The Performance of Water Floods with Horizontal and Multilateral Wells

Abstract

The use of horizontal and multilateral wells in the oil industry has increased rapidly during the last two decades. The main reason for this upsurge is that horizontal and multilateral wells provide a large contact area with the reservoir, and therefore enhance the well productivity or injectivity better than conventional vertical wells. The high productivity coupled with the recent advances in drilling technology for horizontal and multilateral wells has made their application an economically viable option. In this study, the performance of nonconventional wells in water flooding projects was investigated using numerical simulation techniques. Extensive three-dimensional, fine-mesh simulation runs are performed to determine the oil recovery by nonconventional wells under different operating/reservoir conditions. Results show that the pattern used has a significant effect on the displacement performance of nonconventional wells. The study shows the various conditions under which nonconventional wells will perform better than the use of conventional vertical wells.     

常规稠油油藏水平分支井渗流特征及产能评价

水平分支井已?成为开发边际油藏、常规稠油油藏、低渗透油藏、裂缝油藏、高含水油田剩余油挖潜的重要手段,也已经成为研究热点。首先研究了常规稠油油藏水平分支井渗流特征,在对水平分支井生产段（主支和分支）进行数学描述的基础上,利用势叠加原理,并考虑了各分支之间以及与主支之间的干扰,推导出油藏与生产段耦合条件下,常规稠油油藏对称水平分支井和非对称水平分支井的产能评价数学模型。并且将该模型应用于渤海常规稠油油田水平分支井产能计算,计算结果与该井投产后的实际产量误差在20％以内。     

PRODUCTIVITY OF HORIZONTAL AND MULTILATERAL WELLS

This paper introduces a new semi-analytical technique that can be applied to calculate the productivity of vertical, horizontal and multilateral wells. The well location and profile can be arbitrary. The reservoir region containing the well must be homogeneous (isotropic or anisotropic) and it may have constant potential or no-flow outer boundaries. Constant rate, constant bottom hole pressure and a combination of these constraints can be imposed on the wells. It is shown that under certain conditions the well productivity is strongly influenced by the pressure drop in the well and the type of conditions that exist at the reservoir boundaries. For multilateral wells the interaction among laterals can also influence productivity. In many cases, conventional techniques can result in large errors.     

PRODUCTIVITY OF HORIZONTAL AND MULTILATERAL WELLS

This paper introduces a new semi-analytical technique that can be applied to calculate the productivity of vertical, horizontal and multilateral wells. The well location and profile can be arbitrary. The reservoir region containing the well must be homogeneous (isotropic or anisotropic) and it may have constant potential or no-flow outer boundaries. Constant rate, constant bottom hole pressure and a combination of these constraints can be imposed on the wells. It is shown that under certain conditions the well productivity is strongly influenced by the pressure drop in the well and the type of conditions that exist at the reservoir boundaries. For multilateral wells the interaction among laterals can also influence productivity. In many cases, conventional techniques can result in large errors.     

分支水平井技术在单家寺特稠油油藏开发中的应用

通过对单家寺油田单2块沙一段特稠油油藏特征的系统研究,探讨了分支水平井开发特稠油油藏边际储量的巨大优势。分支水平井具有泄油面积大、单井产量高、节约钻井费用等特点,可实现特稠油边际储量的有效动用。以单家寺油田单2块沙一段为例,从分支水平井部署的位置优选、分支水平井参数优化及轨迹设计与优化等方面描述了水平分支井的地质设计技术,并提出在分支水平井钻进过程中进行实时跟踪分析,以确保分支水平井的顺利完钻,从而达到高效开发特稠油边际储量的目的。     

多分支水平井产能敏感性分析

多分支水平井是开发低渗透油气藏的重要手段.结合目前先进的多分支水平井半解析产能预测模型,对影响多分支水平井产能的重要油藏因素和井型参数进行了敏感性分析.研究结果表明:油藏供给边界性质及主井筒的展布方位会对多分支水平井产能产生很大影响,其中四周定压油藏边界的影响最明显;在断块油藏中,应将多分支水平井布于油藏中部,根据多分支水平井的泄油面积来确定井网密度.分支长度、分支数目、分支角度是影响多分支水平井产能的重要井型参数,应选择尽可能大的分支长度,三分支以上的分支数目和不小于30°的分支角度.     

水力深穿透射孔井产能计算方法及开发效果分析

水力深穿透射孔技术的成孔结构、渗流条件与多分支水平井比较接近,因此可以通过多分支水平井产能公式来研究水力深穿透射孔井的产能.从多分支水平井产能公式导出了水力深穿透射孔井的产能公式和表皮系数公式,射孔孔径、孔深、孔数、表皮系数对水力深穿透射孔井产能的影响分析结果表明,增加水力深穿透射孔的孔深和增大孔密,可提高水力深透射孔井的产能,且水力深穿透射孔技术能穿透近井污染带,有效连通地层和井筒,提高产能;水力深穿透射孔技术在薄油层的效果好于厚油层,它更适合对薄油层进行改造和作业.     

水平井在吐哈盆地红南油田底水油藏开发中的应用

根据油田地质特征,应用油藏数值模拟方法对比分析了红南油田白垩系油组应用水平与直井的开采效果,论证了应用水平井开发的可行性。同时根据油田地质特征及油藏数值模拟进行水平井地质设计、产能分析,确定其合理产能。通过与油田生产动态资料相对比,表明了水平井对底水油藏具有良好的开发效果,水平井产能的确定结果是可信的,其方法也是可行的。     

气藏水平井生产系统动态分析模型

对于水平井开发气藏，其生产系统由气藏内渗流和水平井井筒内流动两部分所组成。首先仿造采油指数的定义来定义压力平方形式下的采气指数，分别建立了气藏渗流及水平井筒流动的数学模型，该模型具有压力平方的形式，然后应用体积平衡原理将气藏内流动和井筒内流动联系起来，建立了产量耦合下生产系统分析模型，该模型实际上是水平气井的流入流出动态分析模型，分为层流、光滑管壁紊流、粗糙管壁紊流3种流态，推导出气藏水平井的产量随位置变化的关系式，并分析讨论了管壁相对粗糙度对气藏水平井产能的影响，在考虑水平井水平段内摩阻的情况下，实例分析了气藏水平井的流入流出动态关系。这为钻井工程、描述水平井流入流出动态、评价水平井产能、确定合理生产制度和管壁相对粗糙度对气藏水平井产能的影响提供了可靠的手段和方法。     

复杂断块油田跨断层水平井产能预测及分段长度优化方法——以西非A深水油田为例

布署跨封堵断层水平井是一种有效提高复杂断块油田单井动用储量、减少钻完井投资的开发手段。与常规水平井相比,跨断层水平井的产能预测和分段长度优化需考虑各断块内储层渗透率及厚度差异、封闭断层边界和井筒摩阻等多因素的影响。为综合考虑上述因素,基于势的叠加原理和镜像原理,建立了2种模式下的跨封堵断层水平井沿井筒径向流量分布计算模型,得到了适用于复杂断块油田的跨断层水平井产能预测方法,在此基础上形成了一种快速优化跨封堵断层水平井在各断块分段长度的油藏工程方法,并通过西非复杂断块深水油田的实例验证了模型和方法的可靠性及有效性。研究结果表明：在断块物性和各断块内水平井长度相同的条件下,跨1条封堵断层水平井径向流量分布整体上近似"U"形,而对于跨2条封堵断层水平井,由于两侧封闭断层边界的影响中部断块水平井段的径向流量显著低于两侧断块,以线性流为主要特征;对于复杂断块油田,水平井与断层边界的距离显著影响其产能,跨断层水平井长度相同时,水平井跟端和趾端距离断层边界越近,水平井产能越低,而常规水平井产能预测方法难以考虑封闭断层边界的影响导致其预测结果偏高。     

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.     

顺9井区致密油藏水平井一体化开发技术

顺9井区志留系碎屑岩储层存在埋藏深、温度高、物性差和底水发育,前期直井压裂后无法获得稳定产能的问题,为此,开展了水平井一体化开发技术研究。按照钻井、完井和压裂一体化设计的思想,水平井方位角设计为137.7°,与最大主应力方向正交,以提高压裂后泄油面积;使用油基钻井液钻进,保证井径规则,便于分段完井工具坐封;优选耐温130℃、耐压差70 MPa的裸眼封隔器,保证分段成功,并将压裂端口置于储层发育段,便于裂缝起裂;通过降低胍胶浓度和优化添加剂用量,形成耐温130℃的低伤害压裂液;采用油藏数值模拟方法优化压裂施工参数,应用常规压裂+人工隔层控缝高技术实现避水高度30 m,控缝高、深穿透压裂,形成顺9井区致密油藏水平井一体化开发关键技术。现场试验表明,水平井压裂后产能较直井提高4倍,2口井累计产油量达1.02×104 m3。水平井一体化开发技术提高了顺9井区致密油藏开发效果,对国内同类致密油藏开发具有一定借鉴意义。      

断溶体油气藏流动物质平衡方法

断溶体油藏由于“竖板”状的特珠形态,需要针对其流动特征,建立具有针对性的流动物质平衡方法。采用图示法分析了断溶体油藏油气流动模式,根据不同的流动特征以及对应的产能方程计算了油藏的渗透率,在此基础上建立了断溶体油藏的流动物质平衡新方法,并通过数值模型,验证了新方法的适用性。结果表明：断溶体油藏直井中的流动模式为线性流,与常规油藏水平井的流动特征相似,而断溶体油藏水平井中的流动模式为径向流,类似于常规油藏直井的流动特征;该方法和物质平衡方法得到的动态储量误差小于5%;新方法对储层渗透率的计算更接近实际井况。该研究对断溶体油藏动态储量核算具有指导意义。     

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.     

基于缝网扩展模拟的致密储层体积压裂水平井产能贡献分析

针对致密储层体积压裂缝网扩展预测和多重孔隙介质耦合流动模拟难度大的问题,开展了基于体积压裂裂缝扩展机理的致密储层流体流动规律研究,建立了多重介质不稳定渗流数学模型和多裂缝互相干扰条件下的压裂裂缝网络扩展模型,并采用有限单元法求解。以鄂尔多斯盆地致密油为例进行生产模拟,分析致密油藏体积压裂水平井不同孔隙介质产量贡献程度。研究表明:体积压裂水平井簇间距减小,则水力裂缝延伸长度变短,平均带长减小,改造面积先减小后趋于平缓,平均带宽和裂缝宽度先增大后趋于平缓;体积压裂水平井产能贡献以天然裂缝和水力裂缝为主,基质对产能贡献较小。研究结果为致密储层压裂水平井裂缝扩展模拟和产能预测提供了一定的理论基础。     

页岩夹层及压裂裂缝对蒸汽辅助重力泄油蒸汽腔扩展的影响

为了研究储层非均质特征对SAGD蒸汽腔扩展的影响,通过顺序指示模拟方法（SISIM）建立了不同页岩夹层分布模式,基于油藏数值模拟定义了“上部蒸汽腔分数”、“下部蒸汽腔分数”、“总蒸汽腔分数”的概念,研究了不同页岩夹层分布模式和压裂裂缝形式对SAGD蒸汽腔扩展的影响。研究结果表明:随着地层内页岩夹层发育的增多,页岩夹层对蒸汽腔扩展的限制作用增强,并呈现出蒸汽腔垂向扩展减弱而水平方向扩展增强的趋势;不同页岩概率下总蒸汽腔分数与采收率呈现较好的线性函数关系;压裂裂缝能改善SAGD蒸汽腔扩展和开发效果,垂直裂缝通过扩大蒸汽腔垂向发育高度加快了SAGD泄油速度,开发效果好于水平裂缝;移位垂直裂缝可以降低垂直裂缝导致的注采井间蒸汽窜流,蒸汽腔扩展及开发效果都好于垂直裂缝。     

Modeling of Fishbone Multilateral Well Productivity in Row Well Pattern

The technology of fishbone multilateral wells has been extensively applied worldwide in oilfield development. However there are few published models about fishbone multilateral wells' productivity. Based on conformal transformation and mirror image theory, a semianalytical model was derived for horizontal wells and fishbone multilateral wells' productivity in row well pattern, and verified through the electrolytical model experiment. The matching result showed there was only 12.15% maximum error.     

利用水平井提高稠油油藏剩余油采收率技术

为了挖潜辽河油田A块超稠油油藏井间剩余油,应用数值模拟软件描述了水平井有利部署区温度场、压力场及剩余油分布:蒸汽吞吐周期较高的生产井周围油层动用情况较好,油层温度高达190～210℃,但蒸汽加热的有效面积只在井筒周围20～30 m,井间仍然有大部分区域处于45～65℃的低温状态;由于蒸汽吞吐过程中的汽窜现象,部分井之间有热连通形成.动用最好的区域油层压力为3.00 MPa,一般在3.40～3.90 MPa.井间存在大量剩余油,剩余油饱和度大于50%.在兴Ⅲ、兴Ⅱ_2油层单层厚度大干5 m区域整体部署水平井30口,水平段长度250～400 m.模拟预测水平井蒸汽吞吐8周期后,平均单井累计产油25 220 t,油汽比0.42,采出程度为31.5%.与直井生产效果对比,加密水平井可以挖潜稠油油藏井问剩余油,提高该区块采收率.图5表3参10     

浅层超稠油水平井微压裂扩容技术及应用

针对新疆油田F油田齐古组非均质油藏驱泄复合井网加密水平井与老井不均匀连通的问题,从改善水平段井筒周围渗流条件出发,提出水平井微压裂扩容改造技术。通过室内岩心实验、地质力学有限元模拟及热采数值模拟技术,分析了微压裂扩容技术的可行性及扩容后储层变化特征。结果表明:储层石英含量高,黏土矿物含量低且孔隙结构发育,有利于注水扩容改造;稳定提压过程中扩大挤注液的波及范围,进而降低周围储层有效围压,可大幅提升扩容改造程度;扩容后储层纵向位移量和孔隙度增大幅度明显优于横向,有助于上下注采井连通。微压裂扩容后经过5周期吞吐预热,油井间可快速建立热连通,预热期间周期产油、油汽比明显提升,且水平段动用程度大幅改善。研究结果可为提高驱泄复合井网的注采井间连通性提供借鉴。     

水平井在火山岩底水油藏开发中的应用

根据准噶尔盆地石西油田石炭系火山岩油藏地质特征,应用现代油藏工程和数值模拟技术对比分析了该油藏应用水平井与直井的开采效果,论证了应用水平井开发的可行性。同时根据油田地质特征进行水平井地质设计、产能分析,确定其合理产能。油田动态数据对比表明,水平井对深层、低渗透、裂缝性、块状底水、异常高压的天然裂缝性火山岩油藏具有较好的适应性,水平井产能的确定结果是可信的,其方法也是可行的。