With high reservoir heterogeneity in terms of permeability and fluid properties, substantial amounts of oil are produced along with water. At water cuts higher than 96–98%, wells become uneconomic and are shut in or undergo water shut-off treatments. For this reason, shutting off water flow through thief zones in flooded reservoirs to prevent it from entering wells is one of the biggest technical challenges in enhancing oil recovery from mature multi-reservoir oil fields.
As the water cut increases, water flow through thief zones must be reduced, along with the amount of water entering the well, to enhance sweep efficiency in lower-permeability portions of the reservoir. A new technology employing polymer dispersed systems (PDS) shuts off formation and injected water flows by increasing flow resistance in thief zones. This process redistributes the energy of the injected water in the reservoir and helps produce oil from unswept zones, thus increasing flooding efficiency and oil recovery. PDSs do not require drastic changes in existing development systems and are employed together with conventional water-flooding methods.
This paper presents studies of basic and modified PDS versions for oil recovery enhancement adapted for conditions existing in the Vyatka area of the Arlan oil field containing poorly continuous reservoirs with lithofacies heterogeneity. This depleted area had a stable, high water cut.
The new method for enhancing water flooding efficiency using polymer dispersed systems presented in the paper selectively increases flow resistance in the thief zones of productive formations with a resulting increase in sweep efficiency.
Fedorenko, N. V. (BashNIPIneft LLC, RF, Ufa) | Lozin, E. V. (BashNIPIneft LLC, RF, Ufa) | Gareev, A. G. (BashNIPIneft LLC, RF, Ufa) | Nurov, S. R. (BashNIPIneft LLC, RF, Ufa) | Sibaev, T. V. (BashNIPIneft LLC, RF, Ufa)
The PDF file of this paper is in Russian.
Main object development unique Arlanskoye oilfield has exceptionally complex subsurface geology and contains heavy oil with increased viscosity. In section of terrigenous low carbonic thick series, eight productive layers have been identified. Taking into account the heterogeneity of the filtration-capacitive properties of these layers, in the section of the object, it is lawful to single out three packs. The upper one, uniting mainly of three highly permeable layers, predominantly sustained in area, middle pack with four thin middle-permeable layers, and a lower pack, represented by a single high-permeable layer with an extensive aquifer. The layers of the middle pack have deteriorated reservoir properties in comparison with the layers of the upper and lower packs, which influences the development of the multi-layered object. According to the results of development survey and geophysical studies, with the joint operation of packs of the object, the middle pack is characterized by the worst output, both qualitatively and quantitatively. These facts point to the unevenness of the coverage of the layers by waterflooding and the lesser degree of production efficiency from the middle pack. To assess the localization of current oil reserves in the conditions of a multi-layered object, a deep geological and field analysis of production was carried out with the involvement of sectoral geological and hydrodynamic modeling. The carried out analysis made it possible to identify the zones of localization of current oil reserves by section and area. The application of differentiated influence systems on packs and layers - partial disaggregation of the object in the zones of localization of current oil reserves in production and injection wells and application of the targeted program of geological and technical measures will significantly improve the production efficiency of the object's reserves.
Основной объект разработки уникального Арланского нефтяного месторождения отличается исключительно сложным геологическим строением и содержанием тяжелой нефти повышенной вязкости. В разрезе терригенной толщи нижнего карбона выделены восемь продуктивных пластов с различными фильтрационно-емкостными свойствами. С учетом неоднородности фильтрационно-емкостных свойств в разрезе объекта правомерно выделение трех пачек: верхней, объединяющей три преимущественно выдержанных по площади высокопроницаемых пласта; средней с четырьмя маломощными пластами средней проницаемости; нижней, представленной одним мощным высокопроницаемым пластом с обширной водонефтяной зоной. Пласты средней пачки обладают ухудшенными коллекторскими свойствами по сравнению с пластами верхней и нижней пачек, что влияет на разработку многопластового объекта. Согласно результатам промыслово-геофизических исследований при совместной эксплуатации пачек объекта (добывающий, нагнетательный фонд) средняя пачка характеризуется худшими показателями, как на качественном, так и на количественном уровне. Это свидетельствует о неравномерности охвата пластов заводнением и меньшей степени выработки запасов из средней пачки. Для оценки локализации остаточных запасов в условиях многопластового объекта проведен глубокий геолого-промысловый анализ выработки с привлечением секторного геолого-гидродинамического моделирования. Результаты анализа позволили выделить зоны локализации остаточных запасов по разрезу и площади. Применение дифференцированных систем воздействия на пачки и пласты – частичного разукрупнения объекта в зонах локализации остаточных запасов в добывающих и нагнетательных скважинах - и адресной программы проведения необходимых геолого-технических мероприятий позволит существенно повысить эффективность и полноту выработки запасов нефти объекта.
Lozin, E. V. (BashNIPIneft LLC, RF, Ufa) | Arzhilovskiy, A. V. (BashNIPIneft LLC, RF, Ufa) | Chervyakova, A. N. (BashNIPIneft LLC, RF, Ufa) | Gareev, A. T. (BashNIPIneft LLC, RF, Ufa) | Nurov, S. R. (BashNIPIneft LLC, RF, Ufa) | Sibaev, T. V. (BashNIPIneft LLC, RF, Ufa)
The PDF file of this paper is in Russian.
Prof. V.N. Schelkachev at first made theory of elastic regime for oil-gas bedding systems on based the investigations the plural outage wells in Grozny’s oil field at war conditions in 1942 ye. After putting in operation the wells (for increase it amount there no having finance and physical resources) have more dynamic levels than before and start to more production. This are explained with elastic reaction of porosity-permeability medium and saturation liquid. Analogy conditions were being in Russian oil industry at beginning 90’s last century: there were not turn-over capitals to putting in operation outage wells; its amount were growth. Average period downtime of one well set up 5-7 years. Main these wells put in operation after downtime. In article were made analyses of hydrodynamics effect from long downtime of many produce wells at main object development Arlanskoye oil field – terrigenous low carbonic thick series. Criterions on representative wells are work out and analyses made only for its. Representative wells make up 24.0% from total quantity of outage ones. In result objective geology & petroleum date confirmed main statement of theory elastic regime: elastic energy content growth up; in conformity with present process growth seam pressure and hydrodynamic conditions support the increase of summary producing of oil from terrigenous low carbonic thick series and Arlanskoye oil field common.
Gafarov, Sh. A. (Ufa State Petroleum Technical University, RF, Ufa) | Lysenkov, A. V. (Ufa State Petroleum Technical University, RF, Ufa) | Gafarov, A. Sh. (Gazprom VNIIGAZ LLC, RF, Moscow) | Akimkin, A. V. (Bashneft PJSC, RF, Ufa)
The PDF file of this paper is in Russian.
In the article experience of use of monocarboxylic acid in oil well treatment are reviewed. Noted range of advantages of monocarboxylic acid compared to usually used hydrochloric acid solutions. Main advantages are: slower rate of interaction with carbonate matrix; lower corrosion rate; better iron and aluminum ions stability features. Monocarboxylic acid can be used as additives to hydrochloric acid solutions at oil well treatments (acetic acid, formic acid etc.). To optimize cost of treatments we tested out hydrocarbon liquid-phase oxidation products (hereafter referred to as ‘mono-mix’) - mixture of monocarboxylic acids and organic solvents. Production of mono-mix is well spread at gasoline plants or in situ at oil fields treating facilities. Mono-mix manufactured from co-produced gas or gas and condensate from gas fields. To define reservoir condition limitation for mono-mix well treatment series of laboratory tests was conducted. It is shown that mono-mix reaction with carbonate is exothermic. Neutralization rate of mono-mix as well as it`s solutions with HCl considerably slower compared to pure HCl. Mono-mix solutions (fresh or spent) bear low coefficient of surface tension at mono-mix – oil border. Mono-mix shows quite high stabilizing and bactericidal features. Fresh and spent mono-mix solutions significantly depress the swelling ability of formation clays as well as filtered from drilling mud, destroy and disperse clay structure supporting the takeaway from the reservoir, possessing anti-corrosion features.Using theoretical and experimental data one-fluid and two-fluids solutions for field testing proposed. 11 oil well exploiting Kashirskian-Podolskian horizon of Arlanskoye oilfield were treated with mono-mix solution. Before pilot test those wells were treated with HCl numerous times as well as with oil-acid emulsion. Treatment with mono-mix solutions complete in pilot test display much better result compared to previous standard HCl-solution treatments and can be recommended for common use.
В статье рассмотрен опыт использования монокарбоновых кислот для интенсификации добычи нефти. Монокарбоновые кислоты (уксусная, муравьиная и др.) обладают рядом преимуществ в сравнении с традиционно используемыми растворами соляной кислоты. Они медленнее взаимодействуют с карбонатными породами, являются менее коррозионно-активными, обладают лучшими стабилизирующими свойствами по отношению к оксидам железа, алюминия. Монокарбоновые кислоты используют как добавки к закачиваемым растворам соляной кислоты при кислотных обработках призабойной зоны скважин (ПЗС). С точки зрения стоимости технологии воздействия на ПЗС с применением монокарбоновых кислот, большой интерес представляет изучение возможности использования продукта жидкофазного окисления углеводородного сырья, который представляет собой смесь монокарбоновых кислот и органических растворителей. Процесс получения данного продукта освоен нефтехимической промышленностью. Он может быть получен на газобензиновом заводе и непосредственно в промысловых условиях, сырьем для получения продукта служат нефтяной газ, газ и конденсат газоконденсатных месторождений. Для определения геолого-физических условий эффективного использования продукта, для разработки технологии воздействия на пласт проведен комплекс лабораторных исследований. Установлено, что реакция продукта c карбонатной породой является экзотермической. При этом скорость нейтрализации продукта и его смеси с раствором соляной кислоты (HCl) значительно ниже скорости нейтрализации 15%-ного раствора HCl. Растворы продукта (активные и нейтрализованные) на границе с нефтью характеризуются низкими коэффициентами поверхностного натяжения, обладают значительно лучшими стабилизирующими и бактерицидными свойствами. Активные и нейтрализованные растворы продукта существенно подавляют способность пластовых и внедрившихся вместе с фильтратом бурового раствора глин к набуханию, растворяют и разрушают их структуру, способствуя выносу из пласта, имеют меньшую коррозионную активность. На основе теоретических и экспериментальных исследований предложены две технологии воздействия на ПЗС: однорастворная и двухрастворная. Приведены результаты обработки 11 скважин, эксплуатирующих карбонатные отложения каширо-подольского горизонта Арланского месторождения. Выбранные скважины до применения растворов продукта неоднократно подвергались стандартным соляно-кислотным обработкам, отдельные скважины - обработкам с использованием нефтекислотной эмульсии. Опытно-промышленные работы по применению технологии с использованием продукта жидкофазного окисления углеводородного сырья показали хорошие результаты. Рассмотренный продукт рекомендован для широкого внедрения при разработке карбонатных коллекторов.
Bashneft Oil Company has rich drilling history. First well in Bashkiria was drilled in Ishimbaiskoe oil field in 1932, the oil flow rate was 20 ton/day. Thereby oil exploration in Bashkiria commenced. Petroleum refinery was founded in Ishimbay city in 1935. The same year Bashneft oil company was founded. Initially the company composed of Ishimbayskoe oil field, logging and exploration facilities. 90 % of total oil production in west part of Soviet Union has been produced on Bashneft in 1939. Cumulative oil production was more than 15 million tons in 1955, Bashneft was the first company in USSR by cumulative oil flow rate per year.
Unsuccessful attempts of horizontal and multilateral well drilling were initiated in the beginning of 20 century in USA. However first multilateral well was completed in Ishimbaiskoe oil field under the guidance of Alexander Grigoryan in 1953. The well had of 9 boreholes, total effective length was 322 meters and initial oil flow rate was about 200 ton/day.
The oil cumulative production peak of 47 million tons was reached in 1967. One billion tons had been produced in Bashneft by 1980. Significant amounts of oil production were huge amounts of new drilling as green fields in region were discovered. In 1935 Bashneft had 19 wells, in 1970 were 7050. In 1980 total number of production wells in Bashneft was about 14 000. Large deposits were drilled the Soviet period. The last decade of the XX century drilling came mainly in new fields, small in size and reserves, as well as at during the main large fields of Bashkortostan. New reserves in old fields discovered due to detailed 3D seismic survey and processing of well data archives.
During period of 2008 – 2013 new well drilling decreased. 220 new wells were drilled in 2008 and 35 new wells were drilled in 2012. Average oil flow rate of new wells increased many times this period (figure 1).
Physics of surface effects in porous medium in relation to structural-mechanical mudding was investigated. The micro-rheology of surfactants effect on reservoir fluids was studied. Scientific basis for enhanced oil recovery techniques application was developed.
Low efficiency of low-concentrated solutions of non-ionic surfactants during flooding is linked to a number of factors that reduce relatively high laboratory evaluations of cleaning and displacing characteristics of individual surfactants - low surface activity of agent on border with oil, significant reduction of surfactant contents on displacement front due to high adsorption losses and shaft of buried water.
Filtration and micro-rheology research, conducted on original installation which allows to explore structural and mechanical properties of reservoir fluids in pores of µm size, showed that crucial role is played by another factor - the twofold effect of surfactants on film oil. This effect, previously noted in high-molecular systems, was defined by us for the low-molecular components of reservoir system "oil - surfactant solution - porous medium". The phenomenon essence lies in the surface and volumetric mechanisms of surfactants influence on the film oil. Firstly, there is a well-studied adsorption on active centres of solid body, what reduces structuring effect of the solid field on near-wall layers of liquid. Volumetric mechanism is due to diffusion of surfactant in liquid and reduction of cohesive interactions in liquid. Their combination can lead to both weakening and strengthening of non-Newtonian and filtration anomalies of film oil.
Proven that even light asphalt-resinous oil in pores with diameter of 1 - 4 µms acquires properties of solid rheological body, which depend on ratio of intensity of intermolecular interactions within the fluid and at its external borders. Introduction of surfactant, changing balance of these forces leads to increase or decrease in rheological and filtration anomalies of film oil. Mixed effects of surfactants on residual oil, complexity of maintenance of optimal reagent concentration at displacement front does explain results of field tests of this method, which requires additional non-standard laboratory tests and strict compliance of application technology in the field.
Direct measurements of structural-mechanical and hydrodynamic liquid parameters in tight gaps - flat capillaries in reservoir conditions have been carried out. The extreme character of concentration dependencies of hydrodynamic properties of capillary oil proves the possibility of oil effect mechanism change by variation of reagent concentration in the displacing fluid. The study defined more precisely physical-chemical peculiarities of membranous oil condition - impact of intensification methods and estimate its effectiveness degree. New methodology of studies included analysis of structure forming kinetics and the specifics of oil from three oil fields before and after reagent contacts in tight gaps, which correspond for average pore dimensions of low-, medium- and high-permeable reservoirs under development. Study has been carried out with reagents of different character. Proposed reagents meet major criteria for flow deflection technologies, helping on the first stage washing of oil in washed parts of reservoir and decreasing its permeability, subsequently. Extensive research allowed developing appropriate enhanced oil recovery technologies and it successful realization in the field.
Many ASP flooding method have been tested in Daqing oil field. After the success of polymer flooding in Daqing oil field, four alkaline-surfactant-polymer flooding pilot tests have been conducted in order to :increase oil recovery further and provide technical and practical experience for expanding the ASP pilot. From four ASP pilot test , the following conclusions can be made: ASP flooding pilot can form oil banks, greatly lower water cut, increase the oil production as well as the oil recovery. The incremental oil recovery was about 20% over water flooding.
To further confirm the effect of large well spacing on EOR ,three ASP field test with a large well spacing (200 to 250 m) have been tested in Daqing oil field. The commercial pilot tests result shows that the ASP flooding can increase recovery 20% more than water flooding.
The paper collected 12 pilot test date of industrial surfactant flooding in China, It Has been evaluated that each pilot test successful or not cleanly. Also discussed problem. Emphasize indicated that design project of combination flood, surfactant kind, structure, slag design and size and a scale of production were developed key. Decreased cost were also important task . Alkaline-Surfactant-Polymer (ASP) flood processes have been increasingly applied in the oil fields due to their high ultimate oil recovery. However, a major technical challenge is how to significantly reduce the amount and the cost of chemicals used such that ASP floods can become cost-effective as well. Field applications show that the concentrations of alkali, surfactant and polymer remain relatively high in the produced fluids of ASP floods. Thus, successful reuse of these chemicals can substantially reduce the capital cost and the environmental impact. Also re-injection of the produced chemicals is conducted for further enhancing oil recovery.
This paper have discuss problems of ASP flooding:
Emulsions occurred in some producers of the larger well spacing field test, the test shows that by using a specific kind of de-emulsifier commonly used in the field, the emulsions in the produced fluid are not to be broken because adding hard alkali.
This paper provides practice basis for the enlarging of ASP flooding..At present, most of ASP flooding are successful, But alkaline/com-oil carboxylates/polymer and foam/alkaline/surfa-
ctant/polymer flooding are not successful to be used to Daqing oilfield. The cost of chemicals (alkaline/surfactant/polymer) per barrel incremental oil is $11 to $15.The total cost of per barrel incremental oil is $15 to $30 .The incremental recovery is 20% OOIP over water flooding.
Summary and progress
Recently, chemical flooding is a important technology of tertiary recovery methods. Chemical EOR operations are increasingly applied in the oil fields as tertiary oil recovery methods. In the literature, there are some comprehensive studies on chemical flooding. A variety of chemical floods are conducted, such as alkaline flood, surfactant flood, polymer flood, Alkaline-surfactant flood, alkaline-polymer (AP) flood and ASP flood. In particular, as one of the most effective EOR techniques, ASP flood has been applied to recover the residual oil in the reservoirs since 1980. It has been reported that the successful applications of ASP floods in daqing and Karamay oil fields can enhance oil recovery up to 20% [1-6]. Generally speaking, an ASP flood is a modified alkaline flood. Field applications of alkaline floods alone result in poor oil recovery due to the alkaline loss caused by the chemical reactions with the reservoir rocks, low acid number of the crude oil, and adverse mobility ratio .The mechanisms of the polymer flood are viscous property can increase apparent viscosity and viscous elasticity, The injected polymer can significantly improve the mobility ratio, polymer flood enhances both the areal and the vertical sweep efficiencies.. Many of polymer floods alone (daqing ,shengli, dagang oil field, China) indicated that usually result in 6-12% oil recovery. The ASP combination flooding is defined as a combination flooding system of alkali, surfactant and polymer. The ASP technologies were well studied during the 80's, and proved to be an effective method for improving oil recovery process for certain reservoires1.During the 80's to 90's, the ASP combination flooding studies were conducted in Daqing and Shengli oil field, and the results were very good from both laboratories and fields The major EOR mechanisms of an ASP flood are briefly described as follows. In conjunction with the added surfactant, the surfactants generated in situ by the chemical reactions between the injected alkali and the natural organic acids in the crude oil can result in ultra-low interfacial tension (IFT). The ultra-low IFT at the oil-brine interface helps to emulsify and mobilize the residual oil in a reservoir. In addition, the reservoir rock surface becomes more negatively charged at higher hydroxyl ion concentrations[7??8??9??10??11 12]. These negatively charged ions not only prevent the adsorption of anionic chemicals, such as anionic surfactants and polymers, but also change the wettability of the rock surface12-14. Also, the added surfactant can enhance the salinity tolerance of the alkali15. To achieve the same displacement efficiency as that of micellar-polymer flood, the surfactant concentration required in the ASP flood can be reduced by one order16 ; The injected polymer can significantly improve the mobility ratio. The adsorption of polymer onto the reservoir rock can reduce the effective water permeability. Hence, polymer flood enhances both the areal and the vertical sweep efficiencies17. The earliest field test started on December 3, 1987 in West Kiehl oil field, a very exciting results were achieved .By the end of june 22 in 1990, the incremental oil recovery was 26%OOIP.
The sweep efficiency enhancement technologies applied in Russia were analyzed. It was shown that the most common sweep efficiency enhancement techniques are sidetracking, non-stationary flooding and different flow-diverting technologies, based on chemicals injection, restricted by volume. In some cases, hydraulic fracturing can be considered also as a means to improve the sweep efficiency by treatment. The case histories of all treatment techniques specified in the paper are presented and trends of their development in the future are identified.
The report is devoted to the estimation of intensity of display of quasi-viscous properties of oils of depositions of bottom and medial Carbon. By the studies held earlier it has been demonstrated, that at the increased maintenance in oils of asphaltic-resinous components and paraffins filtering of oils in formation takes place with deflections from Darcy linear law. A consequent of oil display quasi-viscous properties is a reason of formation zones of the depressed filtering or stagnant zones, decrease of completeness of oil displacement and increase of expenses at production activity.
According to the experiments results it is established:
- viscosity of oils with not destroyed spatial pattern is on the order and more exceed viscosity of the same oils with completely destroyed structure. Accordingly, mobility of oils in pore space in terrigene rocks due to structuring decreases at 2-17 times.
- intensity of display of anomalies of oil viscosity and mobility in many respects depends on amount and gas-phase composition. Oil viscosity and mobility anomalies in terrigene rocks intensify with gas content increase.
- oil with quasi-viscous properties by the character of capillary flow relate to pseudo-plastic liquids. Static pressure and gradients of pressure of shift are noted in oils with the increased maintenance of heavy paraffin hydrocarbons.
Quantitative estimations of rheological and filtration characteristics of reservoir and separated oils, which account will raise reliability of designing of development and field construction of deposits with non- Newton oils are given.
Russia is one of the main oil producing country in the world with very long history of the oil industry. In one's time in former Soviet Union a lot of attention was paid to oil recovery problems. Unfortunattelly the unfavorable economic climate of the late 1980-s and economic shocks during the period of well-known events in the country in 1990-s caused the rapidly decline of the number of new EOR projects. EOR technologies started to develop in direction of sweep efficiency improvement by cheap agents. Nevetheless by now the very intereresting EOR experience has been accumulated in the country. It is likely that EOR- produced oil in Russia has not already reached its peak level and that it will increase above the current production rates because of improvement of economic situation in the country on the one hand and increasing of mature fields on the other hand.
The paper presents an overview of EOR field experiences in former Soviet Union and Russia for the last 25 years, an analysis of recent efforts and discusses briefly on perspectives for conventional and new EOR methods. The main EOR experiences reviewed are chemical flooding (and flow diverting technologies in particular), gas injection, thermal recovery process, microbiological and unconventional EOR.