Ultra-high Water Cut Research Articles

The research on the classification method of high water-cut well group in Y block

Y block has entered the ultra-high water cut stage of production, and the water cut of oil wells is generally higher than 90%. Before polymer flooding, water cut continues to rise. High-water-bearing wells in the injected area are characterized by difficulty in effectiveness and low water cut decline, which seriously affects the overall development effect of the area. In this paper, the high water-bearing wells are divided into four categories by the parameter index of the number of layers in the high water-bearing channels before polymer flooding.Through the splitstream curve and the phase permeability curve, the permeability and oil saturation data under the condition of 98% water content were selected for fitting, and the critical oil saturation formula was obtained.The ratio between the oil saturation and the critical oil saturation is calculated by numerical simulation, and the discriminant standard of the dominant seepage channel with high water content is established.Compared with previous remaining oil saturation field identification methods, changed the method according to the conventional ideas of remaining oil saturation evaluation of water and residual oil, through the analysis of reservoir permeability parameters for the current development under the condition of the target reservoir quantitative identification of the cause of high water cut, to cause high containing water wells and reservoir high water cut oilfield management work provide quantitative analysis and objective guidance.

Practice and Understanding of Fine Control Fracturing Technology for Three Types of Sandstone Reservoirs

Development Zone B of Daqing Oilfield is located in the northwest of the oilfield structure and at the western end of the anticline structure in the north. The structure is relatively gentle. It belongs to sandstone reservoirs deposited by typical continental fluvial-delta facies reservoirs. There are many faults in this area, with a large fault distance. A total of 29 large and small faults are developed, all of which are normal faults. The faults have good sealing performance. The sand bodies in this area are cut into narrow strips by faults, with a small distribution area, and the phenomenon of one injection and one production or with and without injection is serious. The contradictions among and within the three types of reservoirs are prominent, and the degree of reservoir production is low. In order to study the high-efficiency tapping potential technology for the three types of reservoirs in pure oil region, technical research and experiments were carried out from 2017 to 2018. Through in-depth analysis of the main factors that affect the development effect of the three types of reservoirs in pure oil region, the technical research route with fine subdivision and large penetration ratio fracture sand control body to improve interlayer and plane contradictions as the research direction was determined, which is aimed at the difference of reservoir sand body development characteristics and injection-production connectivity in each direction, fine subdivision was carried out on the target layer in the longitudinal direction, and the reservoir sand body characteristics and injection-production relationship were combined in the plane. Fine control fracturing technology has been tried in three types of reservoirs, and initial results have been achieved. The fine control fracturing technology has been applied to two wells, with a fracturing efficiency of 100%, increasing oil production by 8.6t at the initial stage of a single well and 2186.3t at the stage. Field tests show that the fine control fracturing technology has a remarkable effect on the reconstruction and production of thin and poor reservoirs, and explores a new way to tap the potential of thin and poor reservoirs in the later period of ultra-high water cut.

Research on Deep Profile Control Technology of Water Flooding in Lamadian Oilfield

After Daqing Lamadian Oilfield entered the stage of development of ultra-high water cut, the ineffective circulation of various oil layers was serious, which restricted the development benefit of oilfields. To this end, the research on deep profile control of water flooding is carried out, and the combination of polymer microsphere flexible diverting agent and bulk expanded particle slug is used to exert a slower blocking speed of polymer microspheres, and a certain resistance is established in the deep pores of the reservoir. To provide the main slug with aggregating residence time; to exert the superior advantage of flexible steering agent deformation and adhesion ability, to form a dynamic path-distributing mechanism in the deep cavity of the reservoir; to play the advantage of faster blocking speed of the bulk-expanding particles, to prevent the main section The plug was flushed by subsequent water injection. Through the multi-segment combination indoor core experiment, it is shown that the front section is filled with microspheres, the main section is filled with flexible agent, and the post-segment is filled with expanded particles, which can well block the invalid circulation part, improve the displacement effect and improve The recovery rate can reach 3.12 percentage points. On October 16, 2013, Daqing Lamadian Oilfield carried out a deep liquid flow steering test study on the 9-injection and 16-hole water-flooding group. The comprehensive water content of the affected oil wells decreased by 7.8 percentage points, and the cumulative oil increase was 5,435 tons. The rate is 2.7 percentage points, and the input-output ratio is 1:4.0, which has achieved better mine results.

Auto-optimization of production-injection rate for reservoirs with strong natural aquifer at ultra-high water cut stage

Abstract Based on the optimal control theory and taking the production law of reservoirs with strong natural aquifer as the basic constraint, a mathematical model of liquid production for such reservoirs in the later stage of development is established. The model is solved by improved simultaneous perturbation stochastic approximation algorithm (SPSA), and an automatic optimization software for liquid production is developed. This model avoids the disadvantage of traditional optimization methods that only focus on the maximum value of mathematics but ignore the production law of oilfield. It has the advantages of high efficiency of calculation, short period and automatic optimization. It can satisfy the automatic optimization of liquid production in later stage of oilfield development. The software was applied in the oilfield development of D oilfield, Ecuador in South America, and realized the automatic optimization of liquid production in the later stage of oilfield development.

Study on Development Law and Yield Replacement Method in Sazhong Development Area

with the increasing time of water drive development in the Sazhong development zone, the oilfield has gradually entered the stage of high water cut stage or ultra-high water cut stage, and now it has entered the development stage of the high water cut period of the coexistence of the two drive. In order to extend the production life of the oilfield and plan the scale of production, based on the application of reservoir engineering method to calculate the natural decline rate and by grouping the Sa Pu oil layer and the Gaotaizi oil reservoir in the Sazhong oilfield, reducing the yield base of each year and re prediction of water drive production decline rule in Sazhong development area, which is concluded that the average decline rate is 7.46%. At the same time, the characteristics of tertiary oil recovery are analyzed, and the production replacement equation is established through the production demand under different production decline conditions. Based on the law of decreasing water drive and the change rule of chemical flooding production, the average chemical drive reserves in 12th Five-Year and the annual largest chemical drive reserves as tertiary oil recovery reserves, and the output forecast index of the sash development zone can be obtained.

Study on deep profile control technology and field evaluation of water flooding thick layer in Lamadian Oilfield

Nine wells are on deep profile control in SaIII1-7 layer of Lamadian Oilfield North West block. Flexible diverting agent are be used to carry out high-dose and long slug deep profile control. Injection profile of injection wells are improved, the radius of plugging is expanded and the plugging efficiency is improved. It has certain adaptability to the profile control of thick layers, and can improve the condition of reservoirs absorption. It can reserve technology for large scale deep profile control on water flooding, and create a new way for high efficiency development the ultra-high water cut oilfield.

The Residual Potential of Bottom Water Reservoir Based upon Genetic Algorithm for the Relative Permeability Inversion

At present in the offshore oilfield, X oilfield had successfully developed bottom water reservoir with horizontal well. The development mode of single sand body of horizontal well caused water cut rose rapidly and irresistible bottom water coning. The common empirical formula of recoverable reserves obtained through statistical analysis was not applicable to the bottom water reservoir. Under the condition of as high as tens of thousands of time local scour multiple, underground seepage law had been changed. In order to improve the understanding of the remaining potential of bottom water reservoir in the ultra-high water cut stage, this research innovation proposed to carry out the flow tube simulation of the bottom water ridge. In addition, combining with the theoretical research of the quantitative characterization of the water ridge form and the vector permeability, theoretical model was established. At last, the phase permeability curve was calculated from the production data of the ultra-high water cut stage of the bottom water reservoir by combining the genetic algorithm. According to the change of water ridge and oil saturation, the mechanism of end point change of phase permeability curve was expounded, and the effective production radius of water drive oil in bottom water reservoir was put forward, which provided the basis for understanding the potential of oil field and tapping the potential in the future.

Study on Optimization of Combined Parameters of Subdivision Water Injection Layer Sections in Ultra-high Water Cut Stage

After 50 years of exploitation, Block A has entered the development stage of the ultra-high water cut stage. Although the layer series of development has been subdivided and adjusted, the interlayer interference is still serious, imposing difficulties in development adjustment. Based on dynamic production data and monitoring data analysis, this paper applies multi-disciplinary reservoir description technology and introduces economic evaluation indicators to quantitatively analyze the variation coefficient of permeability within subdivided layer sections, the number of monolayer breakthrough series and sections, the number of small layers within a layer section, and the effect of sandstone thickness on the subdivision and adjustment effect, analyze the influence of well test period and operation costs on the economic benefits, and the optimize combined parameters of subdivision water injection layer sections. After field application, the utilization proportion of sandstone in the soil layer with the subdivided well permeability of less than 0.1 μ m2 increased by 18.3 percentage points, and the average daily oil output per well in the surrounding wells increased by 0.3 t, effectively reducing the decline in output and increase in the water cut, and providing technical support for water flood fine potential tapping in the ultra-high water cut stage.

New water drive characteristic curves at ultra-high water cut stage

Abstract A function expression of the oil-water relative permeability ratio with normalized water saturation at high water saturation was proposed based on statistics of measured oil-water relative permeability data in oilfields. This expression fits the later section of conventional relative permeability ratio curve more accurately. Two new water drive characteristic curves at the ultra-high water cut stage (fw>90%) were derived by combining the new oil-water relative permeability ratio expression and reservoir engineering method. Then, the numerical simulation results of five-point well pattern and production data of Yangerzhuang Oilfield and Liuzan Oilfield were used to verify the adaptability of the new water drive characteristic curves. The results showed that the new water drive characteristic curves are more accurate than conventional water drive characteristic curves after A type and B type water drive curves rise, and can be used to predict production performance at ultra-high water cut stage, ultimate recovery efficiency and recoverable reserves.

SISP to Enhance Oil Recovery at Ultra-high Water Cut Stage

This paper studied force condition of oil droplets in porous media and mechanism of separated-zone water injection and separated-zone oil production (SISP), considering the action of buoyancy on oil droplets during different stages of oilfield development. New idea SISP to enhance oil recovery is that different layers produce in different pressures by controlling fluid production and improving bottom pressure at ultra-high water cut stage. Three different vertical permeability model was designed and each with following five programs. The results show that the greater vertical permeability is, the bigger incremental recovery factor is. SISP is better than co-injection and co-production.

Numerical Simulation of N2 Foam Flooding in Medium-Permeability Light-Oil Reservoir with Ultra-High Water Cut

This paper is the first attempt to simulate the mechanism of N2 foam flooding in an ultra-high water cut reservoir using the CMG-STARS reservoir simulator with a non-isothermal module. The simulation results showed that N2 foam flooding had the potential to improve oil recovery in a reservoir with high water cut up to 97.6%. The best strategy was simultaneous injection of N2 and foaming agent of 0.3-0.4 wt. % concentration at a gas—liquid ratio of 2-2.5 and total porosity volume (PV) of 0.3-0.35. Under these conditions, the recovery was expected to increase by 1.2%. The experimental results indicated that oil recovery could be enhanced by N2 foam flooding in a medium-permeability light-oil reservoir with an ultra-high water cut.

特高含水期剩余油受力状态方程及敏感分析

特高含水期剩余油受力状态方程及敏感分析

A new water drive curve at ultra-high water cut stage and application in prediction of oilfield development

For the water-flooded reservoir at ultra-high water cut stage, the ratio of oil and water relative permeability and the water saturation deviate from the linear relationship and show the downwarping trend in the semi-log coordinate, and the conventional water drive curves show the upwarping trend. Aiming at predicting the dynamic, recoverable reserve and recovery of oilfields at ultra-high water cut stage, a new formula characterizing the relation between the ratio of oil and water relative permeability and the water saturation was proposed, derivation of a new water drive curve was done by reservoir engineering methods, and the formula of recoverable reserve and recovery was derived. Comparison of the new water drive curve and the conventional one through numerical simulation and field application showed higher accuracy and better adaptability resulted from the new water drive curve, which solved the problems of upwarping and big prediction error in curves of ultra-high water cut stage.

Index system evaluating water flooding development effect of oilfield at ultra-high water cut stage

The LaSaXing Oilfield has entered the ultra-high water cut stage, and the original evaluation indexes of water flooding development effect cannot reflect development status of the oilfield. In order to correctly evaluate the water flooding development effect of the oilfield at ultra-high water cut stage, the indexes were extensively selected in terms of geological conditions, development technologies, production management, and economic benefits, and they were initially screened by observation principle, the Delphi method, and theoretical analysis. Then, the evaluation indexes were quantitatively selected by Pearson correlation analysis and combination of gray clustering-rough set to establish the index system evaluating water flooding development effect of oilfield at ultra-high water cut stage. The practice showed that the index system evaluating the development effect, which was scientific, objective, and strongly applicable, had great significance for comprehensive evaluation of the water flooding development effect of oilfield at ultra-high water cut stage, analysis of development potential, and formulation of development adjustment plan.

Development prediction and the theoretical analysis in the ultra-high water cut stage for water-flooding sandstone reservoirs

A new relationship between the ratio of water and oil relative permeability, and the water saturation is proposed based on the flow characteristic in porous media in the ultra-high water cut stage which results in a new water flooding characteristic curve with reservoir engineering method. Then a new algorithm to forecast development indexes is derived on the basis of the new relationship above, the new water flooding characteristic curve and the production decline law using Welge equation in which there are many parameters including time, water cut, the average water saturation and the oil recovery that can be used to evaluate the recoverable reserve. Through the examinations with the numerical simulation method and the on-site application, it shows that the new algorithm can give an accurate prediction with an relative error less than 6 %, which is instructive for the oil field development.

Multi-factor prediction of water flooding efficiency based on a time-varying system

ABSTRACTThe neural network prediction method gets good historical matching between prediction indices and influence factor indices, while the differential simulation prediction method can reflect the changing trend of prediction indices; considering these new traits, a new multi-factor prediction method is proposed to organically combine these two prediction methods. At first, the input–output relation between water flooding efficiency in ultra-high water cut stage and their influence factors is viewed as a time varying system, then the BP neural network is introduced in parameter identification of differential simulation to obtain a new multi-factor prediction method of functional simulation based on the time varying system. This new prediction model has got good self-adaptability since its parameters change by time. Moreover, it has better results in the mid-long-term water flooding efficiency prediction because the non convergence problem appeared in the coupling process can be overcome in the training process of the neural network by variable learning rates. In the end, practical output prediction cases in two different oilfield blocks in China are given. The computational results show that the prediction results obtained using the new multi-factor prediction method are in good agreement with the reality, even much better than the results obtained by other prediction methods.

Application and Study on Relationship Between Relative Permeability Ratio and Water Saturation Curve

In the process of oil field development, the law of water cut is usually described by exponent model, but during the early water breakthrough stage and ultra-high water cut stage, relative permeability ratio of oil to water (<i>K_ro/K_rw</i>) and water saturation (<i>S_w</i>) is no longer linear relations in semilog coordinate, so it has an important influence on water cut increasing rate, theoretical production index, oil displacement efficiency, relationship between recovery and water cut etc. Based on relation curve character of relative permeability ratio of oil to water (<i>K_ro/K_rw</i>) and water saturation (<i>S_w</i>), this paper proposes a new function model in order to reduce prediction error, such as production index and water cut increasing rate. According to nonlinear properties of the model, Newton algorithm is supposed to be used for optimization solution. Finally, take relative permeability data of P Oilfield as an example to testify, and results show that fitting precision of the model is quite high and it possess nicer applicability. On this basis, the relationship between water cut and recovery, relationship between water cut increasing rate and recovery are derived. By comparing water cut and water cut increasing rate with recovery degree, it can be used to guide the development as the foundation of geology and reservoir of P Oilfield.

The Application of Multistage Fuzzy Comprehensive Evaluation Mathematics Method for the Analysis of Determining the Remaining Oil in Ultra-High Water-Cut Oilfield

After the water flooding sandstone oilfield entering the ultra-high water-cut developing phase, the remaining oil distribution has become increasingly fragmented, how to quantitative distinguish the remaining oil potential is the key to influence oilfield development, using multilevel fuzzy comprehensive evaluation mathematics method, comprehensive analyzed the classification reservoir’s producing conditions during the ultra-high water-cut developing phase, established a quantitative evaluation method from geological and develop factors, solved the problem of analyzing remaining oil in deferent kinds of reservoirs, realized the quantitative characterization of remaining oil in the ultra-high water-cut oilfield.

Study and Application of Design Optimization of Horizontal Wells in a Thick Positive Rhythm Oil Layer

Remaining oil is enriched at the top of the thick positive rhythm oil layer during the ultra-high water cut stage. While the conventional vertical wells cannot produce good development for such remaining oil, the horizontal wells can bring effective results. In this study, typical well groups were selected from the Gudao Oilfield, and a geological model was established. By using the reservoir simulation technology, the design of horizontal wells was optimized under the current vertical well pattern, and the energy supply manners for horizontal wells were optimized. The research results were applied to oilfield development, and good development effects have been obtained.

The Research on Improving the Efficiency of Injection-Production of the Lamadian Oilfield in Ultra-High Water Cut Stage

With the oil field developing, the water cut increased, gradually and the efficiency of injection-production reduced year by year. Since the water flooding of Lamadian Oilfield entered extra high water cut period, the distribution of flow flied become more and more complex. The distribution of remaining oil and ineffective circulation is complex. The existing of ineffective circulation led to the flooding efficiency reducing sharply and cost of crude oil per ton by water flooding increased. In order to control production energy consumption in the extra high water cut, the method of improving the efficiency of Injection-production is studied in the Lamadian oilfield. Through the analysis of injection-production status, the factors that influence the injection efficiency is studied. The distribution of ineffective circulation which seriously affects the efficiency of Injection-production is made clearly. According to the factors that influence the efficiency of injection-production, based on flow field characteristics of water flooding, the countermeasure to enhance efficiency of injection-production is put forward in order to reduce the energy consumption and cost of producing crude oil.