Water Flooding Conditions Research Articles

The egg model – a geological ensemble for reservoir simulation

The ‘Egg Model’ is a synthetic reservoir model consisting of an ensemble of 101 relatively small three‐dimensional realizations of a channelized oil reservoir produced under water flooding conditions with eight water injectors and four oil producers. It has been used in numerous publications to demonstrate a variety of aspects related to computer‐assisted flooding optimization and history matching. Unfortunately the details of the parameter settings are not always identical and not always fully documented in several of these publications. We present a ‘standard version’ of the Egg Model which is meant to serve as a test case in future publications, and a dataset of 100 permeability realizations in addition to the permeability field used for the standard model. We implemented and tested the model in four reservoir simulators: Dynamo/Mores (Shell), Eclipse (Schlumberger), AD‐GPRS (Stanford University) and MRST (Sintef), which produced near‐identical output. This article describes the input parameters of the standard model. Together with the input files for the various simulators, it has been be uploaded in the 3TU.Datacentrum repository with free access to external users.

Effect of crossflow on upgridding geological model under water flooding scenario

Abstract The main purpose of upgridding is to reduce the number of grid blocks present in the geological model while preserving the dynamic behavior observed in the geological model. Since the main goal is to preserve the dynamic behavior, the reservoir parameters, which have an impact on dynamic behavior, should be properly calibrated before upgridding. This includes the type of flow process that is under consideration as well as crossflow across the geological layers. In this paper, we examined the effect of mobility ratio in the presence and absence of crossflow under water flooding conditions. We observed that in the case of favorable mobility ratio and crossflow condition, the upgridding error (difference between fine and coarse layer models production) is small and many more layers could be combined without deviating from the fine-scale model result. In contrast, for unfavorable mobility ratio displacements, crossflow does not help homogenize heterogeneous layers. The upgridding error increases very rapidly as the layers are combined. This implies that we need to maintain a much higher level of detail from the fine-scale model if we want to retain the dynamic behavior.

New understanding on water-oil displacement efficiency in a high water-cut stage

Based on analyzing dominant internal and external factors affecting water-oil displacement efficiency, the variation of oil displacement efficiency is studied by means of experimental and theoretical analyses. Internal factors include reservoir heterogeneity (highlighted micro-pore structure heterogeneity) and wettability. External factors are waterflooding conditions, including pore volume (PV) of water injected, injection rate, and oil-water viscosity ratio. The variation mechanism is analyzed based on the definition, laboratory determination and field application of oil displacement efficiency. A viewpoint is proposed that the changes of wettability and pore structure in a high water-cut stage would reduce the critical capillary number and the residual oil saturation, leading to improvement of water displacement efficiency. More attention should be paid to water-oil displacement efficiency when water-flooding oilfield enters a high water-cut stage. Research on water-oil displacement efficiency must be deepened from three levels as follows: the first is the definition of laboratory values, the second is to study economic and effective conditions for getting (reaching) a certain oil displacement efficiency, the third is how to develop cost-effective techniques to improve the displacement efficiency by increasing capillary number.

Petroleum exploration and development practices of sedimentary basins in China and research progress of sedimentology

Based on the characteristics of recent discoveries in China, continental clastic reservoirs are the most important area for reserves and production growth. Significant progress has been made in exploration of carbonates reservoirs, for example, platform-margin reef complexes and platform interior reefs and banks. Volcanic reservoir exploration in sedimentary basins is feasible now. Mature oilfields with high water cut are predominant in the oil production in China. Some technological problems facing the stable production of mature oilfields have been solved by fine characterization of reservoirs, improving water flooding conditions, and EOR techniques. CNPC makes progress on studies of the sedimentary pattern of continental lacustrine basin shallow water delta, the origin and distribution of sandy debris flow, the mechanism and distribution prediction of deep favorable reservoirs, the sedimentary facies evaluation and reservoir prediction of low-porosity and low-permeability conglomerates, the lithofacies palaeogeography reconstruction of marine carbonates, the fine characterization of carbonates platform margins, the mechanism of carbonate reservoir superposition and rework, the origin classification of karst reservoirs, unconventional reservoir evaluation, reservoir improvement techniques, etc. These provide important theoretical and technical support for the exploration and development of oil and gas. 从近期中国油气发现的特点看，陆相碎屑岩仍是中国石油增储上产最主要的领域，碳酸盐岩勘探正处于大发现期，台缘礁滩复合体与台内礁、滩勘探成果显著，沉积盆地中火山岩储集层已成为油气勘探的现实领域。高含水老油田是中国油田开发的主体，持续的储集层精细表征研究和改善水驱条件、提高采收率技术攻关，突破了高含水老油田的稳产技术瓶颈。中国石油天然气集团公司在陆相湖盆浅水三角洲沉积模式建立、砂质碎屑流成因与分布、深部有利储集层发育机理与分布预测、低孔渗砂砾岩储集层成岩相评价与有利储集层预测，海相碳酸盐岩岩相古地理重建、碳酸盐岩台地边缘精细刻画与台地内部结构细化、碳酸盐岩储集层多期叠加改造机理、岩溶储集层成因分类，非常规储集层评价、开发储集层沉积学、沉积储集层研究新技术与新方法、储集层改造技术等领域不断取得新的进展，为今后油气勘探开发提供了重要的理论和技术支撑。图6表2参62

Effect of Arbuscular Mycorrhizal Fungi on Tree Growth and Nutrient Uptake of Sclerocarya birrea under Water Stress, Salt Stress and Flooding

A greenhouse experiment was conducted to determine the influence of arbuscular mycorrhizal (AM) fungus inoculation on water stress, salt stress and flooding tolerance of three subspecies of Scleocarya birrea (A. Rich.) Hochst. Gigaspora margarita Baker and Hall was used for the inoculation. All the three subspecies of S. birrea had high tolerance both to water stress and flooding even without G. margarita inoculation. All flooded seedlings developed lenticels and survived three months of flooding. Non-mycorrhizal seedlings of S. birrea subsp. multifoliolata survived even under electric conductivity of up to 7.1 dS·m−1. Root colonization by G. margarita markedly improved tolerance of S. birrea seedlings to water stress, salt stress and flooding. In particular, S. birrea subsp. caffra under water stress and flooding conditions showed the highest response to inoculation. Mycorrhizal S. birrea subsp. multifoliolata recorded enhanced uptake of N, P, Ca and Mg at 7.1 dS·m−1. These results demonstrate that even though S. birrea has natural tolerance to water stress, salt stress and flooding, AM fungus is very effective in strengthening the tolerance of S. birrea grown in arid and semi arid areas.

A mitigation strategy for the natural disaster of poverty in Bangladesh

PurposeAims to bring attention to the problems faced by rural Bangladeshis. Several objectives for the paper were identified. First, to illustrate that Bangladeshis suffer from acute levels of poverty, a lack of clean drinking water and regular flooding and cyclonic conditions. Second, to establish the failure of western “handout” aid provision to address these problems. Third, to evidence the possibilities for the production of more durable building materials utilising regionally available waste materials and proven solar technologies. Finally, to present strategies in which solar technologies could contribute to the reduction of poverty and improvements in health standards.Design/methodology/approachThe ongoing development and testing of the innovative solar technology concepts reported in the paper were informed by a literature review covering solar cookers and solar kilns. The methodology and detail of the testing of that solar technology is currently considered commercially sensitive. With regard to the poverty alleviation strategies proposed within the paper, their development was underpinned by a methodology combining a thorough review of the relevant literature with input from practitioners in Bangladesh.FindingsUtilising aid moneys for the establishment of solar technology‐based small‐scale production of vernacular building materials could address poverty by affording access to wealth‐generating activities in the sale of goods and clean drinking water from rainwater harvesting. Additionally, such activities would enable Bangladeshi society to be better able to withstand and then recover from natural disasters, by possessing more resistant shelters, and being more economically resilient.Research limitations/implicationsThe experimental component of the research is ongoing and considered commercially sensitive. No limitations have thus far been identified within this component. The implications of the research regarding solar technologies are potentially considerable in that the innovative approach under examination, if underpinned by positive results, represents a new area of activity and has both social and technical implications.Practical implicationsCurrent aid is not significantly alleviating the problems experienced by Bangladeshis resulting from poverty, arsenic contamination of deep water aquifers and regular flooding. The technology and strategies proposed address the fact that the current vernacular shelters provide little resistance to flooding, and are unsuitable for rainwater harvesting, whilst also allowing participation in wealth‐generating activities. Such a combination has the potential to reverse the trend for Bangladesh to increasingly rely on “hand‐out” aid.Originality/valueThe value of the paper is largely in the area of bringing new possibilities to the attention of the research and practitioner communities dealing with both solar technologies and developing world poverty alleviation.

Analysis and Interpretation of Water/Oil Ratio in Waterfloods

SummaryAn important problem in water control is the identification of the dominant reservoir or production mechanisms. Recently, Chan (Chan, K.S.: "Water Control Diagnostic Plots," paper SPE 30775 presented at the 1995 SPE Annual Technical Conference and Exhibition, Dallas, 22–25 October) postulated that a log-log plot of the water/oil ratio (WOR) produced vs. production time may be used to diagnose these factors. In this paper we provide analytical and numerical results for a variety of waterflood conditions to explore this possibility.We show analytically that the late-time slope of the log-log plot can be related to the well pattern and the relative permeability characteristics, specifically the power-law exponent in the kro − Sw relationship or the reservoir heterogeneity. Analytical results are provided for the behavior immediately following water breakthrough. In certain simple cases (mobility ratio equal to 1, layered systems), analytical type curves can be derived. In the general case, we use numerical simulation to provide numerical type curves.The results are summarized in terms of the various power-law scalings in different time regimes and by a catalog of numerical type curves. They confirm the potential of WOR-time plots as diagnostic tools for reservoir analysis and characterization.

Effects of Capillary Pressure and Use of Polymer Solutions on Dense, Non-Aqueous-Phase Liquid Retention and Mobilization in a Rough-Walled Fracture

In this laboratory study, perchloroethylene (PCE) was permitted to migrate through a horizontal rough-walled limestone fracture under controlled conditions to assess fracture retention capacity. Retention of immiscible-phase PCE in the absence of an applied wetting-phase hydraulic gradient varied between 11% and 26% of the fracture volume. A portion of this residual could be removed through water flooding; however, even at the maximum applied hydraulic gradient of 1.0, residual PCE remained in the fracture. The observed correlation of reduced residual saturation with capillary number (NC) demonstrated that this rough-walled fracture exhibited behavior similar to that of a porous medium under water-flooding conditions. For a given hydraulic gradient, polymer-enhanced floods (using xanthan gum) were not as successful as conventional water flooding at removing residual from the fracture. The traditional form of the capillary number became an increasingly poor predictor of mobilization behavior as the viscosity of the displacing phase was increased. Incorporation of (μW/μNW)-0.5 into the traditional capillary number provided a more appropriate dimensionless group with which to correlate residual PCE saturation in the fracture as μW increased.

The Importance of Interfacial Tension on Fluid Distribution During Depressurization

Summary Many North Sea reservoirs produce water at very high cuts under current waterflooding conditions. As oil production drops below economical limits, procedures for recovering residual and bypassed oil are being investigated. One technique identified as potentially suitable for at least ten candidate fields in the United Kingdom Continental Shelf (UKCS) is to depressurize these fields. During pressure depletion, improved hydrocarbon recovery has been shown to result from the release of solution gas and subsequent expansion of the freed gas. The precise nature of gas nucleation and its subsequent growth phenomena, however, have not been well understood. For example, there exists experimental evidence supporting two apparently conflicting models describing gas nucleation. High pressure micromodel studies have shed light on the physical processes occurring at the pore scale during pressure depletion in waterflooded systems. Specifically, tests performed with fluids characterized by different gas/oil interfacial tensions (IFT's) have shown the important role gas/oil and gas/water IFT's play during bubble formation and growth in porous media. Analysis of visual information from water-wet micromodel tests have shown that the magnitude of the liquid-gas IFT is one of the factors that determines in which phase the bubbles nucleate, and how many bubbles form per unit volume of pore space. A low gas/oil IFT results in a relatively large number of bubbles forming in the oil phase only, with little or no supersaturation. Higher values of gas/oil IFT result in increasing levels of supersaturation with relatively fewer bubbles nucleating at cavity sites on the water-solid interface. Not only is the gas/oil IFT at the bubblepoint important in determining the nucleation loci and densities, but the increasing gas/oil IFT values with decreasing pressure also affect the distribution of the three phases during the process. Increasing gas/oil IFT's, combined with the effect of disjoining pressure in thin water films separating oil ganglia, result in delayed oil production and expulsion of water from the system below a certain threshold pressure. This suggests that there is an identifiable minimum pressure below which hydrocarbon production will not be viable.

Decline Curve Analysis For Canadian Oil Reservoirs Under Waterflood Conditions

Abstract Decline curve analysis using type-curve matching has become an established engineering tool to evaluate long-term production characteristics of oil and gas reservoirs producing under various drive mechanisms. Decline curve analysis is often used to satisfy various regulatory requirements, to establish reserves, and to evaluate the success or failure of operational changes made during a reservoir's producing life. In this study, a detailed investigation of production decline data from 78 Western Canadian Sedimentary Basin oil pools under waterflood conditions is presented. This study demonstrates that the majority of the waterflooded oil pools follow a hyperbolic decline with decline curve exponents ("b") less than 0.5. The decline exponent "b" does not exhibit any obvious functional relationship to the type of rock, oil density, geographical area, and/or geological formation. Nonetheless, such a study provides a basis for "b" values to be expected for Canadian oil reservoirs under waterflood conditions. Introduction Decline curve analysis is one of the oldest and most extensively used methods of predicting the future performance of a producing well, a lease, or a depleting reservoir. The purpose of this study is to present an analysis of the production declines of a group of waterflooded oil pools in Western Canada to establish any obvious decline trend. All of the pools selected are located in the Western Canadian Sedimentary Basin, which covers northeastern British Columbia, the southern half of Saskatchewan, and most of Alberta. This study uses a type-curve matching technique(1) based on the general hyperbolic decline equation: Equation 1 (available in full paper) Previous Studies Fetkovich(2) reported that in a predominantly solution-gas-drive reservoir in Texas, both the primary decline and the waterflood decline appeared to have the same decline exponent "b" of 0.3. Reasons for this phenomenon were uncertain to him. Schuldt et a l .(3), indicated that waterflooded oil reservoirs are generally expected to follow hyperbolic decline behaviour, but they neither explained why this should be so nor indicated their source of information. Mead(4) wrote that pools under different producing mechanisms, waterflood or water influx, should follow exponential or hyperbolic decline with decline exponents in the range of 0 to 0.2. Lijek(5) showed that if a plot of log (WOR) versus cumulative oil produced is linear, the decline curve of the pool is either hyperbolic or harmonic, depending on whether the gross rate is constant or variable. From his experience, he concluded that the decline exponent is very close to one (that is, harmonic decline) at a constant gross rate. Currier and Sindelar's work(6) was similar to that of Lijek(5). They used log (WOR) versus cumulative oil recovery and a frontal advance cross-plot to aid them in establishing waterflood production decline trends from early data of a waterflood field in Alaska. Their study also showed that waterflood declines are harmonic or hyperbolic with a decline exponent much higher than those presented by Mead(4). In their study, cases with a straight line log (WOR) versus cumulative oil produced yielded decline exponents between 0.6 and 0.7.

96/04293 29Si-NMR study of the absorbent for flue gas desulphurization

Based on the characteristics of recent discoveries in China, continental clastic reservoirs are the most important area for reserves and production growth. Significant progress has been made in exploration of carbonates reservoirs, for example, platform-margin reef complexes and platform interior reefs and banks. Volcanic reservoir exploration in sedimentary basins is feasible now. Mature oilfields with high water cut are predominant in the oil production in China. Some technological problems facing the stable production of mature oilfields have been solved by fine characterization of reservoirs, improving water flooding conditions, and EOR techniques. CNPC makes progress on studies of the sedimentary pattern of continental lacustrine basin shallow water delta, the origin and distribution of sandy debris flow, the mechanism and distribution prediction of deep favorable reservoirs, the sedimentary facies evaluation and reservoir prediction of low-porosity and low-permeability conglomerates, the lithofacies palaeogeography reconstruction of marine carbonates, the fine characterization of carbonates platform margins, the mechanism of carbonate reservoir superposition and rework, the origin classification of karst reservoirs, unconventional reservoir evaluation, reservoir improvement techniques, etc. These provide important theoretical and technical support for the exploration and development of oil and gas.从近期中国油气发现的特点看，陆相碎屑岩仍是中国石油增储上产最主要的领域，碳酸盐岩勘探正处于大发现期，台缘礁滩复合体与台内礁、滩勘探成果显著，沉积盆地中火山岩储集层已成为油气勘探的现实领域。高含水老油田是中国油田开发的主体，持续的储集层精细表征研究和改善水驱条件、提高采收率技术攻关，突破了高含水老油田的稳产技术瓶颈。中国石油天然气集团公司在陆相湖盆浅水三角洲沉积模式建立、砂质碎屑流成因与分布、深部有利储集层发育机理与分布预测、低孔渗砂砾岩储集层成岩相评价与有利储集层预测，海相碳酸盐岩岩相古地理重建、碳酸盐岩台地边缘精细刻画与台地内部结构细化、碳酸盐岩储集层多期叠加改造机理、岩溶储集层成因分类，非常规储集层评价、开发储集层沉积学、沉积储集层研究新技术与新方法、储集层改造技术等领域不断取得新的进展，为今后油气勘探开发提供了重要的理论和技术支撑。图6表2参62

Role of Capillary Forces In Detennining Microscopic Displacement Efficiency For Oil Recovery By Waterflooding

Abstract The factors controlling the distribution of two immiscible fluids, such as oil and water, within the interstices of a porous solid are reviewed. It is shown that an improved understanding of these factors forms the basis of much recent work aimed at the development of new methods for reducing capillary forces and, consequently, eliminating residual oil saturations. Introduction THE PETROLEUM INDUSTRY has for many years devoted much research effort to the development of new processes for achieving improved oil recovery efficiencies. The current status of the most promising of these new processes has been reviewed by Elkins(l) and by Arnold(2). For the most part, the research leading to these processes has developed along lines pointed out by Muskat(3) in a review published about 20 years ago. In addition to thermal processes, which are used primarily to overcome adverse crude oil viscosity characteristics, a variety of processes are designed to eliminate or reduce the so-called "surface forces" within the crude-oil-displacing fluid-reservoir rock system. When displacement is carried out by flooding with an immiscible fluid such as water or gas, the surface forces (or. more accurately, the capillary forces) are responsible for trapping a large portion of the oil phase within the interstices or pores of the rock. For typical, homogeneous sandstone rocks, under usual waterflooding conditions, trapping will occur within an appreciable fraction of the total number of pores constituting the pore space of the rock. The fraction of the pore volume which is involved may range from 10 to 50 per cent. Thus, capillary forces play a major role in limiting the recovery efficiency of such displacement processes. Capillary forces will clearly be eliminated if the drive fluid is preceded by a slug or bank of fluid which is miscible both with the reservoir oil and with the displacing phase(4). However, the costs of the solvent materials required in processes based on this principle may be prohibitive. Alternatively, water-soluble surfactants, such as petroleum sulphonates, can be employed to eliminate the tendency of the oil phase to remain trapped in the pores of the rock. Details of several processes based on the use of such surfactants have been recently reported(5–9). In this paper, the nature of the surface or capillary forces encountered in petroleum reservoirs, together with the microscopic features of the associated trapping mechanism, will first be reviewed. Some features of a new recovery process based on the use of surfactants, i.e., the low-tension waterflooding process (7–9), will then be described. This discussion will emphasize one of the principal microscopic mechanisms on which the process is based. An analysis of this mechanism indicates that ultra-low values of the oil-water interfacial tension are required in order to achieve improved recovery. Hydrostatics, Capillarity and Residual Saturations HYDROSTATIC PRINCIPLES IN MULTIPHASE FLUID SYSTEMS Two or more fluid phases confined within a porous solid phase of very small average pore size wilt generally be microscopically commingled. The fluid-fluid interfacial areas associated with fluid distributions of this type are large and characterized by high curvatures.

Economic aspects of using electric power for waterflooding

A specific oil field is selected to illustrate the comparison of electric power costs and those of gas engine operation in another field under similar waterflood conditions. The study indicates that electric power costs have been one half the cost of fuel for gas engine operation for equal volumes of fluid pumped, while manpower requirements were reduced 20 per cent due to electrification of six out of eight waterflood projects.

Water Input Profile Determinations on Injection Wells in Secondary Recovery Fields

Abstract The knowledge of the distribution of input water in injection wells is important to the success of water flood secondary recovery projects. The presence of thief formations, the lack of complete well history, and improper completion methods all contribute to diverting the flood water from the producing horizon. Through the use of known tools and procedures, input profiles can be obtained. The interface velocity procedure coupled with caliper and correlation logs give satisfactory input profiles. These provide the data to detect the presence of the undesirable conditions and for the method of correction. Under normal conditions the correlations between profile data and permeability data from cores is good. Introduction The application of secondary recovery methods to oil production has spread rapidly throughout the oil fields of the United States. This has created a desire for greater knowledge of the behavior of the oil reservoir under a secondary recovery program. In the case of water flooding projects and particularly during the early stages of pilot flood work, it is important to know the water is being directed through the proper zone. In a recent paper on secondary recovery water flood projects which had been classified as unsuccessful, it was shown that a considerably larger quantity of water had been injected than fluid recovered. This indicated that the flood water was going into zones which were not part of the oil reservoir. Confirmation of this was not established since no attempt had been made to determine the distribution of the input water into the zone being flooded. The need for this type of information on many water flood projects has caused the secondary engineers to seek means of obtaining this data in an effort to better understand and evaluate their various floods. This would require a procedure which would work satisfactorily on wells completed either through perforations, open hole, or shot hole under the following water flooding conditions, namely:Surface injection of flood waters under pressure;Surface injection of flood waters at atmospheric pressure;Dump flood wells using water for flooding from a zone above the oil reservoir. In addition, any tool involved would have to be small enough to work through 2-in. tubing, since a large number of injection wells have tubing in them. In some cases it is not desirable and in others it is not possible to remove it.

Surface Indicating Pressure, Temperature and Flow Equipment

Abstract A surface indicating pressure, temperature and flow instrument that employsvariable frequency sensing elements has proved useful in evaluating flowcharacteristics of wells. Relative productivity of individual oil and gas sandsin a given well can be analyzed at several back pressures. The variable frequency sensing elements are an improvement in sensitivityand accuracy and make possible observation of temperature and pressurevariations that have not been possible heretofore. The surface indicatingfeature results in a more direct approach to solving problems and eliminatesmany assumptions. All three subsurface factors are evaluated, and correlation between themresults in a direct means of analyzing reservoir and well conditions. Surveys have been used to evaluate well performance, locate gas entry inhigh ratio wells and to investigate gas injection and water floodingconditions. Introduction In a flowing well that is open to a multiple number of producing sands withvarying characteristics, it is valuable to know which sands are producing fluidat a given back pressure and in what relative quantity. Core studies couldqualify an interval as productive, and reserves would be computed on thisbasis. Unless the well is produced so that the interval does contribute, irreparable damage to the interval can occur. It is generally accepted that theoptimum condition of production of oil in an oil well will be, if the objectiveis to produce the largest amount of oil at the least cost, to produce oil atsuch rates of flow that the decline of production and the intrusion of edgewater should be uniform as between all portions of the producing horizonsproducing into the well. An indirect approach to this problem does not alwaysresult in a timely practical answer. To insure a correct answer, the conditionshould be measured as directly as possible, while the well is being produced.The PTF equipment was developed with this objective. Measurements of allvariable factors that can be associated with fluid movement, to a high degreeof dependability and accuracy, was a design requirement. Initial field use has indicated that sufficient data can be obtained withthe instrument to answer the questioned conditions in a reasonable length oftime and at a reasonable cost. A description of the instrument, the principals of operation, and the fieldexperience are discussed herein. T.P. 3080