Research on Well Testing Interpretation of Low Permeability Deformed Dual Medium Reservoir

Considering the influence of quadratic gradient term and medium deformation on the seepage equation, a well testing interpretation model for low permeability and deformation dual medium reservoirs was derived and established. The difference method was used to solve the problem, and pressure and pressure derivative double logarithmic curves were drawn to analyze the seepage law. The research results indicate that the influence of starting pressure gradient and medium deformation on the pressure characteristic curve is mainly manifested in the middle and late stages. The larger the value, the more obvious the upward warping of the pressure and pressure derivative curve;the parameter characterizing the dual medium is the crossflow coefficient. The channeling coefficient determines the time and location of the appearance of the “concave”. The smaller the value, the later the appearance of the “concave”, and the more to the right of the “concave”.

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.

Effect of absorption boundary layer on nonlinear flow in low permeability porous media

Taking low permeability cores of Daqing oilfield for example,the flow characteristics at low velocity were studied with the self-designed micro-flux measuring instrument.Considering the throat distribution and capillary model,the thickness of fluid boundary layer under different pressure gradients was calculated,and the mechanism and influencing factors of nonlinear percolation were discussed.The results show that the percolation curve of ultra-low rocks is nonlinear,and apparent permeability is not a constant which increases with pressure gradient.The absorption boundary layer decreases with the increase of pressure gradient,and changes significantly especially in low pressure gradient,which is the essence of nonlinear percolation.The absorption boundary layer is also found to be impacted by the surface property of rocks.

Fretting Wear Behavior of Medium Carbon Steel Modified by Low Temperature Gas Multi-component Thermo-chemical Treatment

The introduction of surface engineering is expected to be an effective strategy against fretting damage. A large number of studies show that the low gas multi-component （such as carbon, nitrogen, sulphur and oxygen, etc） thermo-chemical treatment（LTGMTT） can overcome the brittleness of nitriding process, and upgrade the surface hardness and improve the wear resistance and fatigue properties of the work-pieces significantly. However, there are few reports on the anti-fretting properties of the LTGMTT modified layer up to now, which limits the applications of fretting. So this paper discusses the fretting wear behavior of modified layer on the surface of LZ50 （0.48%C） steel prepared by low temperature gas multi-component thermo-chemical treatment （LTGMTT） technology. The fretting wear tests of the modified layer flat specimens and its substrate （LZ50 steel） against 52100 steel balls with diameter of 40 mm are carried out under normal load of 150 N and displacement amplitudes varied from 2 μm to 40 μm. Characterization of the modified layer and dynamic analyses in combination with microscopic examinations were performed through the means of scanning electron microscope（SEM）, optical microscope（OM）, X-ray diffraction（XRD） and surface profilometer. The experimental results showed that the modified layer with a total thickness of 60 μm was consisted of three parts, i.e., loose layer, compound layer and diffusion layer. Compared with the substrate, the range of the mixed fretting regime（MFR） of the LTGMTT modified layer diminished, and the slip regime（SR） of the modified layer shifted to the direction of smaller displacement amplitude. The coefficient of friction（COF） of the modified layer was lower than that of the substrate in the initial stage. For the modified layer, the damage in partial slip regime（PSR） was very slight. The fretting wear mechanism of the modified layer both in MFR and SR was abrasive wear and delamination. The modified layer presented better wear resistance than the substrate in PSR and MFR; however, in SR, the wear resistance of the modified layer decreased with the increase of the displacement amplitudes. The experimental results can provide some experimental bases for promoting industrial application of LTGMTT modified layer in anti-fretting wear.

Timing of advanced water flooding in low permeability reservoirs

It is very important to design the optimum starting time of water injection for the development of low permeability reservoirs. In this type of reservoir the starting time of water injection will be affected by a reservoir pressure-sensitive effect. In order to optimize the starting time of water injection in low permeability reservoirs, this effect of pressure change on rock permeability of low permeability reservoirs was, at first, studied by physical simulation. It was shown that the rock permeability decreases exponentially with an increase in formation pressure. Secondly, we conducted a reservoir engineering study, from which we obtained analytic relationships between formation pressure, oil production rate, water production rate and water injection rate. After our physical, theoretical and economical analyses, we proposed an approach which takes the pressure-sensitive effect into consideration and designed the optimum starting time of water injection, based on the principle of material balance. Finally, the corresponding software was developed and applied to one block of the Jiangsu Oilfield. It is shown that water injection, in advance of production, can decrease the adverse impact of the pressure-sensitive effect on low permeability reservoir development. A water-flooding project should be preferably initiated in advance of production for no more than one year and the optimum ratio of formation pressure to initial formation pressure should be maintained at a level between 1.05 and 1.2.

大庆油田水驱开发技术及其发展方向

通过回顾大庆油田水驱开发技术发展历程,系统总结了近10年创新发展的水驱层系井网优化调整、近阻组合注水优化调整、区块及单井套损预警防控等油田主体开发技术。在客观分析大庆油田水驱主要矛盾问题的基础上,明确了水驱开发核心技术发展方向。在井网调整方面,攻关以“两驱协同、优选井型”为核心的井网优化调整技术,通过“二三结合”井网优化、分类储层加密调驱、井缝协同井网调整、多井型高效挖潜等井网调整新技术攻关,实现由水驱直井均匀加密向两驱协同、多井网多井型立体调整转变;在结构调整方面,攻关以“智能优化、水驱+”为核心的新一代综合调整技术,通过智能注采优化、低渗透储层功能性水驱、特低渗断块油藏压驱提产等技术攻关,实现由常规注采调整向智能调控、多方式补能转变;在套损防控方面,攻关以“层位预警、套损复产”为核心的套损精准防治技术,在深化地质力学机理研究基础上,发展套损层位精准预警技术、套损区复产挖潜技术,实现由区块、单井预警向大数据与地应力分析相结合的套损层位精准预警及防控转变。

中低渗砂岩油藏水驱后期油藏再评价及提高采收率对策

为探究高—特高含水中低渗油藏水驱开发后期提高采收率的有效途径,以南湖油田为例,利用矿物分析与SEM等方法深化储层微观特征再认识,应用核磁共振与压汞结合的方法研究冻胶分散体提高采收率的可行性和应用效果。研究表明:南湖油田大孔道较发育,速敏与水敏特征明显,水窜严重是开发低效的主要原因,低排量注水、保持地层能量、控制水窜是提高开发效果的关键;冻胶分散体能有效抑制水窜,提高中小孔隙剩余油的启动能力,通过冻胶分散体驱替后,样品岩心小孔隙采收率提高52.83个百分点,中孔隙采收率提高34.60个百分点,综合采收率提高33.14个百分点,开发效果显著提升。研究结果可为高含水油藏改善开发效果提供借鉴。

深层低渗凝析气藏气驱适应性研究

针对深层低渗凝析气藏由衰竭开采转变为气驱开发过程中适应性不明确的问题,综合采用PVT(地层流体高压物性)分析仪、长岩心驱替物理模拟技术和数值模拟计算方法,开展了一系列评价研究。通过对比分析注CO_(2)、天然气(伴生气、CH_(4))、N_(2)对凝析气体系高压物性影响与提高凝析油采出程度情况,明确了深层低渗凝析气藏气驱的适应性。实验结果表明:CO_(2)在凝析油中的溶解度和溶解气油比最大,具有较强降低凝析气藏饱和压力和露点压力的特点,提高凝析油采出程度的效果最佳。同时,采用长岩心物理模拟技术针对CO_(2)驱进行了注入时机、注入方式、注气速度优化研究,明确了在露点压力以上脉冲式注气效果更好,为注气开发技术政策及现场方案的实施提供数据支撑。

元坝隔层型底水气藏水侵动态实验模拟研究

元坝长兴组生物礁储层纵向发育多期生物礁,不同期次礁体之间均发育不同程度的不渗透隔层、低渗透隔层,纵横向展布连续性差,隔层如何影响底水水侵动态是气藏开发关注的重点和难点.本文首次设计了7组无隔层、低渗透隔层、不渗透隔层型底水水侵全直径岩心物理模拟实验:主要包括无隔层型、不渗透隔层型和低渗透隔型底水水侵模拟对比实验,不渗透隔层型底水在不同衰竭速度下的水侵动态模拟实验,不同厚度低渗透隔层水侵动态模拟实验.实验结果表明,隔层型底水气藏水侵可划分为以天然气弹性能为主要驱动能的弹性气驱、受天然气弹性能与底水水体补能共同作用的水体补能及受水侵储层伤害控制的气水同产三类渗流阶段,隔层、低采速、高厚度隔层能够抑制底水过快水侵到井底,提高气藏开发效果.基于无隔层、有隔层型底水水侵渗流阶段的差异性建立了水侵模式诊断曲线,为明确底水气藏模式提供了理论支撑.

“一点法”产能评价方法的内涵、矿场应用及改进

近年来,在四川盆地气井产能评价实践中发现,针对低渗强非均质性和中高渗储层,常规“一点法”适用性差。为探索并解决该问题,文中系统梳理并总结了“一点法”产能评价方法的不同形式,揭示了其内涵。“一点法”的内涵主要包括均质储层、可靠的稳定经验数、气井现场测试达到拟稳定渗流状态3个方面,围绕这3个方面的内涵,指明了“一点法”的矿场应用偏差。在此基础上,首先深入剖析了“一点法”计算参数的敏感性;其次对矿场应用提出了改进和数据处理方法,建立了稳定经验数与试井地层系数的经验关系式及不同层系试井地层系数与测井储能系数拟合关系式;再次,提出了不同类型气井测试数据评价方法及试油建议;最后应用文中建立的“一点法”改进方法对四川盆地不同气田的31口气井进行了计算对比,验证了方法的可靠性和可行性。该改进方法不仅适用于常规“一点法”的应用领域,也适用于具有低渗强非均质性、中高渗地质特征的气田,弥补了特定地质条件下常规“一点法”确定气井稳定产能误差大的不足,对于气田的开发设计、规模调整和现场生产组织均具有积极意义。

中低渗油藏适用性工艺技术的研究与应用

河口采油厂管辖的油田是中低渗油藏。在复杂低渗油藏条件下,目前进入特高含水开发阶段。该油田中低渗油藏的特性开发中面临着注采不对应、开发效果下降、工艺技术适应性变差等问题。因此,为了改善油藏开发效果和最终采收率,要求采用特殊适用的工艺技术。为了提高措施效果和油藏采收率,开展了工艺的适用性研究,以确保工艺技术与不同类型的油藏特点相适应。2021年的现场实际应用表明,这些工艺技术体系具有较强的适应性,取得较好的增注、增油、降水效果。

低盐水驱对中低渗砂岩采收率及润湿性影响

低盐水驱是一项前沿的改善水驱技术,具有成本低、环境友好等优点。大庆油田中、低渗储层物性较差,化学驱效果不理想,而低盐水驱在中、低渗储层应用前景良好。分别选大庆油田中、低渗透率岩心各5块,采用矿化度为1 000~10 000 mg·L^(-1)盐水开展岩心驱替实验和接触角测试。结果表明:当注入水矿化度由10 000 mg·L^(-1)降为5 000 mg·L^(-1)时,采收率增加,等渗点右移,含油饱和度下降,储层变为水湿;当注入水矿化度从5 000 mg·L^(-1)降为1 000 mg·L^(-1)时,采收率下降,等渗点左移,驱替压力上升,引发黏土膨胀,含油饱和度上升,储层为中性润湿。因此,利用低盐水驱开发大庆油田中、低渗油藏可行,能够提高原油采收率,并改善注入能力,并且矿化度阈值为5 000 mg·L^(-1)。

低渗煤层瓦斯抽采顺层钻孔水力造穴卸压增透效果研究

为了揭示水力造穴参数对钻孔瓦斯抽采效果的影响规律,指导煤层水力造穴增透技术施工参数的合理选择。建立了煤层损伤-应力-渗流耦合模型,分析了不同造穴参数下煤层卸压增透效果,展开了顺层钻孔水力造穴现场工程试验,考察了不同造穴参数下钻孔瓦斯抽采效果,结果表明:采用水力造穴技术形成的孔穴能够有效降低其周围煤体应力,提高煤层渗透率,增加瓦斯钻孔抽采效果;造穴半径越大煤层的卸压程度越大,进而煤层渗透率增幅就越大,但在实际工程中过大的造穴半径会使得孔穴稳定性差,钻孔塌孔堵塞瓦斯涌出通道会使得钻孔瓦斯抽采量有所降低,试验矿井最优造穴半径为0.6 m;造穴间距对它们之间的应力降低区范围有着较大的影响,在一定距离条件下孔穴卸压有着明显的叠加效应,造穴间距越近叠加效应越明显,煤层应力越小,卸压增透效果越好。试验钻孔穴间距由8 m减小到6 m时,单孔平均瓦斯抽采纯量增加389.16%。

不同耕作施肥模式对夏玉米干物质积累、产量和氮肥利用率的影响

针对当前中低产夏玉米田耕层薄、犁底层厚、单施缓释肥及玉米生育前期氮素供应不足的问题,本试验以玉米品种联创839为材料,在施氮240 kg/hm^(2)条件下,设置免耕单层PK肥(无氮肥,SPK)、免耕单层缓释NPK肥(SNPK)、免耕单层掺混NPK肥(SNMPK)、深松分层PK肥(无氮肥,DPK)、深松缓释NPK肥(DNPK)、深松分层NPK肥(DNLPK)共6个处理,所有肥料均一次性基施,研究不同耕作施肥处理对夏玉米干物质积累、产量和氮肥利用率的影响。结果表明,不同耕作施肥处理对玉米成熟期干物质积累量和产量影响显著,其中DNLPK处理玉米干物质积累量和产量均最高,较DNPK、SNMPK、SNPK处理分别显著提高了8.8%、5.7%,9.5%、5.4%和13.0%、12.0%;不同耕作施肥处理对茎叶干物质转运量和转运率影响显著,缺氮处理的干物质转运量和转运率均较高,其中DPK处理均最高,较DNLPK处理高出511.00 kg/hm^(2)和7.99个百分点;不同耕作施肥处理显著影响花前干物质对籽粒的贡献率,缺氮处理的较高,其中SPK处理最高,比DNLPK处理高出11.17个百分点;不同耕作施肥处理对植株氮素积累量影响显著,其中DNLPK处理最高,较DNPK、SNMPK、SNPK处理分别提高1.9%、3.9%、5.4%,均达显著水平;不同耕作施肥处理对氮肥表观利用效率影响显著,其中DNLPK处理最高,较DNPK、SNMPK、SNPK处理分别提高4.9%、7.1%、11.0%,均达显著水平。综上看出,深松分层施肥技术既能满足中低产田夏玉米对养分的需求,又能提高氮肥利用率,实现产量提升。该结论可为深松分层施肥技术在生产上大面积推广应用提供数据支撑和理论依据。

低渗透油藏微乳液驱渗流规律研究

主要探索了微乳液驱在低渗透油藏的渗流规律,并研究流体在低渗透介质空隙中的渗流边界体,微乳液驱在改善油气外部环境以及流体的可流动性;分析微乳液在降低界面张力、渗透边界层和启动压力梯度进行理论分析。

单一低透气性煤层水耦合深孔预裂爆破增透技术研究与应用

为解决单一低透气性煤层瓦斯透气性差、抽采困难、传统爆破方式增透效果不佳等问题,提出采用水耦合装药替代空气不耦合的方式。通过ANSYS/LS-DYNA软件建立水耦合装药深孔预裂爆破模型,分析水耦合装药方式爆破后应力波传递和裂隙的延伸效果,得出了水耦合装药方式能够更好的传递爆破产生的应力波。在河南省新郑煤电有限责任公司14207下底抽巷开展水耦合深孔预裂爆破试验,爆破致裂后,煤层瓦斯浓度和标态瓦斯纯流量都有提高,与数值模拟结果相互验证,表明该方法可以较好的增加煤层的透气性,改善单一低透气性煤层瓦斯抽采困难的问题。

Uncoupled state space solution to layered poroelastic medium with anisotropic permeability and compressible pore fluid

This paper presents an uncoupled state space solution to three-dimensional consolidation of layered poroelastic medium with anisotropic permeability and compressible pore fluid.Starting from the basic equations of poroelastic medium,and introducing intermediate variables,the state space equation usually comprising eight coupled state vectors is uncoupled into two sets of equations of six and two state vectors in the Laplace-Fourier transform domain.Combined with the continuity conditions between adjacent layers and boundary conditions,the uncoupled state space solution of a layered poroelastic medium is obtained by using the transfer matrix method.Numerical results show that the anisotropy of permeability and the compressibility of pore fluid have remarkable influence on the consolidation behavior of poroelastic medium.

聚合物类型、注液方式和层系组合方式对聚驱效果的影响实验

目前大庆油田聚合物驱油技术的应用对象已经由一类储层向二、三类储层转移,原注入体系在注聚初期阶段的适应性较差,对高渗层的封堵能力弱,需要进一步评价注入体系和优化注入方式,以提高聚驱效果。因此开展了聚合物类型、注液方式和层系组合方式对聚驱效果影响实验研究。结果表明:实验所用“抗盐”聚合物低剪切强度表现为内摩擦力即视黏度损失较小,但高剪切强度条件下结构易于破坏,致使黏度保留率较低、滞留和液流转向能力较差;考虑到矿场注入压力受到储层岩石破裂压力限制,与“恒速”注入方式相比较,“恒速/恒压”注入方式和现场注入方式更为贴近;采用“分步注入”,模型中“层内非均质”岩心打开时机较晚,最终采收率增幅较大。实验结果可以为矿场局部注聚技术的推广提供技术支持。

水平井+CO_(2)吞吐改善中低渗稠油油藏开发效果机制解析——以大港油田刘官庄埕隆1601区块为例

大港油田刘官庄埕隆1601区块特稠油油藏由于受原油粘度大、渗透率低、油层厚度薄、出砂及地面环境复杂等苛刻条件的制约,多年来常规的开采技术无法实现动用,为此开展了“水平井+CO_(2)吞吐”技术研究及矿场试验。利用室内实验及数值模拟手段,开展增油机制研究及注采参数优化,结果表明CO_(2)与稠油在非混相状态下混溶后,稠油粘度由16800 mPa·s下降至69 mPa·s,降粘率达99.6%,原油启动压力梯度由19.1 MPa/m降低至0.2 MPa/m,储层绝对渗透率提高了约41.86%,有效提高了稠油的流动性能;优化后的合理注采参数为:单位水平段注入强度3.5~5.5 t/m,单位水平段注入速度0.5~0.6 t/(m·d),闷井时间为25~35 d,单位水平段产液强度为0.075~0.125 m3/(m·d),采用“抽油机+液力反馈泵+电加热杆”及水力喷射泵两种注采一体化工艺。矿场“水平井+CO_(2)吞吐”技术试验证实,单井单轮次增油1000~2000 t,最高增油达4000 t以上,换油率2.0~4.5 t/t,技术和经济效果显著,证实了该技术的可靠实用性,为中低渗稠油油藏的有效开发提供了很好的借鉴。

高速铁路中低压缩性土路基沉降计算与分析

高速铁路路基沉降计算与分析是路基设计及评估的重要环节。为准确计算高速铁路中低压缩性土路基沉降,从中低压缩性土的工程特性出发,基于考虑时间效应的压缩层厚度计算方法和分层连续加载下地基沉降计算理论,建立更适应于高铁路基荷载特征的高铁中低压缩性土路基沉降计算方法。利用吉珲铁路珲春试验工点得到的地基土物理和力学指标,计算路堤分级堆载条件下,不同埋深处上层硬塑粉质黏土和下层全风化泥质粉砂岩地基的时效变形规律。结果表明,在路基填筑过程中,基底附加应力计算方法获取的基底附加应力与实测值较为吻合。进一步对比理论与现场实测结果发现,截至第700天,地基总沉降的计算误差约2mm;地基分层沉降的理论值与计算值误差在±5%以内,验证了计算方法的可靠性和准确性;针对考虑时间效应的压缩层厚度计算确定的地基压缩层厚度,其随路基填筑高度呈线性正相关。上述方法不仅为合理选择并优化高速铁路中低压缩性土的地基加固措施及方案提供了关键的技术支撑,也为精确计算和预测工后沉降提供了保障。