bluuebunny/crossref_metadata_2025 huggingface dataset:
A Closed Form Hydraulics Equation for Aerated Mud Drilling in Inclined Wells
Authors: Guo Boyun , Sun Kai , Ghalambor Ali
Published: December 2007

Accurate 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

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

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

Through-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

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

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

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

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

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.
Downhole Oil Water Separation (DOWS) Systems in High-Volume/High HP Application
Authors: Bangash Yasser K. , Reyna Marcello
Published: December 2007

Downhole oil water separation (DOWS) technology has been in the industry since the early 1990's. This technique, offers both economical and environmental benefits to producers. Despite these advantages, only a limited number of these systems has been installed worldwide. There is a consensus in the industry, on the advantages this technology has to offer. On the other hand, very few operators are willing to deploy this technology due to reliability issues associated with these systems. Based on the author's experiences, the two outstanding factors that are contributing to this perception are: Complicated system designMisapplication of the technology

The intent of this paper is to discuss several reasons that are limiting the applications of these systems and also offer solutions to these problems. One such solution is a newly developed Encapsulated DOWS System. This new system and its the implementation in La-Victoria Field will be addressed in detail.
Oilfield Scaling – Part I: Mathematical and Laboratory Modelling
Authors: Bedrikovetsky P. G. , Lopes R. P. , Rosário F. F. , Bezerra M. C. , Lima E. A.
Published: December 2007

The BaSO4 scaling is a chronicle disaster in waterflood projects with incompatible injected and formation waters. This is usually due to precipitation of barium sulphate from the mixture of both waters and consequent permeability reduction. The effect of porous media on the BaSO4 scaling kinetics is studied.

A new methodology for determination of kinetic constant from coreflood tests consists of the sequence of diffusivity tests, of transient tests with chemical reaction, and of steady state tests on simultaneous injection of both injected and formation waters. The diffusion coefficient versus flow velocity is found from the diffusivity tests. Steady state tests allow determination of chemical reaction rate constant versus velocity. The transient test data as compared with the mathematical modelling data validates the results of steady state tests treatment.

The test data are treated using semi-analytical and numerical models.

The main result of the work is the proportionality between the chemical reaction constant and flow velocity in the range studied.
Overcoming The Previous Limitations Of Variable Speed Drives On Submersible Pump Applications
Authors: Breit S. , Sikora K. , Akerson J.
Published: December 2007

There is an ever-increasing use of variable speed drives in submersible pump applications. However as with all new applications new problems can be encountered. The long cable lengths associated with submersible pump equipment have limited the effectiveness of variable speed drives. Many drives have to use external filters, inductors and conditioners to keep from damaging the cable and motor. The extra costs associated with this equipment, as well as the custom use, limit the overall effectiveness. VSG (Variable Sine-wave Generation) technology has been developed to overcome these limitations, as well as providing the user all the flexibility that initially attracted them to Variable Speed Drives.
The Brazilian Oil and Gas Conformity Assessment Program - Part II: Two Years Later
Authors: da Silva G. R. , Sala J. F. , Freire A. F.
Published: December 2007

Interesting aspects and products of the program are presented. The program, that was presented in the paper SPE 69468 (VII LACPEC), is now in the middle of its development. Brazilian oil and gas industry data and also the regulatory strategy for the facilities' operational safety are updated. Focus is given in the principal obstacles and in the most important conquests of a innovative and complex project, specially considering its "multiple interfaces" characteristics. Finally, it is presented, the revised planning for development and implantation of the Program, including its stages, in an outlined 5W + 2H method (WHAT - WHY - WHO - WHERE - WHEN - HOW and HOW MUCH).
Dynamic Analysis of Stabilized Drilling Strings Performance in Low-Dip Wells
Authors: Fernández M. A. , Inciarte G. , Ramones R. , Romero J. L. , Bello A.
Published: December 2007

This paper describes the field evaluation of drilling strings with different stabilizing configurations, so that minimizes bit vibration problems in the bottomhole assemblies (BHA), contributing to optimize the performance. The studio was made for Lagotreco field, Block III in Maracaibo Lake. The evaluation is supported with simulation results obtained with drilling computer applications.

The use of BHA designs with the criteria of stabilization "30- 60ft" (stabilizers placed to 30ft and 60ft from bit, respectively), generally used in western PDVSA operational areas, to control straight holes and displacements; cause premature damages at the bits, such as broken cutters, chipped cutters, lost cutters and ring outs. These dull characteristics are potential signs of lateral vibration, increasing drilling costs because of additional bit trips.

A dynamic analysis study of three different stabilizing configurations for BHA (30 - 60ft, 15-45ft and 0-30ft), show the values rank for critical rpm speed, side forces and displacements measured from bit, for every case.

The field test evaluation shows the reduction of bit damages by vibration effects, with a BHA stabilized 15′-45′; so that the decreasing of drilling time in terms of costs per feet (CPF). The study also includes an unconfined compressive strength formation analysis from the study area (USC).
Predicting Transition to Turbulence in Well Construction Flows
Authors: Frigaard I. A. , Nouar C.
Published: December 2007

Two classical geometries for wellbore hydraulics are the pipe and the plane channel, (often approximating an annulus). The technical literature is full of semi-empirical methodologies for computing frictional pressure losses and flow regimes in these geometries and there is much confusion about both the validity and physical basis of many of these phenomenological criteria.

In this paper we examine phenomenological criteria for transition, in the context of newly derived theoretical results on stability of these flows. We examine five transitional criteria commonly used in the petroleum industry and are able to rigorously demonstrate that only one of the five criteria can possibly be correct over the full range of Bingham numbers. We then examine a more limited, but relevant, range of Bingham numbers and show that enormous discrepancies exist between these criteria. We conclude by discussing implications for current practice.
A Fast Method for Computing Tracer Flow in Oil Reservoirs
Authors: Guevara-Jordan J. M.
Published: December 2007

This paper describes a new and fast numerical scheme for computing tracer flow in oil reservoirs. It combines the f undamental s olution m ethod (FSM) and the s treamline a pproach (SA) to obtain a very efficient algorithm. The FSM is based on the method of images and the singular value decomposition technique to compute the pressure and velocity fields. The SA uses the time of flight notion along the streamlines to obtain very accurate tracer concentration. Applications of the new scheme to a quarter five spot, arbitrary shaped and multiple wells reservoir problems show that it is faster than boundary and finite element methods.
Using Geographical Information System (GIS) Technology in State Owned Company
Authors: Jaggernauth Deonarine D. J.
Published: December 2007

Petrotrin, a state owned company has production operations which span the whole of south Trinidad. The company has numerous wells, the miles of gas and oil lines, and the passage of these lines through agricultural areas, towns and villages are a major environmental concern to the company. Many of these installations were inherited from predecessor companies.

Geographical Information System (GIS) technology is only about twenty years, and its usefulness over the years has shown that it is a cost saving to the company. Groups monitoring GIS has concluded that it is a billion dollar industry if one were to add the value of the software, hardware and services. Other computer software packages are not as beneficial as GIS. In GIS the storage of data is independent of the mode of presentation4.

GIS can provide the following information needed for management to make the right decisions: ∼identify all areas within 100 feet of the wells∼identify all watercourses within 100 feet of installations∼identify all buildings, agricultural lands that are within 100 feet of the gas and crude oil pipelines among others.

Several departments within Petrotrin can look at the same data simultaneously because GIS allows that flexibility. Previously, in using paper maps only one person can look at the information since there were not several copies of these maps circulating. If these maps had to be updated it took a long time. Now with the GIS software and hardware packages more than one person can look at the same data and make faster decisions. The report presented herein conveys the benefits of using GIS in environmental decisions in Petrotrin's production operations.
Proven Performance Improvements in Well Intervention through Outsourcing and Continous Learning Systems
Authors: Joseph Kevin P.
Published: December 2007

A Marine Oilfield operator, with over 800 offshore wells, has experienced significant performance improvements using continuous learning systems incorporated in their Workover management operations.

The Workover Management Department was outsourced seven years ago to Multinational Service Company together they created a system of benchmarking, Quality control and trend analysis to improve performance and cost effectiveness. Innovation and technology coupled with an international shared learning database resulted in significant reduction of down time, unscheduled events, completion skins, post workover production and workover costs all equating to improved overall profitability. The Workover management group operates within a flat structure, results-oriented culture, continuous learning systems, cross-cultural multi-disciplined staff, cutting-edge IT support systems, and a team based reward structure. The formula, presented in this report, can be introduced to almost any environment and can certainly positively impact low cost operators in the oil industry.
Assessing the Impact of Seismic Survey Operations on the Environment
Authors: Salter Edward , Walls Anne
Published: December 2007

The aim of the Seismic Survey Environmental Assessment Tool (SSEAT) is to reduce the risks to the environment from seismic surveys. It facilitates environmental impact assessment and the management of environmental sensitivities whilst designing and undertaking a seismic survey. It is both a ‘check-list’ guide and a sound propagation impact model. In the UK it guides the completion of an application to carryout a seismic survey, Petroleum Operations Notice (PON) 14A under the Offshore Petroleum Activities (Conservation of Habitats) Regulations 2001. SSEAT used properly ensures that the risks to the environment are understood simply and clearly by a survey team and enables the elimination of any that are adversely significant. The new tool allows BP to better understand the impact of seismic surveying and submit environmental information to the DTI, the UK Department of Trade and Industry, in a transparent and consistent manner. The Gausland model ‘received level = source level -transmission loss’ is used to model the behaviour of a seismic pulse, and to later help estimate the zones of effects for sounds using presented scientific literature thresholds - Zones of: 1) Audibility; 2) Response; and, 3) Hearing Loss, Discomfort and Injury. This is achieved by taking the sound levels that are known to induce a response to mammals and/or fish and recording the distance from the seismic source that the sound level occurs from the plotted sound decay curve. Whilst designed for use in the UK it can be used anywhere in the world to assess the environmental impact of seismic surveying. If so it will set a performance benchmark. Its use has also highlighted areas where improvements could be made. The outcome is an abbreviated summary of an ‘environmental impact assessment’ (EIA). It is similar in process to undertaking an Environmental Impact Assessment (EIA) under the UK Offshore Petroleum Production and Pipelines (Assessment of Environmental Effects) Regulations 1998, European Amended Environmental Assessment Directive 97/11/EC and World Bank EIA guidelines.
Strategies for Minimizing Produced Water Impacts in a Changing Regulatory Environment; A Trinidad and Tobago Experience
Authors: Sookdeo Nigel
Published: December 2007

Currently, produced water discharges are regulated in Trinidad and Tobago by a voluntary standard for liquid effluent developed by the Trinidad and Tobago Bureau of Standards (TTBS) in 1998. With the imminence of new and stringent legislation for effluent discharges under the Environmental Management Authority's Water Pollution Rules 2000, regulation of produced water will evolve from a voluntary compliance standard to that of mandatory compliance by law. In order to cope with the proposed legislative changes with regards to effluent discharges and a forecasted increase in produced water production, Trinmar, an offshore oil and gas operator in Trinidad and Tobago required new strategies for produced water management, since it is the single largest waste stream by volume within the entire operations of the company. The main strategy for produced water management was to upgrade the existing treatment system for process optimization/compliance with pending legislation and included; Upgrade of processes-primary and secondary oil/water separationDischarge of produced water from inland to coastal nearshoreEvaluation of the current produced water treatment system by conducting an engineering studyUpgrade of current produced water treatment system to ensure regulatory compliance.

The findings of the engineering study indicated that the current produced water treatment system at Trinmar is adequate to ensure water quality for compliance with existing standards that are voluntary and limited to specific parameters.

However, with the advent of the new regulations and a projected increase in produced water production by the company, the current system will not be adequate. The most feasible option for produced water management was found to be treatment on-land and disposal in a coastal nearshore or offshore environment to be achieved by upgrading the present produced water treatment system and by modifying the process. The results of the engineering study and proposed process changes are discussed in the subsequent sections of this paper.
Exporting Safety and Environmental Best Practices to Energy Frontiers: A Web-Based Solution
Authors: Thompson Archie R.
Published: December 2007

Ever growing worldwide demand for oil and natural gas production continues to geographically challenge an aging, experienced workforce. Worker safety and pollution control are largely dependent upon proper human behavior.

Most U.S. based operators integrate API, EPA and Coast Guard standards into their international operations. These standards can be complex and difficult to follow on the fly, and even more so in regions that lack an abundance of local experienced workers.

Increased reliance on intelligent tools to systematically capture knowledge and best practices for day-to-day operations is becoming the norm in the United States. By using the worldwide-web as the conduit, these best practices can be accessed and applied to both frontier as well as human resource-challenged theaters of operations.

The paper describes the development, implementation and capabilities of a proprietary Internet based safety and compliance system that is currently in use by owners/operators in the Gulf of Mexico. The system provides in a real time format for the continuous monitoring, verification and documentation of compliance with all U.S. federal codes and regulations for producing operations.

Continuous oversight of remote producing operations is afforded via the Internet. A real-time audit trail is electronically maintained in a format that permits 24/7/365 access without having to physically visit the remote sites.

Users in the field are systematically guided through the practical tasks required to maintain safe and environmentally friendly operations. Thus, the system can also be used as a continuing education and training tool for field personnel as well as for verification of on site training and skill levels.

Interested Parties. All parties involved in corporate HSE and Regulatory Compliance. All parties involved with keeping remote producing operations safe and environmentally friendly. All parties involved with training and verification of employee skill levels.
Simulations of Oil-Wet Membrane Wells for Water-Free Oil Production and Downhole Separation
Authors: Tweheyo Medad T. , Akervoll Idar , Holt Torleif , Torsæter Ole
Published: December 2007

The costs incurred in processing and disposal plus environmental concerns to minimise discharges during oil production have always created a desire to control unwanted fluid phases. In this paper, the potential of stopping the production of water by use of oil-wet selective membranes that allow oil flow and shuts off water has been studied. Water is an issue in the oil industry because it is a prime field abandonment criterion leaving trapped hydrocarbons behind.

The implementation of the membrane technology was verified through numerical simulations of different reservoir geometries. The simulations were performed on models where the water was either retained in the reservoir or where a water removal system was involved. During the simulations, the selective membrane was placed either on the production tubing or towards the reservoir rock wall.

Production profiles for the membrane wells have been compared to the production from conventional (base case) wells without the membrane. The results have shown that completing a production well with an oil-wet membrane shuts off water production as long as the water capillary entry pressure of the membrane is not exceeded. It was observed that the water block that accumulates in the annulus and near the well-bore area after water arrival at the well reduces the oil contact with the membrane and hence the flow of oil to the production tubing.

The simulation models other than the base cases have illustrated that the membrane well can act as a downhole separator. It was further observed that by optimising the design of removing the accumulated water from the annulus and proper timing to open the water removal facilities, it is possible to produce "water-free" oil at a total recovery efficiency as high as in conventional wells or better.
Simulation Study of CO2 Sequestration in a North Sea Formation
Authors: House N. J. , Faulder D. D. , Olson G. L. , Fanchi J. R.
Published: December 2007

Two similar Tertiary gas fields in the North Sea produce relatively rich gas condensate with a high proportion (4.5%-9%) of carbon dioxide (CO2) in the gas. The objective of this study was to evaluate the potential for CO2 sequestration in high permeability sandstone above the main reservoirs, estimate the ultimate storage capacity of the reservoir, and assess the risk of reservoir leakage. Only published data was used to create the hypothetical models discussed in this paper.

NOTE: A great deal of information is in the public domain on the CO2 sequestration project underway since 1998 in the Sleipner field area in the North Sea. What follows is an investigation of two different models: the first model is a model of a homogeneous sand with properties of the Utsira sand in the Sleipner area; and the second model is a hypothetical faulted anticlinal model with high vertical permeability to the fault. Both models use reservoir properties from the available literature of the Utsira sand reservoir and gas-water properties from the literature.
Rigless Water Shut-off Experience in Offshore Saudi Arabia
Authors: Al-Zubail Makki A. , Al-Nasser Redha H. , Al-Umran Saleh A. , Al-Saeed Saeed S.
Published: December 2007

As the offshore Saudi Arabia fields mature, more wells are becoming wet and consequently more wells are dying due to water encroachment. These dead wells and associated facilities are valuable assets that need to be effectively utilized throughout the producing life of the fields. Therefore, remedial actions to revive dead wells are vital strategies to maximize revenues. Rigless water shut-off techniques in conventional wells have been successful due to relatively simple wireline interventions. However, water shut-off jobs in horizontal wells are more complicated and are more challenging tasks for oil companies, including Saudi Aramco, due to their associated high cost and cement placement uncertainties.

This paper is a study of six years of rigless water shut-off efforts to revive dead wells in Saudi Aramco's Northern Area offshore fields to extend the producing life of the wells and enhance oil recovery. During the study period, 46 rigless water shut-off jobs were executed with a 91% success rate. Of the 46 water shut-off jobs, three jobs were successfully implemented on dead horizontal cased hole wells using coiled tubing (CT). The job success is attributed to proper problem diagnosis, job design and execution, resulting in a significant production gain and workover cost avoidance.
Water Production Management – PDO's Successful Application of Expandable Technology
Authors: Braas J. C. M. , Aihevba C. O. , Shandoodi M. , Van Noort R. H. , Baaijens M. N.
Published: December 2007

Water production management starts to play a more important role as reservoirs mature. Production logging is required to identify watered out intervals in producers and thief zones in injectors. The interpretation of logs acquired in horizontal, barefoot wells in highly fractured, heterogeneous, carbonate reservoirs is challenging at least. Yet this technique has been successfully applied in Petroleum Development Oman (PDO) in the Yibal and Al Huwaisah fields (Fig. 1) and has lead to significant production improvements after the subsequent water shut off.

Expandable Open Hole Clad (OHC) systems, with external seals, have been deployed to shut off water in both horizontal producers and injectors. The seal between the expanded pipe and the formation is further enhanced by elastomers with the ability to swell upon contact with formation fluids.

Case histories are presented to demonstrate the viability of this new technology.
Ranking and Upscaling of Geostatistical Reservoir Models Using Streamline Simulation: A Field Case Study
Authors: Ates Harun , Bahar Asnul , El-Abd Salem , Charfeddine Mohsen , Kelkar Mohan , Datta-Gupta Akhil
Published: December 2007

In this paper, we present a field example where a streamline simulator was used to rank multi-million cell geostatistical reservoir descriptions and to find the optimum level of vertical upscaling for finite-difference simulation. During geostatitstical reservoir characterization, it is a common practice to generate a large number of realizations of the reservoir model to assess the uncertainty in reservoir descriptions and performance predictions. However, only a small fraction of these models can be considered for comprehensive flow simulations because of the high computational costs. A viable alternative is to rank these multiple ‘plausible’ reservoir models based on an appropriate performance criterion that adequately reflects the interaction between heterogeneity and the reservoir flow mechanisms.

In this study, we explore the use of ranking based on streamline time of flight connectivity derived from a streamline simulator. The time of flight reflects fluid front propagation at various times and its connectivity at a given time provides us with a direct measure of volumetric sweep efficiency for arbitrary heterogeneity and well configuration. The volumetric sweep efficiency is the simplest measure that reflects the interaction between heterogeneity and the flow field. It is a dynamic measure that can be easily updated to account for changing injection/production conditions. We show that the proposed connectivity criterion can also be used to evaluate the effects of vertical upscaling in the dynamic performance and to determine the optimal level of upscaling for numerical simulation purposes.

Our field study involves a Middle Eastern carbonate reservoir under a moderate to strong aquifer influx. The reservoir is on primary depletion and has no injectors. Multiple geostatistical reservoir descriptions were generated using a hierarchical approach whereby the larger level of uncertainty is defined first followed by smaller levels. The aquifer is modeled with a constant pressure boundary and for each time update, the location of the boundary was modified to account for the water encroachment. Using the field-wide sweep efficiency as a performance measure, the realizations were ranked, and used for flow simulation to assess risks associated with various development strategies. Subsequently, three selected realizations were upscaled for the purpose of comprehensive history matching and performance prediction.
Improvements in Dynamic Modeling of Underbalanced Drilling
Authors: Fjelde Kjell K. , Rommetveit Rolv , Merlo Antonino , Lage Antonio C. V. M
Published: December 2007

The present work discusses some improvements that have been introduced in a dynamic model, which was developed for simulating the two-phase flow transient phenomena associated with underbalanced drilling operations. The model enhancements are basically obtained by implementing mechanistic closure relationships and more accurate numerical schemes. This process of improvement is validated through comparison to full-scale experimental data in transient scenarios, showing that the gains in terms of increasing the model accuracy are significant.
Little Known Lubrication Method: Great Tool for UB Work
Authors: Nance Gary W.
Published: December 2007

Underbalanced drilling is defined as drilling with the hydrostatic pressure of the fluid intentionally less than that of the formation pore pressure. The IADC classifies UBD wells according to the drilling fluid used to achieve underbalanced conditions.
3D Modeling using Multiple Scenarios and Realizations for Pre – Reservoir Simulation Screening
Authors: Scheepens C. C. J.
Published: December 2007

Understanding and managing subsurface risk is becoming an increasingly important business driver for oil companies. The ability to generate, manage and rank multiple models of a reservoir will allow for better economic forecasting, particularly at early project stages.

3D geological modeling is becoming a standard work process in many oil companies. Properly utilizing multiple scenarios and realizations for risk analysis, however, is a technique that requires a more sophisticated work process. Two main themes are discussed. First: how to frame the problem to generate reasonable model trees that will contain multiple stochastic realizations. Second: how to perform model ranking and select a small number of models for further investigation and analysis.

This is an evolving workflow in many companies. In this presentation we provide some ideas and guidelines for streamlining and focusing the work to the desired goal.
Competitive Impact of New Canadian Reserve Guidelines
Authors: Etherington John R. , Chan Phillip
Published: December 2007

The Canadian Securities Administrators (CSA) has proposed new guidelines governing the annual reporting of oil and gas reserves for Canadian companies. The guidelines require disclosure of both Proved and Probable reserves and associated value; inclusion of Possible reserves information is optional.

Reserve disclosures are key criteria to establish relative company stock value. It is thus instructive to compare the CSA regulations to existing U.S. Securities and Exchange Commission (SEC) rules and further to guidelines endorsed by the Society of Petroleum Engineers (SPE).

The CSA mandates disclosure of Proved volumes and associated future net revenues using two economic criteria: a forecast cost and prices scenario ("forecast case") and a constant cost and prices sensitivity scenario ("flat case"). The SEC Proved reserve is comparable to the "flat case" Proved reserve quantities in most instances. The CSA guidelines for Probable and Possible reserves conform closely to the current SPE published criteria. While recognizing probabilistic reserve assessments, the CSA has adopted the SPE guidance that reserves should not be aggregated beyond the "field" level using probabilistic summations.

The CSA may allow so-called "cross-border issuers", those Canadian companies also listed on USA stock exchanges, the option to solely follow SEC constraints. SEC regulations specifically prohibit disclosure of Probable and Possible reserves in 10K filings but many U.S. companies refer to additional resource potential in "forward looking statements" in their annual reports. Canadian "cross-border issuers" may not have similar latitude.

Unique to the Canadian regulations are rules regarding establishment of an internal company reserves committee and use of a qualified independent evaluator to audit assessment procedures and assets.

Will the new CSA rules improve, or impair, the ability of Canadian companies to compete for investment dollars? Further, the Sarbanes-Oxley Act on CEO/CFO certification requirements may have some unique implications for Canadian oil and gas companies.
OPEC Oil Production Strategy and Its Implication on Global Oil Market Stability
Authors: Iledare Omowumi O.
Published: December 2007

This paper applies statistical analysis to data describing the trends in OPEC oil production ceiling allocations from 1982-2001 The empirical analysis presupposes that a corporate decision framework guides OPEC production ceiling allocations subject to individual member characteristics and objectives. On average, and with a highly significant confidence interval, the empirical results indicate that the responsiveness of production quota to capacity, crude oil prices, reserves and other determinants are relatively small but inelastic. The empirical results also show the contemporaneous nature of each of OPEC's allocation criteria. This suggests that if OPEC really wants to accomplish a stable oil market, then each member nation must accept some joint responsibility and bear some equitable production reduction based on these criteria as and when necessary. Such an agreeable mechanism governing production ceiling allocations on the basis of concrete factors/criteria can significantly reduce the apparent lack of production discipline among members that has hitherto plagued OPEC1.
Rotating Jetting Nozzle Adds Value in the Cleanup of Horizontally Gravel Packed Well-Case Histories from Sandstone Environment
Authors: Onwusiri Henry , Onwuzurike Chiji , Abiodun Afolabi , Uchendu Chike
Published: December 2007

A 360-degree rotating jetting tool has been successfully deployed to cleanup about 1000 ft of 6.25" horizontal open-hole gravel packed (OHGP) well. The exercise was carried out using Nitrified 10% HCl placed from the toe to the heel at Coil Tubing average rate of 20 ft/min. Three passes were made at total fluids rate of 1.0 bpm. During the fluid placement, no losses were encountered. After the treatment and initial production testing, a baseline memory production log (MPLT) was acquired across the horizontal drain section to evaluate the completion/cleanup efficiency. The MPLT results indicated a better drain hole cleanup as seen in the inflow profile of the completed drain section. Higher contribution was also noticeable in the cleaner sand members. From the result obtained, the 360-degree rotating jetting tool can be efficiently applied to cleanup drain holes especially in horizontal wells equipped with gravel packs.