Study on Geological Genesis and Sedimentary Model of Complex Low Resistivity Reservoir in Offshore Oilfield — A Case of NgIII Formation of X Oilfield in Bohai Sea

In order to study the micro genetic mechanism and main geological controlling factors of low resistivity reservoir in NgIII formation of X oilfield in Bohai sea in China, the clay mineral composition, irreducible water saturation, salinity and conductive minerals of low resistivity reservoir were studied by using the data of core, cast thin section and analysis, and compared with normal resistivity reservoir. At the same time, the control effect of sedimentary environment on low resistivity reservoir was discussed. The results show that the additional conductivity of high bound water content and high montmorillonite content in the reservoir together leads to the significant reduction of reservoir resistivity, which is the main microscopic cause of the formation of low resistance, and is mainly controlled by the sedimentary background such as paleoclimate and sedimentary cycle. During the deposition period of NgIII formation, the paleoclimate was dry and cold, and it was at the end of the water advance of the medium-term sedimentary cycle. The hydrodynamic force of the river channel was weak, the carrying capacity of the riverbed was weak, and the river channel swayed frequently, resulting in fine lithologic particle size, high shale content and complex pore structure of the reservoir, resulting in significant reduction of reservoir resistance. The research conclusion would have strong guiding significance for the development of low resistivity reservoirs in this area.

A novel profile modification HPF-Co gel satisfied with fractured low permeability reservoirs in high temperature and high salinity

Conformance control and water plugging are a widely used EOR method in mature oilfields.However,majority of conformance control and water plugging agents are unavoidable dehydrated situation in high-temperature and high-salinity low permeability reservoirs.Consequently,a novel conformance control system HPF-Co gel,based on high-temperature stabilizer(CoCl_(2)·H_(2)O,CCH)is developed.The HPF-Co bulk gel has better performances with high temperature(120℃)and high salinity(1×10^(5)mg/L).According to Sydansk coding system,the gel strength of HPF-Co with CCH is increased to code G.The dehydration rate of HPF-Co gel is 32.0%after aging for 150 d at 120℃,showing excellent thermal stability.The rheological properties of HPF gel and HPF-Co gel are also studied.The results show that the storage modulus(G′)of HPF-Co gel is always greater than that of HPF gel.The effect of CCH on the microstructure of the gel is studied.The results show that the HPF-Co gel with CCH has a denser gel network,and the diameter of the three-dimensional network skeleton is 1.5-3.5μm.After 90 d of aging,HPF-Co gel still has a good three-dimensional structure.Infrared spectroscopy results show that CCH forms coordination bonds with N and O atoms in the gel amide group,which can suppress the vibration of cross-linked sites and improve the stability at high temperature.Fractured core plugging test determines the optimized polymer gel injection strategy and injection velocity with HPF-Co bulk gel system,plugging rate exceeding 98%.Moreover,the results of subsequent waterflooding recovery can be improved by 17%.

Pore structure differences of the extra-low permeability sandstone reservoirs and the causes of low resistivity oil layers: A case study of Block Yanwumao in the middle of Ordos Basin, NW China

The influence of pore structure difference on rock electrical characteristics of reservoir and oil reservoir was analyzed taking Triassic Chang 6 reservoir in Block Yanwumao in the middle of Ordos Basin as an example. The relationship between the pore structure difference and the low resistivity oil layer was revealed and demonstrated through core observation, lab experiments, geological research, well log interpretation and trial production etc. The results show that there were two kinds of oil layers in Chang 6 oil layer set, normal oil layer and low resistivity oil layer in the region, corresponding to two types of pore structures, pore type mono-medium and micro-fracture-pore type double-medium; the development of micro-fracture changed greatly the micro-pore structure of the reservoir, and the pore structure difference had an important influence on the rock electrical characteristics of the extra-low permeability sandstone reservoir and oil reservoir; the normal oil layers had obvious characteristics of pore-type mono-medium, and were concentrated in Chang 61, Chang 6232 and Chang 62; the low resistivity oil layers had obvious characteristics of micro-fracture-pore type double-medium, which were mainly distributed in Chang 612 and Chang 63. The mud filtrate penetrated deep into the oil layers along the micro-cracks, leading to sharp reduction of resistivity, and thus low resistivity of the oil layer; the low resistivity oil layers had better storage capacity and higher productivity than the normal oil layers.

Saturation evaluation of microporous low resistivity carbonate oil pays in Rub Al Khali Basin in the Middle East

To solve the problem that it is difficult to identify carbonate low resistivity pays(LRPs) by conventional logging methods in the Rub Al Khali Basin, the Middle East, the variation of fluid distribution and rock conductivity during displacement were analyzed by displacement resistivity experiments simulating the process of reservoir formation and production, together with the data from thin sections, mercury injection and nuclear magnetic resonance experiments. In combination with geological understandings, the genetic mechanisms of LRPs were revealed, then the saturation interpretation model was selected, the variation laws and distribution range of the model parameters were defined, and finally an updated comprehensive saturation interpretation technique for the LRPs has been proposed. In the study area, the LRPs have resistivity values of less than 1 Ω·m, similar to or even slightly lower than that of the water layers. Geological research reveals that the LRPs were developed in low-energy depositional environment and their reservoir spaces are controlled by micro-scale pore throats, with an average radius of less than 0.7 μm, so they are typical microporous LRPs. Different from LRPs of sandstone and mudstone, they have less tortuous conductive paths than conventional reservoirs, and thus lower resistivity value under the same saturation. Archie’s formula is applicable to the saturation interpretation of LRPs with a cementation index value of 1.77-1.93 and a saturation index value of 1.82-2.03 that are 0.2-0.4 lower than conventional reservoirs respectively. By using interpretation parameters determined by classification statistics of petrophysical groups(PGs), oil saturations of the LRPs were calculated at bout 30%-50%,15% higher than the results by conventional methods, and basically consistent with the data of Dean Stark, RST, oil testing and production. The 15 wells of oil testing and production proved that the coincidence rate of saturation interpretation is over 90%and the feasibility of this method has been further verified.

奥连特盆地隐蔽油藏高效滚动勘探开发方法技术及应用——以厄瓜多尔14和17区块为例

厄瓜多尔14和17区块位于奥连特盆地前渊带,主要含油层系为Napo组的M1,U和T段。现已开发油田进入高含水阶段,资源接替面临挑战。通过基于趋势面驱动的叠后地震数据连片一致性处理、时-频衰减高精度合成记录标定和解释及各向异性变速成图,精细刻画了低幅度构造,发现了一批低幅度构造油藏。采用分频迭代去噪拾取薄层弱反射系数,以其重构的叠后宽频有效信号为约束,采用相控波形非线性反演,定量预测了埋深3 000 m的2~5 m厚潮汐水道砂岩,发现了多个M1超薄层岩性油藏。依据区域水动力条件、低幅度构造油藏油-水界面趋势及油藏能量特征,发现了LU水动力油藏并滚动扩边。通过观察大量岩心薄片,发现海绿石在石英砂岩储层中呈胶结物和颗粒两种赋存状态,建立了海绿石双组构测井解释体积模型,评价并识别了UT低电阻率油藏。基于热带雨林地表和隐蔽油藏特点,按照“整体部署、分批实施、跟踪评价、及时调整”的策略,实现滚动勘探、评价和快速建产,探井和评价井成功率大于90%。

高温中低渗油藏智能纳米黑卡驱提高采收率技术

当前化学驱储量接替严重不足,亟需攻关突破高温中低渗油藏提高采收率技术。智能纳米黑卡驱油技术是当下极具前瞻性的纳米驱油技术,可大幅度提高采收率。针对河南油田高温中低渗油藏,开展高温条件下纳米黑卡静态性能评价,并通过高温岩心驱替实验评价不同渗透率条件下智能纳米黑卡驱油效果。结果表明,智能纳米黑卡具有优异的耐高温性能,分散稳定性好,能够降低油水界面张力至10^(-1)mN/m,并具有改变润湿性和快速乳化与破乳性能。同时,纳米黑卡具有高效的洗油能力,在95℃下注入0.3 PV的质量分数为0.005%的智能纳米黑卡溶液,在目标油田不同渗透率(50×10^(-3)~450×10^(-3)μm^(2))条件下可提高采收率15.8百分点~20.0百分点。因此,智能纳米黑卡驱油技术适用于河南油田高温中低渗油藏提高采收率。

基于灰色关联度分析-极限学习机的低阻油层及水淹层测井识别——以渤海P区块馆陶组为例

历经近20的开发,渤海P区块进入高含水期,馆陶组发育的大量低阻油层与水淹层在测井曲线形态上差异不明显。为了精确进行水淹层识别以及水淹层等级划分,采用了机器学习算法。首先采用灰色关联度分析,筛选低阻油层和水淹层识别的敏感参数曲线;其次构建了极限学习机水淹层识别模型,对模型进行训练,获取最优参数。将其应用于实际资料处理,结果表明,基于灰色关联度分析极限学习机的低阻油层及水淹层测井识别方法对低阻油层与水淹层的预测精度较高,符合率达89.3%,远远优于未经过灰色关联度分析筛选的预测结果,具有实际应用价值。

福山凹陷低阻油层成因分析及流体识别方法

福山油田涠洲组广泛发育低阻油层,储层低阻成因机制认识不清与储层流体准确识别是制约涠洲组高效勘探开发的主要难题。以花场、白莲、永安地区为研究对象,综合分析岩石物理实验、地层水分析化验、测井、试油等资料,围绕地层水矿化度、淡水钻井液侵入、束缚水饱和度、黏土附加导电性、含油饱和度5方面因素展开分析研究。明确不同地区低阻主控因素,深入分析不同成因机制的岩石物理和测井响应特征,针对性构建综合储集指数、侵入因子、电阻增大率等流体敏感测井评价参数。结合测井解释及生产试油情况,建立相应流体识别图版,应用于涠洲组27口井58个试油层位。结果表明,流体识别符合率由76%提高到84%,有效提高了涠洲组低阻油层流体识别准确率。

环庆区块长8低阻油层常规测井定性识别方法研究与应用

环庆区块长8发育低阻油层区,低阻油层储层流体纵向分布关系复杂,油、水重力分异弱,储层非均质性和隐蔽性强,储层流体性质判断难,准确识别低阻油层流体性质,对环庆区块下步勘探工作具有极为重要的意义。本文针对低阻油层的特点,通过开展长81低阻油层流体识别方法研究,总结建立了一套适合环庆区块低阻油层的常规测井定性识别方法,提高了测井解释精度和解释符合率。

川南长宁地区奥陶系五峰组—志留系龙马溪组页岩气储层低电阻率响应特征及主控因素

以川南长宁地区NX22井五峰组—龙马溪组低电阻率页岩气储层为例,利用岩心矿物组分、扫描电镜、总有机碳(TOC)含量、含水饱和度测试及测井曲线等资料,确立了低电阻率页岩气储层岩石体积物理模型,采用随机法构建了三维数字岩心模型,进而利用有限元数值模拟方法模拟计算各矿物组分含量、含水饱和度及有机质石墨化的电阻率响应特征,并分析其主控因素。研究结果表明:(1)长宁地区五峰组—龙马溪组低电阻率页岩气储层岩石体积物理模型由骨架(石英、长石、方解石和白云石等)、黏土矿物、黄铁矿、未石墨化有机质以及石墨化有机质、孔隙6个部分组成。(2)三维数字岩心模型的长、宽、高分别为100×100×100像素,融入了上述物理模型中的6个部分,并采用不同的颜色对导电组分进行标识,可以显示不同方向上的切片,表征低电阻率页岩气储层的组分特性。(3)黏土矿物含量、黄铁矿含量、含水饱和度以及有机质石墨化程度等4个参数增大都会造成页岩气储层的电阻率下降,而有机质的高石墨化程度(25%)和高含水饱和度(88.0%)使页岩气储层的电阻率从正常电阻率(大于15Ω·m)降到低阻甚至超低阻(小于5Ω·m),是导致研究区页岩气储层超低阻响应的2个核心因素。

长宁地区低阻页岩孔隙结构精细表征及分形研究

为明确四川盆地长宁地区龙马溪组低电阻页岩储层孔隙发育差异性,采用低阻页岩与常规页岩相对比的研究手段,开展了有机碳分析、氮气吸附实验、XRD矿物组分分析和扫描电镜等一系列实验,阐明了长宁低阻页岩储层孔隙结构及其分形特征,并明确了它们的控制因素。结果显示,长宁地区大多数低阻页岩孔隙发育程度明显差于常规页岩,其中,孔体积发育的差异主要体现在2~20 nm孔径范围内,比表面积差异则主要集中在小于1.5 nm和大于1.8 nm段。页岩储层孔隙结构随电阻率的降低有变差的趋势,对低电阻页岩储集能力影响更明显的是有机质含量和成熟度。相较于常规电阻页岩,低电阻页岩在小孔隙段具有更加复杂的孔径及孔壁发育。黏土矿物和黄铁矿对分形维数的影响在不同电阻率页岩中是一致的,而有机质对2类页岩分形维数的影响相反。有机质对分形维数的影响与过演化页岩石墨化后的有机孔变化密切相关。

南海东部M油田低损害耐温长效型完井液分析研究

针对南海东部M油田完井后8个月以上才能进行投产、完井液长时间滞留在储层中可能造成严重储层伤害的问题,调研完井液储层伤害类型以及低损害完井液种类,分析低损害完井液发展的趋势,总结选用现场应用效果好完井液体系的方法;分析完井液高温长时间静置储层潜在损伤因素,并提出有针对性地提高完井液耐温长效性能方法。通过对低损害完井液研究现状调研和完井液高温长效性能影响分析,为M油田低损害耐温长效型完井液体系的构建提供一定方向指导。

低成本低油水比低土相油基钻井液技术研制与应用

油基钻井液的应用范围较广,为降低油基钻井液成本,通过优选低成本油类基础液,开展研发新型单剂高效乳化剂,降低油水比,降低有机土加量等研究,建立了新型低成本低油水比低土相油基钻井液配方,同时对其性能进行了室内评价。实验结果表明:该钻井液油水比在65∶35~85∶15范围可调,有机土加量小于等于2.0%,密度为1.4~2.2 g/cm^(3),抗温达200℃,破乳电压大于800 V,高温高压失水量小于3 mL,油基钻井液单方成本较3号白油配制的油基钻井液降低15%以上,适用于-25℃条件,可满足辽河油区冬季施工需求。在辽河油区页岩油、致密油地层进行了应用,现场应用结果表明,低成本低油水比低土相油基钻井液性能稳定,封堵防塌性能良好,乳化稳定性良好,耐低温效果好,单方成本明显降低。研究成果有利于油基钻井液应用规模的扩大,可满足非常规油气资源低成本、安全、高效开发的技术需求。

海上低阻油藏注水开发影响因素分析

低阻油藏储层的研究一直是国内外油田开发人员亟待解决的难题之一。本文结合岩心、薄片、扫描电镜、物性及黏土矿物分析化验数据,H油田Ⅳ油组储层成岩作用可见压实作用、胶结作用和溶解作用。胶结物泥质、高岭石、菱铁矿和黄铁矿是影响该段储层物性的主要因素,主要的建设性成岩作用为溶解作用,溶解作用对改善储层的储集性能更为有利,产生的次生孔隙及裂缝一定程度上改善了本井的孔隙结构。Ⅳ油组储层分析样品含油饱和度随着地层深度增加呈现递增趋势;而含水饱和度随着地层深度增加呈现递减趋势;含油饱和度平均为7.5%;而含水饱和度平均为84%。Ⅳ油组深度2094.35~2129.39 m划分为中成岩A期,2130.00~2136.42 m划分为中成岩B期。研究成果为低阻H油田储层的高效开发提供了依据。

耐温水基聚合物压裂液制备及性能评价

针对低渗油藏水基压裂液体系进行了实验研究,通过室内性能评价测试优选了耐温水基聚合物压裂液体系配方,结合红外光谱及热重分析等微观手段对其结构、热稳定进行了分析,利用室内评价实验测定了其流变性、携砂性、返排防膨性及滤失性等相关特性,并在油田现场进行了先导性试验。压裂液主体配方(质量分数)为:0.2%~0.8%HPAM稠化剂、1.0%B3黏土稳定剂、0.1%~0.3%M2破胶剂、0.3%G6助排剂、0.2%TB破乳剂及0.02%~0.06%FS交联剂。微观测试结果表明其具备优良的热稳定性。压裂液破胶残渣远低于其他体系,对于黏土质量分数大于18%的岩屑防膨率可以达到88%。压裂液体系不需要额外降滤失剂的添加,对储层的伤害程度相较于胍胶体系压裂液可降低超过10%。

秦皇岛A油田气测录井的低阻油层识别方法

针对秦皇岛A油田储层含水高、物性差,流体性质差异大等特征,优选气测录井数据,建立低阻油层识别参数标准,形成以储层含烃指数及储层含水指数为主的识别低阻油层的技术,并在实际应用中取得较好效果,为今后该区低阻油层的识别提供了可靠的思路和方法。

低阻油层录测多元参数综合评价方法

渤海P油田馆陶组纵向上存在多套流体系统,砂体叠置关系和油水界面复杂,普遍发育低阻油层。由于低阻油层的成因和类型复杂多样,导致低阻油层具有不同的岩石物理和录、测井响应特征。依据常规测井所建立的评价方法往往会低估甚至遗漏低阻油层,尤其当低阻油层同时具有低气体含量特征时,电阻率特征和气体含量与水层难以区分。结合以岩屑为测量载体的地化录井、三维定量荧光录井等技术,优选评价参数,建立多元综合评价方法。通过验证,大大提高了研究区低阻油层的快速识别符合率,为P油田开发部署提供了有力的依据支撑。

塔里木富满油田碳酸盐岩油藏压力能利用研究

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