裂缝性碳酸盐岩油藏脉冲注水研究

在裂缝性碳酸盐岩油田注水开发主要是利用毛细管的渗吸作用。注入水驱油时,毛管自吸作用使注入水进入基质系统并将原油驱替至裂缝系统。采用脉冲注水方式能够有效的利用渗吸作用来改善此类油藏的水驱开发效果,可以提高油藏的最终采收率。本文在实验室岩芯的渗吸规律与脉冲注水的分析基础上,论证合理的开发指标。实验研究表明,碳酸盐岩基质系统物性较差,从而在渗吸作用中驱油效率较低。相对自然渗吸作用,脉冲注水可提高0.61%~8.92%的驱油效率。在数值模拟与实际开发的验证中也表明脉冲注水能提高裂缝性碳酸盐岩油藏的采出程度。     

注采优化提高平面非均质低渗油藏井网水驱波及效率

不稳定注水广泛应用于非均质油藏的水驱开发,为进一步改善平面非均质低渗油藏水驱开发效果,采用与目标油藏对应的径向流物理模型,分析了3种注采方式下平面非均质油藏井组生产井生产动态及采收率,明确了3种注采方式改善水驱开发效果的作用机理,并给出3种不同注采方式的适用性。结果表明:不稳定注水方式可形成不稳定压力场,形成油水交渗及弹性力驱油,改善低渗区域的驱油效果;同步平衡产液量注采方式可改善整体水驱波及效率,并利用不稳定注水提高低渗区域原油采收率,整体采收率较高;异步平衡产液量注采方式可在不稳定注水后,调整注采压差,提高低渗区域驱油效率,同时扩大注入水对低渗区域的波及效率,大幅度提高低渗区域的采收率。实验结果可为目标油藏水驱开发注采方式优化提供理论支持。     

临盘油田盘二块稠油油藏水驱油规律试验研究

通过室内水驱油模拟试验,分别研究了盘二块稠油油藏注水过程中注水强度、注水方式对中、高渗储层水驱油效率的影响以及水驱油对储层物性的影响。结果表明:①常规稠油油藏注水开发高含水期可采出总可采储量的70%~75%以上;②提高注水强度、注水压力可有效地提高水驱油效率,且对中低渗稠油油藏更敏感;③水驱油可在一定程度上改变储层物性特征。     

缝洞型碳酸盐岩油藏水驱油机理模拟实验研究

缝洞型碳酸盐岩油藏由于储集空间特殊，结构复杂，其内部流体流动形态、流动机理不够明确。根据TH油田地质资料显示的缝洞联接方式，设计了2种缝洞物理模型，采用人工造缝造洞技术制备实验模型岩心，对缝洞型碳酸盐岩注水驱油时油水遵循的流动规律、水驱油效率的影响因素、合理的缝洞数学模型以及水驱油机理进行了研究，得出了相关的研究成果，为此类油藏的开发提供了指导。     

胜利油区不稳定注水技术的研究及应用

针对胜利油田储层类型和油藏：河流相正韵律沉积、三角洲沉积及复杂断块油藏，开展了不稳定注水机理研究及现场先导试验并推广应用。实践证明不稳定注水能够提高注水波及系数，提高油藏最终采收率。该技术具有投资少、见效快、增油显著的特点，是一种深化二次采油、改善水驱油藏开发效果的有效技术手段。     

吉7井区稠油油藏油水自乳化作用及水驱特征

因具有自乳化特征,吉7井区稠油油藏常温注水开发水驱特征不同于稀油油藏和普通稠油油藏,水驱开发驱油效率更高。基于吉7井区自乳化成因及乳化液特性分析,明确吉7井区水驱特征,认为吉7井区中含水期含水率长期稳定的主要原因是油包水自乳化使水油比接近1。进一步提出稳定水油比是适用于稠油油藏水驱管理的有效方法之一,保持水油比稳定在1可使稠油油藏采收率最大化。     

低渗透稀油油藏水驱后氮气泡沫驱适应性

吐哈油田低渗透稀油油藏注水开发进入高含水期后,水淹程度高,水驱调整措施效果较差,亟需寻找后续提高采收率方法。针对低渗透油藏注入能力差、不适合注聚合物等高黏度流体的特点,利用水驱、氮气泡沫驱和水驱后氮气泡沫驱开展室内实验研究,探讨驱油效率及其影响因素。结果表明,水驱驱油效率随渗透率的增加而升高,与渗透率呈较好的对数关系;氮气泡沫驱驱油效率为67.66%,较水驱驱油效率提高10.62%;氮气泡沫驱可在水驱的基础上提高驱油效率约9.63%。实验用泡沫的残余阻力系数大于1,表明氮气泡沫驱通过堵水调剖,提高了水驱后油藏的采收率,从机理和实验提高驱油效率程度判断,氮气泡沫驱适用于吐哈油田低渗透稀油油藏。     

胜利油区不稳定注水技术的研究及应用

针对胜利油区储层类型和油藏:河流相正韵律沉积、三角洲沉积及复杂断块油藏,开展了不稳定注水机理研究及现场先导试验并推广应用。实践证明不稳定注水能够提高注水波及系数,提高油藏最终采收率。该技术具有投资少、见效快、增油显著的特点,是一种深化二次采油、改善水驱油藏开发效果的有效技术手段。     

百色油田复杂断块油藏注水吞吐技术

百色油田油藏多属于陆相复杂小断块油藏，由于断块过小，油藏储量仅由单井控制，断层封闭，底边水不活跃，油藏在开发中得不到有效的能量补给，致使开发效果极差。单井注水吞吐开发模式一方面利用油层的亲水性、发挥毛管力吸水排油的作用实现水驱，一方面补充地层能量，恢复地层压力，实现人工补充能量。通过多周期的注采开发，逐渐扩大水驱波及半径、提高驱油效率，从而提高无能量补充断块的采收率。该技术在百色油田实际运用取得了较好的效果。     

低渗透油藏提高水驱效率技术对策——以胡尖山油田H区长4+5油藏为例

胡尖山油田H区长4+5油藏为鄂尔多斯盆地典型低渗透油藏,低孔、低渗、低压。长4+5油藏为多期河道叠加复合砂体储层,隔夹层发育、非均质性强,多层合采、多层分层注水。经多年开发及井网加密调整后,注水沿高渗带及诱导缝突进,油井多方向见水,水驱开发矛盾突出,水驱开发效率低。通过梳理影响H区长4+5油藏水驱效率提高的关键影响因素,有针对性地采取治理对策,达到提高低渗油藏水驱效率的目的。结果表明,影响研究区油藏水驱效率提高的主要因素为储层砂体连通程度、储层非均质性、水驱后诱导裂缝及高深渗带发育、水驱后储层物性变化及分注井分层注水有效性等。通过采取油水井补孔、单层增注、深部调剖调驱、均衡平面采液、优化分注工艺等治理技术对策,油藏水驱效果得到改善,油藏最终采收率提高,油藏向良性开发转变。     

塔河油田单井注氮气采油技术现场应用

塔河油田碳酸盐岩缝洞型油藏经过多年开发后,底水锥进、油水界面抬升,剩余油主要以阁楼油形式富集。现场实践证实注氮气采油开发碳酸盐岩缝洞型油藏是可行的,能有效动用阁楼型剩余油,并且在实践中总结了注氮气采油的选井经验,建立了高效注气井分类模型,为同类碳酸盐岩缝洞型油藏开发提供了参考依据。注氮气采油技术是一种高效提高采收率的技术手段。     

Numerical Simulation of the LSWI Effect on Hydrocarbon Recovery From Carbonate Rocks

Wettability alteration mechanism is still believed to be the main contributor to low salinity water injection (LSWI) effect on oil recovery from carbonate rocks. The authors investigated the main mechanism and contributor to the LSWI effect on oil recovery from carbonate rocks through history matching recently published corefloods using the UTCHEM simulator. The history match results suggest that wettability alteration has negligible effect on water relative permeability, which could be related to the double electric layer expansion mechanism. This paper provides a basis to develop a LSWI model to predict oil recovery from carbonate rocks.     

Three-dimensional physical simulation and optimization of water injection of a multi-well fractured-vuggy unit

With complex fractured-vuggy heterogeneous structures, water has to be injected to facilitate oil production. However, the effect of different water injection modes on oil recovery varies. The limitation of existing numerical simulation methods in representing fractured-vuggy carbonate reservoirs makes numerical simulation difficult to characterize the fluid flow in these reservoirs. In this paper, based on a geological example unit in the Tahe Oilfield, a three-dimensional physical model was designed and constructed to simulate fluid flow in a fractured-vuggy reservoir according to similarity criteria. The model was validated by simulating a bottom water drive reservoir, and then subsequent water injection modes were optimized. These were continuous (constant rate), intermittent, and pulsed injection of water. Experimental results reveal that due to the unbalanced formation pressure caused by pulsed water injection, the swept volume was expanded and consequently the highest oil recovery increment was achieved. Similar to continuous water injection, intermittent injection was influenced by factors including the connectivity of the fractured-vuggy reservoir, well depth, and the injection–production relationship, which led to a relative low oil recovery. This study may provide a constructive guide to field production and for the development of the commercial numerical models specialized for fractured-vuggy carbonate reservoirs.     

缝洞型油藏超深井注氮气提高采收率技术

塔河碳酸盐岩油藏非均质性强，溶洞是最主要的储集空间，裂缝主要起连通通道作用，储集体中流体以管流模式为主，储集体类型复杂导致对剩余油分布认识不清，前期主要依靠弹性和水驱开发，采收率较低。目前塔河油田缝洞型油藏注水开发后期面临挖潜困难、剩余油储量难以动用的情况，注氮气驱油工艺的提出为解决这一难题提供了思路和方法。通过对注入气源的选择、地面注入工艺的优化、井口及管柱优化，成功实现了气水混注降压工艺及多轮次注气—机抽生产转换作业，节约了成本，提高了生产时效，减少了施工风险。该研究为碳酸盐岩油藏注气提高采收率工作提供了新的借鉴。     

Black Oil and Compositional Reservoir Simulation for Increasing the Recovery Performance of an Iranian Fractured Carbonate Reservoir

Abstract

Naturally fractured reservoirs contain a significant amount of world oil reserves. Accurate and efficient reservoir simulation of naturally fractured reservoirs is one of the most important, challenging, and computationally intensive problems in reservoir engineering. Black oil and compositional reservoir simulators have been used to determine the reservoir management and production strategies to increase the oil recovery from a low-porosity, low-permeability fractured carbonate reservoir, with an average matrix permeability of 0.8 md, average fracture permeability of 500 md, and an average matrix porosity of 10%. This reservoir is a candidate for an enhanced oil recovery (EOR) process, because the reservoir production rate has been declined due to increasing the water cut as a result of rising the water oil contact. The injection techniques that have been considered in this study for black oil model include (a) gas injection, (b) water injection, and (c) simultaneous water alternating gas injection and for the compositional model include (a) dry gas injection, (b) CO₂ injection, and (c) N₂ injection. Simulation results show that CO₂ injection has the maximum oil recovery between the EOR scenarios.     

A Bohai Sea SZ36-1 Oil Field Formation Scaling Experimental Study and Scale Inhibitor Optimization

The authors studied Bohai sea SZ36-1 oil field scaling conditions and analyzed its formation characteristics as well as injected water characteristics. According to the Oddo-Tomson saturation index, this oil field scale can be calcium carbonate scale and calcium sulfate scale. Research indicates that calcium carbonate (CaCO₃) scale will form during the process of water injection, but calcium carbonate scale is not the main scaling type. With our own experiment measuring device and scale static and dynamic experimental evaluation data, the amount of actual scaling buildup can be calculated and the extent of the formation permeability damage caused by the amount of scaling buildup can also be studied. On this basis, the scale inhibitor can also be well selected. Conclusion of the study will help guide oil field water injection practice and reduce formation damage, and thereby enhance oil recovery.     

缝洞型碳酸盐岩油藏注氮气泡沫可行性及影响因素

为了研究缝洞型碳酸盐岩油藏注氮气泡沫可行性及影响因素,研制了缝洞型碳酸盐岩油藏细观物理模型和宏观剖面可视化物理模型,可由细观到宏观对缝洞型油藏注泡沫可行性及其影响因素进行室内物理模拟。细观物理模型实验结果表明:水驱后,剩余油主要以封闭孔洞内剩余油、阁楼油、绕流油和油膜的形式存在;氮气泡沫能通过重力分异及阻力效应启动阁楼油与绕流油并剥离油膜。在宏观剖面可视化物理模型上进行了注泡沫影响因素研究。实验结果表明:在含油饱和度较低时,以低部位井注、高部位井采(低注高采)的方式注泡沫效果更好,注泡沫时机不宜过早,宜在充分水驱的基础上转注泡沫;底水能量过强则不利于注泡沫,同时存在一个最优的泡沫注入量。对于碳酸盐岩缝洞型油藏开采中后期,注泡沫开采能够有效维持高效开发,提高原油采收率。     

碳酸盐岩缝洞型油藏提高采收率关键技术

中国碳酸盐岩缝洞型油资源量丰富,探明石油地质储量达29.3×10⁸ t,已经成为中国油气勘探开发和油气增储上产的重要领域。由于深埋5 500 m碳酸盐岩缝洞体的描述精度低、流动模式多样、模拟预测难度大,注水窜流易造成油井暴性水淹,导致采收率低仅为15.9%,此类油藏开发是世界级难题。经过多年的研究与实践,形成地球物理描述、地质建模、注水注气和酸压改造等提高采收率系列技术,单元应用后储量动用率提高了42%,同时已提高采收率2.3%,对同类深层、超深层强非均质性油藏开发具有借鉴作用。     

低矿化度注水提高砂岩储集层采收率的微观机理

低矿化度注水是一项前沿技术,因在碳酸盐岩和砂岩储集层中能提高驱油效果,目前受到广泛关注。本文梳理了砂岩储层低矿化度注水提高采收率的主要微观机理,即润湿性的改变、黏土的膨胀与运移、双电层的扩散等。低矿化度水的质量浓度、离子类型能改变多种黏土内部力平衡及黏土与原油之间的力平衡,造成双电层扩散,最终使黏土出现润湿性的改变以及膨胀运移的现象。低矿化度注水能提高大部分砂岩油藏的采收率。国内大部分砂岩油藏开发已进入中后期,进行低矿化度注水的微观机理研究对砂岩油藏开发有极大的指导意义。     

碳酸盐岩缝洞型油藏单井注水替油开采的成功实践

塔河油田主要储渗空间为碳酸盐岩的岩溶缝-洞复合体,非均质性极强,多数井间不连通,油藏采收率仅有12％左右,其封闭型单井油藏年产量递减达到30%~90%、采收率仅有2.5%~5.5%. 在封闭型单井开展注水吞吐替油开采试验,利用重力分异原理注水置换替油并补充地层能量,提高这类油井的产能和采收率。数值模拟研究表明这种开采方式是可行的。通过对110 口井矿场试验与推广,注水132.18×10⁴ t、增油45.25×10⁴ t,单井初期日增油13~164 t、周期增油55~3 076 t,其中典型长停井X81 注水吞吐替油后采收率已提高了12.67 个百分点。