bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Directional Difficulty Index - A New Approach to Performance Benchmarking
Authors: Oag Alistair W. , Williams Mike 
Published: December 2007

Abstract
High-level performance measures, used to benchmark drilling performance, have been the subject of several industry-sponsored reports. With the advent of truly three dimensional directional wells, these benchmarks no longer measure true drilling performance due to the uniqueness of each wells' profile. This problem is common to both operators and service companies when both groups are striving to demonstrate their added value to their clients.
This paper puts forward a simple methodology called the Directional Difficulty Index, (DDI), which provides a first-pass evaluation of the relative difficulty to be encountered in drilling a directional well. This index was developed through use of a straightforward questionnaire distributed so as to reach consensus on identifying key performance measures. The index can be used to group wells of similar characteristics and complexity. Data from these similar groups can then be examined for learning-curve improvements and thus provide a measure of performance. This was not possible with previous benchmarks for random well designs.
The key value drivers of quality, service and time can then be examined on a like-for-like basis. The key principles of performance measurement can then be addressed with a much more balanced approach focused on value drivers, adding value, demonstrating organizational learning, linking planning, strategy and service company performance.
Actual well data demonstrate the validity of the Directional Difficulty Index as a methodology for the performance benchmarking process, allowing the user to evaluate the same process on wells of similar complexity and measure improvements in that process. Goals and targets set for future wells can also be used to truly measure real performance to the benefit of both the service provider (remunerative) and the service user (cost as opposed to price).
Deepwater Subsalt Development: Directional Drilling Challenges and Solutions
Authors: Cromb J. R. , Pratten C. G. , Long M. , Walters R. A. 
Published: December 2007

Abstract
Gulf of Mexico deepwater drilling activity has increasingly discovered economic hydrocarbon deposits lying below salt formations. Subsalt reservoir development is becoming one of the major challenges for operators, with the salt providing challenges in both seismic interpretation and drilling.1 This paper looks at how one operator successfully undertook a subsalt development in Mississippi Canyon. The project covered the completion of an exploratory well and the directional drilling of two development wells which produced from a state-of-the-art subsea system of wells, manifold and flowlines. The Gemini development was one of the first deepwater subsalt projects in the Gulf of Mexico and provided unique challenges for the directional drilling operations. These challenges included kicking off the well riserless in large-diameter hole, controlling wellbore trajectory through more than 3000 ft of salt and executing sidetracks to revised bottomhole targets after initial geological evaluation
Success was achieved through detailed planning from a directional drilling aspect that considered the geological, engineering and economic requirements and novel application of technology. In this paper we describe how these challenges were met from the standpoint of wellbore trajectory, bottomhole assembly design and operational procedures, and we review the performance of the directional drilling operations.
The Economic Viability of Multilateral Wells
Authors: Oberkircher James P. 
Published: December 2007

AbstractMultilateral wells are receiving much attention in the oil industry. Despite the increasing amount of publicity, multilateral wells in practice account for only a small fraction of the total number of wells drilled in the world today. One reason for this limited application may be that the economic benefit of drilling these wells may be in question, even though the higher construction costs associated with drilling a multilateral well can usually be justified on paper by the resulting, projected rise in well producibility.Several factors can contribute to the economic success of a multilateral project:Reservoir Charecteristics Production and Facilities Capabilities Operator and Service Company experience with multilateral installations. Technological advances and refinements in the multilateral drilling and completion system Complexity of the drilling program Effective contingency planning prior to the commencement of the drilling operations.This paper examines multilateral wells that have been drillled in the North Sea and reviews their true economic impact. The paper proposes a balanced score card for tracking and benchmarking the economic performance of these wells. The paper also discusses suggestions for enhancing the probablility of both the economic and technical succes of multilateral wells.
Improving Drilling Performance in Troublesome Clay Formations in the Heidrun Field
Authors: Stjern G. , Horsrud P. , Agle A. 
Published: December 2007

Abstract
Despite the use of inhibitive water-based mud (KCl), high pump rates to obtain good hole cleaning and relatively high mudweight, problems with cavings, pack-offs and lost circulation persisted when drilling Tertiary clay formations in the Heidrun field offshore Mid-Norway. A study was therefore initiated, including extensive data collection (logging and coring of the shale) and subsequent core testing, data analysis and evaluation of field experience.
The study showed that the major problem zone was not the low-density zone as anticipated. However, the core revealed a fractured and crushed zone, which was eventually found to be the main source of the problem. The study has resulted in a new strategy. An improved borehole stability model has been established, and the mud and operational strategy has been revised. The mudweight has been reduced, the salt content of the mud has been reduced, and good hole cleaning is obtained through a low-viscosity mud which is kept close to turbulent flow. Furthermore, wells are now planned without steering in these formations, if possible.
An economic evaluation of the study was also performed, showing a substantial benefit/cost ratio. So far, the cost reduction for an average well is close to 20 MNOK (ca. 2.5 million USD). With more than 50 wells left to drill in the field, the potential for cost-saving is large. Additionally, there is a huge and non-quantified effect from accelerated production.
Problems in Drilling through Abnormal / Subnormal Pore Pressures of Post Eocene Formations in the Potwar Basin of Pakistan with Special Reference to Adhi Field
Authors: Afzal M. , Rasool S. Anisur 
Published: December 2007

Abstract
The drilling conditions in the Potwar basin, the traditional oil producing region of Pakistan, are extremely tough, hazardous and challenging due to sudden reversal of pressure regimes from near geostatic to near hydrostatic. Pressures close to geostatic have been encountered at shallow depths because of the uplifting of the Himalayan foreland, resultant of collision between the Eurasian plate and the Indian plate. The orogenic movements in the presence of huge salt thickness created these ‘pop up’ structures which brought associated pressures to shallower depth. These sudden pressure reversals have resulted in the inflow of high pressure formation water and severe losses of circulation simultaneously, causing internal and surface blowouts. The other related problems which have resulted in the premature abandonment of wells are casing collapse, bridging and tightness of hole, caving and heaving of shale and stuck pipe due to differential pressure.
A number of wells have been drilled in Potwar basin by different oil companies including Pakistan Petroleum Limited (PPL). In this paper we first discuss the origin of these high pressures and the pressure reversals. Then we will discuss the experiences gained during the drilling of 12 wells in the Adhi field and how it has led to the development of a methodology by PPL for predicting and handling these abnormal/subnormal pore pressures. Out of the 12 wells, 6 wells were prematurely abandoned because of these high pressure problems. Normal Drilling Exponent (Dxc) pore and fracture pressure gradient prediction/detection technique has limited effectiveness in this area. The water inflows were controlled by raising mud weight and placing barite plugs. The losses of circulation were cured with LCM pills and cement plugs. The loss and gain situation was very well negotiated with LCM pill or cement plug against the thief zones and the barite plug against the inflow zones. The casing design was changed and the trouble string was introduced to isolate high and low pressure zones. The cement design was also changed and new methodology was introduced to control the water flow through the annulus after casing cementation.
Drilling Optimization Using Drill-bit Seismic in the Deepwater Gulf of Mexico
Authors: Armstrong Philip , Nutt Leslie , Minton Reginald 
Published: December 2007

Abstract
Drill Bit Seismic has been used successfully on land and in shallow marine environments for many years. The technique utilizes the acoustic energy radiated during the drilling process to provide vital information about the drilling operation. It provides time-depth and formation velocity information at the well site, allowing the position of the bit to be plotted on the surface seismic section as drilling progresses. By generating look ahead VSP images, the approach to critical horizons such as casing points or overpressure zones, can also be monitored, leading to significant cost savings and enhanced safety.
The technique has recently been extended to water depths of almost 4000ft in the Gulf of Mexico, where time-depth data was obtained down to a depth of 12500ft, drilling in soft formations with a rollercone bit. This information can be used to calibrate pre-drill velocity models and helps to prevent unexpected occurrences during drilling.
The Use of Resistivity-at-the-Bit Images and Annular Pressure While Drilling in Preventing Drilling Problems
Authors: Rezmer-Cooper Iain , Bratton Tom , Krabbe Helle 
Published: December 2007

Abstract
The cost of well construction can dramatically exceed budget if the drilling operations are plagued by wellbore instability problems, and excessive time and resources are needed to free stuck pipe, regain circulation, or clean the hole efficiently.
Annular pressure while drilling has recently been recognized as one of the key downhole measurements for aiding real-time diagnosis of the condition of the wellbore and the drilling fluids. In addition to conventional drilling mechanics measurements, time-lapse logging-while-drilling (LWD) documents the dynamic change in the measured properties during well construction. This can be essential in diagnosing wellbore failure, and the mechanism of failure, in addition to dynamic processes such as cuttings build-up.
An example from a horizontal well in the North Sea is used to illustrate how LWD resistivity images can be used in conjunction with annular pressure while drilling measurements to detect the onset of drilling-induced fractures. Although the majority of azimuthal images have been acquired to understand the geology and petrophysics of reservoirs, the images usually contain features resulting from geomechanical processes.
Analysis of these features reveals important information for optimizing drilling and understanding the geomechanics of the well. Coupling the resistivity images to the pressure measurement enables problem identification, and the correct remedial actions to be taken to optimize the drilling operation, for example, ensuring that swab and surge pressures are kept to a minimum, and correct hole cleaning procedures are utilized to prevent irreversible formation breakdown.
Field Test Results for a Real-Time Intelligent Drilling Monitor
Authors: Corser G. P. , Harmse J. E. , Corser B. A. , Weiss M. W. , Whitlow G. L. 
Published: December 2007

Abstract
Under funding from both Sandia Labs and GRI, Marconi has developed a real-time system, called the Intelligent Drilling Monitor (IDM), to detect circulation problems at the rig site. IDM monitors standard surface measurements, measured flow out, and, if available, measured flow in. Using these measurements, IDM performs real-time modeling, problem detection, and problem diagnoses using Kalman filters, advanced statistical processing, and artificial intelligence. The problems that can be detected by IDM include loss of circulation, kicks, pump efficiency losses, pump stroke counter errors, inflow meter errors, outflow meter errors, bit plugs, and washouts. This paper will present the results of processing field data from two different wells through IDM.
Lateral Drillstring Vibrations in Extended-Reach Wells
Authors: Heisig G. , Neubert M. 
Published: December 2007

Abstract
Drillstring dynamics and hole cleaning problems are some of the most important limiting factors in extended reach applications. Here, long sections of the drillstring lie on the low side of the wellbore while rotating. When the rotary speed exceeds a critical threshold the drillstring starts to "snake", sliding up and down the borehole wall. If rotated well beyond the threshold speed, the drillstring will eventually start to "whirl" which can cause severe damage to string components after only a short period of time.
In this paper an analytical solution for the threshold rotary speed is derived and presented. It is shown to be in the range of the rotary speeds used in modern extended reach applications. The analytical results are verified using a versatile finite element formulation to model the drillstring in greater detail. Animated time domain simulations with this model provide deeper insight into the dynamic behavior of the drillstring.
Conclusions on improved drilling practices in extended reach applications - especially with respect to hole cleaning problems - are drawn from the theoretical results.
Drilling Dynamics in the Presence of Mud Flow
Authors: Schmalhorst Bernd , Brommundt Eberhard , Baumgart Andreas , Richter Uwe 
Published: December 2007

Abstract
A new drillstring dynamics model takes into account the interaction between the drill string and the instationary mud flow circulation. Most papers in the past neglected the influences of fluid-structure coupling forces and fluid flow excitation forces on drillstring dynamics. The drill string under consideration includes a Bottom Hole Assembly that consists of a PDC bit, a mud driven positive displacement motor, and optionally a Measurement While Drilling pulser. Besides mud flow vibrations, the assembly is excited by axial bit vibrations caused by a profiled bottomhole, motor imbalance and friction effects between the borehole wall and the string. Coupled axial, torsional, lateral and pressure vibrations are calculated. Simulation results include damaging bit bouncing, self excited stick-slip and whirl effects of the assembly. Vibration response of a positive pressure MWD pulser is also treated. The application helps to avoid critical operating conditions and to select the corresponding system parameters. Therefore a significant reduction in project cost can be achieved.
Automatic Inclination Controller: A New Inclination Controlling Tool for Rotary Drilling
Authors: Yinghui Liu , Yinao Su 
Published: December 2007

Abstract
The working principles, structural features and application of Automatic Inclination Controller(short in AIC) designed by Professor Su Yinao are introduced in this paper. It includes the analyses of controlling principles of the tool and the mechanical properties of the BHA with AIC. As a new type of adjustable stabilizer, AIC provides one downhole closed-loop system which relies solely on hydraulic feedback. The BHA with AIC reduces the number of round trip and saves drilling costs. It especially meets the requirements of China's oil fields.
Improvement on the Procedure in Exploration Well By Unbalanced Drilling: A Case History in BS7 Well in People's Republic of China
Authors: Yongfeng Guo 
Published: December 2007

Abstract
The paper has discussed some questions in unbalanced drilling, and state that the most important question is determining the information pressure gradient before drilling in the design. The paper put out some principles and formulae for determining the information pressure gradient, which are different from that were put forward by some scholars in past to some extent. The author introduced a case history about unbalance drilling – BS7 well, which was drilled in Dagang oil field, Tianjin city, People's Republic of China, and explain the application of the principles and formula in the well. There are two points in this paper. First, in term of new principle and formula of design formation pressure gradient, the time that is from starting show of some omen to having blow out in well, is longer than predicting in other method in past, and this predicting had been testified by the practise in the well. So the operator has more time to deal with well kick and protect the blow out of well, in other words, designer can take a risk to determine the formation pressure gradient more than in past. Second, when determining the formation pressure gradient, the designer would not consider abnormal layers, which are much smaller in thick than the length of naked section in the hole. Because not only the operator have enough time to deal with well blow out if the blow out really happen, but also some situations have not happened, in speciality to the block faulted oil field, for example, Dagang oil field. The mainly reason is the level of forecast the formation pressure gradient is not very accurate, and it is not worthy of raising the value of it in the whole section in well only according to a predicting value of the formation pressure gradient in shorter section, which predicting value of it mainly depend on the data from neighbor wells. Since beginning of 1999, the most of oil fields in main land of China have accepted these principle in the drilling of explored well so that decease the mud density, and get obvious effect, which have found several huge oil fields so far.
A method to realize the surface-to-downhole communication while drilling
Authors: Zhou Jing , Fu Xingsheng , Shang Haiyan , Li Changxing 
Published: December 2007

Abstract
One of the developments, at present, on drilling technology is to realize closed-loop control of wellbore path geologic pilot drilling. It is also a new high technical engineering that integrates drilling, machinery, electronic, microelectronic, sensors and control technology into a whole. This article is involved in the research of realization on communication channel necessary to closed-loop control of the project. It is well known that there are commercial products used in up-channel from the well to ground, and no one from ground to downhole. The research is by signaling "1" or "0" indicated as the clear difference of the vibration of drill pipe at operation and stopping, based upon that, and then to code the signal for downward transfer. It has been proved that method for signal transfer could be realized in normal well condition at indoor and oil field.
Detection of Asphaltene Deposition by Capillary Flow Measurements
Authors: Broseta D. , Robin M. , Savvidis T. , Féjean C. , Durandeau M. , Zhou H. 
Published: December 2007

Abstract
This paper presents an experimental methodology that allows a sensitive determination of the onset and rate of deposition in asphaltene-containing fluids when the pressure, temperature, or fluid composition are varied. This determination is inferred from pressure drop measurements across a capillary tube in which the fluid is injected at a constant flow rate and at specified conditions of temperature, pressure and composition. When the conditions for deposition are met the pressure drop across the capillary tube is no longer stationary but increases with time as a result of the buildup of a deposition layer on the tube walls.
In the experimental set-up that has been constructed, the fluid composition is controlled by co-injecting the various fluid components into the capillary by means of different pumps. This setup has been utilized to determine, at some given temperature and pressure, the deposition envelope of systems made of crude oil, solvent (xylene) and precipitant (heptane). The measured deposition points coincided with bulk flocculation thresholds determined by a conventional light transmission method. The light transmission method was, however, difficult to for fluids with a very low asphaltene content, whereas the proposed method was efficient for fluids containing as low as 0.04 wt.% asphaltenes.
The rate of deposition was observed to increase with the distance from the deposition onset. Reversibility of deposition was significant only when the asphaltene-containing fluid was returned to conditions remote from those of the deposition onset.
Controlling Gelation Time and Microgel Size for Water Shutoff
Authors: Chauveteau G. , Omari A. , Tabary R. , Renard M. , Rose J. 
Published: December 2007

AbstractInjecting stable preformed microgels as relative permeability modifiers to reduce water production is an attractive new procedure to minimize the risk of formation plugging and consequently of inefficiency of in-depth treatments. This paper describes the mains results of theoretical and experimental investigations carried out to know how to control both size and conformation of microgels formed under constant shear flow. Since gelation kinetics strongly depends on crosslinker chemistry, Zr K-edge XANES and EXAFS studies of zirconium speciation were performed under the complex conditions of polymer gelling for water shutoff. The results show that crosslinking species may be dimers, tetramers and associations of tetramers depending on pH and Zr concentration in presence of lactate. In polymer gels, Zr monomers were observed. The generalisation of our crosslinking-under-shear theory described in this paper provides simple power laws. The microgels formed in diffusion regime are isotropic and their size decreases significantly as shear rate increases, while when formed in correction regime, they are anisotropic and their size decreases negligibly with shear rate. All experimental data are in agreement with this theory so that conclusions can be derived to optimize microgel preparation as a function of their role in the aimed application, either relative permeability modifiers for water shutoff or viscosity enhancers for polymer flooding.