Stabilizing Oil Production Research Articles

A novel method to identify preferential flow paths by considering the time-varying effect of petrophysical parameters in ultra-high water-cut reservoirs

The continental clastic reservoirs mainly distributed in the eastern region of China are regarded as the “ballast stone” for ensuring national energy security. After long-term waterflooding, reservoir petrophysical parameters have changed drastically. When the ultra-high water-cut period is achieved, the preferential flow paths are widely distributed inside the reservoir, resulting in severe ineffective water circulation and high difficulty in inhibiting water cut rise and stabilizing oil production. Due to the slow calculation speed and low identification accuracy of the existing methods, it is crucial to propose a novel method to identify preferential flow paths by considering the time-varying impact of petrophysical parameters in ultra-high water-cut reservoirs. To tackle this issue, massive dynamic and static data are collected from typical water-drive reservoirs in the Daqing oilfield to analyze the dynamic characteristics of preferential flow wells and the time-variation laws of reservoir parameters. A rapid evaluation index system for preferential flow paths is thereafter established. By describing the time-variation of reservoir permeability and fluid apparent viscosity and introducing a dynamic flow resistance coefficient to infer the inter-well or inter-layer connectivity, a novel method with the time-varying effect of petrophysical parameters considered is developed to quickly identify preferential flow paths in ultra-high water-cut reservoirs. A critical criterion of preferential flow paths is further constructed. Finally, the proposed method is used to determine the spatial distribution of preferential flow paths in a typical block of the Daqing oilfield. Results demonstrate that, once a preferential flow path is formed, some distinct dynamic characteristics of injectors and producers will be exhibited. Based on the estimated dynamic flow resistance coefficient, the preferential flow paths are further classified into four types: non-preferential, primary preferential, intermediate preferential, and strong preferential flow paths. Using the proposed method, the identification accuracy of preferential flow paths exceeds 95%, and the identification speed is more than 10 times faster than the traditional methods.

ПОЛИМЕРЛІ ЕРІТІНДІЛЕРДІҢ РЕОЛОГИЯЛЫҚ ҚАСИЕТТЕРІН ЗЕРТТЕУ

Annotation. The long-term operation of the deposit, the alternation of reservoir zones with high and degraded filtration and capacitance properties due to the heterogeneity of the reservoir, the deformation of the development system due to downtime and inactivity of wells predetermined the selective movement of water through the most permeable layers. As practice shows, the widespread use of traditional flooding technology does not ensure the effective production of residual reserves from low-permeable and highly watered formations. Therefore, increasing the degree of oil extraction from the depths of the developed fields using effective methods of active impact on water-oil-saturated formations is an important scientific and technical task facing the oilmen of the republic. One of the most effective and promising methods of stabilizing oil production is physics-chemical technologies based on the use of injection of polymer compositions. The main purpose of injection of polymer compositions is to equalize the heterogeneity of productive layers by reducing the mobility of the displacing agent in highly conductive interlayers and increasing the coverage of the reservoir by flooding both in power and in stretch. As is known, the effectiveness of the use of technologies based on polymer solutions depends on their good selective filterability into zones with high water saturation, which allows creating water-insulating screens in the desired direction and to a sufficient depth. It is known that the effective use of polymer solutions depends on the influence of various factors: molecular weight, polymer concentration in solution, filtration rates, reservoir permeability, as well as such an important parameter as the rheological properties of polymer solutions. The study of the rheological properties of polymer solutions allows us to substantiate and propose for practical implementation effective integrated technologies for increasing oil recovery during the operation of the oil fields under consideration. In this work, the rheological properties of polyacrylamide, physical parameters, taking into account their physics-chemical properties, are studied. The influence of mineralization and water hardness on polymer solutions is considered. The issues of mechanical destruction of polymers have been studied. The degree of mechanical destruction of the polymer is estimated based on the results of the study of the rheological properties of the polymer sample.

БИОПОЛИМЕРЛІК ЖҮЙЕГЕ НЕГІЗДЕЛГЕН АҒЫНДЫ АУЫТҚУ ТЕХНОЛОГИЯСЫН ҚОЛДАНУДЫ ТАЛДАУ

Annotation. At present, many oil fields are on the third and fourth stages of development, which are characterized by significant volumes of associated water production and low degree of depletion of oil reserves from individual sections of the deposit. The volume of oil produced from the deposits is constantly decreased. This is due to the influence on the operation of wells of complex geological structures of productive formations, and fluid compositions that manifest themselves in production processes. In dense reservoirs with high geological heterogeneity, separate undeveloped areas and areas that are not covered by flooding remain in the development process. In these conditions, in order to increase the efficiency of flooding systems, the task is to maximize the coverage of reservoirs by exposure, which can be achieved by introducing water into low-permeable oil-saturated intervals. In this case, the elastic-capillary-cyclic method and the method of changing the direction of filtration fluid flows in the reservoir have significant possibilities, both in area and in the section. In this case, the elastic-capillary-cyclic method and the method of changing the direction of filtration fluid flows in the reservoir have significant possibilities, both in area and in section. One of the most effective and promising methods of stabilizing oil production is physics-chemical technology based on the application of injection of polymer compositions. This paper provides an analysis of the application of the technology of redistribution of filtration flows in a multilayer field. This technology used a biopolymer-based chemical composition. To study the effect of the biopolymer system on the oil production process, an analysis of changes in the technological parameters of the reacting production wells was carried out. The article provides an assessment of the technological effectiveness of methods for changing the direction of filtration flows in the reservoir based on the analysis of the results of the use of biopolymer compositions at one of Mangystau deposits. Keywords: Well, oil deposit, influence on the formation, flow-deflecting technology, filtration flow, polymer composition, biopolymer system, efficiency

Synergistic mechanism of enhanced heavy oil recovery by compound flooding using 3D visualization model

Most of oilfields have entered the development stage of high water-cut and low recovery factors, and stabilizing oil production and controlling water production are the key to enhancing subsequent oil recovery. Adopting the 1/4 five-point injection-production well pattern, the chemical flooding experiments were conducted using a three-dimensional (3D) visualization sand-pack model with liquid drain orifices. A real-time image acquisition and dynamic observation device for detecting droplet textures as fluid flowing was developed with experimental system. In heterogeneous reservoirs with a high permeability contrast, the effects of oil-displacement agents on production dynamics, sweep morphology, and emulsifying characteristics of remaining oil at different locations were investigated to reveal the synergistic mechanism of compound flooding for enhanced oil recovery. The results showed that, in the main streamline region, the mean droplet diameter decreased, the distribution density increased first and then decreased, and the maldistribution decreased first and then increased with an increase in injection volume of the compound system. In the vertical region with the main streamline, the mean diameter and maldistribution reduced, and the distribution density increased owing to the synergistic mechanism. The viscosity reducer can increase sweep efficiency by 8.34% and recovery factor by 5.95% due to the viscous crossflow in the high permeability channel. The compound system can increase sweep efficiency by 15.92% and recovery factor by 12.67% due to the synergistic effect of emulsifying-tapping, emulsion plugging conversion, and profile control. Therefore, chemical compound flooding has great potential of enhancing heavy oil recovery in heterogeneous reservoirs due to the synergistic effect of the compound system.

Transient Pressure Behavior of Finite-Conductivity Fractures in Horizontal Wells Considering Interference of Water-Injection Wells

Fractured horizontal wells and water-flooding development are effective means to stabilize oil production in low-permeability reservoirs; however, transient pressure behavior analysis based on a single-well testing model ignores the interference effect caused by water-injection wells. With advancements in horizontal drilling technology, multiple-fracture horizontal wells are widely used in tight reservoirs, and researchers have concluded that pressure drops in hydraulic fractures cannot be ignored. In this paper, we present a well testing model that considers the effects of finite-conductivity fractures and the interference of water-injection wells. The analytical solutions were derived based on the source function and superposition principle, and the characteristics of the transient pressure behavior at the bottom hole are analyzed and discussed. The typical pressure curve of our model showed that seven flow regimes exist: wellbore storage stage, transitional flow, first linear flow, fracture interference flow, second linear flow, pseudoradial flow, and interference flow. Furthermore, the results of the sensitivity analysis indicated that the flow regimes are greatly affected by the properties of the fractures and water-injection wells. The length of the fracture mainly affects the transitional flow, first linear flow, fracture interference flow, and second linear flow regimes, whereas the number of fractures predominantly affects the first two stages. The fracture spacing has a significant effect on the fracture interference flow and second linear flow regimes, and the water-injection rate mainly affects the interference flow regime. The well spacing determines when the interference effect occurs. These findings will support more accurate modeling of well production performance considering the impact of water-injection wells.

Problems of oil and gas potential realization in Bazhenov-Abalak play in Khanty-Mansi Autonomous Okrug – Yugra

This research aims to analyze problems related to resources, reserves and development of Bazhenov-Abalak oil and gas play and to find geological and technological solutions for bringing reserves into development commercially. This should stabilize oil production in Okrug on the level 210–215 million of tons. Geological, field and statistical data from V.I. Shpilman Research and Analytical Centre for the Rational Use of the Subsoil and Department of Subsurface Management & Natural Resources of Khanty-Mansi Autonomous Okrug – Yugra were retrospectively analyzed during this research. Oil production from Bazhenov-Abalak play using conventional technologies is still sub economic. Running experimental areas and test ranges for industrial approval of development efficiency enhancement technologies for Bazhenov-Abalak play are created on producing fields. Unfortunately, accumulated experience ends up inside oil companies. Undoubtedly, single initiatives of oilmen will not solve a problem of development of huge resources in Bazhenov formation.

Progress and prospects of EOR technology in deep, massive sandstone reservoirs with a strong bottom-water drive

The Triassic massive sandstone reservoir in the Tahe oilfield has a strong bottom-water drive and is characterized by great burial depth, high temperature and salinity, a thin pay zone, and strong heterogeneity. At present, the water-cut is high in each block within the reservoir; some wells are at an ultra-high water-cut stage. A lack of effective measures to control water-cut rise and stabilize oil production have necessitated the application of enhanced oil recovery (EOR) technology. This paper investigates the development and technological advances for oil reservoirs with strong edge/bottom-water drive globally, and compares their application to reservoirs with characteristics similar to the Tahe oilfield. Among the technological advances, gas injection from the top and along the direction of structural dip has been used to optimize the flow field in a typical bottom-water drive reservoir. Bottom-water coning is restrained by gas injection-assisted water control. In addition, increasing the lateral driving pressure differential improves the plane sweep efficiency which enhances oil recovery in turn. Gas injection technology in combination with technological measures like channeling prevention and blocking, and water plugging and profile control, can achieve better results in reservoir development. Gas flooding tests in the Tahe oilfield are of great significance to identifying which EOR technology is the most effective and has the potential of large-scale application for improving development of deep reservoirs with a strong bottom-water drive.

STUDY OF THE EFFICIENCY OF OIL DISPLACEMENT PROCESS BY POLYMERS OF DIFFERENT GRADES

Currently, a large number of fields with high-viscosity oil are being developed. Increasing the degree of oil recovery from the subsoil of developed fields using effective methods of active influence is an important scientific and technical task for employees of oil producing enterprises. One of the most effective and promising methods for stabilizing oil production is physical and chemical technologies based on the injection of polymer compositions. Therefore, the authors of the article pursue the goal - to investigate the effectiveness of the use of polymer compositions for further recommendation for use in fields with high-viscosity oils and formations containing hard-to-recover reserves. The article provides an analysis of the results of the study of polymers, namely GL-50 and R-1 on rock samples of various well depths. In this regard, an experiment was carried out to displace oil with various displacing reagents. During the oil displacement experiment with various displacement reagents, the water saturation of the sample and the displacement efficiency were determined. Particular attention is paid to the rate of advancement of the flow of polymers and the propagation of molecules through pores of different diameters. The main goal of this experiment was to determine a more effective polymer for enhanced oil recovery. Comparison of oil displacement efficiency at the stages of polymer injection is given. In the course of the study, the results of determining the displacement coefficients of GL-50 and R-1 polymers were obtained. From the results obtained, it can be assumed that polymer grades have a significant impact on the degree of efficiency of the oil displacement process.

Remaining oil distribution characteristics in an oil reservoir with ultra-high water-cut

An accurate mapping and understanding of remaining oil distribution is very important for water control and stabilize oil production of mature oilfields in ultra-high water-cut stage. Currently, the Tuo-21 Fault Block of the Shengtuo Oilfield has entered the stage of ultra-high water cut (97.2%). Poor adaptability of the well pattern, ineffective water injection cycle and low efficiency of engineering measures (such as workover, re-perforation and utilization of high-capacity pumps) are the significant problems in the ultra-high water-cut reservoir. In order to accurately describe the oil and water flow characteristics, relative permeability curves at high water injection multiple (injected pore volume) and a semi-quantitative method is applied to perform fine reservoir simulation of the Sand group 3–7 in the Block. An accurate reservoir model is built and history matching is performed. The distribution characteristics of remaining oil in lateral and vertical directions are quantitatively simulated and analyzed. The results show that the numerical simulation considering relative permeability at high injection multiple can reflect truly the remaining oil distribution characteristics after water flooding in an ultra-high water-cut stage. The distribution of remaining oil saturation can be mapped more accurately and quantitatively by using the ‘four-points and five-types’ classification method, providing a basis for potential tapping of various remaining oil types of oil reservoirs in late-stage of development with high water-cut.

Low cost development strategy for oilfields in China under low oil prices

By reviewing the challenges in the development of oilfields in China under low oil prices, this study analyzes the root causes of cost rising, put forwards the low cost oilfield development strategy and specific paths to realize the strategy, and predicts the development potential and prospect of oilfields in China. In addition to the low grade of the reservoir and high development maturation, the fundamental reasons of development full cost rising of oilfields in China are as follows: (1) Facing the problem of resources turning poorer in quality, we have built production capacity at a pace too fast before making enough technical and experimental preparation; (2) technical engineering service model leads to high service cost; (3) team of oil development expertise and matched engineering system cannot satisfy the technical requirements of stabilizing oil production, controlling water cut and fine development. To realize development at low cost, the core is to increase economic recoverable reserves. The concrete paths include: (1) to explore the “Daqing oilfield development culture”, improve the ability of leaders in charge of development, and inspire potential of staff; (2) to improve the ability of reservoir dynamics control, and implement precise development by following scientific principles; (3) to speed up integration of water flooding and enhanced oil recovery (EOR) and technological upgrading in order to enhance oil recovery; (4) to innovate key techniques in gas flooding and accelerate the industrial popularization of gas flooding; (5) to break the related transaction barriers and create new management models; and (6) to collaboratively optimize strategic layout and cultivate key oil bases. Although oilfield development in China faces huge challenges in cost, the low-cost development strategy will succeed as long as strategic development of mature and new oil fields is well planned. The cores to lower cost are to control decline rate and enhance oil recovery in mature oil fields, and increase single well productivity through technical innovation and improve engineering service efficiency through management innovation in new oil fields.

Reservoir production optimization based on surrograte model and differential evolution algorithm

Production Optimization is a significant method for oilfields to control water cut and stabilize oil production. When the oilfield enters the high or ultra-high water cut stage, it becomes particularly important to use production optimization methods for improving the water-flooding efficiency. Currently, the commonly used production optimization methods are based on reservoir simulators. Such methods require lots of forward simulations during optimizing, which results in low computational efficiency. It's not applicable to the reservoir without numerical simulation models. Thus, a new production optimization method based on the reservoir proxy model is proposed in this work. Firstly, the dynamic production data of the oilfield are collected and preprocessed for training the Extreme Gradient Boosting model, and constructing the proxy model for water cut prediction of producers and the reservoir. Then, an optimal control model for minimizing the water cut of the reservoir can be constructed based on the proxy model. Finally, an optimal injection-production scheme can be obtained by using the differential evolution algorithm. For the evaluation and verification purposes, the proposed method is applied to a well block from SL oilfield, China. Empirical results demonstrated that the proposed method can effectively improve the water-flooding efficiency. • A proxy model based production optimization framework was proposed in this work. • The XGBoost based proxy model was established to predict the water cut of wells. • DE is introduced to solve the optimal model constructed by proxy and constraints. • The proposed method effectively optimize and improve the water-flooding efficiency.

Coordinated Development Mode of Oil and Gas Resources and Water Resources in Western China

Western China is an important area for increasing oil and gas reserves and production in China, and it is also the most arid and water-deficient area in the country; there is a complex linkage between energy and water resources in this region. Hence, it is important to promote the coordinated management of energy and water resources. In this article, we review the prospects and deployment of oil and gas production in Western China, investigate the development mode and water utilization status of different oil and gas fields from seven companies of China National Petroleum Corporation in Western China, and analyze the guarantee risks of water resource and water environment during gas and oil development. The research shows that oil and gas production has steadily increased in Western China in recent years, and the consumption of fresh water in oil and gas fields has changed little, owing to the continuous improvement in sewage treatment and recycling efficiency. However, considering the progressive development of unconventional oil and gas resources, future oil and gas development in Western China is likely to significantly affect the surface and underground water systems. It is suggested to develop precise water injection and waterless fracturing technology to stabilize oil production and control water use, increase the recycling of produced water to strengthen scientific water management, and improve the comprehensive allocation guarantee system of water resources, so as to reduce the impact of oil and gas development on water system while ensuring water use security for energy industry, thereby realizing the coordinated development of energy and water resources in Western China.

МЕТОДЫ УВЕЛИЧЕНИЯ НЕФТЕОТДАЧИ НА МЕСТОРОЖДЕНИЯХ ЮГРЫ

Актуальность.Государственным балансом запасов в Югре учтено 482 месторождения углеводородного сырья (порядка 12 млрд т извлекаемыхзапасов).273 месторождения находятся в разработке, а 210 – на различных этапах исследования. Текущая выработанность месторождений составляет 61 %, а их текущая обводненность – выше 85 %. Современный этап характеризуется снижением добычи практически на всех объектах нефтедобычи и увеличением до 65–70 % долитрудноизвлекаемых запасов.Главной задачей предприятий ТЭК Югры – основной базы углеводородного сырья и нефтедобычи России –является стабилизация добычи нефти на достигнутом в 2018 г. уровне в 235–236 млн т/год. Решение этой задачи невозможно без применения инновационных технологий повышения нефтеотдачи пластов. Цель: анализ эффективности (с точки зрения дополнительной добычи) внедренных в производственном режиме третичных технологий повышения коэффициента извлечения нефти на месторождениях Югры. Объект. Особенности методов увеличения нефтеотдачи и их геолого-промысловые результаты на месторождениях Югры (2013–2019 гг.): физико-химических, гидродинамических, гидроразрыва пласта, бурения горизонтальных скважин, зарезки боковых стволов, обработкипризабойной зоны, а также прочих методов – геолого-технологических мероприятий по оптимизации работы фонда скважин. Методы:ретроспективный сопоставительный анализ выполненных скважино-операций методов увеличения нефтеотдачии дополнительной добычи нефти: физико-химических – 48016, гидродинамических – 23374, гидроразрыва пласта – 28454, бурения горизонтальных скважин – 11225, зарезки боковых стволов – 9010, обработки призабойной зоны – 44081, геолого-технологических мероприятий – 32123 операции. Результаты.Анализировались геолого-промысловые и отчетно-статистические данные Научно-аналитического центра рационального недропользования им. В.И. Шпильмана и Департамента по недропользованию ХМАО-Югры. В Югре наметилась тенденция стабилизации годовой добычи нефти. При этом доля дополнительной добычи нефти за счет применения методов увеличения нефтеотдачии геолого-технологических мероприятийувеличилась с 9,4 % в 2013 г.до 16,0 % в 2019 г. Наиболее массовыми методами интенсификации добычи и повышения нефтеотдачи являются физико-химические, обработки призабойной зоныи гидродинамические. Самыми эффективными методами, обеспечивающими дополнительную добычу, являются:бурение горизонтальных скважин,зарезка боковых стволови гидроразрыв пласта. Массовое применение методов увеличения нефтеотдачина разрабатываемых месторождениях требует усиления научного-технического обоснования оптимальных условий строительства и эксплуатации систем разработки. Доля трудноизвлекаемых запасов нефти составляет в среднем около 60 %, а по некоторым компаниям достигает 75–80 %, поэтому альтернативы развитию третичных методов повышения нефтеотдачи на месторождениях Югры сегодня нет.

Technological progress and development directions of PetroChina overseas oil and gas field production

This study reviews the development history of PetroChina's overseas oil and gas field development technologies, summarizes the characteristic technologies developed, and puts forward the development goals and technological development directions of overseas business to overcome the challenges met in overseas oil and gas production. In the course of PetroChina's overseas oil and gas field production practice of more than 20 years, a series of characteristic technologies suitable for overseas oil and gas fields have been created by combining the domestic mature oil and gas field production technologies with the features of overseas oil and gas reservoirs, represented by the technology for high-speed development and stabilizing oil production and controlling water rise for overseas sandstone oilfields, high efficiency development technology for large carbonate oil and gas reservoirs and foamy oil depletion development technology in use of horizontal wells for extra-heavy oil reservoirs. Based on in-depth analysis of the challenges faced by overseas oil and gas development and technological requirements, combined with the development trends of oil and gas development technologies in China and abroad, overseas oil and gas development technologies in the future are put forward, including artificial intelligence reservoir prediction and 3D geological modeling, secondary development and enhanced oil recovery(EOR) of overseas sandstone oilfields after high speed development, water and gas injection to improve oil recovery in overseas carbonate oil and gas reservoirs, economic and effective development of overseas unconventional oil and gas reservoirs, efficient development of marine deep-water oil and gas reservoirs. The following goals are expected to be achieved: keep the enhanced oil recovery (EOR) technology for high water-cut sandstone oilfield at international advanced level, and make the development technology for carbonate oil and gas reservoirs reach the international advanced level, and the development technologies for unconventional and marine deep-water oil and gas reservoirs catch up the level of international leading oil companies quickly.

Experimental research on novel oil displacement and profile control system for heterogeneous reservoir

Polymer flooding and surfactant/polymer flooding (SP flooding) were mainly focused on the improvement in oil–water flow ratio and the reduction in oil–water interfacial tension. Preformed particle gel (PPG) flooding was mainly focused on the reservoir heterogeneity improvement. Each of these technologies has its own limitations. Heterogeneous system flooding (HS–PP flooding) was proposed as a novel flooding method aimed to improve oil–water flow ratio and reservoir heterogeneity at the same time. The HS–PP flooding system was composed of PPG and polymer solution. HS–PP flooding, polymer flooding and SP flooding as different chemical EOR methods were studied in laboratory in physical simulation heterogeneous model. Property of cubic expansion of PPG was researched by laser particle analyzer. The result shows that cubic expansion of PPG in simulation water is obvious and can be controlled. The effect of PPG on the diversion rate modification in double parallel sandstone model was obvious. The oil displacement experiments of the three different flooding systems with the same viscosity in physical simulation heterogeneous model were studied. The results show that the HS–PP flooding improves the oil recovery by 20.04%, comparing the result of 12.67% for polymer flooding and 16.66% for SP flooding, respectively. HS–PP flooding as a novel flooding method shows an excellent ability for stabilizing oil production and controlling water cut. The mechanism of the HS–PP flooding was discussed briefly. In addition to the viscoelastic displacement of polymers, the special circulation ability of “accumulating–deforming (collapsing)–accumulating again” of PPG is the main reason why the HS–PP flooding shows an excellent property for stabilizing oil production and controlling water cut.

Research and application of distribution characteristics of depositional sand bodies in delta-front facies under the condition of large area dense well pattern

Geological reserves in sedimentary unit of small channel sand developed in Gaotaizi reservoir cover 38% of their proved reserves, about 50% of penetration wells are perforated, most of the oil is not recovered, it seriously affects the development effect, in order to produce remaining oil, increase reservoir producing degree, and realize Gaotaizi reservoir fine potential tapping. This paper researches distributing feature of sedimentary sand bodies of in Gaotaizi reservoir and water control and the method for potential tapping by sue of core data and abundant well logging curves, based on analysis of sedimentary facies and logging facies, boundaries of sedimentary units of Gao I reservoir group 1-9 are unified through stratigraphic correlation. The microfacies of the studied area are divided into such three types: subaqueous distributary channel microfacies, sheet sand and subaqueous interdistributary channel microfacies. Based on the detailed study of reservoir thickness, logging curve features, lithologic character, sandbodies and depositional genesis, subaqueous distributary channel and delta front sheet sand microfacies are subdivided into 4 relatively homogeneous units, so as to further reveals the channel sand and sheet internal heterogeneity. Six plane maps sedimentary microfacies of the studied area are drew. It reveals connecting relation of sandbody and describes the sandstone distribution, which can establish geological foundation for identification of high water channel, analysis of injection - production problem and development adjustment scheme design. These methods are used to guide for water control and potential tapping, and the obvious effect of stabilizing oil production by controlling water-cut is shown.

Subsection Optimization Method Research of Slotted Screen Liner Parameters for Horizontal Wells

The slotted screen liner parameters are the same along the whole horizontal wellbore for most slotted Screen Liner completion of horizontal well, it will lead to water prematurely appears and the high water cut in high permeability area, so the research of subsection optimization for slotted screen liner parameters of horizontal well is important, which can adjust the inflow profile along the whole horizontal wellbore to enhance oil recovery, stabilize oil production and control water cut. Based on the skin factor model of slotted screen liner and the inflow control principle of horizontal wellbore, a subsection optimization model for slotted parameters of horizontal wells in heterogeneous reservoirs is established, and the subsection optimization design of horizontal well slotting parameters in heterogeneous reservoirs is realized by genetic optimization algorithm.

Research of phenolic crosslinker gel for profile control and oil displacement in high temperature and high salinity reservoirs

ABSTRACTTo further enhance oil recovery of high temperature and high salinity reservoir at Tahe Oilfield, field test results from profile control and oil displacement of gel were carried out in this article. Static and dynamic evaluations were performed through gel strength code method, environment scanning electron microscope, and physical simulation experiment devices. The field test results show that, under the conditions of high temperature (100.8 °C) and salinity (19.8 × 104 mg/L), the stable gel system was formed with gelling time range from 26 to 45 h, gel strength ranging from E to H, and dehydrating amount lower than 3.0% after ageing 60 days. Meanwhile, the microstructure is very stable. When the permeability and gel strength ranges from 0.212 to 0.970 μm2 and E to H, respectively, the plugging ratio is larger than 85%, and the plugging performance becomes better with the increase of permeability or gel strength. Due to the profile improvement rate of 99.8% and the oil recovery up to 28.5%, profile control and oil displacement technology of gel can effectively promote fluid diverting. The water cut reduced from 95.2% to 89.0% during field test carried out in Tahe Oilfield, which means that profile control and oil displacement technology of gel could stabilize oil production by water control effectively. Also, this technology has a wide application prospective that provides with strong technical support for further enhanced oil recovery in high temperature and high salinity reservoirs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46075.

The Synergistic Effect of Branched-Preformed Particle Gel and Hydrolyzed Polyacrylamide on Further-Enhanced Oil Recovery after Polymer Flooding

Polymer flooding is widely and successfully used to enhance oil recovery. How to further enhance oil recovery after polymer flooding becomes an important question that needs to be solved to stabilize oil production. Branched-preformed particle gel (B-PPG) is a newly developed chemical agent to enhance the oil recovery from heterogeneous reservoirs. Here, laboratory experiments were performed to investigate the enhanced oil recovery of B-PPG/hydrolyzed polyacrylamide (HPAM) mixed solutions through heterogeneous porous media by the core flood test. The results show that the B-PPG/HPAM mixed solutions have a higher oil recovery than solutions containing HPAM or B-PPG alone because of the synergistic effect between B-PPG and HPAM. B-PPG can adjust flows in different permeability zones by its properties of blocking, deforming, and passing through the throat during flow, which can be proved by the fractional flow behaviors in the parallel-sandpack displacement test. HPAM can not only increase the viscosity of t...

A new mathematical model for horizontal wells with variable density perforation completion in bottom water reservoirs

Horizontal wells are commonly used in bottom water reservoirs, which can increase contact area between wellbores and reservoirs. There are many completion methods used to control cresting, among which variable density perforation is an effective one. It is difficult to evaluate well productivity and to analyze inflow profiles of horizontal wells with quantities of unevenly distributed perforations, which are characterized by different parameters. In this paper, fluid flow in each wellbore perforation, as well as the reservoir, was analyzed. A comprehensive model, coupling the fluid flow in the reservoir and the wellbore pressure drawdown, was developed based on potential functions and solved using the numerical discrete method. Then, a bottom water cresting model was established on the basis of the piston-like displacement principle. Finally, bottom water cresting parameters and factors influencing inflow profile were analyzed. A more systematic optimization method was proposed by introducing the concept of cumulative free-water production, which could maintain a balance (or then a balance is achieved) between stabilizing oil production and controlling bottom water cresting. Results show that the inflow profile is affected by the perforation distribution. Wells with denser perforation density at the toe end and thinner density at the heel end may obtain low production, but the water breakthrough time is delayed. Taking cumulative free-water production as a parameter to evaluate perforation strategies is advisable in bottom water reservoirs.