Effect Of Water Flooding Research Articles

Study on Reasonable Injection-Production Parameters of Water-Flooding Reservoir: A Case Study of Daqing Oilfield

This paper, by conducting comprehensive analysis on water-flooding reservoir, intensively studied and discussed the characteristics of geological development, determined the evaluation indexes of development effect, carried out research from five steps, the first is the introduction part, it conducted indepth study and discussion from research background, research significance, literature review, and research methods four aspects. The second outlined the related theory from the optimization principle and mechanism of injection-production parameters, and the distribution mechanism of remaining oil two aspects. The third analyzed the current situation of reasonable injection-production of water-flooding reservoirs in Daqing Oilfield from reservoir characteristics and reservoir deposition. The fourth evaluated the water-flooding development effect from combined water cut, changing conditions of production and predicted recovery ratio. The fifth intensively studied the reasonable injection-production parameters of water- flooding reservoirs in Daqing oilfield from design of separated layer water injection plan, maintaining level reservoir formation pressure, and reasonable plan of injection-production ratio and oil recovery rate three aspects, and provides theoretical guidance for later targeted excavation of water-flooding reservoirs.

Fuzzy Comprehensive Evaluation of Oil Field Waterflooding Effect

Oil field waterflooding is a complex man-controlled systematic behavior, and the related evaluation methods vary greatly. This paper put forward a fuzzy comprehensive method of evaluating controlled development level by analysis of the macroscopic evaluation to oil field waterflooding effect with combination of original reservoir geological state. This fuzzy evaluation technique bears unique advantages because there is little difference among evaluation indexes which represent the dynamic and static state of regional neighborhood of development units (blocks, Production Company, etc.). Not only the mathematical method for evaluating oil field waterflooding effect is set up, but also the method is applied in three blocks of D oil field. The calculated results show the effectiveness and practicability of the method.

Application of principal component analysis on water flooding effect evaluation in natural edge-bottom water reservoir

Water flooding effect evaluation is considered as the basic work to formulate comprehensive adjustment measures and improve the effectiveness of oilfield development. However, natural edge-bottom water energy is seldom considered in the conventional evaluation method. So, it cannot reflect the comprehensive effect of both natural edge-bottom water and injected water. Principal component analysis is a kind of multivariate statistical analysis method, which has been widely used in social science and other fields. Based on this method, the water flooding effect of 5 edge-bottom water reservoirs is comprehensively evaluated. First, 11 indicators are selected from four aspects, including natural edge-bottom water energy, production change, water injection development and utilization, energy maintenance and deficit compensation. Then, the selection of principal components is optimized. Based on the consideration of keeping as much information as possible to get more convincing results, three principal components are obtained. Finally, take five oilfields as examples to realize comprehensive evaluation. Results indicate that the natural energy of B oilfield is quite sufficient and water injection is timely in the later stage of development. So the water flooding effect is the best among five oilfields and the comprehensive principal component value is 1.434. That of A and C oilfields are 0.527 and 1.021, respectively, ranking 3 and 2. Although D oilfield has quite sufficient natural energy, water injection is not timely. So the water flooding effect is poor and the comprehensive principal component value is 0.259. That of E oilfield is − 3.241, indicating that it has the worst water flooding effect. The ranking results of five oilfields are consistent based on principal component analysis and Tong's chart, which are both B, C, A, D and E oilfield, verifying this method’s feasibility and practicability. Additionally, compared with the single index, it can reflect the comprehensive water flooding effect of both natural edge-bottom water and injected water. Specific oilfield cases are evaluated by the proposed method, which help for better understanding its application potential for evaluating the water flooding effect of natural edge-bottom water reservoirs.

Research on optimal timing range for early polymer injection in sandstone reservoir

In this study, lab research was performed to obtain a method to determine the timing for early polymer injection in oilfields, to increase applicability of lab research in actual oilfield management and to identify the optimum timing for polymer flooding to ensure efficient development of offshore oilfields. This study optimized the methods for lab experiments on oil displacement, analyzed the characteristics of two-phase flow permeability experiments, identified the effect of early polymer flooding, and found the method to decide the timing for early polymer flooding applicable to real-world oilfield management. The research result shows that there is optimum timing for early polymer flooding: in the case that a reservoir’s oil viscosity is 70mPa⋅s, the optimum timing is when the water cut is within the range from 0% to 40%. The water cut increase rate and the water/oil mobility ratio are key factors to the performance of polymers in mobility control: the best control effect can be achieved when the water/oil mobility ratio is below 1 and before the water cut increase rate reaches the maximum. Before polymer flooding, injection of a certain volume of water can unclog the channels, give full play to the effect of waterflooding, reduce the pressure of polymer injection, and cut the loss of effective viscosity of the polymer solution. In actual oilfield development, it is feasible to predict and monitor changes in the oil productivity index and take the timing of sharp decrease of the index as the optimum timing for polymer flooding.

Pore scale experimental and numerical study of surfactant flooding for enhanced oil recovery

Surfactant flooding is a traditional method to enhance oil recovery. The surfactant flooding experiment based on glass etching model allows researchers to observe directly how the remaining oil is displaced by surfactant through microscope, so as to explore the mechanism of surfactant enhanced oil recovery. However, microscopic experiments mostly stay at the level of physical experiments, and the operation of physical experiments is too complex and cumbersome. This study is the first to combine surfactant flooding experiment with numerical simulation in glass etching model. Firstly, based on the real pore and throat structure of the real low permeability reservoir core, the glass etching model was developed, and the micro-oil-water displacement experiment was carried out. Through microscopic observation and analysis, combined with testing and image processing technology, the effect of water flooding was quantitatively investigated. Then the surfactant flooding was carried out. Three surfactants were used for displacement. It was found that residual oil in pore network was greatly reduced. The recovery factor has been greatly improved. Finally, numerical simulation of water flooding and surfactant flooding based on micro-physical experiment was carried out. The results of numerical simulation were compared with the experimental results. It is found that the recovery factor and the form of residual oil are basically the same. By analyzing the results of numerical simulation of oil recovery, it is found that the extent of surfactant enhancing oil recovery is different under different interfacial tension. The results showed that the surfactant with interfacial tension of 0.22 mN/m has the highest ability to enhance oil recovery. This work provides a reference for surfactant selection in oilfield development. It can select the best surfactant according to the factors of time, efficiency and cost.

Experimental Investigation of the Effects of Water and Polymer Flooding on Geometric and Multifractal Characteristics of Pore Structures

During water and polymer flooding for enhanced oil recovery, pore structures may vary because of the fluid–rock interactions, which can lead to variations in petrophysical properties and affect oil field production. To investigate the effects of fluid flooding on pore structures, six samples were subjected to brine water, dual-system, and alkaline–surfactant–polymer (ASP) polymer displacement experiments. Before and after experiments, samples were scanned by X-ray CT. Thin sections, X-ray diffraction, and high pressure mercury injection tests were also carried out to characterize mineralogy and fractal dimension of pore systems before experiments. Experiment results show that water flooding with low injection pore volume ratio (IPVR) can improve reservoir quality since total porosity and connected porosity of samples rise after the flooding and the proportion of large pores also increases and heterogeneity of pore structure decreases. However, water flooding with high IPVR has reverse effects on pore structures. Polymer flooding reduces the total porosity, connected porosity, the percentage of small pores and enhances the heterogeneity of pore structures. It can be found that pore structures will change in fluid flooding and appropriate water injection can improve reservoir quality while excessive water injection may destroy the reservoir. Meanwhile, injected polymer may block throats and destroy reservoirs. The experimental results can be used as the basis for oil field development.

Inter-well interferences and their influencing factors during water flooding in fractured-vuggy carbonate reservoirs

Abstract Based on the characteristics of injection-production units in fractured-vuggy carbonate reservoirs, nine groups of experiments were designed and performed to analyze the interference characteristics and their influencing factors during water flooding. Based on percolation theory, an inversion model for simulating waterflooding interferences was proposed to study the influence laws of different factors on interference characteristics. The results show that well spacing, permeability ratio, cave size, and cave location all affect the interference characteristics of water flooding. When the cave is located in high permeability fractures, or in the small well spacing direction, or close to the producer in an injection-production unit, the effects of water flooding are much better. When the large cave is located in the high-permeability or small well spacing direction, the well in the direction with lower permeability or smaller well spacing will see water breakthrough earlier. When the cave is in the higher permeability direction and the reserves between the water injector and producer differ greatly, the conductivity differences in different injection-production directions are favorable for water flooding. When the injection-production well pattern is constructed or recombined, it's better to make the reserves of caves in different injection-production directions proportional to permeability, and inversely proportional to the well spacing. The well close to the cave should be a producer, and the well far from the cave should be an injector. Different ratios of cave reserves to fracture reserves correspond to different optimal well spacings and optimal permeability ratios. Moreover, both optimal well spacing and optimal permeability ratio increase as the ratio of cave reserves to fracture reserves increases.

Study on start-up of residual oil for different grades of water flooding zones at ultra-high water-cut stage

At present stage, most of the oil reservoirs in China have entered the ultra-high water-cut period, and the heterogeneity is serious. The water flooding effects in different zones of the reservoirs are obviously different. The overall reservoir recovery degree is low, and there is still a large amount of remaining oil remaining in all grades of water flooding zones. This paper mainly carried out the relevant physical model experiment of the remaining oil in the ultra-high water-cut period, and simulated the recovery of the remaining oil under different subsequent flooding conditions after entering the ultra-high water-bath period of different grades of water flooding zones. The start-up law of the remaining oil in the different grades of water flooding zones was observed and analyzed. According to the experimental results, it can be seen that in the period of ultra-high water cut, the strong water flooded zone has a greater exploitation potential than the extreme water washing zone and the weak water flushed zone. Therefore, the focus of developing in the ultra-high water-cut stage should be placed on the strong water flooded zone, and the water flooding after adjusting the profile by injecting jelly can effectively improve the recovery rate of the strong water flooded zone.

Analysis of the Static and Dynamic Imbibition Effect of Surfactants and the Relative Mechanism in Low-Permeability Reservoirs.

Establishing an effective displacement system for conventional water flooding development in low-permeability reservoirs is difficult, with generally low liquid and oil production and a worse water flooding effect. Imbibition oil recovery technology has received increasing attention from oil development workers because of its simple operation, low cost, and good oil increase effect. To explore the method and mechanism to further improve the effect of imbibition oil recovery, we study the imbibition and oil recovery effect and its influencing factors in a low-permeability reservoir in the Dagang Oilfield based on evaluation indexes of the adhesion work reduction factor, ratio of capillary force to gravity NB–1, regression analysis of the recovery rate of imbibition, proportional relationship with spontaneous imbibition, and dynamic imbibition effect in crack rocks. Results show that reducing the interfacial tension of the surfactant on the imbibition process has a dual effect. The selection of the surfactant for fractured tight reservoirs should not excessively pursue ultralow interfacial tension, and it should consider the surface wettability environment favorable for imbibition to ensure that a sufficient driving force can be provided. In the initial imbibition stage, the capillary force is large, the velocity of water imbibition in pores is fast, and the oil recovery rate is high; the holding time of the imbibition process is important to imbibition recovery. With the increase in imbibition time, the capillary force weakens, and the imbibition speed decreases to zero. With the increase in injection volume, reservoir pressure, pressure holding time, and imbibition cycles, the oil recovery increases, but the amplification of oil recovery decreases. From the technical and economic viewpoints, the optimal slug size, throughput cycle, and pressure holding time of the target reservoir are recommended as follows: 0.5 PV,three3 rounds, and greater than 96 h, respectively.

A Novel Oil-Water Two-Phase Flow Numerical Simulation Method In Tight Sandstone Reservoirs

As a crucial factor affecting water flooding in tight sandstone reservoirs, dynamic capillary pressure (DCP) has significant impact on the production performance during oil-water flow. In this work, a novel numerical simulation method with DCP is developed to study oil displacement in tight sandstone reservoirs. Based on this new model, the impacts from DCP to water/oil displacement (or water flooding effects) are analysed. The results of this work show that the effects brought by dynamic capillary pressure cannot be neglected. The more significant dynamic effects of capillary pressure correspond to the sample with lower permeability. The effect of DCP is probably a major contributor to non-linear flow (non-Darcy flow) in tight sandstone reservoirs during water flooding process. Compared with the conventional flow theory (e.g., static capillary pressure theory), our derived model with DCP can help to reduce the uncertainty in water/oil flow in tight sandstone reservoirs.

Application of Well Pattern Adjustment for Offshore Polymer Flooding Oilfield: a Macro-Scale and Micro-Scale Study

The early polymer flooding development technology has been applied to the Bohai Bay oilfield. However, about 50% of the residual crude oil remains in the formation after polymer flooding. The ways to improve the effect of polymer flooding needs to be further investigated. In this paper, we simulated the development effect of well pattern adjustment technology during polymer flooding through laboratory experiments and analyzed the development effect of oil displacement and the distribution of remaining oil from macroscopic and microscopic aspects. The micro-electrode technology was applied to the macro-scale physics experiment to study the development effect and residual oil distribution. In this experiment, nine-spot injection pattern was changed to line-drive pattern during polymer flooding. The micro-scale physics experiment uses nuclear magnetic resonance technology to study the micro-scale distribution of residual oil in the high and low permeability core pores before and after polymer flooding. The experimental results show that in heterogeneous reservoir, the remaining oil is mainly concentrated in the large pores of the medium and low permeability layers at high water cut stage. During the polymer flooding stage, the polymer is squeezed into the large and medium pores of the high-permeability layer and small pores of the low-permeability layer, effectively increasing the sweeping area and displacement efficiency of the low-permeability layer. The residual oil remains mainly in the large pores of the medium and few permeability layers. During the subsequent water flooding stage, the medium permeability layer demonstrates the strongest displacement effect. The increase in yield of the low permeability layer was mainly due to the displacement of oil in the large pores in low permeability layer. After long-term water injection development, the oil recovery of large pores in the low-permeability layer is similar to that in the high-permeability layer. The remaining oil is concentrated in the small pores of the high-permeability layer and the medium and small pores of the low-permeability fiver. The low-permeability layer still has potential for development. Changing the well pattern system is conducted to provide uniform displacement of polymer solution, improving and enhancing the displacement effect of polymer flooding and subsequent water flooding, especially improving the displacement effect in the low permeability layer. In this experiment, the oil recovery of well pattern adjustment was increased by 4.77%. Through experimental research, we believe that polymer flooding with well pattern adjustment can not only expand the flow area by changing the flow field, but also further play the role of polymer profile control. The two mechanisms complement each other, 'effectively improving the unevenness of displacement and enhancing the oil recovery. The experimental results can provide new ideas and technical support for further improving the development effect of polymer flooding in offshore oilfields.

Research and Application of Optimized Integrated Profile Control in Wang 36 Well Area of Wangjiawan Oilfield

Aiming at the problems of serious heterogeneity of reservoirs in Wang 36 well area of Wangjiawan Oilfield, raPId rise of water cut in the oilfield, poor waterflooding development effect and unsatisfactory effects of conventional single profile control measures. Based on PI decision-making, a comprehensive profile-adjustment decision-making technique based on factors such as heterogeneity of water absorption profile and rising rate of water cut is developed. Field application shows that the overall profile adjustment of the block effectively improves the water flooding effect of Wang 36 block. This method has the characteristics of fastness, practicality and strong operability, and has important guiding significance for comprehensive treatment of similar oilfields.

The effectiveness of low salinity waterflooding in naturally fractured reservoirs

Low Salinity (LoSal) waterflooding is a technique which promises to improve and enhance oil recovery. The method has been studied widely in the laboratories using various core plug samples of sandstones and carbonates. Most of the experimental outcomes have demonstrated the possibility of recovery increment in conventional reservoirs. Meanwhile, it is rare to find a discussion in these experiments about the effectiveness of LoSal waterflooding in naturally fractured reservoirs. In this paper, we investigate the potential benefits in fractured reservoirs using simulations.It is often reported from coreflood experiments that LoSal injection has the ability to alter the rock wettability and reduce residual oil saturations through chemical and physical interactions between the rock-oil-water system. Based on the published work, we have calculated relative permeability curves to represent the flow in regions flooded with LoSal water. This includes a qualitative representation of uncertainty. In this sense, the relative permeabilities are a proxy for any physical and chemical mechanisms which are not explicitly represented. The newly generated flow curves were applied to simulate LoSal waterflooding using a fine-scale model and a field scale model based on a fractured reservoir from the Middle East.The simulation results underline the benefits of LoSal whereby the oil recovery from fractured reservoirs can be increased. An additional benefit is the control of water production. The fine-scale modelling has provided an in-depth analysis and accurate estimation of the oil recovery without modelling artefacts or limitations, where an increment of (12–14)% of the Stock Tank Oil Initially In Place (STOIIP) were obtained under secondary and tertiary recovery scheme, respectively. The investigated scenarios demonstrated a sensitivity to the newly generated flow curves and how they affect the ultimate oil recovery. However, for the field scale model, a higher oil production rate has maintained during LoSal waterflooding up to 32 K BPD by the end of year fourteen compared with 25 K BPD in case of high salinity scenario, besides a reduction in the produced water by 35.7%. Therefore, the effectiveness of LoSal brine required a longer time frame to observe the improvements in the oil displacement or sweep efficiency.

Formation mechanism and distribution characteristics of micro residual oil in ultra-high water cut reservoirs a case study of yangsanmu oilfield

The formation mechanism and distribution characteristics of microscopic remaining oil are the basis for efficient development and enhanced oil recovery of heavy oil reservoirs in ultra-high water cut stage. This paper takes Yangsanmu heavy oil reservoir in Huanghua depression as an example, micro-displacement simulation experiment based on microscopic pore structure analysis. Through parallel experiments, the remaining oil displacement effects of water flooding combined with polymer flooding, water flooding and surfactant polymer system combination, water flooding and poly-alkaline ternary composite flooding were compared. The formation mechanism and distribution pattern of remaining oil under different displacement medium conditions were studied to find a reasonable displacement medium system. The experimental results show that the formation of microscopic remaining oil in the study area is related to the stripping effect, the flow around, the pinch action occurs, the run through effect and the adherent flow. The distribution types of remaining oil are mainly angular type, pore wall oil film type, throat retention type, dispersed oil drop type and porphyritic remaining oil in macropores. The analysis of residual oil saturation under different displacement media shows that the combined flooding effect of water flooding and poly-alkaline ternary composite flooding are the best, followed by water flooding and surfactant polymer system combination flooding. This study provides guidance for the remaining oil exploration plan of the ultra-high water cut stage heavy oil reservoir in this area.

Research on New Mining Technology Based on Oilfield Reservoir Water Injection

During the development of oilfields, we usually study reservoir water injection and water injection well fracturing as two important measures to improve the effect of water flooding. These two technologies play a big role in oilfield development, but there are also some problems in the application process. In this paper, through the analysis of the fracturing mechanism and problems of reservoir water injection and water injection wells, the adjustment method of reservoir water injection and water well fracturing is proposed, which reduces the water injection pressure technology of high pressure water injection well and improves the oilfield development effect.

Experimental Investigation on Injection and Production Pattern in Fractured-Vuggy Carbonate Reservoirs

To constitute and adjust the injection and production pattern in fractured-vuggy reservoirs, we extracted twelve fractured-cave structures, fabricated them into physical models with acrylic plates, and performed experiments via these models. The results show that utilizing oil/water gravity segregation sufficiently and forming valid flow channels should be emphasized. Preferentially exploiting the reservoir body containing intermediate-scaled or large-scaled caves, arranging injection wells in fractures or small-scaled caves while placing production wells in large-scaled caves, and separately putting injection wells and production wells in low/high parts of an intermediate-scaled or large-scaled cave, were found to benefit oil/water gravity segregation and thus gain a better water flooding effect in these experiments. Experiments with combined models also figured out that, after adjusting the injection and production pattern, the valid flow channel newly formed must pass through caves containing enough residual oil to improve the water flooding effect and could be obtained by shutting down the old production well while adding a new production well, adding a new production well, or switching the production well into an injection well while adding a new production well. In the actual field, adjusting the well location and altering the flow channel were proposed to conduct together. This study may provide references on the production management of analogous reservoirs.

Crude oil/brine/rock interface in low salinity waterflooding: Experiments, triple-layer surface complexation model, and DLVO theory

The determination of the electrokinetic properties of crude oil/brine and rock/brine interfaces is necessary to understand and evaluate the low salinity waterflooding (LSWF) effect on wettability alteration and enhanced oil recovery (EOR). The interface properties and characteristics of oil and rock minerals significantly affect LSWF and must be elucidated in detail. Herein, the interaction of crude oil, brine, and rock was studied to elucidate the LSWF effect in carbonate and sandstone reservoirs. A triple-layer surface complexation model was proposed to describe the calcite/brine and kaolinite/brine interfaces and was verified with zeta potential experiments at various pH and calcium, magnesium, and sulphate concentrations. Furthermore, the surface complexation model prediction of zeta potential agreed well with the measured data for the suspension in seawater, formation water, and associated dilutions. The predicted surface potential of crude oil, calcite, and kaolinite was used in Derjaguin-Landau-Verwey-Overbeek (DLVO) theory to estimate the total disjoining pressure as attractive/repulsive forces. The interaction between crude oil and calcite/kaolinite on seawater dilution and in the presence of sulphate in the diluted solution for calcite was evaluated via disjoining pressure. Moreover, the importance of electrokinetic properties on attractive/repulsive forces and the mechanisms for wettability alteration in crude oil-brine-kaolinite due to LSWF as well as in oil-brine-calcite because of sulphate addition are discussed.

Study on Injection-Production System Adjustment of Fault Block Reservoir Based on Equilibrium Displacement

This paper proposed a method of injection-production system adjustment to solve the problem that the water flooding effect was restricted because of the horizontal and vertical contradictions during the development process of fault block reservoirs. Considering the heterogeneity of reservoir, the Buckley-Leverett water flooding theory was applied to establish the relationship between the recovery and cumulative water injection. In order to achieve the goal of vertically balanced recovery of each section, the calculation method of vertical sectional injection allocation was proposed. The planar triangular seepage unit was assumed and sweep coefficients of different oil-water distribution patterns were characterized using multi-flow tube method. In order to balance and maximize the plane sweep coefficient, the calculation method of plane production system optimization was obtained. Then the injection-production system stereoscopic adjustment method based on equilibrium displacement was proposed with vertical sectional injection allocation and plane production system optimization. This method was applied to injection and production adjustment of BZ oilfield in southern Bohai. The effect of water control and oil increase was obvious. This method can greatly improve the effect of water flooding of offshore fault block reservoirs with the adjustment of injection-production system.

3D Physical Simulation of Water Flooding Characteristics of Buried Hill Reservoir with Different Fracture Systems

In order to understand the water-flooding characteristics of different fracture systems in metamorphic rock buried hill reservoirs and the mechanism of improving water-flooding development effect, a three-dimensional physical model of fractured reservoirs is established according to the similarity criterion based on the prototype of metamorphic buried hill reservoirs in JZ Oilfield in Bohai Bay Basin. Combined with the fractured reservoir characteristics of JZ Oilfield, the water displacement characteristics of the top-bottom staggered injection-production well pattern in different fracture network mode and different fracture development degree of buried hill reservoir are studied. The experimental results show that: 1) the more serious the fracture system irregularity is, the shorter the water-free oil production period is and the lower the water-free oil recovery is. After water breakthrough of production wells, the water cut rises faster, and the effect of water flooding development is worse; 2) under the condition of non-uniform fracture development, the development effect of the bottom fracture undeveloped is better than that of the middle fracture undeveloped. Water injection wells are deployed in areas with relatively few fractures, while oil wells are deployed in fractured areas with higher oil recovery and better development effect.

Nuclear Magnetic Resonance Evaluation Study for Effect of Foam flooding in Heterogeneous Cores

Foam flooding demonstrated the ability to solve the viscous fingering problem of gas flooding and increase the sweep efficiency in enhancing oil recovery. It is commonly used in development of heterogeneous reservoirs. While the characteristics of fluid migration in pores and between layers were still unclear. In this paper, Dynamic change of oil and water with different foam quality was tested during foam flooding by NMR method. Oil displacement effect of water flooding and foam flooding was compared. The results showed the foam quality affected the foam stability and profile control effect. Compared with water flooding, the foam could increase the recovery rate of the low-permeability layer, and the foam system with high stability had a high sweep efficiency and a high oil displacement efficiency in the heterogeneous cores.