注水是一种常见的提高采收率方法，利用自动控制ICD可实现采收率的有效提高！ 来自 |?JPT编译 | TOM 惊蛰 为弥补油藏亏空及压力自然降低造成的产量下降，由研究人员在致密油区块进行了二次注水开发研究，重点关注可以获得较完整历史数据的Bakken地层。 在研究区域，最初的完井和井距设计不合理，导致从注入井到生产井间形成窜流通道。这通常是由水力压裂造成的。在某些情况下，这种窜流通道具有有限的水驱波及效率，被称为无效注水循环。通过实施化学和机械导流技术，处理了无效循环问题，并取得了不同程度的成功。 对多级压裂井进行水驱的最简单方法是不使流体转向流动或分隔而直接从地面注入。因为水遵循阻力最小的路径流动，所以可能造成沿着井筒不均匀的注入并进入地层。在某些情况下，可能会通过裂缝路径产生窜流无效循环。 使用分布式温度传感（DTS）装置，操作员能够调查分析注入井是否发生窜流。通过使用各种粘性流体和固体暂堵剂，进行了许多尝试以重新引导来自阻力最小的路径的流体流动。这些措施的效果各不相同，在某些情况下，需要作业多次才能有效。因此操作员开始研究井眼部分的机械分流和隔离分注，以实现物理控制沿井筒侧面的不同区域的流速。 可以调节ICD的喷嘴直径来弥补由于井筒不同位置渗透率变化和压力损失（称为趾跟效应）导致的储层和裂缝注入量变化。这些装置可以在裸眼中运行，也可以在固井或未固井的套管中运行。 在这项研究中，对具有多个自动ICD装置的两级套管的管柱进行了试验。通过液压封隔器与管柱趾部的循环阀共同作用，循环阀能够使组件安装期间的流体正常循环。液压封隔器使用一个普通投球装置关闭循环阀进行坐封。一旦封隔器同时坐封完毕，通过连续油管（CT），使用细直径、可延伸的开关工具打开套管，注入井开始恢复注入。 操作员使用的系统中的关键部件是自动ICD装置，可以使用CT部署的液压开关工具多次使用（打开或关闭）。在打开的位置，使用碳化钨喷嘴实现流量控制。每个ICD最多可装配四个喷嘴，可实现灵活控制回压。当单个喷嘴的流动区域不能充分适应所需的流速时，则使用两个或多个喷嘴的组合。在该项研究中，每个ICD点的单个喷嘴尺寸均足以实现指定的流速和转向。 盲建模算法——在项目的初始阶段，由于有效数据有限和时间限制，重点研究近井储层区域。与水力压裂形成的裂缝渗透率相比，储层基质渗透率基本被认为是可忽略的。水力压裂模型在建模中被定义为具有非常高的相对渗透率的区域。这些渗透率参数以及其他近井地带的性质将加入到油藏数值模拟的边界条件中。 目标井的网格块尺寸被定义为*×*×*m，通过部署在靠近井眼放置，能够高清晰度捕获流体从井到油藏的流动过程。距离井筒越远，网格块被定义的尺寸越大，以便减少模拟时间。基础方案（无ICD）的模拟结果显示不均匀的注水剖面。这被认为是较高压降和高渗透率（窜流区域）组合的结果。 通过数据分析，提供了工作流程中需要设计、分级和优化的ICD配置所需指标和参数。并提出建议：在每个隔段使用规格均一的喷嘴尺寸，并在井段之间使用相同的间距。一帮将这种方法称为盲建模算法，其通过分析沿井筒的压降效应，提供改进的流量均衡模式。然而，这可能导致高渗透性区域不像改变喷嘴尺寸方法那样阻塞的效果好。模拟结果表明，较小直径的ICD喷嘴可以获得更好的注入流体分布，并且通常会形成较高的注入压力。 基于生产测井工具的方法：模型校准。为了更好地了解ICD安装前后的注水剖面变化，将DTS分析加入到工作流程中。DTS解释软件中包含用于流动建模的类似分析方法。通过对储层渗透率进行各种敏感性优化，使测量的注入速率与储层模拟模型相匹配。 光纤分布式温度测量方法使用工业激光在线路上发射**-ns的信号。在数据包通过光在光纤传送期间，少量从光纤中散射出去。可以分析该散射光以测量沿光纤的温度变化。因为光速是恒定的，所以可以通过使用时间采样，每隔一段就产生一束散射光，形成沿光纤的连续光谱记录。可以获得沿着井筒整个长度的温度记录。 为了收集数据，沿目标井水平段在管道内部通过单端测井电缆部署DTS光纤。利用热分析软件建立井眼和近井地带的轴对称有限元热模型。一旦匹配成功，就可以明确储层区域中变量的分布，并提供标准的单个区域流速。 在确定了喷嘴尺寸的若干灵敏度参数之后，便明确了能够提供最佳射流分布的ICD配置，最大注入量位于最靠近底部的位置。由于这些位置具有接近均匀的流体分布，因此它们被组合在一个井段中，并且喷嘴尺寸经过特殊设计，限制流体在该区域内的流动并可转向至井筒的其它区域。 使用校准后的DTS现场测量输入数据进行注入剖面建模，可提供准确的基准注入剖面。这样可以基于其特定参数对ICD配置进行定制化设计以优化各个井筒。 自****年底以来，开发商已成功安装了**多个ICD系统。截至****年第一季度，Viewfield Bakken地区ICD系统成功安装案例就有**个。平均注入率提高了***％，没有明显窜流现象，产量平均增加了**％，一些油井的产量几乎翻倍。To offset production decline caused by normal pressure decline and reservoir drainage, secondary recovery using water injection has been administered in three Saskatchewan tight oil plays. This study will be focused on the Bakken formation, the area with the most-complete historical data set available to the authors. The original completion and well-spacing plan has resulted in occasional direct water channeling from injection to production wells. This is believed to be caused by hydraulic fracturing. In some cases, this communication has limited waterflood sweep efficiency and is referred to as short-circuiting of injection fluid. Chemical and mechanical diversion techniques have been implemented to address short-circuiting with varying degrees of success. Field Development The simplest means to waterflood a multistage fractured well is to reverse the direction of flow and to bullhead water from the surface without diverting or compartmentalizing fluid flow. Because the water follows the path of least resistance, nonuniform fluid injection along the wellbore and into the formation may occur. In some instances, short-circuiting of producing wells through fracture paths may occur. Using distributed temperature sensing (DTS), the operator was able to investigate wells that were suspected of short-circuiting or channeling. Many attempts were made to redirect flow from the paths of least resistance by use of various viscous fluids and solid diverters. The effectiveness of these treatments was inconsistent and, in some cases, required multiple applications. The operator began investigating the application of mechanical diversion and isolation of sections of the wellbore to enable physical control of flow rates into different areas along the lateral wellbore. Compartmentalization With ICDs The nozzle diameter of ICDs can be adjusted to compensate for variations in reservoir and fracture injectivity resulting from variable permeability effects and frictional pressure losses along the wellbore, known as the heel-to-toe effect. The installations can be run in openhole configurations and within cemented or noncemented tubulars. In this study, tubing strings with several active ICDs with two-position sleeves were trialed. Hydraulic packers were used along with a circulation valve at the toe of the string that allowed fluid circulation during installation of the assemblies. The hydraulic packers were set using a common ball-drop system that closes the circulation valve. Once the packers were simultaneously set, a slim-diameter, expandable shifting tool was run on coiled tubing (CT) to open the sleeves. At that point, the well was ready to start or resume injection. A key component in the systems used by the operator are the active ICDs (Fig. *), which can be exercised (opened or closed) multiple times with a CT-deployed hydraulic shifting tool. In the open position, flow control is achieved using tungsten carbide nozzles. Each ICD can accommodate up to four nozzles, enabling flexibility in backpressure potential. When the flow area of a single nozzle cannot accommodate the desired flow rate adequately, a combination of two or more nozzles is used. For this study, a single nozzle size at each ICD point was sufficient to achieve the designated flow rates and diversion. Blind-Modeling Approach. At the initial stage of the project, because of the limited data availability and time constraints, the near-wellbore reservoir region was the area of focus. Reservoir matrix permeability was considered negligible in contrast with the conductivity of the hydraulic fractures present. The hydraulic fractures were modeled as zones with very high relative permeabilities. These permeabilities, along with other near-wellbore properties, were then increased throughout the boundaries of the reservoir simulation. The gridblock size for the subject well was defined at *×*×* m, placed close to the wellbore to capture a high resolution for well-to-reservoir fluid movement. The farther away from the wellbore the gridblocks were positioned, the larger their size was in order to reduce simulation time to a reasonable level. The base-case (no ICD) simulation showed a nonuniform water-injection profile. This was believed to be the result of a combination of a higher drawdown and high-permeability zones (short-circuit zones). The work flow provided valuable metrics required to design, rank, and optimize ICD configuration with limited data. Use of a uniform nozzle size for each compartment, and use of similar spacing between compartments, is recommended. This is referred to as the blind-modeling approach. This method will provide improved flow equalization through a pressure-drop effect across the wellbore. However, it may lead to cases where higher-permeability zones are not choked as optimally as they are in a variable-nozzle-size approach. Simulation outputs demonstrate that smaller-diameter ICD nozzles result in better injection distribution and will generally result in higher injection pressure. Production-Log-Tool-Based Approach: Calibrating the Model. To understand injection profiles before and after ICD installations better, DTS analysis was incorporated into the work flow. DTS-interpretation software used for this purpose incorporates a similar analytical approach for flow modeling. The injection rates measured were matched with the reservoir-simulation model by performing various sensitivity optimizations with the reservoir permeability. Fiber-optic-distributed temperature measurement uses an industrial laser to launch **-ns bursts of light down an optical fiber line. During the passage of each packet of light, a small amount is backscattered from molecules in the fiber. This backscattered light can be analyzed to measure the temperature along the fiber. Because the speed of light is constant, a spectrum of the backscattered light can be generated for each meter of the fiber by using time sampling. A continuous log of spectra along the fiber is provided. A temperature log can be calculated every meter along the entire length of the fiber (and wellbore). To collect the data, a single-ended wireline-deployed DTS fiber was run inside the tubing along the horizontal section of the subject well. An axisymmetric finite-element thermal model for the well and near-wellbore region was built using thermal-analysis software. Once a match is achieved, the distribution of the variable in the reservoir zones is defined uniquely and the model provides measured individual zone flow rates. After a number of sensitivities on nozzle size had been established, an ICD configuration (Table * of the complete paper) was determined that provided the optimal injection distribution. The largest volume of injection was located in the stages closest to the heel. Because these stages had near-uniform distribution, they were grouped together in one compartment and nozzle size was designed to restrict flow within this zone and divert to the rest of the compartments. Modeling injection profiles calibrated with DTS field-measurement inputs provide an accurate baseline injection profile. This allows for customization of ICD configurations to optimize individual wellbores on the basis of their specific parameters. Field Results Since late ****, the contributing operator has successfully installed more than ** ICD systems in southeastern Saskatchewan. The Viewfield Bakken area accounts for ** of the successful ICD system installations as of Q* ****. Improvements in injection rates of ***% on average have been achieved without direct channeling effects. Oil-production rates have increased **% on average, with some wells reaching close to ***% improvement.