bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deriving Capillary Pressure and Water Saturation from NMR Transversal Relaxation Times
Authors: Glorioso Juan Carlos , Aguirre Omar , Piotti Gabriel , Mengual Jean-François 
Published: December 2007

Abstract
Determination of water saturation (Sw) from conventional resistivity and porosity logs has proved difficult in several gas fields within Bolivia. To address this challenge, a method was developed to determine Sw profiles based on pseudo-capillary pressure curves (Pc) derived from transversal relaxation times (T2 distribution) measured by nuclear magnetic resonance (NMR) logging tools.
Some of the Bolivian sand reservoirs, producing gas and condensate with a high gas/oil ratio, are characterized by a lack of resistivity contrast above and below the oil-water contact. This problem is attributed to complex mineralogy, including thin shale laminations within sand bodies of variable petrophysical quality, and mostly to very fresh formation waters that average a salinity of 5000 ppm of total dissolved solids. Also, the lack of lateral extension of each reservoir makes cross-well correlation very difficult.
The core hypothesis of this original method is to assume that the relation between capillary pressure and pore throat sizes is similar to that between T2 values and pore-size distribution. A consistent scaling factor is used to derive a pseudo-capillary pressure from an NMR T2 distribution. After the pseudo-pressure is calibrated with capillary pressure measurements from laboratory-derived core data, it is combined with density (difference between the produced hydrocarbon and the formation water) and free-water level (FWL) information to compute Sw along the wellbore trajectory.
Even so, in general terms, resistivity-based models are still the most consistent and documented foundation in order to compute water saturation; Examples demonstrate the success of this new standalone method of uncovering unforeseen hydrocarbon in place and obtaining accurate Sw as an alternative to the standard, but dubious or inadequate, resistivity method in Bolivia where cretaceous and carboniferous rocks with intergranular porosity are found within several sedimentary basins.
A Method To Estimate Permeability on Uncored Wells Based on Well Logs and Core Data
Authors: Lacentre Pablo E. , Carrica Pablo M. 
Published: December 2007

Abstract
Reservoir description for simulation studies requires good knowledge of the permeabilities. Unfortunately, reliable permeability is only available from laboratory tests on cores, which are usually taken from a small percentage of the wells. Frequently, this information is extrapolated to calculate permeabilities all over the field, but the lack of enough data points usually causes unreliable predictions. We propose a method to estimate formation permeabilities from standard well logs and core data. The analysis includes a first step consisting of the interpretation of the petrophysics and a characterization in lithofacies, electrofacies and hydraulic flow units. This step involves the use of modern mathematical tools to rationally classify each reservoir region into a given (discrete) hydraulic flow unit. As a second step the core permeability data is mapped with the well log data using neural networks and the restrictions found on the first step of the analysis. This approach allows the use of continuous hydraulic flow unit values and reduces the error arising from the discrete zonation technique. Also, it overcomes the error coming from the mapping between log data and hydraulic flow units. The method should be applicable to any kind of reservoir as long as sufficient core and log data are available. The method assumes that the Carman-Kozeny equation holds for the reservoir rocks, which is a fairly reasonable assumption, and that the well logs available contain intrinsic information on tortuosity, sand size distribution, cementing characteristics, etc., which ultimately determine the flow performance of the rock. This hypothesis is usually strong because the available logs are not able to fully read the physical phenomena that cover the complex dynamics of the flow on the reservoir rocks. The method was tested using available core and log data in a sandstone formation in Chihuido de la Salina, Neuquen Basin, Argentina. Some core data points were not used to train the neural network and therefore useful for validation and comparison. In spite of the cited drawbacks, the method has shown to outperform both the standard regression techniques and the hydraulic flow units approach.
Monitoring Techniques for HP/HT Reservoirs: Furrial Field Case
Authors: Matamoros Valeria , Escobar Elena , Rodríguez Anaiza 
Published: December 2007

Abstract
The continuous monitoring of the main reservoir parameters is usually very important in capturing data, which are then used for reservoir characterization and recovery process evaluation in reservoir studies. This characterization is used to define the production strategy and oil recovery efficiency of the fields. In the case of High Pressure and High Temperature reservoirs, the reservoir monitoring becomes a challenge. The Furrial field, located in Northeastern Venezuela, is an example of a very deep, HP and HT reservoir. During the design and application of a WAG pilot project in this field, several monitoring techniques were considered. Of these, some monitoring techniques were selected and subsequently some of them were implemented in the pilot.
This paper presents some field results related to several monitoring techniques that have been applied during the different phases of the WAG pilot test in the Furrial field. The study considers conventional techniques such as chemical and radioactive tracers, and saturation, temperature, pressure and production logs. Also this study examines unconventional techniques such as natural tracers, pressure and temperature downhole gauges. Finally, the study investigates, new approaches for monitoring such as saturation downhole permanent gauges, post-mortem cores and crosswell seismic. All the techniques were analyzed and compared, considering the reservoir characteristics, application feasibility, market availability, time of response and costs, to select the most suitable techniques for this type of reservoir. The results from the Furrial field case show that even though permanently mounted downhole gauges seem to be the most appropriate way to capture reservoir data for a mechanistic pilot, they are not totally reliable, so far, for HP and HT reservoirs.
The Cruse ‘E’ Expansion Steamflood: Technical, Economic and Environmental Perspectives
Authors: Ramlal V. 
Published: December 2007

Abstract
Based on the success of the Cruse ‘E’ Pilot steamflood, Petrotrin decided to venture into a large-scale project of a similar nature called the Cruse ‘E’ (IADB) Expansion Steamflood. The project area consisted of 270 acres, with an estimated original oil in place of 31.1 million barrels in the zone of interest, the Upper Cruse ‘E’ sand. Surface and infrastructure work began in January 1994, which was followed by rig work - drilling, recompletions, and workovers. Sixty (60) new wells comprising twnty-eight (28) injectors and thirty-two (32) offtakes were drilled and completed to form twenty-eight (28) patterns. Also thirty-five (35) existing wells were utilized as offtakes. The project was commissioned in January 1996 when steam injection began. This brought the number of active steamfloods and WASP projects at Petrotrin to eight (8). It was predicted by reservoir simulation that 11 million barrels of heavy oil would be recovered over fifteen (15) years with production peaking in the year 2000.
However, in 1998 when oil production reached 877 bopd, the project was adversely affected by environmental concerns to a residential area in the vicinity of the steamflood and it was actually shutdown by order of the regulatory body in November 1998. Extensive environmental work was undertaken in the areas of communication, training and operations to improve the safety and environmental aspects of the steamflood, and ensure that it was brought up to the environmental standards required. After forty (40) months of inactivity, approval was finally obtained in March 2002 from the regulatory body to restart steam injection.
This paper discusses the performance of the steamflood during steam injection and during no injection, the technical, operational and economic aspects of the project, and the environmental upgrade conducted.. The paper also discusses the restarting exercise conducted for steam injection and presents future operating strategies.
A Closed Form Hydraulics Equation for Aerated Mud Drilling in Inclined Wells
Authors: Guo Boyun , Sun Kai , Ghalambor Ali 
Published: December 2007

AbstractAccurate prediction of shut-in and flowing bottom hole pressures in inclined holes presents a challenge in aerated mud drilling. It is highly desirable to develop a simple and accurate hydraulics equation for this purpose. This paper fills the gap.A closed form hydraulics equation was developed in this study on the basis of recent experiments on multiphase flow in an inclined well model. The newly developed hydraulics equation is a 4-phase model considering injected liquid, injected gas, formation fluid influx, and cuttings entrained at bottom hole during drilling.The equation was first calibrated using data measured from a full-scale research borehole. It was then tested with two field cases covering a deep (9831 ft) vertical well and a shallow (697 ft vertical depth) horizontal well drilled with aerated muds. The results show 8.66% and 0.81% error of the equation in bottomhole pressure prediction for the deep and shallow well, respectively. The equation was also compared with two commercial software packages (S1 and S2) using measured bottombhole pressure from another well. It indicates that the flowing bottomhole pressure calculated by the equation is comparable to that by S1 and much more accurate than that by S2. Sensitivity analyses with the equation show that gas injection rate affects "static" pressure more than flowing pressure in the annular space in the tested data range. The new model indicates very high Equivalent Circulating Density (ECD) and low Equivalent Mud Weight (EMW) in shallow depth near surface. ECD and EMW versus depth in a 6.37"×3.5" annulus was generated for field applications.
Case Study: Field Application of a Novel High-Density Fluid-Loss Pill
Authors: Messler D. , Richey J. , Powell J. , Miller D. , Guidry J. 
Published: December 2007

Abstract
As part of a post-fracture stimulation fluid-loss contingency plan for a sub-salt completion, a pill was required that exhibited the following characteristics: thermal integrity above 200°F for a minimum of four days in a zinc-based brine, stable rheologies that promoted the suspension of bridging particles, and pill removal with well production alone.
Obtaining desired viscosifier yield and stability in zinc bromide has proved challenging, particularly at temperatures above 200°F.1 There was no "on-the shelf" solution for these requirements. Studies aimed at maximizing pill effectiveness while minimizing the potential to impair completion productivity were initiated. These studies focused on incorporating novel additives that yielded stable rheology at anticipated temperatures and promoted the easy lift-off of the residual filter cake. The bridging particles were optimally sized to minimize total solids loading and to promote an efficient and quick seal on the screen drainage layer.
Historically, these fluid-loss pills have been sized solids in a polymer fluid base.2–3 Concerns about the easy removal of these pills through flow back or acid clean-up was a major focus in evaluating the success of the various formulations studied. The result of these studies was a pill that formed a thin filter cake in the test cell. It exhibited both low spurt loss and minimal accumulated filtrate over the 96-hour test period. It was still active when the test was stopped for time. Flow-back tests indicated a lift-off pressure of less than one psi.
The successful implementation of this contingency pill when the mechanical fluid-loss device failed resulted in HSE benefits, cost savings, and prevention of damage to the reservoir. This paper will document the pill design, field application, and the outstanding production results obtained (currently producing 65 mm cu/ft/day).
Finding New Limits with Horizontal Wells in a Thin Oil Column in the Mahogany Gas Field, Offshore Trinidad
Authors: Mackow H. Michael , Milliken Mike , Trujillo Jorge , Stephen Andy 
Published: December 2007

Abstract
Horizontal oil well drilling, completion and production techniques have continued to advance through the continued Mahogany field development by bp in Trinidad. The Mahogany field was initially developed to supply gas to Train 1 of the Atlantic LNG plant in Trinidad. The 21 Sand reservoir in this field is contained in two fault blocks having 60 and 72 foot oil columns respectively. The fault block V oil column was developed first and is overlain by a 300 bcf gas cap and underlain by water. The fault block IV oil column has been developed recently during the phase 2 Mahogany field development and has a 45 bscf gas cap.
As with other fields in Trinidad that have thin oil columns horizontal well technology has been the preferred technology for developing the 21 sand oil leg. During the first phase of drilling the wells were generally around 2000 to 2500 feet and gravel packed. The final well of the Phase 1 program has sand control screens but was not gravel packed and turned out to be the most productive well of the phase 1 program. The well has produced sand free even after water breakthrough.
The design of the phase 2 wells was modified after running a wireline tractor PLT on the MB04 well. The PLT showed that the entire length of lateral was contributing to production even with very low drawdown. The PLT and continued success using a rotary steerable drilling system led to design changes for the phase 2 wells. The wells are now drilled very flat and as long as possible. Results from this approach have resulted in the drilling of the longest horizontal well in Trinidad (MB14). Two of the other Phase2 wells drilled in Mahogany have become the second and third longest wells. The phase 2 wells are performing above expectations and have significantly reduced the development costs of the 21 sand thin oil rim.
String Design and Application in Through-Tubing Rotary Drilling (TTRD)
Authors: Reynolds Harris , Watson Gregor 
Published: December 2007

AbstractThrough-Tubing Rotary Drilling (TTRD) is a slim-hole sidetracking technique successfully employed from North Sea platforms to economically access marginal targets in mature fields from existing wellbores. TTRD typically uses 2-7/8" standard production tubing with high-torque threaded connections, run from the standard platform drilling rig, to drill-out through the existing completion via whipstock.TTRD sidetracks in the North Sea have been less than 3500 feet in length, and completed with 2-7/8" or 3-1/2" flush-jointed liners. As a contingency, the 2-7/8" drillstring can be cemented in place as a liner.Since (1) TTRD does not require the mobilization of specialized equipment, and (2) the drillstring may be rotated to reduce differential sticking and improve cuttings returns, and (3) the drillstring will tolerate high overpulls, TTRD has proven consistently more economical than Coiled Tubing Drilling (CTD) in similar applications.The objective of this paper is to review and discuss string design and applications issues for Through-Tubing Rotary Drilling. Topics will include:Drill-Floor Handling Issues Drilling Torque and Over-Torque Downhole OD Wear of Tubing Upsets Fluid Dynamics, especially Equivalent Circulating Density (ECD) Issues Hole Cleaning Fatigue Life Estimation Repeated Make & Breaks with Production Tubing Subsequent Use of the Drill String as Production Tubing Cementing and Completions
Integrated Approach to Completion Design Results in Major Producers in Trinidad: The Hibiscus Project
Authors: Hylkema H. , Guzman J. , Green T. , Gonzales G. 
Published: December 2007

Abstract
This paper describes the integrated approach adopted to optimize the gravel pack completion design and fluid selection for the North Coast Marine Area (NCMA) development project, offshore Trinidad. This resulted in the development of a uniquely engineered gravel pack completion design and associated procedures, incorporating a number of novel fluid-related and equipment technologies. Key challenges to the project were: wellbore stability, due to narrow mud weight windows and shale reactivity; effective sand control; productivity; and minimal rig space, leading to an ‘intervention less completion design' philosophy, and an accelerated project schedule. These challenges are interdependent and rely heavily on fluid selection and optimization, not only for drilling operations but also for gravel packing and clean-up operations.
Through effective tendering and subsequent teamwork, the completion design has resulted in high productivities and cost savings amounting to some US$ 5.5 million.
Effect of Depletion Rate on Performance of Solution Gas Drive in Heavy Oil Systems
Authors: Maini Brij B. 
Published: December 2007

Abstract
Foamy oil flow appears to be an important contributing mechanism in the better than expected performance of solution gas drives in many Canadian and Venezuelan heavy oil reservoirs. The foamy flow occurs when the gas released from solution during depletion is able to flow through the sand while remaining dispersed in the oil. In laboratory depletion tests, it occurs when a high enough rate of pressure decline is used. With low rates of pressure decline, the depletion appears to occur by the classical two-phase flow mechanism and results in a low recovery factor.
Two types of laboratory depletion experiments were carried out to further examine the conditions needed for initiating foamy flow. First, a series of depletion tests was completed at different rate of pressure depletion to establish the relationship between the rate and the recovery factor. In the second type of experiments, the depletion was started at a low rate and continued to different depletion levels before increasing the depletion rate to a much higher value.
The results show that in tests done at a constant rate of depletion the recovery factor decreases with the decreasing rate of pressure depletion. In the second type of test involving slow depletion followed by fast rate of pressure decline, the recovery factor depends strongly on the pressure level to which the slow depletion was continued. If the slow depletion was continued to level that resulted in the establishment of continuous gas saturation, the subsequent fast rate of depletion was ineffective in providing a high recovery factor. However, when the depletion rate was increased before the average gas saturation in the sand-pack exceeded the critical gas saturation, the recovery factor was much higher and comparable to the tests involving high rate of depletion from the beginning.
These results tend to strongly suggest that the high recovery factor obtained in fast depletion tests is not related to events that take place during the initial phase of depletion, i.e. during the nucleation and initial growth of gas bubbles. It is what happens at the point when the gas phase is ready to become continuous that controls the depletion performance. A plausible explanation is that when the pressure gradient becomes high enough to mobilize the bubbles before they coalesce into a continuous gas phase, the formation of continuous gas phase is delayed. This keeps the gas mobility low and improves the recovery performance.
Competency Systems - A Task Based Learning and Development Method
Authors: Abder Carlton H. , Thomas Bruce D. 
Published: December 2007

Abstract
This paper is based on the field application of competency systems within an oilfield service company. It defines competency systems, reviews and summarizes literature on Competency Systems, and demonstrates the shift from traditional classroom training to a competency based approach within the service sector of the petroleum industry.
The paper defines the need for knowledge, skills, behaviors, and experience necessary for an individual to achieve competence and explains the method by which people can achieve competence.
The paper also discusses the five essential elements and the advantages and limitations of a competency based training and development system.
Horizontal Production Logging using Tractor Technology- a first for Trinidad
Authors: Allahar Ian A. , Krieger K. 
Published: December 2007

Abstract
Many horizontal wells have been drilled off the East Coast of Trinidad to maximize hydrocarbon production and ultimate recoveries in thin oil rim reservoirs. Surveillance data in the horizontal wells provides valuable reservoir depletion information and helps shape future well designs. The long, high angle and horizontal well trajectories prohibit the use of conventional surveillance techniques such as production logging tools (PLT) conveyed on electric wire line. To overcome the deviation challenge PLT tools are deployed using coil tubing, this however poses both an economic strain and affects the production profile due to the restriction on flow imposed by the coil tubing diameter. A new technology, the wire line tractor, allows the operator logging access into any hole angle at lower cost with a reduced imposed tool restriction resulting in higher quality data.
Mahogany MB04 was the first horizontal well logged using the Tractor technology in Trinidad. The logging results provided proof of hydrocarbon contribution along the entire 1743' lateral, confirming the value of drilling longer horizontal wells. Assurance gained from the PLT survey supplemented the technical justification for drilling the longest horizontal well in Trinidad with a peak clean up production rate of 10,000 stock tank bopd.
Design of Glycol Unit for Maximum Efficiency in Gachsaran Oil Field
Authors: Bahadori Alireza 
Published: December 2007

Abstract
In designing dehydration units for natural gas, several critical parameters exist which can be varied to achieve a specified dew point depression. This paper studies the effects of varying the glycol flow rate, number of stages in the contactor,. The presence of heavy ends (C7+).
Water and hydrocarbons are natural companions. Hydrocarbons are formed in water environment and are in equilibrium with water. The water content of a gas depends on system pressure and temperature and the composition of the water containig gas. The presence of heavy ends (C7+) effects the water capacity of gas. In this study the effects of glycol circulation rate, glycol concentration and C7+ mol fraction are evaluated in a dehydration system.
This paper presents optimization of dehydration units. The results provide an analysis of the dehydration effectiveness at a variety of common operating variables for a typical dehydration facility. Next, the effect of c7+ in the plant feed will be presented.