bluuebunny/crossref_metadata_2025 huggingface dataset:
The Need For A Marketing Strategy For Alberta Bitumen
Authors: Redford David A.
Published: March 2010

In the Alberta oil sands, Alberta has one of the three gigantic petroleum deposits in the world. The others being in the Middle East and in the heavy oil belt of eastern Venezuela. Fifteen years ago, we could produce only a small fraction of this immense deposit (perhaps 4 billion m3 from the Athabasca deposit and a small portion of the Clearwater formation in Cold Lake) and costs were high.

Over the past 15 years, government and industry have invested heavily in research and development of new technology for bitumen extraction. The results have been spectacular. Not only can we produce vast amounts of bitumen (~ 45 billion m3) from the Athabasca, Peace River and Cold Lake deposits, but it can be done in many cases at one-third to one-half the previous cost.

The application of Steam-Assisted Gravity Drainage Technology from Underground Access (SAGDUA) to the thick continuous sections of the Athabasca deposit can produce 12.6 billion m3 of bitumen for C$7.00/bbl (Fig. 1). This is the same average cost of producing conventional crude in Alberta, excluding exploration costs. At a supply cost for bitumen of C$9.00/bbl, it is estimated that up to 42.5 billion m3 (270 billion bbls) can be recovered.

Despite these spectacular gains in technology and the resulting lower cost of producing bitumen, we see no rapid increase in bitumen recovery. Indeed, most new bitumen production projects have been put on the back burner or moth-balled. Five major integrated projects have been cancelled. Why is this occurring?

Figure 2 gives the price in U.S. dollars of bitumen in Edmonton. The price is extremely variable and at times very low (C$5.00)/bbl). The field price is even lower (as low as C$3.00/bbl) With such highly variable and often very low prices, it is not surprising that investment and development has been suppressed. It also demonstrates the inadequacy of a marketing strategy for Alberta bitumen which relies on the sale of raw bitumen. Alberta is far from tide water and bitumen is not a readily transportable commodity. Alberta bitumen, therefore, cannot readily access world markets and command competitive world market price. In recent years, bitumen has been transported to the Chicago area, and more recently to Billings, Montana, by dilution with light condensate. This provides a very limited and restrictive market because only specialized conversion facilities can accept bitumen.

The dilution condensate, which goes along for the ride, commands a low value because of its high yield of low octane gasoline containing excessive aromatics. These have low demand in an increasingly more environmentally conscious world.

What are the options? The sale of bitumen in western Canada is dependent on the very limited and highly variable asphalt market and this currently contributes to the high variability of bitumen prices in Edmonton. The transport of bitumen, as an oil-in-water emulsion, while technically feasible, suffers the limitation in Canada that we live in a very cold climate.
Coil Tubing Fishing Operation On a Deep, High Pressure, Sour Gas Well
Authors: Stadlwieser J. , Best J. , Willson D. , Bloor B.
Published: March 2010

The use of coil tubing in fishing operations has been limited to date. This paper discusses a coil tubing fishing operation on a 4000 m, 30% H2S gas well with 27 MPa surface pressure. A 12.5 metre wireline tool string was stuck inside the production tubing at 1770 m, with 76 m of elemental sulphur fill on top. The need for 23 m of lubricator during coil tubing fishing operations was eliminated by designing a pump through Pressure Deployment System, along with a pump-off sub. Problems encountered with the Pressure Deployment BOPs will necessitate periodic inspection of the BOP stack on future high pressure, sour well work.

Advances in coil tubing technology have made coil tubing an economical alternative for many oil field operations. Fishing operations can now be performed on live wells without long sections of lubricator. Coil tubing has increased to 88.9 mm (3 1/2") in size, has become more H2S resistant and is now continuous without butt welds. The components of the coil tubing unit, such as the injector have also increased in strength allowing work in deeper and higher pressure wells.

Introduction

Esso's Obed Field near Hinton, Alberta is comprised of five sour gas wells, three of which are completed in the Nisku formation and the remaining two in the Leduc formation. A gauge ring with a junk catcher was run into Esso et al. Obed 11-13-54-23 W5 in an attempt to determine the amount of sulphur and iron sulphide scale buildup on the 114.3 mm tubing.

The gauge ring became stuck due to sulphur scale buildup at 1770 m and was left in the hole. An unsuccessful attempt was made to fish for the gauge ring using braided line. During the fishing attempt the fish could not be pulled free and the fishing tool would not release from the fish so the braided line was pulled out of the rope socket. This left a resulting fish of 12.5 m in the well. An impression block run later revealed that 76 m of sulphur had piled on top of the fish.

This 4000 m, 8% CO2, 30% H2S gas well had a bottom hole pressure of 38 MPa and 27 MPa surface pressure. Figure I is a schematic of the well,

FIGURE 1: Subsurface schematic: Esso et al. OBED 11-13-54-23 WSM. (Available in full paper)

wellbore, shear events near the well bore (combined P and S phases, too close to be distinguished), or shear events far away from the wellbore (S phase only, P phase completely absorbed). It is interesting to note that most of the signals are oriented within the N30–40 °E window (Figure 6). which is close to the expected orientation of the main fracture. The results also show that the best polarization is obtained within the first quarter-period of the wave and degenerates quickly afterwards. This can be explained if one assumes that the events are occurring close to the wellbore. The first part of the waveform would be mostly a P-wave that would become gradually contaminated by S-waves.
Reservoir Pressure Analysis: Art Or Science?
Authors: Mattar L.
Published: March 2010

Introduction

Measure the pressure in a gas well using high resolution electronic recorders (resolution better than 1 kPa). Produce IE6 m3 of gas. Shut the well in until complete buildup and measure the pressure again. It is 100 kPa lower than the initial pressure. Does this mean depletion? The material balance relationship for a gas pool is an equation of a straight line. All you need is two pressure/production measurements to define this line. The ends of this line give you the initial pressure and initial gas in place. Does this mean we don't need to measure the initial pressure anymore. because we can determine it, a posteriori, from any two measurements'? Two pressure recorders (electronic, high sensitivity) sitting one metre (vertically) apart show a difference of 1 kPa. Is the fluid between them gas or water'?

From a science perspective the answers to the above three questions are very obvious: yes, yes, gas: but from an engineering perspective, the answers are: sometimes, no, maybe either. These examples are typical of the issues we face as engineers (particularly reservoir engineers), dealing with inaccurate data and trying to estimate unknowns, and sometimes "unknowables."

With the advent of the computer age, we have lost something precious; we have thrown out the baby with the bath water. Not only did engineers throwaway their slide rule, but with it some of us threw away the slide rule mentality - the art of approximation and judgment. I remember with the early electronic calculators the square root of 4 was not 2, it was 1999 It is also apparent that, with the advent of digital watches, time is no longer a continuum. but it occurs in discreet quantities such as seconds! (As seen on the LED display of the digital watch). This is the dilemma of our age.

Science and Art - Theory and Practice

Computers now calculate at the rate of millions of instructions per second. They have given us the ability to arrive at the answer faster. Usually the answer will be wrong! But if we are good engineers it will be the best possible answer. This underlies the essence of engineering (particularly reservoir engineering). We are usually working with extremely complex real life situations, idealized (simplified) models, precise but inaccurate data, incomplete data sets and conflicting data. We can study and compute multiple options based on several assumptions, each leading us to different conclusions. But, at the end of the day, in spite of the numerous solutions, we usually only have a choice of one of these options to act on.

Science and computers have provided us with the theory. However, superseding all this theory, must be the practice. Often this is a gut feeling, procedure based on experience of real life behaviour of systems. In other words, it is an art." Good engineering is an art based on both science and experience, theory and practice.
Coalbed Methane In Alberta
Authors: Byrnes T.L. , Schuldhaus K.F.
Published: March 2010

Alberta's coalbed methane (CBM) resource has been estimated to be comparable in size to that of the province's conventional natural gas resource base. Although only limited drilling for CBM targets has occurred in the province to date, considerable interest in how development of this resource might proceed has been shown by the gas and coal industries, the public, and regulatory agencies. Because CBM is a form of natural gas, it is regulated in the same manner as other natural gas. An overview of CBM in Alberta is given, including the potential resource base, elaboration on the application of natural gas regulations to CBM, activity to date, and some of the main regulatory issues and initiatives that have arisen. It is shown that there is a need to collect Alberta specific CBM data before decisions can be made on the necessity of regulatory change specifically for CBM development.

Introduction

Numerous papers and articles have been published over the past few years on various aspects of CBM. The growing number of CBM wells and increasing amount of CBM production in the United States (USA) has caused somewhat of a surge in published case histories and field experiences for the major CBM basins ill that country. Much less CBM field experience currently is available for Alberta, but the potential CBM resources of the province have not been overlooked.

Early investigations into the production of CBM in Alberta date back to the late 1970's, but interest waned in the early to mid 1980's with falling gas prices and a levelling in gas demand. The more recent interest in CBM development ill Alberta was spurred on by the surge in CBM activity that occurred in parts of the USA from 1989 to 1992.

A summary of the current CBM situation in Alberta is given in this paper. The province's CBM resource potential and regulatory framework are overviewed along with activity to date and some of the issues that have been raised regarding the development of this resource.

Why the Interest in Coalbed Methane in Alberta?

The recent interest in CBM in Alberta can be attributed to three main factors:the large CBM resource potential of the province.the large amount of recent CBM development activity in the USA, andenvironmental concerns regarding the development of CBM in Alberta.

Alberta's Coalbed Methane Resource Potential

CBM is a naturally occurring hydrocarbon gas, consisting largely of methane, that is generated by and stored in coal seams. Because Alberta has extensive coal deposits, it follows that the CBM resource associated with these deposits has the potential to be significant.

Coals of varying thermal maturity, or rank, underlie about 45 per cent of the province(1), with essentially all of the coals being located south of Township 75 as shown ill Figure I. These coals are associated with Upper Jurassic, Cretaceous, and Lower Tertiary strata as shown in Figure 2, and much of it may be of suitable rank to hold potential for CBM development.
Co-polymer Beads Reduce Friction In Horizontal Wells
Authors: Bird J. , Garrett C.
Published: March 2010

Introduction

Divinyl benzene co-polymer beads, better known as plastic beads, have been used for reducing torque and drag in conventional drilling operations for 17 years. Over the last four years, they have also been utilized to reduce friction in horizontal wells when drill pipe is not sliding at a fast enough rate, or is not moving at all. Co-polymer beads have also gained recognition as a means of reducing friction in coiled tubing workovers.

Friction is reduced by introducing co-polymer beads between the drill string and bore hole. Laboratory testing and field experience have developed methods for reducing friction through specific application techniques. Application of the beads can vary, from spotting small "pills" in specific sections of the bore hole to carrying a concentration of beads throughout the system using a bead recovery unit.

Drill string drag is the incremental force required to move pipe up or down in the hole, and torque is the force required to rotate pipe. The magnitudes of torque and drag are related in any particular well, and high drag forces and excessive torque loads normally occur together.

There are a number of causes for excessive torque and drag. They include:tight hole conditions;sloughing hole;key seats;differential sticking;cuttings buildup because of poor hole cleaning; andsliding well bore friction.

With the exception of sliding friction, these causes are associated with problem conditions in the well bore.

Although all of these conditions can occur in horizontal wells, the primary source of torque and drag in a horizontal well with good hole conditions is sliding friction. The ability to alleviate sliding friction using co-polymer beads has proven to be extremely beneficial in horizontal drilling and workover operations, including standard pipe and coiled tubing.

Sliding Friction

Normal contact force and the coefficient of friction between contact surfaces are the two factors that affect sliding well bore friction. Another factor, capillary attraction, must be considered in open hole situations. Capillarity is described as the relative attraction of the molecules of a liquid where it is in contact with a solid. The relative attraction of molecules leads to a force of adhesion between a solid and a liquid.

The wallcake of a well bore will exert very strong capillary attraction forces on a drill string when it comes in close contact with the drill string. This is explained by the fact that the wallcake or mudcake is composed of very small particles of clay, barite, sand, or other matter, and these minute particles will have considerably more surface area exposed for wetting by liquid than would larger particles in the same section of mudcake. The smaller the particles, the more surface area exposed for liquid wetting, thus the greater the attractive capillary force exerted.

The capillary attractive force could lead to the drill string adhering to the wallcake, creating torque and drag. The beads, having a larger particle size than the solids in the wallcake, reduce this adhesive force.
Selection of PVT Properties For BLack Oil Simulation
Authors: Smith R.A.W. , Tan T.B.
Published: March 2010

It is generally accepted that the reservoir depletion process is a differential liberation process where the gas is removed from contact with the oil as soon it is formed, and the production of fluids through tubing and separators is a flash liberation process where the gas liberated from solution remains in contact with the oil.

laboratories commonly perform differential liberation and separator tests on the reservoir fluid and then use a correlation described by Amyx et al.(1) to arrive at a composite liberation curve for an optimum separator pressure. Engineers are often confused as to which of the two sets of PVT data, i.e, differential or composite, should be used in a black oil simulation of the reservoir. The differences between the two sets of the data becomes more substantial as the API gravity of oil increases.

The black oil simulator used in this report has a compositional formulation and has the ability to rigorously model the PVT behaviour by entering differential liberation data for reservoir conditions and using a surface separator option for the surface flash process. This paper describes a critical comparison of the three methods to enter PVT properties in a black oil simulator.

The results of using the simulator in three ways:differential liberation at reservoir, surface separator for flash,composite liberation data,differential liberation data,

are described in this paper for a medium gravity crude.

It is shown that the composite liberation data most closely represents the rigorous representation of phase behaviour as in (a). Use of inappropriate liberation data could result in significant error in estimates if oil-in-place as in (c). The paper compares the differences between composite liberation (b) and the rigorous representation (a), such as different initial pressure and saturaturation gradients due to initial density differences.

Introduction

When studying reservoirs with moderately high API gravity and gas-oil-ratio values, it becomes more important to incorporate both the differential and flash components of the PVT behaviour. In order to demonstrate the differences between using only the differential data as opposed to including the effects of the flash data, actual PVT data from the model study which is referred to as reservoir A, with an API gravity value of 34, is incorporated into the SPE Second Comparative Solution Project(2). The data of the Second Comparative Project remains the same except that the original PVT data set was replaced by the PVT data from reservoir A as shown in Table 1. Note that the differential solution gas (Rs) value if reservoir A was significantly highr that the separator flash data.

Problem Statement

Potential loss of intermediates, number of stages in the compressor design and an accurate forecast of oil and gas production are among the major concerns of any simulation study with PVT properties similar to Reservoir A. To accommodate these requirements, it would be necessary to accurately model the PVT behaviour of the fluids from the reservoir to the tanks.
Heavy Oil-"Riding the Wave"
Authors: Morgan Rob
Published: March 2010

This month we will be presenting our fifth year of the one day "Slugging it Out" conference series. Co-sponsored by the Heavy Oil Special Interest Group and the Canadian Heavy Oil Association, this successful series gathers individuals interested in all areas of heavy oil development for an informal and informative brainstorming ession. our theme this year is "Riding the Wave," which we feel is very appropriate given the resurgence in heavy oil activity, primarily due to heavy oil wellhead prices in the $20/bbl range. The conference will be held at the Metropolitan Centre on April 10 and registration information is available by contacting The Petroleum Society office. Now that I've dispensed with the commercial, let's consider the last 12 years of our heavy oil industry.

I believe this is my second major price cycle in the heavy oil business. As a production engineer in Lloyminster in 1985, it appeared that all that was required to make money was to get oil out of the ground, by whatever means possible. Wellhead prices for heavy oil were in the $30/bbl range, and economic analysis would support drilling a 20 bopd well. Price forecasts were of the "hockey stick" variety, and the majors were amassing infrastructure to be ready when prices hit $50/bbl. Thermal projects (primarily Cyclic Steam Stimulation) were in full operation predicting 30% recovery of the original oil in place. A conventional vertical primary well was drilled on 40 acre spacing and the rule of thumb recovery factor was 5%. Sand production was a necessary evil that contributed to higher operating costs and could sometimes be mitigated by reducinghe drawdown on your well. Progressive (or as they are more correctly called now Progressing) Cavity Pumps had appeared on the scene, but were generally not accepted as a means of producing heavy oil.

The decision by OPEC in early 1986 to recapture market share lost over the years was a dramatic "wake-up" call to our industry. By mid to late 1986, a barrel of heavy oil in Lloydminster was selling for less than $10 and companies were scrambling to minimize the losses. The first to go were the thermal projects as operating costs were typically in excess of $10/bbl. Next, the marginal primary producing wells were shut-in. The human toll was most obvious as the vacancy rate at my apartment complex went from 0.1 % to 30% in a matter of eight months. Throughouthis process, I realized that I had very little understanding of the factors that influenced the pricing of heavy oil, and perhaps it was time to remedy that situation.

Pricing for heavy crude is based on a differential to a light sweet crude (usually the Edmonton par price for a 40 API crude) which encompasses differences in quality (density and sulfur content) and the amount of condensate (C5+) required to make up a heavy oil blend suitable for pipelining. A Lloydminster type blend is typically in the order of 22 API and will contain anywhere from 20 – 25% condensate.
Can Snake Oils Become Panaceas?
Authors: Davis Gordon A.
Published: March 2010

At just about any time during the course of recent history, in the "oil patch," there have been processes or "technologies" which for one reason or another did not fit the paradigm of the time, and in many cases were branded as radical, extreme, unwarranted or even dangerous, as they had not either been sufficiently developed or tested to everyone's satisfaction. In many cases, some were even considered "snake oil," as they seemed to work, but no one could say why, and in many cases the results were short-term or not at all.

And so it goes, in the ever present struggle by producers to increase field productivity. So many possibilities, all of which would take a part of the profits from current production, while promising future increases.

For many of these technologies, success and acceptability came from the acceptance of the process by some forward thinking, established service company which decided to invest in the process, and even to improve or develop it through genuine research projects, lack of such acceptance resulted in failure and obscurity. Such is the case even today, with many applications which can and in many cases do, improve productivity substantially, using unconventional or even unorthodox methodology. In all of the problems faced daily by producers, two of the major ones in the current market are: formation/perforation damage, and waxing and scaling.

Formation/perforation damage which occurs to the formation from initial drilling and fluid invasion thereby reducing effective porosities and permeabilities, or damage which occurs from perforating, such as reduced core flow efficiencies, have always been problems, which have required many different approaches in as many situations. However there now appears to be a consistent application which can help.

Historically, explosive stimulation has always been treated as one of those "snake oil" methods which worked in many cases, and not in just as many, with no real way of telling where it would or would not. In too many cases, not only did it not, but many times it also caused significant and irreversible damage in the process.

Little Wonder in the Lack of Faith by the Industry

In recent years, however, significant scientific investigation, and improvements both in the method and materials (low detonation velocity epoxies) have significantly increased the efficiency of propellant stimulation technology. More important still, the ability to model and simulate the stimulation technique have been developed and refined, and high speed impact resistant data recorders have been developed which can measure and record the event. By simulating the event and using precisely calculated amounts of propellant, and by analysing the data recorded, an effective, repeatable stimulation can be obtained. With this sort of control and predictability, many companies have decided to use propellant stimulation, in a variety of applications, rom heavy oil perf clean up and sand-arch collapse, to prefrac treatments of sandstones and carbonates, all with a good deal of success.
Patterns And Structural Positions of Productive Fractures In the Asmari Reservoirs, Southwest Iran
Authors: Gholipour A.M.
Published: March 2010

In wrench faulted areas, similar to the one introduced here, identifying structural styles and their histories could be one of the most important tasks in studying tectonic related fractures and faults.

The main purpose of this paper is to examine the patterns and structural positions of productive fractures in different reservoir structures of the Asmari formation (Oligo-Miocene) in the Khuzistan oil fields belt of southwest Iran.

Details of productive fracture positions have been studied on four major Asmari reservoirs, using:production data (e.g., production rates and productivity indices) which are the most reliable indirect fracture identifiersmud losses, to identify open fracture portionfaulted well assemblages to find tectonically active Portionssecond derivative map to find the portions of the maximum rate-of-change-of-dip on top of the reservoir structures, where it is expected to have maximum fracture density.

The results were then compared with the surface fracture patterns and densities in the mountain front boundary in the area.

In general, productive fractures were found to be associated mainly with the plunges and bends of the Asmari reservoir structures.

To assist in determining optimal horizontal well trajectories in the anticlinal traps of the studied area, idealized fracture pattern models have been presented in this paper.

Structural Styles and History of the Area

Identifying structural styles and their histories could be one of the most important tasks in studying tectonic related fractures. These styles are generally differentiated on the basis of the extent of the basement involvement and/or the detachment of sedimentary cover.

In the Khuzistan oil fields belt of southwest Iran, reservoir structures have become further complicated by the superimposition of fundamentally different tectonic regimes, which are still active based on a high concentration of earthquake foci in the area (Figure 1).

Some evidence of recent activity of the regional basement controlled faults is indicated by a high concentration of the earthquake epi-centres (foci), the existence of sinuosity (bending) in the reservoir structures and high length to width ratio in most of the anticlinal structures of the Plio-Pleistocene age.

The major deformation took place in the Miocene, following the collision of the Arabian plate with the central Iranian block. This convergence, with its accompanied subduction, caused the folding of sedimentary cover into the present styles; huge anticlines, with general trends of northwest-southeast perpendicular to orogenic (folding) compressional forces which are southwestnortheast trending.

These styles are mostly formed during three different stages:Early orogenic shocks, which caused the early folding phase in the Miocene.Main orogenic shocks, which caused the late folding phase in the Pliocene.Recent orogenic shocks, which caused the recent folding phase.

Each folding phase created its own related fracture pattern, which are discussed in this paper.
Flare Gas Flow Rate Measurement By a Steady State Tracer Dilution Method
Authors: Tang J.S.
Published: March 2010

A tracer dilution method based on steady-state tracer concentration at constant injection rate has been designed and implemented successfully at Imperial Oil's Quirk Creek gas plant to measure flare gas flow rate which, together with the H2S content, is required for renewing the clean air operating licence. The gas flow rate was determined to be 2.06 ± 0.05 Sm3/min or 2.48 ± 0.05 m3/min at the stack conditions, and the H2S concentration was averaged at 13.7 ± 2.9% over a period of six hours. The results agree with those obtained by simulation and mass balance. This is the first known reliable method for measuring flare gas flow rate in a low pressure, low flow rate and extremely sour environment. The method is well suited to accurate measurement of gas, oil, water flow rates in refining as well as production facilities. Complications due to tracer partitioning into the discharged liquid and dissimilar gas and tracer allocations in a complex flow field are discussed. A method for simultaneous measurement of flare gas and liquid discharge rates in a liquid knock-out tank using partitioning tracers is also presented.

Introduction

In the Quirk Creek gas plant, sour glycol and produced water constitute the two major sources contributing H2S to the flare gas stream. In the gas sweetening unit, sour gas is dehydrated by glycol before entering the amine absorber. The dissolved sour gas and water vapour are removed from the spent glycol in a subsequent glycol re-generation cycle. The separated gas is combined with the sour produced water overhead gas and gases from various other sources and then piped to a liquid knock out tank. This mixed gas stream which has a H2S content as high as 40% is flared with a valid clean air operating licence. The current licence was to expire in May 1993 and, in accordance with the government regulations, the daily sulphur emission rate has to be included in the licence renewal application. Sulphur emission calculation requires the knowledge of H2S concentration and the flare gas flow rate. While the H2S content can be accurately measured by gas chromatograph, there is no suitable gas flow meter which can be used in a low pressure, low flow rate and highly hazardous environment. A tracing method was thus developed by for measuring gas flow rate at such conditions.

Theory

Gas flow rate can be determined by a steady-state tracer dilution method. A gas tracer with high vapour pressure which can completely flash into the gas phase is injected at a constant rate into the gas stream and the tracer concentration is monitored downstream of the injection point, preferably near the gas outlet. The gas flow rate can be derived from the steady-state tracer concentration and the tracer injection rate. The tracer dilution method has been used successfully in measuring gas flow rate through compressor(1). The tracer results agreed with those measured by orifice flow meters within an accuracy of ± 1%.
The Steam And Gas Push (SAGP)
Authors: Butler R.
Published: March 2010

While heavy oils can be produced by horizontal wells at economic rates, the extent of recovery is small because of loss of drive and/or watering out of the production. In typical cases a recovery of only a few per cent of the OOIP is achievable. SAGD overcomes these problems by allowing high production rates with only a small drawdown. The reservoir pressure is maintained by the injection of the steam and operation without steam coning is practicable; very high recoveries are normally obtained.

In conventional SAGD the depleted reservoir becomes filled with steam at the saturation temperature corresponding to the operating pressure-typically 200 to 250 ° C. Large quantities of steam are required to heat the depleted reservoir, the reservoir surrounding the steam chamber and, particularly with thin reservoirs, the overburden. With high quality, thick reservoirs SORs of about 2.5 - 3 are obtained but in thinner reservoirs, and in reservoirs with lower oil saturations, SORs are much higher and the process is uneconomic. The problem is compounded by the steam chamber having long sloping boundaries that extend the heated area.

In this paper it is shown that it is not necessary for the whole steam chamber to be at a uniform high temperature. Only the lowest part, where the coning tendency is greatest, needs to be at the highest temperature. High temperatures in the upper part of the chamber are an "overkill" that results in wasted heat. It is proposed that the SAGD process be modified by injecting noncondensible gas, such as natural gas, with the steam from a horizontal injection well somewhat above the producer. Gas accumulates in the chamber above the injector and lowers the temperature. Considerable savings can be made by this approach without a substantial decline in performance. In one example it is shown that the heat stored in the chamber per cubic metre of produced oil will be only 62% of that for conventional SAGD and that the heat lost to the overburden will be a very much smaller fraction. This concept should greatly extend the range of reservoirs that can be produced economically.

Introduction

For the efficient and economic recovery of heavy oils it is necessary to employ means for facilitating the flow of the viscous fluid through the reservoir. Not only is it necessary to offset the effect of very high oil viscosity by providing extended contact and/or viscosity reduction by heating, but it is also necessary to maintain the drive needed to move the oil as the reservoir becomes depleted.

Some approaches such as the use of long horizontal wells or cyclic steaming are effective in promoting flow but only produce limited recovery. Steamflooding and, more recently, SAGD also maintain reservoir drive and allow high recoveries. However, because of their considerable heat requirements, these processes are limited in their economic use to higher quality reservoirs.

It is the purpose of this paper to describe a new concept for the production of heavy oils that is a modification of the SAGD process(1–5).
Industrial water reuse opportunities and high temperature compatible membranes
Authors: Valentin A.-C.
Published: March 2010

Process condensates represent a real value to the industry as it usually contains several items of potential savings, including but not limited to heat energy and water. In most cases the condensate has become contaminated with unwanted particles or with product carryover making it unfit for direct reuse in the process or as boiler makeup water. Conventional methods use heat exchangers for partial recovery of the heat content to be followed by ion exchange or reverse osmosis limited to 30–40°C feed temperature. By using the Duratherm® High Temperature compatible membranes in RO and NF, it is now possible to process the condensate at temperatures up to 80°C thereby maintaining the calorific value of the stream. Many plants also produce a product using evaporation. The overheads from the evaporators usually contain a small amount of their product that must either be recovered by an additional evaporation step or disposed of in a waste treatment plant. These reverse osmosis or nanofiltration systems allow concentration of the product, produce high quality water suitable for reuse, and reduce the load on the waste treatment plant. The treated condensate can then be used for various utility operations including boiler & process makeup.
Perfluorinated chemicals (PFCs) in water purification plants (WPPs) with advanced treatment processes
Authors: Shivakoti B. R. , Fujii S. , Nozoe M. , Tanaka S. , Kunacheva C.
Published: March 2010

A series of perfluorinated chemicals (PFCs) surveys were conducted in two water purification plants (WPPs) having ozonation and granular activated carbon (GAC) filtration processes. In each plant, six different processes samples (source water, influent, coagulation-sedimentation effluent, ozonation effluent, GAC filtration effluent, and final tap water) were collected for two times and eight PFCs were measured. The results showed that seven kinds of PFCs (PFHxS, PFOS, PFHpA, PFOA, PFNA, PFDA, and PFUnDA) were detected in both plants with concentration range of 0.5–53.5 ng L−1, while the range of total concentration of all seven PFCs was 31–90 ng L−1. All detected PFCs were not removed effectively in both dates but removal was observed to some extent for certain PFCs (PFNA, PFDA, PFOS, and PFUnDA) by GAC filtration tank.
Clinico-radiological characteristics of bronchial carcinoid
Authors: Stevic R. , Jovanovic D. , Masulovic D. , Pesut D. , Vasic N. , Stojic J.
Published: March 2010

Objectives: To review clinical and radiological characteristics of a patients with bronchial carcinoid. Methods: In this retrospective study, we reviewed the clinical, pathological and imaging findings in 42 patients diagnosed with bronchial carcinoid during the seven years period. Results: There were 23 women and 19 men, with a mean age of 47 years (range from 15 to 75). Thirty patients had typical and 12 atypical bronchial carcinoid. Dominant symtoms were cough (46,7%) and 38%. Tumor was localized in 28 patients in the left, and 14 in the right lung. On radiographs carcinoid manifested as tumor shadow in 40.5%, nodule and atelectasis in 21.4% cases each respectively, pleural effusion and pneumonia in 7.1% each respectively and hyperinflation in 2.4% of the cases. Computerized tomography revealed endoluminal tumor in 30.9% patients. Conclusion: Major imaging findings are central, tumor mass or nodule and obstruction signs like atelectasis. Diagnosis is confirmed by pathological examination of samples taken by bronchoscopy or surgery.
Preoperative chemoradiotherapy in locally advanced esophageal cancer
Authors: Radosevic-Jelic Ljiljana , Stankovic V. , Josifovski T. , Nikolic V. , Popov I. , Pesko P.
Published: March 2010

Preoperative or definitive chemoradiotherapy defines today the standard treatment of patients with localized or locally advanced esophageal cancer. Preliminary results of our study are presented. 46 patients with locally advanced squamous cell esophageal cancer (T3-4, N0-1, M0) were enrolled. All patients recieved concomitant chemotherapy (Cisplatin/ 5FU/LV) and radiotherapy (45-50,4Gy). Clinical response rate was 59% (3 patients (7%) complete response, 24 patients (52%) partial regression, 13 (28%) stabile disease, 6 patients (13%) disease progression). Out of 46 patients, 12 were operated (26%), all with R0 resection. Complete patohistolgical regression (TRG 1) was noted in 5 patients (42%). TRG 2 i TRG 3 in one (8%) and 3 patients (25%), and TRG 4 in 3 patients (25%). Mean survival time in operated group of patients was 9,3 months, and in nonoperated group 5,5 months. Studies show improved survival rate in patients with complete response to chemoradiotherapy and R0 resection. Individualy tailored therapy is essential.
X-ray and CT presentation of advanced gastric carcinomas of different locations
Authors: Djuric-Stefanovic A. , Saranovic Dj. , Masulovic D. , Lazic Lj. , Nastasic T. , Visic B. , Colic J. , Dzelebdzi D. , Djordjevic-Sopalovic D.
Published: March 2010

We presented the X-ray and CT findings characteristic for gastric cancers of different localizations (localized in different parts of the stomach). Particularly, esophagogastric junction (EGJ) carcinomas and antral carcinomas are singled out, as two localizations of gastric cancer that we usually meet in everyday clinical and radiological practice, and which have completely different radiological presentation. Advanced carcinomas of esophago-gastric junction, whose incidence is on the rise, usually affect the distal segment of the esophagus, cardia, and proximal part of the stomach, in different proportions. Siewert's, and the Japanese classification of these tumors are listed. Due to the involvement of the distal esophagus, scanning region, besides the abdomen, should be expanded to the chest. Advanced cancer of the antral part of the stomach is presented by the X-ray as a fungating, infiltrative, or combined form, often capturing the entire wall circumference. Possible infiltration of the left liver, the body and neck of the pancreas, colon and anterior abdominal wall should be estimated by CT.
Diagnostic value of Diffusion Weighted Imaging in assessment of malignant focal liver lesions
Authors: Maksimovic R.M. , Kratovac-Dunjic M.S. , Lilic G.B. , Milenkovic R.M. , Masulovic D.M. , Milicevic M.
Published: March 2010

Introduction: The study was designed to determine if there was a difference between apparent diffusion coefficient (ADC) values using diffusion weighted imaging (DWI) MRI technique between different malignant focal liver lesions. Patients and methods: The study included 63 patients with focal hepatic lesions: fourteen patients (22.2%) with hepatocellular carcinoma (HCC), 16 patients (25.4%) with hepatic metastatic colorectal tumors, 17 patients (26.9%) with cavernous haemangioma and 16 patients (25.4%) with hepatic cysts. MRI was performed with 1.5T scanner, using EPI sequence with ADC values being determined for all lesions based on three b values. Results: ADC values were statistically different among the groups (F=70.7, p<0.01): HCC patients 1.11+0.29x10- 3 s/mm2, metastatic tumours 2.18+0.15x10-3 s/mm2, haemangioma 2.22+0.32x10-3 s/mm2, cysts 3.08+0.03 x10-3 s/mm2. Furthermore, there was statistically significant difference between benign lesions (haemangioma and cysts, 2.36+0.43x10-3 s/mm2), and malignant diseases (HCC and secondary tumors, 1.52+0.58x10-3 s/mm2), t=5,6, p<0.01. Conclusion: DWI technique could be helpful in defining the focal liver lesions.
Positron emission tomography/computed tomography in patients with cancer of unknown primary origin
Authors: Lucic S.M. , Lucic M.A. , Peter A. , Jovanovic D. , Vucaj-Cirilovic V.
Published: March 2010

Cancer of unknown primary origin is not an uncommon clinical state, usually accounting for 2%-7% of all cancer patients. Material and methods: Positron emission tomography and computed tomography (PET/CT) was performed in 17 patients with histologically proven metastatic tumors of unknown primary and negative or inconclusive conventional diagnostic procedures. Results: The study included 17 patients (8 male and 9 female) age from 42 to 76 years. PET / CT has pointed out the probable localization of primary tumors in 10 patients. According histological diagnosis of carcinoma of unknown origin, most common is adenocarcinoma (64.71%). Origin of the primary cancer was found in 72.73% patients with adenocarcinoma 66.67% of respondents with squamocelular carcinoma and 50% of respondents with low differentiated carcinoma. Location of primary cancer was not found in 41.18% of the respondents, including patients with mucinous adenocarcinoma and patients with melanoma. Conclusion: FDG PET/CT demonstrates very good whole-body imaging method in evaluation of patients with unknown primary carcinoma.
Imaging capabilities in upper urothelial malignancies differentiation
Authors: Markovic B.B. , Maksimovic H.M. , Pejcic T. , Plesinac V. , Stojadinovic M. , Civcic M.
Published: March 2010

Aim of our study is to analyze sensitivity and specificity of imaging procedures in characterization upper urothelial malignancies, according to algorithm suggested by American Urology Association. Material and methods: We analyzed 242 patients with kidney tumor masses who had been operated during 2006/2007 at Urological clinic in Belgrade. Due to pathohistological exam 210 patients had kidney parenchyma and 32 patients upper urothelial kidney tumor. Results: According to tumor stage, computed tomography was sufficient and definitive diagnostic tool concerning both renal epithelial and upper urothelial malignancy. Only in four cases 1.60% (4/242; CT in 3/4, MRI 1/4) preoperative site of origin was different from histopathology findings. This mislead to inappropriate surgery plan. Conclusion: Familiarity with limitations and capabilities of imaging modalities is crucial for appropriate diagnosis. It should respect algorithm but has to be individual adapted.
Kako prevenirati tkivno urastanje i inkrustaciju metalnih stentova urinarnog trakta kod bolesnika sa osnovnom malignom bolescu male karlice?
Authors: Markovic Z. , Masulovic D. , Markovic B. , Anojcic P. , Mladenovic A.
Published: March 2010

At the current level of stent application in urology each irreversible urostasis contraindicated for surgical therapy implies consideration of indications for metal stent insertion. Stent incrustation which leads directly into a new uroobstruction is a characteristic complication of this method. Available experience in different uroobstructive conditions has shown that very different clinical aspects of stent usage may directly determine the possibility of their incrustation. Stent incrustation may occur in the early postprocedural course or several months later. After that, prevention of stent incrustation starts with postprocedural evaluation, selection of the stent type, and it is subsequently continued by insertion technique and lasts practically permanently after the insertion (infection control, promotion of diuresis and maintenance of normal urodynamics). Authors present own experianse in clinical application of metal stents in uroradiology strictures for period of last 15 years.
Combined hormono-radiotherapy in treatment of locally advanced prostate cancer
Authors: Radosevic-Jelic Ljiljana , Stankovic V. , Josifovski T. , Dozic M. , Borojevic N. , Tulic C.
Published: March 2010

Numerous questions regarding combined hormono-radiotherapy in the treatment of locally advanced prostate cancer still remain open. We present results of combined treatment in 133 our patients with locally advanced prostate cancer. All patients received hormonotherapy as neoadjuvant, concomitant with radiotherapy (tumor dose range 65-72Gy), and adjuvant. In six months follow-up time, complete regression (CR) was noted in 120 patients (90%), partial regression (PR) in 6 (4,5%), stabile disease (SD) in 2 (1,5%) and progression of disease (PD) in 5 patients (4%). In mean follow up time of 17 months (6-77), 13 patients relapsed. Five-year time to progression was 70%. Five-year disease-free interval for CR patients was 70%. At the date of last control CR was noted in 116 patients (87%), PR in 2 patients (2%), SD in 7 patients (5%), and 8 patients (6%) had progressive disease. Second malignancy was noted in 4 patients. Multidisciplinary studies directed towards the optimisation of combined treatment are ongoing. There are no definitive conclusions.
Postoperative radiotherapy of cervival carcinoma: Treatment results and analysis of prognostic factors
Authors: Plesinac-Karapandzic V. , Borojevic N. , Milosevic Z. , Markovic B. , Nikitovic M. , Plesinac S.
Published: March 2010

The purpose of the study was to evaluate the efficacy of postoperative radiotherapy (RT) and to investigate prognostic factors for early-stage cervical cancer patients. We reviewed the medical records of 162 cervical cancer patients treated by RT during 2003 year. RT included 30- 45Gy of external photons to pelvis in 12-25 fractions. Brachytherapy with 192Ir was delivered in 3-5 fractions to a dose of 27-32 Gy. The mean age was 49 years (range 27-71). Majority of patients 130 had Stage Ib. Radical hysterectomy with lymphadenectomy was performed in 122pts. and simple hysterectomy in 40 pts. The 5-year actuarial overall survival (OS) for all patients was 92,6% and disease-free survival (DFS) was 90,9%.There was statistically significant differences in OS and DFS in pat. with positive vs. negative pelvic lymph nodes; tumor 4cm vs. tumor <4cm; positive vs. negative surgical margin/residual tumor (p<0,05). Late GIT complications were determined in 35,8% and UT in 12,3%. In conclusion, postoperative radiotherapy has achieved high-satisfactory survival with acceptable complications. The survival benefit was less evident among patients with positive lymph nodes, tumor > 4cm and positive surgical margin/ residual tumor.