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.

Progress and development directions of stimulation techniques for ultra-deep oil and gas reservoirs

By reviewing the development history of stimulation techniques for deep/ultra-deep oil and gas reservoirs,the new progress in this field in China and abroad has been summed up,including deeper understanding on formation mechanisms of fracture network in deep/ultra-deep oil and gas reservoir,performance improvement of fracturing fluid materials,fine stratification of ultra-deep vertical wells,and mature staged multi-cluster fracturing technique for ultra-deep and highly deviated wells/horizontal wells.In light of the exploration and development trend of ultra-deep oil and gas reservoirs in China,the requirements and technical difficulties in ultra-deep oil and gas reservoir stimulation are discussed:(1)The research and application of integrated geological engineering technology is difficult.(2)The requirements on fracturing materials for stimulation are high.(3)It is difficult to further improve the production in vertical profile of the ultra-deep and hugely thick reservoirs.(4)The requirements on tools and supporting high-pressure equipment on the ground for stimulation are high.(5)It is difficult to achieve efficient stimulation of ultra-deep,high-temperature and high-pressure wells.(6)It is difficult to monitor directly the reservoir stimulation and evaluate the stimulation effect accurately after stimulation.In line with the complex geological characteristics of ultra-deep oil and gas reservoirs in China,seven technical development directions are proposed:(1)To establish systematic new techniques for basic research and evaluation experiments;(2)to strengthen geological research and improve the operational mechanism of integrating geological research and engineering operation;(3)to develop high-efficiency fracturing materials for ultra-deep reservoirs;(4)to research separated layer fracturing technology for ultra-deep and hugely thick reservoirs;(5)to explore fracture-control stimulation technology for ultra-deep horizontal well;(6)to develop direct monitoring technology for hydraulic fractures in ultra-deep oil and gas reservoirs;(7)to develop downhole fracturing tools with high temperature and high pressure tolerance and supporting wellhead equipment able to withstand high pressure.

Origin of abnormal high pressure and its relationship with hydrocarbon accumulation in the Dina 2 Gas Field, Kuqa Depression

Based on distribution of formation pressure by indirect estimation and formation testing,this study investigates origin of abnormal high pressure in the Dina 2 Gas Field in the Kuqa Depression in combination with the latest research findings.Contribution of major overpressure mechanisms to this gas field is estimated,and generation of the abnormal high pressure as well as its relationship with natural gas accumulation is explored.Disequilibrium compaction,tectonic stress,and overpressure transfer are the major overpressure mechanisms.Overpressure transfer resulted from vertical opening of faults and folding is the most important cause for the overpressure.Gas accumulation and abnormal high pressure generation in the reservoirs of the Dina 2 Gas Field show synchroneity.During the early oil-gas charge in the Kangcun stage,the reservoirs were generally normal pressure systems.In the Kuqa deposition stage,rapid deposition caused disequilibrium compaction and led to generation of excess pressure(approximately 5-10 MPa)in the reservoirs.During the Kuqa Formation denudation stage to the Quaternary,reservoir overpressure was greatly increased to approximately 40-50 MPa as a result of vertical pressure transfer by episodic fault activation,lateral overpressure transfer by folding and horizontal tectonic stress due to intense tectonic compression.The last stage was the major period of ultra-high pressure generation and gas accumulation in the Dina 2 Gas Field.

Prediction of wax precipitation region in wellbore during deep water oil well testing

During deep water oil well testing, the low temperature environment is easy to cause wax precipitation, which affects the normal operation of the test and increases operating costs and risks. Therefore, a numerical method for predicting the wax precipitation region in oil strings was proposed based on the temperature and pressure fields of deep water test string and the wax precipitation calculation model. And the factors affecting the wax precipitation region were analyzed. The results show that: the wax precipitation region decreases with the increase of production rate, and increases with the decrease of geothermal gradient, increase of water depth and drop of water-cut of produced fluid, and increases slightly with the increase of formation pressure. Due to the effect of temperature and pressure fields, wax precipitation region is large in test strings at the beginning of well production. Wax precipitation region gradually increases with the increase of shut-in time. These conclusions can guide wax prevention during the testing of deep water oil well, to ensure the success of the test.

苏北页岩油二氧化碳强压质换技术

为了保持苏北页岩油藏能量,降低产量递减率,提高页岩油藏采收率,研究了苏北页岩油CO_(2)强压质换技术。采用苏北页岩油藏岩心进行了室内试验,分析了CO_(2)注入压力、焖井时间对原油采出程度的影响,CO_(2)注入量对原油采收率的影响;采用数值模拟软件,进行了SD1J井注入时机、注入量、注入速度及焖井时间的优化,并进行了SD1J井注超大量CO_(2)强压质换技术现场试验。SD1J井措施后自喷正常生产,产液量由38.6 t/d降至30.3 t/d,产油量由14.0 t/d升至29.2 t/d,含水率由63.8%降至3.5%。研究表明,CO_(2)强压质换技术能够提高页岩油藏地层能量和降低产量递减率,为提高页岩油藏开发效果提供了一种新的技术途径。

黏温黏压下径向柱塞泵滑靴副温度分布与泄漏量分析

针对高压大排量径向柱塞泵滑靴副摩擦失效和泄漏问题,以XDP1000型径向柱塞泵为例,对滑靴副温度分布与泄漏量进行了流场仿真和数值计算。首先,根据滑靴柱塞组件运动学特性分析,求解了滑靴偏转角变化规律,并通过建立滑靴副不同通道流量计算公式的方式,建立了滑靴副静压支承特性方程;然后,建立了滑靴副泄漏功率损失和摩擦功率损失模型,求解了滑靴副最佳油膜厚度,并分析了最佳油膜厚度的变化规律;最后,在考虑了油液黏温黏压特性的基础上,通过流场数值计算的方式,研究了滑靴副温度分布与泄漏量随径向柱塞泵工况参数的变化规律。研究结果表明:额定工况下,滑靴副最佳油膜厚度值约为14μm,滑靴副最佳油膜厚度值随着转子转角的增大而增大,随着工作压力和温度的增大而减小;滑靴运动方向侧油膜温度较另一侧高13 K,滑靴副温度值基本不受工作压力的影响,而随着转速的增大而升高;滑靴副阻尼孔泄漏量较滑靴边界泄漏量大0.02 kg/s,而且泄漏量随着压力、转速和油液温度的增大而增大。该研究结论可为高压大排量径向柱塞泵滑靴副设计及优化提供参考。

海上油气田特色射孔工艺技术及应用

介绍了海上油气田勘探开发过程中,针对不同油气藏和完井工艺形成的特色海上油气田射孔工艺技术及应用,包括针对大斜度井水平井的MWD/LWD-TCP(随钻测量和油管传输射孔)联作射孔技术,针对电潜泵完井的ESP-TCP(电潜泵和油管传输射孔)联作射孔技术,针对疏松砂岩砾石充填完井的超高孔密大孔径射孔技术以及高温高压碱性完井液条件下的射孔技术等。通过MWD/LWD与TCP技术的深度融合,实现了高精度定位和自动化控制,提高了射孔作业的智能化水平。特色射孔技术的应用显著提高了海上油气田勘探开发的作业效率,缩短了工期。通过技术创新和工艺改进,降低了射孔作业的风险,保障了作业安全。

井下电控水泥释放工具研制与试验

针对国内外传统油气井释放水泥工具所存在的弊端,基于井下电动工具的设计原理,创新性地研制出了一套新型井下电控水泥释放工具。详细介绍了该工具的结构组成和工作原理,重点对工具动作部件进行了力学分析,探究了井斜、温度、压力及井液性质对工具开启的影响,所研制的井下电控水泥释放工具外径为73 mm,长度为1 400 mm,可根据不同施工井况,通过变扣灵活配备不同规格的储灰筒。高压地面试验和现场施工试验分别验证了工具耐高温高压性能以及倒灰作业施工的可行性。可为油气井封堵作业的安全施工提供更高效可行的技术支撑。

超高温高压完井组块密封的研制

组块密封作为完井工程中的保持井筒完整性、实现井下资源分层开采的重要工具,其工作的可靠性与稳定性不言而喻。在超高温高压油气田中,对于组块密封的耐温性、耐压性要求更高,该方面研究在国内少有涉及。本文通过新型耐高温气密材料的开发、组块密封结构设计,结合结构仿真与试验,研制形成多个尺寸系列耐温204℃、耐压10000 psi的完井组块密封工具,为我国超高温高压油气田开发提供了国产化工具支持。

富含凝析油型凝析气藏衰竭开发采收率研究

目前,标准的PVT筒中的凝析气定容衰竭实验都是在空筒内完成的,没有考虑多孔介质的影响,这与实际情况相差甚远。文章采用富合凝析油型真实凝析气体系分别在PVT筒和长岩心中进行衰竭实验,表明多孔介质中凝析油采收率比PVT中高约1倍,天然气采收率和PVT筒中测试相比差别不大。此外,还开展了真实凝析油气相渗曲线和常规油气相渗曲线测试,发现二者差别很大,经过进一步的分析,表明造成凝析油采收率差别的主要原因是凝析油气相渗曲线的差别。研究还发现凝析气藏凝析油采收率有速度敏感性,衰竭速度快有利于提高凝析油采收率;常规PVT筒测试的凝析油采收率不能用于开发评价,在开发方案及动态分析数值模拟中,使用平衡凝析油气相渗曲线对多孔介质中凝析油采收率预测更为可靠。

高压脉冲—超临界萃取法提取荔枝种仁精油

对高压脉冲电场一超临界CO2萃取荔枝种仁精油及其影响因素进行研究，结果表明：种子含水量是影响精油萃取效率的主要因素。两者呈“S”型衰减指数关系。精油萃取率与萃取压力、萃取时间呈对数函数关系。在临界压力下，温度过高会因密度下降而使单位体积的萃取携带效率降低。

致密油储层微观孔隙结构定量表征——以鄂尔多斯盆地新安边油田长7储层为例

鄂尔多斯盆地新安边油田长7致密油储层具有较好的开发潜力,由于微观孔隙结构研究的薄弱制约了致密油勘探开发进程,对后期开采具有较大影响。该文采用扫描电镜、铸体薄片、高压压汞、微纳米CT扫描等技术,对新安边油田长7致密油储层的储集空间特征及微观孔隙结构参数进行定量表征。结果表明,长7致密油储层孔隙类型主要分为三类:粒间孔、溶孔、微裂缝。研究区发育大量纳米级孔喉,其对储层的储集及渗流能力具有较大贡献。依据不同样品的排驱压力划分:排驱压力小于1 MPa时,微米尺度孔隙丰富且连通性好,孔喉形态多为粗大管状、条带状,喉道半径主要集中在100~380 nm;排驱压力介于1~3 MPa之间,局部孔隙连通性好,纳米尺度孔喉多发育于粒内溶孔,孔喉形态表现为管束状、球状,喉道半径主要分布于75~250 nm;排驱压力大于3 MPa时,大量孤立的小球状孔喉聚集,垂向连通性差,仅局部微裂缝发育区提供储集空间,喉道半径主要集中为15~75 nm。

苏里格气田优质储层的控制因素

苏里格气田优质储层具有埋藏深度大、深埋时间长、成岩演化阶段高、物性好的特点。该套储层的分布主要受沉积环境、石英含量、颗粒粒度、埋藏史、成岩作用、裂缝发育程度、异常高压等因素的控制。其中分流河道为最有利的微相 ;石英含量大于 90 %、特别是大于 95 %时 ,孔渗明显变好 ;孔隙度大于 8%、渗透率大于 0 .5×10 -3 μm2 的样品通常分布于粒度中值在 0 .5 0mm以上的粗砂岩中 ;裂缝对储层物性有较大的改善 ;异常高压对优质储层的发育具有一定的保护作用 ,应特别加强对裂缝的研究。

高温高压下碳酸钙的溶解度及朝阳沟注水油田低渗透储层结垢问题

大庆朝阳沟低渗透水驱油田一些注水井注水压力不断上升,采油井井底结垢,垢样含63.4%CaCO3、22.0%Fe2O3、14.6%有机物及其他。讨论了生成CaCO3垢的基本化学反应。实验测定并发表了温度分别为25、50、75、90℃±0.1℃,压力分别为0.1、9、19、29MPa(测量误差±5%,0.1MPa时除外)时,CaCO3在蒸馏水中的溶解度数据(单位mg/L)。概括性地讨论了相同离子和盐对CaCO3溶解度的影响。基于测得的溶解度数据及注入水、地层水矿化离子种类和含量,认为在朝阳沟油田,注水井井底温度25℃、压力约19MPa(注水压力9MPa),只要严格控制注入水的离子种类和含量,一般不会产生CaCO3结垢;采油井井底温度约45℃,压力≤0.2MPa,易产生CaCO3结垢。图2表1参2。

歧北深层高温高压条件下烃源岩特殊的成烃演化规律

黄骅坳陷歧北地区深层高温高压条件下古近系烃源岩成烃演化规律与传统的干酪根降解演化规律存在差异 ,其差异突出体现在成熟度参数的演化特征上。在分析歧北深层烃源岩特殊的成熟演化特征及不同温压条件下热压模拟演化特征的基础上 ,探讨超压在深层烃源岩成烃演化过程中的作用 ,总结高温高压条件下深层烃源岩特殊的成烃演化规律。指出 :虽然超压影响油气生成演化的全过程 ,但在不同演化阶段超压的影响是不同的。超压的滞烃效应主要作用于烃类进入生烃高峰的后期 ,超压不仅可抑制液态烃向气态烃的转化 ,而且还抑制干酪根的降解 ,使油气生成的时限延迟 ,以致在正常条件下预测生气的深度仍将继续生油。歧北地区深层高温高压条件下古近系烃源岩特殊的成烃演化规律主要体现在成熟油相窗口向高成熟早期的推移。图 4表 1参

激光测试高温高压凝析油析蜡温度及其应用

针对柯深 10 1井异常高温高压含蜡凝析气井出现石蜡堵塞现象 ,开展了室内实验和现场评价的研究。文章利用自行开发的固溶物沉积激光测试系统 ,测试了凝析气平衡油在不同压力下的析蜡温度。结果表明 ,凝析气平衡油液—固两相析蜡温度随压力下降而升高 ,压力越低析蜡温度上升越快 ,而且平衡油的析蜡规律与脱气油相反 ;该井凝析气中平衡油在压力 6 0 .0 0～ 0 .10MPa的析蜡温度为 2 7.7～ 38℃。研究得到的气—液—固三相相图表明 ,当温度低于液—固两相析蜡温度后 ,预测的气—液两相等液量线开始偏离正常 ,并快速上翘。利用析蜡实验数据预测出了析蜡位置 ,使得任何时候地层中都不会析蜡 ;在生产测试时 ,井筒中的蜡在距井口 4 6 5m油管以上析出 ,预测结果与现场试验吻合。提高产量或加热、保温等措施 ,使井口流温高于 38℃ ,井筒中不会析蜡 ;将分离器及其上游管线温度从 32℃提高到 36℃以上 ,可以防止凝析油在地面流动中析蜡。

聚乙烯复合管在油田苛刻环境的适用性

使用高温高压釜模拟塔河油田塑料复合管苛刻的工况条件,研究了聚乙烯和交联聚乙烯两种复合管在三种介质模拟工况条件下不同试验时间后的外观形貌、质量、拉伸强度、耐热性能和化学结构的变化规律。结果表明,气体、煤油、NaCl溶液三种介质对这两种复合管的性能均会产生不利的影响。在三种介质模拟工况条件下,随时间的增加两种复合管的质量增加、拉伸强度和维卡软化温度(VST)降低,拉伸强度和VST的变化主要发生在前10 h;在煤油介质中两种复合管的质量增加最显著,同时VST降低幅度最大;模拟工况试验1?000 h后,两种复合管在所有介质中的拉伸强度均下降,交联聚乙烯管的拉伸强度保持率略优于聚乙烯管,在气体和NaCl溶液中交联聚乙烯管的VST略高于聚乙烯管,在煤油介质中交联聚乙烯管的VST仅为64℃,聚乙烯管的VST为67℃。

高温高压水洗物性变化实验研究——以塔里木轮南油田T_Ⅰ油组为例

塔里木轮南油田TⅠ油组已有20年注水开发历史,近年对油藏开发过程中的水洗动用状况进行了一些研究,但所采用的实验手段均未在地层条件下进行。该文利用取自该油田的流体和岩心,进行高温高压下的水洗模拟实验,以弄清储层条件下油水渗流规律,研究储层长期水洗后微观孔隙结构、润湿性等变化特征。实验表明:水洗过后,岩心孔渗降低幅度随水洗倍数增加而略有增大,分选性变差;水湿性随水洗倍数增大而增强;相渗曲线的Swi与Sor均增大,Krw(Sor)降低,驱油效率降低;水洗后未形成大孔道,造成水提前突破的主要原因可能是TI层内存在平面与纵向非均质性。

挥发油油藏生产特征及影响采收率的因素

通过对中原油田某挥发油藏生产特征的研究，分析了该油藏弹性能量、溶解气能量，以及目前开采该油藏所存在的问题。指出该油藏的开采特征不同于黑油油藏，进而讨论了开发该油藏的合理开采方式及转注时机，并针对目前油藏注水困难这一问题进行了分析和研究，指出了油藏注水时应注意的问题。目的在于为开发同类油藏提出一些合理的建议。

港深78井裂缝发育影响因素、成因及其在油气勘探中的意义

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