bluuebunny/crossref_metadata_2025_split huggingface dataset:
Underbalanced Drilling Dynamics: Two-Phase Flow Modeling and Experiments
Authors: Lage A. C. V. M. , Fjelde K. K. , Time R. W. 
Published: December 2007

Abstract
A dynamic model, based on the drift-flux formulation, is presented for treating transient phenomena in UBD operations. A set of mechanistic steady state procedures for dealing with the definition of flow patterns, pressure drops, gas volumetric fractions, and in-situ velocities completes the model. The iteration between those mechanistic laws and the conservation equations is discussed. The numerical solution, which presents an easy implementation, uses a composite explicit scheme that properly combines the second order MacCormack and the first order Lax-Friedrichs methods, reducing false oscillations and numerical diffusion. In addition, details about the boundary treatment are also presented.
Model predictions are validated through comparison to full-scale experimental data in two distinct transient situations. First, a typical unloading scenario in an underbalanced operation is studied. Further, the model simulates the injection of a high velocity single pulse and a sequence of two pulses of a gas-liquid mixture. Measured variables as pressure and returning liquid and gas rates at surface are compared to the predicted ones. The comparisons address model limitations and improve the understanding of the physics involved.
Cements for Long Term Isolation – Design Optimization by Computer Modelling and Prediction
Authors: di Lullo Gino , Rae Phil 
Published: December 2007

Abstract
Today, development of high early compressive strength (CS) is a key performance specification for oilwell cementing. Early strength is important to ensure structural support to the casing and hydraulic/mechanical isolation of downhole intervals. Delays in strength development cause significant amounts of lost time due to the need to Wait-On-Cement. Thus, drilling operations cannot proceed and the rig must sit idle until the cement is deemed hard enough to continue.
The actual development of strength in cement systems is dependent on a number of factors. The type of cementitious material is important due in part to chemistry and in part to granulometry. Slurry density is considered critical – lower density has, traditionally, been associated with lower strength. Temperature is a key parameter and, to a lesser extent, the pressure. Less appreciated, is the influence of the many types of additives that are included in slurry formulations. Correct selection of cement and additives allows slurry tailoring to achieve "a strong cement" that will support mechanical stresses that happen during the well productive life. Since cement is the primary means of isolation, its integrity as a sealing material should be paramount.
Under confining pressure, cement compressive strength is several times higher that the values obtained from an unconfined API test. In fact, the ultimate compressive strength of a wide variety of slurries is similar to that of the surrounding reservoir rock, regardless of initial slurry density. In the long term, more important than compressive strength is the ductility/compliance that set cement has to support down-hole stresses imposed by pressure and temperature oscillations during drilling, work-over and production operations. In the vast majority of well operations, cement failure occurs under tensile loading, not under compression. Poor appreciation of this has led to the routine use of higher density slurries for many applications. Such slurries may be not only unnecessary but also positively harmful, since they can produce more brittle cements that fail under downhole stresses. This paper describes a method of designing cement slurries using a simulator that models cement setting and strength development. Instead of obsolete rules of thumb, mechanical properties of set cement, formation and casing responses to cyclic stresses during the well life are used to optimise designs for early times and long term. Finally, a few case histories are presented, demonstrating the benefits of this new design methodology to produce cost effective cement slurries for one isolation.
Zonal Isolation in Stimulation Treatments and Gas/Water Shutoff Using Thermally Compensated Inflatable Packers and Plugs
Authors: Wilson Paul , Hoffman Corey E. 
Published: December 2007

Abstract
This paper provides laboratory and field-test results of a thermally compensated fluid-inflated packer system. This system greatly reduces the chance of sealing-element failure when inflatable packers or plugs are used where the borehole fluid changes temperature more than 50° F (10°C). To date, a primary cause of failure in achieving zonal isolation while using inflatable packers and plugs is the change in temperature of the borehole and inflation fluids once the packer is set. Thermally compensated inflatable packers are an innovation in nflatable packer technology. These packers act in a manner unlike conventional inflatables, which are susceptible to temperature changes as little as 50° F (10°C) between borehole and internal fluids. These temperature changes can cause the fluids inside conventional inflatable packers either to expand and rupture the element or to contract and cause the element to lose its seal on the casing wall. Qualification tests and resulting data will be presented as well as data acquired after a thermally compensated inflatable plug system was deployed in a water injection well. Possible applications include those in which a fluid inflatable packer, straddle acker, or plug would be used and subjected to temperature changes in excess of 50° F (10°C).
The introduction of thermally compensated inflatable packers offers a more technically effective, economical means of zonal isolation in almost any cased-hole application. This technology is equally applicable for openhole applications.
Well Control of an Influx from a Fracture Breathing Formation
Authors: Ashley Paul R. 
Published: December 2007

Abstract
Hydrocarbon influxes into the wellbore while drilling are typically caused by over-pressured formations, where mud weight is insufficient to control the pore pressure of the formation drilled. Formation permeability and over-pressure determine the intensity of the kick. Well kill procedures in such situations are standard industry wide. Shut in drillpipe pressure is used to determine the pore pressure of the formation, and the driller's or weight and wait method is used to remove the hydrocarbon influx from the well. Hydrocarbon influxes associated with fracture breathing are much less common, and methods to deal with such influxes are not taught within the drilling industry. This paper describes two case studies: the first, Bard–1, an exploration well in the Timor Sea, offshore Australia, describes a well control situation that was initially interpreted as over-pressure. The well could only be killed by pumping cement. Investigation showed that the influx mechanism was a fracture breathing and hydrocarbon swap out mechanism. The high mud weights used in the attempt to kill the well actually exacerbated the situation. The second case study, Jura-1 which was located nearby Bard-1, describes design and procedures used to manage a similar influx mechanism. These were implemented successfully enabling the well to achieve its objectives.
The Benefits of Monitoring Torque & Drag in Real Time
Authors: Vos Bart E. , Reiber Frank 
Published: December 2007

Abstract
Monitoring Torque and Drag effects in real time has been done for some time now in the oil industry. However, the service is still used only in a small percentage of the total drilling hours and the analyzing techniques used are quite diverse.
The real-time Torque and Drag technique described in this paper is in many ways advantageous compared to the precalculated hook load (HKLD) and surface torque comparison techniques typically used in the industry. Several delimiters are filtered out of the equation and current drilling conditions are used automatically and directly in the calculations and evaluations. Monitoring Torque and Drag in the described way gives direct information on current down hole drilling conditions and predicts upcoming situations. This allows the driller to go closer to the limit of the drillstring load capacity in a controlled manner, thereby optimizing tool use whilst maintaining safety on the rig.
Combined monitoring of Torque and Drag and the Equivalent Circulating Density (ECD) shows clear correlations, and gives additional information on hole cleaning conditions. The technique also helps to optimize reaming programs - reaming correctly and only when necessary -, to save rig time and improve weight transfer.
Monitoring Torque and Drag in real time is part of a service package that analyzes the available data at the rig-site and converts them into valuable information. This information is subsequently used to improve well profitability by optimizing drilling efficiency and increasing well productivity.
Causes and Remedies of Drillstring Failures while Drilling Medium Radius Horizontal Wells (Field Study)
Authors: Amro M. M. 
Published: December 2007

Abstract
Improvements in horizontal drilling technology made it possible to drill almost in all types and shapes of reservoirs. No change, however, was made in the design of drill pipes to overcome the high stresses especially for drill pipe rotating in medium or short radius horizontal wells. During drilling of some horizontal wells in the Middle East area, an abnormal amount of tubular failure was noticed in the drill string being used.
This paper presents a field case study of drill string failure during drilling of medium radius horizontal wells.
Investigations as well as a metallurgical evaluation were conducted in an attempt to establish the possible causes of the drill string failures. Other possible reasons for drill string failures and suggestions to minimize the bending stress of drill pipes are also discussed.
New Bio-Polymers for Drilling, Drill-in, Completions, Spacer Fluids and Coiled Tubing Applications
Authors: Navarrete R. C. , Seheult J. M. , Coffey M. D. 
Published: December 2007

Abstract
Xanthan gum has been used extensively as a viscosifier in the oil industry for different applications due to its unique rheological properties. In this paper we introduce two biopolymers for use in drilling, drill-in, completions, spacer fluids and coiled tubing applications. The first bio-polymer yields higher viscosities and better temperature stability at lower polymer concentrations that welan and xanthan gum due to its higher molecular weight; this polymer is particularly effective in low salt fluids. The second bio-polymer has improved solubility in high density CaCl2 brines.
Viscosity data over a wide shear rate range is presented comparing the new bio-polymers with xanthan and welan gum at temperatures between 75°F to 300°F. Viscoelastic measurement and settling test are presented to demonstrate the effect of elasticity of the bio-polymers on solids transport and suspension capabilities. Fluid-loss, formation damage tests and friction pressure tests in coiled tubing are also shown.
Development Process and Field Applications of a New Ester-Based Mud System for ERD Wells on Australia's Northwest Shelf
Authors: Eckhout Daniel , Dolan Shane , Gogan Ray , Ledgister Hanjo , Mowat Carol , Tipton Paul , Ewen Bruce , Dye William 
Published: December 2007

Abstract
Extended reach wells drilled from the Goodwyn Alpha platform are highly aggressive and have been drilled with a variety of invert-emulsion mud systems. Historically, mud system selection for these wells was based on compliance to environmental regulations and satisfaction of technical criteria. In order to take a more proactive approach to mud system selection and to raise environmental standards to new levels, an initiative was undertaken to replace the environmentally acceptable, and technically competent mud system being used on Goodwyn with a new ester-based system. Ester-based mud systems are considered the "system-of-choice" in terms of environmental acceptability and possess inherent lubricating qualities for torque and drag reduction.
This paper describes the development process and 4 successful field applications of the new ester-based mud system. A new ester, which exhibits the lowest kinematic viscosity of commercially available esters, was identified and selected for use. New and innovative technologies were introduced in the laboratory development and field applications to address barite sag, hole cleaning efficiency and hydrolytic stability.
The system development and field testing processes were enhanced by daily communication with the development teams in Aberdeen, Houston and Perth. Down-hole friction factors were significantly lower than modeled predictions. Barite sag problems encountered on previous wells were eliminated, and hole cleaning efficiency was optimized.
Jetting Clean-Up of Formation Damage Caused by the Drilling Process
Authors: Way P. W. , Howard P. , Johnson A. 
Published: December 2007

Abstract
We report here a laboratory study that considers the potential of jetting technology for removing formation damage produced in the drilling process.
The effective placement of chemical treatments over long open hole sections is an unresolved problem. The treating chemicals are often lost to the formation in relatively small areas resulting in poor clean-up in large sections of the wellbore. The jetting technique, which has been investigated as part of an on-going research program, could be used with coiled tubing or conventional drill pipe and would provide effective coverage along the whole length of the wellbore. The use of barite as a weighting agent in the drilling fluid rather than calcium carbonate is possible because the material is removed physically and not chemically. This is beneficial as it means that the total solids volume in the drilling fluid is lowered.
We have considered the effects of abrasive laden jetting fluids on two sandstones of differing permeabilities using two water based drilling fluids and two types of weighting agent. Further tests using water only as the jetting fluid are reported
We find that in all cases the jetting removed any external filtercake that was present, and is also capable of removing rock material. On the higher permeability sandstone we see no improvement to the level of formation damage from jetting even with the filtercake removal. SEM studies reveal pore space blocked by particles generated during the jetting process and or by the abrasive material. For the lower permeability sandstone we note an improvement with jetting and no evidence of invaded solids material.
We have further considered the pressure required to initiate flowback after jetting compared with production straight back through the filtercake. We find that the pressure to initiate production is reduced by over 40% for all the fluids tested on both rock types.
Application of Very Heavy Mud and Cement in a Wildcat
Authors: Ezzat A. M. , Jennings S. S. , Al-Abdulgader K. A. , Al-Hammad M. A. 
Published: December 2007

Abstract
Unusual pressure was encountered while drilling through the Triassic lower Jilh formation in a wildcat. The well was one of the deep exploration wells for non-associated gas, in the northern fields, targeting the Permian Khuff and Pre-Khuff gas reservoirs. Mud weight was increased from 80-pcf (10.7 lb/gal) to 156-pcf (20.86 lb/gal) with barite. The drill-string became stuck against the formation above the high-pressure zone. A specially designed spotting fluid was used to disperse the wall cake and free the pipe. Well-killing operation continued with the drill-string inside the casing. Achieving higher mud densities required the use of hematite and phasing out the barite until the well was controlled with 162-pcf (21.66 lb/gal), which is the heaviest drilling mud ever used in Saudi Arabia’s oil fields.
Extensive laboratory work was carried out at the well site. The mud system formulation design was adjusted and maintenance treatment was carried out in timely manner. Drilling operations were commenced safely to the casing point where the temperature exceeded 300°F. Successful bit selection for this interval lead to a New World record run in rotating hours. A 9-5/8" liner was run and cemented with specially designed 170-pcf (22.73 lb/gal) cement slurry, which was also a challenge. The liner was extended to surface and cemented in two stages with 145-pcf (19.39 lb/gal) cement. This paper presents the laboratory data along with the field mud and cement formulations used.
A Newton-Raphson Iterative Scheme for Integrating Multiphase Production Data into Reservoir Models
Authors: Wu Zhan 
Published: December 2007

Abstract
This paper presents a new linearized iterative algorithm for building reservoir models conditioned to multiphase production data and geostatistical data. The significant feature of the proposed algorithm is that the computation of the sensitivity coefficients of production data with respect to model parameters can be avoided. This leads to dramatic reduction of computational cost. Instead of generating the sensitivity matrix as required for the least-squares algorithms, the proposed approach relies on solving the inversion equations which are derived from the necessary conditions for a functional extremum.
It is proved that the proposed method requires considerably less computational effort than the traditional algorithms such as the Gauss-Newton method, the Levenberg-Marquardt method and the generalized pulse-spectrum technique (GPST). This is because the computation of the sensitivity coefficients makes the traditional algorithms computationally intensive. However, for the proposed linearized iterative scheme, the computational requirement only depends on the time steps used in the reservoir simulator rather than the number of parameters or the number of observed data.
The linearized iteration scheme converges fast since the inversion equations can be solved through the Newton-Raphson method. At each iteration, the new approach requires solving the finite difference equations and the linear adjoint equations only once, respectively. Since the solver for the flow equations can be used to solve both the adjoint equations and the inversion equations, the proposed algorithm can be easily applied to commercial reservoir simulators. In this paper, two numerical examples for incorporating water oil rate data into geostatistical models are given to prove the efficiency of the proposed algorithm.
Optimization of Multivariate Production-Injection System for Water-Alternating-Gas Miscible Flooding in Pubei Oil Field
Authors: Yang Daoyong , Zhang Qi , Cui Huanwen , Feng Hu , Li Luhua 
Published: December 2007

Abstract
The first Water-Alternating-Gas (WAG) miscible flooding project, Pubei oil field in Xinjiang, was put into production and scheduled to initially inject miscible gas as well as water at the early development stage. With consideration the specialty of the WAG process, optimization of multivariate production-injection system (PIS) is the Gordian knot of improving the reservoir benefit as well as extending the reservoir life. In general, the production history of a reservoir can be predicted by integrating a reservoir model, and a production model including a wellbore model and a choke model. Changes in any production and/or injection parameter will cause changes in the predicted production and/or injection history.
Well-to-well tracer results were used to modify the reservoir model and evaluate efficiency of WAG during the field development, and novel integrated concepts and methods were proposed to couple the reservoir model with well model including both injectors and producers. The genetic algorithm is shown to be both stable and efficient when used to optimize the multivariate PIS with different constraints. It is shown from field applications that reasonable measures can be adopted for globally optimizing production and injection at the any stage of the field life, and that parameters including bottomhole flowing pressure, reservoir pressure, injection pressure, oil rate, gas-oil ratio, water-cut, etc. were controlled and adjusted in an optimized range.
Using a 3D Stochastic GeoModel to Determine Optimal Infill Potential of a Mature Gas Field: A Case History
Authors: Herweijer J. C. , Barley M. , Chugh S. , Alexander S. , Smith M. , Kuppe F. 
Published: December 2007

Abstract
Discontinuous fluvial sands with highly variable permeability patterns pose a significant challenge for further development of mature onshore gas fields in South Australia. To obtain an optimal strategy for further infill drilling a multi-disciplinary reservoir characterization study was undertaken. This study combined all available data (petrophysics, geology, geophysics, and engineering) into a 3D stochastic geo-model before various upscaling methods could be considered for creating a reservoir simulation model. Coarse upscaling methods were used to match macro-scale reservoir characteristics (e.g. the effective permeability in the well's drainage area) while smaller scale heterogeneity (RFT pressure measurements) were matched using permeability predictors that preserved the observed variability from core data.
Several geological scenarios were designed for the model. These scenarios included various assumptions on sand content of the main producing horizon, sandbody dimensions, the permeability distribution, and continuity of coals acting as vertical baffles. During history matching, some of these scenarios were tested as alternatives in pursuit of a history match. Scenarios were refined/rejected and/or iterations made to re-assess the data. The history matching procedure revealed the significance of outlier permeability streaks as conduits to effectively drain reserves. The study was conducted under the constraints of a fairly tight operational schedule to meet a development drilling deadline. Drilling locations and the associated economic evaluations were based on simulated forecasts from a number of stochastic realizations/scenarios while connected volume calculations were made for a larger number of realizations.