Adaptability of Development Methods for Offshore Gas Cap Edge Water Reservoirs under Different Permeability Levels

The BZ 34-1 oilfield is a typical gas cap edge water reservoir in the Bohai oilfield. The main characteristics of the oilfield were multi-phase sand body stacking and the sand body was composed of three parts: gas cap, oil reservoir, and edge water. The actual production site results show that the permeability difference of multi-layer sand bodies has a serious impact on the development effect. This article establishes a typical reservoir model numerical model based on the total recovery degree of the reservoir and the recovery degree of each layer, and analyzes the impact of permeability gradient. As the permeability gradient increases, the total recovery degree of all four well patterns decreases, and the total recovery degree gradually decreases. The recovery degree of low permeability layers gradually decreases, and the recovery degree of high permeability layers gradually increases. As the permeability gradient increases, the degree of recovery gradually decreases under different water contents. As the permeability gradient increases, the reduction rate of remaining oil saturation in low permeability layers is slower, while the reduction rate of remaining oil saturation in high permeability layers was faster. By analyzing the impact of permeability gradient on the development effect of oil fields, we could further deepen our understanding of gas cap edge water reservoirs and guide the development of this type of oil field.

Development characteristics and orientation of tight oil and gas in China

Through reviewing the development history of tight oil and gas in China,summarizing theoretical understandings in exploration and development,and comparing the geological conditions and development technologies objectively in China and the United States,we clarified the progress and stage of tight oil and gas exploration and development in China,and envisaged the future development orientation of theory and technology,process methods and development policy.In nearly a decade,relying on the exploration and development practice,science and technology research and management innovation,huge breakthroughs have been made.The laws of formation,distribution and accumulation of tight oil and gas have been researched,the development theories such as"multi-stage pressure drop"and"man-made reservoirs"have been established,and several technology series have been innovated and integrated.These technology series include enrichment regions selection,well pattern deployment,single well production and recovery factor enhancement,and low cost development.As a result,both of reserves and production of tight oil and gas increase rapidly.However,limited by the sedimentary environment and tectonic background,compared with North America,China’s tight oil and gas reservoirs are worse in continuity,more difficult to develop and poorer in economic efficiency.Moreover,there are still some gaps in reservoir identification accuracy and stimulating technology between China and North America.In the future,Chinese oil and gas companies should further improve the resource evaluation method,tackle key technologies such as high-precision 3D seismic interpretation,man-made reservoir,and intelligent engineering,innovate theories and technologies to enhance single well production and recovery rate,and actively endeavor to get the finance and tax subsidy on tight oil and gas.

“Extreme utilization”development theory of unconventional natural gas

In the process of unconventional natural gas development practice,the"extreme utilization"concept that focuses on"continuously breaking through the limit of development technology"is gradually formed,and supports the scale benefit exploration of unconventional gas in China.On this basis,the development theory of"extreme utilization"is proposed,its theoretical connotation together with development technologies of unconventional natural gas are clarified.The theoretical connotation is that,aiming at"extreme gas reservoirs","extreme techniques"are utilized to build subsurface connected bodies,expand the discharge area,and enlarge the production range,to obtain the maximum single-well production,extreme recovery,and eventually achieve the"extreme effect"of production.The series of development technologies include micro/nano-scale reservoir evaluation,"sweet spot"prediction,unconventional percolation theory and production capacity evaluation,optimization of grid well pattern,optimal-fast drilling and volume fracturing,and working regulation optimization and"integrated"organizing system.The"extreme utilization"development theory has been successfully applied in the development of unconventional gas reservoirs such as Sulige tight gas,South Sichuan shale gas,and Qinshui coalbed methane.Such practices demonstrate that,the"extreme utilization"development theory has effectively promoted the development of unconventional gas industry in China,and can provide theoretical guidance for effective development of other potential unconventional and difficult-to-recovery resources.

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.

低渗透裂缝性油藏测井侧向剩余油挖潜措施研究——以长庆A油田为例

针对长庆A油田低渗透裂缝性油藏注水开发动态特点,通过深化精细基础地质研究,结合老区检查井取心、测井资料,开展了剩余油分布精细评价、不同水线距离的检查井水洗程度评价,以及裂缝对剩余油分布和开发效果的影响分析。结果表明,低渗透裂缝性油藏主向井水淹严重、侧向区剩余油富集,侧向剩余油挖潜设计方案可行;油藏井网加密调整后开发效果评价证实,侧向剩余油挖潜方案可减缓油藏递减、改善油藏的开发效果。可为同类油藏开发中后期实施井网调整、增储挖潜及油藏采收率提高提供有益借鉴。

苏里格气田致密气开发井网效果评价与调整对策

鄂尔多斯盆地致密气资源丰富,其天然气资源量占全国致密气总资源量的60%以上,已发现苏里格、神木、大牛地、延安、米脂等多个致密气田。其中苏里格气田引领中国致密气开发已20年,由于气田开发井网复杂多样,其结构特征与开发效果缺乏系统评价,因此未来天然气井网优化调整对策尚不明确。为此,充分利用区内1.8×104余口气井的动、静态生产资料,系统梳理了开发进程中井网的持续优化过程,将其划分为直井规则、混合、水平井整体、加密试验与欠完善等5种类型,并采用加密井增产气量评价方法,评价了不同井网的特征和开发效果,提出了高效调整对策。研究结果表明:(1)500 m×650 m、600 m×600 m井网下,天然气的采收率较高,但优化调整面临较大风险;(2)600 m×800 m井网较优,既可达到较高的天然气采收率,又具备优化调整空间;(3)混合开发井网占比高,但储量碎片化严重,优化调整潜力有限;(4)水平井整体井网的优化调整可能性较低。结论认为,针对成熟天然气开发区需加强剩余气精细挖潜与井网精准调整技术攻关,针对未开发区应强化储层结构精准描述与可视化部署、差异化井网实施与储量极致动用技术研究,从而为气田长期稳产及提高天然气采收率提供支撑,也为我国致密气藏高效开发提供技术参考。

基于动态特征的开发井网优化——以苏里格致密强非均质砂岩气田为例

鄂尔多斯盆地苏里格气田是典型的致密强非均质砂岩气田,储层有效砂体规模小、变化快、平面非均质性强、连通性差,开发难度很大,如何科学部署开发井来提高气藏采收率,是成功开发这类气田需要解决的首要问题。为此,在多年开展该气田开发方法研究成果和实际效果分析总结基础上,从开发井干扰现象分析入手,重新认识井网密度对采收率的影响。首次提出了井间干扰概念,并揭示了苏里格气田井间干扰概率与井网密度之间的关系,联合采用砂体精细解剖、油藏工程、数值模拟、经济评价等多种方法,建立了开发井网优化数学模型,得到了气田采收率和井网密度之间的定量描述。进而在综合分析的基础上给出了苏里格气田合理的开发井网:井网形式为平行四边形;井网密度为3.1口/km2,对应的井距为500m,排距为650m。开发实践效果证实,该方案在保证获得较好经济效益的同时,可最大程度地动用地质储量,提高气田最终采收率。

小断块边底水油藏开发实践与认识

江苏油田陈堡、安丰、周宋等复杂小断块边底水砂岩油藏,油藏规模小、含油带窄、隔夹层复杂,在早期开发中都是采取一套井网控制,逐层上返的开发模式,油井投入开发后普遍呈现含水上升快,产量递减迅速等问题。在剩余油研究的基础上,根据油藏形态、隔夹层分布、边底水能量及油水粘度比等,有针对性地采取不同的调整策略,转变油藏开发模式,调整层系井网,充分挖掘各类剩余油潜力,大大改善了油藏开发效果。

低渗碳酸盐岩气藏提高采收率技术对策

系统的提高采收率技术对策是改善低渗碳酸盐岩气藏进入开发中后期效果的重要技术手段。针对该类气藏进入开发中后期地质、生产动态以及开发方式上相对于早期的变化,围绕气田挖潜与提高采收率,梳理了该类气藏在面临侵蚀沟槽发育、储层低渗非均质性强、低压低产井多等特征时,剩余储量挖潜、提高储量动用程度和井网完整性评价中的关键技术问题。并在复杂岩溶储层描述、低渗气藏精细动态评价技术的基础上,提出以“沟槽挖潜、井网优化、增压开采、排水采气”为核心的提高采收率技术思路与对策,并将研究成果应用于鄂尔多斯盆地M气田。结果表明:M气田可新增动用储量220.3×108 m3,增产气量303.4×108 m3,提高气田采收率6.8%。研究结果对国内同类气藏的开发与实践具有指导意义。

乐安油田草31断块气顶稠油油藏开发技术界限研究

针对乐安油田草31断块的气顶稠油油气藏,在落实天然气储量规模和油气分布的基础上,运用油藏工程方法,借助数值模拟手段,对小气顶油藏的开采方式、布井方式、注水时机等开发技术界限进行了优化研究,确定出适宜该油气藏的开发方案。

油田经济极限井网密度计算新方法

经济合理的井网密度对提高油藏波及系数和最终采收率至关重要,是油田调整开发方案的依据。针对谢尔卡乔夫公式计算井网密度的结果与生产实际不符的问题,从理论及方法上对经济井网密度进行了系统阐述,明确了目前常用井网密度的内涵和外延,重新界定了经济极限井网密度的定义,在此基础上对谢尔卡乔夫公式进行了修正完善,建立了新的适合于中国石化不同油区和不同类型油藏计算经济极限井网密度的经验公式。根据各区不同类型油藏实际的储量丰度和油藏流度统计数据,结合修正的谢尔卡乔夫公式对中国石化5个主力油区及各油区的中高渗透、低渗透和稠油3种不同类型油藏的经济极限井网密度进行了计算。结果表明,东部5个主力油区和不同类型油藏在油价为80美元/bbl时可钻加密井分别为20515和19366口。

商三区中块沙二下油藏开发存在的问题与对策

商河油田商三区沙二下亚段储层属低孔低渗储层 ,其岩性以粉砂、细砂为主 ,砂泥岩薄互层。储层砂体层间差异小 ,但层内非均质性很强。经过多年的注水开发 ,研究区在注采井距、油水井套损、注入水水质等方面的问题日益突出。根据油田的开发现状 ,针对存在的问题 ,建议修好并开启所有注水井和生产井 ,提高注入水的水质 。

大庆喇萨杏油田三类油层开发方式探讨

大庆油田目前已进入特高含水期的开发阶段,但检查井及动态监测等资料结果表明三类油层还有相当一部分储量动用差或不动用.由于这部分剩余油在空间上分布比较复杂,且目前薄差层的水淹层解释精度远远不够,使三类油层三次加密选井选层难度加大,加密井初期含水高,经济效益不理想,因此提出三类油层开发不能单纯靠水驱加密调整,有必要采取加密与三次采油技术相结合的开发方式,高效开发三类油层.同时针对目前复杂的层系井网现状,确定该方式下三类油层层系组合、井距和井网部署方式.

气顶油气藏细分油藏类型协同精细开发研究

气顶油气藏在开发中存在气油比迅速上升,油井产量快速下降,检泵周期短等问题,开发难度逐步加大。为此,引入气顶指数,结合对储层地质认识、生产动态特征分析和现场实验的成果,提出细分油藏类型,协同精细开发的技术思路。将气顶油气藏细分为气顶油藏和油环气藏,两类油藏能量、开发特征差异较大,采取两套井网协同注水开发。对于油环气藏,采取边部注水,平衡气顶、油环能量的调整方式;对于气顶油藏,采取面积注水,整体补充油藏能量的调整方式。现场实施表明,该调整方式能取得较好的开发效果,提高采收率5%,该成果对气顶油气藏开发具有较好的指导意义。

新场气田致密砂岩气藏采收率影响因素分析

致密砂岩气藏储量丰度低,地质条件复杂,提高气藏采收率难度大。以四川盆地典型层状致密砂岩气藏新场气田J_(2)s_(2)气藏为例,采用岩心实验、动态分析及数值模拟等方法,从地质方面和开发方面对影响气藏采收率的因素进行综合研究。结果表明,地层渗流能力、含气性等地质因素以及开发井网、废弃地层压力、工程工艺等开发因素对致密砂岩气藏的采收率影响较大。研究成果可为国内外致密砂岩气藏提高采收率对策的制定提供支撑。

高升油田雷64断块块状砂砾岩底水油藏高效开发技术

雷64断块为一巨厚块状砂砾岩底水油藏,采用底部注水、中下部采油方式。该区块油层具有储层均质性较好,强亲水、中等—弱敏感性,储量丰度高,水驱油效率高,润湿性好,油水黏度比低等特征,适合注水开发。区块一直保持低含水条件下的高速开采,低含水采油期累计采油68.5×104t。开发初期月产油量不断上升,注水开发后,由于累计注采比一直小于1以及采油速度高,底部注水开发方式不能有效补充上部油层的地层能量,产油量不断递减。从注水开发效果看,水驱储量控制程度及动用程度高,分别达到99%和78.6%;"注水与产能建设同步"开发方式有效补充了地层能量,含水上升合理。由于单一底部注水难以有效保持地层能量,因此进行了气顶驱试验,有效补充了上部地层能量,缓解了下层系注入和产出之间的矛盾,有利于区块的长期稳定高效开发。

井网对溶蚀孔洞型储集层水驱开发特征的影响实验

根据相似准则理论,选取火山岩露头岩样建立实验模型,开展裂缝型与无裂缝型溶蚀孔洞储集层五点井网、九点井网、五点转九点井网、井位与裂缝相对位置、注入井注入速度等多种方式的水驱油开发实验,分析不同实验方案的开发指标变化规律,总结不同井网的水驱开发特征,探索最优注水开发方式。研究表明,无裂缝溶蚀孔洞型储集层,五点井网水驱波及范围小,水窜严重,采收率低,转九点井网后,采收率可较大幅度提高,但对距离较远的角井效果不明显,裂缝-溶蚀孔洞型储集层,注采井不在连通裂缝上,裂缝可以更好地沟通连通性较差的溶蚀孔洞,改善水驱开发效果;无论溶蚀孔洞型储集层有无裂缝,九点井网开发效果明显优于五点井网、五点井网转九点井网,边井开发指标优于角井,且有裂缝时更明显;九点井网水驱至高含水期,将角井转注变为交错井网后采收率可进一步提高;注入井提高注水速度,有助于提高九点井网距离较远角井的产油量,提高最终采收率,但无水采油期大幅缩短,无水采收率大幅下降。

层状砂岩油藏协同开发优势渗流通道分布规律——以非洲M盆地P油田Y油组为例

利用岩心、测井、分析化验、吸水剖面、生产动态等资料,结合地质与油藏工程识别方法,分析非洲内陆裂谷M盆地P油田主力产油层Y油组的优势渗流通道,明确层状砂岩油藏在天然水体与人工注水协同开发时优势渗流通道分布规律与分布模式。结果表明:M盆地P油田Y油组优势渗流通道优先发育于以辫状河沉积相为主的YⅥ砂组正韵律砂体底部,厚层致密泥岩隔夹层促进优势渗流通道发育并限制纵向延展。优势渗流通道多与物源呈顺河道方向平行或小角度相交;发育于层间渗透率突进系数高(>1.25)、层间渗透率变异系数较高(>0.4)、层间渗透率级差大(>4.36)砂组的高渗砂岩层。研究区建立3个层次优势渗流通道分布模式,即砂组间水体控制、砂组隔层控制和砂岩层内韵律性控制分布模式。该结果为治理层状砂岩油藏优势渗流通道、提高油藏剩余油采收率、实现稳油控水提供地质参考。

致密低渗油藏压裂井网气驱深度学习预测模型

压裂井网气驱将油藏压裂与注气井网驱油结合,是当前致密低渗油藏提高采收率有效技术之一.水力裂缝及多相流动复杂性,使得基于精细油藏数值模拟的压裂井网气驱效果预测变得困难且耗时.提出一种基于均方根传播(root mean square propagation,RMSProp)深度学习的压裂井网气驱效果预测方法.通过建立压裂直井/水平井混合井网气驱数值模拟模型,引入高斯函数定量表征压裂水平井多级裂缝分布特征.利用正交试验筛选试验样本方案,自主编程实现数值模拟结果自动提取与数据处理,建立致密低渗油藏压裂井网气驱样本数据库.基于随机森林算法,筛选油藏地质、裂缝、生产等关键参数重要性特征,通过误差逆传播(back propagation,BP)神经网络、长短期记忆单元(long short-term memory,LSTM)、双向长短期记忆单元(bi-directional long short-term memory,BiLSTM)等深度学习算法,建立日产油、地层压力和采出程度预测代理模型,通过与油藏数值模拟对比,验证模型准确性.结果表明,BiLSTM算法在预测压裂井网气驱和压裂衰竭开发时效果最好.所提出的基于RMSProp的深度学习方法有效兼顾了模型实用性与精确性,为致密低渗油藏压裂井网气驱模拟预测提供了新途径.

断块油藏开发后期井网再优化研究

江苏油田进入开发后期,在当前油价下传统的开发注采井网调整模式投入大,适配性差,制约了油田采收率的提高。为探索复杂断块油藏开发中后期经济高效的调整模式,在明确现有井网条件下水驱潜力及剩余油分布状况下,利用数模手段开展拟均质油藏、多层油藏和相控条件下井网优化技术对策研究,形成了一套复杂断块油藏开发后期注采井网再优化技术。分别在江苏油田高7、陈2区块进行了现场实践,实现了区块稳产和提高水驱采收率的目的,对江苏油田高含水后期井网调整挖潜剩余油具有一定的指导意义。