缝洞型碳酸盐岩油藏流体流动表征方法探讨

塔里木盆地缝洞型碳酸盐岩油藏储集空间尺度差异大、流动复杂,很多学者认为渗流理论不能解决其流动表征问题,应该用管流理论解决。为厘清这一问题,从管流与渗流的概念、单相流流动特征及数学表征方法、油水两相流流动特征及数学表征方法3方面,研究了管流与渗流的关系,在此基础上,分析了管流方程描述缝洞型碳酸盐岩油藏流体流动的可行性,并对缝洞型碳酸盐岩油藏流体流动的表征方法进行了探讨。结果表明,从研究的角度,渗流可视为小尺度复杂管道管流;单相流时,管流存在层流、紊流两种流态,渗流也存在层流、紊流两种流态,层流状态,描述管流与渗流的方程是统一的,紊流状态,二者的描述方程不一致,但都是考虑惯性力的影响;两相流时,管流存在多种流型,渗流因尺度小、流型简单,管流基于流型建立了不同的流动表征模型,渗流利用相渗曲线解决两相流问题。说明,管流与渗流并不“冲突”,渗流即是小尺度复杂管道管流,只是由于学科不同、研究对象不同,对流体流动采用了不同的表征方法。缝洞型碳酸盐岩油藏描述不确定大,受油藏描述精度和研究范围的制约,现有管流的处理方法并不适用描述缝洞型碳酸盐岩油藏流体的流动。缝洞型碳酸盐岩油藏的流体流动表征问题应该在渗流力学的架构内,部分借鉴管流的处理方法来解决。

融合权重注意力和密集残差连接的图像超分算法

在光学相机远距离拍摄图像时,由于光线衰减和环境噪声的影响,图像容易变得模糊且难以清晰识别。为应对这一挑战,提出了一种基于权重注意力和密集残差连接的图像超分算法(image super-resolution algorithm based on weighted attention and dense residual connections, WADRNet)。首先,在网络的浅层特征提取阶段,提出一种非对称卷积模块,以替代传统的卷积模块,提高了模型的信息提取能力,尤其是对边缘和纹理等关键特征的提取;其次,采用密集残差结构,在不增加额外计算量的同时实现跨层特征传递和信息的有效利用,增强了模型的上下文特征提取能力,更好地还原图像;最后,在窗口注意力模块融入权重通道注意力模块,有效地利用全局感受野特性。实验结果表明,WADRNet在自制数据集上明显领先于其他模型,尤其在峰值信噪比和结构相似性等方面;同时,该模型在公开数据集上也表现出良好的效果。因此,该方法能够显著提升低分辨图像像素质量,在工程领域具有广泛的应用潜力和价值,尤其适用于需要远距离成像的应用场景。

塔河油田缝洞型碳酸盐岩油藏水驱后剩余油分布主控因素与提高采收率途径

综合岩心、测井、地震、生产动态等多方面资料,对缝洞型碳酸盐岩油藏储集空间多尺度特征、储集体类型、缝洞体空间形态及分布模式、与生产井的配置关系等进行了系统研究,分析了各因素对剩余油分布的影响,建立了水驱后剩余油分布的主控因素模式;结合塔河油田的开发实践,系统研究了提高原油采收率的方法与途径。研究表明,缝洞型碳酸盐岩油藏水驱后剩余油分布主控因素可归结为局部高点、井控不足、连通通道屏蔽和弱水动力4大类。缝洞型碳酸盐岩油藏提高采收率是一个系统工程:天然能量开发阶段,做好生产调控,防止底水窜进;注水早期,依据储集体类型、连通性、空间位置构建注采关系,提高水驱控制及动用程度,尽量减少剩余油;注水开发中后期,依据剩余油分布主控因素及分布特征,通过加强井控、利用重力分异和毛细管的渗吸作用、扰动(改造)流场等措施,实施精准挖潜。同时做好技术储备,开展储集层改造、新型注入介质、智能优化开发等技术的研发,做好注水、注气技术的接替,最大限度地提高采收率。

塔河油田缝洞型碳酸盐岩油藏水驱开发特征及改善对策

以塔河油田缝洞型碳酸盐岩油藏注水开发实践为基础,综合应用地质、地球物理、示踪剂测试、生产动态等资料,对其水驱开发特征进行了系统研究,建立了低效水驱模式,并针对性提出了改善水驱技术对策。研究结果表明,缝洞型碳酸盐岩油藏水驱开发呈现三大特征:①受效方向单一;②注水利用率低;③注水失效的主要原因为底水水侵。主要存在低水驱控制型、低水驱动用型、低洗油效率型3大类10亚类低效水驱模式。改善水驱开发效果的对策包括:①围绕连通缝洞体(或缝洞群)构建(或完善)注采关系,通过完善井网、改善连通等提高水驱控制程度;②通过调驱、注采参数优化、改变水驱方向、变强度注水等提高水驱动用程度;③通过改善岩石及油水界面性质提高水驱洗油效率;④通过提高生产井井底压力、封堵水侵通道、降低底水能量等方式抑制底水。同时,还要综合利用多种技术手段提高油藏描述精度,提高技术实施有效率。

基于物质平衡的超深断溶体油藏弹性驱产能主控因素分析

以塔里木盆地Q单元为例,基于物质平衡原理,从储量、能量、流度3大方面分析超深断溶体油藏弹性驱产能主控因素,解释不同断裂级次弹性驱产能差异。结果表明:超深断溶体油藏弹性驱产能主控因素包括缝洞储集体规模、地层弹性能量和流体流动能力,这3个因素整体均呈主干断裂大于分支断裂、分支断裂大于次级断裂的特征;弹性驱单井累积产油量、日产油量、阶段累积产油量均与单井控制储量呈强线性关系;单井累积产油量和单井控制储量与初始地层压力乘积在对数坐标上是一条斜率近似为1的直线;综合弹性压缩系数、缝洞储集体规模对累积产油量影响大于初始地层压力影响;流体流动能力越强,平均单井日产油量越高;要提高超深断溶体油藏弹性驱产能,早期井位部署应优选规模大、地层破碎程度高的缝洞储集体,开发中后期要尽量提高单井控制储量。

缝洞型碳酸盐岩油藏开发技术的认识与思考--以塔河油田和顺北油气田为例

塔里木盆地缝洞型碳酸盐岩油藏是油田开发面临的新的油藏类型,存在产量递减快、采收率低和储量动用率低等问题。剖析了中国石化塔河油田和顺北油气田缝洞型碳酸盐岩油藏地质特征及开发面临的挑战,系统总结了中国石化在缝洞型油藏描述、开发建产和提高采收率等方面的技术进展,针对塔河油田和顺北油气田的不同开发阶段,提出了下一步技术攻关建议。缝洞型碳酸盐岩油藏经过多期构造运动、岩溶作用和油气充注,储集体非均质性极强,油、气、水分布复杂,给油藏描述、地质建模、储量评价、效益建产、注水-注气、钻井工程、酸压改造、井筒举升等带来一系列挑战。经过20年的开发实践,中国石化西北油田形成了基于地球物理的体积雕刻、断裂精细解析和岩溶系统表征技术,以及基于岩溶相控的地质建模、靶向酸压和注水-注气提高采收率等技术。为实现顺北油气田高效开发,需进一步开展基于断裂解析的成藏特征研究以及基于地球物理雕刻的储集体相控地质建模、流体相态特征及高压物性、油藏组分数值模拟、油藏地质力学与数值模拟耦合、油气藏与举升一体化模拟、井位优选和钻井轨迹优化等工作。为实现塔河油田大幅提高采收率目标,需进一步开展缝洞结构描述、岩溶成因系统研究、储量动用评价、注水-注气机理及规律研究、缝洞井节点网络模拟和动态监测系统研究等工作。

塔河油田缝洞型油藏注入水利用状况评价

塔河油田缝洞型油藏注水开发中后期注入水利用率低,亟需优化调整。但由于缝洞型油藏非均质性强,裂缝发育,存在注入水"外溢"问题,现有评价指标难以对其进行有效评价。在分析缝洞型油藏注入水利用特征的基础上,根据注入水在地下的去向,提出4个评价指标:升压指数、驱油指数、窜失指数和漏失指数,并给出了计算方法。通过在塔河油田6区S80单元TK713井组的应用,显示该评价方法量化表征了注入水在地下的去向,评价结果可以有针对性地指导调整措施的制定。

Controlling factors of remaining oil distribution after water flooding and enhanced oil recovery methods for fracturecavity carbonate reservoirs in Tahe Oilfield

Based on comprehensive analysis of core, well logging, seismic and production data, the multi-scale reservoir space, reservoir types, spatial shape and distribution of fractures and caves, and the configuration relationship with production wells in fracture-cavity carbonate reservoirs were studied systematically, the influence of them on the distribution of residual oil was analyzed, and the main controlling factors mode of residual oil distribution after water flooding was established. Enhanced oil recovery methods were studied considering the development practice of Tahe oilfield. Research shows that the main controlling factors of residual oil distribution after water flooding in fracture-cavity carbonate reservoirs can be classified into four categories: local high point, insufficient well control, flow channel shielding and weak hydrodynamic. It is a systematic project to improve oil recovery in fracture-cavity carbonate reservoirs. In the stage of natural depletion, production should be well regulated to prevent bottom water channeling. In the early stage of waterflooding, injection-production relationship should be constructed according to reservoir type, connectivity and spatial location to enhance control and producing degree of waterflooding and minimize remaining oil. In the middle and late stage, according to the main controlling factors and distribution characteristics of remaining oil after water flooding, remaining oil should be tapped precisely by making use of gravity differentiation and capillary force imbibition, enhancing well control, disturbing the flow field and so on. Meanwhile, backup technologies of reservoir stimulation, new injection media, intelligent optimization etc. should be developed, smooth shift from water injection to gas injection should be ensured to maximize oil recovery.

Theories and practices of carbonate reservoirs development in China

Carbonate reservoirs in China have the characteristics of diversified accumulation pattern, complex structure and varying reservoir conditions. Concerning these characteristics, this article tracks the technical breakthroughs and related practices since the 1950 s, summarizes the developed theory and technologies of carbonate reservoir development, analyzes their adaptability and problems, and proposes their development trend. The following theory and technologies have come into being:(1) carbonate reservoir formation mechanisms and compound flow mechanisms in complex medium;(2) reservoir identification and description technologies based on geophysics and discrete fracture-vuggy modeling method;(3) well testing analysis technology and numerical simulation method of coupling free flow and porous media flow;(4) enhanced oil recovery techniques for nitrogen single well huff and puff, and water flooding development techniques with well pattern design in spatial structure, changed intensity water injection, water plugging and channel blocking as the core;(5) drilling and completion techniques, acid fracturing techniques and its production increasing techniques. To realize the efficient development of carbonate oil and gas reservoirs, researches in four aspects need to be done:(1) complex reservoir description technology with higher accuracy;(2) various enhanced oil recovery techniques;(3) improving the drilling method and acid fracturing method for ultra-deep carbonate reservoir and significantly cutting engineering cost;(4) strengthening the technological integration of information, big data, cloud computation, and artificial intelligence in oilfield development to realize the smart development of oilfield.

Experiments on the influences of well pattern on water flooding characteristics of dissolution vug-cave reservoir

Based on the similarity criterion, volcanic rock samples were taken from outcrops to make experimental models. Water flooding experiments of five-spot well pattern, nine-spot well pattern, five-spot to nine-spot well pattern, the relationship between relative well and fracture positions, and injection rate in dissolution vug-cave reservoirs with/without fractures were carried out to analyze variation regularities of development indexes, find out development characteristics of water flooding with different well patterns and sort out the optimal water flooding development mode. For dissolution vug-cave reservoirs without fractures, five-spot well pattern waterflooding has very small sweeping area, serious water channeling and low oil recovery. When the well pattern was adjusted from five-spot to nine-spot well pattern, oil recovery could be largely improved, but the corner well far from the injector is little affected. In dissolution vug-cave reservoirs with fractures, when the injector and producer are not connected by fractures, the fractures could effectively connect the poorly linked vugs to improve the development effect of water flooding. Whether there are fractures or not in dissolution vug-cave reservoirs, the development effect of nine-spot well-pattern is much better than that of five-spot well pattern and five-spot to nine-spot well pattern, this is more evident when there are fractures, and the edge well has better development indexes than corner well. At the high-water cut stage of water flooding with nine-spot well pattern, the oil recovery can be further improved with staggered line-drive pattern by converting the corner well into injection well. It is helpful to increase the oil production of corner well of nine-spot well pattern by increasing the injection rate, and improve ultimate oil recovery, but the water-free production period would be greatly shortened and water-free recovery would decrease.

基于节点网络模型的缝洞型碳酸盐岩油藏动态描述技术

缝洞型碳酸盐岩油藏非均质性极强,缝洞体离散分布,基于地球物理雕刻技术的静态描述存在较大不确定性。动态描述技术利用动态资料深化油藏认识,是动静结合提高油藏描述精度的重要途径。现有动态描述技术多基于连续介质理论构建,很难反映缝洞体离散分布的特征,与地球物理雕刻结果"兼容性"较差。针对缝洞体离散分布的特征,创建一种基于节点网络模型的动态描述技术。首先,提出基于节点网络的离散缝洞表征方法,建立节点网络模型自动生成方法,实现地球物理雕刻模型与节点网络模型快速转换;其次,基于节点网络模型,建立流动表征及开发指标计算方法,算例显示,产量、压力等开发指标计算结果吻合度超过93%,计算速度提升156倍;最后,形成缝洞关键特征参数反演方法,明确缝洞型油藏3个Ⅰ类、4个Ⅱ类共7个关键特征参数,基于拉丁超立方抽样建立辅助历史拟合方法,确定缝洞关键特征参数概率分布,算例显示,缝洞体储量、水体体积、断裂渗透率等反演误差约为10%,满足动态分析需求。该技术在塔河油田多个单元(井区)进行验证及应用,开发指标历史拟合符合率达90%以上,实现了缝洞体地质储量及动用程度的量化表征,提高了开发措施实施的针对性和有效性。

超深断溶体油藏油井动用深度确定方法及其对开发的指导意义

超深断溶体油藏是近年来在塔里木盆地发现的一种断控缝洞型碳酸盐岩油藏,油井生产过程中井底下方油气沿断裂高导流通道向井底流动。为表征油井纵向动用范围,提出了"动用深度"的概念,并建立基于井温的油井动用深度确定方法。动用深度定义为超深断溶体油藏油井生产时井底下方流体开始向上流动的位置到井底的垂向距离。在油井纵向动用位置,纵向上驱动压力梯度等于流动阻力、流速等于0、流温等于静温。利用井温法可计算油井动用深度,本质上是基于超深断溶体油藏非等温流动特征确定"热源"位置。研究认为:基于温度—深度线性关系的油井动用深度控制方程,其分母为静温梯度与流温梯度差。油嘴尺寸越大,油井动用深度越深且流体热损失越小,这均导致相同深度流静温差越大。油井动用深度概念及确定方法的提出在超深断溶体油藏油柱高度认识、储量计算、动用方式优化等方面具有重要意义。超深断溶体油藏的初始静压并不"静",基于超深断溶体油藏油井生产压差和油藏压降的油藏工程评价指标计算方法需重新建立。

超深油藏物质平衡方程修正及应用

压缩系数是影响油藏物质平衡方程准确性的关键参数,其大小与地层压力密切相关,超深油藏地饱压差、油藏压降较大,但传统超深油藏物质平衡方程忽略压缩系数随地层压力的变化。为完善超深油藏物质平衡方程,考虑岩石孔隙体积压缩系数、地层水压缩系数、地层原油压缩系数、地层原油的两相体积压缩系数以及气体压缩系数随地层压力的变化,修正不同驱动方式(弹性驱、水压驱动、气顶驱、溶解气驱、综合驱动)传统超深油藏物质平衡方程。研究结果表明:传统油藏物质平衡方程未考虑压缩系数随地层压力的变化、未采用微分或积分法求解,不适合超深油藏;传统油藏物质平衡方程均是近似方程。若忽略压缩系数随地层压力的变化且做进一步近似处理,修正后超深油藏物质平衡方程可转化成传统油藏物质平衡方程,证实超深油藏物质平衡方程的修正过程及最终表达式可靠。利用修正后超深油藏物质平衡方程计算得到塔里木盆地超深油藏G-02井动态地质储量为188.65×10^(4)t,而传统油藏物质平衡方程计算结果偏大,相对误差为19.19%;随油藏压降增加,修正后超深弹性驱油藏物质平衡方程计算动态地质储量逐渐减小。