Potential Of Wells Research Articles

Evaluation of carbon dioxide storage potential in wells of the Bredasdorp Basin offshore South Africa

This study focuses on determining how carbon dioxide (CO2) storage can be stored in the central Bredasdorp basin offshore South Africa. Logs, seismic lines, and reports of three exploration wells were used to build a 3D static model, and the compressibility method was used to estimate the CO2 static storage capacity of the reservoir. The wells displayed fair to good porosity and moderate permeability. The zone of interest had little to no faulting, and there is evidence of differential deposition of marine sandstones that overlie fluvial shales. The sandstones have good reservoir characteristics and are overlain by thick shales that serve as seals. The reservoir displayed thinning in the eastern direction and over structural highs. A static storage assessment of the reservoir showed 0.64 Mt of CO2, and the effect of changing pore volume and water saturation on overall CO2 storage volume was observed. The results revealed that an increase in pore volume would also increase the amount of CO2 stored in the reservoir. Conversely, increased water saturation leads to decreased CO2 that can be stored in the reservoir. This study has shown that the pre-existing reservoir fluid has an impact on CO2 storage volume; the greater the volume of water in the reservoir, the less the volume of CO2 that can be stored in the reservoir; this is because water is less compressible than rock, oil or gas.

WELL SILENCING TECHNOLOGIES IN CONDITIONS OF MULTIPLE COMPLICATIONS

Silencing of wells in the conditions of the Jurassic facilities developed by «Kharampurneftegaz» LLC is complicated by a number of negative factors, such as low permeability of the hydrophilic reservoir collector, high gas factor, low reservoir pressure, which significantly reduce the success of underground repair of wells (URW). To eliminate the influence of these complications in URW, an approach to silencing technology has been developed, which consists in combining several types of technological fluids, which, when used together, can eliminate the risks of reducing the production potential of wells after repair. So, to prevent gas manifestations during the URW, a blocking liquid based on the polymer «Biopol» and surfactant (gas-blocking compound, GasoBC) has been developed, acting due to its viscoelastic properties (polymer) and foaming ability in contact with gas (surfactant). A buffer liquid designed to prevent swelling of clay cement, reduce interfacial tension and restore phase permeability in oil was developed on the basis of a 6% HCl solution with the addition of a surfactanthydrophobizer (buffer hydrochloric acid liquid, BufHA). Blocking silencing compound (BSС) based on a Biopol polymer solution with a suspended suspension of microcalcite (BSС-microcalcite) and halite (BSС-halite) allows to prevent the absorption of silencing fluid at reduced reservoir pressure in wells with hydraulic fracturing.
 Pilot field testing of the technology of silencing wells with multiple complications was carried out at 23 wells, where GasoBС block packs were used 21 times, BufHA — 9 times, BSC-halite and BSC-microcalcite — 14 and 9 times, respectively.
 8 typical silencing plans have been compiled for various parameters of wells. The results of research and development works are fixed in the Instructions of «Kharampurneftegaz» LLC on the topic «Selection of blocking silencing compounds during well repair».

The Application of Neural Networks to Forecast Radial Jet Drilling Effectiveness

This paper aims to study the applicability of machine-learning algorithms, specifically neural networks, for forecasting the effectiveness of Improved recovery methods. Radial jet drilling is the case operation in this study. Understanding changes in reservoir flow properties and their effect on liquid flow rate is essential to evaluate the radial jet drilling effectiveness. Therefore, liquid flow rate after radial jet drilling is the target variable, while geological and process parameters have been taken as features. The effect of various network parameters on learning quality has been assessed. As a result, conclusions on the applicability of neural networks to evaluate the radial jet drilling potential of wells in various geological conditions of carbonate reservoirs have been made.

Automation of workover candidate ranking processes at Krasnoleninskoye oil and gas condensate field

Background. Workovers (WO) are the main EOR tool at Krasnoleninskoye reservoirs. Therefore, the issue of increasing the reliability of technological and economic performance when planning various types of workovers is urgent. This is due to the complexity of selecting well candidates, the lack of a comprehensive methodology for assessing the short-term and long-term potential of wells, large WO scopes, as well as declining WO performance associated with the reduction of reserves, deterioration of the energy state of the reservoirs, and advancement of the injected water front. 
 
 The purpose of the study is to create mathematical tools that will reduce the time of well-candidates selection for various types of workovers and to improve the WO quality for entire field. 
 
 The paper describes methods of automated selection of well candidates that were successfully applied in the conditions of the field of interest, namely graphical and mathematical tools. The mathematical one has been created based on the correlation-regression analysis of the actual implementation of stimulation methods in various geological-field conditions in Microsoft Excel 2010 with Visual Basic for Applications (VBA). The graphical tool has been generated on the basis of all historical field data verified and processed using methods of primary statistical analysis in RN-KIN software. 
 
 The study resulted in a technique that was selected and tested in the conditions of Krasnoleninskoye oil and gas condensate field. The process of introducing the developed approaches to the search for well candidates for various types of workovers in the field was accompanied by updating, analysis of results, and cyclic training of the system. A methodological approach has been developed, including the combination of several methods for selecting well candidates for various types of workovers. A combination of statistical and graphical methods made it possible to significantly improve the reliability of WO candidates selection and therefore to reduce the share of uneconomic workovers by 12 % in the period from 2017 to 2020. As part of the study, a script has been developed that automatically computes the rank of a well-candidate which significantly reduces time costs and allows to quickly evaluate the “best” workover candidates.

Empirical and theoretical analysis of a modified isochronal test in a caspian region gas reservoir

A deliverability test performed in a gas well is one of the fundamental steps to determine the flow potential of the wells in reservoir surveillance. Dynamic reservoir models need robust AOF (Absolute Open Flow), productivity index, permeability for calibration, history matching, and predictions. In this study, a gas well in a Pliocene sandstone gas reservoir was validated using the “Modified Isochronal Testing” method. This study aims to mitigate the efforts done to estimate the phenomenon of flow potential of the gas wells. Hence, the field development activities can be leveraged to a more efficient stage technically and economically. In this study, AOF, Productivity Index (PI), and the permeability of the tested interval were calculated. The validation of the permeability with log and core data increases the confidence level of the work done. AOF is the key performance indicator to define the gas well productivity at zero sand face pressure which is a measure of ranking the production potential of gas wells. The AOF values support the determination of the number of wells to be drilled and the design of the surface facilities. In this study, pressure and time data were obtained and they were analyzed by empirical and theoretical methods. These two methods used in analysis gave very close AOF values; 10.15MMSCF/D (empirical) and10.67 MMSCF/D (theoretical), respectively. The permeability was calculated as 3.42 md, which is in line with the log permeability of 3.70 md and core permeability of 3.40 md.

Development of a comprehensive methodology for the forecast of effectiveness of geological and technical measures based on machine learning algorithms

The main part of hydrocarbon production in Russia is represented by old oil and gas producing regions. Such areas are characterized by a significant decrease in well productivity due to high water cut and faster production of the most productive facilities. An important role for such deposits is played by stabilization of production and increase of mobile reserves by improving the development system. This is facilitated by various geological and technical measures. Today, an urgent problem is to increase the reliability of the forecast of technological and economic efficiency when planning various geological and technical measures. This is due to the difficulty in selecting candidate wells under the conditions of the old stock, the large volume of planned activities, the reduction in the profitability of measures, the lack of a comprehensive methodology for assessing the potential of wells for the short and long term. Currently, there are several methods to evaluate the effectiveness of geological and technical measures: forecast based on geological and field analysis, statistical forecast, machine learning, hydrodynamic modeling. However, each of them has its own shortcomings and assumptions. The authors propose a methodology for predicting the effectiveness of geological and technical measures, which allows one to combine the main methods at different stages of evaluating the effectiveness and to predict the increase in fluid and oil production rates, additional production, changes in the dynamics of reservoir pressure and the rate of watering of well production.

АПРОБАЦИЯ МЕТОДИК ПРОГНОЗИРОВАНИЯ ТЕХНОЛОГИЧЕСКОЙ ЭФФЕКТИВНОСТИ ВЫРАБОТКИ И ОЦЕНКИ ЗАПАСОВ НЕФТИ ПРИ ПОДБОРЕ СКВАЖИН-КАНДИДАТОВ НА ПРОВЕДЕНИЕ МЕРОПРИЯТИЙ ПО ОБРАБОТКЕ ПРИЗАБОЙНОЙ ЗОНЫ СКВАЖИН НА ПРИМЕРЕ СЕВЕРО-ОРЕХОВСКОГО МЕСТОРОЖДЕНИЯ

Актуальность исследования вызвана необходимостью оценки текущего состояния качества запасов нефти призабойной зоны скважин и прогнозирования технологической эффективности существующей выработки нефтяных запасов при подборе скважин-кандидатов на проведение мероприятий по обработке призабойной зоны, что соответствует потребностям мировой практики в поиске наиболее результативных методик освоения нефтегазовых месторождений. Цель: определить величину изменения балансовых запасов нефти на примере Северо-Ореховского месторождения и произвести анализ методик, позволяющих осуществить прогнозирование технологической эффективности выработки и оценки запасов нефти при подборе скважин-кандидатов на проведение мероприятий по обработке призабойной зоны скважин, применяемых на территории Северо-Ореховского месторождения Объект: Северо-Ореховское месторождение как энергоресурсный комплекс, на базе которого осуществляется не только применение традиционных методик прогнозирования технологической эффективности выработки нефтяных запасов, но и апробируется качественно новая методика оценки запасов нефти при подборе скважин-кандидатов на проведение мероприятий по обработке призабойной зоны. Методы: прогнозирование, обусловившее понимание технологической эффективности выработки и оценки запасов нефти при подборе скважин-кандидатов на проведение мероприятий по обработке призабойной зоны скважин; определение величин удельных остаточных балансовых запасов обусловило обращение к сравнительному анализу возможностей скважин доноров и акцепторов; анализ и оценка величины выходящих из дренирования запасов; оценка значения текущей нефтенасыщенности. Результаты. Большинство нефтяных месторождений Западной Сибири находится на поздней стадии разработки. В связи с этим вопрос выработки остаточных запасов становится первоочередным. Для принятия проектных решений на прогнозный период разработки необходима оценка остаточных ресурсов углеводородов месторождения, что обусловливает актуальность исследования и адаптации методов оценки ресурсов месторождения. Произведен сравнительный анализ существующих методик прогнозирования технологической эффективности выработки и оценки запасов нефти, используемых при подборе скважин-кандидатов на проведение мероприятий по обработке призабойной зоны скважин. Предлагается измененный способ определения удельных балансовых запасов нефти, позволяющий для каждой добывающей скважины учесть запасы и отборы всего объекта, а также фильтрационно-емкостные свойства всего фонда скважин. Установлено, что метод определения величин удельных остаточных балансовых запасов предполагает выявление скважин доноров и акцепторов. Выявлено, что используемый подход в подборе скважин-кандидатов под обработку призабойной зоны является универсальным, так как позволяет выявлять скважины с недостаточной выработкой при существующем потенциале (водоограничивающие, гидрофобизирующие методы увеличения нефтеотдачи). Более того, данный методический подход предполагает принцип оценки относительной динамики отборов нефти и выявление несоотносимо высоких с остаточным потенциалом темпов падения добычи нефти. Методический подход, совмещающий свойства прогноза ожидаемой технологической эффективности и критериального обоснования, основывается на применении процедуры расчетов параметров множественного регрессионного анализа. В его основе лежит предположение, что технологическая эффективность мероприятий (исключая успешность, случайный фактор) тесно связана с геолого-технологическими параметрами, характеризующими потенциал скважин – остаточные извлекаемые запасы, эффективная нефтенасыщенная мощность, площадь зоны дренирования, проницаемость и т. д. Доказывается, что данный метод подходит не только для подбора скважин-кандидатов под обработку призабойной зоны, но и для групп технологий увеличения нефтеотдачи различной специфики (по механизму вовлечения незадействованных запасов нефти); искомой функцией является технологическая эффективность от мероприятий (за год или за месяц), а аргументами – набор геолого-технологических показателей фонда скважин на дату проведения мероприятия. Предложена методика оценки остаточных балансовых запасов фонда скважин, что способствует определению качества нефтяных запасов для отдельной добывающей скважины и позволяет учесть запасы и отборы всего объекта, а также фильтрационно-емкостные свойства всего фонда скважин. Выводы. Установлено, что выявленные в ходе анализа особенности существующих методик позволяют решить ряд нефтепромысловых задач: определить объем выходящих из дренирования запасов (подбор водоограничивающих методов увеличения нефтеотдачи, ремонтно-изоляционные работы, коррекция режимов работы скважин, остановки); определить величину незадействованных запасов нефти, не участвующих в дренировании (гидровлический разрыв пласта, уплотнение); проанализировать достижимость выработки извлекаемых запасов, оцениваемых по общепринятым характеристикам вытеснения, по добывающим скважинам, то есть произвести их коррекцию.

A new refracturing candidate selection method for multi-fractured horizontal wells in tight oil reservoirs

Abstract Refracturing technology has been widely applied to increase the production rate of multi-fractured horizontal wells (MFHWs) and enhance ultimate recovery. However, due to the complicated relationships between various parameters, it is often difficult to select candidate wells for refracturing. A novel method combining analytic hierarchy process (AHP), grey relation analysis (GRA) and fuzzy logic was proposed in this study to evaluate refracturing potential of wells from reservoir quality and initial completion efficiency. First, based on the parameters of the constructed wells, several elements were chosen as appraisal factors. AHP was used to establish a multi-parameter evaluation system for refracturing treatment. Then, GRA was used to calculate the weight coefficient and sort out the main factors that influence fracturing result. Finally, GRA was coupled with fuzzy logic to determine the classification threshold of reservoir quality. A novel comprehensive evaluation score (CES) was proposed to determine the priority of the refracturing wells. The method was successfully applied to a tight oilfield in Northeast China and the optimum refracturing potential area was selected based on the reservoirs quality and completion efficiency by using quadrant analysis. Average daily oil production increased from 2.3 to 17.6 tons per day after refracturing treatment. The method can be used to identify refracturing candidates quickly and economically.

Advanced cuttings analysis provides improved completion design, efficiency and well production

R ecent case studies of lateral well completions have highlighted the apparent ineffectiveness of geometric stage performance with regards to fracture initiation and stimulated reservoir volume (Far et al., 2015; Ashton et al., 2013; Ganguly and Cipolla, 2012). It has been observed that poor stage performance can be attributed to varying rock type compositions along the borehole, due to lateral facies changes and/or wellbore porpoising. The inefficiencies linked to non or poor performing stages can result in higher costs, associated with equipment and materials, and limit the production potential of wells. This case study highlights how the application of an optimized hydraulic fracture stimulation plan, by honouring lateral well geological heterogeneities, improved completion efficiency and well production within the Cleveland Sandstone formation, Oklahoma, USA. Optimized completions Designing optimized hydraulic fracture stimulation in a lateral well requires an understanding of the near-well bore geomechanical properties and the near-well bore and farfield stresses along the entire lateral. Such reservoir characterization is normally developed from geomechanical and petrophysical analyses using wireline or logging-while-drilling (LWD) services that include acoustic and borehole- image logs. Unfortunately, economic considerations can often inhibit or prohibit the use of logging techniques and hence the complete characterization of the reservoir, especially in the current low oil and gas price environment. A practical and convenient alternative for reservoir characterization is to use the commonly available cuttings samples to provide gross characterization of a vertical or lateral well. Utilizing Automated Mineralogy (AM) techniques, such as CGG’s RoqSCANTM, (Ashton et al., 2013) provides comprehensive data from these cuttings which includes mineralogy, texture and rock properties throughout the entire length of the well. RoqSCAN analysis can be performed either in the laboratory or at the well site to provide near-real-time reservoir navigation and data to optimize the design of completions that will be performed soon after the well reaches total depth (TD).

Influence of time-periodic potentials on electronic transport in double-well structure

Within the framework of the Floquet theorem, we have investigated single-electron photon-assisted tunneling in a double-well system using the transfer matrix technique. The transmission probability displays satellite peaks on both sides of the main resonance peaks and these satellite peaks originate from emission or absorption photons. The single-electron resonance tunneling can be controlled through changing the applied harmonically potential positions, such as driven potential in wells, in barriers, or in whole double-well systems. This advantage should be useful in the optimization of the parameters of a transmission device.

About the potential of wells to reflect stress variations within inhomogeneous crust

Kümpel, H.-J., 1992. About the potential of wells to reflect stress variations within inhomogeneous crust. In: T. Mikumo, K. Aki, M. Ohnaka, L.J. Ruff and P.K.P. Spudich (Editors), Earthquake Source Physics and Earthquake Precursors. Tectonophysics, 211: 317–336. Numerous pre-, co-, and post-seismic well level changes, that are believed to reflect stress variations in the crust, have been observed in various parts of the world. So far, analysis of these data has not favoured a distinct model of the processes that could be involved. The benefit from the signals is, in fact, limited because understanding of the underlying physical mechanisms is poor. The paper discusses the impact, that inhomogeneities in the brittle crust can have on the observations. In particular, the following problems are considered: (1) Could the well level signals be induced by the invasion of pressurized pore fluid at some place? (2) Could the hydrological conditions close to the observation well modulate any remote pore pressure variation? (3) Which features of the crust are most likely to dominate the process of stress transfer in the crust? (4) How should a stress-sensitive well be designed? The results can be summarized as follows. (1) Stress diffusion due to the invasion of pressurized pore fluid can lead to significant well level changes, only when the source region is at closer distance than a few kilometres (probably less than a few hundred metres) from the well. (2) Local inhomogeneities in the vicinity of the observation well may strongly influence the well's response to remote pressure changes. Even sign reversal of the anomaly may be encountered. (3) There is increasing evidence that the wide range of stiffness values of natural rocks (from 100 MPa or less, till 100 GPa), manifested in a fractal distribution of fault-like weak zones within relatively stiff formations, dominates stress transfer in the brittle crust. Uncertainty about the effective rheology for time scales from 10 −4 to 10 3 years limits the inversion of many geophysical observations at present. (4) Of various configurations, a well tapping an extensive hydraulic fracture could act best as a sensitive stress sensor, provided that the fracture volume is isolated from the pore space of the host rock. However, experimental evidence of the practicability of such configuration is still due. The weakness of conventional wells as stress sensors results from the fact that the process of fluid flow often lacks a sufficient control on attenuation mechanisms for low-frequency well level variations, regardless of whether the wells end in stiff or weak formations. To a large extent, the presented findings are compiled from publications of investigators working in various fields.

Ground‐Water Contamination in the Silurian Dolomite of Door County, Wisconsina

ABSTRACTDoor County, a recreational and fruit‐growing area bordering Lake Michigan in northeastern Wisconsin, has had a long history of ground‐water contamination from surface and near‐surface sources. Contamination is most severe in late summer when the influx of tourists and fruit‐canning operations create additional wastes.Thin soil cover and well‐fractured dolomitic bedrock give easy entry to ground‐water contaminants throughout large parts of Door County. Many contaminants enter the dolomite by surface or near‐surface seepage. There is little attenuation of contamination concentrations in the well‐jointed dolomite, and contaminants may travel long distances underground in a relatively short time. The major source of ground‐water contamination is bacterial, from individual waste‐disposal systems, agricultural, industrial, and municipal sources. Contamination is in zones that originate from point sources and move in the direction of ground‐water flow, either naturally or as induced by pumping wells. The contaminated areas include only a small percentage of the total ground‐water system and are separated by large areas of ground water free of contamination. Tests based on indicator bacteria suggest that the periods of highest contamination potential occur during or immediately following rapid ground‐water recharge periods. Increasing the depth of casing and pressure grouting the casing into firm bedrock are two well‐construction procedures that reduce the contamination potential in wells.

Review of Geothermal Energy in New Zealand: ABSTRACT

Generation of electric power in New Zealand from geothermal steam at the present time amounts to 148 MW at the Electricity Department's station at Wairakei, and < 10 MW at the Tasman Pulp and Paper Company's mill at Kawerau. Exploration commenced in 1950, and in association with geologic, geophysical, and geochemical surveys, wells were drilled at Waiotapu, End_Page 1439------------------------------ Reporoa, Broadlands, Tauhara, Orakei Korako, and Te Kopia in the central volcanic region of the North Island, and at Ngawha in Northland. At Broadlands the production potential of wells already drilled is about 130 MW, and other wells are being drilled. Technical studies carried out in New Zealand indicate that capital costs per kW for small geothermal power plants are at least as cheap as those for large plants, making the former attractive for developing countries and isolated districts. Estimates of power-life of geothermal systems are not yet possible, but studies of the effect of draw-off rate show that a maximum power-life is obtained if wellhead pressure is allowed to fall to 75 p.s.i.g. over the life of a field. From a hot-water geothermal reservoir power output can be increased for the same rate of production if the steam-water mixture is conveyed to the powerhouse in a single pipeline and separated in two stages. More than 500 shallow wells have been drilled in Rotorua and a few in Taupo to tap hot water and steam used in conjunction with heat exchangers to provide space heating and hot-water supplies for domestic and commercial users, for drying of timber lucerne, growing of mushrooms and fruit, and hydrotherapy in the treatment of patients. Permission has been given to a Japanese group to make a feasibility survey, based on a study of the Broadlands field, of the possibility of using geothermal energy in the production of heavy water. Hot spring discharges at localities in both islands have been augmented by drilled wells to extend facilities at swimming pools for public use. A recent development in the Bay of Plenty near Tauranga has been the drilling of wells to obtain warm water for public and private swimming pools in areas where the subsurface gradient is 1.5-4 times normal. End_of_Article - Last_Page 1440------------