of T-Nb2O5 or H-Nb2O5 towards V2O5. Synthesis in the solid state and properties of V4Nb18O55
Authors: Tabero Piotr , Filipek Elzbieta , Piz Mateusz
Published: February 2009

The IR spectrum of V4Nb18O55 has been compared with the IR spectra of selected niobates of known structures to show structural relations between these compounds. This comparison shows that V4Nb18O55 has crystal structure related to T-Nb2O5, W16Nb18O94 and Ba2NaNb5O15. On the other hand, reaction between V2O5 and H-Nb2O5 yields a solid solution of V2O5 in VNb9O25. It has been proposed two models of synthesized solid solution with formulas V1+xNb9-xO25 or V1+xNb9O25+5x/2.Independently of Nb2O5 polymorph, used for synthesis, the metastable compound VNbO5 cannot be synthesized in the solid state below 650°C
Simultaneous spectrophotometric determination of minoxidil and tretinoin by the H-point standard addition method and partial least squares
Authors: Bordbar Maryam , Yeganeh-Faal Ali , Ghasemi Jahanbakhsh , Ahari-Mostafavi Mohammad , Sarlak Nahid , Baharifard Mohammad
Published: February 2009

A simple, sensitive and selective spectrophotometric method for simultaneous determination of tretinoin and minoxidil using partial least square (PLS) calibration and H-point standard addition method (HPSAM) is described. The results of the H-point standard addition method show that minoxidil and tretinoin can be determined simultaneously with the concentration ratio of tretinoin to minoxidil varying from 2: 1 to 1: 33 in mixed samples. A partial least squares multivariate calibration method for the analysis of binary mixtures of tretinoin and minoxidil was also developed. The total relative standard error for applying the PLS method to eleven synthetic samples in the concentration range of 0–10 μg mL−1 tretinoin and 0–32 μg mL−1 minoxidil was 2.59 %. Both proposed methods (PLS and HPSAM) were also successfully applied in the determination of tretinoin and minoxidil in several synthetic pharmaceutical solutions.
Effect of ethyl acetate on carbohydrate components and crystalline structure of pulp produced in aqueous acetic acid pulping
Authors: Gümüşkaya Esat , Usta Mustafa , Balaban Uçar Mualla
Published: February 2009

The aim of this study was to investigate the changes in carbohydrate components and the crystalline structure in hemp bast fibers by adding ethyl acetate to acetic acid/water pulping processes. It was found that ethyl acetate added to acetic acid/water process had a positive effect on yield, viscosity and carbohydrate components in pulp. It was assumed that the delignification ratio increased by adding ethyl acetate to aqueous acetic acid pulping. Xylose content in hemp bast fibers was affected more negatively in the ethyl acetate/acetic acid/water process than in the acetic acid/water one. Crystallinity and crystallite size were higher in pulp sample obtained by the acetic acid/water process without ethyl acetate.
Inverse gas chromatographic characterization of Porapak Q as an extractant of pollutants from aqueous media
Authors: Moustafa Nagy , El-Desouki Doaa
Published: February 2009

The surface of Porapak Q was characterized by inverse gas chromatography (IGC) carried out by the determination of dispersive and specific adsorption components of Porapak Q surface, calculating γsd and -ΔH as parameters, respectively. An interpretation was given based on the chemical structure of Porapak Q. The obtained results were confirmed through the surface Lewis acidity and basicity constants, K a and K b, respectively, correlating well with the determined thermodynamic parameters.
Exposure to High Fluoride Drinking Water and Risk of Dental Fluorosis in Estonia
Authors: Indermitte Ene , Saava Astrid , Karro Enn
Published: February 2009

The purpose of this study was to assess exposure to drinking water fluoride and evaluate the risk of dental fluorosis among the Estonian population. The study covered all 15 counties in Estonia and 93.7% of population that has access to public water supplies. In Estonia groundwater is the main source for public water supply systems in most towns and rural settlements. The content of natural fluoride in water ranges from 0.01 to 7.20 mg/L. The exposure to different fluoride levels was assessed by linking data from previous studies on drinking water quality with databases of the Health Protection Inspectorate on water suppliers and the number of water consumers in water supply systems. Exposure assessment showed that 4% of the study population had excessive exposure to fluoride, mainly in small public water supplies in western and central Estonia, where the Silurian-Ordovician aquifer system is the only source of drinking water. There is a strong correlation between natural fluoride levels and the prevalence of dental fluorosis. Risk of dental fluorosis was calculated to different fluoride exposure levels over 1.5 mg/L.
4-[(Pyridin-3-ylmethylene)amino]phenylhexadecanoate
Authors: Ha Sie-Tiong , Ong Lay-Khoon , Win Yip-Foo , Koh Teck-Ming , Yeap Guan-Yeow
Published: February 2009

A new Schiff base 4-[(pyridin-3-ylmethylene)amino]phenylhexadecanoate was synthesized and its IR, 1H NMR, 13C NMR and MS spectroscopic data are presented.
4-[(Pyridin-3-ylmethylene)amino]phenyltetradecanoate
Authors: Ha Sie-Tiong , Ong Lay-Khoon , Win Yip-Foo , Koh Teck-Ming , Yeap Guan-Yeow
Published: February 2009

A new Schiff base 4-[(pyridin-3-ylmethylene)amino]phenyltetradecanoate was synthesized and its IR, 1H NMR, 13C NMR and MS spectroscopic data are presented.
A Method for Digital Color Analysis of Spalted Wood Using Scion Image Software
Authors: Robinson Sara C. , Laks Peter E. , Turnquist Ethan J.
Published: February 2009

Color analysis of spalted wood surfaces requires a non-subjective, repeatable method for determining percent of pigmentation on the wood surface. Previously published methods used human visual perception with a square grid overlay to determine the percent of surface pigmentation. Our new method uses Scion Image©, a graphical software program used for grayscale and color analysis, to separate fungal pigments from the wood background. These human interface processes render the wood block into HSV (hue, saturation, value, within the RGB color space), allowing subtle and drastic color changes to be visualized, selected and analyzed by the software. Analysis with Scion Image© allows for a faster, less subjective, and easily repeatable procedure that is superior to simple human visual perception.
Surface Acoustic WaveAmmonia Sensors Based on ST-cut Quartz under Periodic Al Structure
Authors: Hsu Cheng-Liang , Shen Chi-Yen , Tsai Rume-Tze , Su Ming-Yau
Published: February 2009

Surface acoustic wave (SAW) devices are key components for sensing applications. SAW propagation under a periodic grating was investigated in this work. The theoretical method used here is the space harmonic method. We also applied the results of SAW propagation studied in this work to design a two-port resonator with an Al grating on ST-cut quartz. The measured frequency responses of the resonator were similar to the simulation ones. Then, the chemical interface of polyaniline/WO3 composites was coated on the SAW sensor for ammonia detection. The SAW sensor responded to ammonia gas and could be regenerated using dry nitrogen.