Maximizing volumetric sweep efficiency in waterfloods with hydrocarbon F-Φ curves

Waterflooding is by far the most commonly used method to improve oil recovery. Success of a waterflood depends on its ability to sweep mobile oil efficiently. Incorrect or insufficient design may lead to increases in cost associated with water cycling and poor sweep. Most waterflood management is restricted to classical methods (e.g., surveillance or pattern balancing) or sensitivity studies centered on finite difference simulation. Most of the time, conventional methods fail to account for subsurface heterogeneity. Optimizing sweep via numerical modeling is time consuming in waterfloods with large number of wells or a relatively high-resolution numerical grid.We propose a practical and efficient approach for rapid and full-field optimization of waterfloods. Our method focuses on optimizing volumetric sweep efficiency using streamlines. We introduce two new concepts: the hydrocarbon F-Φ curve and Hydrocarbon Lorenz Coefficient (L_C-HC). We show that these concepts can be easily derived from streamline simulation and can be used for optimum waterflood management. L_C-HC serves as a unique measure of the flow - or dynamic - heterogeneity. We show that minimizing L_C-HC results in maximum volumetric sweep efficiency. The method is straightforward: we evaluate the sensitivity of L_C-HC to variations in operating conditions in a design of experiment (DoE) study, describe the L_C-HC as a function of those operating conditions using response surface methods, then select the operating conditions that minimize L_C-HC (maximize sweep efficiency). The main advantages of our method are its speed, flexibility to start optimizing at any arbitrary time regardless of the history, and ability to handle large problems. The new approach requires running a streamline simulator only a few time steps, so multi-million cell models are simulated in minutes.We verified our approach with several synthetic examples. An example shows that a 100,000 cell, complex reservoir with 13 wells, and 29 completions can be optimized in less than 4 h, leading to significant increase in recovery efficiency and reduced water cycling. We then apply the method to a model of the Brugge field, the SPE comparative problem on recovery optimization. Improved production response illustrates the power of the new method.     

碳酸盐岩注水替油效果差油井主要影响因素及治理对策

塔河采油二厂注水替油开发效果明显,近三年减缓,年自然递减平均在10%~15%,统计发现仍有16.1%井数比例的油井注水替油效果差,表现为注水轮次少,生产高含水。分析认为,影响注水替油效果的主要因素是井眼位置低、储层条件不好、注水参数设计欠合理三者之一或复合构成,并提出了治理对策;同时完善了注水替油选井及注水参数设计原则。现场实施取得了较好的效果,具有推广意义。     

水力扩容在注水替油失效井中的应用

塔河油田缝洞型碳酸盐岩油藏目前主要采用注水替油的方式来提高采收率。随着注水替油工作的不断开展,注水失效井逐步增多,如何挖掘失效井潜力成为当务之急。从失效原因分析入手,在总结常规失效治理手段的基础上,提出了水力扩容的思路来进一步对剩余储量进行挖潜,提高储量动用程度,同时初步确定了水力扩容有利井选井条件。     

微地震监测水驱前缘技术在哈得双台阶水平井的应用效果评价

哈得4油田薄砂层油藏首创采用双台阶水平井注水开发,然而双台阶水平井的动态监测是一个全新的课题,注入水朝哪个方向推进、主力驱替方位如何、水驱前缘波及何处都难以判断。示踪剂方法施工复杂、周期长、精度不够,只能粗略判断,而利用微地震监测水驱前缘技术,却可准确得到注水井的水驱前缘状况、注入水的波及范围、优势注水方向,为中后期合理调整、挖掘剩余油、提高最终采收率,提供了可靠的技术保障。     

Hot water flooding and cold water flooding in heavy oil reservoirs

Murphy Oil’s Seal asset in the Peace River Oil Sands region in North West Alberta, Canada, has a remarkable capacity for implementation of Enhanced Oil Recovery (EOR) processes. Some wells in Seal have shown strong historical production due to excellent permeability and the foamy solution gas drive mechanism. The reservoir characteristics in this portion are highly variable where determining the most suitable EOR method is very challenging. Two of the potential EOR candidates which have been evaluated for this portion include conventional cold waterflooding and hot waterflooding. Results of EOR core analysis, logging, detailed seismic and petrophysical studies, and history-matched reservoir simulation and forecast indicate that cold waterflooding outperforms hot waterflooding. This is surprising as hot waterflooding is believed to outperform cold waterflooding in most medium heavy oil reservoirs.     

水平井注水动态模拟研究

为了评价面积０．１６ｋｍ２（４０英亩）的五点井网水平井系统（水平注水井和水平生产井）和垂直井系统（垂直注水井和垂直生产井）注水开发的原油采收率，进行了二维和三维模拟研究。三维模拟结果表明，在水－油流度比一定的情况下，垂向渗透率与水平渗透率的比值、注采速度、油层厚度等参数对采收率几乎没有影响。无论垂直井还是水平井系统，采收率都随流度比的增加而减少。由此断定，流度比是影响采收率的主要参数。这与Ｃｒａｉｇ，Ｇｅｆｅｎ，Ｍｏｒｓｅ等人的常规注水试验结果一致。但是，用水平井系统所得到的采收率比垂直井系统的高。已经推导出，在一个假想的５点法井网中随流度比变化的体积驱油效率相关曲线，可用这种曲线估算设想参数范围内的采收率。     

Study on the downhole permanent low frequency pulsating water injection technique

Waterflood technique with pressure fluctuation, especially with low, ultra low frequency, changes the continuous water flow into the flow with pressure fluctuation, and can prevent contamination precipitation, formation plugging and Jamin effect. It also can prevent the plugging of water injection well, decrease the pressure of waterflood and increase the rate of water injection. On the basis of the existing eccentric injection mandrel, used the energy storage character of air energy accumulator and the pressure switch character of pressure control valve, fixed the plunger valve for pressure control on the position of blanking plug, then developed one new injection mandrel with low frequency character, which can inject water continuously with low, ultra low frequency. Water fluctuation produced during the water injection affect the formation directly and is useful to break down, prevent plugging and augment injection.     

提高油田注水系统效率的探讨

分析了目前长庆油田的注水现状，指出油田注水系统能耗高的主要原因是选用注水泵不合理，造成注水回流量过大，有些泵站注水回流量接近泵排量的50％，使注水系统每吨水单耗过高，从而造成大量的电能消耗。因此，提出了减少注水回流量、降低能耗的具体意见，即加强现场管理，严格各项制度，合理选择注水泵，并对泵用电动机提出了改进方案。     

滨南油田一区回注污水的实验研究

滨南油田一区油井含水率已高达９０％以上，采出的大量地层水（污水）回注地层。但由于污水的水质不能满足储层的要求，回注后在１５～２０ｄ的时间内回注井的吸水能力就大幅度下降。通过综合研究及模拟实验表明：回注污水对该区储层的伤害机理是污水中有４３．７６％的固相颗粒与储层孔喉不匹配，对储层产生了严重的堵塞，有端面堵塞也有孔喉内的深部堵塞，对储层的伤害率平均为９３．８５％。从减轻对储层伤害的角度出发，通过流动实验表明，该区回注的污水至少应通过孔径为６．０μｍ的过滤措施；现场的应用证明该项实验研究为该区的污水回注提供了科学依据。     

水平井与垂直井联合井网波及系数研究

利用数值模拟方法对五点法、七点法、九点法注水方式不同见水时刻水平井与垂直井联合井网的波及系数进行的研究结果表明,油水流度比、水平井穿透比及水平井与水平方向的夹角对3种联合井网波及系数的影响较大.在对各种影响因素分析对比的基础上,得出了各影响因素与波及系数的关系曲线,并对数值模拟结果进行了回归,得到了联合井网的波及系数与各影响因素之间的定量关系.