Development Strategies for Achieving High Production with Fewer Wells in Conventional Offshore Heavy Oil Fields in Bohai Bay,China

Development strategy for heavy-oil reservoirs is one of the important research interests in China National Offshore Oil Corp. （CNOOC） that plans a highly effective development for heavy oil fields in multilayered fluvial reservoirs because of their significant influence on marine oil and even on China＇s petroleum production. The characteristics analysis of multilayered fluvial reservoirs in the heavy oil fields in Bohai Bay indicates that large amounts ofoil were trapped in the channel, point bar and channel bar sands. The reserves distribution of 8 oilfields illustrates that the reserves trapped in the main sands, which is 20%-40% of all of the sand bodies, account for 70%-90% of total reserves of the heavy oil fields. The cumulative production from high productivity wells （50% of the total wells） was 75%-90% of the production of the overall oilfield, while only 3%-10% of the total production was from the low productivity wells （30% of the total wells）. And the high productivity wells were drilled in the sands with high reserves abundance. Based on the above information the development strategy was proposed, which includes reserves production planning, selection of well configuration, productivity design, and development modification at different stages.

Geochemical Characterization and Origin of High-Sulfur,Heavy Oils in Jiyang Sub-Basin,East China

High-sulfur,heavy petroleum is widely occurring in the Tertiary lacustrine Jiyang sub-basin, Bohai Bay Basin.They are differentiated into two families based on the bulk properties and biomarker compositions.Family 1 is characterized by high resins（40%-71%）and sulfur（2%-4%）,and low wax （l%-6%）,with n-alkanes removed by biodegradation,whereas family 2 is characterized by extremely abundant sulfur（3%-10%）,and high asphaltenes（7%-31%）and wax（2%-19%）,with no evidence of microbial attack.The oils of family 1 are distributed in the reservoir,lower than 1500 m throughout the sub-basin.Biomarker assemblages,such as low pristane/phytane ratios（1 Pr/Ph）and a high abundance of carotane,gammacerane,and dinosterane,suggest that they are derived from the calcareous mudstones and shales among the stratified,saline Es_4~u unit,in addition to the in situ biodegradation-concentrated sulfur content.However,the oils of family 2 are identified only in the western Zhanhua and eastern Chezhen depressions,with a depth deeper than 1700 m.Physical properties,together with biomarker ratios,including even-numbered n-alkanes,1 Pr/Ph,trace diasteranes,higher C35 homohopanes,and abundant dibenzothiophene series,with1 dibenzothiophene/phenanthrene,indicate an origin from carbonate source rocks.The X-ray diffraction analysis showed that the carbonate source rock is limited in the Es_4~u unit of the Bonan sag,which is different from most other source rocks in the same horizon.It is suggested that the high-sulfur,heavy oils are generated at the early stage of the oil window.Bacterial sulfate reduction might be responsible for the occurrence of sulfur species in the high-sulfur,heavy oils,while heavy biodegradation will enhance sulfur concentrations.

Performance and Modeling of an Up-flow Anaerobic Sludge Blanket(UASB) Reactor for Treating High Salinity Wastewater from Heavy Oil Production

In this study,an up-flow anaerobic sludge blanket(UASB) reactor was applied to treat the high salinity wastewater from heavy oil production process.At a HRT of ≥24 h,the COD removal reached as high as 65.08% at an influent COD ranging from 350mg/L to 640mg/L.An average of 74.33% oil reduction was also achieved in the UASB reactor at an initial oil concentration between 112mg/L and 205mg/L.These results indicated that this heavy oil production related wastewater could be degraded efficiently in the UASB reactor.Granular sludge was formed in this reactor.In addition,two models,built on the back propagation neural network(BPNN) theory and linear regression techniques were developed for the simulation of the UASB system performance in the oily wastewater biodegradation.The average error of COD and oil removal was-0.65% and 0.84%,respectively.The results indicated that the models built on the BPNN theory were wellfitted to the detected data,and were able to simulate and predict the removal of COD and oil by the UASB reactor.

Optimization of the Plugging Agent Dosage for High Temperature Salt Profile Control in Heavy Oil Reservoirs

After steam discharge in heavy oil reservoirs,the distribution of temperature,pressure,and permeability in different wells becomes irregular.Flow channels can easily be produced,which affect the sweep efficiency of the oil displacement.Previous studies have shown that the salting-out plugging method can effectively block these channels in high-temperature reservoirs,improve the suction profile,and increase oil production.In the present study,the optimal dosage of the plugging agent is determined taking into account connection transmissibility and inter-well volumes.Together with the connectivity model,a water flooding simulation model is introduced.Moreover,a non-gradient stochastic disturbance algorithm is used to obtain the optimal plugging agent dosage,which provides the basis for the high-temperature salting-out plugging agent adjustment in the field.

Evaluation of Early High Speed Development of Bottom Water Heavy Oil Reservoir

The bottom water heavy oil reservoir has high natural energy, and the bottom water body multiple of the reservoir is 300 times or even higher. The natural energy of the reservoir can keep the superior condition that the formation energy does not decrease under the condition of large liquid volume and high recovery rate. In view of this reservoir condition, we take C oilfield as an example to carry out the oilfield development effect under the condition of large liquid volume and high-speed production, and analyze the influence of high-speed production and medium low-speed production on recovery rate of similar heavy oil bottom water-reservoir. The results show that the rising trend of water cut in oilfield is the same whether high-speed development with large liquid volume or conventional low-speed development is adopted. Under the condition of high liquid production, the sweep efficiency of water flooding is high in the same period of time, which has certain advantages of enhanced oil recovery. The development mode of early large liquid production is explored, which provides certain guidance for the efficient development of heavy oil reservoir with bottom water.

Biodegraded Oil and Its High Molecular Weight (C_(35+)) n-alkanes in the Qianmiqiao Region in the Bohai Bay Basin, Northern China

With a production of 208.2 m3/d, heavy oil was produced by drill stem test (DST) from three shallow reservoirs in Sand Group Nos. Ⅰ and Ⅲ of the Neogene Guantao Formation (NgⅠ and NgⅢ) and the Eogene Dongying Formation (Ed) in an exploratory well Ban-14-1 within the Qianmiqiao region, Bohai Bay Basin, northern China. Based on the GC and GC-MS data of the NgⅠ and NgⅢ heavy oil samples, all n-alkanes and most isoprenoid hydrocarbons are lost and the GC baseline appears as an evident 'hump', implying a large quantity of unresolved complex mixture (UCM), which typically revealed a result of heavy biodegradation. However, there still is a complete series of C14-C73 n-alkanes in the high-temperature gas chromatograms (HTGC) of the heavy oil, among which, the abundance of C30- n-alkanes are drastically reduced. The C35-C55 high molecular weight (HMW) n-alkanes are at high abundance and show a normal distribution pattern with major peak at C43 and an obvious odd-carbon-number predominance with CPI37-55 and OEP45-49 values of 1.17 and 1.16-1.20, respectively. According to GC-MS analysis, the heavy oil is characterized by dual source inputs of aquatic microbes and terrestrial higher plants. Various steranes and tricyclic terpanes indicate an algal origin, and hopane-type triterpanes, C24 tetracyclic terpane and drimane series show the bacterial contribution. With the odd-carbon-number preference, HMW n-alkanes provide significant information not only on higher plant source input and immaturity, but also on the strong resistibility to biodegradation.

Temperature effect on performance of nanoparticle/surfactant flooding in enhanced heavy oil recovery

Recently,nanoparticles have been used along with surfactants for enhancing oil recovery.Although the recent studies show that oil recovery is enhanced using nanoparticle/surfactant solutions,some effective parameters and mechanisms involved in the oil recovery have not yet been investigated.Therefore,the temperature effect on the stability of nanoparticle/surfactant solutions and ultimate oil recovery has been studied in this work,and the optimal concentrations of both SiO2 nanoparticle and surfactant(sodium dodecyl sulfate)have been determined by the Central Composite Design method.In addition,the simultaneous effects of parameters and their interactions have been investigated.Study of the stability of the injected solutions indicates that the nanoparticle concentration is the most important factor affecting the solution stability.The surfactant makes the solution more stable if used in appropriate concentrations below the CMC.According to the micromodel flooding results,the most effective factor for enhancing oil recovery is temperature compared to the nanoparticle and surfactant concentrations.Therefore,in floodings with higher porous medium temperature,the oil viscosity reduction is considerable,and more oil is recovered.In addition,the surfactant concentration plays a more effective role in reservoirs with higher temperatures.In other words,at a surfactant concentration of 250 ppm,the ultimate oil recovery is improved about 20%with a temperature increase of 20°C.However,when the surfactant concentration is equal to 750 ppm,the temperature increase enhances the ultimate oil recovery by only about 7%.Finally,the nanoparticle and surfactant optimum concentrations determined by Design-Expert software were equal to 46 and 159 ppm,respectively.It is worthy to note that obtained results are validated by the confirmation test.

Diffusion coefficients of natural gas in foamy oil systems under high pressures

The diffusion coefficient of natural gas in foamy oil is one of the key parameters to evaluate the feasibility of gas injection for enhanced oil recovery in foamy oil reservoirs. In this paper, a PVT cell was used to measure diffusion coefficients of natural gas in Venezuela foamy oil at high pressures, and a new method for deter- mining the diffusion coefficient in the foamy oil was de- veloped on the basis of experimental data. The effects of pressure and the types of the liquid phase on the diffusion coefficient of the natural gas were discussed. The results indicate that the diffusion coefficients of natural gas in foamy oil, saturated oil, and dead oil increase linearly with increasing pressure. The diffusion coefficient of natural gas in the foamy oil at 20 MPa was 2.93 times larger than that at 8.65 MPa. The diffusion coefficient of the natural gas in dead oil was 3.02 and 4.02 times than that of the natural gas in saturated oil and foamy oil when the pressure was 20 MPa. However, the gas content of foamy oil was 16.9 times higher than that of dead oil when the dissolution time and pressure were 20 MPa and 35.22 h, respectively.

Air-SAGD technology for super-heavy oil reservoirs

The air oxidation of super-heavy oil at low temperature was studied in laboratory and its influences on oil viscosity, component and steam sweep efficiency before and after air-injection were analyzed. The feasibility, operation mode and air flooding effect at the late stage of steam assisted gravity drainage(SAGD) were investigated by numerical simulation. The experimental results show for vertical-horizontal well pair SAGD test area of Xing VI Formation in Block Du 84 of Liaohe Oilfield, the low temperature oxidation occurred between 150-250 ?C(steam chamber temperature), the oil viscosity increased greatly after low temperature oxidation, consequently, the oil displacement efficiency dropped sharply. Three development methods in the late stage of SAGD were simulated, i.e., steam + air low temperature oxidation, only air low temperature oxidation and only air high temperature oxidation. By comparing production dynamic curves and residual oil distribution etc., high temperature oxidation reduced the heat loss in late stage of SAGD, recovered the residual oil effectively, and prolonged reservoir development time.

Modification of Mesophase Pitch from Petroleum Heavy Oils

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Development Situation and Future Tendency of Liaohe Oil Province

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稠油热采无机硅酸凝胶封窜剂的研究与应用

在稠油油藏热采过程中容易发生蒸汽地下窜流和地表汽窜,严重影响矿区产能,同时造成地面污染。以水玻璃与尿素为交联剂主体,通过与表面活性剂甘油三乙酸酯进行复配,研制了一种新型耐高温封窜剂。通过正交试验确定了最优封窜剂配方:60%水玻璃+4%尿素+0.2%甘油三乙酸酯+水;红外光谱(FTIR)及扫描电镜(SEM)分析发现,该体系中水玻璃通过一段时间的交联,形成单硅酸,后缩聚形成线性多聚硅酸,硅酸分子间相互作用发生缠结,形成的网状结构使得其稳定性较高,结构更稳定,有更好的耐温能力;实验室内填砂管性能评价结果表明,封窜剂段塞注入量为0.2 PV及候凝时间为5 d时,封堵率98.8%、突破压力梯度1.4 MPa/m、残余阻力系数83.32,经过21 PV 260℃的高温蒸汽冲刷后封堵率稳定在94%以上;现场试验结果表明,井F-109日产油从0.9 t增至5.5 t,含水率由89%降至50%,施工244 d,累计增油1122.4 t,F井区地面不再发生蒸汽窜漏,受地面窜漏影响的14口井恢复了正常注汽吞吐生产,累计增油15713.6 t,平均单井日注汽量100 m 3,注汽压力5.5 MPa。综合表明,该封窜剂体系具有良好的高温选择封堵性,对稠油热采高温蒸汽窜流的有效治理提供了理论指导和技术支撑。

稠油多轮次注采固井水泥浆体系评价与优选

在稠油多轮次注采开发过程中,井筒水泥环需承受350℃高温及多轮次温度交变,需要水泥浆体系具有良好的耐高温和抗疲劳能力。开发了4种耐高温水泥浆体系,在350℃高温循环加热的条件下,对4种水泥浆体系进行10轮次的加热,分别测定其抗压强度和弹性模量,并取样进行X射线衍射分析、扫描电镜形貌分析、纳米CT扫描测试。评价了4种水泥浆体系的抗高温循环能力,探讨了其性能变化的机理。试验结果表明,复合加砂水泥和耐高温韧性水泥可满足稠油多轮次注采开发需求,硅酸盐水泥中添加细硅粉和弹塑剂可有效改善其抗高温能力和耐疲劳能力。

傅里叶变换离子回旋共振质谱技术在稠油高低温氧化评价中的应用

为了认识稠油开发过程中低温氧化与高温氧化阶段原油变化规律,利用静态氧化釜开展稠油的高低温氧化实验,借助傅里叶变换离子回旋共振质谱分析技术对高低温氧化前后的原油分子量及O、N、S杂原子化合物特征开展研究,结果表明:原油低温氧化阶段分子量分布特征与原样相似,相对分子量分布范围在200~750,整体呈平缓状单峰型分布,高温氧化阶段分子量分布范围前移,呈明显的前峰单峰型分布;杂原子化合物中的O元素在低温氧化阶段主要以无环的饱和二元酸形式存在,在高温氧化阶段受环化、芳构化及脱甲基作用的影响,伴随着侧链烷基及杂原子基团的断裂和芳构化过程,造成原油中杂原子化合物向着碳数更小、双键当量(double bond equivalents,DBE)值更低的方向演化。该研究探索了温度与原油结构及化学组成之间的关系,对于指导稠油开发现场具有重要意义。

原油中饱和烃化合物在稠油火驱室内实验中的指示作用

稠油油藏开发中,火驱是否实现高温氧化已经成为评价开发效果的难点之一。为了认清火驱后原油性质的微观变化特征,借助室内物理模型开展稠油火驱实验,并采用气相色谱-质谱(GC-MS)技术对火驱前后的原油开展饱和烃方面的研究。研究表明:火驱后由于原油中饱和烃组分含量增加,造成轻重比(ΣnC_(21-)/ΣnC_(22+))变大,而Pr/nC17、Ph/nC18降低,Pr/Ph比值和OEP值基本不变;甾烷系列化合物的分布特征和含量变化是判断火驱高温氧化的良好指标,热稳定性较好的孕甾烷和升孕甾烷含量增加明显,甾烷异构化参数C_(29)(ββ)/(αα+ββ)和C_(29)(20S)/(20S+20R)基本保持不变;萜烷系列的三环萜烷/藿烷比值在火驱后增加了近2倍,反映热演化程度的C_(31)(22S)/(22S+22R)比值变化不大;β-胡萝卜烷与γ-胡萝卜烷是判断火驱高温氧化的良好指标,火驱后胡萝卜烷含量大幅降低。因此,通过原油中饱和烃化合物的变化趋势、分布特征、含量变化可有效进行火驱高温氧化的评判,可为稠油火驱开发高温氧化燃烧状态的识别提供有力支持。

PHT-01/PHC-05组合催化剂在加氢裂化装置的工业应用

在中国石油辽阳石化公司110万t/a加氢裂化装置中,以俄罗斯原油的二次油(减压蜡油和催化柴油的混合油,二者质量比10∶1)为原料,采用中国石油自主开发的PHT-01加氢精制催化剂、PHC-05加氢裂化催化剂及PHT系列加氢保护剂,为最大限度生产重石脑油进行了工业应用,考察了催化剂应用情况、产品性质及其分布。结果表明:催化剂运行中,可同时进行湿法硫化与钝化操作,精制反应器、裂化反应器的平均反应温度分别为367,363℃,比设计值分别低5,15℃,温升比设计值分别低3,4℃;目标产品重石脑油的含硫(氮)量均小于0.5μg/g、溴指数0.755 mg/g、芳潜质量分数47.3%、初馏点73℃、收率51.56%,精制油含氮量为7~9μg/g,主要产品收率为94.04%,满足下游重整装置进料要求。

海上超稠油高温脱水技术研究

某海上超稠油富含胶质和沥青质,原油密度大、黏度高、油水密度差小、原油流动性差,并且油水乳化严重,导致热化学沉降脱水速度慢、脱水周期长。因海上平台空间受限和缺少稀油资源,该超稠油脱水不能采用陆上油田掺混稀油和长时间大罐沉降脱水的常规方法。开展了超稠油高温脱水技术研究,优选出耐高温破乳剂,破乳剂加剂量400 mg/L,在150℃高温、0.6~0.7 MPa压力下沉降4 h,含水15%~65%超稠油的原油含水率均达到<1%,实现了较好的脱水效果。根据室内脱水实验结果,获得海上超稠油高温脱水工艺参数,确定最佳破乳剂加药量、脱水温度和沉降时间,推荐了海上超稠油二段热化学脱水工艺方案。

塔河油田稠油井生产测井技术应用效果评价

通过对比塔河油田不同稠油井测量产液剖面时的稀稠比、测量时机、仪器组合,分析成败原因,最终总结出一套适合稠油井的生产测井施工优化方案,并在两口井的施工中实施,均取得合格生产测井数据。

重质油高温快速热解自动反应网络的动力学建模

重质油高温快速热解过程模型对提高产品收率、附加值及降低能耗具有重要意义。利用自动反应网络生成器RMG(reaction mechanism generator)构建重质油高温快速热解的机理模型。选择了分步构建方法,最终合并的模型包含230种物质和1468个反应。采用高频炉对二十烷、十氢萘、乙苯和不同质量比例混合物(二十烷、乙苯和十氢萘)进行快速热解实验验证,结果表明:机理模型可准确模拟出重质油高温快速热解主要气体产物生成结果,当重质油中链烷烃含量较多时和芳烃含量较多时,分别控制温度在1300℃左右和800℃左右有利于乙烯的生产。

稠油开采水泥改性材料研究进展

近些年来在稠油开采水泥改性材料的研究中有一些新的进展,主要的研究方法是在油井水泥中添加二氧化硅材料和纤维,同时发现200目(0.074mm)的硅粉适用性广,掺量35%左右的硅粉在油井水泥施工是较为合适的。由于微硅和纳米二氧化硅具有大比表面积和小粒径,具有一些特殊性能。水泥石可以加入单一纤维或者混杂纤维,都能有效提高水泥石的强度。缓凝剂的加入,有效缓解了高温下水泥快速水化的问题。除此之外,还有一些学者研究了非常规水泥改性材料。