Abstract Control of nanophenomena in geological formations, fields fluids and production equipment in oil and gas industry are known as technologies of their regulation (nanotechnologies). Some ways for increasing of oil-andgas recovery are described: regulation of injected reagents ionic component, influence on the oil-and-gas layers by physical fields resulting in change of balance in system «oil-gas-water-rock», and others nanotechnologies which use for increases efficiency of oil-and-gas reserves operation (include gashydrate). The analysis of the nanomineral complexes geometry change in oil formation is carried out. Our studies reveal that the control of the above nanocomlexes can increase oil recovery of oil field due to change of the capillary hysteresis value and clay minerals specific behaviour at water flooding. Classification of ?OR/IOR-nanotechnologies by their effect on oil reservoirs, examples of laboratory and field test some ?OR/IOR-nanotechnologies efficiency estimations, prospects of oil&gas nanoindustry are given. 1. Introduction Oil has entered into our life so deep that cost of a barrel of oil is announced daily alongside with common weather forecast. And it is clear - power engineering and petrochemistry became the basis of well-being of many countries and their citizens. Therefore, the world society is interested in good prospects of oil extraction. However, these prospects depend significantly on amount of financial investments into fundamental researches of properties of oil reservoirs and oil-field fluids, into creation of new efficient technologies and elements of oil-field equipment. There is much information about special features of processes of reservoir drive, but conventional understanding of a role of fundamental research in these processes has been not developed yet. It is enough to mention that the basic equations of processes of oil displacement from oil stratums are traditionally grounded on foundations of continuum mechanics, in which so-called «boundary phenomena» (which indeed are nanoscale phenomena) are considered as negligible. These equations work well in pipe hydraulics, in high-size filters and rectifying columns, in high-permeability stratums. As to low-permeability oil-saturated porous mediums, during the last years it is became more and more clear that high recovery factor can be achieved only when decreasing capillary forces keeping oil in rock pores. Here, fundamental knowledge in the area of physics-chemistry and nanomineralogy, and ability to use this knowledge for recovery factor calculation are required. Why «nano»-mineralogy? Because structural elements of surface of pores have nanoscale characteristic dimensions. We have solid grounds to use the cult prefix «nano» here. Textbooks on physics of oil and gas stratums considered physical-chemical problems of oil recovery from the point of view of physics, for example, they mentioned influence of capillary forces. But, at the same time, formulas and schemes for calculation of a recovery factor implied use of continuum mechanics instead of physics and chemistry. In general, problems leading to a low recovery factor were mentioned (alongside with problems of insufficient oil resources), but correlation of nanoscale effects with macro-dimensional volumes of oil was not taken into account. But after all, this situation is similar to samples from classical mathematics, when one small parameter significantly influences not only a solution of a certain equation, but also its principle features. General modern interest to oil is based on research of macroeconomists (N. D. Kondratyev) in the area of technological foundations of economic crises. First of all, people create a science connected with new scientific prospects; this period lasts 10–15 years. After that, the stage of development of prototypes takes place - during the next 10-15 years. At last, the third stage - penetration of new technologies into real economy - takes the same time. In the Figure 1, dynamics of innovations in different technological areas (according to Kondratyev's cycles of economic activity) is represented.

Abstract Production of residual reserves (1–1.5 billion m3) under low formation pressures in West Siberia as well as withdrawal of a strained gas from watered areas is always a trouble. Traditional methods used today to develop such fields are characterized by low hydrocarbons (including stained gas) extraction efficiency and production cost rise that even affects the reliability of a gas producing company operating performance. Herein, results of theoretical researches and laboratory tests on the displacement of natural gas through the injection of nitrogen into the formation are presented. Qualitative and quantitative data demonstrating the in-situ injection of nitrogen at the Medvezhye field are also shown. Introduction At the final stage of gas field production there is a time when the pressure of residual gas in the productive layer is about 5 MPa, not more. In the case of bottom water intrusion the rate of pressure reduction slows down, that compensates partly the negative subsequences of the water drive process. So, some or less significant zones of the residual gas resources could be trapped behind the gas-water front. But, in many cases the share of trapped gas and low pressure gas could be such significant (tens of percents from the gas-saturated portion of reservoir), that it is necessary to apply some additional arrangements for those losses reduction. According to VNIIGAZ estimation, the residual low-pressure gas resources at the biggest gas fields in Western Siberia (Medveje, Urengoy, Yamburg) in the case of those fields just depletion will exceed 1.5 billion m 3 and trapped gas makes the most part of those losses – 75%. One of the way to increase the gas fields development efficiency is the reduction of hydrocarbons losses including those from trapped and low pressure gas in the productive layer. This is important task both from scientific and practical point of view. The results of seam inundation process investigations at the conditions of noncompensible hydrocarbons production, made in VNIIGAZ, evidence that even in homogeneous porous medium trapped gas is distributed not uniformly. For example, the data obtained with topographical methods, evidence that at Medveje field, where the average gas saturation is about 15–20%, there are zones where the real gas saturation is much more and could exceed the hydrodynamic mobility edge. These data obtained stimulate further investigations for the method development, which could provide the residual trapped gas resources involvement into their active production. BLOCK 3 - - FORUM 14 17 IFINAL STAGE OF NATURAL GAS FIELD DEVELOPMENT We had the intentions to develop the method, which is not based at the both big bulk of associated water and gas itself production (the correspondent information could be tak

Abstract. A consistent screening technique was developed to quickly evaluate the Improved Oil Recovery (IOR) potential of oil reservoirs. This evaluation consists of: checking reservoir's geological /production data for consistency, selection of technically feasible IOR processes, performance projection for the selected IOR processes, and generating a complete IOR report, containing all the production and injection plots. A software (PRIzeTM) was built based on this screening technique. This computer program generates information on the feasibility of IOR processes based on the average reservoir parameter values, the driving mechanisms, and the current understanding of IOR processes; analytical models are used for most predictions. These analytical models have been selected by distilling a significant number of forecasting methods in the open literature. This paper discusses the PRIzeTM-based experience in evaluating the potential of waterflooding, chemically assisted waterflooding, miscible gas injection (CO2, hydrocarbon, and N2), and thermal recovery processes (steam drive, SAGD and in-situ combustion). Options for using horizontal wells in conventional oil recovery and IOR processes are also addressed. Although PRIzeTM is not a numerical simulator, it allows one to establish, to a first order approximation, the likely performance for determining economic viability of a given IOR process. can, in turn, be used for risk and economic INTRODUCTION analyses. The screening criteria are based on Selection of Improved Oil Recovery statistics of successful commercial IOR (IOR) process is extremely important projects worldwide. All reservoir because, as a rule only 10% of the total IOR engineering equations and algorithms used pilots have been developed into to generate the oil recovery forecasts of semi-commercial and commercial individual IOR schemes have been operations. This figure was generated from established by distillation of a significant a 2-decade statistics on IOR pilots in number of forecast methods existing in the USA1,2. Many of IOR field pilots have open technical literature. When necessary failed because the most appropriate IOR they were improved using our own method was not chosen. To assist in this, a experience. specialized software, PRIzeTM, was created With the exception of steam in 1992, and has been continuously assisted gravity drainage (SAGD), the updated and improved since. Our intent screening and the prediction calculations are here is to present the technical content of performed only for IOR methods, which are this software. proven via commercial operations. A general IOR method, applicable However, we included SAGD because of an to the complete range of field situations, impressive success in a semi-commerci

Abstract. The Offshore Mexican hydrocarbons production area is located in the south of the Gulf of Mexico. In this region around 200 platforms and 1800 km of pipelines have been installed, producing 2.1 mmbpd (334 km3/ d) of crude oil and 1100 mmscfpd (31 Mm3/d) of gas. These facilities suffered the effect of two very strong hurricanes named Roxanne and Opal, on October 12th, 15th, 16th and 17th, 1995. Consequently, the structural integrity and remaining life of those facilities have been assessed, according to API-RP-2A Section 17. The assessment mentioned before is presented in this paper, involving the following tasks: metocean criteria review, subsea and surface inspection work, and analytical structural simulations. INTRODUCTION Petróleos Mexicanos (PEMEX) operates approximately 190 offshore platforms in Campeche Bay, in southern Gulf of Mexico. The total production of the area (around 2 100000 BPD of crude oil and 1100 MMSCFPD of gas) is driven through approximately 1800 km of pipelines that deliver oil and gas for local consumption and heavy crude for exportation. The geographic characteristics of the region makes it less vulnerable to hurricanes, but more exposed to moderate and strong winter storms when compared to the governing environmental conditions in the northern Gulf of Mexico (US area). This derives in milder overall meteorological and oceanographic (metocean) conditions. Most of the structures installed in Campeche Bay are conventional jacket type platforms clustered in complexes that concentrate housing and all the process equipment to handle production from local and satellite drilling platforms. Eight-legged jackets are commonly used for different services and tripods are used mostly as well protectors and for bridge support. Last year the Campeche Bay suffered the effect of the two back to back hurricanes Opal and Roxanne. The latter was more intense and exhibited a highly anomalous behavior that induced extreme forces on the structures and generated the necessity of platform and pipeline requalification due to the damage found. For that purpose, PEMEX and Instituto Mexicano del Petróleo (IMP) created a special engineering group to take on the assessment process, knowing that despite API-RP-2A (WSD) Section 17 draft had been issued, hard work was required to refine such methodology and to adapt it to the local environment. The special group is coordinating the whole assessment process, as well as the two engineering firms hired to perform the structural analyses. The PEMEX/IMP group and the engineering firms have worked together with several experts on different fields to reach the aimed goal. Right after Roxanne took place,

Abstract. The oilfield St. Ulrich-Hauskirchen, part of the Vienna Basin, was discovered in the late thirties, located approximately 50 km north of the city of Vienna. The main oil bearing formation is a naturally fractured sandstone, with an IOIP of about 22 million metric tons. Since the start of development in 1941, a total of 235 production and injection wells have been drilled and for secondary recovery a water flooding project was implemented in 1953. In the beginning of the nineties the economic limit of production had been reached and therefore alternatives for further improvement of ultimate recovery had to be considered. Oil recovery factor by that time was approx. 25%. Reservoir studies have led to the assumption that there could be a considerable amount of ‘attic oil’ left in the fracture system, which cannot be recovered by the water flooding process. Injection of nitrogen gas was considered as a feasible method to provide the required gravity drainage effect. The first pilot tests were conducted in 1992, within a few days an increase in oil production and a decrease in water cut was observed in some of the adjacent wells. Due to this promising result a full scale injection program was implemented in 1994. As of June 1997 about 45000 metric tons of incremental oil could be recovered. Today approx. 40% of total oil production of this field can be allocated to this EOR process. Since the start of the project the average water cut has decreased from 95% to 89%. In addition water injection could be reduced by half of the volume which in turn has a significant impact on the operational costs of this marginal oil field. Right now the nitrogen injection project can be classified as technically and economically successful. INTRODUCTION Since January 1994 nitrogen is injected into the naturally fractured Flysch reservoir of the oil-field St. Ulrich-Hauskirchen to extend fieldlife and further improve recovery. Due to the injection of nitrogen production rates were increased from about 2000 tons per month up to 3300 tons per month. As of June 1997 about 5.10 MM Sm3 of nitrogen were injected, total amount of incremental oil produced is 45 O00 tons. Due to a number of additional measures costs per unit oil produced were reduced dramatically (i.e. reduction of producing wells, reduction of water injection volumes, reduction of gross production, abandonement of water treatment facilities). DESCRIPTION OF FLYSCH RESERVOIR Figure 1 is showing a structure map on the top of the Flysch formation. The Flysch reservoir of the oilfield St. Ulrich-Hauskirchen is a buried mountain summit of the old land surface which formed the Alpine Carpathic chain before the collapse of the Vienna Basin. This distinct structural high which stretches from east to west is cut by several north south trending valleys. The

Abstract. Depletion gas drive, gravity drainage, aquifer inflow, and compaction are identified as naturallyoccurring production mechanisms in heavy-oil production. These are supplemented by potential gradients developed during flooding operations. Flooding processes usually are thermal in character: hot-water, steam, and in-situ combustion. Production mechanisms during thermal recovery processes include: displacement; thermal expansion of fluid and minerals; distillation, transport, and condensation of light components: incrementai gas drive with increasing temperature: decomposition, fluid-fluid, and fluid-solid reactions: and changes in fluid-fluid and fluid-solid interfacial forces. Each of these alters the local potential field, and thus are mechanisms affecting flow. The mechanisms resulting in ‘foamy oil’ behavior (low produced gas/oil ratios, and apparently high oil mobilities and production rates sustained for prolonged periods of time) remain unexplained. The use of horizontal and conventional wells in different arrangements does not create new production mechanisms. Steam is the most common injectant, usually started as cyclic for early income generation and switched to flooding to optimize gains. Primary production using horizontal wells (or high productivity index completions) may be commercial in areas of high oil mobility. 1. INTRODUCTION The term ‘heavy oil’, or viscous crude oil, does not have a universally-accepted definition. Briggs et al.' suggested that heavy oils be defined as those having no less than 100 cp (100mPa. s) at ambient reservoir conditions. That is the working definition used in this article. All reservoir mechanisms present in light oil reservoirs are common to reservoirs containing heavy oils. Since most reservoirs (including tar sands deposits) have a maximum permeability of about 10000 md (10000 pm2), an approximate upper bound to the mobility of heavy oils is 100 md/cp (100 pm2/mPa s). This combination of high permeability and low viscosity is not common. A more representative upper bound would be about 10 md/ cp (10 pm2/mPa s), which is near the lower bound of economic attractiveness even for light crudes. Additionally, heavy oil deposits are usually shallow (are at relatively low pressure). As a result, essentially all heavy-oil production is based on an improved recovery process. The improved recovery processes based on injectants, the flooding processes, enhance the natural driving forces in the reservoirs. Other processes use wells with high productivity indices (e.g., horizontal wells, downhole heating, hydraulic fracturing) and make use of natural forces existing in the reservoir to not supplement the forces in the reservoir in significant ways, are stimulation-type applications. Here we take an extended view that the use of horizontal instead of conventi

Abstract. Oil-gas-condensate fields of the Precaspian Depression (PD) started to play an important role in the ex-USSR petroleum industry at the beginning of Eighties' after the discovery of giant formations Astrakhan, Karachaganak, Tengiz. The common characteristic features of presalt formations of the Precaspian Depression are as follows: large productional thickness-up to 2 km; high vertical compositional gradients of reservoir fluids; large depth of formations (5–7 km) and significant deformation of the reservoir rocks; high pressure and temperature, subcriticai and near criticai phase behaviour of reservoir fluids; high concentration of non hydrocarbon components (up to 19 mole% for carbon dioxide and up to 28% for hydrogen sulphide); high content of condensate liquid in petroleum fluids and low recovery with pressure depletion, necessity for pressure maintenance; very low values of average permeability, large partition of media with thin pores; large amount of trapped hydrocarbon liquids in gas caps; carbonate reservoir rocks with a high level of heterogeneity on ali the scales. New methods for study of these unique reservoirs are developed: analytical 3-D model for gas injection into heterogeneous reservoirs; analytical model for characterization of heterogeneity from field test data; phase behaviour theory with capillarity and wettability; theory of compositional grading with the geothermal gradient. 30 years production history of the Orenburg field (PD) was used for characterization of the ‘new’ fields. Multivariant comparative study of different EOR methods shows that the most prospective recovery method for PD fields is gravity stabilized injection with the use of non-hydrocarbon gases. INTRODUCTION Oil-gas-condensate fields of the Precaspian Depression (PD) started to play an important role in the Soviet petroleum industry at the beginning of the Eighties after a very successful exploration in the Northern Board of the PD and the discovery of large reserves in Astrakhan (Russia), Karachaganak and Tengiz (Kazakhstan) formations (Fig. 1). Presently the giant gas condensate fields Astrakhan and Orenburg are of great importance in the Russian gas industry. Karachaganak is the largest gas condensate field in Kazakhstan (second in the World) and Tengiz is the largest oil field in Kazakhstan. Later were discovered reservoirs of a medium size-Dzonadzol, Teplovsko-Tokarevskaja Group, Kenkijak and Urekhtau. The first gas-condensate-oil field of the PD (Orenburg) was developed starting in 1972. The huge experie

Abstract. More than half of the Romanian territory is covered by sedimentary rocks, deposited in former sea basins, with hydrocarbon source and accumulation conditions. Since 1857 when the first oficial oil production was recorded in Romania (over 136 years of history) important oil and gas quantities were produced and a huge experience in this field has been accumulated. All the reserves ever discovered in Romania exceed 860 million tons, or 6.4 billion bbl and 1600 billion SCM, or 57 trillion SCF and the cumulative production by 01.01.93 was 650 million tons, or 4.82 billion bbl and 1070 billion SCM, or 38 trillion SCF, oil and gas, respectively. The prospects for new reserves are connected in Romania with the discovery of new reservoirs, in extension of the existing ones and in deeper formations in difficult geological and access conditions. Some oil reserves may be obtained by increasing only by 3% the actually estimated ultimate oil recovery, (which averages 31.3%). With only 3% of the ultimate recovery the reserves extend the actual production by 12 years. Therefore, the methods for increasing oil recovery (IOR), conventional (water and gas flooding) and special (EOR) are more and more considered for the oil potential of the country, of course from now on, only under economic conditions. Today, the Romanian Oil Corporation with the state capital Petrom R.A. is totally open to cooperation by foreign companies in both the fields of exploration and enhancing of oil recovery. 1. INTRODUCTION Currently 465 structures are in operation in Romania for oil production and 430 structures for gas production. The conventional methods, water flooding and gas injection were initiated in 1950 and by the end of 1992 they were applied on 181 structures (175 water + 6 gas). All processes are based on the studies and supervision of the Institute for Research and Technology (ICPT) Campina, a subsidiary of Petrom R.A., Romanian Oil Corporation. The EOR methods started to be studied by the 1950s, when the mechanism of oil displacement became clearer and the influence of fluid mobilities was better understood. The first idea was to increase the water viscosity by molasses (too expensive) and by sodium silicates (unsuccessfully). Polymer use was considered as a big hope and the first experiments in the laboratories were done with partially hydrolized polyacrylamides. At the same time, studies were done on the use of surfactants and CO, for miscible processes. Another big hope was in 1964, when Gogarty published Maraflood and the micellar solutions appeared as a * Institutul Cercetari si Proiectare Tehnologice (Institute for Research and Technology). key to oil recovery increase. The chemical flood and miscible displacement of oil by CO, was studied and experimented in the lab and in the field by ICPT C

Abstract. The objective of this paper is to summarize the current status of miscible flooding technology with a focus on reservoir behavior. The results are largely based on Exxon's broad experience in both research and commercial applications of miscible flooding using a variety of miscible solvents, including CO, hydrocarbons and nitrogen. Pore-level mechanisms of miscible displacement are defined, discussed and related to performance observed in field projects. Representative commercial projects are reviewed with respect to both performance to date and predicted performance. Special attention is given to the evaluation of current capabilities of predicting performance of miscible floods through use of computer simulation. Finally, important technology needs are identified and discussed. 1. INTRODUCTION There is currently a large number of commercial miscible flooding projects in the U.S. and Canada, which represent a total investment on the order of 10 billion U.S. dollars. Most of these projects were initiated in the early 1980's without the benefit of much commercial miscible flooding experience. The investment decisions at that time relied upon laboratory data, reservoir simulation studies and a limited amount of information from field pilot tests. Many of these commercial projects are now at a stage where they have progressed far enough and have enough history to allow meaningful evaluation of overall project performance. Therefore, it seems appropriate at this time to evaluate performance-to-date of these commercial projects. The lessons learned from such an evaluation should be useful in continued management of current projects, as well as in design of future miscible flooding projects. The specific objectives of this paper are to address the following questions: What do we know about how the miscible flooding process works? What is industry's level of activity in field applications? How have current field projects performed? What can be learned from those projects? What are the basesltechniques for predicting performance of new projects? How can we reduce risks associated with investment decision making for new projects? - - J. And finally, what research is needed to improve the miscible flooding process and to reduce risk? In developing answers to these questions, we utilized a variety of information sources. Probably the most important was Exxon's first-hand experience in designing and operating miscible floods. Another important source was experience from participation in miscible flooding pilots and projects operated by others. We also utilized the published literature. Exxon is currently operating, or has an interest in, 35 projects involving CO, hydrocarbon and nitrogen solvents. The total incremental produ

Abstract. The paper describes Statoil's experiences in drilling extended reach (ERD) wells, primarily to serve remote parts of widespread reservoirs, experiences in drilling horizontal and complicated wells, specially designed for optimal drainage of complex reservoirs. Several world records in extended reach drilling, conducted from the Statfjord ‘C’ platform are summarized. The latest ERD well drilled has a horizontal reach of 7290 m. Included are also the latest plans of implementing these new techniques in developing new fields. A brief summary is given of achievements within the industry with other special wells, such as dual laterais, snakey, multiple arm etc. Furthermore the paper describes the technical challenges of drilling complex wells and how planning is carried out to cope with these challenges. Some limitations to the drilling are highlighted and solutions to drilling problems related to torque, drag, buckling, hole cleaning and surveying are given. Cost-Benefit considerations regarding ERD, horizontal and complex wells are discussed. Reducing number of platforms and/or eliminating subsea templates due to ERD wells are considerable cost reducing factors. Reducing the total number of wells from a platform due to horizontal and/or complex well profiles is another major cost reducing factor. INTRODUCTION The oilfields developed in the 1970s-1980s had relatively significant limitations to the drainage area from each platform. The Statfjord and Gullfaks fields were initially planned to be developed with maximum 60 degree inclination wells, resulting in a maximum horizontal reach of 3000m at the Statfjord field and 2100 m at the Gullfaks field reservoir depths. To drain the fields in an optimum way based on the technology available, called for three GBS platforms on each field. Developments and improvements in drilling technology, engineering research and field experiences have, since then, pushed the limits for available well profiles and horizontal reach distances dramatically. The purpose of drilling extended reach, horizontal and complex design wells is to drain the field in the most cost effective way. The use of these new techniques can make old nonprofitable fields profitable, prolong an existing field's economic life and make new questionable field discoveries worth developing. Today's techniques enable the reservoir, dip angles, faults and structural geology to be design factors for optimal placement of the wellpath. STATO1 LS EXP ER I EN C ES/ACH I EVE M E NTS Extended reach wells The definition of an extended reach well is a well with a measured depth to true vertical depth ratio (MDITVD) greater than 2.0. A mega reach well has a MD/TVD ratio greater than 3.0. The import

Abstract. Summarized results of EOR methods application in the U.S.S.R. are presented in the paper. On the basis of comparative analysis of actual data, the probability of successful EOR methods application have been evaluated for specific conditions, and the most preferable geologic parameters have been highlighted. Some peculiarities of EOR methods application in domestic oil fields have been considered, including those in Western Siberia. The results of multivariant prediction of EOR methods application in the U.S.S.R. are presented. Résumé. Cette communication résume les résultats de l'application des méthodes de RAH en U.R.S.S. Sur la base d'une analyse comparée de données réelles, on évalue la probabilité de succès de I'application des méthodes de RAH dans des conditions spécifiques et on souligne les paramètres géologiques préférables. On observe quelques particularités de l'application des méthodes de RAH dans les gisements pétroliers soviétiques, y compris ceux en Sibérie occidentale. On présente les résultats de la prévision multivariante dans l'application de méthodes de RAH en U.R.S.S. 1. INTRODUCTION The method of artificial reservoir flooding is the main one used for U.S.S.R. oil field development; it covers about 95% of domestic total oil production. To date, the design oil recovery factor in the U.S.S.R. due to this technique is higher than in other world oil-producing countries but it still does not exceed 40%. Recent years have been characterized by a constant and considerable structural deterioration of oil reserves. Oil fields with low reservoir permeability, high viscous oils and more complicated geological structures are now put into operation. Under such conditions a conventional flooding technique cannot always provide for high oil recovery factors. In the Soviet Union as well as other countries, more attention is paid to the problem of searching for and implementing new reservoir stimulation methods for a significant increase of development efficiency. Lately the scope of thermal, gas and chemical EOR methods in the country is constantly increasing. 2. STATUS OF EOR TECHNIQUES APPLICATION To date in the U.S.S.R. all the known EOR techniques are being examined and applied, some of them for commercial oil field development. Tables I and II present some generalized data concerning the application scope of thermal, gas and chemical techniques. EOR techniques were implemented in 354 areas of 173 domestic oil fields in the past 25 years. Presently 247 areas in 157 oil fields are in operation. It is clear that in ten years the total number of areas increased more than four times though the ratio of the number of operating areas to the total number decreased from 0.8 to

Abstract. Technical criteria, economics, and the availability of injection materials limit the application of miscible flooding to select reservoirs. A key element in further evaluation of these reservoirs for miscible flooding potential is an assessment of the uncertainty in oil recovery predictions. The degree of uncertainty that can be tolerated in a performance projection depends on local economic conditions and, as a result, varies from one project to another. This paper is concerned with the causes of uncertainty in miscible flood evaluations. It describes what ideally needs to be accounted for in a performance prediction and discusses the practical limitations to achieving this ideai. It identifies key data that contribute to uncertainty in performance projections and discusses how these projections are affected both by the degree of understanding of some important displacement mechanisms and by the limitations of reservoir simulators. Examples are given to illustrate the sensitivity of projections to data and mechanisms that often are poorly known. Measures for reducing uncertainty in predktions are described. Résumé. Des critères techniques et économiques et la disponibilité des produits injectables limitent à certains réservoirs sélectionnés le champ d'application du déplacement miscible. L'élément clé pour une meilleure évaluation du potentiel du déplacement miscible pour un réservoir donné est l'estimation du degré d'incertitude affectant les prévisions sur la récupération du pétrole. Le degré d'incertitude tolérable dans une prévision de performance dépend des conditions économiques locales et, par conséquent, varie d'un projet à l'autre. Cette communication traite des causes de l'incertitude dans les évaluations du déplacement miscible. Elle décrit ce qui doit être pris en considération pour une prévision de performance idéale et discute les limites pratiques affectant la réalisation de cet objectif. On identifie les données clés qui contribuent à l'incertitude dans les prévisions de performance et on discute comment ces prévisions sont affectées à la fois par le degré de compréhension de certains mécanismes de déplacement et par les limitations des simulateurs de réservoirs. Quelques exemples illustrent la sensibilité des prévisions à des données et des mécanismes souvent mal connus. Des méthodes susceptibles de réduire l'incertitude des prévisions sont également décrites. INTRODUCTION This paper is concerned with the causes of uncertainty in predictions of miscible flood performance. Predictions of the amount and rate of oil recovery by miscible flooding must account for (1) the extent of miscible sweepout, (2) unit displacement efficiency or the reduction in oil satu

Abstract. Characteristic features of a Tension Leg Platform (TLP) for deepwater will be examined. Aspects of general configuration and special hardware, including tension leg components and risers, will be considered. Recent developments in design and analysis methodologies, and possible impacts on the deepwater TLP, will be reviewed. The paper will postulate certain aspects of a deepwater hydrocarbon development project so that the process of planning a project and synthesizing a system can be illustrated. The conceptual design features of deepwater TLPs will be described based on these premises. Results of recent research and design technique development will be discussed in addition to experience gleaned from the Hutton Field Development Project which is currently in progress. Technical lessons of recent work, including establishing environmental criteria, detailed assessment of dynamic and hydrodynamic loadings and strength analysis will be covered. Conclusions concerning the probable design qualities and range of applicability of tension leg platforms to deepwater hydrocarbon projects will be drawn. Résumé. On examine les caractéristiques d'une plate-forme à câbles tendus (TLP) pour des grandes profondeurs d'eau. On considère des aspects de la configuration générale et des équippements spéciaux, y compris les composants du système d'ancrage et les tubes prolongateurs. On passe en revue de développements récents dans les méthodologies de conception et d'analyse et leurs conséquences possibles sur les plates-formes à câbles tendus pour des grandes profondeurs d'eau. La communication présente certains aspects d'un projet de développement de gisements d'hydrocarbures à grande profondeur d'eau afin d'illustrer le processus de planification et de synthèse du projet. On décrit les caractéristiques conceptuelles des plates-formes à câbles tendus pour grandes profondeurs d'eau sur la base de ces hypothèses. On discute les résultats de recherches récentes et de développements dans la technique de conception à la lumière de l'expérience tirée du projet de développement du gisement de Hutton. On traite l'apport technologique de travaux récents, y compris la détermination des critères de l'environnement, l'évaluation détaillée des forces dynamiques et hydrodynamiques, et l'analyse structurelle. On tire des conclusions concernant les qualités probables de la conception et les possibilités d'applications de plates-formes à câbles tendus pour des projets de production d'hydrocarbures dans des grandes profondeurs d'eau. 1. INTRODUCTION 1 .I. Background A tension leg platform, or TLP, is an evolutionary form of semisubmersible, connected to anchors fixed in the seabed by vertical moorin

Abstract. The scope and constraints for enhanced oil recovery in the North Sea have been widely recognised. North Sea reservoirs are in general over-pressured and are highly permeable. They contain a 35–40 "API crude which exhibits a wide range of compositional variations. The present development of fields in the hostile environment of the North Sea does not permit a close spacing of wells which is in generai desirable for enhanced oil recovery. A review is presented of the theoretical and experimental laboratory studies and field test results aimed at optimizing recovery with various enhanced recovery methods. Laboratory studies and field test results indicate that for several major North Sea reservoirs, miscible gas injection may lead to higher recoveries than water injection. Miscible gases that are being considered are hydrocarbon gas and nitrogen. A miscible hydrocarbon gas drive test has already been initiated in the Statfjord reservoir of the Brent field. Laboratory studies have also indicated that the oil remaining after waterñood can be recovered by nitrogen injection, which may lead to very low residual oil saturations. Résumé. L'importance et les contraintes de la récupération assistée du petrole en mer du Nord ont été largement reconnues. Les réservoirs en mer du Nord ont en général une pression supérieure à la normale et ils sont très perméables. Le pétrole contenu dans ces gisements a une densité variant entre 35 et 40" API et est caractérisé par des variations de composition importantes. L'hostilité de l'environnement en mer du Nord ne permet pas le rapprochement des puits qui est généralement souhaitable pour la récupération assistée du pétrole. La communication passe en revue les études théoriques et expérimentales en laboratoire, ainsi que les résultats des essais sur le terrain, ayant pour but la maximalisation de la récupération du pétrole par diverses méthodes de récupération assistée. Les études en laboratoire et les essais sur le terrain ont montré que l'injection de gaz miscibles peut, dans plusieurs réservoirs importants en mer du Nord, conduire à des récupérations supérieures à celles obtenues par injection d'eau. Les gaz miscibles, dont l'utilisation est envisagée, sont les hydrocarbures et l'azote. Un projet d'injection de gaz miscibles dans le réservoir Statfjord du gisement de Brent a débuté. Les études en laboratoire ont aussi montré que le pétrole restant dans le réservoir après injection d'eau peut être en partie récupéré par l'injection d'azote, ne laissant que de très basses saturations résiduelles. 1. INTRODUCTION Of the remaining Western European oil reserves, about 93% is

Abstract. This work demonstrates how experimental and theoretical model studies of several fundamental reservoir parameters can be conducted for preliminary economic and technical designs of CO2 floods. Phase behaviour effects, minimum miscibility pressure and displacement efficiency in contacted areas of a reservoir are estimated for a real and a synthetic system. Also considered are the effect of relative permeability on minimum miscibility pressure calculated by a compositional simulator and the incrementai recovery of oil by CO2 floods from a waterflooded carbonate core. Résumé. Ce travail démontre comment, à l'aide des modèles, on réalise des études expérimentales et théoriques de plusieurs paramètres fondamentaux des réservoirs pour les projets économiques et techniques préliminaires de systèmes d'injection de gaz carbonique. On évalue l'effet du comportement des phases, la pression minimale de miscibilité et l'efficacité du déplacement dans les endroits accessibles du milieu poreux, pour un système réel et un système synthétique. On étudie aussi l'effet des perméabilités relatives sur la pression minimale de miscibilité a l'aide d'un modèle numérique, et la récupération additionnelle du pétrole par l'injection de gaz carbonique dans un milieu poreux Carbonat6 qui a été balayé par de l'eau. 1. INTRODUCTION As a first step in the design of CO2 floods, one must predict the recovery of oil in the swept portions of the reservoir,' i.e. the unit displacement efficiency. This requires consideration of the phase behaviour, transport properties and rock-fluid interaction of the C02-oil system. The primary objective of this paper is to show how laboratory experiments and computer models can be used to yield the necessary information for this crucial step. To do this the following three studies were conducted: Phase behaviour and fluid properties of C02-oil combinations were measured and modelled at pressures and temperatures likely to be operative in miscible floods. Slim tube experiments were conducted to aid in understanding miscibility conditions between CO2 and these oils. A displacement experiment on a restored core at reservoir conditions was conducted in order to help determine the extent of oil recovery by CO2 after waterñooding the core. The studies were performed on a light recombined reservoir oil and a defined ternary system consisting of various mixtures of n-pentane, n-hexadecane and CO2. The defined ternary system was chosen to aid in understanding mechanisms, and to provide a reproducible syste

In his introduction the CHAIRMAN pointed out that the papers presented were chosen so as to cover a wide range of reservoir engineering topics and can be grouped as follows. The first two papers are primarily concerned with investigations aimed at a more reliable characterization of the reservoir. The next two papers deal with methods for improving the interpretation and prediction of reservoir performance. The fifth paper highlights continuing efforts to increase our limited oil reserves. The first paper, on the use of advanced seismic techniques in field development, was presented by F. R. VAN VEEN. In answering questions from MR NEDERLOF (Shell Netherlands) regarding the resolving power of this technique under various conditions, Mr VAN VEEN explained that as a general rule, below 3000 m it becomes difficult to distinguish between gas and liquid, because the acoustic impedance characteristics of the pore fluid is overshadowed by those of the matrix and because the density contrast becomes small. Thus, distinguishing oil from water is even more difficult. Also, reservoir fluids are less easily recognized in carbonate reservoirs because there the grain-to-grain contacts are better and thus the acoustic velocity depends to a lesser degree on pore fill than is the case for sandstone reservoirs. In reply to a question from Mr DOBRE (Research Institute for Oil and Gas, Romania) it was stated that resistivity logs had been used only to determine the gas saturation, which, in turn, is required to correct both the density and sonic log readings to ‘virgin-formation’ conditions before calculating acoustic impedance. The second paper, on displacement experiments at reservoir conditions, was presented by L. CUIEC. This presentation gave rise to a lively discussion on the subject of wettability. Answering questions from Messrs DIMITRI (Research Institute for Oil and Gas, Romania) and BI- LARDO (University of Rome), Mr CUEIC stated that the data available did not permit a conclusion with respect to wettability variation within a given reservoir. In his opinion the best wettability measurements are those based on imbibition and capillary pressure. Of these two, the imbibition method is the easier one. The contact angle method is less suitable and the thermodynamic method is not feasible with rock-fluid systems. No attempts had been made to compare methods. Mr OFFERINGA (Shell Research, Netherlands) noted that wettability measurements had been carried out under normal pressure and temperature and questioned to what extent the results obtained are representative of the wettability of cores saturated and aged under reservoir conditions, bearing in mind e.g. that a decrease in pressure may lead to deposition of asphalte

Abstract. Mechanisms for enhanced recovery of oil are discussed. Two requirements are improvement of sweep and mobilization of oil. Improvements of sweep using polymers are described briefly. In order to mobilize oil its saturation must be reduced below that for waterÍìooding. This is accomplished by decreasing the viscosity of oil, using thermal or CO2 methods, or by reducing the interfacial tension between oil and water using surfactants or caustic. The mechanism of surfactant and causticflooding is reducing interfacial tension. Efficient displacement of oil from porous media occurs when low interfacial tensions are obtained. Although low tension is necessary for efficient displacement, it is not sufficient. For effective displacement, low tension must be propagated throughout the reservoir. Low tension can be destroyed by adsorption of some components or by dilution with reservoir fluids. It is crucial to understand the relationship between low tension and phase behavior. Interfacial tensions show definite dependencies near critical points on the phase diagram. These dependencies allow extrapolation beyond where tensions have been measured. Conversely, knowledge of behavior near critical points allows design of systems for which interfacial tensions are insensitive to dilution. Design and results for a surfactantflood in the North Burbank Unit are discussed. Also, results are given for improving sweep using polymers. Résumé. On étudie les mécanismes de la récupération assistée du pétrole. Les deux objectifs en sont l'amélioration du déplacement et de la mobilisation du pétrole. On décrit brièvement l'amélioration du déplacement par des polymères. Pour mobiliser l'huile, il faut réduire la saturation en huile au-dessous de celle de l'injection d'eau. Ce ci sera réalisé soit par réduction de la viscosité de l'huile per des méthodes thermiques, ou par l'injection de gaz carbonique, soit par réduction de la tension interfaciale entre l'huile et l'eau au moyen de tensioactifs ou l'injection de soude. Le mécanisme du déplacement par des tensioactifs ou de la soude est la réduction de la tension interfaciale. Un déplacement efficace de l'huile du milieu poreux s'effectue quand on obtient des tensions interfaciales basses. Bien que des tensions interfaciales basses soient nécessaires pour un déplacement efficace, elles ne sont pas suffisantes. Pour un déplacement efficace, il faut que la tension interfaciale basse soit propagée à travers le réservoir. La tension interfaciale basse peut être détruite par l'adsorption de quelques composants ou par dilution dans les fluides du réservoir. I1 est indispensable de comprendre la relation entre la tension basse et le comportement des phases. Les tensions interfaciales montrent des dépenda

I am grateful for this opportunity to address the participants to the Congress on behalf of the delegation of Soviet oilmen; I would also like to congratulate those present here and especially the organizers of the 10th World Petroleum Congress-the Romanian organizing committee-with the opening of this important forum and to wish all of you fruitful work. If we take a retrospective look at the history of commercial oil production and try to ascertain the role played by oil in the development of productive forces of the society, there is every reason to call our 20th century a century of oil rather than a century of atomic energy, outer space or cybernetics. The tremendous growth rate of oil production is best illustrated by the 25 billion tons of oil produced over the past decade-makes half of all oil produced throughout the entire history of the industry. For a quarter of a century (1951-1975) world consumption of energy resources trebled; during the same period oil consumption increased five-fold and its share in the world energy balance rose from 24% to 43% and, recently, even to 45%. This was accompanied by vigorous growth of gross national product which, as is known, is directly proportiona! to indigenous oil consumption. However, long-term fuel and energy forecasts appearing in different countries in recent years state that although oil is one of the most widespread fossils (it is being produced by 67 countries), its reserves are by far more limited than, for example, those of coal, and if produced at increasing growth rate are subject to depletion in the next few decades. For evaluation of the present situation in oil production and consumption, one should bear in mind the following. Firstly, the oil recovery factor does not exceed on the average 40% of original oil-in-place in spite of continuous development of production technology and methods for increasing ultimate oil recovery. Investigations of oil recovery processes in natural reservoirs greatly advanced during the last decades. Calculation methods of oil displacement processes were also improved. However, complex physical and chemical phenomena during displacement, affecting ultimate oil recovery, have not yet been thoroughly learned. Therefore, we often cannot predict with confidence results of applying certain technology to oil production. Such natural factors as heterogeneity and fractures of reservoirs, and high viscosity of oil also handicap the increase of oil recovery efficiency. Introduction of new technology is a slow and costly process. Such methods as displacement by injection of solvents and thermal treatment are not yet widely used due to high production costs. Nevertheless, it is increasing the ultimate oil recovery that holds potential for considerable growth of recoverable reserves. For this reason the methods mentioned attract mo

Abstract. In assessing the logical methodology to anticipate, based on the preliminary technological data of a process, the modalities of evolutionary behaviour of the process under study, the paper analyses the operative technological consequences resulting from the introduction of classical logic in drawing up the casing programme and estimation of pipe creep in deep and ultra-deep wells. Résumé. En évaluant les possibilités de la méthodologie logique de prévision-basée sur les données technologiques préliminaires d'un procédé: les modalités de l'évolution du comportement du procédé étudié, l'exposé analyse les conséquences technologiques opératoires résultant de l'application de la logique classique i l'établissement des programmes de tubage, ainsi qu'à l'estimation du fluage des tubes dans les puits profonds et très profonds. 1. SOME ASPECTS OF FORMAL LOGIC IN THE SUBSTANTIATION OF DRILLING TECHNOLOG- ICAL ACTIVITIES 1.1. Generally speaking, the technological activities are complexes of antagonistic, conflicting interactions between the medium undergoing the change into an industrial product and the transforming technological process. Such activities may be grouped into two main classes : class of technologies to which the efficiency of the technological process A is evaluated by analysis of the characteristics (properties) of the industrial product B, properties confirming or refuting the efficiency of process A, and class of technologies to which we estimate the functional efficiency of product B to be obtained, by the transforming properties of the technological process A, confirming or refuting the functional efficiency B of the product. The plant type technologies are technologies in which evaluation of the transforming process efficiency is a post-process evaluation. Such technologies allow a dichotomic decision on the obtained industrial product. That is why the plant type industrial processes are called Mecanicist-Laplacean determinism processes. These technologies belong to technologies included in class (a) above. In drilling technologies, unlike these technologies, the evaluation of the functional efficiency of the obtained product B is a pre-process evaluation. Such technologies do not allow a dichotomic decision on the technological process A, and consequently a certain specification of the product B. That is why the industrial processes taking such a form are called conflicting type determinism processes. 1.2. Sentences (a) and (b) above are called technological sentences. To sentence (a) we associate the formulation 'we evaluate A by B, confirming or refuting it'. Similarly, to sentence (b) we associate the formulation: 'we evaluate B by A, confirming or refuting B'. To these sentences we associate the logical patterns: AXBXA (1.2.1) BXAXB (1.2.2) In the above

Never before has the need been greater and more pressing for the most efficient recovery of oil from existing reservoirs. World's discovered petroleum resources of light and medium oils are estimated at roughly 600 × IO9 m3, and the heavy oils at 400 × lo9 m3. At present, the world-wide average ultimate recovery from the light and medium oils is about 150 × lo9 m3, or roughly 25% of the in-place oil, while from the heavy oil deposits on the average only 10% of the oil-in-place will be recovered. Increasing demand and prices for petroleum and the desire of all people to have an adequate and continuous supply make it imperative that better technology be developed and applied. Research in the laboratory together with new and innovative applications in the field have demonstrated that substantially increased oil recoveries can be achieved economically-as has been exemplified by the reports delivered in this Panel Discussion and in the Panel Discussion No. 9, 8th World Petroleum Congress in Moscow. As you know, the theme of this congress is "Petroleum for the Welfare of Mankind". One would like to think that the theme for this Panel Discussion we had today is Increased and More Eficient Oil Recovery for the Welfare of Mankind. It is hoped that everyone will go away from this session thinking for always how to get more oil from reservoirs. There are two ways to increase crude oil reserves: discovery and enhanced recovery operations. The latter has some obvious advantages. Exploration costs and risks, which have been spiralling in the last decade, are absent in improved recovery schemes. We know where the billions of barrels of oil reserves are located. Also, discoveries require sizeable new investments, while new improved recovery operations utilise injection, production and transportation facilities that are for the most part already in place. Incidentally, the limitations on efficient recovery apply equally to new pools. All improved oil recovery methods have several basic requirements in common: the process must mobilise oil which would have been left as residual, i.e. increase the displacement efficiency. A substantially greater part of the reservoir must be contacted and displaced by the injected fluid, i.e. volumetric sweep efficiency must be increased. Any mobilised oil must be moved to the production wells and not be retrapped in other parts of the reservoir. Last and most important, the process must be viable economically. Experience has taught us that novel and more efficient recovery processes must be started in a reservoir as early as possible not only to increase the production and the ultimate recovery but also to reduce the operating life of a field thereby giving a more attractive rate of return on investment. It is fa