The Design and Preparation of a Simulator for the Water Coning Phenomenon Applying in Fractured Reservoirs

Abstract

The problem of water production is one of the major technical, environmental, and economical issues associated with oil and gas production. The main goal of this study is to prepare a reservoir numerical simulator with emphasis on water coning. The study mostly involves the numerical simulation of water coning and includes proposed correlations in the literature. The computer program included four distinct modules to calculate: critical or maximum allowable oil rate, water breakthrough time, well performance after water coning take palaces, and water coning simulation. Flow equations of water and oil were discretized and numerically solved for two-dimensional coordinates. The implicit scheme was used to calculate unknown pressures of any grid block. For calculation of water saturation, explicit scheme was used. Real field data of a well in southwest Iran was put into the program and critical rate, water breakthrough time, well performance after water coning, and water coning simulation of reservoir were determined. The authors found that the results of correlations are very far from the reality. On the other hand, numerical simulation shows good agreement with real production data. In addition, it was observed that the present production rate of this well would result in rapid water coning.     

Performance of Horizontal Injection–Horizontal Production Wells in a Five Spot Pattern: Experimental Approach

Abstract

This article presents an experimental investigation to study the effect of horizontal injector well length on oil recovery in a five spot water flood pattern having arrays of horizontal wells. The results of this study show that breakthrough recovery increases as the length of the horizontal injection well increases. However, recoveries at 95% water cut were found to be almost the same for all the injection well lengths investigated. It is also found that the additional recoveries after water breakthrough decreases as the length of the horizontal injection well increases. This is associated with sharp increase in % water cut after breakthrough.     

An Experimental Study of Secondary WAG Injection in a Low-Temperature Carbonate Reservoir in Different Miscibility Conditions

Abstract

This experimental study is aimed at evaluation of the performance of secondary WAG injection in carbonate cores at different pressures. To do so, a comprehensive series of high-pressure high-temperature (HPHT) core flooding tests are conducted. The fluid system includes reservoir dead and live crude oil, CO₂, and synthetic brine while the chosen porous media consists of a number of fractured carbonate core samples. Parameters such as oil recovery factor, water and oil production rates, and pressure drop along the core are recorded for both dead and live oil. According to results, at first increasing pressure improves the oil recovery, but this improvement after MMP is not as significant as it is before MMP. Also recoveries of dead and live oils at same pressure show different values due to differences in miscibility condition of injected gas. Then as the graphs demonstrate, relative permeability reduction due to hysteresis effect has dominant effect on pressure drop curves. Finally, as the production rate curves show, nearly all of the remained oil after breakthrough is produced as the gas is being produced and almost no oil can be recovered during water production portions.     

底水油藏水平井水脊脊进规律

利用油气藏数值模拟软件,研究了水平井底水突破的位置。根据水平井的产量公式,推导出与垂面径向流的渗流阻力相应的生产压差。假设垂面上的生产压降满足对数分布,可得到考虑重力影响的底水脊进速度公式,并推导出油井的见水时间方程。最后,用实例验证了该方法的可靠性。研究表明,底水首先从水平井中部突破,并且随着生产时间的延长,底水脊进的速度会加快。合理增大水平井的水平段长度和避水高度,可以推迟油井的见水时间。     

The Impact of Sandstone's Geometry Form on Water Flooding Efficiency in Heterogeneous Reservoirs

Abstract

Due to the sedimentary environment, diagenesis effect, and tectogenesis effect, the geometry form of sandstone shows heterogeneity, which affects the water flooding efficiency, especially in continental sedimentary reservoir. First, according to distribution characters of sandstone, an idealized mode can be obtained. The 2-D and two-phase mathematical mode at certain inlet and outlet pressure was established. By applying discrete and differential numerical methods, the cumulative oil production under two conditions can be calculated. It is higher when the inlet end is wider part of the sandstone. Second, using streamline numerical simulation to build similar injection and production horizontal well model, the authors obtained analog and study sweep efficiency of different displacement directions. Last, by adopting reservoir numerical simulation method, the influence of geometric form of sandstone on water flooding efficiency of well pattern was further studied. The conclusion was drawn that when injector was deployed in narrow part of sandstone and oil well in the wide part, the speed of water flood front was fast, and water breakthrough times were shorter, which led to rapid water cut rises. Under certain bottomhole flowing pressure, formation pressure surrounding injector was a little higher, water injection rate dropped, and cumulative oil production decreased.     

一种预测底水油藏水锥动态及见水时间的新方法

底水油藏开发面临的核心问题是底水的锥进,准确预测底水油藏油井的见水时间,并采取相应的措施,可以延长油井的无水采油期,提高油井的累计产油量和采出程度。文中基于流体在多孔介质中的渗流规律,对底水油藏双重不完善井的水锥突破时间进行了研究。通过数学推导,得到了底水油藏油井水锥突破时间的计算公式,该公式考虑了油水流度比,原始束缚水饱和度,残余油饱和度等影响因素,并与其他底水油藏见水时间的公式进行了对比。实例分析表明,新的底水油藏油井见水时间公式的预测值较准确,并且与李传亮公式的结果较为接近,为预测底水油藏油井的见水时间提供了借鉴和指导。     

PERFORMANCE COMPARISON OF FRACTURED AND UN-FRACTURED VERTICAL AND HORIZONTAL WELLS IN RESERVOIRS WITH BOTTOM-WATER DRIVE

ABSTRACT

An experimental investigation, using a scaled three- dimensional rectangular model, has been conducted to study the production performance of un-fractured and fractured vertical wells under bottom water drive. The results are compared against those for un-fractured horizontal wells and horizontal wells with orthogonal and longitudinal fractures. The model represented a section of the drainage volume for a single horizontal well in one of the Middle East reservoirs. Kerosene and distilled water were used to represent the reservoir fluids, while glass beads were used to represent the porous medium. All experiments were conducted at the same production rate, which was chosen so that the oil–water interface would remain stable until it approaches the producing well. As expected, fracturing vertical wells greatly improves their performance by increasing oil recovery at breakthrough and ultimate recovery, delaying water breakthrough and reducing pressure drop. While horizontal wells have, in general, better performance than vertical wells, fractured vertical wells perform better than horizontal wells with regard to recovery, water breakthrough and pressure drop. Horizontal wells with orthogonal or longitudinal fractures are found to be superior to fractured vertical wells. In general, increasing the fracture penetration improved the production performance of both vertical and horizontal wells. Interestingly, it was found that extending the fracture penetration towards the original oil–water contact did not, as might have been expected, result in earlier water breakthrough.     

Study and Application of In-depth Water Control Technology for Production Wells

Abstract

In view of low oil increment and short valid period of conventional water shutoff for production well, the authors propose and develop a new in-depth water control technology for production well. The different-strength (from weak to strong) water shutoff agents are separately injected into a remote zone, transition zone, and near-wellbore zone in this technology, which can achieve the aim of in-depth water control, extending the valid period of water control, increasing oil production, and decreasing water cut. Physical and visual simulation experiments show that there is optimized displacement of 3:10 between production well and injection well for the water shutoff agent with the most oil recovery. Field tests in Jidong, Shengtuo, and Weizhou 11-4 oilfields also show that the in-depth water control technology is a reliable, feasible technology and worthy to be widely applied.     

提高原油采收率的一种新理论与新方法

近年来,水平井开采底水、气顶油藏显然在初期得到一些令人满意的效果,但对于气、水突入油井,依然没有抑制措施,当水突破油井以后,油井大量出水,影响正常开采,成为阻碍直井、水平井技术发展的一大技术难题。本文研究了油田开发中水气突入油井的机理,首次建立了消除水、气突入油井的新理论,并提出了消除水、气突入油井的多种工艺方法。采用此理论和工艺可高效地开采低渗油气藏、特种油气藏、中高含水期的已开发油藏,可延长油井的无水、气采油期,提高原油采收率,给油田带来重大的经济效益。     

Integrating Neural Network and Numerical Simulation for Production Performance Prediction of Low Permeability Reservoir

Abstract

It is difficult to predict the production performance of low permeability fractured oil reservoirs. This is because complicated factors such as geological and engineering factors affect well production performance. This paper presents a methodology to predict well production performance in the Hanq oil field, which is a low permeability fractured reservoir. Integration of neural network with numerical simulation is employed. First we study the regularity of fluid flow and oil displacement mechanism by injection well group numerical simulation and analysis of production performance. Then we form the “expert knowledge” affecting production performance. The neural networks based on expert knowledge are trained using production data. This method will play an important role in future waterflood management and the design of recovery strategy for the Hanq oil field.     

考虑应力敏感的低渗透底水油藏见水时间预测

目前预测低渗透底水油藏油井见水时间没有考虑渗透率应力敏感问题,基于低渗透底水油藏的渗流特征和储集层介质的压力敏感性等特点,推导出了考虑应力敏感等多因素影响的低渗透底水油藏底水突破时间预测公式。分析了应力敏感、启动压力梯度及油水黏度比对底水突破时间的影响。研究表明:应力敏感系数越大,底水突破越早;随着启动压力梯度增加,底水与井底之间的压力差值越大,底水突破的时间提前;油水黏度比越大,油井见水时间越早;油井见水时间随着产量的增加而提前,因此合理地设计生产井产量,可以延长油井无水采油期。     

基于生产动态数据的采油井水窜类型诊断方法研究

为提高油藏油水井调剖堵水的成功率,必须搞清造成采油井非正常出水的主要原因.基于采油井实际生产动态数据,根据理论分析结果,利用油井水油比、水油比导数与生产时间关系曲线的变化趋势,判断油井非正常出水的原因.由于实际生产动态数据中存在取值误差等噪音数据,因此首先采用小波变换方法对实际动态数据进行除噪,除噪后的采油井水油比导数与生产时间关系曲线不仅较好地还原了生产数据中蕴含的真实信息,而且使得斜率的正负值更加明显,从而保证了采油井水油比、水油比导数与生产时间关系曲线具有很好的光滑性和逼近度,提高了采油井出水类型诊断的准确性和可靠性.实例证明,该方法简单易用,结果可信.     

塔河缝洞型碳酸盐岩油藏油井见水特征浅析

高产油井突然见水是影响塔河奥陶系缝洞型碳酸盐岩油藏开发的主要因素,常规油藏工程方法很难解释、预测油井突然见水及含水变化规律。多年开发实践中,尝试采用管流方法分析油井突然见水现象,与管流典型特征(漩涡现象、回流现象)对应,探讨见水后邻井干扰造成的影响和波动规律,初步建立以管流为基础的缝洞型油藏见水分析方法,探讨水推油见水后的挖潜措施和油藏治理方法。此研究对塔河奥陶系油藏的动态研究和综合治理、改善开发效果有一定的指导意义。     

河道砂油藏注水初期“间注间开”技术应用

河道砂岩油藏纵向及平面非均质性均较强。局部发育边水,规模小,主要以弹性驱动为主,开采后期地层亏空严重,能量供应不足,注水补充能量是必然趋势。注水初期,注水方式的选择对注水开发起着举足轻重的作用。常规连续注水初期有效但容易发生水窜,后期改为周期注水效果差。对河道砂油藏初期注水提出了试验"间注间开"注水技术,即在注水井注水过程中油井停止生产,待能量补充到位后确定开井时机,将注水井停注,恢复油井生产。     

复杂高压气井地层出水判别及评价新方法

基于气井见水和出水量增大时气井水样氯根含量增大和气井产量稳定油压突降的特征,气井见水初期,可根据氯根浓度变化及油压突降来判别见水和评价产水量; 气井高含水期,可根据气井生产动态数据利用垂直管流估算法评价气井产水状况,即在气井垂直管流模型的基础上,利用气井产量、油压、油压下降速度等生产参数求解气井产水量。目前已形成了"由站到井"的复杂高压气井见水判别方法,并在判别特征参数( 氯根含量、日产气量、油压等) 上发展出了新的出水评价方法。该套方法简明实用,能有效判别及评价气井生产全时期的产水状况,为气田治水措施采纳、开发方案综合调整提供了参考依据。     

底水油藏的压锥效果分析

底水锥进是影响底水油藏开发效果的重要因素。底水锥进常常使油井过早见水、含水上升迅速、产量递减加快。关井压锥是人们常常想到的抑制底水锥进的方法之一,但压锥效果并不理想。因此,从理论上分析了压锥效果差的原因：底水锥进的动力为油井的生产压差,水锥动力强,水锥速度快,而压锥的动力为地层的水油重力差,压锥动力弱,压锥速度慢。还通过数值模拟方法对压锥效果进行了研究,模拟结果显示,压锥后油井的含水快速升高至压锥前的水平,油井产量虽略有提高,但与压锥期间油井关井损失的产量相比,仍然得不偿失。建议矿场上不要采用关井压锥的方法来克服底水锥进带来的不利影响。     

Application of Abrasive Water Jet Perforation Assisting Fracturing

Abstract

This article presents a new technology of abrasive water jet perforation assisting fracturing on Well Zheng 408-8, Bin Nan Production Plant, Shengli Oilfield. First, the balsting tool, with 9 nozzles, was lowered down to the payzone and perforated 90 tunnels with abrasive water jet after being moved upward 9 times. Then the fracture work was conducted and 18 m³ sands were squeezed into the formations. After that the well production reached 11.6 t/d liquid and 8.7 t/d oil, respectively, and this continued for 9 months. But before the job, nothing was produced from this well.     

The Investigation of SAGD Production Profile in a Naturally Fractured Reservoir (NFR)

Abstract

The steam-assisted gravity drainage (SAGD) process has been found as a promising enhanced oil recovery (EOR) process to recover bitumen and heavy oils. A few studies were done on the SAGD process in naturally fractured reservoirs. The effects of various reservoir variables and operational parameters on production profile were simulated using commercial software. The results showed that three different periods of oil production exist in SAGD process at naturally fractured reservoirs. At first, fractures depletion in the near well region (NWR) affect mainly the initial oil production rate. However, the preheated NWR matrixes cause the oil rate not to decrease suddenly. Then, due to rising of steam into upper layer fractures, oil rate increases and therefore the first flag of the oil rate pulse occurs. At third period, another flag of oil rate pulse with a reduction trend is observed due to fractures depleting and starting of oil drainage from its surrounded matrix blocks. The second and third period occur again as steam penetrates into another block in above well region (AWR). The number of oil rate pulses shifts to left by increasing preheating period and fracture density and also by decreasing well pair length. The number of pulses also increases with reduction in well pair length and fracture density. By increasing well spacing and fracture permeability and also by decreasing production bottom hole pressure and fracture density the pulses vanish.     

边水油藏水平井见水规律及控水措施研究

边水油藏水平井开采时,水平井见水是一个比较复杂的问题．它不仅受到井身轨迹如：水平段长度,避水距离等的影响,还与油藏的自身备件如：油水黏度比,各向异性有关。采用无因次水平段长度、无因次避水距离综合分析水平井的井身轨迹及油藏的自身条件对边水油藏水平井见水时间的影响,并给出各个影响因素与水平井见水时间的数学关系式。同时,通过正交试验的方法确定了见水时间影响因素的主次顺序。用注聚合物的方式控制边水突进,提高采收率的效果比较明显。本研究对边水油藏水平井的应用、合理井身轨迹的确定,以及水平井的控水增油有一定的指导意义。     

冷41断块边底水稠油油藏油井出水判别方法浅析

通过分析油井的生产动态,识别深层块状边底水稠油油藏油井出水特征,从而分析总结地层水的有效识别方法.油井如果见地层水,其水油比曲线存在拐点,即水油比变化率大于0.研究结果表明,冷41断块油井周期回采水率上升迅速,周期回采水率大于100%,且居高不下,因此可以判定油井见地层水.