Hydrocarbon gas huff-n-puff optimization of multiple horizontal wells with complex fracture networks in the M unconventional reservoir

The oil production of the multi-fractured horizontal wells(MFHWs) declines quickly in unconventional oil reservoirs due to the fast depletion of natural energy. Gas injection has been acknowledged as an effective method to improve oil recovery factor from unconventional oil reservoirs. Hydrocarbon gas huff-n-puff becomes preferable when the CO_(2) source is limited. However, the impact of complex fracture networks and well interference on the EOR performance of multiple MFHWs is still unclear. The optimal gas huff-n-puff parameters are significant for enhancing oil recovery. This work aims to optimize the hydrocarbon gas injection and production parameters for multiple MFHWs with complex fracture networks in unconventional oil reservoirs. Firstly, the numerical model based on unstructured grids is developed to characterize the complex fracture networks and capture the dynamic fracture features.Secondly, the PVT phase behavior simulation was carried out to provide the fluid model for numerical simulation. Thirdly, the optimal parameters for hydrocarbon gas huff-n-puff were obtained. Finally, the dominant factors of hydrocarbon gas huff-n-puff under complex fracture networks are obtained by fuzzy mathematical method. Results reveal that the current pressure of hydrocarbon gas injection can achieve miscible displacement. The optimal injection and production parameters are obtained by single-factor analysis to analyze the effect of individual parameter. Gas injection time is the dominant factor of hydrocarbon gas huff-n-puff in unconventional oil reservoirs with complex fracture networks. This work can offer engineers guidance for hydrocarbon gas huff-n-puff of multiple MFHWs considering the complex fracture networks.

Exploration Technology for Complex Sandstone Reservoirs in the Developed Area of Shengli Oilfield

Jiyang depression, which is the main oil productive area of Shengli oil field, is located at the southeast part of the Bohai Bay Basin and is a terrestrial lacustrine rift subsidence basin formed in the late Mesozoic with fully developed fault system. The main hydrocarbon productive formations of this depression are the terrestrial clastic rocks of the Tertiary, which are of strong lateral variation. The complex fault reservoirs and subtle lithological reservoirs distributed extensively and are becoming the main exploration targets in recent years. The exploration and development practice in these years has formed the exploration technologies, mainly including detailed study and description of low grade faults, delineation of microstructures, facies constrained formation description and prediction and low resistivity oil bearing formation’s identification. These exploration technologies have resulted in remarkable effectiveness on the reserve and oil production increments.

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%.

Compositional heterogeneity of crude oil and its origin in the Linnan subsag,Linyi County,Shandong Province

The Linnan subsag is the main oil producer of the Linpan oil zone. Based on the oil group composition,gas chromatography data and biomarker analysis,it was indicated that crude oils from different oilfields varied greatly in group composition and showed obvious heterogeneities in the aspects of precursor type,crude oil maturity and hydrocarbon depositional environment. According to the characteristics of source rocks,three oil populations can be distinguished,i.e.,the southern,northern and transitional oil populations. Furthermore,on the basis of post-reservoir reworking processes,the medium conditions of hydrocarbon-generating environment and differences in maturity,six oil families and twelve sub-families were distinquished. An integrated study suggested that the fac-tors leading to such heterogeneities in crude oil composition mainly include different source rocks,multi-stage oil/gas charging,geo-chromatographic effects during oil/gas migration,reservoir heterogeneities and various post-reservoir secondary alterations.

Characterization of complex hydraulic fractures in Eagle Ford shale oil development through embedded discrete fracture modeling

This study extends an integrated field characterization in Eagle Ford by optimizing the numerical reservoir simulation of highly representative complex fractured systems through embedded discrete fracture modeling(EDFM). The bottom-hole flowing pressure was history-matched and the field production was forecasted after screening complex fracture scenarios with more than 100 000 fracture planes based on their propped-type. This work provided a greater understanding of the impact of complex-fractures proppant efficiency on the production. After compaction tables were included for each propped-type fracture group, the estimated pressure depletion showed that the effective drainage area can be smaller than the complex fracture network if modeled and screened by the EDFM method rather than unstructured gridding technique. The essential novel value of this work is the capability to couple EDFM with third-party fracture propagation simulation automatically, considering proppant intensity variation along the complex fractured systems. Thus, this work is pioneer to model complex fracture propagation and well interference accurately from fracture diagnostics and pseudo 3 D fracture propagation outcomes for multiple full wellbores to capture well completion effectiveness after myriads of sharper field simulation cases with EDFM.

Origin of dolomites in the Permian dolomitic reservoirs of Fengcheng Formation in Mahu Sag,Junggar Basin, NW China

Origin of authigenic dolomites in the dolomitic reservoir of the Permian Fengcheng Formation in the Mahu Sag of Junggar Basin is unclear.Occurrence and genetic evolution of the authigenic dolomites in dolomitic rock reservoir of the Fengcheng Formation in the Mahu Sag were analyzed by polarized and fluorescence thin sections,scanning electron microscope(SEM),electron microprobe(EMP),C,O and Sr isotopes analysis,and other techniques.(1)Dolomites were mainly precipitated in three stages:penecontemporaneous-shallow burial stage(early stage of the Middle Permian),middle burial stage(middle stage of the Middle Permian),and middle-deep burial stage,with the former two stages in dominance.(2)Dolomitization fluid was high-salinity brine originating from alkaline lake.In the penecontemporaneous-shallow burial stage,Mg^(2+)was mainly supplied by alkaline-lake fluid and devitrification of volcanic glass.In the middle burial stage,Mg^(2+)mainly came from the transformation of clay minerals,devitrification of volcanic glass and dissolution of aluminosilicates such as feldspar.(3)Regular changes of Mg,Mn,Fe,Sr,Si and other elements during the growth of dolomite were mainly related to the alkaline-lake fluid,and to different influences of devitrification and diagenetic alteration of volcanic materials during the burial.(4)In the penecontemporaneous stage,induced by alkaline-lake microorganisms,the micritic-microcrystalline dolomites were formed by primary precipitation,replacement of aragonite and high-Mg calcite,and other processes;in the shallow burial stage,the silt-sized dolomites were formed by continuous growth of micritic-microcrystalline dolomite and replacement of calcites,tuffs and other substances;in the middle burial stage,the dolomites,mainly silt-and fine-sized,were formed by replacement of volcanic materials.The research results are referential for investigating the formation mechanism and distribution patterns of tight dolomitic reservoirs in the Mahu Sag and other similar oil and gas bearing areas.

近废弃油藏延长生命周期开发调整技术

针对近废弃油藏特高含水、优势通道发育、剩余油高度分散、非均质性强等主要矛盾,以双河油田北块Ⅱ(2油组)4—5层系为例,采用油藏精细地质建模、数值模拟方法和微观驱替实验方法,表征了聚合物驱后油藏剩余油分布特征。聚合物驱后宏观剩余油平面上注采非主流线、主流线弱势区及注采井距较大的边部区域剩余油饱和度较高,纵向上正韵律顶部剩余油富集;微观剩余油以半束缚态为主,依据剩余油分布特征提出了非均相复合驱变流线井网加密调整技术思路。通过井网变流线加密调整,形成交错式行列井网模式,流线方向转变30°以上,流线转向率达80%,促使剩余油有效动用。数值模拟预测该技术可提高采收率10.96%,新增可采储量70.61×10^(4) t,延长生命周期15 a,为聚合物驱后油藏大幅度提高采收率提供新的技术方法。

胜利油田稠油油藏开发技术进展

针对胜利油田不同类型稠油油藏的地质特点及开发矛盾,形成了一套较为完善的稠油油藏开发技术系列,并取得了显著的开发效果。从各项技术的理论基础和矿场应用2个方面,总结了不同类型稠油油藏开发技术进展。对于高轮次吞吐后的稠油油藏,基于非达西渗流理论,形成了井网加密技术;对于敏感性稠油油藏,形成了近热远防理论,降低了水敏对开发的不利影响;对于特超稠油油藏,通过HDCS技术的协同降黏、膨胀增能作用,解决了“注不进、采不出”的开发难题;对于低效水驱稠油油藏,通过转蒸汽驱,达到加密角井流线、水井流线逆向的目的,从而提高该类油藏的采收率;对于深层稠油油藏,以气热协同保热强热、热剂协同接替助驱、气剂协同均衡热前缘的协同增效作用机理认识为基础,形成了多元热复合驱油理论,实现了深层稠油的有效动用;对于薄层稠油油藏,通过热+水平井复合开发模式,提高了油藏的吸汽能力和动用范围;对于浅薄层超稠油油藏,通过HDNS技术增能降黏扩波及,实现了该类油藏的高效开发。胜利油田稠油油藏开发技术系列的应用,为胜利油田稠油效益开发、绿色开发提供了技术支撑。

适合致密油藏的超临界CO_(2)-气溶性表面活性剂复合吞吐技术

为了进一步提高致密油储层超临界CO_(2)吞吐的开发效果,探索适合致密油藏的超临界CO_(2)-气溶性表面活性剂复合吞吐技术,通过原油黏度实验、油气界面张力实验、最小混相压力实验、原油膨胀系数实验以及超临界CO_(2)-气溶性表面活性剂复合吞吐模拟实验,评价了不同类型气溶性表面活性剂的性能及其对吞吐采收率的影响。结果表明:气溶性表面活性剂GRS⁃1的综合性能更加突出,随着气溶性表面活性剂质量分数的不断增大,原油黏度、油气界面张力和最小混相压力均呈现出逐渐降低的趋势,而原油体积膨胀系数则逐渐增大,并且岩心的吞吐采收率和入口端压力也呈现出逐渐增大的趋势;随着混合流体注入量的增加以及闷井时间的延长,岩心吞吐采收率和入口端压力均逐渐增大,并且岩心的渗透率越大,吞吐采收率就越高;超临界CO_(2)-气溶性表面活性剂复合吞吐的最佳实验参数为气溶性表面活性剂GRS⁃1的质量分数0.6%、混合流体注入量0.5 PV、闷井时间3 h、吞吐轮次3次。该复合吞吐技术能够显著提高致密油藏的采收率,对高效开发致密油藏具有指导意义。

复杂断块油藏井震联合建模数模一体化技术研究

【目的】为解决复杂断块油藏面临的油藏构造碎小、低序级断层数量多、准确识别难度大和油藏描述效率低等问题。【方法】充分应用地震资料、测井数据等储层信息,开展井震联合建模数模一体化技术研究,利用三维地震资料,结合现场生产动态响应情况开展断层精细解释、断裂系统精细刻画,准确落实低序级断层发育及组合方式,在精细地层对比研究的基础上,建立三维地质模型,利用数值模拟与模型互检,迭代修正更新模型,尽可能保证模型精准,以便厘清剩余油分布规律,指导后期开发。【结果】该技术在胜利油田复杂断块区D块、L块等多个区块先后进行了应用,结果显示,断点吻合率均达到100%,数模含水拟合率达到90%以上。【结论】该技术能够实现复杂断块构造的精细描述,对特高含水期自然断块剩余油潜力认识、提高老区采收率具有重要意义,对其他同类型油藏的剩余油挖潜具有指导意义和良好的推广价值。

复杂压力系统薄互层致密油藏水平井钻井关键技术

南堡凹陷高柳区块沙三3段V油组属于典型的砂泥薄互层致密油藏,因多年压裂注水开发导致地层压力系统复杂、人工缝网分布密集,水平井钻井过程中井漏、油水侵与井壁垮塌复杂情况同时存在、矛盾突出。结合高柳区块地层特征阐述了水平井安全钻井技术难点,明确了钻井液漏失、井壁垮塌原因,优选纳微米级乳化防塌剂、石墨微球与微米级柔性封堵剂、超细钙构建了封堵承压井壁稳定油基钻井液体系,该体系有效降低滤液对泥岩地层的侵入,对泥岩强度保持能力提高5倍以上,使中高渗砂岩封堵承压能力达到18 MPa;针对油基钻井液漏失问题提出了油基桥接堵漏技术与油基固化堵漏技术。现场试验解决了高柳区块复杂压力系统致密油藏水平井安全钻井难题,十余口应用井无井壁垮塌情况发生,漏失井堵漏后漏失层承压能力提高5.4 MPa,满足后续钻井施工要求。

砾岩油藏二元复合驱注入体系优化研究

新疆克拉玛依砾岩油藏经过几十年的水驱开发,面临剩余油高度分散、采油速度低等问题,选取聚合物部分水解聚丙烯酰胺(HPAM)和低张力表面活性剂PS-30及强乳化表面活性剂OP-10组合形成不同的二元复合体系,利用长砂管模型研究不同渗透率、不同驱替方式及不同注入量下复合驱体系在砾岩油藏的应用界限及提高采收率极限。实验结果表明:二元复合驱能够有效驱替残余油、扩大波及体积,显著提高砾岩油藏采收率。聚合物浓度为1000 mg/L,相对分子质量为7×10^(6)的聚合物在渗透率3×10^(-2)μm^(2)时复合驱采收率为66.31%,较水驱提高21.85个百分点。强乳化复合体系提高采收率效果好于低张力复合体系。复合体系注入量越高,提高采收率越大,但提高采收率幅度并非线性变化,复合体系注入量达到3.5 PV以后,复合体系提高采收率值逐渐趋于稳定,在注入10 PV后,复合驱体系最高提高采收率幅度达到40.38个百分点。

鄂尔多斯盆地页岩油水平井扇形井网地质工程一体化开发实践

多平台大范围规模布井是非常规资源高效动用的关键。由于黄土塬地貌特征和林缘区、水源区的限制,鄂尔多斯盆地庆城三叠系延长组长7页岩油的布井模式存在局限性。为进一步实现平台动用储量最大化,创新提出扇形井网布井方式。文章采用地质工程一体化方法,探究扇形井网不同布井方位对裂缝扩展和产能的影响,对扇形井网开展相应的裂缝间距和压裂次序优化,同时结合实际案例分析扇形井网下的压裂特征并对产能效果进行对比。研究结果表明,斜交水平井(水平段井轨迹与最小水平主应力夹角大于或等于15°)与常规水平井(水平段井轨迹与最小水平主应力夹角小于15°)相比,预测产能随偏转角度(布井方向与最小水平主应力方向的夹角)的增大而减小,当偏转角度大于45°时,产能差异进一步放大,同时模拟结果下的经济评价情况表明,当偏转角度为90°时,经济可行性最差,不建议布井;扇形井网模式下通过扩大裂缝间距和采用“从外到内”的压裂次序可以提高预测产能;斜交水平井裂缝首先沿垂直井筒方向延伸且震级较大,但在远场尺度下最大水平主应力方向仍然是裂缝扩展的主导因素;与常规水平井相比,斜交水平井储层改造体积小,但裂缝复杂程度高,缝网改造更充分;对比实际投产效果来看,斜交水平井累计产量低于常规水平井,但液面高度高且目前日产油量接近,存在一定开发潜力。

复杂油气藏储层预测方法综述

随着油气勘探不断深入,传统储层逐渐减少,使得岩溶储层、裂缝储层、页岩储层、煤层气等复杂储层成为重要勘探目标。这些复杂储层往往具有多种非均质性特征,包括岩性变化、孔隙裂缝、多介质分布等,导致储层的空间分布和特性变化极为复杂,深入研究复杂储层预测方法具有重要的理论和应用价值。本文重点分析了岩溶储层、裂缝储层、页岩储层和煤层气储层等复杂油气藏的形成机理和勘探难点;系统总结了相关研究的发展情况和应用方法,为相关领域研究人员提供了有益的参考。指出未来复杂储层预测的发展将集中在多源信息融合、数据集成、高分辨率地震技术和人工智能等方向,这些技术的应用有望提高预测精度和效率,为复杂气藏的勘探和开发提供更为全面和有效的支持。

非常规油气藏不规则复杂裂缝表征方法

非常规油气资源储量大,开发难度高。储层压裂改造是非常规油气资源开发的关键技术手段。天然裂缝和压裂裂缝具有不规则性和复杂性。针对现有裂缝表征方法难以准确刻画裂缝真实形状和宽度变化等不规则特性这一问题,提出了基于非结构PEBI网格的不规则复杂裂缝表征方法。首先,建立基于PEBI网格的天然裂缝表征流程,实现对任意区域或限定区域天然裂缝的准确表征;其次,建立基于Delaunay三角形网格和PEBI网格的压裂裂缝表征及优化方法,分析网格尺寸及优化次数对裂缝表征精度的影响;第三,建立基于非结构网格的非平面裂缝表征方法,实现对弯曲裂缝的刻画和表征,裂缝形态和分布与实际情况更相符;第四,提出非均匀裂缝宽度表征方法,实现对变宽度即同一条裂缝宽度和导流能力不均匀分布裂缝的精细表征;第五,在全区域和限定区域内,实现耦合不规则压裂裂缝和不规则天然裂缝的复杂缝网表征。针对大规模天然裂缝与压裂裂缝相交、裂缝宽度非均匀分布、非平面裂缝等复杂条件下的裂缝网络表征,通过调整网格优化次数,能够提高缝网表征质量。利用PEBI网格能够灵活准确逼近裂缝复杂边界条件的优势,实现快速、准确地显示处理大量不规则天然裂缝和压裂裂缝。形成的不规则复杂裂缝表征方法,有助于提高非常规油气藏裂缝网络的表征精度和数值模拟计算准确性。

鄂尔多斯盆地陕北斜坡储层岩石学特征及油气勘探指示——以油房庄北部长6油层组为例

为明确鄂尔多斯盆地油房庄北部有利相带和优质储层发育区,推进鄂尔多斯盆地探明储量的进一步扩大,通过岩心薄片观察、岩石矿物成分分析测定等多种手段开展油房庄北部重点层段长6油层组储层的碎屑颗粒组成、填隙物组分等关键特征要素研究,并在此基础上分析长6油层组储层的重、轻矿物分布规律,进而探讨物源的指示意义以及油气耦合关系,以期补充该地区关于储层岩石学和物源分析的科研成果.经分析,长6砂岩储层主要为长石砂岩,并见少量岩屑长石砂岩;填隙物的类型多、含量变化大,主要包括黏土胶结物、碳酸盐类胶结物、硅质胶结物等;粒级分布以细砂为主,颗粒磨圆为次棱角状,颗粒分选中等以上占主体;胶结类型以薄膜-孔隙型和孔隙-薄膜型、孔隙型、薄膜型、加大-孔隙型胶结为主.长6砂岩储层标准偏差对粒度平均值图解和重矿物组合、轻矿物组分都揭示了长6油层组时期研究区主要受东北方向物源影响,发育了多期叠置的三角洲前缘水下分流河道砂体,并且由于长距离搬运效应,残余粒间孔、长石溶孔较为发育,长石、绿泥石和高岭石的矿物组合在一定程度上提升了研究区的储层物性,并增加了低阻油藏的渗透性.长61和长62的水下分流河道砂体为研究区的优质储层发育区.

海上J油田自适应复合调驱技术研究与应用

针对海上J油田注入压力高、地层非均质性强、各层吸水不均、层间矛盾突出问题,设计了一种自适应复合调驱体系。确定了体系配方为8%自生气体系(生气剂亚硝酸钠与生气剂氯化铵质量比1.0∶1.1)+0.5%起泡剂+0.3%强化剂体系(聚合物+酚醛交联剂质量比1∶1),考察了体系的动静态性能。实验结果表明:该体系具有泡沫生成可控和成胶强度可控的“双控特点”,岩心实验结果表明该体系封堵率达到97.32%,采收率提高幅度高、中、低渗透率分别为19.59%、45.17%、57.83%,具有很好的调整吸水剖面性能。现场应用取得了很好的降水增油效果。该体系为海上油田水驱高效开发提供了技术支持,具有广阔应用前景。

海上低渗透油田油井低效原因分析及解堵措施

为了找出海上X油田油井低产低效的原因,并进一步提高海上低渗透油田的开发效率,在分析了目标油田基本概况以及开发现状的基础上,通过室内实验对目标油田油井损害原因进行的分析,并研制了一套新型复合解堵体系。结果表明:水锁伤害、入井流体伤害、有机质沉积伤害以及注入水和地层水不配伍导致的结垢伤害是造成海上X油田油井低效的主要原因。新型复合解堵体系主要由有机解堵液、无机解堵液和顶替液组成,有机解堵液对有机垢的溶解效果较好,无机解堵液对现场无机堵塞物的溶蚀能力较强,并且缓蚀性能较好。复合解堵体系对污染后的岩心具有良好的解堵效果,解堵后岩心的渗透率恢复值均能达到97%以上。现场应用结果表明,A1井采取复合解堵体系施工后解堵效果显著,日增油达到了60 m^(3)以上,措施有效期较长,施工效果较好。

Reservoir Geochemistry of the Kuche Petroleum System in the Tarim Basin, China

The geochemical characteristics of crude oils and reservoir core extracts from the Kuche petroleum system are described and studied systematically by means of various geochemical techniques and methods to acquire molecular information. The results suggest crude oils from the petroleum system can be divided into two groups: marine oils and non-marine oils. The former represents the dominant oils found in the area. Tar mats were firstly discovered and determined accurately in terrestrial oil and gas reservoirs, with Lower Tertiary sandstone reservoirs in the Yaha oilfield of the Tarim Basin. However, based on the ratio of 20S/(20S+20R)C-29 sterane as a maturity parameter, lacustrine oils filled into the Tertiary reservoirs in the direction toward the western part of the petroleum system. In contrast, according to the fact that methylcyclohexane indices of eastern oils are greater than those of western oils, the location in which coal-generated oils filled into the Tertiary reservoirs lies in the eastern part of the petroleum system.

A multi-mechanism numerical simulation model for CO_(2)-EOR and storage in fractured shale oil reservoirs

Under the policy background and advocacy of carbon capture,utilization,and storage(CCUS),CO_(2)-EOR has become a promising direction in the shale oil reservoir industry.The multi-scale pore structure distribution and fracture structure lead to complex multiphase flow,comprehensively considering multiple mechanisms is crucial for development and CO_(2) storage in fractured shale reservoirs.In this paper,a multi-mechanism coupled model is developed by MATLAB.Compared to the traditional Eclipse300 and MATLAB Reservoir Simulation Toolbox(MRST),this model considers the impact of pore structure on fluid phase behavior by the modified Peng—Robinson equation of state(PR-EOS),and the effect simultaneously radiate to Maxwell—Stefan(M—S)diffusion,stress sensitivity,the nano-confinement(NC)effect.Moreover,a modified embedded discrete fracture model(EDFM)is used to model the complex fractures,which optimizes connection types and half-transmissibility calculation approaches between non-neighboring connections(NNCs).The full implicit equation adopts the finite volume method(FVM)and Newton—Raphson iteration for discretization and solution.The model verification with the Eclipse300 and MRST is satisfactory.The results show that the interaction between the mechanisms significantly affects the production performance and storage characteristics.The effect of molecular diffusion may be overestimated in oil-dominated(liquid-dominated)shale reservoirs.The well spacing and injection gas rate are the most crucial factors affecting the production by sensitivity analysis.Moreover,the potential gas invasion risk is mentioned.This model provides a reliable theoretical basis for CO_(2)-EOR and sequestration in shale oil reservoirs.