3D Physical Simulation of Water Flooding Characteristics of Buried Hill Reservoir with Different Fracture Systems

In order to understand the water-flooding characteristics of different fracture systems in metamorphic rock buried hill reservoirs and the mechanism of improving water-flooding development effect, a three-dimensional physical model of fractured reservoirs is established according to the similarity criterion based on the prototype of metamorphic buried hill reservoirs in JZ Oilfield in Bohai Bay Basin. Combined with the fractured reservoir characteristics of JZ Oilfield, the water displacement characteristics of the top-bottom staggered injection-production well pattern in different fracture network mode and different fracture development degree of buried hill reservoir are studied. The experimental results show that: 1) the more serious the fracture system irregularity is, the shorter the water-free oil production period is and the lower the water-free oil recovery is. After water breakthrough of production wells, the water cut rises faster, and the effect of water flooding development is worse;2) under the condition of non-uniform fracture development, the development effect of the bottom fracture undeveloped is better than that of the middle fracture undeveloped. Water injection wells are deployed in areas with relatively few fractures, while oil wells are deployed in fractured areas with higher oil recovery and better development effect.

Research and Application of Water Flooding Timing and Method for Blocky Bottom Water Fractured Buried Hill Reservoir

Oilfield A is a fractured buried hill reservoir in Bohai bay of China. In order to solve the difficult problem of water flooding timing and method in oilfield. Considering the characteristics of the buried hill fractures with stress sensitivity and strong heterogeneity, the ECLIPSE software was used in the research, and a three-dimensional injection-production numerical model for horizontal wells in buried hill reservoirs is established. According to the main research factors in water flooding, a series of water flooding schemes are designed, and the optimization of water flooding timing, oil recovery rate and water flooding mode in buried hill reservoirs were carried out. The results show that the optimum pressure level of fractured reservoir is about 70% of the original reservoir pressure. The optimal water flooding method is the conventional water flooding in the initial stage, when the water cut reaches 80%, it is converted into periodic water flooding. The oil recovery is the highest when the water injection period is 4 months. Field tests show that conventional water flooding is carried out in the initial stage of the oilfield A when the pressure is reduced to 70% of the original. Periodic water flooding is carried out when water cut is 80%. Good development results had been achieved in the 10 years since oilfield A was put into production. The average productivity of single well reached 300 m3/d in the initial stage, at present, the water cut is 60%, and the recovery degree is 18.5%, which is better than that of similar oilfields. This technology improves the water flooding effect of blocky bottom water fractured dual media reservoirs in metamorphic buried hills, and provides a reference for the development of similar reservoirs.

Experimental Study on Phase Characteristics of CO2 Injection in BZ13-2 Strong Volatile Oil Reservoir in Bohai Sea Buried Hills

BZ13-2 oil field is a deep submerged strongly volatile reservoir in Bohai Sea. This oil reservoir has the characteristics of high gas oil ratio and small difference in formation pressure and saturation point pressure. It usually adopts gas injection development to avoid crude oil degassing and fast decreasing production capacity. However, the phase characteristics and miscibility mechanism of this high-temperature and high-pressure fluid after gas injection are not clear. Therefore, it is necessary to study the feasibility of CO2 injection to improve oil recovery in near critical volatile oil reservoirs through CO2 injection experiments. In the early stage of the depletion experiment, the content of heavy components in the remaining oil increased significantly, so the depletion method is not conducive to the development of such reservoirs. With the increase of CO2 injection, the volumetric expansion coefficient of formation crude oil increases significantly, while the saturation pressure and formation crude oil viscosity remain basically unchanged. The minimum miscible pressure experiment shows that CO2 injection under formation pressure conditions can achieve multiphase miscibility. Based on experimental research results, the BZ13-2 oilfield is suitable for early gas injection development and can significantly improve recovery.

Oil Source and Entrapment Epoch of the Ordovician Oil Reservoir in the Kongxi Burial-Hill Zone, Huanghua Depression, North China

An oil flow obtained from the Middle Ordovician Fengfeng Formation carbonate reservoir in the well KG-3, Kongxi burial-hill zone in 1993 marked a breakthrough in petroleum exploration of the high-mature Lower Palaeozoic strata, North China. Both the Lower member of the Fengfeng Formation and the Second Member of the Upper Majiagou Formation in the Middle Ordovician are supposed to be the main source beds. Oil generation peaks range from 1.0% to 1.6% in Ro, showing a “lag effect” of oil generation in high-mature carbonate source rocks under multicyclic tectonic movement conditions. The Kongxi burial-hill zone adjoins a potential Ordovician source kitchen. The KG-3 Ordovician burial-hill reservoir has undergone two oil filling events, i.e., an early event in the Late Carboniferous-Permian and a more significant late event in the early Eogene.

Formation of the primary petroleum reservoir in Wumaying inner buried-hill of Huanghua Depression, Bohai Bay Basin, China

Well Yinggu 1 drilled on the tectonic belt of the Wumaying buried-hill in Huanghua Depression obtained non-H2S high-yield oil and gas flow from the Permian Lower Shihezi Formation sandstone. The oil and gas are derived from the Upper Paleozoic coal source rock, the petroleum reservoir is an inner buried-hill primary oil and gas accumulation, showing a good prospect of the Paleozoic inner buried-hill primary reservoir exploration. The formation and accumulation of the primary petroleum reservoir in the Wumaying inner buried-hill are discussed by studying the primary source conditions, the inner buried-hill reservoir-cap combinations and the hydrocarbon accumulation period. The primary petroleum reservoir has three preponderant characteristics of accumulation: secondary large-scale gas generation of coal source rock, multi reservoir-cap combinations and mainly late hydrocarbon charging, which formed the compound hydrocarbon accumulation of the above-source sandstone and under-source carbonate rock in the Paleozoic inner buried-hill. Along with the Mesozoic and Cenozoic tectonic activities, the formation of the primary reservoir in Wumaying inner buried-hill is characterized by "mixed oil and gas charge in local parts in early stage, adjustment accumulation due to structural high migration in middle stage, and large-scale natural gas charge and compound accumulation in late stage".

Study of the Law about Water-Cut Variation for the Fractured Metamorphic Reservoir of Buried Hill with Bottom Water

Aiming at the complex flowing environment including the buried hill of Metamorphite, the active bottom water and the fracture at Budate Reservoir within Beir Depression of the Hailar Basin, combining the laboratory studies and based on analysis of its drive mechanism, field wells’ parameters were used to analyze the effects of different conditions of the fractured metamorphic reservoir with bottom water on its law of wa-ter-cut variation and the waterflooding efficiency. The results show that for the Budate buried hill reservoir with bottom water, the gravity should be taken into consideration to determine reasonable perforation ratio and production pressure difference. And because of the acid sensitivity of the buried hill reservoir, application of proper clay stabilizer will enhance the field oil recovery to a satisfactory extent.

Effect of Faulting on Ordovician Carbonate Buried-Hill Reservoir Beds in Hetianhe Gas Field, Tarim Basin

Ordovician carbonate buried-hill reservoir beds in the Hetianhe （和田河） gas field, located in the Mazhatage （玛扎塔塔） structural belt on the southern margin of the Bachu （巴楚） faulted uplift, southwestern Tarim basin, were studied. Based on field survey, core and slice observation, the general characteristics of carbonate buried-hill reservoir beds and specifically Ordovician carbonate buried-hill reservoir beds in the Hetianhe gas field were discussed. The karst zone of the reservoir beds in Hetianhe gas field was divided into superficial karst zone, vertical infiltration karst zone, lower subsurface flow karst zone, and deep sluggish flow zone from top to bottom. The effects of faulting on Ordovician carbonate buried-hill reservoir beds in the Hetianhe gas field were obvious. The faulting intensified the karstification and increased the depth of denudation. Faulting and subsequent fracture growth modified the reservoir beds and improved the physical property and quality of the reservoir beds. Moreover, faulting enhanced the development of the dissolution holes and fractures and increased the thickness of the effective reservoir beds. Meanwhile, faulting made the high porosity-permeability carbonate belts, which created conditions for the hydrocarbon accumulation, develop near the fault zone.

珠江口盆地潜山储层地质力学及压裂参数优化研究

珠江口盆地珠一坳陷惠州27-1井区作为潜山油气储层,压裂层段厚度大、层数多、非均质性强、压裂改造难度大,对于人工裂缝的在潜山储层中的拓展延伸规律认识困难。针对此问题,首先建立动态参数测井解释模型,并与静态岩石力学数据协同校正,建立一维岩石力学剖面;结合深部成岩理论,建立三维地质力学模型,真实模拟研究区块成岩环境;最后基于三维地质力学模型,研究排量、液量、砂比、前置液占比、射孔层位厚度等参数对裂缝纵向和平面延伸规律的影响,优化压裂设计。结果表明:惠州27-1区块,杨氏模量平均值为45.47 GPa,最大水平主应力平均值为100.91 MPa,最小水平主应力平均值为80.98 MPa,泊松比平均值为0.30。排量6~7 m^(3)/min、液量600~700 m^(3)、砂比10%~15%、前置液比例50%~60%、射孔厚度8~11 m为最优施工参数,为现场施工提供指导意见。

乍得基岩注气井膨胀管悬挂二次完井技术

乍得油田潜山基岩油藏面临油井低压低产的问题,需要开展注气补充地层能量以提高油井产量,但裸眼开发井转投注气井后,出现上部层系出砂填埋储层的问题。为此,下入膨胀管悬挂器结合裸眼封隔器等组成的下部完井管柱,在乍得BX20井进行二次完井技术先导试验。现场试验结果表明:设计的二次完井管柱一次入井到位,整个作业周期为10 d,较传统二次完井平均施工作业周期减少7 d,节省修井作业费用超20万美元;该井完井后能够有效地封固和保护套管免受注气高压的破坏,有效解决裸眼注气井井筒完整性问题,试注气压力达到20 MPa,注气量达到2000 m^(3)/h。该完井工艺的成功实施解决了乍得油田注气井完井问题,对同类油田的开发具有先导示范作用。

海上低渗潜山储层缝网压裂可行性评价方法

海上低渗潜山储层开发难度大、开发经济界限高,开发效果受压裂改造体积影响很大。采用地质工程一体化方法,在地质模型和力学模型的基础上,研究认为M潜山储层可以形成复杂人工缝网。为进一步提高裂缝复杂程度,建立了以储隔层应力差、隔层厚度、逼近角、水平应力差异系数为参数的缝网评价方法,并给出了最优值,认为储隔层应力差小于4MPa或隔层厚度小于7m时,可以实现人工裂缝穿层,实现裂缝复杂化。该研究对论证海上低渗潜山储层压裂能否形成复杂缝网,提高单井初产和累产具有很好的指导作用。

基于井震融合的碳酸盐岩古岩溶残丘储层刻画方法

北大港构造带千米桥奥陶系潜山顶部发育的碳酸盐岩古岩溶残丘作为一种重要的古地貌和油气储集单元,具备良好的成藏条件,有效地刻画古岩溶残丘储层对于残丘储层的油气运移聚集分析及勘探开发有着非常重要的意义。本文首先应用地震印模法对千米桥奥陶系潜山风化壳岩溶古地貌进行精细刻画,揭示该区发育5个岩溶残丘,4个岩溶沟谷,表现为山上有山的特征;同时井震融合分析认为潜山风化壳储层大多分布在风化壳面以下0~200 m范围内,主潜山各区块风化壳残余厚度差别较大,岩溶残丘之上构造高点残余厚度大。通过成像测井和常规测井曲线上异常显示识别残丘风化壳内幕发育的岩溶洞穴,主要有大溶洞和中小溶蚀孔洞两种。应用提频地震体开展正演模拟,明确优势缝洞体储层的地震反射特征,结合张量方向场裂缝定量预测技术,能精细地预测碳酸盐岩缝洞复合体储层,以指导残丘风化壳储层油气潜力目标区的评价开发。

双封隔器在渤海油田潜山地层取样的应用

渤海油田潜山地层油气藏油质好、储量大,但由于埋藏深、岩性复杂、储集空间多样,勘探开发过程中储层有效性评价及流体性质评价难度大。钻井中途油气层测试仪(EFDT)是中海油田服务股份有限公司自研的一种模块化、泵抽式电缆地层测试仪,其双封隔器取样技术能够在非均质性强的地层成功坐封和取样,准确判断潜山地层是否存在油气,为正确认识储层特征和流体类型提供可靠依据,为确定潜山成藏模式的勘探决策提供重要参考。

济阳坳陷孤西潜山带构造演化及其对油气差异富集的控制

为明确济阳坳陷孤西潜山带油气差异富集特征,指导下步油气勘探方向优选,综合利用钻井及地震资料,在潜山地质特征分析的基础上,对潜山构造演化及其对油气差异富集的控制作用进行了研究。结果表明,印支期以来,孤西潜山带经历了晚三叠世挤压抬升剥蚀、早—中侏罗世弱挤压到截凸填凹、晚侏罗世挤压抬升剥蚀、早白垩世左行走滑拉张、晚白垩世挤压抬升剥蚀、古近纪右行走滑拉张高位潜山剥蚀等4期挤压、2期拉张、2期走滑、5期剥蚀的演化过程,并于新近纪整体沉降定型,在孤西潜山带形成高位潜山和低位潜山2类潜山,整体具有“NW向断层控带、NE(EW)向断层控山、垒堑相间”的构造格局。多期构造活动作用的叠加,导致2类潜山在源储对接关系、油藏类型和油气富集特征上具有明显差异,高位潜山斜坡带上古生界和中生界地层油藏最为富集,低位潜山各层系均可成藏,且以古生界构造油藏最为富集,同种类型的潜山由于成藏要素配置关系的不同,其油气富集特征也有所差异。埕中、埕东、孤岛等高位潜山斜坡带地层油藏,孤北、垦利等低位潜山下古生界风化壳油藏及内幕构造油藏和上古生界及中生界构造油藏是下步重点勘探目标。

琼东南盆地松南低凸起YA区花岗岩潜山风化壳储层特征及发育控制因素

为揭示琼东南盆地松南低凸起YA区花岗岩潜山型油气藏发育机理与成藏规模,运用岩心、物性、元素、磷灰石裂变径迹分析测试资料及测井-地震解释,研究了区内花岗岩潜山风化壳储层特征及发育控制因素、风化壳发育史及残余厚度分布。研究表明:YA区花岗岩系形成于印支期早三叠世,盆地基底在古新世—中新世经历多次构造抬升及沉降,风化壳分两期形成并得以保存,区内热带季风型古气候促进了花岗岩系化学风化作用。区域构造演化、古气候及岩石类型是控制区内古潜山风化壳发育的主要因素。风化壳发育程度存在显著差异性,区内古构造高点处的花岗岩风化壳残余厚度大。YA区花岗岩具有显著的钙碱性-碱性、准铝质-过铝质特征,属于易风化岩石类型。区内风化壳垂向上可分为残积-坡积层、砂化层、风化裂缝层、水平潜流层和基岩层。风化裂缝层是最有利储层,平均孔隙度为11.46%,平均渗透率为5.98×10^(-3)μm^(2),物性随深度增加逐渐变差。花岗岩风化壳在测井曲线上呈现高自然伽马值、高电阻率、低密度和高声波时差等特征,测井指标变化趋势与物性变化趋势基本吻合。地震波反射属性高异常程度与风化壳裂缝发育程度基本呈正相关规律。

琼东南盆地基底花岗岩风化—构造联合控储机制

含油气盆地的潜山基岩油气藏是一个特殊的勘探领域。近年来,在南海琼东南盆地的中生界花岗岩潜山中获得多个油气勘探发现,昭示着该领域良好的勘探前景。盆地中部的松南潜山群资料最为丰富,多口探井钻遇基底花岗岩储层。裂缝作用作为致密结晶基岩成储的先决改造条件,在基岩潜山储层研究中至关重要,但是对该区域花岗岩潜山的裂缝发育特征以及构造应力缺乏研究,严重制约了基岩潜山油气藏的勘探进展。基于松南低凸起5口钻井的岩心和壁心观察、显微薄片鉴定、测井和地震资料解释,揭示了松南低凸起潜山的多期裂缝的切割关系、开度、形态和走向等发育特征,并探讨了形成两组构造缝的构造应力。研究结果表明,构造缝和沿裂缝的溶蚀孔洞是基岩花岗岩的主要储集空间;构造缝分为北东向和北西向两组,印支期古特提斯洋关闭形成的北东向挤压是北西向断裂以及北东向构造缝的构造动力,燕山期来自东南侧的西太平洋俯冲相关的构造挤压则促成了北东向断裂以及北西向构造缝的发育;花岗岩中高密度裂缝的发育为暴露期大气水下渗溶蚀提供了网状通道,并形成了由砂砾岩带、风化裂缝带、内幕裂缝带组成的风化壳储层三层结构;新生代早期裂谷盆地形成过程中的伸展拆离背景对先存网状裂缝体系具有活化作用,是裂缝松弛开启从而提高储集空间的重要因素。

珠江口盆地深水区古潜山强风化淋滤带储层分布规律及其主控因素

珠江口盆地深水区古潜山钻井资料极少,严重制约了古潜山有利储层的预测和天然气勘探进程。为此,以该盆地白云凹陷东部古潜山为例,综合利用井资料和高精度三维地震数据,对该古潜山的强风化淋滤带储层分布进行了重点解剖,在明确其储层微观和测井响应特征的基础上,通过井—震标定,依托高精度三维地震数据揭示了古潜山强风化淋滤带储层的分布规律,并探讨其主控因素。研究结果表明:①古潜山强风化淋滤带储层具有低密度的测井响应特征,其内部斜长石和云母等矿物严重蚀变,斜长石内的裂缝因强烈的溶蚀改造变宽和不同程度弯曲;②古潜山强风化淋滤带储层在地震剖面上呈空白反射,且具有明显的垂向非均质性,分布在古潜山现今地貌西部的高点和东部的斜坡上;③在始新世早期及其之前,该区古潜山均位于古地貌高点,长期的强风化淋滤作用有效地促进了强风化淋滤带的形成,中—晚始新世,东强西弱的差异伸展导致西部强风化淋滤带仍处于地貌高点,而东部则由于断块旋转和岩浆底侵导致的抬升转变为现今的斜坡部位。结论认为,大气降水沿古潜山内幕断裂的差异渗流导致了差异风化,造就了古潜山强风化淋滤带储层的垂向非均质性;古地貌是主控古潜山强风化淋滤带储层东西差异分布的主要因素。

Z4变质岩潜山油藏裂缝特征及地震预测

裂缝地震预测是裂缝型油藏评价的基础。变质岩潜山油藏具有裂缝类型多、不同部位裂缝发育程度差异大、裂缝非均质性强、预测难度大等特征,针对Z4变质岩潜山油藏开展裂缝特征及地震预测研究。Z4潜山油藏裂缝发育程度具有成层性,可分为4段:顶部风化-半充填裂缝段、上部网状裂缝发育段(发育程度高)、中部低角度裂缝发育段(发育程度中等)和下部高角度裂缝发育段(发育程度低)。提出了综合多尺度通用谱分解、倾角导向的本征值相干处理和迭代蚂蚁体分析的综合裂缝预测技术。将岩心上裂缝产状及发育程度与地震预测结果进行对比,结果显示吻合度较高,提出的多方法综合裂缝地震预测具有较高的准确性。

渤中19-6潜山裂缝储层高承压可解堵防漏堵漏体系优化与应用

渤中19-6等区块潜山储层裂缝发育,导致钻井过程中漏失频发。潜山层段顶部存在风化壳,裂缝极其发育,且多为微小—小裂缝,严重影响了钻井时效。通过分析渤中19-6等区块钻井液漏失密度、裂缝宽度和漏失工况,揭示了潜山裂缝漏失特征和机理;通过形貌分析及酸溶率、抗温性和承压能力测试,优选出GYD合金作为架桥材料、水镁石纤维作为铺网捕获的纤维材料、MDF粉末和PF-EZCARB粉末作为填充粉末,构建了潜山裂缝性高承压可解堵堵漏体系。室内测试评价结果表明,所优选的堵漏材料复配协同,对开度1.0 mm×0.5 mm楔形长裂缝封堵承压达10 MPa,强化了防漏堵漏体系的网络结构,提高了承压堵漏性能,酸溶解堵率为72.5%,实现了“堵而不死,易于解堵”,最大限度地满足了潜山储层的堵漏要求。本文构建的潜山裂缝性高承压可解堵堵漏体系已在渤中19-6区块深层探井中取得成功应用,可为渤海潜山储层安全高效钻井提供技术支持。

机械比能模型在潜山储集层评价中的改进与应用

渤海油田潜山储层岩性多样、地质条件复杂、非均质性强,传统机械比能模型对潜山储层储集性能响应的敏感性较差,难以高效指导勘探作业决策。为此,基于微钻头钻进实验和滑动窗口理论,分析了机械比能对工程参数的响应规律,构建了机械比能标准化模型和改进型机械比能模型,形成了潜山储层储集性能解释标准。结果表明:渤海油田潜山储层钻压系数为0.309~0.605;改进型机械比能小于0.80时为Ⅰ、Ⅱ类储层,改进型机械比能为0.80~1.15时为Ⅲ类储层,改进型机械比能大于1.15时为致密储层。研究成果在渤海油田36口潜山探井作业中进行了应用,储层储集性能解释符合率平均值为80.2%。该研究可为中途测试、完钻等勘探作业决策提供技术支持,具有很好的借鉴意义。

潜山储层定量预测技术研究与应用——以珠江口盆地惠州凹陷H潜山为例

惠州凹陷古潜山埋藏深、构造复杂、储层非均质性强,“甜点”储层及潜山内幕复杂断裂体系表征难度大。从潜山储层成因机理出发,基于潜山风化裂缝带、内幕裂缝带储层主控因素的分析,形成了潜山储层定量预测关键技术。针对风化裂缝带,基于Keys-Xu岩石物理模型,构建新的弹性参数,提高了“甜点”储层的识别能力。针对内幕裂缝带,利用蚂蚁体技术提取优势方位断裂信息,再将提取出的不同方位优势断裂信息进行等权融合,实现对潜山内幕断裂的精细刻画。以上技术有效指导了惠州凹陷H潜山储层的勘探评价,为珠江口盆地潜山勘探提供了宝贵经验。