Study of the mechanisms of streamline-adjustment-assisted heterogeneous combination flooding for enhanced oil recovery for post-polymer-flooded reservoirs

Streamline-adjustment-assisted heterogeneous combination flooding is a new technology for enhanced oil recovery for post-polymer-flooded reservoirs.In this work,we first carried out a series of 2D visualization experiments for different chemical flooding scenarios after polymer flooding.Then,we explored the synergistic mechanisms of streamline-adjustment-assisted heterogeneous combination flooding for enhanced oil recovery and the contribution of each component.Test results show that for single heterogeneous combination flooding,the residual oil in the main streamline area after polymer flooding is ready to be driven,but it is difficult to be recovered in the non-main streamline area.Due to the effect of drainage and synergism,the streamline-adjustment-assisted heterogeneous combination flooding diverts the injected chemical agent from the main streamline area to the non-main streamline area,which consequently expands the active area of chemical flooding.Based on the results from the single-factor contribution of the quantitative analysis,the contribution of temporary plugging and profile control of branched preformed particle gels ranks in the first place and followed by the polymer profile control and the effect of streamline adjustment.On the contrary,the surfactant contributes the least to enhance the efficiency of oil displacement.

The simulation of gas production from oceanic gas hydrate reservoir by the combination of ocean surface warm water flooding with depressurization

A new method is proposed to produce gas from oceanic gas hydrate reservoir by combining the ocean surface warm water flooding with depressurization which can efficiently utilize the synthetic effects of thermal, salt and depressurization on gas hydrate dissociation. The method has the advantage of high efficiency, low cost and enhanced safety. Based on the proposed conceptual method, the physical and mathematical models are established, in which the effects of the flow of multiphase fluid, the kinetic process of hydrate dissociation, the endothermic process of hydrate dissociation, ice-water phase equilibrium, salt inhibition, dispersion, convection and conduction on the hydrate disso- ciation and gas and water production are considered. The gas and water rates, formation pressure for the combination method are compared with that of the single depressurization, which is referred to the method in which only depres- surization is used. The results show that the combination method can remedy the deficiency of individual producing methods. It has the advantage of longer stable period of high gas rate than the single depressurization. It can also reduce the geologic hazard caused by the formation defor- mation due to the maintaining of the formation pressure by injected ocean warm water.

A Novel Interacting Multiple-Model Method and Its Application to Moisture Content Prediction of ASP Flooding

In this paper,an interacting multiple-model(IMM)method based on datadriven identification model is proposed for the prediction of nonlinear dynamic systems.Firstly,two basic models are selected as combination components due to their proved effectiveness.One is Gaussian process(GP)model,which can provide the predictive variance of the predicted output and only has several optimizing parameters.The other is regularized extreme learning machine(RELM)model,which can improve the overfitting problem resulted by empirical risk minimization principle and enhances the overall generalization performance.Then both of the models are updated continually using meaningful new data selected by data selection methods.Furthermore,recursive methods are employed in the two models to reduce the computational burden caused by continuous renewal.Finally,the two models are combined in IMM algorithm to realize the hybrid prediction,which can avoid the error accumulation in the single-model prediction.In order to verify the performance,the proposed method is applied to the prediction of moisture content of alkali-surfactant-polymer(ASP)flooding.The simulation results show that the proposed model can match the process very well.And IMM algorithm can outperform its components and provide a nice improvement in accuracy and robustness.

An enhanced oil recovery technique by targeted delivery ASP flooding

Aiming at the problem of the loss of the ASP flooding near the injection wells, this paper gives a new idea to enhance oil recovery called "Technique of Targeted Delivery", which combines the radial horizontal well with ultra-short radius drilled by high pressure water jet with the ASP flooding, the horizontal wells work as the "Target channel" transport the ternary composite system to the remaining oil enrichment area directly, to avoid the loss of the ternary composite system near the injection wells. The plate homogeneous experiment and numerical simulation show that the technique can significantly improve the sweep efficiency and the effect of the oil displacement, and greatly improve the oil recovery rate. The optimal flooding parameters of the target transport technique are: the right angle target, the length of the channel is about 15% of the well distance and the injection volume of the ternary composite system is 0.4 PV. Under such conditions, this technique can enhance recovery by 48.87% and 22.04% respectively, compared with the water flooding and conventional ASP flooding. The target transport technique solves the problem of high loss of chemical agent in near-wellbore area during the ASP flooding, and compensates for the high cost of ASP flooding and the limitation of application, and has a broad application prospect.

Production calculation of the second and tertiary recovery combination reservoirs under chemical flooding

Based on the analysis of the production composition of reservoirs developed by the second&tertiary recovery combination(STRC),the relationship between the overall output of the STRC project and the production level during the blank water flooding stage is proposed.According to the basic principle of reservoir engineering that the“recovery factor is equal to sweeping coefficient multiplied by oil displacement efficiency”,the formula for calculating the ultimate oil recovery factor of chemical combination flooding reservoir was established.By dividing the reservoir into a series of grids according to differen-tial calculus thinking,the relationship between the ultimate recovery factor of a certain number of grids and the recovery de-gree of the reservoir was established,and then the variation law of oil production rate of the STRC reservoir was obtained.The concept of“oil rate enlargement factor of chemical combination flooding”was defined,and a production calculation method of reservoir developed by STRC was put forward based on practical oilfield development experience.The study shows that the oil production enhancing effect of STRC increases evenly with the in crease of the ratio of STRC displacement efficiency to water displacement efficiency,and increases rapidly with the increase of the ratio of recovery degree at flooding mode conversion to the water displacement efficiency.STRC is more effective in increasing oil production of reservoir with high recovery degree.Through practical tests of the alkali free binary flooding(polymer/surfactant)projects,the relative error of the oil production calculation method of STRC reservoir is about±10%,which meets the requirements of reservoir engineering.

A differential wide field electromagnetic method and its application in alkaline-surfactant-polymer(ASP) flooding monitoring

To improve effectiveness of ASP flooding, it is necessary to establish a reliable parameter design and tracking adjustment method to monitor the process of oil displacement. A differential wide field electromagnetic method was proposed and applied to the ASP displacement monitoring test in a block of the Daqing Oilfield. In the process of ASP flooding, the electromagnetic field was measured many times. The data acquired before the ASP flooding were set as the background field, and the resistivity model was obtained by inversion. Then, the resistivity data were calibrated by logging data and the resistivity model was established. Finally, the range and front of ASP flooding were deduced with the residual gradient from the spatial domain first-order difference of the resistivity model. Production data of well groups in this block have proved that this method can work out the range and front of ASP flooding accurately, providing support for optimization of ASP flooding parameters.

The Feasibility of ASP Flooding with Low Alkali Concentration in Heterogeneous Reservoirs

In this paper, as far as the ASP flooding in the pilot area of Daqing oilfield is concerned, the effect of apparent viscosity of ASP solution on enhanced oil recovery have been studied by comparison of experiments on artificial heterogeneous cores with on natural cores. The results showed that the decrease in the concentration of alkali could increase the apparent viscosity of ASP solutions, namely, the apparent viscosity increased and the IFT couldn’t get ultra low, and the oil recovery efficiency by ASP solution with a reasonably lower concentration of alkali was not less than that with a higher concentration of alkali and ultra low IFT. The experiments with models having impermeable interlayers between adjacent layers, and by means of “co-injection and separate production” showed that the ASP solution with a higher viscosity and a lower alkali concentration was more beneficial to starting-up medium and low permeability layers and enhancing total oil recovery. Therefore, to heterogeneous reservoir, as factors of affecting oil recovery, the apparent viscosity may be more important than the ultralow IFT. Furthermore, on the premise that the concentration of surfactant and the concentration of polymer keep constant, ASP flooding with low alkali concentration not only enlarges the selectable range of surfactants and decreases the cost of ASP flooding, but also solves the problem of alkali scales. Finally, a dynamic absorption experiment was performed with a 05 meter long linked-up natural core to determine alkali wastage in formation. The result being accord with the application case in the pilot confirmed that it was not necessary to add the alkali too much in ASP flooding from a new direction.

ASP复合驱油体系瞬时界面张力的研究

以胜利油田孤岛试验区原油为油相， 用正交试验筛选了碱／天然混合羧酸盐／聚合物驱油体系， 讨论了各组分对ＡＳＰ复合驱油体系油水瞬时界面张力的影响， 并探讨了各组分间的相互作用机理及其在油水界面的吸附机理．

ASP体系在大庆二类油层中的色谱分离现象及其对采收率的影响

ASP体系在二类油层中运移不同距离时,体系的黏度和及其与原油间的界面张力等均会发生变化。本实验采用不同长度的人造岩心(10、20、30、60和80 cm)来模拟ASP体系在油藏中的运移距离,通过测定各组实验产出液的黏度及其与原油间界面张力,分析ASP体系运移不同距离时体系性能的变化及其对采收率的影响。实验结果表明,随着ASP驱油剂运移距离的增大,复合驱采收率逐渐降低,且在近井地带附近采收率降低的幅度较大。复合驱采收率受复合体系的黏度和其与原油界面张力影响,在0~30 cm运移范围内,由于超低界面张力和较强流度控制能力的综合作用,驱油剂在油藏中的波及体积和驱油效率较大,复合驱采收率和最终采收率较高;当运移距离大于30 cm时,由于界面张力值迅速升高,其对采收率的贡献较小,此时体系的黏度在驱油过程中起着主导作用;复合驱采收率随着驱油剂相对注入量的增大而增加,适当地增大ASP驱油剂的相对注入量可有效的提高大庆二类油层的采收率。

关家堡海上油田开发早期ASP三元复合驱注入参数优选

关家堡海上油田已经完成了井网部署,即将投入商业开发。为了达到高速高效开发的目的,通过室内实验研究了注水开发初期实施ASP三元复合驱的可行性,对比了复合驱“早期—低浓度—大段塞”、“中期—中浓度—中段塞”和“晚期—高浓度—小段塞”3种注入方式下的驱油效果。研究结果表明,在关家堡海上油田推荐使用“早期—低浓度—大段塞”方式,即开发初期就实施复合驱,ASP三元复合驱体系为600mg/L聚合物、0.3%表面活性剂和1.2%碳酸钠,段塞尺寸为0.50倍孔隙体积。该研究成果对于关家堡油田的高速高效开发具有指导意义。

ASP复合驱用烷基苯磺酸盐表面活性剂的合成

以重烷基苯为主要原料,以SO3为磺化剂,合成ASP三元复合驱用烷基苯磺酸盐表面活性剂。探讨了原料组成、反应条件等因素对烷基苯磺酸盐产品性能的影响,研究了烷基苯磺酸盐表面活性剂的界面活性及稳定性。在室内合成研究的基础上进行了工业放大试验,工业试验合成产品界面活性优良,其ASP复合体系驱油效率比水驱驱油效率提高20％以上。

棉籽油酸单乙醇酰胺硫酸酯盐的合成及其在ASP驱油中的应用

为了提高石油采收率 ,用不经提纯的棉籽油脚为原料 ,制得棉籽油酸单乙醇酰胺硫酸酯盐。通过正交实验 ,找出了硫酸酯化的优化条件为 :反应温度 90℃ ,酰胺 /硫酸 (摩尔比 ) =1∶1.2 ,反应时间 5 0min。将硫酸酯盐与酰胺进行复配 ,与碱和聚合物构成三元复合驱油体系 ,可与克拉玛依七东一区原油形成 5× 10 -3 mN/m的超低界面张力。

ASP体系与大港和大庆原油的乳化特性研究

为了更为真实地反映化学驱中ASP三元复合体系与原油在地下的乳化过程,以大港和大庆原油为例,采用多测点长岩心,研究了不同碱用量条件下,NaOH/石油磺酸盐/部分水解聚丙烯酰胺三元复合体系在驱替过程中与原油的乳化特性。结果表明,ASP三元复合体系以油藏中的平均流速(约1m/d)驱替大港原油和大庆原油,在运移数厘米距离内就发生了乳化作用。ASP体系乳化原油的难易程度、乳化量及形成乳状液的稳定性与原油酸值、原油粘度和碱用量密切相关。碱用量越高,乳化量越大,乳状液越稳定。与高酸值、高粘度的大港原油相比,ASP体系与低酸值、低粘度的大庆原油易于发生乳化,但形成的乳状液稳定性较弱,乳化量较小。此外,实验结果还表明,乳化对提高采收率和采油速度有较大的贡献,乳化能力较好的体系,采油速度和采收率相对较高。

孤东原油组分与其ASP配方体系之间界面张力的研究

为探索三次采油配方的本质 ,寻找原油中对配方起主要作用的组分及其含量 ,以孤东原油为对象 ,首先得到其最佳三采配方 ,然后通过测量其与原油各个组分之间的界面张力 ,得到一些有价值的结果 :①以价格低廉的天然混合羧酸盐为表面活性剂的孤东原油的ASP(碱、表面活性剂及聚合物组成的三元复合体系 )配方 (质量分数 ) :0 .5 %SDC C(S) + 0 .7%复碱 (m(Na2 CO3)∶m(NaHCO3) =1∶1 ) (A) + 0 .1 %HAPM(P) ;②降低界面张力的能力以沥青质最大 ,胶质次之 ;③单独沥青质、胶质或者油分的模拟油 ,与ASP最佳配方体系的界面张力都比原油高 ,说明原油中各个组分存在协同效应 ;④胶质可作为原油的等效烷烃用于三次采油配方的研究 .

低碱ASP三元复合驱技术的适用界限分析

针对大庆油田三元复合驱的油层条件 ,利用渗透率变异系数为 0 .72的三层非均质模型进行了驱油物理模拟实验 ,系统地研究了碱及聚合物浓度对ASP驱采收率的影响 ,并利用加隔层模型和合注分采方式 ,研究了碱浓度对启动中、低渗透层的影响。结果表明 ,低碱ASP驱在提高体系粘度的同时也造成界面张力升高 ,因而有其适用界限。在给定的非均质油层条件下 ,ASP驱存在一个临界粘度 ,只有达到临界粘度后 ,采收率才随界面张力的降低而升高 ,即界面张力发挥作用的前提是充分扩大波及体积。若为追求高粘度而过于降低碱量或取消碱 ,也会因洗油效率下降而影响采收率。低碱ASP驱可以保证体系足够的粘度 ,更有效地启动中、低渗透层 ,即使界面张力仅达到1 0 - 2 mN/m 。

适用于纯梁原油的天然混合羧酸盐ASP体系

胜利纯梁采油厂原油含蜡量高 ,凝固点高 ,地层渗透率低 ,粘土含量多 ,而且对碱敏感性高。以天然混合羧酸盐为主 ,通过正交实验设计和界面张力最低值测定获得针对纯梁采油厂的最佳三元复合驱配方 ,界面张力最低值为 5 .2× 10 -4 mN/m ,对此配方进行了室内模拟驱油实验研究 ,采收率提高达 14.6 %— 16 .7%OOIP。

ASP三元复合体系在孔隙介质中的流变性

利用室内物理模拟的方法，对三元复合体系在多孔介质中的流变行为进行了研究，分析了聚合物、碱、表面活性剂浓度和岩芯渗透率对三元复合体系在多孔介质中的流变特征的影响规律，研究结果认为复合体系在多孔介质中呈现出剪切变稀和增稠双重流变特性，复合体系在多孔介质中出现粘弹流变特征的临界剪切速率随着聚合物浓度的升高而减小，随着表面活性剂和碱浓度的增加而增大。

确定ASP复合驱相对渗透率曲线的最优化方法

ＡＳＰ复合驱油体系相对渗透率曲线的确定是研究ＡＳＰ复合驱油体系的驱替机理和数值模拟的关键技术，由于ＡＳＰ复合驱的复杂性，单纯依靠实验测定其相对渗透率曲线是很困难的。本文应用渗流力学和最优化理论，将瞬时界面张力和聚合物的影响引入相对渗透率曲线模型，给出了描述ＡＳＰ复合驱油体系的数学模型及相对渗透率曲线参数估计的最优化模型，用原油采收率和岩心两端压差的加权平均作为拟合的目标函数，采用变尺度的最优化方法，反求出相对渗透率曲线模型中的参数。实例计算结果表明，该ＡＳＰ复合驱油体系的数学模型及求相对渗透率曲线的最优化方法是可行的和可靠的，并可有效地克服参数初值的敏感性问题。

ASP复合驱注采参数优化设计

根据正交设计方法和模糊数学原理 ,在室内试验及数值模拟研究的基础上 ,考虑到各项技术和经济指标的综合影响 ,建立了基于模糊综合评判模型的复合驱注采参数优化设计模型。同时 ,以孤东油田七区西Ng5 4- 6 1层复合驱试验为例 ,对化学剂组合方式、配方浓度、段塞尺寸、注采速度、注入方式、注入时机等参数进行了优化。综合分析表明 ,该方法能够用尽可能少的方案寻求各参数间的最佳协同效应 ,且便于决策。

适用于大庆油田的天然混合羧酸盐ASP驱油体系

针对酸值为０．１ ｍｇ ＫＯＨ／ｇ 的大庆原油，通过相态研究和界面张力测定进行配方初选，通过稳定性测定进行配方调整，得到了以天然混合羧酸盐ＳＤＣ为表面活性剂的ＡＳＰ三元复合驱油体系：１ ．２％ 复碱（ 质量比１∶１ 的Ｎａ２ＣＯ３ ＋ ＮａＨＣＯ３）＋ ０．６％ ＳＤＣ５＋ ０ ．５％ 植物胶（ 苎麻胶） ＋ ０ ．１６％ ＨＰＡＭ（ ＢＰ７） 。此体系与大庆原油间的最低瞬时界面张力为５ ．９３ ×１０－ ４ ｍＮ／ｍ 。在室内用两种填砂管模型进行驱油实验，得到的采收率为１８ ．８ ％ 和１９．１ ％ （ ＯＯＩＰ），注入１ ｇ ＳＣＤ５ 驱出原油１３８．３ ｍＬ。