Research and Application of CO₂Flooding Enhanced Oil Recovery in Low Permeability Oilfield

This paper discusses the new progress and field application of CO2 flooding in low permeability reservoirs enhanced oil recovery. The study shows that CO2 flooding can improve the oil recovery rate of low permeability oilfield by more than 10%. The practice shows that the liquid CO2 injection in low permeability reservoir is easier than water injection, and the reservoir generally has better CO2 storage.

Model building for Chang-8 low permeability sandstone reservoir in the Yanchang formation of the Xifeng oil field

In order to build a model for the Chang-8 low permeability sandstone reservoir in the Yanchang formation of the Xifeng oil field,we studied sedimentation and diagenesis of sandstone and analyzed major factors controlling this low permeability reservoir.By doing so,we have made clear that the spatial distribution of reservoir attribute parameters is controlled by the spatial distribution of various kinds of sandstone bodies.By taking advantage of many coring wells and high quality logging data,we used regression analysis for a single well with geological conditions as constraints,to build the interpretation model for logging data and to calculate attribute parameters for a single well,which ensured accuracy of the 1-D vertical model.On this basis,we built a litho-facies model to replace the sedimentary facies model.In addition,we also built a porosity model by using a sequential Gaussian simulation with the lithofacies model as the constraint.In the end,we built a permeability model by using Markov-Bayes simula-tion,with the porosity attribute as the covariate.The results show that the permeability model reflects very well the relative differences between low permeability values,which is of great importance for locating high permeability zones and forecasting zones favorable for exploration and exploitation.

A Case of Multi-Stage Fracturing Horizontal Well Used in BZ Oilfield in Bohai Bay Low-Permeability Oilfield Development

BZ oilfield in Bohai Bay of China was a typical offshore low permeability oilfield, which was restricted by many factors such as environment and economy. In this paper, the development characteristics of BZ oilfield were summarized in depth, and the new development mode of offshore low-permeability oilfield was explored from reservoir prediction, well spacing and fracturing technology. Taking BZ oilfield as an example, a set of technical system for the effective development of offshore low permeability oilfield had been formed through research, which mainly includes reservoir prediction and evaluation of offshore middle and deep low permeability oilfield, optimization of horizontal well pattern, multi-stage fracturing design of horizontal well and other technologies. The results show that improving the resolution of seismic data, strengthening the analysis of seismic reflection characteristics and carrying out the comprehensive study of seismic geology were the keys to solve the reservoir prediction of offshore low-permeability oil fields. Multi-stage fracturing horizontal well pattern is the main pattern of offshore low-permeability oilfield development. The parameters of multi-stage fracturing horizontal well together affect the development effect. Selecting the optimal fractured horizontal well pattern can greatly improve the development effect. The successful combination and application of new technology system was the foundation and core of conquering offshore low-permeability oil fields. On the basis of understanding the geological characteristics of oil reservoirs, it is an effective means of developing offshore low-permeability oil fields by selecting reasonable production methods, well types and well patterns. Using efficient perforation and fracturing technology to successfully control fracture parameters and form optimal injection and production well pattern was the key to improve low permeability offshore oil fields.

Advances in enhanced oil recovery technologies for low permeability reservoirs

Low permeability oil and gas resources are rich and have great potential all over the world, which has gradually become the main goal of oil and gas development. However, after traditional primary and secondary exploitation, there is still a large amount of remaining oil that has not been recovered.Therefore, in recent years, enhanced oil recovery(EOR) technologies for low permeability reservoirs have been greatly developed to further improve crude oil production. This study presents a comprehensive review of EOR technologies in low permeability reservoirs with an emphasis on gas flooding, surfactant flooding, nanofluid flooding and imbibition EOR technologies. In addition, two kinds of gel systems are introduced for conformance control in low permeability reservoirs with channeling problems. Finally,the technical challenges, directions and outlooks of EOR in low permeability reservoirs are addressed.

Development of the theory and technology for low permeability reservoirs in China

The development theories of low-permeability oil and gas reservoirs are refined, the key development technologies are summarized, and the prospect and technical direction of sustainable development are discussed based on the understanding and research on developed low-permeability oil and gas resources in China. The main achievements include:(1) the theories of low-permeability reservoir seepage, dual-medium seepage, relative homogeneity, etc.(2) the well location optimization technology combining favorable area of reservoir with gas-bearing prediction and combining pre-stack with post-stack;(3) oriented perforating multi-fracture, multistage sand adding, multistage temporary plugging, vertical well multilayer, horizontal and other fracturing techniques to improve productivity of single well;(4) the technology of increasing injection and keeping pressure, such as overall decreasing pressure, local pressurization, shaped charge stamping and plugging removal, fine separate injection, mild advanced water injection and so on;(5) enhanced recovery technology of optimization of injection-production well network in horizontal wells. To continue to develop low-permeability reserves economically and effectively, there are three aspects of work to be done well:(1) depending on technical improvement, continue to innovate new technologies and methods, establish a new mode of low quality reservoir development economically, determine the main technical boundaries and form replacement technology reserves of advanced development;(2) adhering to the management system of low cost technology & low cost, set up a complete set of low-cost dual integration innovation system through continuous innovation in technology and management;(3) striving for national preferential policies.

Geologic characteristics, controlling factors and hydrocarbon accumulation mechanisms of China’s Large Gas Provinces of low porosity and permeability

Based on the analysis of the geological characteristics and controlling factors, we analyzed the formation mechanism of different types of gas reservoirs. The main characteristics of gas provinces with low porosity and permeability are mainly as follows: large area, low abundance, small gas pools and large gas provinces; widely distributed excellent hydrocarbon source rocks with closely contacted source-reservoir-cap association; development mainly in large continental depressions or in paralic shallow-river delta systems; many kinds of traps coexisting in large areas, dominantly para-layered lithologic, digenetic and capillary pressure traps; double fluid flow mechanisms of Darcy flow and non-Darcy flow; complicated gas and water relations; and having the resource distribution of highly productive "sweet spots", banding concentration, and macroscopically large areas integrated. The main controlling factors of large sandstone gas provinces with low porosity and permeability are stable dynamic backgrounds and gentle structural frameworks which control the extensive distribution of alternate (interbedded) sandstones and mudstones; weak hydropower of large gentle lake basins controlling the formation of discontinuous, low porosity and permeability reservoirs in shallow-water deltas; regionally differential diagenesis and no homogeneous digenetic facies controlling the development of favorable reservoirs and digenetic traps; and weak and dispersive reservoir-forming dynamic forces leading to the widely distributed small traps with low abundance. Low porosity and permeability gas provinces with different trap types have different formation mechanisms which include fluid diversion pressure difference interactive mechanism of lithologic-trap gas accumulations, separated differential collection mechanism of digenetic-trap gas accumulations, and the Non-Darcy flow mechanism of capillary-pressure gas accumulations.

低渗透油田微生物堵剂的多尺度封堵性能

封堵低渗透油藏的多尺度水窜通道是提升这类油藏水驱开发效果的关键,开发了一种内源微生物堵剂,优化了其菌种发酵营养液配方,并基于室内静态实验表征了其基础物性,最后通过岩心动态实验评价了其封堵适应性。所优化的菌种发酵营养液配方为:1.0%~2.0%糖蜜+0.2%~1.0%硝酸钠+0.5%~2.0%磷酸二氢钾+0.2%~1.0%磷酸氢二钠+0.1%~0.5%硫酸铵+0.01%~0.1%工业酵母膏+0.01%~0.03%硫酸铁+0.01%~0.03%硫酸锰。在营养液中培养4 d后,微生物趋于稳定,形成的分散颗粒呈正态分布,粒径集中在40~160μm之间,粒度中值在90μm左右,且具有良好的抗剪切性、耐盐性及稳定性。初始态的微生物调堵剂能顺利进入低渗透岩心、非均质岩心和裂缝性岩心。进入岩心后,微生物基于其自生长特性与孔隙及裂缝介质匹配,对渗透率为5×10^(-3)μm^(2)的岩心的封堵率达到80%;对渗透率为5×10^(-3)/100×10^(-3)μm^(2)的非均质岩心的封堵率达92%;对渗透率为5×10^(-3)/300×10^(-3)μm^(2)的非均质岩心的封堵率达95%。微生物堵剂对开度为30μm的裂缝性岩心的封堵率达84%;对开度为80μm的裂缝性岩心的封堵率接近90%。微生物堵剂既可以封堵不同尺度的多孔介质水窜通道,又可以封堵不同尺度的微裂缝水窜通道,具备封堵低渗透油田多尺度水窜通道的潜力。

低渗透稠油油藏CO_(2)压驱提高采收率机理及规律研究

为明确低渗透稠油油藏CO_(2)压驱开采机理及开发效果,利用相态模拟技术分析了CO_(2)对稠油的作用机理。基于有限元离散法,建立了裂缝扩展渗流场-应力场耦合模型,分析了注入压力对裂缝扩展行为的影响。基于裂缝生成模拟结果,建立了考虑CO_(2)复合压驱后形成复杂裂缝的数值模型,进行了油藏压后生产模拟,形成了基于油藏动态参数的稠油油藏CO_(2)压驱数值模拟方法,分析了CO_(2)压驱过程中的裂缝扩展规律,优化了CO_(2)压驱工艺参数。模拟结果表明,CO_(2)压驱的主要作用机理包括降低原油黏度、膨胀原油、增强原油流动性、在注入井附近造缝提高CO_(2)注入能力及增加地层压力。CO_(2)具有较好的增能效果,CO_(2)运移受储层非均质性影响严重,气体超覆作用导致注入的CO_(2)易在储层上部位聚集,上部位原油降黏效果更为显著。通过优化稠油CO_(2)压驱工艺参数,建议压驱注入压力控制在40~50 MPa。该研究结果对稠油油藏CO_(2)压驱设计及现场应用具有一定的指导作用。

适用于套损井修复的高强度复合材料研究及应用

针对西部某特低渗透油田套损井采用机械封隔和水泥封堵修复技术成功率低以及有效期短的问题,以改性环氧树脂GE-1、缓凝剂柠檬酸、分散剂NNO、硅烷偶联剂KH-540、消泡剂SQ-XP105、固化剂GH-3和纳米二氧化硅为原料,制备了一种适用于套损井修复的高强度复合材料,并对其综合性能进行了评价。结果表明:高强度复合材料具有良好的稠化性能,在150℃下的稠化时间仍大于400 min;材料具有良好的力学性能,150℃下固化试件的抗压强度可达110.5 MPa,抗折强度可达32.4 MPa;材料的耐酸碱和耐盐性能较强,在强酸、强碱或者高矿化度水溶液中浸泡后的质量损失率较低;另外,材料还具有良好的封堵性能,填砂管中注入高强度复合材料后,水驱的突破压力可以达到42.6 MPa。现场应用结果表明:5口套损井采用高强度复合材料封堵修复均一次成功,成功率为100%,现场施工压力较高,套损井修复效果较好。

渤海油田中低渗油藏“凝胶+微球”组合调剖体系研究与应用

针对渤海Z油田6井区中低渗储层注入水窜流严重、水驱效率低的问题,开发了乳液聚合物凝胶+水基微球组合调剖体系。实验结果表明,乳液聚合物凝胶体系成胶稳定时间为7 d左右,成胶黏度大于20000 mPa·s;水基微球粒径14 d左右膨胀到最大。乳液聚合物凝胶+水基微球组合体系在双管并联岩心实验中具有较好的改善剖面能力,可有效启动低渗岩心,两根岩心提高采收率分别为12.57%和15.33%。组合体系在6井区边部4井组现场试验,实施措施后3口油井全部受效,井组高峰期日增油45.79 m^(3),单井最高含水下降20.47%,9个月内累计增油1.5×10^(4)m^(3)。

低渗透油田生物酶化学驱油技术

低渗透油田开发面临传统采油技术效率低、环境污染等挑战,生物酶化学驱油技术因其环保高效而备受关注,但其在低渗透油田中的适用性和稳定性尚需进一步研究。针对这些问题展开系统性的实验研究,首先通过对不同种类生物酶的优选,发现脂肪酶在不同质量浓度下表现出最显著的驱油效果,最佳质量浓度为2.0 g·L^(-1),可提高原油采收率至24.5%。其次,评价脂肪酶在高盐度和碱性条件下的稳定性,发现在适当质量浓度下脂肪酶仍能保持较高的驱油效果,但在极端条件下其活性可能会受到抑制。最后,研究发现脂肪酶能够有效降低原油表面张力,当质量浓度为2.0 g·L^(-1)时,原油表面张力可降至37.9 m N·m^(-1)。

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。

高效疏水性纳米颗粒合成及其在低渗透油田驱油特性

为提高低渗透油田的驱油效率,通过化学还原法合成了高效疏水性银纳米颗粒(SHAg),并系统评估了其在油田模拟水中的稳定性、分散性以及岩心驱替实验中的驱油性能。研究发现,通过控制三甲基氯硅烷(TMCS)的质量分数,可以有效调节SHAg的疏水性,当TMCS质量分数为0.5%时,SHAg的接触角达到112.4°,表现出优异的疏水性。此外,SHAg在模拟油田水中展现出良好的稳定性和分散性,特别是在5%的NaCl质量分数下,其平均粒径仅为83.6 nm。岩心驱替实验结果表明,含有400 mg·L^(-1)SHAg的驱替液的驱油效率高达59.7%,显著高于纯水驱的基础驱油效率。这一研究不仅揭示了疏水性纳米颗粒在提高低渗透油田驱油效率中的潜力,而且为实际油田应用提供了重要的理论依据和技术支持。

中国海上低渗油气田开发历程、关键技术及攻关方向

中国海上低渗透油气资源丰富、分布广泛,但受海洋特殊作业环境、技术和经济性等限制,经济有效开采难度大,攻克技术瓶颈、推进规模化开发意义重大。历经多年实践,充分吸收陆上油田开发经验,立足少井高产,围绕“四个匹配”攻关形成了具有海上特色的低渗有效开发技术路径,提出三项开发策略“压裂投产、能量补充、降本增效”和5项关键技术内容,即储层综合评价、有效能量补充、地质工程一体化、压裂工艺工具与经济评价,成功突破了20 mD以上低渗透油藏开发瓶颈,并逐渐下探至5 mD近特低渗油藏有效开发,有力地推进了海上低渗油田开发进程。未来将进一步探索深层-超深层油气领域关键技术,研发大型压裂作业技术装备,打造海上低渗“CO_(2)驱油+封存”联合工程。

一种低渗透油田化学复合驱油体系

随着低渗透油田开发面临的挑战日益增加,采用有效的提油技术以提高采收率和降低开发成本显得尤为重要。通过实验方法评估了氮气泡沫复合驱油体系在不同地层条件下的泡沫稳定性、流变特性以及驱油效率。实验结果表明:泡沫在25℃和101.325 kPa下的半衰期为88.5 min,而在100℃和1013.25 kPa下显著减少至19.9 min,显示出明显的温度和压力依赖性。泡沫的黏度在剪切速率从0.1 s^(-1)增至10 s^(-1)时,从1.58 Pa·s降至0.82 Pa·s,表明其良好的剪切稀化行为。在驱油效率方面,随着注入压力从101.325 kPa增至1 013.25 kPa,驱油效率从45.5%提升至75.8%。此外,泡沫成分的生物降解速率和毒性测试表明其环境友好性,为油田应用提供了理想的选择。

海上低渗砂岩储层酸压可行性及酸液体系研究

采用常规基质酸化作业无法对海上低渗砂岩储层实施整体改造,并且由于部分储层渗透率较低,酸液无法顺利进入地层。因此,以涠洲X低渗砂岩油藏为研究对象,开展了适合海上低渗砂岩储层的酸化压裂可行性分析研究,并优选了相应的酸液体系,评价了酸液体系的综合性能。结果表明:目标油田储层段含有一定量的碳酸盐岩矿物,储层的脆性较好,并且储层段水平主应力差异系数在0.114~0.130之间,具备酸化压裂施工的物质基础,压裂施工可使储层形成复杂的裂缝网络。采用有机酸HCW-1、有机酸盐HCF和高温缓蚀剂HSJL-3为主要处理剂,构建了一套适合海上低渗砂岩储层酸压施工的酸液体系,该酸液体系具有较低的表面张力和腐蚀速率,同时具有较强的铁离子稳定能力和防膨能力。另外,储层段天然岩心采用酸压工作液酸蚀作用后裂缝导流能力大幅度提高,并且岩心表面完整,未出现微粒脱落的现象。研究结果认为目标海上低渗砂岩储层具备酸压施工的条件,可以采取酸压施工对其进行增产改造。

低渗透油田压裂技术研究分析

石油在我国社会经济发展中具有举足轻重的地位。与此同时,随着社会经济的迅速发展,人们对能源的需求量越来越大。随着各类科技的发展,越来越多的新技术被用于开发和利用,所以,对油气田的开发与利用就显得尤为重要。尤其是在对许多油田进行了深入的研究后,发现许多油区属于低渗透油区,而对这些油区所使用的压裂技术效果显著。文章对以低渗透油藏为中心的压裂工艺进行了论述与分析,并就其进展作了较为详尽的介绍,希望能够提供相关参考。

MO-DRILL油基钻井液体系在东海油气田的优化与应用

针对东海油气田目前大位移钻井过程中遇到的井壁失稳、薄弱地层易漏失的问题,对现有的MO-DRILL油基钻井液进行优化改进。通过研发合成不同粒径组成的聚合物封堵剂和纳微米级固壁剂,形成了多层次复合微封堵技术。根据不同的漏失层位、漏失性质、漏失速度,筛选相应的油基钻井液堵漏材料,形成了适合东海地层的油基钻井液堵漏技术。通过对MO-DRILL油基钻井液体系的技术优化,现场应用效果良好,应用井深超过8001 m,打破东海大位移井纪录,对实现油气田偏远储量的有效动用,起到了良好的技术支撑作用。

海上低渗油田CO_(2)驱降混剂的研发与评价

针对海上低渗J油田注CO_(2)难以实现混相驱的问题,通过室内合成柠檬酸异丁酯,采用高温高压界面张力仪和细管实验仪开展了不同降混剂的界面性能及浓度优选评价实验,筛选出适合目标油田的降混剂。实验结果表明:J油田地层压力低于CO_(2)驱油最小混相压力,无法达到混相。室内合成的柠檬酸异丁酯相比乙二醇、石油醚具有更高的安全性,能有效降低最小混相压力至17.5 MPa,可以实现混相,最佳质量分数为0.6%。

海上低渗油田注入伴生气驱油最小混相压力实验

为分析L油田注入伴生气驱油能否实现混相驱,开展了最小混相压力测定实验。采用长细管实验法分别测定了海上低渗L油田W31、W32和W51油组含CO_(2)伴生气驱油的最小混相压力,并通过气相色谱仪分析了长细管末端见气前后产出油气组分变化规律。结果表明:气驱前期(0~0.5PV),注入气未运移至长细管末端,产出流体为原油,不同压力下驱油效率和气油比的变化规律相近;随压力增大,注入气与原油两相相态从非混相到近混相再到混相,气液界面逐渐消失,驱油效率不断增大;在地层压力下,L油田W31和W32油组注入伴生气无法实现混相驱,W51油组注入伴生气可以实现混相驱;伴生气驱油过程中主要萃取原油中的轻烃组分,同时伴生气中CO_(2)和C^(5+)会溶解于原油。