bluuebunny/crossref_metadata_2025 huggingface dataset:
Restoring Injectivity of Wells Drilled in Sour Carbonate Formations
Authors: Nasr-El-Din H. A. , Zabihi M. , Al-Dossary K. , Djelliout M. A. , Kelkar S. K.
Published: December 2007

Saudi Aramco has embarked on developing an oil field located in the Northern area of Saudi Arabia. This field is characterized by the presence of tar-mat zones that are present at the base of oil-column. These zones form a barrier which physically isolates the producing zones and the injection water. This paper addresses the challenges faced in maintaining the injectivity of water in this particular field.

Open-hole water injectors with extended reach (ER) were completed horizontally at the bottom of the producing zones and just-above the tar-mat zones. The typical open-hole lengths in these wells are between 3,000 –7,000 ft. Challenges were faced in drilling these wells in a populated area in the northern area of Saudi Arabia and being stratified, tar-mat was encountered in the open-hole sections of these wells. Tar content varies inconsistently around these injectors. This limits the injection rate of these injectors initially to as low as 600 BWD at 2,400 psig.

The low-injectivity of these water injectors is attributed to the damage induced by the drilling mud (water-based mud) and the presence of tar and asphaltenes in the injection zone. Acid stimulation treatments of these wells were needed to reach the target injection rates. Furthermore, this particular northern field in Saudi Arabia is sour and located inside a highly populated area and as such, environmental regulations prohibit any well flow back post acid treatment and no flaring is allowed.

To overcome these challenges a tailored acid treatment was designed. It included a preflush of an aromatic solvent, then stages of 20 wt% HCl regular and emulsified acids. To achieve better acid diversion in horizontal wells, stages of a surfactant-based acid system were utilized. Along with tailored acid treatments, new methods to place the acid in the zone of interest were also employed. More than 20 extended reach horizontal injectors were successfully stimulated in a sour carbonate oil reservoir. Pre and post treatment injectivity tests were performed using down-hole gauges in order to evaluate the efficiency of the acid treatments. This paper will discuss challenges faced during stimulation of water injectors in this sour heterogeneous reservoir, fluid selection, design criteria, field treatments, lessons learned, and results of the acid treatments.
The Challenges of Accident Response Training and Application in a Middle East Environment
Authors: Williams J. M. , Allan H.
Published: December 2007

This paper describes the development of, and challenges in the implementation of accident response training schemes and their results both for employees and students. Key issues relating compatibility with a Middle Eastern environment are discussed.

It is not believed emergency training issues have been addressed in this way previously. The study demonstrates that successful transfer of health, safety, and environmental (HSE) practices between countries or regions must accommodate local culture and traditions. Recommendations and suggestiuons are made that can be used by other organizations.
Analysis of Time-Dependent Wellbore Stability of Underbalanced Wells Using a Fully Coupled Poroelastic Model
Authors: Hodge M. , Valencia K. L. , Chen Z. , Rahman S. S.
Published: December 2007

Coupled poroelastic response of formation around wellbore is expected to differ from the classic linear elastic theory when subject to changes in the state of stress. This may lead to redistribution of stress and pore pressure around the wellbore and consequent time-dependant wellbore deformation. These effects could cause delayed wellbore failure, loss of circulation and even the total loss of the well, especially in the case of underbalanced drilling. This paper presents a fully coupled poroelastic model developed for wellbore stability analysis with particular emphasis on fluid flow induced stress changes around wellbore. By using finite element methods, the model is able to simultaneously compute the geomechanical and hydraulic variables.

In analogy with the common approach of wellbore stability analysis through initial and infinite time stresses calculation, the model can evaluate transient stress and pressure profiles to demonstrate the behavior of a wellbore throughout its history. This allows us to widen the safety mud weight window which leads to reduced drilling time and costs. The time of failure can be predicted by using modified Mohr-Coulomb criteria for breakout failure and tensile failure criteria for fracture. Thus, the coupled poroelastic approach can examine the factors influencing the wellbore stability more accurately than linear elastic method.

The model was used to analyse wellbore stability in different formation types, stress conditions and drilling situations. Time-dependent shear stress distributions are presented so that they can be compared with shear strength of these rocks at different depths to select appropriate mud weights for underbalanced drilling.
The Timing of Investment in Deepwater Heavy-Oil Opportunities With Uncertainty in Oil Price and Production Technology
Authors: de Abreu C. A. Camargo , Lima G. A. Costa , Suslick S. B.
Published: December 2007

Many offshore heavy oil discoveries in deep waters can be considered valuable assets if new technologies are available to transform geological successes into economic successes through projects of development and production. But, there are some latent questions: i) how to forecast future technology advances in order to produce this heavy hydrocarbon?; ii) how companies can estimate development cost for the next five to ten years?; iii) with which degree of certainty will new technologies be available to reduce present production costs for these oil types? This paper proposes the application of the theory of option pricing for valuation and decision-making in opportunities to invest in projects to produce heavy oil in a deep water environment. The first uncertain variable is oil price, which evolves over time as a Geometric Brownian Motion. The second uncertain variable is the impact of advances of production technology on production cost that evolves as a Poisson process. The assumptions in oil price modeling are based on continuous fluctuations over time. In case of production technology, we assume that advances take place in a discrete way through jumps that can represent gains, which may enable the firm to produce with greater efficiency reducing costs. This timing model is applied for valuation and decision-making of a typical heavy-oil project located in Campos basin in Brazil (15 °API, 2900 m water-depth). This production includes 7 production and 7 injection wells. Preliminary results show that the investment-rule is far from that of traditional NPV (that is, invest as long as NPV>0), especially in case of increasing oil pricing volatility and size and arrival of technological innovations.
Meeting the Environmental Challange: A New Acid Corrosion Inhibitor for the Norwegian Sector of the North Sea
Authors: Vorderbruggen M. , Kaarigstad H.
Published: December 2007

The rigorous environmental regulations of the North Sea oil and gas fields have required fundamental changes in the way service companies acidize wells. Traditionally, acid corrosion inhibitors have been some of the most toxic chemicals routinely pumped downhole. This paper describes a new acid corrosion inhibitor (NSACI) that meets the Norwegian environmental "Yellow" specifications for chemicals. This inhibitor functions in both mineral and organic acids and has been successfully used in the larger fields on the Norwegian Continental Shelf. Laboratory data is presented in detail along with field references to explain both the strengths and limitations of this new, environmentally-friendly acid corrosion inhibitor.
Robust Waterflooding Optimization of Multiple Geological Scenarios
Authors: van Essen G. M. , Zandvliet M. J. , Van den Hof P. M. J. , Bosgra O. H. , Jansen J. D.
Published: December 2007

Dynamic optimization of waterflooding using optimal control theory has a significant potential to increase ultimate recovery, as has been shown in various studies. However, optimal control strategies often lack robustness to geological uncertainties. We present an approach to reduce the impact of geological uncertainties in the field development phase known as a robust optimization (RO). RO uses a set of realizations that reflect the range of possible geological structures honoring the statistics of the geological uncertainties.

In our study we used 100 realizations of a 3-dimensional reservoir in a fluvial depositional environment with known main flow direction. We optimized the rates of the 8 injection and 4 production wells over the life of the reservoir, with the objective to maximize the average net present value (NPV). We used a gradient-based optimization method where the gradients are obtained with an adjoint formulation.

We compared the results of the RO procedure to two alternative approaches: a nominal optimization and a reactive control approach. The nominal optimization is based on a single realization, while in the reactive approach each production well is shut in when production is no longer profitable. The three control strategies were applied to each realization, from which the average NPV's and three cumulative distribution functions were determined. The RO results displayed a much smaller variance than the alternatives, indicating the increased robustness to geological uncertainty. Moreover, the RO procedure significantly improved the average NPV, compared to the alternative methods: on average 9% higher than using reactive control and 3% higher than for the nominal case.
Interfacial Tension Data and Correlations of Brine/CO2 Systems Under Reservoir Conditions
Authors: Chalbaud C. , Robin M. , Egermann P.
Published: December 2007

It has been long recognized that interfacial interactions (interfacial tension, wettability, capillarity and interfacial mass transfer) govern fluid distribution and behavior in porous media. Therefore the interfacial interactions between CO2, brine and reservoir oil and/or gas should have an important influence on the effectiveness of any CO2 storage operation. As a model, the interfacial tension of the pure water-CO2 system has been studied intensively. Nevertheless, to our knowledge, no interfacial tension (IFT) equilibrium data for brine-CO2systems are available at reservoir conditions for different salinities, temperatures and pressures.

In this paper, we present experimental IFT brine-CO2data obtained at high pressures (45 to 255 bar), high temperatures (27 to 100°C) and different salt concentrations (5,000 to 150,000 ppm of NaCl) using the axi-symmetric drop shape analysis technique (ADSA) for a rising drop case. Special attention was paid in developing a procedure to achieve true thermodynamic equilibrium. The themodynamic conditions were selected in order to cover the most practical CO2 storage cases of interest, liquid and supercritical CO2. A correlation was developped on the basis of the Parachor model, the salt effect and a regression fit of more than a hundred IFT experimental values obtained in this study. This correlation yields a Brine-CO2IFT prediction at reservoir conditions with a mean absolute deviation of 2.5%. We also present correlations to determine the IFT increase due to salt concentration. The existence of a plateau in the brine-CO2IFT values, independent of the temperature and the pressure and only dependent on the salt concentration, has been demonstrated from the experimental data for temperatures between 27 to 71°C and pressures above 150 bar. These pressure and temperature values can be easily found in many geological sites considered as prospects for CO2storage. The linear dependency of the IFT increase with molal NaCl concentration has also been demonstrated.
Solid Expandable Tubulars Facilitate Intelligent-Well Technology Application in Existing Multilateral Wells
Authors: Rivenbark M. , Abouelnaaj K.
Published: December 2007

A major Middle Eastern operator has been exploiting long reach, openhole, multi-lateral technology to maximize oil recovery from a large field producing from a limestone reservoir. Significant production increases have been attained, but the recovery efforts have been hampered by an inability to re-enter openhole sidetracks for remedial purposes. The operator has also encountered water production problems with no real way to identify the source of the water or to remediate it if the source is found.

These problems have been overcome with the introduction of solid expandable tubulars in combination with intelligent well technology. An openhole multi-lateral involves sidetracking out of the main bore while in the open hole. In wells where the technology has been applied, production rates have generally been higher and recovery has improved. A lower unit development/operating cost is also a key driver in this type of well. The new adaptation of using solid expandable tubulars and intelligent well technology allows for re-entry into the lateral for remedial work and real-time pressure, temperature and flow data without the need for well intervention. Intelligent well components allow for quick identification of any water-producing zones and provide a means for shutting off the water production, again without the need for well intervention.

This paper describes the deployment and operation of the new combined-technology application and presents field examples of its use. The paper also discusses applications under development that will push solid expandable tubular technology even further.
Startup of an ESP Well Producing Heavy Crude Oil
Authors: Guerrero-Sarabia I. , Fairuzov Y. V.
Published: December 2007

Numerical simulations of the pump start-up in an ESP were performed A comparison of the model predictions with field data is shown. Results of numerical simulations of the ESP start-up in a well producing heavy (13 °API) crude oil are presented. Liquid level variations in the casing annulus observed during the well start-up are explained. A parametric study was carried out to investigate the effects of reservoir characteristics and oil viscosity on the pressure and flow rate variations, as well as on the system response time. The results obtained can be used for the development of operational strategies for artificial lift systems with ESP.
Coulomb Na Kika: Deepest Water-Depth Completion with Internal Plastic Coating Tubing Application
Authors: Ituah I. A. , Stockwell L. , Stair C. D. , Kumar R. , Neeld S. , Lauer R.
Published: December 2007

The Coulomb field is the 6th field of the ultra deepwater GoM Na Kika subsea development. The two subsea tie-back wells in the Coulomb development (the C–2 and the C–3) were completed in April and May of 2004, in 7,570' of water depth. When completed, the Coulomb wells held the industry record for the deepest water depth subsea completions in the world. The subsea trees and the surface-controlled subsurface safety valves also represented the deepest set to date.

The development planning included selection of the optimum completion design to address a wild-cat in the northern block, which had not previously been penetrated. While the conceptual sand control design was based on data from the previously appraised southern block.

The execution phase was performed on a Generation 5 Moored Mobile Offshore Drilling Unit (MODU) with no prior experience in deepwater completions. Value creation activities were employed to raise the awareness and competence of the rig team to transform improvement opportunities into high performance goals. The Heave-Compensated Landing System (HCLS)1 was used to install the subsea tree, tubing head spool and well jumpers from anchor handling vessels, hence expanding the scope of activities performed off the critical path of the rig and contributed significantly to the record-breaking pace.

Completion fluid, workstring and treatment fluid were carefully selected and tested for well-specific conditions. Specific challenges included the quick turn around completion design and execution on a wild cat, optimizing the drill/complete sequence to complete in uncertain mineralogies, high day rate leading to a desire to be "quick but good", cooling effects due to huge riser volume and long riser trip times. Through extensive preparation and the use of several innovative concepts, record performance was achieved.

This paper also gives an overview of the application of internal plastic coating of the production string in the Coulomb wells. Through nodal analysis with a match to the well performance data, it is demonstrated that the reduced tubing friction associated with the use of internal plastic coating in the tubing has been estimated to yield a 15% increase in daily production in these wells. Success in this application further proves the effectiveness of today's new and novel coating system.
Study on Cement Displacement by Lattice-Boltzmann Method
Authors: Li X. , Novotny R.
Published: December 2007

Cement displacement plays a key role in the well construction and completion. The displacement of drilling fluids with cement to support, protect casing and seal reservoir formation has been a required process in oil industry for years. Also plug cementing has been applied in the abandoned wells for the environmental concerns. In all these cases, poor cement displacements such as cement channeling and bad zonal isolation will result in a subsequent remedial squeeze cementing, which is both expensive and time consuming. Currently, the cement displacement process relies very often on field engineer's experience. So far, in the literature, cement displacement phenomenon has been qualitatively described by lubrication theory on the basis of the macro-scale consideration.

In order to understand the fluid transport behavior, we propose a new approach to simulate the cement displacement process in this paper. From the micro-scale viewpoints, this new approach is using a Lattice-Boltzmann method to describe quantitatively the fluid flow's behavior in the tubular and annulus during the displacement operation. The traditional approaches such as finite-difference, finite-element or finite volume methods of computational fluid dynamics have serious problems: like long computational times, poor convergence and numerical instabilities. However, the Lattice-Boltzmann method is another computational approach that is more efficient and it is based on a more rigorous description of the transport phenomena, the Boltzmann equation.

The velocity distribution profiles with mud and slurry in the annuli will be obtained from the fluid dynamics computation. The effects of slurry properties, inlet flow rate on the displacement's velocity profiles are investigated. The chances of cement channeling also are discussed with the Lattice-Boltzmann's simulation results. This study will provide insight in the mechanism of miscible fluid transport properties and a guidance of cement displacement's job design.
Tahiti: Assessment of Uncertainty in a Deepwater Reservoir Using Design of Experiments
Authors: Carreras P. E. , Johnson S. G. , Turner S. E.
Published: December 2007

Tahiti prospect in deepwater Gulf of Mexico is a three-way anticlinal structure trapped against salt, with primary pay sands ranging from 24,000 to 27,000 ft TVD. The field contains several hydrocarbon-bearing turbidite sands. The discovery well was drilled in 2002, and two appraisal wells were drilled soon afterwards. Due to significant uncertainties remaining after appraisal, probabilistic methods were used to assess development plan alternatives and reserves. The primary purpose of this paper is to show the integrated earth modeling and reservoir simulation workflow, which incorporates uncertainty analysis and experimental design.

The first step of the reservoir simulation workflow was the identification of the uncontrollable parameters that might influence performance predictions. These uncontrollable parameters included the earth model, water-oil contact location, faulting and compartmentalization, reservoir anisotropy, aquifer support, relative permeability curves, pore volume compressibility, rock compaction and dilation, fluid characterization, skin factor and well pressure drawdown. The analysis of available information from Tahiti field and analog fields with simple statistical techniques allowed the unbiased estimation of low, medium and high values of each uncontrollable parameter. The second step was the application of design of experiments to evaluate the impact of each uncertainty on reservoir performance. Monte Carlo simulation was used to estimate P10, P50 and P90 oil recovery and discounted oil recovery for each reservoir. Finally, we developed reasonable P10, P50 and P90 reservoir simulation models that incorporate the full range of each significant reservoir uncertainty.

Probabilistic production forecasts for primary depletion and waterflood strategies supported project decisions like number of pre-drills, total well count, bottom-hole locations, waterflood strategies and facility capacity. Reservoir simulation results also supported proved reserves estimation and economic evaluation of the project.
Oil in Produced Water Analysis and Monitoring in the North Sea
Authors: Yang M.
Published: December 2007

Oil in produced water analysis is important both for process control and reporting to the regulatory authorities. Until recently the determination of oil in produced water has been traditionally carried out using standard reference methods based on solvent extraction followed by an infrared (IR) quantification. However due to the phase-out of Freon-113 for environmental reasons, and also concerns over health and safety of its replacement solvent tetrachloroethylene (also known as Perklone or TTCE), a new reference method based on using gas chromatography has been recommended by OSPAR (Oslo-Paris Commission). The new reference method is based on a modified version of the ISO 9377-2 GC-FID (Gas Chromatography and Flame Ionization Detection), and will be implemented from 1 January 2007.

The paper will give an overview of the current practices of oil in produced water analysis / monitoring in the North Sea and the different approaches that have been adopted by the different countries. It will also examine the differences between the new and old reference methods and discuss the implications on the implementation of the new reference method.
Self-Removing Frangible Bridge and Fracture Plugs
Authors: Swor L. , Sonnefeld A.
Published: December 2007

Currently, the conventional method of removing mechanical fracture plugs is to drill them out with jointed tubing or mud motors on coiled tubing. This necessary procedure can be time-consuming, expensive, and damaging to sensitive formations. The objective of the project presented here was to develop a process that does not require intervention for removal of these tools. The result is self-removing frangible bridge and fracturing plugs that disintegrate from internal explosives and fall downhole into the rathole after service, requiring no removal action.

This paper discusses the development of a self-removing plug constructed of high-strength frangible materials, such as cast iron and ceramics. The frangible materials provide great compressive strengths that can still be exceeded by the shock of explosives. Explosives built into the high-strength, frangible plug are capable of targeting key areas that allow the debris of a shattered plug to pass through. When the frangible parts are exploded, they fall downhole through the targeted area, allowing the entire assembly to collapse into the rathole.

This paper also details the testing of this system in both lab and field conditions. The frangible plugs isolate zones as desired and detonate at the desired times using built-in electronic circuits.

This style plug can replace drillable plugs, thereby eliminating the need for plug removal. This application is especially helpful in sensitive frac zones where placing weighted fluids on the formation could cause production damage. The frangible plugs could potentially change a huge portion of fracturing work in much the same way that (1) composite tools reduced the drillout times of cast-iron plugs and (2) cast iron plugs with brass valves reduced drillout time from that of milling or drilling out plugs containing steel components.
Real Time Data for Structural Integrity and Stability Assessment: A GoM Case Study
Authors: Mitchell M. , Tipton E. , van Dijk Ir. Radboud R.T. , Allen B.
Published: December 2007

This case study illustrates how advanced data transfer and processing techniques can be applied to add value to high resolution environmental and structural monitoring data for use in operational decision making.

With hurricane Ivan in 2004 and hurricanes Katrina and Rita in 2005, the GOM operating area has suffered significant damage to its offshore structures. These experiences have shown it is essential to not only collect environmental and structural data, but to have this data readily available to stakeholders and technical experts for assessment in the aftermath of a storm or other unexpected event that threatens structural integrity.

Advanced systems for handling high frequency, high resolution data have been developed over the past decade to deal with reservoir monitoring data. The following case study from the Gulf of Mexico illustrates how this technology was adapted to provide an operational tool for filtering, transferring and accessing structural integrity and stability data. This tool is now being used to monitor asset integrity during and after hurricanes and other unexpected events that threaten the structural integrity of offshore structures.
Sewage Treatment Project
Authors: Cunha G.
Published: December 2007

The river basin that empties into the Atlantic Ocean near the Brazilian city of Aracaju is the most important in the northeast corner of this environmentally sensitive country. The river basin supplies water for Aracaju's 470,000 inhabitants, as well as for many sugar cane plantations and cattle ranches in the region.

Protecting that water supply was a major concern for Schlumberger operations based in Aracaju. The city's water is collected and treated from the Poxim River that flows close to the base. To ensure no contaminated water reaches the river, Schlumberger recently built an organically based wastewater treatment plant that has eliminated all sewage emissions.

As a result of the new wastewater treatment plant, the Schlumberger base in Aracaju achieved the following results:

Contributed to protection of local water supply Achieved significant reductions in harmful discharges Completely eliminated sewage emission into the Poxim River Received recognition from state environmental agency Eliminated odors and enhanced local vegetation

In 2003, Schlumberger built a wetland tank to collect and treat effluent water from the base, which houses up to 120 employees. The new sanitation installation was built as a requirement to comply with local regulations, established in 2002, in order to renew the state environmental license for the base.

The wetland tank replaced septic tanks that used to discharge used water into the Poxim River. The Aracaju Water Treatment Station collects its water from the river. Now, instead of being released into the river, effluent water is stored and re-oxygenated in a 37-cubic-meter cement treatment tank filled with coarse gravel in which Tabua plants live.

The water treatment plant uses no mechanical devices. Rather aerobic and anaerobic chambers are used to degrade organic material. The final effluent water is evaporated in a wetland and any excess is used to irrigate grass and trees of the base.

With this system, the treatment plant has achieved significant reductions in chemical oxygen demand, oxygen consumption and fecal coliforms. The discharge rates for these are significantly lower than those allowed by the new local environmental regulations. In addition the base has completely eliminated sewage emission into the Poxim River.

The Schlumberger base was recognized by the state environmental agency that inspected the new plant in July/2004 to issue the environmental license. The agency took photographs and requested that plant be copied at other industrial installations at Sergipe State as part of environmental licenses locations. Also, the base's neighbor, a state finance agency, congratulated the base on the elimination of foul odors. Visually, the grass at the base entrance now is continuously green.
Better Valuation of Future Information Under Uncertainty
Authors: Prange M. , Armstrongt M. , Bailey W. , Couet B. , Djikpesse H. , Wilkinson D. , Galljt A.
Published: December 2007

In conditions of high demand for rigs and other scarce equipment, it may be appropriate and more advantageous for a client to agree to a forward contract for a service to be performed at a future date at some specified price. In this case, the service provider is contractually bound to provide the service at the pre-agreed price within a specified time window, regardless of the prevailing price and availability.

This paper presents a mathematically consistent framework using decision trees, conditional probabilities and Monte Carlo simulation to appropriately value future information today. We assume that the client company and the service provider share information on reservoir uncertainty. The presence of multivariate reservoir uncertainties typically makes such valuations non-trivial and mostly intractable to current modeling schemes.

We demonstrate the approach with an example involving a decision to be made for a marginal asset on where to place an injector well relative to a fault. The example considers the value to the client of a future measurement of the degree of compartmentalization caused by this fault. We conclude that when faced with the possibility of obtaining new and useful information in the future, our methodology provides a quantitative valuation framework. This framework could lead, for example, to novel ways of setting up contract terms.
A New Approach to Matrix Sandstone Acidizing Using a Single-Step HF System: A Niger Delta Case Study
Authors: Uchendu C. , Nwoke L. , Akinlade O. , Arukhe J.
Published: December 2007

The use of unique or modified HF acid systems for matrix acidizing within the Niger Delta and some other parts of the world is still the preferred method for effective stimulation of sandstone reservoirs. The continued success of treatments done with modified HF systems in this area are due to its ability to mitigate the rapid spending of the active acid with clays and silicates; prevent matrix unconsolidation in the near wellbore region and the subsequent precipitation of acid reaction by-products within specific well applications. This success has brought about modifications to the acid system and new applications for various well scenarios.

This paper discusses the successful application of a unique sandstone acidizing process that uses a single acid stage (no preflush or postflush is required) making multiple stage treatments much simpler while still achieving both economic and technical targets for the well. It covers the non-formation stimulation treatment of several wells using this single-step method and also describes a successful approach to improving the productivity of high water cut wells with severe fines- damaged gravel packs by this system. Unique experiences acquired during the field trials carried out within the Niger Delta using this system are evaluated. The results demonstrate a significant increase in incremental hydrocarbon production for normally high risk, low reward wells and remarkable stimulation cost reduction via reduced chemical volumes, less equipment requirements and shorter job times.

Also included are a thorough analysis of actual candidate selection criteria, fluid chemistry, actual job design and operational issues during execution of treatments. Key technical and economical performance indicators including skin factors, production rates, specific productivity indices, treatment costs indicate that this system has certainly and successfully increased the application envelope for unique HF treatments within sandstone reservoirs.
Are All PSAs Good Marriages?
Authors: Dabbous S. , Macary S. , Wilson W. R.
Published: December 2007

The foundation for the relationship between a host Government and a contractor oil company in the operation of a petroleum concession is the Production Sharing Agreement (PSA). This document, versions of which have evolved over many years, should recognize that the two parties have one common goal: properly exploit the hydrocarbon resources within the defined concession area - but each has potentially diverse interests. Generally, the representing entity of the host Government is compelled to minimize financial commitment and risk and negotiates with a view to put these obligations onto the ‘Contractor’; and the Contractor, particularly if it is a publicly owned corporation, in accepting the financing and risk obligations, is compelled to seek maximization of the financial return consistent with internally established risk-return relationships.

The stage is set for serious negotiation.

If the Government terms are too restrictive, the company will take its exploration money to another opportunity in a different country. If the company is seen as too greedy, the Government will invite another company as the potential partner. Without an agreement neither wins; with a good agreement, both win. Understanding by all negotiators of the interests, goals and limitations of the other party is essential. Remember that the normal 25 year duration of a concession agreement is similar to that of a good marriage. If instead of "understanding," the parties inter into discussions with only "perceptions" regarding the forces driving decisions made, or positions taken by the other party, the negotiation process can then be unbelievably difficult, and the experience thereafter less than satisfactory, and such perceptions are created at the first reading of a revised PSA form.

This paper presents the authors' expectations about the "perceptions" that may be created by recent changes in the Production Sharing Agreement format adopted by the Egyptian General Petroleum Corporation (EGPC), the national oil company of Egypt which, we believe, is a guide for many Arab countries.
The Successful Evolution of Anton Irish Conformance Efforts
Authors: Smith D. D. , Giraud M. J. , Kemp C. C. , McBee M. , Taitano J. A. , Winfield M. S. , Portwood J. T. , Everett D. M.
Published: December 2007

The Anton Irish field was discovered in 1945, unitized in 1950 for a produced gas pressure maintenance project and converted to a waterflood in 1969. In 1997 CO2 flooding began and currently accounts for about 85% of the unit production. Presently, the entire field produces around 6,500 BOPD; 36.5 MMCFPD of recycled CO2, and 69,200 BWPD. Over the years of flooding, various conformance problems have been identified and many attempts have been made to address these problems with limited to no success. In 2003 a new program was initiated to re-evaluate the problems and design better solutions. This paper will outline the diagnostic efforts that were undertaken, discuss the basic findings of that effort, review the resulting solutions that were designed to resolve these problems, and show the results of this work.
New Barnett Shale Horizontal Completion Lowers Cost and Improves Efficiency
Authors: Lohoefer D. , Athans J. , Seale R.
Published: December 2007

Over the last few years horizontal completions of the Barnett Shale have advanced in an attempt to better stimulate the entire horizontal interval. One standard completion process, where the horizontal is cased and cemented, has emerged. Completing the well consists of running and setting a composite plug on coiled tubing (CT), perforating, stimulating, flowing the well back and repeating the process for the required number of stages for the well. This process is very costly and time consuming, with the added risks of having to remove the composite plugs, plus there is no viable method for re-stimulating these wells at a later date.

For over three years now, a new completion system has been deployed in the Barnett Shale that is fast, efficient, less costly and provides equal to or better production than what the standard completion system offers. Using specially designed mechanical open hole packers run on the production liner, mechanical diversion in the open hole section can be accomplished at predetermined points. This provides well site flexibility in completion design, so the fracturing and stimulation process can be optimized. Each stage in the horizontal section can have a specifically designed fracturing or stimulation procedure. The system has also been designed, to allow all of the fracturing or stimulation treatments to be pumped in one continuous operation with the added benefit of re-stimulating all or selected intervals at a later date if desired. This has proven to be very cost effective and efficient, while reducing the time required to bring production on line. With a multitude of jobs completed to date in the Barnett Shale, this paper will analyze the operational efficiencies, cost benefits, reliability and production data of this completion system compared to the standard completion practices being implemented today.
A Novel Approach for Determining, Evaluating, and Applying Stress Concentration Factors for Rotary-Shouldered Connections
Authors: Tang W. , Muradov A. , Chandler R. B. , Jellison M. J. , Gonzalez M. E. , Wu J.
Published: December 2007

This paper presents a new stress concentration factor (SCF) analysis methodology for rotary shouldered connections (RSCs). The proposed method uses finite element analysis (FEA) as a primary tool to explore the maximum peak stress trends in RSCs and calculates SCF to represent the connection performance. The paper provides a thorough discussion on the SCF analysis methodology and its application in evaluating drill string connection designs. The paper also compares peak stress trends and SCF values among various RSC designs to assist in evaluation and selection of connections for drilling, completion and intervention riser applications.
Stability Criteria for the Thermal Adaptive Implicit method
Authors: Agarwal Anshul , Moncorgé Arthur , Tchelepi Hamdi A.
Published: December 2007

The fully implicit method (FIM) is widely used due to its unconditional stability (even with possibly large time steps). However, FIM is computationally expensive per time step, especially for large number of components. IM-PES (Implicit Pressure, Explicit Saturations), on the other hand, is computationally inexpensive, but only conditionally stable. For large-scale heterogeneous models, the allowable stable time step of IMPES may be extremely small. In the Adaptive Implicit Method (AIM), only a subset of the primary variables is treated implicitly. AIM offers a balance between FIM and IMPES by employing implicit treatment only where necessary. The challenge with AIM is to find a robust and sharp stability criteria that can be used to choose an optimal time step size. The objective here is to derive and verify the stability criteria for a given time step selection in simulations based on a Thermal Adaptive Implicit Method (TAIM). Our linear stability analysis accounts for mass and heat convection, heat conduction, capillary mixing and compressibility. The TAIM stability criteria are obtained using a von Neumann approach. We found the stability criteria to be sharp. That is, mild violations of the stability limits lead to unstable solutions both in the saturation and temperature profiles. The instabilities lead to significant deviations from reference solutions for small CFL (Courant-Friedrichs-Lewy) violations and oscillations for larger CFL violations. Our analysis indicates that, overall, a TAIM-base approach is a promising candidate for simulation of thermal displacement processes of practical interest.
A Retrievable and Reseatable Propagation Resistivity Tool for Logging While Drilling and Logging While Tripping
Authors: Frey M. T. , Argentier L. , Ross M. , Varveropoulos V.
Published: December 2007

A new while-drilling propagation resistivity system with a novel architecture has been developed that greatly reduces lost-in-hole exposure and provides increased operational efficiency and flexibility. The downhole electronics, antennas, and battery are mounted in a retrievable and reseatable tool unit with a 1.75-in. outer diameter. This unit is seated in a 4.75-in., 6.75-in., or 8.25-in. special stainless steel collar that is engineered to be electromagnetically transparent. The tool measures phase shift and attenuation resistivity at 2 MHz and 400 KHz to provide borehole-compensated resistivity measurements at four independent depths of investigation. This service can be run with an existing measurement-while-drilling (MWD) system to provide real-time data such that the combination is retrievable and reseatable in one operation. Alternately, the collar alone can be run while drilling, the tool unit can be lowered through the drill string into the collar, and measurements can be recorded while tripping out at speeds up to 1800 ft/hr. Combination of the data with cased-hole logs can be used to save operational time and improve logging success in difficult environments. The system has completed extensive field-testing. Several field examples and comparisons with while-drilling and wireline logs will be shown.
Customized Reperforating With New Technologies for Optimal Field Drainage and Productivity Enhancement: East Venezuela Applications
Authors: Rodríguez H. , Molina O. , Salazar A. , Rondón A. K. , Méndez M. , Fayard A. , Gama C. , Smitheman C. , Mármol A. , Cervantes E.
Published: December 2007

This paper describes a new methodology and technologies applied for re-perforating production wells in a development field in East Venezuela. Subsequent well tests and production logs demonstrated significant skin reductions and improved flow profiles, delivering up to threefold increase in productivity index and enhancing reservoir drainage efficiency. These results exceeded normal expectations for this type of job.

El Furrial field is located in Northeast Venezuela. The wells typically produce from multiple intervals having widely heterogeneous flow capacities. In order to avoid asphaltene production and water-gas channeling, downhole pressure drawdown has to be limited leading to restricted production. These conditions are further complicated by severe formation damage caused by deep mud filtrate invasion and plugging of existing perforation tunnels with crushed rock material left over from conventional perforating. This environment motivated the team to try a novel re-perforating methodology to overcome these combined challenges.

In these cases, rather than follow the common practice of treating all intervals as having the same average reservoir properties, the reperforation program was customized, taking into account the individual properties and skin of each layer.

Post re-perforation analysis, presented in this paper, clearly shows that the two main causes of formation damage (skin) i.e.: deep mud filtrate invasion and perforation tunnels lined with crushed rock material, were effectively minimized by using new deeper penetrating charges and a controlled dynamic underbalance perforating technique.

El Furrial field success has renewed interest in re-perforation as an important tool for optimizing reserves recovery. This new customized approach used by PDVSA has generated a much higher effective return on investment.
Permeability Modeling for the SAGD Process Using Minimodels
Authors: McLennan J. A. , Deutsch C. V. , Garner D. , Wheeler T. J. , Richy J. -F. , Mus E.
Published: December 2007

The predicted flow performance of Steam Assisted Gravity Drainage (SAGD) well pairs is sensitive to the spatial distribution of permeability. A number of permeability measurements are taken from small scale core plug data. The data may be taken preferentially from certain geologic locations and there may be inconsistencies in the data. The measurement scale is significantly less than that required for input to flow simulation. Mini-models of porosity and permeability are constructed and flow simulated in order to establish representative relationships/correlations at the grid block scale used in SAGD flow simulation. The mini-models are constructed on a by-facies basis honoring the spatial variability within each category. The uncorrected mini-model flow results lead to a too-narrow range of permeability. Geostatistical scaling laws are applied to correct the permeability values.

This paper presents a permeability modeling procedure with application to the Surmont Lease in Northern Alberta, Canada. The mini-model construction, flow simulation of the mini-models, and derivation of representative porosity-permeability statistics are described and documented in this context. A comparison of SAGD flow simulation results (recovered bitumen and steam-oil-ratio) with different permeability modeling procedures is presented to support the relative importance of modeling permeability. The legitimacy of any particular permeability model can only be compared to or validated with comparison to actual flow performance at some time in the future, which is a difficult task. Even with actual flow data, this is a difficult task. This will occur at the Surmont project, at some point in the future.
Advancement in Completion Technologies Proves Successful in Deepwater Frac-Pack and Horizontal Gravel-Pack Completions
Authors: Lorenz M. , Ratterman G. , Martins F. , Triplett W.
Published: December 2007

When operating companies and the service companies combine teamwork and technology development with cohesive communication and planning, the result is proper integration of multi-discipline technologies to ensure successful field applications. The authors will outline some of the obstacles encountered and describe how the tools and procedures were designed to optimize reliability and achieve completions with better well life.

Completion case histories are reviewed for wells in Brazil's offshore and deepwater Campos Basin, and deepwater Gulf of Mexico. The discussion addresses well planning, pumping operations, frac-pack design, selection of well screens with extended longevity and fluid systems that prevent formation damage.

Openhole deviated and horizontal completions continue to be a primary method for reducing cost and improving recovery by maximizing reservoir contact. Integrating this technology with Intelligent Well Systems achieves a significant reduction in the number of wells required to maximize well productivity and reservoir drainage. Openhole completions have been utilized to successfully develop many of the reserves in offshore Brazil. These completion types include horizontal producers and injectors, gravel packs, stand alone screens, openhole gravel packs with annular isolation and integration of Intelligent Well Systems.

Globally, technology has enabled the successful application of gravel packs in lateral lengths exceeding 8,300 feet, and water depths exceeding 6,100 feet. The growth of frac packing in deepwater Gulf of Mexico has intensified engineering efforts to meet the demands specified by the operating companies for fracturing formations with high permeability. Frac-pack applications in deep water can require pump rates exceeding 60 barrels per minute and proppant concentrations of 15 ppa. Specialized tools and performance software have advanced to address the increasing demands and risk management required in today's deepwater market. The evolution of technology is enabling reduced operations risk, better reliability and enhanced oil recovery.