bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pressurized Mud Cap Drilling in Qatar's North Field
Authors: Niznik Michael R. , Elks William C. , Zeilinger Sabine C. 
Published: February 2009

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

AbstractWells 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.
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

Abstract
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

AbstractA 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.