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Scale formation due to the mixing of injection water with formation water causes formation damage and reduction in petroleum production. By using scale inhibitors, scale formation/scaling could be prevented. In this work, static experiments were performed with rapid controlled precipitation tests, which were undertaken using three different scale inhibitors namely Falat scale inhibitor, Scahib 760 scale inhibitor and Scahib 780 scale inhibitor. Results show that parameters such as temperature and pH have significant effects on scale inhibitor efficiency. In this study, at pH of 7.8–9 it was found that an increase in pH can lead to a decrease in SI efficiency. In addition, acquired data shows that Falat scale inhibitor is more efficient at 45 °C but scale inhibitors (Scahib 760, 780) have better efficiencies at 25 °C. SEM tests were performed to find structure deformation and morphology of precipitation crystals, which indicated that scale inhibitor can have various effects on crystal's shapes. Finally, dynamic tests were performed with coreflood equipment that indicated higher recovery by using the scale inhibitors. The dynamic tests results show that the recovery factor in the presence of Scahib 760 scale inhibitor is about 58% and breakthrough time is 2099 (sec). In the absence of scale inhibitor, the recovery factor is about 52% and breakthrough time is 2720 (sec). Keywords: Scale inhibitor, Formation damage, Scaling index, Static test, Dynamic test, SEM test

Air-breathing high-temperature proton exchange membrane fuel cell (HT-PEMFC) gets rid of the cumbersome air supplying systems and avoids the water flooding problem by directly exposing the cathode to air and operating the fuel cell at elevated temperature. Performance of the air-breathing HT-PEMFC is dependent on many factors particularly the cathode flow field configurations. However, studies about air-breathing HT-PEMFCs are quite limited in the literature. In the present study, an experimental testing system was setup for the performance measurement of the air-breathing HT-PEMFC. A 3D numerical model was established and validated by the experimental data. Effects of the cathode flow field configurations including the opening shape, end plate thickness, open ratio and opening direction on performance of the air-breathing HT-PEMFC were experimentally and numerically investigated. It was found that the cathode end plate thickness and upward or sideways orientation have the least effect on the performance. The maximum power density of 160 mW/cm2 at the current density of 394 mA/cm2 can be achieved for the cathode flow field with slot holes and an open ratio of 75%.

For unconventional reservoirs, water flooding performs poorly because of low displacement efficiency; gas flooding shows limited enhanced oil recovery (EOR) capability due to gas breakthrough. Carbonated water injection (CWI) and active CWI (ACWI) are promising EOR methods which combine advantages of water and gas flooding. This paper provides experimental and numerical studies of carbonated water and surfactant injection based on a case study in Changqing Oilfield, China, which is the first time to investigate the feasibility of CWI and ACWI for tight oil reservoirs. This study compares performances of active water injection (AWI), CWI, Water altering gas (WAG), and ACWI. Experimental results reveal that the oil recovery of CWI is 2.7% more than WAG. ACWI achieves the highest incremental oil recovery (9.43%) among four methods. The sensitivity analyses of ACWI + WAG is further implemented experimentally, which demonstrates that ACW as a pre-flood improves 7% of oil recovery during WAG process. For Changqing tight reservoir cores, the optimal injection volume of ACW is 0.8 pore volume. Numerical simulations are conducted to validate the capability of cubic Equation-of-State coupled with Henry's law (EOS/H model) for CWI in tight oil reservoirs, indicating EOS/H model is applicable to correlate phase behavior of carbonated water and oil system. This paper, for the first time, investigates the EOR performance of ACWI in tight oil reservoirs. These results explore the feasible application of using CWI/ACWI in tight oil reservoir development.

Heavy oil recovery is the most challenging part for the petroleum industry, and several techniques including steam and water injection are currently used that are either energy intensive, expensive, or less efficient. This study aims to evaluate a novel amphiphilic viscosity reducing polymer (DN-1) used along with hot water flooding for promoting viscous oil mobilization. Its performance for heavy oil mobilization was evaluated using viscosity measurements at different temperatures followed by core flooding experiments. Our results indicate that DN-1 at low concentrations could form 3D networks and stable aggregates. DN-1 featured good interfacial properties including low CMC, low IFT, and small contact angle. Even at low concentration it could form dynamic oil in water emulsions, thereby causing easy emulsification and fast demulsification. The injection pressure of DN-1 was much smaller than that of the conventional polymers or associative polymers used for heavy oil development and is beneficial for oi...

Time-lapse (4D) seismic is widely deployed in offshore operations to monitor improved oil recovery methods including water flooding, yet its value for enhanced well and reservoir management is not fully realized due to the long cycle times required for quantitative 4D seismic data assimilation into dynamic reservoir models. To shorten the cycle, we have designed a simple inversion workflow to estimate reservoir property changes directly from 4D attribute maps using machine-learning (ML) methods. We generated tens of thousands of training samples by Monte Carlo sampling from the rock-physics model within reasonable ranges of the relevant parameters. Then, we applied ML methods to build the relationship between the reservoir property changes and the 4D attributes, and we used the learnings to estimate the reservoir property changes given the 4D attribute maps. The estimated reservoir property changes (e.g., water saturation changes) can be used to analyze injection efficiency, update dynamic reservoir models, and support reservoir management decisions. We can reduce the turnaround time from months to days, allowing early engagements with reservoir engineers to enhance integration. This accelerated data assimilation removes a deterrent for the acquisition of frequent 4D surveys.

Reservoir relative permeability is greatly important to the development of water flooding reservoirs. Currently, most researches on relative permeability have not taken the roughness of pore surface and actual fluid distributions into consideration. In this paper, a novel relative permeability model for water flooding reservoirs taking the roughness and actual fluid distributions into consideration has been proposed by using the fractal theory. The novel model contains some key parameters, all of which have clear physical meanings, such as the immobile liquid film thickness, relative roughness, tortuosity fractal dimension $$ D_{\text{T}} $$ and pore fractal dimension $$ D_{\text{f}} $$ . The predicted results of the novel fractal relative permeability model are consistent with published experimental data. That verifies the correctness of the novel fractal relative permeability model. Finally, sensitive factor analysis of novel relative permeability model is conducted. We can find that the wetting fluid relative permeability decreases as the immobile wetting fluid film thickness or relative roughness increases. When the tortuosity fractal dimension or pore fractal dimension increases, the wetting relative permeability and non-wetting relative permeability will both decrease. An increase in maximum pore diameter or the decreasing of minimum pore diameter results in the reduction in fractal dimension of flow channel and discontinuous saturation. The increasing of maximum pore diameter results in an increase in the relative permeability of wetting fluid. The minimum pore diameter has tiny effect on the relative permeability.

Carbonated water injection (CWI) might be an efficient alternate to CO2injection technique. In CWI, CO2exists as a dissolved phase and not as a free phase; thus, it eliminates some challenges encountered in CO2injection such as poor sweep efficiency and gravity segregation. In CWI, the density and viscosity of water become higher than normal due to the CO2dissolution, thereby reducing the gravity segregation and channeling effect. This article is a comprehensive review on how carbonated water flooding has evolved over the time and captured salient features on the mechanisms involved in its role in enhanced oil recovery. The aspects reviewed in this article include a brief comparison of conventional CO2injection and carbonated water injection and the benefits thereof. Solubility of CO2in water, brine and oil phases is discussed in detail with valid correlations. A brief history of the development of CWI in the laboratory and field information is captured from 1905s to the present followed by the possible mechanisms and principle of CWI reported by various authors. This article also captured the latest findings on the beneficial effect of hybridizing CWI with smart water technologies.

Corner-point is an industry-standard type grid for application in reservoir simulation. The flexible gridding in corner-point grids provides several advantages over Cartesian grids for the representation of complex geological features. In this work, an embedded discrete fracture model (EDFM) is extended to corner-point grids with a full-permeability-tensor formulation to simulate complex fractures in this type of grids. The developed model is implemented in an IMPEC, compositional reservoir simulator. We first describe the formulations of the full-permeability-tensor implementation together with the modified governing equations for EDFM simulations. Then, we present methodologies for computing matrix-fracture intersections and fracture-fracture connections in the EDFM considering the various block geometries in corner-point grids. Subsequently, case studies are presented to verify the developed model, where the impacts of grid distortion and cross derivatives on simulation results are discussed. Three-dimensional case studies are also shown to illustrate the influence of natural fractures on secondary recovery. The results of this study demonstrate the reliability of the developed model, and they also show the compatibility of the EDFM with different types of numerical solution schemes in existing simulators.

This paper described an investigation into the properties of water-in-heavy oil emulsion and its role in enhanced oil recovery (EOR). Effect of pH and salinity on emulsion stability, droplet size and distribution as well as rheological behavior were researched. Core flooding experiments were conducted to study the role of emulsion on EOR. Results indicated that stability of emulsions decreased as salinity increased. The presence of salt leads to a rise in droplet size and a drop in uniformity of distribution. Besides, emulsion formed at pH of 7 was characterized by the least stability, largest droplet size and unevenest droplet size distribution. An increase or decrease in pH both improved emulsion stability and reduced droplet size. Equally, rheological property of emulsion was greatly affected by salinity and pH. In relatively low shear rate region (

The never ending challenge for petroleum engineers is to improve recovery from existing reservoirs. One promising and relatively low cost method for improving recovery is low salinity (LS) waterflooding. Previously [1], we studied the effects that divalent cations (Ca2+ and Mg2+) in formation water (FW) have on LS water EOR tests, and we found that higher concentrations of divalent cations generally and specifically Ca2+ in FW lowered the performance of LS water EOR. In this study, we probe the significance of the Ca2+ and Mg2+ concentrations in the injected LS water. We also measured the wettability index to investigate the wettability alteration resulted after changing the divalent cations concentrations. Berea sandstone cores were saturated with oil and connate FW. Each core was flooded with two pore volumes (PV) of FW followed by two PVs of various LS waters at reservoir temperature (90 °C). During flooding, aqueous samples of the effluent were analyzed for pH, Ca2+ and Mg2+ concentration. Six LS water flood cases were investigated: (a) 3× dilution of Ca2+ with original Ca2+ concentration; (b) 3× dilution of Mg2+ with original Mg2+; (c) 3× dilution of both Ca2+ and Mg2+; (d) 10× dilution of Ca2+ with original Ca2+ concentration; (e) 10× dilution of Mg2+ with original Mg2+; (f) 10× dilution of both Ca2+ and Mg2+. Overall, both Ca2+ dilution cases achieved a positive LS effect (higher incremental oil recovery), with the 10× Ca2+ dilution producing a larger effect than the 3× dilution. The Mg2+ dilution cases produced either zero or small LS effects. When both Ca2+ and Mg2+ were diluted, there was a positive LS effect but less than for just Ca2+. The presence of Mg2+ inhibited the full benefit of the Ca2+ dilution.

The low salinity water injection has become one of the most important studies in the oil industry for improving oil recovery compared to conventional seawater injection. Thus, extensive studies hav...

In Proton Exchange Membrane Fuel Cell (PEMFC) heat and water are generated as a side production. The accumulated water leads to a decrease in PEMFCs' efficiency. Hence, water has to be removed in order to prevent flooding inside the cell. In this study, by using experimental transparent Gas Diffusion Layer (GDL) water transport in PEMFC is visualized, and the capillary fingering mechanisms are studied. The effect of adding Micro Porous Layer (MPL) on water flooding inside the GDL is also examined. The images of high-speed camera confirmed the characteristics of capillary fingering in the GDL. It is observed that lateral flow on the surface of Catalyst Layer (CL) leads to an increase in water flooding in GDL while PEMFC efficiency is decreased. By using the MPL and increasing its thickness, the amount of lateral flow on the CL is decreased, and the generated fingers are entered into the GDL at specific discrete locations on the surface of the MPL. In this condition, the fingers choose straight paths to reach the gas channel (GC). Adding the MPL, with a maximum thickness of 2 cm, leads to a 51.5% reduction in the expansion length of the penetrating fluid inside the GDL in comparison with the GDL without MPL. Also, at the end of the test, the residual volume of the non-wetting fluid inside the GDL and MPL layers is measured. By employing the MPL and increasing its thickness, the volume of the non-wetting fluid inside the cell is reduced down to 38% which causes a decrease in saturation level of water in the GDL, and the cell performance is also improved.

In order to develop methods to further enhance oil recovery after water flooding in low permeability reservoirs by improving oil displacement efficiency, the displacement mechanism of residual oil ...

Water-oil relative permeabilty information of hydrocarbon reservoir rocks plays important roles in various modeling activities related to reservoir modeling and production forecast. The imbibition relative permeability scheme - the process of concern in this study affects many dynamic processes in reservoir. Water flooding and water encroachment form aquifer to oil zone in the reservoir are two two examples which representation in reservoir model requires the data. This study uses the standard Corey relative permeability model as a tool to study and model imbibition relative permeability behaviour of some reservoir rocks in Indonesia. Laboratory data from as many as 340 rock samples - sandstones and limestones - of various permeability and wettability from various oil fi elds in Indonesia is used. Activities in the modeling has pointed out the need to introduce two new empirical factors that relate to rock wettability and non- wetting fl ow hindrance to the model. The two factors appear to have signifi cantly improved the ability of the model to agree and match to the measured data. The modeling also produces suggested values of the factors for rock groups based on rock wettability type and strength, as well as on permeability categories. Comparison between modeling results before and after modifi cation has shown signifi cant improvement in validity of output.

The Vankor oil field is in the third stage of the development. Well stock mostly includes horizontal and directional wells. Analysis of the field development showed that actual development rate is much higher than planned. Energy potential of the field is drained out due to formation pressure decline and water flooding. New technologies for restoring well productivity, such as acid treatment and hydraulic fracturing should be introduced to maintain planned development rate. Drilling multilateral wells should be used as main enhanced oil recovery technique.

Water flooding and gas injection are two traditional secondary development methods for tight oil reservoirs. Water injection has the problem of small injectivity due to low permeable reservoir matrix while gas injection brings about severe breakthrough because of obvious viscosity difference between gas and oil. These traditional approaches that supplement energy between wells are not highly effective. To fill this gap, this paper proposes an efficient energy-supplement method, continuous in-situ injection and production (CIIP), among fractures for multistage fractured horizontal well (MFHW) in tight oil reservoirs. CIIP divides hydraulic fractures into two kinds, in which odd fractures are used for production while even fractures are for injection. CIIP has three main advantages over traditional water flooding: firstly, it switches displacement interval from between injection and production wells to between hydraulic fractures; secondly, CIIP has a better injectivity compared to traditional water flooding at the same injection pressure; and thirdly, CIIP improves sweep efficiency thereby improving oil recovery. In this paper, a workflow is developed to evaluate the performance of CIIP in a case study. Reservoir properties and micro-seismic (MS) mapping data are analyzed to provide fundamental parameters for building a numerical simulation model, and then history matching is achieved to validate the model. The simulation considers two scenarios of hydraulic fractures: the uniform and non-uniform fractures. Uniform-fracture simulation aims to investigate the mechanisms of CIIP under three fracture models; different fracture half-lengths and the situation of existing high permeable channels between injection and production fractures are also included in uniform-fracture simulation. Non-uniform-fracture simulation, whose fractures are interpreted according to MS mapping results, is devised to demonstrate CIIP’s superiority in a realistic way. This study is based on a theoretical approach and the results wait to be further proven in the field. Simulation results demonstrate that CIIP is an efficient energy-supplement method. It helps to maintain reservoir pressure near the initial condition during the thirty-year simulation. Meanwhile, even if ten injection wells are added, CIIP still injects 55% more water than water injection (WI) at the same injection pressure. Uniform-fracture simulation indicates that CIIP has a 2.23% more oil recovery than WI and a 3.74% than depletion. Besides, the influence of high permeable channels between injection and production fractures is insignificant and we can still expect CIIP’s good performance when hydraulic fractures hit local natural fractures. The non-uniform-fracture simulation demonstrates that CIIP performs well too when hydraulic fractures are randomly distributed. It also finds outs that the presence of primary fractures in which proppant concentrates is essential to CIIP while the role of natural fractures is trivial compared to the hydraulic fractures. In a word, CIIP is a promising technology for tight oil reservoir development.

Aim at solving the problem on the time-variant of reservoir parameters such as permeability and porosity during the water flooding process of sandstone reservoirs and the lack of microscopi...

Water flooding type-curves, recently receiving increasing attentions, play an essential role in evaluation of OOIP and prediction of future production. The study proposed a method modified form Weibull model and water flooding type-curves to analyze the reservoir production performance, including predication of oil production and water injection rates. The results indicate that the method can estimate and provide solutions for oil production, water injection rate and injection-production ratio with a well accuracy. A case study is conducted to demonstrate the applicability and accuracy of model by field data. The matching results illustrate a good accordance between calculated values and field data. Keywords: Weibull model, Water flooding type-curves, Oil production, Water injection rate, Injection-production ratio

Low-salinity water flooding (LSW) is a promising new technique for enhancing oil recovery (EOR) in both sandstone and carbonate reservoirs. The potential of LSW has drawn the attention of the oil industry in the past decade. Along with the few successful field applications of LSW, various studies in this field in recent years have been conducted mainly at the lab scale. The main objective of this critical review was to investigate the potential of this EOR technique in improving oil recovery and the mechanism under which it operates. As a result, various mechanisms have been proposed. However, no consensus on the dominant mechanism(s) in neither sandstones nor carbonate reservoirs has been reported, and the oil industry is continuing to discover the leading effects. Herein, we provide the chronicle of LSW, analysis of the proposed mechanisms of enhancing oil recovery using LSW in recent findings, some laboratory observations, and finally, some successful field applications. From this review, despite the promising potential justified by both laboratory studies and field applications, there exists a large number of unsuccessful field case studies. LSW is viewed as an immature EOR technique with many ambiguities because definitive conclusions about which mechanism(s) is responsible for improving oil recovery remains elusive and a bewilderment to the oil industry.

Aiming at the problem that the heterogeneity of the reservoir became strong, the remaining oil distributed universally after polymer flooding and the existing chemical compound flooding systems had limited application, a heterogeneous compound flooding system based on gel dispersion particles (DPG) was proposed as a substitution technology for further enhanced recovery of reservoirs after polymer flooding. This paper has carried out the design and characterization of heterogeneous compound flooding system, influencing factors, and application performance. With the system viscosity and oil-water interfacial tension as evaluation indicators, the application performance of the optimized heterogeneous polymer flooding system based on DPG was examined. The results showed that the system viscosity was 12.1 to 17.3 mPa•s while the interfacial tension was maintained at 10 -3 mN/m magnitude. At 80 °C, with 60 days aging, the viscosity retention ratio of the system is over 83.5%, and the interfacial tension between oil and water was still maintained at 10 -3 mN/m. The core flow experiment shows that, the heterogeneous compound flooding system has good injection performance, moving characteristics of plugging, breakthrough migration and re-plugging. After high-temperature aging, subsequent water flooding still maintained at a high pressure with good resistance to erosion. Through the selective high and low permeability layers, the water absorption profile was improved, and finally enhanced oil recovery to 20.61% after polymer flooding. Cited as : Li, H., Wang, K., Han, X., Zheng, J. Research on heterogeneous compound flooding system based on dispersed particle gel. Advances in Geo-Energy Research, 2019, 3(2): 156-164, doi: 10.26804/ager.2019.02.05

Emulsions play an important role in enhancing oil recovery during the reservoir flooding process. In order to reveal the profile control ability and the effect of adjustments to the interlayer interference during the migration of the emulsion in the porous media, a stable emulsion system and an alkali-surfactant-polymer (ASP) system were selected to simulate the underground emulsification process by verifying influencing factors of the emulsion. A parallel-core displacement experiment was used to investigate the oil displacement efficiency and the difference of fractional flow in each layer under different emulsification degrees and different permeability contrasts. The results indicate that the stability of the emulsion is related to the shearing strength, the water content, and the type and concentration of chemical system. The oil displacement efficiency of emulsion flooding is better than that of ASP flooding. For parallel core with an average permeability of 40 mD and a permeability contrast of 2, the emulsion flooding can enhance oil recovery by 21.16% compared to water flooding. With increasing permeability contrast, the oil recovery percent of emulsion flooding will further increase. The emulsion system has good profile control ability. Within a certain range, the stronger the heterogeneity of porous media, the better the effect of emulsification on the adjustment of the interlayer interference.

This paper presents a three-dimensional geological modeling method for low permeability reservoirs based on core, logging, seismic, and dynamic data. Matrix and fractures are two types of reservoir space. This method includes two-step modeling methods, and different methods are used to establish a matrix model and fracture model. As a low permeability reservoir, Maxi Oilfield has entered the high water cut stage, and developing a precise three-dimensional structural model that can reflect the spatial distribution of the reservoir is an urgent task. First, the gravity flow channel deposition was determined by core observations and the characteristics of gravity flow reservoirs are described. On this basis, a three-dimensional quantitative geological model of the matrix is established using the sequential indicator simulation. The ant-tracking technique is used to identify the fracture development in Maxi Oilfield, and two groups of fractures, 50°–100° in an NE direction and 30°–35° in an NE direction, are identified as the main reservoirs. The discrete fracture distribution model is established deterministically, and then, the fracture model is modified by the distribution of fractures reflected comprehensively by the water flooding front, microseismic, and dynamic data. This three-dimensional structural model can guide the development of water injection wells in Maxi Oilfield.

This article presents an extensive relative permeability study for low salinity water flooding (LSWF) in minerally different carbonate rocks. The experiments were performed with unsteady state meth...

There is not a consistent view about the mechanism of wettability alteration during low salinity water flooding. This paper highlights extensive wettability studies to investigate the wetta...

All the time the flow of fluids happens below the surface of the earth. These flow processes can only be imagined, but not be fully visualised on how fluid flow behaviour occurs though the porous medium of the rocks. Hence comes the play of microfluidic micromodels. These are a transparent version of slices (2 dimensional) porous structure of rocks such as sandstone duplicated onto materials such as glass, polymers and silicon wafers. Fluids such as crude oil, surfactant and polymer solutions and gases such as carbon dioxide (CO2) are injected through special pumps into these transparent micromodels. The flow patterns and behaviours hence developed inside the micromodels are studied and analysed. Micromodels have helped in different branches of science such as medicine, genetics, liquid channelling and enhanced oil recovery (EOR). The concern of this paper is to study the flow behaviour and EOR in micromodels. Micromodels can be made to represent a micro version of a partially saturated rock with crude oil. The various chemical EOR processes such as surfactant flooding, polymer flooding, gas flooding injected into crude oil filled micromodels with water saturation is studied. The advancement of front developed between displacing and displaced fluids, the fingering effect, the presence of high permeability streaks is observed. Also the breakthrough of the flood front is analysed from the various experiments reviewed. This review paper is undertaken so as to help researchers find a consolidated and concise literature of the trends and developments in microfluidics especially in EOR.

In-depth water flooding profile modification is a new problem for low permeability formation under fracturing. Profile control study for in-depth cross flow which couples fracture and matrix is nei...

Low salinity water flooding appears to be an important means to improved oil recovery in sandstone reservoirs. Wettability alteration has been identified as the main effect behind low salinity wate...

In order to enhance the effect of polymer flooding in offshore oilfields, so as to realize the longer stable production period and higher oil recovery, the reservoir perforation positions of production wells and injection wells are taken as research objects. By analyzing the distribution of remaining oil and production characteristics under different perforation positions, the optimum perforation positions of production wells and injection wells are selected. Bohai oilfield L was taken as target oilfield in this article, according to the actual reservoir characteristic parameters, three-dimensional laboratory physical simulation experiments of water flooding and polymer flooding were carried out, the experiments include different perforation positions of production wells and injection wells. The research result showed that the influence of perforation position on residual oil and development characteristics of the model is obvious. When takes the scheme of injection well upper part perforated and production well all part perforated, the least of the remaining oil distribution, the longest of the production period without water. Contrast with other perforation schemes, its stable production period increase about 1.2 times, the oil recovery of water flooding increase 3.7% - 6.0%, the oil recovery of polymer flooding increase 2.5% - 4.1%. So it is recommended as the best perforation scheme. Preferable effect had been achieved when translating research findings into practice. It can serve as a reference to the similar offshore oilfield.

The aim of this paper is to solve the problems that the existing method of critical production of gas cap reservoir is only suitable for single-phase flow, and the method of critical production of gas cap reservoir under water-flooding is still blank. In this paper, the relationships between dynamic and static equilibrium, plane radial flow theory, oil-water infiltration method and three-dimensional seepage field decomposition theory, were applied to study a calculation method for critical production of directional wells and horizontal wells. Furthermore, the effects of different factors on critical output were studied, such as horizontal permeability, ratio of horizontal permeability to vertical permeability, length of horizontal section, effective thickness, viscosity of crude oil and water content etc. Results show that the critical production increases with the increment of the horizontal permeability, the ratio of the vertical permeability to the horizontal permeability, the reservoir thickness and the horizontal well length; when the viscosity of crude oil is small, the critical production decreases first and then increases with the increase of water content; when the viscosity of crude oil is high, the critical production increases continuously with the increase of water content. This study could provide theoretical and technical guidance for changing of the working system of oil wells. It can avoid gas channeling and improve the development effect.

Oilfield A is a fractured buried hill reservoir in Bohai bay of China. In order to solve the difficult problem of water flooding timing and method in oilfield. Considering the characteristics of the buried hill fractures with stress sensitivity and strong heterogeneity, the ECLIPSE software was used in the research, and a three-dimensional injection-production numerical model for horizontal wells in buried hill reservoirs is established. According to the main research factors in water flooding, a series of water flooding schemes are designed, and the optimization of water flooding timing, oil recovery rate and water flooding mode in buried hill reservoirs were carried out. The results show that the optimum pressure level of fractured reservoir is about 70% of the original reservoir pressure. The optimal water flooding method is the conventional water flooding in the initial stage, when the water cut reaches 80%, it is converted into periodic water flooding. The oil recovery is the highest when the water injection period is 4 months. Field tests show that conventional water flooding is carried out in the initial stage of the oilfield A when the pressure is reduced to 70% of the original. Periodic water flooding is carried out when water cut is 80%. Good development results had been achieved in the 10 years since oilfield A was put into production. The average productivity of single well reached 300 m3/d in the initial stage, at present, the water cut is 60%, and the recovery degree is 18.5%, which is better than that of similar oilfields. This technology improves the water flooding effect of blocky bottom water fractured dual media reservoirs in metamorphic buried hills, and provides a reference for the development of similar reservoirs.

This paper moves one step forward to build a numerical model to research quantitative characterization and dynamic law for interlayer interference factor (IIF) in the multilayer reservoir which was heavy oil reservoirs and produced by directional wells. There are mainly four contributions of this paper to the existing body of literature. Firstly, an equivalent simulation method of the pseudo start pressure gradient (PSPG) is developed to quantitatively predict the value of IIF under different geological reservoir conditions. Secondly, the interlayer interference is extended in time, and the time period of the study extends from a water cut stage to the whole process from the oil well open to produce a high water cut. Thirdly, besides the conventional productivity interlayer interference factor (PIIF), a new parameter, that is, the oil recovery interlayer interference factor (RIIF) is put forward. RIIF can be used to evaluate the technical indexes of stratified development and multilayer co-production effectively. Fourthly, the effectsof various geological reservoir parameters such as reservoir permeability and crude oil viscosity, etc. on the PIIF and RIIF’s type curves are discussed in detail and the typical plate is plotted. The research results provide a foundation for the effective development of multilayer heavy oil reservoirs.

In this paper we quantify the effect of capillary number ( Ca ) , contact angle ( θ ) and viscosity ratio ( M ) on the mobility of multiphase flow through porous media. The focus is mainly on oil-water flows through porous rocks observed during the water flooding process. Simulations are performed using a finite volume method employing a staggered grid formulation. Interactions between fluids and complex solid boundaries are resolved by a direct forcing, implicit and sharp interface immersed boundary method (IBM). The fluid-fluid interface is tracked by a mass conservative sharp interface volume of fluid (VOF) method. IBM and VOF are coupled by imposing the contact angle as a boundary condition at the three phase contact line. Our methodology has been verified/validated for several test cases including multiphase Poiseuille flow in a channel, a viscous finger in a channel and mesh convergence of the contact force. Two types of porous structures are considered: (i) a repeated single pore and (ii) a random multi-pore arrangement. Temporal evolution of phase pressure difference and oil saturation have been studied as viscous fingers penetrate the pores. We observed that the residual oil saturation for different capillary numbers shows exactly the opposite trend for the single and multi pore arrangement. The residual oil saturation for multi-pore shows a well defined linear trend with log Ca , θ and log M .

Primary and secondary recovery methods do not give the maximum oil recovery in certain oil fields, and have a high water cut. Enhanced oil recovery (EOR) methods can solve these issues. Polymer flooding that falls under chemical EOR is one of these methods. The mechanisms of polymer flooding leads to increasing the viscosity of the displacing fluid, water, and reduces the mobility to be lower than the displaced fluid, oil. This gives a better sweeping efficiency, which translates into higher oil recovery and lower water cut because of the delay of viscous fingering and water breakthrough. To select a suitable polymer for a particular field, parameters such as; polymer viscosity, concentration, slug size should be studied carefully. The aim of this study is to evaluate the polymer injection process, and to design an optimum polymer flooding scenario regarding improving the oil recovery factor and net present value (NPV) for X-oilfield in Iraq. The workflow of this study starts with building a reservoir model using Petrel software that fits a cited screening criteria. Then, designing a base case of a secondary recovery method of water flooding using Tnavigator software. After that, implementing a polymer sensitivity analysis, where scenarios with different concentration, viscosity, injectivity, slug size, and shear thinning are created. Finally, choosing a best-case scenario that represents the optimum oil recovery and NPV. The results of this study show that when polymer flooding was implemented compared to water flooding, with a concentration of 5000 ppm, viscosity of 8.5 cP, and slug size of 37.5% pore volume (PV), the oil recovery factor increased from 44.67% to 63.73%, and the NPV was increased from $9.6 billion dollars to $13.1 billion dollars. The results comply with the findings of several researchers.

Between 1996 and 2014, in the midst of the Colombian armed conflict, 117,326 internally displaced people settled in southwest Barranquilla. This article describes the process of rapid urbanization carried out by these communities. It narrates how, due to underinvestment in drainage and electricity infrastructure, flash-flooding and blackouts became frequent in southwestern barrios. Men from the community, known as marañeros (entanglers), built/repaired electricity networks. Subsequently, state regulations classified these settlements as “subnormal,” which meant that although they built their own connections, they had to pay communal bills for the energy extracted from municipal transformers. Communities became indebted and during periods of malfunction, when flashfloods damaged electricity infrastructure, marañeros were victims of accidental electrocution. I suggest that a close look at processes of infrastructural malfunction enables a critical understanding of the state’s active construction of marginality. Interconnected infrastructural malfunction is a form of state engagement, as the presence of precarious infrastructure is a direct action. Instead of narratives featuring state absence/failure, the routines of southwest Barranquilla lay bare the ways in which malfunction is reproduced through institutional channels. Specific regulations created a place of malfunction, and deficiencies in both electricity connections and drainage portray/reinforce racialized and gendered identities based on unequal power relations.

It has always been an urgent issue for the oil and gas industry to improve oil, gas, and condensate recovery at liquid and gaseous hydrocarbon fields developed with the use of artificial formation ...

This paper presents the viscosifying and oil recovery efficiencies of a novel high-molecular-weight ternary polyampholyte (TPA), composed of 80 mol.% acrylamide (AAm) (a nonionic monomer), 10 mol.% 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPS) (an anionic monomer), and 10 mol.% (3-acrylamidopropyl) trimethylammonium chloride (APTAC) (a cationic monomer), in various high-salinity brines as compared to the efficiency of hydrolyzed poly(acrylamide) (HPAM), which is the most commonly used polymer in oil production. The results show that, in a range of salinity from 200 to 300 g∙L−1, the viscosity of the TPA solution is rather high and relatively stable, whereas that of HPAM severely decreases. The ability of TPA to increase its viscosity in extremely high salinity brines is explained by the antipolyelectrolyte effect, resulting in the unfolding of macromolecular chains of charge-balanced polyampholytes at a quasi-neutral state, which occurs due to the screening of the electrostatic attraction between oppositely charged moieties. The novelty of this research is that, in high-salinity reservoirs, the amphoteric terpolymer Aam-AMPS-APTAC may surpass HPAM in oil displacement capability.

The crude oil in Zhundong Oilfield has good self-emulsification phenomenon. In order to reveal the mechanism, the crude oil was divided into saturated hydrocarbon, unsaturated hydrocarbon, resin and asphalt by chromatographic method, and their contents are 40.09%, 11.19%, 48.05% and 0.67%, respectively. The effects of the petroleum components on self-emulsification were investigated. The results show that the resin has the most important effect on emulsification and plays the role of emulsifier. The saturated hydrocarbon and unsaturated hydrocarbon act as the basic oil and cannot be emulsified with the injection water without the resin emulsifier. Moreover, the resin content is very important, only when it is in a proper proportion, the system can be well self-emulsified. This work is useful for water flooding.

Based on the similarity criterion, volcanic rock samples were taken from outcrops to make experimental models. Water flooding experiments of five-spot well pattern, nine-spot well pattern, five-spot to nine-spot well pattern, the relationship between relative well and fracture positions, and injection rate in dissolution vug-cave reservoirs with/without fractures were carried out to analyze variation regularities of development indexes, find out development characteristics of water flooding with different well patterns and sort out the optimal water flooding development mode. For dissolution vug-cave reservoirs without fractures, five-spot well pattern waterflooding has very small sweeping area, serious water channeling and low oil recovery. When the well pattern was adjusted from five-spot to nine-spot well pattern, oil recovery could be largely improved, but the corner well far from the injector is little affected. In dissolution vug-cave reservoirs with fractures, when the injector and producer are not connected by fractures, the fractures could effectively connect the poorly linked vugs to improve the development effect of water flooding. Whether there are fractures or not in dissolution vug-cave reservoirs, the development effect of nine-spot well-pattern is much better than that of five-spot well pattern and five-spot to nine-spot well pattern, this is more evident when there are fractures, and the edge well has better development indexes than corner well. At the high-water cut stage of water flooding with nine-spot well pattern, the oil recovery can be further improved with staggered line-drive pattern by converting the corner well into injection well. It is helpful to increase the oil production of corner well of nine-spot well pattern by increasing the injection rate, and improve ultimate oil recovery, but the water-free production period would be greatly shortened and water-free recovery would decrease. Key words: similarity criterion, dissolution vug-cave reservoir, water flooding, injection-production well pattern, well placement, injection rate, development index, oil recovery

Low salinity water flooding (LSWF) has been intensively investigated but the conditions for LSWF to work are still unclear and the EOR mechanisms are still debatable. In this study, we extracted data from hundreds of LSWF flooding tests using sandstone cores and sand packs that have been published to date (by January 2018), and analyzed the tertiary recovery results (202 groups) collectively. First, all initial experimental conditions are correlated to the tertiary recovery factors in both single and combinatorial manners. Correlation charts show that no single experimental condition constitutes necessary or sufficient conditions for incremental oil recovery; combinatorial conditions show stronger correlations with the recovery factors, but still do not constitute sufficient conditions for incremental oil recovery. Secondly, incidental property changes are correlated to tertiary recovery factors in order to evaluate the related EOR mechanisms. Wettability alteration towards more water-wet shows a strong correlation with improved oil recovery. Finally, all previously proposed EOR mechanisms for LSWF in sandstones are linked in a chart to demonstrate an in-depth overview of all these mechanisms. We use experimental data analyses to provide a solid basis for reviewing LSWF and provide unique perspectives in understanding this process.

Inspired by the successful implementation in acid fracturing, a fiber-loaded suspension system was designed to investigate inlet injectivity, in-depth mobility and overall plugging effect in unconsolidated high permeability sandpacks. In this paper, a series of experiments were conducted to screen suitable fiber suspension, including additives selection and dynamic plugging tests. Results showed that the formulation of 0.02 wt% citric acid+0.1 wt% YC regulator+0.1 wt% sodium tetraborate+0.12 wt% HPG displayed satisfactory dispersity. Sandpacks equipped with three pressure gauges to detect pressure changes were used for physical experiments. Four parameters (fiber length, fiber concentration, injection rate and permeability) that influenced the plugging efficiency were under discussion. The results revealed that relatively slow injection helped stabilize inlet pressure below upper limit. Three pressures increased in sequence during the subsequent water flooding, indicating that fibers moved forward with permeability reduction in sandpacks. The pressure dropped down but maintained at a high level after the operation finished. By comparison, 0.3 wt% 1000 μm-long fiber injected at the rate of 1 mL/min was found to achieve the best performance under the permeability of 4000–7000mD. And the more serious the heterogeneity was, the more significant the diversion ability of the high permeability layer was. Noticeably, the fluctuations were observed in pressure curves, which was further interpreted by the dynamic plugging mechanism of fiber in four transport processes: “migration-capture-redirection-recapture”. With unique slender shape, fibers were flexible enough to bridge and create a compact three-dimensional network structure along the flow direction. Due to high plugging strength and strong penetrability, the new fiber suspension system proves its potential to be an environmentally-friendly candidate in the selection of in-depth diverting agents. The evaluation and mechanism analysis may provide guidance for the operation design of profile control.